35,202 research outputs found
Two phase aqueous extraction of whey proteins in a polyethylene glycol - arabinogalactan system
The whey protein separation potential of aqueous two-phase systems of arabinogalactan [AG] (Lonza FiberAidTM) and polyethylene glycol [PEG], buffered with 10 mmol/g phosphate or citrate buffer, was studied. 100 mmol/g potassium chloride [KCl] was added as required. Previously-published phase equilibrium results were verified and the absorbance of whey protein isolate [WPI] in an AG-PEG solution was measured. The effect of pH, KCl concentration, initial WPI concentrations and upper to lower phase mass ratios on whey partitioning was studied. The best separation system contained 17.20% (w/w) AG, 7.20% (w/w) PEG, 10 mmol citrate buffer (pH 5.4) and 100 mmol KCl per gram of total system. The upper to lower phase mass and volume ratios were 1:1 and 16:11 respectively. Approximately 12 mg (mainly α-lactalbumin) of the 20 mg WPI added partitioned into the AG-rich upper phase. This system has potential to reduce chromatographic requirements in large scale separation of protein mixtures
Electrostatic Structures in Space Plasmas: Stability of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes
Electrostatic structures have been observed in many regions of space plasmas,
including the solar wind, the magnetosphere, the auroral acceleration region,
and in association with shocks, turbulence, and magnetic reconnection. Due to
potentially large amplitude of electric fields within these structures, their
effects on particle heating, scattering, or acceleration can be important. One
possible theoretical description of some of these structures is the concept of
Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear solutions of
the Vlasov-Poisson system of equations in collisionless kinetic theory. BGK
modes have been studied extensively for many decades, predominately in one
dimension (1D), although there have been observations showing that some of
these structures have clear 3D features. While there have been approximate
solutions of higher dimensional BGK modes, an exact 3D BGK mode solution in a
finite magnetic field has not been found yet. Recently we have constructed
exact solutions of 2D BGK modes in a magnetized plasma with finite magnetic
field strength in order to gain insights of the ultimate 3D theory [Ng,
Bhattacharjee, and Skiff, Phys. Plasmas 13, 055903 (2006)]. Based on the
analytic form of these solutions, as well as Particle-in-Cell (PIC)
simulations, we will present numerical studies of their stability for different
levels of background magnetic field strength.Comment: Submitted to AIP Journal Proceedings for "Tenth Annual International
Astrophysics Conference
An integer programming Model for the Hospitals/Residents Problem with Couples
The Hospitals/Residents problem with Couples (hrc) is a generalisation of the classical Hospitals/Residents problem (hr) that is important in practical applications because it models the case where couples submit joint preference lists over pairs of (typically geographically close) hospitals. In this paper we give a new NP-completeness result for the problem of deciding whether a stable matching exists, in highly restricted instances of hrc. Further, we present an Integer Programming (IP) model for hrc and extend it the case where preference lists can include ties. Further, we describe an empirical study of an IP model for HRC and its extension to the case where preference lists can include ties. This model was applied to randomly generated instances and also real-world instances arising from previous matching runs of the Scottish Foundation Allocation Scheme, used to allocate junior doctors to hospitals in Scotland
Idealized Slab Plasma approach for the study of Warm Dense Matter
Recently, warm dense matter (WDM) has emerged as an interdisciplinary field
that draws increasing interest in plasma physics, condensed matter physics,
high pressure science, astrophysics, inertial confinement fusion, as well as
materials science under extreme conditions. To allow the study of well-defined
WDM states, we have introduced the concept of idealized-slab plasmas that can
be realized in the laboratory via (i) the isochoric heating of a solid and (ii)
the propagation of a shock wave in a solid. The application of this concept
provides new means for probing the dynamic conductivity, equation of state,
ionization and opacity. These approaches are presented here using results
derived from first-principles (density-functional type) theory, Thomas-Fermi
type theory, and numerical simulations.Comment: 37 pages, 21 figures, available, pdf file only. To appear in: Laser
and Particle beams. To appear more or less in this form in Laser and Particle
beam
Information and Particle Physics
Information measures for relativistic quantum spinors are constructed to
satisfy various postulated properties such as normalisation invariance and
positivity. Those measures are then used to motivate generalised Lagrangians
meant to probe shorter distance physics within the maximum uncertainty
framework. The modified evolution equations that follow are necessarily
nonlinear and simultaneously violate Lorentz invariance, supporting previous
heuristic arguments linking quantum nonlinearity with Lorentz violation. The
nonlinear equations also break discrete symmetries. We discuss the implications
of our results for physics in the neutrino sector and cosmology
7Li and 19F NMR study of LiCF3SO3 containing polymer electrolytes : the effect of plasticizers
Characterisation of re-entrant circuit (or rotational activity) in vitro using the HL1-6 myocyte cell line
Fibrillation is the most common arrhythmia observed in clinical practice. Understanding of the mechanisms underlying its initiation and maintenance remains incomplete. Functional re-entries are potential drivers of the arrhythmia. Two main concepts are still debated, the “leading circle” and the “spiral wave or rotor” theories. The homogeneous subclone of the HL1 atrial-derived cardiomyocyte cell line, HL1-6, spontaneously exhibits re-entry on a microscopic scale due to its slow conduction velocity and the presence of triggers, making it possible to examine re-entry at the cellular level. We therefore investigated the re-entry cores in cell monolayers through the use of fluorescence optical mapping at high spatiotemporal resolution in order to obtain insights into the mechanisms of re-entry. Re-entries in HL1-6 myocytes required at least two triggers and a minimum colony area to initiate (3.5 to 6.4 mm2). After electrical activity was completely stopped and re-started by varying the extracellular K+ concentration, re-entries never returned to the same location while 35% of triggers re-appeared at the same position. A conduction delay algorithm also allows visualisation of the core of the re-entries. This work has revealed that the core of re-entries is conduction blocks constituted by lines and/or groups of cells rather than the round area assumed by the other concepts of functional re-entry. This highlights the importance of experimentation at the microscopic level in the study of re-entry mechanisms
Rings and Jets around PSR J2021+3651: the `Dragonfly Nebula'
We describe recent Chandra ACIS observations of the Vela-like pulsar PSR
J2021+3651 and its pulsar wind nebula (PWN). This `Dragonfly Nebula' displays
an axisymmetric morphology, with bright inner jets, a double-ridged inner
nebula, and a ~30" polar jet. The PWN is embedded in faint diffuse emission: a
bow shock-like structure with standoff ~1' brackets the pulsar to the east and
emission trails off westward for 3-4'. Thermal (kT=0.16 +/-0.02 keV) and power
law emission are detected from the pulsar. The nebular X-rays show spectral
steepening from Gamma=1.5 in the equatorial torus to Gamma=1.9 in the outer
nebula, suggesting synchrotron burn-off. A fit to the `Dragonfly' structure
suggests a large (86 +/-1 degree) inclination with a double equatorial torus.
Vela is currently the only other PWN showing such double structure. The >12 kpc
distance implied by the pulsar dispersion measure is not supported by the X-ray
data; spectral, scale and efficiency arguments suggest a more modest 3-4 kpc.Comment: 22 pages, 5 figures, 3 tables, Accepted to Ap
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