31,394 research outputs found
Global Dimension of Polynomial Rings in Partially Commuting Variables
For any free partially commutative monoid , we compute the global
dimension of the category of -objects in an Abelian category with exact
coproducts. As a corollary, we generalize Hilbert's Syzygy Theorem to
polynomial rings in partially commuting variables.Comment: 11 pages, 2 figure
Study of zero-gravity, vapor/liquid separators
Heat exchange, mechanical separation, surface tension, and dielectrophoretic methods of separating vapor from liquid at zero gravity for vapor ventin
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A mechanism model of the effect of hedonic product consumption on well-being
In response to recent calls for research into activities that may increase happiness, this study uses longitudinal data to investigate changes in within-subject, instead of between-subject, well-being. In the context of hedonic product consumption, this study reveals a mechanism by which consumption influences well-being through the mediating effect of satisfaction with associated life domains. Four years of data from a large national panel survey show that consuming hedonic products has indirect effects on well-being, by improving consumers' satisfaction within relevant life domains. High hedonic consumption improves satisfaction with relevant life domains, primarily through more frequent consumption of low-cost hedonic products rather than less frequent consumption of high-cost hedonic products
Invariant manifolds and the geometry of front propagation in fluid flows
Recent theoretical and experimental work has demonstrated the existence of
one-sided, invariant barriers to the propagation of reaction-diffusion fronts
in quasi-two-dimensional periodically-driven fluid flows. These barriers were
called burning invariant manifolds (BIMs). We provide a detailed theoretical
analysis of BIMs, providing criteria for their existence, a classification of
their stability, a formalization of their barrier property, and mechanisms by
which the barriers can be circumvented. This analysis assumes the sharp front
limit and negligible feedback of the front on the fluid velocity. A
low-dimensional dynamical systems analysis provides the core of our results.Comment: 14 pages, 11 figures. To appear in Chaos Focus Issue:
Chemo-Hydrodynamic Patterns and Instabilities (2012
Personal branding for academic faculty: a new social phenomenon for Russian higher education?
The paper reports the results of a pilot study on the extent to which academic faculty at Rus-sian higher education institutions engage in personal branding. The paper places personal branding in the context of an increased reliance on social media by Russian higher educa-tion institutions and examines the question of whether personal branding might be conducive to academic faculty’s career advancement. Employing analysis of publicly available data, the authors demonstrate that leading Russian universities use social media to raise their pro-file. Analysis of the Facebook, Instagram and vk social media accounts of academic faculty at a prominent Russian university demonstrated that almost a third of academic faculty en-gaged in personal branding to some extent, and almost 7% engaged in strategic personal branding. This was limited, however, to senior faculty members and it is unclear whether their strategic personal branding impacts on their career advancement or is merely reflec-tive of it. It remains to be seen whether this trend will ‘trickle down’ and become more prev-alent among Russian academic faculty
100 MHz Amplitude and Polarization Modulated Optical Source for Free-Space Quantum Key Distribution at 850 nm
We report on an integrated photonic transmitter of up to 100 MHz repetition
rate, which emits pulses centered at 850 nm with arbitrary amplitude and
polarization. The source is suitable for free space quantum key distribution
applications. The whole transmitter, with the optical and electronic components
integrated, has reduced size and power consumption. In addition, the
optoelectronic components forming the transmitter can be space-qualified,
making it suitable for satellite and future space missions.Comment: 6 figures, 2 table
Instability of toroidal magnetic field in jets and plerions
Jets and pulsar-fed supernova remnants (plerions) tend to develop highly
organized toroidal magnetic field. Such a field structure could explain the
polarization properties of some jets, and contribute to their lateral
confinement. A toroidal field geometry is also central to models for the Crab
Nebula - the archetypal plerion - and leads to the deduction that the Crab
pulsar's wind must have a weak magnetic field. Yet this `Z-pinch' field
configuration is well known to be locally unstable, even when the magnetic
field is weak and/or boundary conditions slow or suppress global modes. Thus,
the magnetic field structures imputed to the interiors of jets and plerions are
unlikely to persist.
To demonstrate this, I present a local analysis of Z-pinch instabilities for
relativistic fluids in the ideal MHD limit. Kink instabilities dominate,
destroying the concentric field structure and probably driving the system
toward a more chaotic state in which the mean field strength is independent of
radius (and in which resistive dissipation of the field may be enhanced). I
estimate the timescales over which the field structure is likely to be
rearranged and relate these to distances along relativistic jets and radii from
the central pulsar in a plerion.
I conclude that a concentric toroidal field is unlikely to exist well outside
the Crab pulsar's wind termination shock. There is thus no dynamical reason to
conclude that the magnetic energy flux carried by the pulsar wind is much
weaker than the kinetic energy flux. Abandoning this inference would resolve a
long-standing puzzle in pulsar wind theory.Comment: 28 pages, plain TeX. Accepted for publication in Ap
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