377,673 research outputs found
Studying Membrane Biogenesis with a Luciferase-Based Reporter Gene Assay
To study the coordination of different lipid synthesis pathways during membrane biogenesis it is useful to work with an experimental system where membrane biogenesis occurs rapidly and in an inducible manner. We have found that phagocytosis of latex beads is practical for these purposes as cells rapidly synthesize membrane lipids to replenish membrane pools lost as wrapping material during particle engulfment. Here, we describe procedures for studying changes in phagocytosis-induced gene expression with a luciferase-based reporter gene approach using the Dual-Glo Luciferase Assay System from Promega
An optimal synchronous bandwidth allocation scheme for guaranteeing synchronous message deadlines with the timed-token MAC protocol
This paper investigates the inherent timing properties of the timed-token medium access control (MAC) protocol necessary to guarantee synchronous message deadlines in a timed token ring network such as, fiber distributed data interface (FDDI), where the timed-token MAC protocol is employed. As a result, an exact upper bound, tighter than previously published, on the elapse time between any number of successive token arrivals at a particular node has been derived. Based on the exact protocol timing property, an optimal synchronous bandwidth allocation (SBA) scheme named enhanced MCA (EMCA) for guaranteeing synchronous messages with deadlines equal to periods in length is proposed. Thm scheme is an enhancement on the previously publiibed MCA scheme
Holonomic Quantum Computing Based on the Stark Effect
We propose a spin manipulation technique based entirely on electric fields
applied to acceptor states in -type semiconductors with spin-orbit coupling.
While interesting in its own right, the technique can also be used to implement
fault-resilient holonomic quantum computing. We explicitly compute adiabatic
transformation matrix (holonomy) of the degenerate states and comment on the
feasibility of the scheme as an experimental technique.Comment: 5 page
Cycle-time properties of the timed token medium access control protocol
We investigate the timing properties of the timed token protocol that are necessary to guarantee synchronous message deadlines. A tighter upper bound on the elapse time between the token's lth arrival at any node i and its (l + v)th arrival at any node k is found. A formal proof to this generalized bound is presented
Evidence for a new resonance with in the old data of reaction
Distinctive patterns are predicted by quenched quark models and unquenched
quark models for the lowest SU(3) baryon nonet with spin parity .
While the quenched quark models predict the lowest resonance
to be above 1600 MeV, the unquenched quark models predict it to be around
energy. Here we re-examine some old data of the \kp \to \la
reaction and find that besides the well established with
, there is indeed some evidence for the possible existence of a new
resonance with around the same mass but with broader
decay width. Higher statistic data on relevant reactions are needed to clarify
the situation.Comment: 7 pages, 4 figure
Experiment and theoretical study of the propagation of high power microwave pulse in air breakdown environment
In the study of the propagation of high power microwave pulse, one of the main concerns is how to minimize the energy loss of the pulse before reaching the destination. In the very high power region, one has to prevent the cutoff reflection caused by the excessive ionization in the background air. A frequency auto-conversion process which can lead to reflectionless propagation of powerful EM pulses in self-generated plasmas is studied. The theory shows that under the proper conditions the carrier frequency, omega, of the pulse will indeed shift upward with the growth of plasma frequency, omega(sub pe). Thus, the plasma during breakdown will always remain transparent to the pulse (i.e., omega greater than omega(sub pe)). A chamber experiment to demonstrate the frequency auto-conversion during the pulse propagation through the self-generated plasma is then conducted in a chamber. The detected frequency shift is compared with the theoretical result calculated y using the measured electron density distribution along the propagation path of the pulse. Good agreement between the theory and the experiment results is obtained
Accelerating Universe from Extra Spatial Dimension
We present a simple higher dimensional FRW type of model where the
acceleration is apparently caused by the presence of the extra dimensions.
Assuming an ansatz in the form of the deceleration parameter we get a class of
solutions some of which shows the desirable feature of dimensional reduction as
well as reasonably good physical properties of matter. Interestingly we do not
have to invoke an extraneous scalar field or a cosmological constant to account
for this acceleration. One argues that the terms containing the higher
dimensional metric coefficients produces an extra negative pressure that
apparently drives the inflation of the 4D space with an accelerating phase. It
is further found that in line with the physical requirements our model admits
of a decelerating phase in the early era along with an accelerating phase at
present.Further the models asymptotically mimic a steady state type of universe
although it starts from a big type of singularity. Correspondence to Wesson's
induced matter theory is also briefly discussed and in line with it it is
argued that the terms containing the higher dimensional metric coefficients
apparently creates a negative pressure which drives the inflation of the
3-space with an accelerating phase.Comment: 0
Auxiliary-field quantum Monte Carlo study of first- and second-row post-d elements
A series of calculations for the first- and second-row post-d elements (Ga-Br
and In-I) are presented using the phaseless auxiliary-field quantum Monte Carlo
(AF QMC) method. This method is formulated in a Hilbert space defined by any
chosen one-particle basis, and maps the many-body problem into a linear
combination of independent-particle solutions with external auxiliary fields.
The phase/sign problem is handled approximately by the phaseless formalism
using a trial wave function, which in our calculations was chosen to be the
Hartree-Fock solution. We used the consistent correlated basis sets of Peterson
and coworkers, which employ a small core relativistic pseudopotential. The AF
QMC results are compared with experiment and with those from density-functional
(GGA and B3LYP) and coupled-cluster CCSD(T) calculations. The AF QMC total
energies agree with CCSD(T) to within a few milli-hartrees across the systems
and over several basis sets. The calculated atomic electron affinities,
ionization energies, and spectroscopic properties of dimers are, at large basis
sets, in excellent agreement with experiment.Comment: 10 pages, 2 figures. To be published in Journal of Chemical Physic
The Central Engines of Gamma-Ray Bursts
Leading models for the "central engine" of long, soft gamma-ray bursts (GRBs)
are briefly reviewed with emphasis on the collapsar model. Growing evidence
supports the hypothesis that GRBs are a supernova-like phenomenon occurring in
star forming regions, differing from ordinary supernovae in that a large
fraction of their energy is concentrated in highly relativistic jets. The
possible progenitors and physics of such explosions are discussed and the
important role of the interaction of the emerging relativistic jet with the
collapsing star is emphasized. This interaction may be responsible for most of
the time structure seen in long, soft GRBs. What we have called "GRBs" may
actually be a diverse set of phenomena with a key parameter being the angle at
which the burst is observed. GRB 980425/SN 1988bw and the recently discovered
hard x-ray flashes may be examples of this diversity.Comment: 8 pages, Proc. Woods Hole GRB meeting, Nov 5 - 9 WoodsHole
Massachusetts, Ed. Roland Vanderspe
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