1,124 research outputs found
Glyco-biomarkers: Potential determinants of cellular physiology and pathology
Once dismissed as just the icing on the cake, sugar molecules are emerging as vital components in life’s intricate machinery. Our understanding of their function within the context of the proteins and lipids to which they are attached has matured rapidly, and with it the far reaching clinical implications are becoming understood.
Recent advances in high-throughput glycomic techniques, glyco biomarker profiling, glyco-bioinformatics and development of increasingly sophisticated glyco-arrays, combined with our increased understanding of the molecular details of glycosylation have facilitated the linkage between aberrant glycosylation and human diseases, and highlighted the possibility of using glyco-biomarkers as potential determinants of disease and its progression.
The focus of this review is to give an insight into the biological significance of these glycomodifications, highlight some specific examples of glyco-biomarkers in relation to autoimmunity and in particular rheumatoid arthritis, and to explore the exciting possibility of exploiting these for diagnostic and prognostic strategies
Radial gradients and anisotropies of cosmic rays in the interplanetary medium
Radial gradients and anisotropies of cosmic rays in interplanetary mediu
Modern theory of Fermi acceleration: a new challenge to plasma physics
One of the main features of astrophysical shocks is their ability to
accelerate particles to extremely high energies. The leading acceleration
mechanism, the diffusive shock acceleration is reviewed. It is demonstrated
that its efficiency critically depends on the injection of thermal plasma into
acceleration which takes place at the subshock of the collisionless shock
structure that, in turn, can be significantly smoothed by energetic particles.
Furthermore, their inhomogeneous distribution provides free energy for MHD
turbulence regulating the subshock strength and injection rate. Moreover, the
MHD turbulence confines particles to the shock front controlling their maximum
energy and bootstrapping acceleration. Therefore, the study of the MHD
turbulence in a compressive plasma flow near a shock is a key to understanding
of the entire process. The calculation of the injection rate became part of the
collisionless shock theory. It is argued that the further progress in diffusive
shock acceleration theory is impossible without a significant advance in these
two areas of plasma physics.Comment: 12 pages, 4 figures, invited talk at APS/ICPP, Quebec 2000, to appear
in Phys. of Plasma
Spectral universality of strong shocks accelerating charged particles
As a rule, the shock compression controls the spectrum of diffusively
accelerated particles. We argue that this is not so if the backreaction of
these particles on the shock structure is significant. We present a
self-similar solution in which the accelerated particles change the flow
structure near the shock so strongly that the total shock compression may
become arbitrarily large. Despite this, the energy spectrum behind the shock is
close to E^{-3/2} independently of anything at all.Comment: Submitted to ApJL, 4 pages, 1 figure, uses revtex and boxedep
Mathematical models of magnetospheric convection and its coupling to the ionosphere
Mathematical models of magnetospheric convection and its coupling to ionospher
Lipid Goals: Update on their Status
Goal: The goal of this lesson is to discuss current medical management of dyslipidemias, including available agents and goals of therapy, as well as potential future treatment strategies based on recently published literature
Magnetic Amplification by Magnetized Cosmic Rays in SNR Shocks
(Abridged) X-ray observations of synchrotron rims in supernova remnant (SNR)
shocks show evidence of strong magnetic field amplification (a factor of ~100
between the upstream and downstream medium). This amplification may be due to
plasma instabilities driven by shock-accelerated cosmic rays (CRs). One
candidate is the cosmic ray current-driven (CRCD) instability (Bell 2004),
caused by the electric current of large Larmor radii CRs propagating parallel
to the upstream magnetic field. Particle-in-cell (PIC) simulations have shown
that the back-reaction of the amplified field on CRs would limit the
amplification factor of this instability to less than ~10 in galactic SNRs. In
this paper, we study the possibility of further amplification driven near
shocks by "magnetized" CRs, whose Larmor radii are smaller than the length
scale of the field that was previously amplified by the CRCD instability. We
find that additional amplification can occur due to a new instability, driven
by the CR current perpendicular to the field, which we term the "perpendicular
current-driven instability" (PCDI). We derive the growth rate of this
instability, and, using PIC simulations, study its non-linear evolution and
saturation. We find that PCDI increases the amplification of the field
(amplification factor up to ~45, not including the shock compression) and
discuss its observational signatures. Our results strengthen the idea of CRs
driving a significant part of the magnetic field amplification observed in SNR
shocks.Comment: 14 pages, 10 figures; submitted to Ap
Non-thermal Origin of the EUV and Soft X-rays from the Coma Cluster - Cosmic Rays in Equipartition with the Thermal Medium
The role of cosmic rays (CR) in the formation and evolution of clusters of
galaxies has been much debated. It may well be related to other fundamental
questions, such as the mechanism which heats and virializes the intracluster
medium (ICM), and the frequency at which the ICM is shocked. There is now
compelling evidence both from the cluster soft excess (CSE) and the `hard-tail'
emissions at energies above 10 keV, that many clusters are luminous sources of
inverse-Compton (IC) emission. This is the first direct measurement of cluster
CR: the technique is free from our uncertainties in the ICM magnetic field, and
is not limited to the small subset of clusters which exhibit radio halos. The
CSE emitting electrons fall within a crucial decade of energy where they have
the least spectral evolution, and where most of the CR pressure resides.
However their survival times do not date them back to the relic CR population.
By using the CSE data of the Coma cluster, we demonstrate that the CR are
energetically as important as the thermal ICM: the two components are in
pressure equiparition. Thus, contrary to previous expectations, CR are a
dominant component of the ICM, and their origin and effects should be explored.
The best-fit CR spectral index is in agreement with the Galactic value.Comment: ApJ accepted; 10 pages LaTeX; 2 figures and 1 table in PostScrip
Proceedings of the Symposium on the Study of the Sun and Interplanetary Medium in Three Dimensions
A series of papers are presented from a symposium attended by over 200 European and American scientists to examine the importance of exploring the interplanetary medium and the sun by out-of-the-ecliptic space missions. The likely scientific returns of these missions in the areas of solar, interplanetary, and cosmic ray physics is examined. Theoretical models of the solar wind and its interaction with interplanetary magnetic fields are given
Advanced Shipboard Communications Demonstrations with ACTS
For ships at sea, satellites provide the only option for high data rate (HDR), long haul communications. Furthermore the demand for HDR satellite communications (SATCOM) for military and commercial ships, and other offshore platforms is increasing. Presently the bulk of this maritime HDR SATCOM connectivity is provided via C-band and X-band. However, the shipboard antenna sizes required to achieve a data rate of, say T1 (1.544 Mbps) with present C-/X-band SATCOM systems range from seven to ten feet in diameter. This limits the classes of ships to which HDR services can be provided to those which are large enough to accommodate the massive antennas. With its high powered K/Ka-band spot beams, the National Aeronautics and Space Administration\u27s (NASA) Advanced Communications Technology Satellite (ACTS) was able to provide T1 and higher rate services to ships at sea using much smaller shipboard antennas. This paper discusses three shipboard HDR SATCOM demonstrations that were conducted with ACTS between 1996 and 1998.
The first demonstration involved a 2 Mbps link provided to the seismic survey ship M/V Geco Diamond equipped with a 16-inch wide, 4.5-inch tall, mechanically steered slotted waveguide array antenna developed by the Jet Propulsion Laboratory. In this February 1996 demonstration ACTS allowed supercomputers ashore to process Geco Diamond\u27s voluminous oceanographic seismic data in near real time. This capability allowed the ship to adjust its search parameters on a daily basis based on feedback from the processed data, thereby greatly increasing survey efficiency.
The second demonstration was conducted on the US Navy cruiser USS Princeton (CG 59) with the same antenna used on Geco Diamond. Princeton conducted a six-month (January-July 1997) Western Hemisphere solo deployment during which time T1 connectivity via ACTS provided the ship with a range of valuable tools for operational, administrative and quality-of-life tasks. In one instance, video teleconferencing (VTC) via ACTS allowed the ship to provide life-saving emergency medical aid, assisted by specialists ashore, to a fellow mariner - the Master of a Greek cargo ship.
The third demonstration set what is believed to be the all-time SATCOM data rate record to a ship at sea, 45 Mbps in October 1998. This Lake Michigan (Chicago area) demonstration employed one of ACTS\u27 fixed beams and involved the smallest of the three vessels, the 45-foot Bayliner M/V Entropy equipped with a modified commercial-off-the-shelf one-meter antenna. A variety of multi-media services were provided to Entropy through a stressing range of sea states. These three demonstrations provided a preview of the capabilities that could be provided to future mariners on a more routine basis when K/Ka-band SATCOM systems are widely deployed
- …