747 research outputs found
Do the fundamental constants change with time ?
Comparisons between the redshifts of spectral lines from
cosmologically-distant galaxies can be used to probe temporal changes in
low-energy fundamental constants like the fine structure constant and the
proton-electron mass ratio. In this article, I review the results from, and the
advantages and disadvantages of, the best techniques using this approach,
before focussing on a new method, based on conjugate satellite OH lines, that
appears to be less affected by systematic effects and hence holds much promise
for the future.Comment: 15 pages, 3 figures. This is an electronic version of an invited
review article for Mod. Phys. Lett. A, published as [Mod. Phys. Lett. A, Vol.
23, No. 32, 2008, pp. 2711] (copyright World Scientific Publishing Company;
http://www.worldscientific.com/
Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor
After the very long consideration of the ideal energy source by fusion of the
protons of light hydrogen with the boron isotope 11 (boron fusion HB11) the
very first two independent measurements of very high reaction gains by lasers
basically opens a fundamental breakthrough. The non-thermal plasma block
ignition with extremely high power laser pulses above petawatt of picosecond
duration in combination with up to ten kilotesla magnetic fields for trapping
has to be combined to use the measured high gains as proof of an avalanche
reaction for an environmentally clean, low cost and lasting energy source as
potential option against global warming. The unique HB11 avalanche reaction is
are now based on elastic collisions of helium nuclei (alpha particles) limited
only to a reactor for controlled fusion energy during a very short time within
a very small volume.Comment: 11 pages, 6 figures, Submitted to Proceedings 2nd Symposium High
Power Laser Science and Engineering, 14-18 MARCH 2016, Suzhou/Chin
Closure Relations of Synchrotron Self-Compton in Afterglow stratified medium and Fermi-LAT Detected Gamma-Ray Bursts
The Second Gamma-ray Burst Catalog (2FLGC) was announced by the Fermi Large
Area Telescope (Fermi-LAT) Collaboration. It includes 29 bursts with photon
energy higher than 10 GeV. Gamma-ray burst (GRB) afterglow observations have
been adequately explained by the classic synchrotron forward-shock model,
however, photon energies greater than 10 GeV from these transient events are
challenging, if not impossible, to characterize using this afterglow model.
Recently, the closure relations (CRs) of the synchrotron self-Compton (SSC)
forward-shock model evolving in a stellar wind and homogeneous medium was
presented to analyze the evolution of the spectral and temporal indexes of
those bursts reported in 2FLGC. In this work, we provide the CRs of the same
afterglow model, but evolving in an intermediate density profile () with , taking into account the
adiabatic/radiative regime and with/without energy injection for any value of
the electron spectral index. The results show that the current model accounts
for a considerable subset of GRBs that cannot be interpreted in either
stellar-wind or homogeneous afterglow SSC model. The analysis indicates that
the best-stratified scenario is most consistent with for
no-energy injection and for energy injection.Comment: 13 pages, 3 figure
Exploring the boundaries: gene and protein identification in biomedical text
Background: Good automatic information extraction tools offer hope for automatic processing of the exploding biomedical literature, and successful named entity recognition is a key component for such tools. Methods: We present a maximum-entropy based system incorporating a diverse set of features for identifying gene and protein names in biomedical abstracts. Results: This system was entered in the BioCreative comparative evaluation and achieved a precision of 0.83 and recall of 0.84 in the “open ” evaluation and a precision of 0.78 and recall of 0.85 in the “closed ” evaluation. Conclusions: Central contributions are rich use of features derived from the training data at multiple levels of granularity, a focus on correctly identifying entity boundaries, and the innovative use of several external knowledge sources including full MEDLINE abstracts and web searches. Background The explosion of information in the biomedical domain and particularly in genetics has highlighted the need for automated text information extraction techniques. MEDLINE, the primary research database serving the biomedical community, currently contains over 14 million abstracts, with 60,000 new abstracts appearing each month. There is also an impressive number of molecular biological databases covering a
Structural Guided Scaffold Phage Display Libraries as a Source of Bio-Therapeutics
We have developed a structurally-guided scaffold phage display strategy for identification of ligand mimetic bio-therapeutics. As a proof of concept we used the ligand of integrin avb6, a tumour cell surface receptor and a major new target for imaging and therapy of many types of solid cancer. NMR structure analysis showed that RGD-helix structures are optimal for avb6 ligand-interaction, so we designed novel algorithms to generate human single chain fragment variable (scFv) libraries with synthetic VH-CDR3 encoding RGD-helix hairpins with helices of differing pitch, length and amino acid composition. Study of the lead scFv clones D25scFv and D34scFv and their corresponding VH-CDR3 derived peptides, D25p and D34p, demonstrated: specific binding to recombinant and cellular avb6; inhibition of avb6-dependent cell and ligand adhesion, avb6-dependent cell internalisation; and selective retention by avb6-expressing, but not avb6-negative, human xenografts. NMR analysis established that both the D25p and D34p retained RGD-helix structures confirming the success of the algorithm. In conclusion, scFv libraries can be engineered based on ligand structural motifs to increase the likelihood of developing powerful bio-therapeutics
Formalizing Data Deletion in the Context of the Right to be Forgotten
The right of an individual to request the deletion of their personal data by
an entity that might be storing it -- referred to as the right to be forgotten
-- has been explicitly recognized, legislated, and exercised in several
jurisdictions across the world, including the European Union, Argentina, and
California. However, much of the discussion surrounding this right offers only
an intuitive notion of what it means for it to be fulfilled -- of what it means
for such personal data to be deleted.
In this work, we provide a formal definitional framework for the right to be
forgotten using tools and paradigms from cryptography. In particular, we
provide a precise definition of what could be (or should be) expected from an
entity that collects individuals' data when a request is made of it to delete
some of this data. Our framework captures several, though not all, relevant
aspects of typical systems involved in data processing. While it cannot be
viewed as expressing the statements of current laws (especially since these are
rather vague in this respect), our work offers technically precise definitions
that represent possibilities for what the law could reasonably expect, and
alternatives for what future versions of the law could explicitly require.
Finally, with the goal of demonstrating the applicability of our framework
and definitions, we consider various natural and simple scenarios where the
right to be forgotten comes up. For each of these scenarios, we highlight the
pitfalls that arise even in genuine attempts at implementing systems offering
deletion guarantees, and also describe technological solutions that provably
satisfy our definitions. These solutions bring together techniques built by
various communities
RTVP-1 regulates glioma cell migration and invasion via interaction with N-WASP and hnRNPK
Glioblastoma (GBM) are characterized by increased invasion into the surrounding normal brain tissue. RTVP-1 is highly expressed in GBM and regulates the migration and invasion of glioma cells. To further study RTVP-1 effects we performed a pull-down assay using His-tagged RTVP-1 followed by mass spectrometry and found that RTVP-1 was associated with the actin polymerization regulator, N-WASP. This association was further validated by co-immunoprecipitation and FRET analysis. We found that RTVP-1 increased cell spreading, migration and invasion and these effects were at least partly mediated by N-WASP. Another protein which was found by the pull-down assay to interact with RTVP-1 is hnRNPK. This protein has been recently reported to associate with and to inhibit the effect of N-WASP on cell spreading. hnRNPK decreased cell migration, spreading and invasion in glioma cells. Using co-immunoprecipitation we validated the interactions of hnRNPK with N-WASP and RTVP-1 in glioma cells. In addition, we found that overexpression of RTVP-1 decreased the association of N-WASP and hnRNPK. In summary, we report that RTVP-1 regulates glioma cell spreading, migration and invasion and that these effects are mediated via interaction with N-WASP and by interfering with the inhibitory effect of hnRNPK on the function of this protein
Tenfold Magnetoconductance in a Non-Magnetic Metal Film
We present magnetoconductance (MC) measurements of homogeneously disordered
Be films whose zero field sheet conductance (G) is described by the
Efros-Shklovskii hopping law . The low field
MC of the films is negative with G decreasing 200% below 1 T. In contrast the
MC above 1 T is strongly positive. At 8 T, G increases 1000% in perpendicular
field and 500% in parallel field. In the simpler parallel case, we observe {\em
field enhanced} variable range hopping characterized by an attenuation of
via the Zeeman interaction.Comment: 9 pages including 5 figure
- …