1,968 research outputs found
A short proof of the result on actions that characterize l∞n
No full textAbstractIt is well known that, if the identity operator on an n-dimensional Banach space V can be extended to any Banach space with the same norm, then V is isometric to l∞n. We give a short proof of the result due to B. Chalmers and B. Shekhtman (Linear Algebra and its Applications 270 (1998) 155–169) saying that the identity is (in some sense) the only such operator
GEM operation in pure noble gases and the avalanche confinement
No full textWe study the operation of the Gas Electron Multiplier (GEM) in pure Ar and almost pure Xe. Rather high gas gains obtained in pure Ar, of the order of 1000, are explained by the effect of the avalanche confinement to a GEM micro-hole. Applications to the development of non-ageing sealed photon detector filled with pure noble gases are discussed. In particular, it is shown that the photoelectron collection efficiency deteriorated in pure Ar due to electron backscattering, can be recovered by operation at a higher electric field
Both Ca2+ and Zn2+ are essential for S100A12 protein oligomerization and function
No full textBackground
Human S100A12 is a member of the S100 family of EF-hand calcium-modulated proteins that are associated with many diseases including cancer, chronic inflammation and neurological disorders. S100A12 is an important factor in host/parasite defenses and in the inflammatory response. Like several other S100 proteins, it binds zinc and copper in addition to calcium. Mechanisms of zinc regulation have been proposed for a number of S100 proteins e.g. S100B, S100A2, S100A7, S100A8/9. The interaction of S100 proteins with their targets is strongly dependent on cellular microenvironment.
Results
The aim of the study was to explore the factors that influence S100A12 oligomerization and target interaction. A comprehensive series of biochemical and biophysical experiments indicated that changes in the concentration of calcium and zinc led to changes in the oligomeric state of S100A12. Surface plasmon resonance confirmed that the presence of both calcium and zinc is essential for the interaction of S100A12 with one of its extracellular targets, RAGE – the Receptor for Advanced Glycation End products. By using a single-molecule approach we have shown that the presence of zinc in tissue culture medium favors both the oligomerization of exogenous S100A12 protein and its interaction with targets on the cell surface.
Conclusion
We have shown that oligomerization and target recognition by S100A12 is regulated by both zinc and calcium. Our present work highlighted the potential role of calcium-binding S100 proteins in zinc metabolism and, in particular, the role of S100A12 in the cross talk between zinc and calcium in cell signaling
Minimal projections and absolute projection constants for regular polyhedral spaces
No full textLet
V
=
[
v
1
,
…
,
v
n
]
V = [{v_1}, \ldots ,{v_n}]
be the
n
n
-dimensional space of coordinate functions on a set of points
v
~
⊂
R
n
\tilde v \subset {{\mathbf {R}}^n}
where
v
~
\tilde v
is the set of vertices of a regular convex polyhedron. In this paper the absolute projection constant of any
n
n
-dimensional Banach space
E
E
isometrically isomorphic to
V
⊂
C
(
v
~
)
V \subset C(\tilde v)
is computed, examples of which are the well-known cases
E
=
l
n
∞
,
l
n
1
E = l_n^\infty ,l_n^1
.</p
Debunking in a world of tribes
No full textSocial media aggregate people around common interests eliciting collective framing of narratives and worldviews. However, in such a disintermediated environment misinformation is pervasive and attempts to debunk are often undertaken to contrast this trend. In this work, we examine the effectiveness of debunking on Facebook through a quantitative analysis of 54 million users over a time span of five years (Jan 2010, Dec 2014). In particular, we compare how users usually consuming proven (scientific) and unsubstantiated (conspiracy-like) information on Facebook US interact with specific debunking posts. Our findings confirm the existence of echo chambers where users interact primarily with either conspiracy-like or scientific pages. However, both groups interact similarly with the information within their echo chamber. Then, we measure how users from both echo chambers interacted with 50,220 debunking posts accounting for both users consumption patterns and the sentiment expressed in their comments. Sentiment analysis reveals a dominant negativity in the comments to debunking posts. Furthermore, such posts remain mainly confined to the scientific echo chamber. Only few conspiracy users engage with corrections and their liking and commenting rates on conspiracy posts increases after the interaction
Critical field-exponents for secure message-passing in modular networks
No full textWe study secure message-passing in the presence of multiple adversaries in modular networks. We assume a dominant fraction of nodes in each module have the same vulnerability, i.e., the same entity spying on them. We find both analytically and via simulations that the links between the modules (interlinks) have effects analogous to a magnetic field in a spin-system in that for any amount of interlinks the system no longer undergoes a phase transition. We then define the exponents δ, which relates the order parameter (the size of the giant secure component) at the critical point to the field strength (average number of interlinks per node), and γ, which describes the susceptibility near criticality. These are found to be δ = 2 and γ = 1 (with the scaling of the order parameter near the critical point given by β = 1). When two or more vulnerabilities are equally present in a module we find δ = 1 and γ = 0 (with β ≥ 2). Apart from defining a previously unidentified universality class, these exponents show that increasing connections between modules is more beneficial for security than increasing connections within modules. We also measure the correlation critical exponent ν, and the upper critical dimension d c, finding that as for ordinary percolation, suggesting that for secure message-passing d c = 6. These results provide an interesting analogy between secure message-passing in modular networks and the physics of magnetic spin-systems
Ferroresonance transient processes in the systems of contiguity of high-voltage converter substations with power systems
No full textThe purpose of the work is to determine the methods of limitation of the effect of ferroresonance transient processes on the operation of power transmission and DC insertions and to develop recommendations for concrete objects. The author has determined the procedures for qualitative analysis of ferroresonance transient processes for circuits whose configuration corresponds to the contiguity circuits of converter substations. The author has determined the voltages acting on the insulation of basic equipment of the Tambov Substation of the EKIBASTUZ - CENTRE PPT and the Vyborg VPT, has recommended the methods of connection of loaded transformers. Main results of the work have been used in determining the requirements to the automatic control systemsAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio
Scanning systems for medical X-ray imaging
No full textDetectors for medical X-ray imaging have been exhibited significant progress during last decade. Numerous systems based on scintillating screen coupled to large area CCD or CMOS matrix have appeared. Storage phosphors were further developed towards faster readout and better detective quantum efficiency (DQE). Large flat panels based on amorphous silicon coupled to CsI were introduced on the market. Amorphous selenium flat panels have been developed that allowed pixel size smaller than 100 micron and thus could be successfully applied to mammography. (...
- …
