7,546 research outputs found
Probing Spin-Charge Relation by Magnetoconductance in One-Dimensional Polymer Nanofibers
Polymer nanofibers are one-dimensional organic hydrocarbon systems containing
conducting polymers where the non-linear local excitations such as solitons,
polarons and bipolarons formed by the electron-phonon interaction were
predicted. Magnetoconductance (MC) can simultaneously probe both the spin and
charge of these mobile species and identify the effects of electron-electron
interactions on these nonlinear excitations. Here we report our observations of
a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI)
and polythiophene (PT) nanofibers. In PA the MC is essentially zero, but it is
present in PANI and PT. The universal scaling behavior and the zero (finite) MC
in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between
spinless charged solitons (interacting polarons which carry both spin and
charge)
Anticancer and anti-inflammatory effects of tomentosin: Cellular and molecular mechanisms
Tomentosin is a natural compound known for its presence in some medicinal plants of the Asteraceae family such as Inula viscosa. Recent studies have highlighted its anticancer and anti-inflammatory properties. Its anticancer mechanisms are unique and act at different levels ranging from cellular organization to molecular transcriptional factors and epigenetic modifications. Tomentosin’s possession of the modulatory effect on telomerase expression on tumor cell lines has captured the interest of researchers and spurred a more robust study on its anticancer effect. Since inflammation has a close link with cancer disease, this natural compound appears to be a potential cancer-fighting drug. Indeed, its recently demonstrated anti-inflammatory action can be considered as a starting point for its evaluation as an anticancer chemo-preventive agent
Universal Behavior of Load Distribution in Scale-free Networks
We study a problem of data packet transport in scale-free networks whose
degree distribution follows a power-law with the exponent . We define
load at each vertex as the accumulated total number of data packets passing
through that vertex when every pair of vertices send and receive a data packet
along the shortest path connecting the pair. It is found that the load
distribution follows a power-law with the exponent ,
insensitive to different values of in the range, ,
and different mean degrees, which is valid for both undirected and directed
cases. Thus, we conjecture that the load exponent is a universal quantity to
characterize scale-free networks.Comment: 5 pages, 5 figures, revised versio
Numerical consistency check between two approaches to radiative corrections for neutrino masses and mixings
We briefly outline the two popular approaches on radiative corrections to
neutrino masses and mixing angles, and then carry out a detailed numerical
analysis for a consistency check between them in MSSM. We find that the two
approaches are nearly consistent with a small discrepancy of a factor of 13
percent in mass eigenvalues at low energy scale, but the predictions on mixing
angles are almost consistent. We check the stability of the three types of
neutrino models, i.e., hierarchical, inverted hierarchical and degenerate
models, under radiative corrections, using both approaches, and find consistent
conclusions. The neutrino mass models which are found to be stable under
radiative corrections in MSSM are the normal hierarchical model and the
inverted hierarchical model with opposite CP parity. We also carry out
numerical analysis on some important conjectures related to radiative
corrections in MSSM, viz., radiative magnification of solar and atmospheric
mixings in case of nearly degenerate model having same CP parity (MPR
conjecture) and radiative generation of solar mass scale in exactly two-fold
degenerate model with opposite CP parity and non-zero reactor angle (JM
conjecture). We observe certain exceptions to these conjectures. Finally the
effect of scale-dependent vacuum expectation value in neutrino mass
renormalisation is discussed.Comment: 26 pages, 5 figures,references added, typos corrected and text
modifie
Synthetic RNA Silencing of Actinorhodin Biosynthesis in Streptomyces coelicolor A3(2)
We demonstrate the first application of synthetic RNA gene silencers in Streptomyces coelicolor A3(2). Peptide nucleic acid and expressed antisense RNA silencers successfully inhibited actinorhodin production. Synthetic RNA silencing was target-specific and is a new tool for gene regulation and metabolic engineering studies in Streptomyces.Peer reviewe
Global organization of metabolic fluxes in the bacterium, Escherichia coli
Cellular metabolism, the integrated interconversion of thousands of metabolic
substrates through enzyme-catalyzed biochemical reactions, is the most
investigated complex intercellular web of molecular interactions. While the
topological organization of individual reactions into metabolic networks is
increasingly well understood, the principles governing their global functional
utilization under different growth conditions pose many open questions. We
implement a flux balance analysis of the E. coli MG1655 metabolism, finding
that the network utilization is highly uneven: while most metabolic reactions
have small fluxes, the metabolism's activity is dominated by several reactions
with very high fluxes. E. coli responds to changes in growth conditions by
reorganizing the rates of selected fluxes predominantly within this high flux
backbone. The identified behavior likely represents a universal feature of
metabolic activity in all cells, with potential implications to metabolic
engineering.Comment: 15 pages 4 figure
TeV-scale seesaw from a multi-Higgs model
We suggest new simple model of generating tiny neutrino masses through a
TeV-scale seesaw mechanism without requiring tiny Yukawa couplings. This model
is a simple extension of the standard model by introducing extra one Higgs
singlet, and one Higgs doublet with a tiny vacuum expectation value.
Experimental constraints, electroweak precision data and no large flavor
changing neutral currents, are satisfied since the extra doublet only has a
Yukawa interaction with lepton doublets and right-handed neutrinos, and their
masses are heavy of order a TeV-scale. Since active light neutrinos are
Majorana particles, this model predicts a neutrinoless double beta decay.Comment: 21 pages, 8 figure
Authenticated storage using small trusted hardware
A major security concern with outsourcing data storage to third-party providers is authenticating the integrity and freshness of data. State-of-the-art software-based approaches require clients to maintain state and cannot immediately detect forking attacks, while approaches that introduce limited trusted hardware (e.g., a monotonic counter) at the storage server achieve low throughput. This paper proposes a new design for authenticating data storage using a small piece of high-performance trusted hardware attached to an untrusted server. The proposed design achieves significantly higher throughput than previous designs. The server-side trusted hardware allows clients to authenticate data integrity and freshness without keeping any mutable client-side state. Our design achieves high performance by parallelizing server-side authentication operations and permitting the untrusted server to maintain caches and schedule disk writes, while enforcing precise crash recovery and write access control
Shortest paths and load scaling in scale-free trees
The average node-to-node distance of scale-free graphs depends
logarithmically on N, the number of nodes, while the probability distribution
function (pdf) of the distances may take various forms. Here we analyze these
by considering mean-field arguments and by mapping the m=1 case of the
Barabasi-Albert model into a tree with a depth-dependent branching ratio. This
shows the origins of the average distance scaling and allows a demonstration of
why the distribution approaches a Gaussian in the limit of N large. The load
(betweenness), the number of shortest distance paths passing through any node,
is discussed in the tree presentation.Comment: 8 pages, 8 figures; v2: load calculations extende
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