5,640 research outputs found
Kleinberg Navigation in Fractal Small World Networks
We study the Kleinberg problem of navigation in Small World networks when the
underlying lattice is a fractal consisting of N>>1 nodes. Our extensive
numerical simulations confirm the prediction that most efficient navigation is
attained when the length r of long-range links is taken from the distribution
P(r)~r^{-alpha}, where alpha=d_f, the fractal dimension of the underlying
lattice. We find finite-size corrections to the exponent alpha, proportional to
1/(ln N)^2
Synchronous and Asynchronous Recursive Random Scale-Free Nets
We investigate the differences between scale-free recursive nets constructed
by a synchronous, deterministic updating rule (e.g., Apollonian nets), versus
an asynchronous, random sequential updating rule (e.g., random Apollonian
nets). We show that the dramatic discrepancies observed recently for the degree
exponent in these two cases result from a biased choice of the units to be
updated sequentially in the asynchronous version
Spatial mode storage in a gradient echo memory
Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate
for efficient quantum storage and for linear optical quantum computation with
time-bin multiplexing. In this paper we investigate the spatial multimode
properties of a lambda-GEM system. Using a high-speed triggered CCD, we
demonstrate the storage of complex spatial modes and images. We also present an
in-principle demonstration of spatial multiplexing by showing selective recall
of spatial elements of a stored spin wave. Using our measurements, we consider
the effect of diffusion within the atomic vapour and investigate its role in
spatial decoherence. Our measurements allow us to quantify the spatial
distortion due to both diffusion and inhomogeneous control field scattering and
compare these to theoretical models.Comment: 11 pages, 9 figure
Fungicidal preparations from Inula viscose
Inula viscosa is a perennial plant native to the Mediterranean Basin. Extracts made from the shoots of this plant exhibited a strong fungicidal activity in vitro and in vivo. TLC analyses revealed at least 7 fungicidal compounds. Most are lipophilic. When such extracts were sprayed on the leaf surface of crop plants they effectively controlled downy mildew in grape, cucumber and tabacco; late blight in potato and tomato; gray mold in cucumber and tomato; and, powdery mildew in cucurbits and cereals. Field experiments conducted with grape vine resulted in effective control of Plasmopara viticola. The data suggest that Inula viscosa is a useful source of herbal fungicidal preparations for agricultural use
Suppression of Classical and Quantum Radiation Pressure Noise via Electro-Optic Feedback
We present theoretical results that demonstrate a new technique to be used to
improve the sensitivity of thermal noise measurements: intra-cavity intensity
stabilisation. It is demonstrated that electro-optic feedback can be used to
reduce intra-cavity intensity fluctuations, and the consequent radiation
pressure fluctuations, by a factor of two below the quantum noise limit. We
show that this is achievable in the presence of large classical intensity
fluctuations on the incident laser beam. The benefits of this scheme are a
consequence of the sub-Poissonian intensity statistics of the field inside a
feedback loop, and the quantum non-demolition nature of radiation pressure
noise as a readout system for the intra-cavity intensity fluctuations.Comment: 4 pages, 1 figur
Leishmania major LACK Antigen Is Required for Efficient Vertebrate Parasitization
The Leishmania major LACK antigen is a key target of the immune response in susceptible BALB/c mice and remains a viable vaccine candidate for human leishmaniasis. We describe the genomic organization of the four lack genes in the L. major diploid genome together with results of selected lack gene targeting. Parasites containing a single lack gene in either the upstream or downstream locus grew comparably to wild-type promastigotes in vitro, but failed to parasitize BALB/c mice efficiently, even in a T cell–deficient environment. The replication of single copy lack mutants as amastigotes was attenuated in macrophages in vitro, and parasites failed to increase in numbers in immunodeficient mice, despite their persistence over months. Complementation with an additional lack copy was sufficient to induce robust lesion development, which also occurred using parasites with two lack genes. Conversely, attempts to generate lack-null parasites failed, suggesting that LACK is required for parasite viability. These data suggest that LACK is critical for effective mammalian parasitization and thus represents a potential drug target for leishmaniasis
The leading hadronic contribution to from lattice QCD with flavours of O() improved Wilson quarks
The comparison of the theoretical and experimental determinations of the
anomalous magnetic moment of the muon constitutes one of the
strongest tests of the Standard Model at low energies. In this article, we
compute the leading hadronic contribution to using lattice QCD
simulations employing Wilson quarks. Gauge field ensembles at four different
lattice spacings and several values of the pion mass down to its physical value
are used. We apply the O() improvement programme with two discretizations of
the vector current to better constrain the approach to the continuum limit. The
electromagnetic current correlators are computed in the time-momentum
representation. In addition, we perform auxiliary calculations of the pion form
factor at timelike momenta in order to better constrain the tail of the
isovector correlator and to correct its dominant finite-size effect. For the
numerically dominant light-quark contribution, we have rescaled the lepton mass
by the pion decay constant computed on each lattice ensemble. We perform a
combined chiral and continuum extrapolation to the physical point, and our
final result is . It contains the contributions of quark-disconnected
diagrams, and the systematic error has been enlarged to account for the missing
isospin-breaking effects.Comment: 30 pages, 10 figure
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