924 research outputs found
A provisional survey of the interaction between net photosynthetic rate, respiratory rate, and thallus water content in some New Zealand cryptogams
The effect of water content on photosynthetic and respiratory rates in eight lichen species and one bryophyte species were studied using an injection infrared gas analyser technique. All species snowed a strong relationship between net assimilation rate (NAR), respiration rate, and water content similar to relationships reported in published studies overseas. Species from moist habitats showed negative NAR at low water contents. Species from high-light areas showed a depression in NAR at high water contents which could be alleviated by higher light intensities. The experiments confirmed the suitability of New Zealand species for these studies
Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point in Supercooled Confined Water
By confining water in nano-pores of silica glass, we can bypass the
crystallization and study the pressure effect on the dynamical behavior in
deeply supercooled state using neutron scattering. We observe a clear evidence
of a cusp-like fragile-to-strong (F-S) dynamic transition. Here we show that
the transition temperature decreases steadily with an increasing pressure,
until it intersects the homogenous nucleation temperature line of bulk water at
a pressure of 1600 bar. Above this pressure, it is no longer possible to
discern the characteristic feature of the F-S transition. Identification of
this end point with the possible second critical point is discussed.Comment: 4 pages, 3 figure
Effect of acoustic absorption by hydrophone and cable on a reverberation technique for measuring sound absorption coefficient of particulate suspensions
Charm meson scattering cross sections by pion and rho meson
Using the local flavor SU(4) gauge invariance in the limit of vanishing
vector meson masses, we extend our previous study of charm meson scattering
cross sections by pion and rho meson, which is based only on the
pseudoscalar-pseudoscalar-vector meson couplings, to include also contributions
from the couplings among three vector mesons and among four particles. We find
that diagrams with light meson exchanges usually dominate the cross sections.
For the processes considered previously, the additional interactions lead only
to diagrams involving charm meson exchanges and contact interactions, and the
cross sections for these processes are thus not much affected. Nevertheless,
these additional interactions introduce new processes with light meson
exchanges and increase significantly the total scattering cross sections of
charm mesons by pion and rho meson.Comment: 14 pages, revtex, 6 figures, added a figure on the effects of
on-shell divergence, final version to appear in Nucl. Phys.
Brane Universes with Gauss-Bonnet-Induced-Gravity
The DGP brane world model allows us to get the observed late time
acceleration via modified gravity, without the need for a ``dark energy''
field. This can then be generalised by the inclusion of high energy terms, in
the form of a Gauss-Bonnet bulk. This is the basis of the
Gauss-Bonnet-Induced-Gravity (GBIG) model explored here with both early and
late time modifications to the cosmological evolution. Recently the simplest
GBIG models (Minkowski bulk and no brane tension) have been analysed. Two of
the three possible branches in these models start with a finite density
``Big-Bang'' and with late time acceleration. Here we present a comprehensive
analysis of more general models where we include a bulk cosmological constant
and brane tension. We show that by including these factors it is possible to
have late time phantom behaviour.Comment: 12 pages, 19 figures. Minor modifications to text, comments on
phantom behaviour added. References added. As submitted to JCA
A Comparison of Random Forest with ECOC-Based Classifiers
We compare experimentally the performance of three approaches to ensemble-based classification on general multi-class datasets. These are the methods of random forest, error-correcting output codes (ECOC) and ECOC enhanced by the use of bootstrapping and class-separability weighting (ECOC-BW). These experiments suggest that ECOC-BW yields better generalisation performance than either random forest or unmodified ECOC. A bias-variance analysis indicates that ECOC benefits from reduced bias, when compared to random forest, and that ECOC-BW benefits additionally from reduced variance. One disadvantage of ECOC-based algorithms, however, when compared with random forest, is that they impose a greater computational demand leading to longer training times
Wear resistant multilayer nanocomposite WC1âx/C coating on Tiâ6Alâ4V titanium alloy
A significant improvement of tribological properties on Tiâ6Alâ4V has been achieved by developed in this study multilayer treatment method for the titanium alloys. This treatment consists of an intermediate 2 ÎŒm thick TiCxNy layer which has been deposited by the reactive arc evaporation onto a diffusion hardened material with interstitial O or N atoms by glow discharge plasma in the atmosphere of Ar+O2 or Ar+N2. Subsequently, an external 0.3 ÎŒm thin nanocomposite carbon-based WC1âx/C coating has been deposited by a reactive magnetron sputtering of graphite and tungsten targets. The morphology, microstructure, chemical and phase compositions of the substrate material after treatment and coating deposition have been investigated with use of AFM, SEM, EDX, XRD, 3D profilometry and followed by tribological investigation of wear and friction analysis. An increase of hardness in the diffusion treated near-surface zone of the Tiâ6Alâ4V substrate has been achieved. In addition, a good adhesion between the intermediate gradient TiCxNy coating and the Tiâ6Alâ4V substrate as well as with the external nanocomposite coating has been obtained. Significant increase in wear resistance of up to 94% when compared to uncoated Tiâ6Alâ4V was reported. The proposed multilayer system deposited on the Tiâ6Alâ4V substrate is a promising method to significantly increase wear resistance of titanium alloys
Tensile Forces and Shape Entropy Explain Observed Crista Structure in Mitochondria
A model is presented from which the observed morphology of the inner
mitochondrial membrane can be inferred as minimizing the system's free energy.
Besides the usual energetic terms for bending, surface area, and pressure
difference, our free energy includes terms for tension that we believe to be
exerted by proteins and for an entropic contribution due to many dimensions
worth of shapes available at a given energy.
In order to test the model, we measured the structural features of
mitochondria in HeLa cells and mouse embryonic fibroblasts using 3D electron
tomography. Such tomograms reveal that the inner membrane self-assembles into a
complex structure that contains both tubular and flat lamellar crista
components. This structure, which contains one matrix compartment, is believed
to be essential to the proper functioning of mitochondria as the powerhouse of
the cell. We find that tensile forces of the order of 10 pN are required to
stabilize a stress-induced coexistence of tubular and flat lamellar cristae
phases. The model also predicts \Deltap = -0.036 \pm 0.004 atm and \sigma=0.09
\pm 0.04 pN/nm
The early evolution of the H-free process
The H-free process, for some fixed graph H, is the random graph process
defined by starting with an empty graph on n vertices and then adding edges one
at a time, chosen uniformly at random subject to the constraint that no H
subgraph is formed. Let G be the random maximal H-free graph obtained at the
end of the process. When H is strictly 2-balanced, we show that for some c>0,
with high probability as , the minimum degree in G is at least
. This gives new lower bounds for
the Tur\'an numbers of certain bipartite graphs, such as the complete bipartite
graphs with . When H is a complete graph with we show that for some C>0, with high probability the independence number of
G is at most . This gives new lower bounds
for Ramsey numbers R(s,t) for fixed and t large. We also obtain new
bounds for the independence number of G for other graphs H, including the case
when H is a cycle. Our proofs use the differential equations method for random
graph processes to analyse the evolution of the process, and give further
information about the structure of the graphs obtained, including asymptotic
formulae for a broad class of subgraph extension variables.Comment: 36 page
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