2,944 research outputs found
Hematodinium-Australis N-Sp, a parasitic dinoflagellate of the sand crab Portunus-pelagicus from Moreton Bay, Australia
A new species of parasitic dinoflagellate is described from the portunid crab Portunus pelagicus. The dinoflagellate is a member of the genus Hematodinium which formerly consisted of a single species, H. perezi. Members of the genus have been reported in crabs and lobsters from Europe and North America, where in some circumstances they cause significant mortalities to host populations. The new species is the first member of the family Syndinidae to be fully described from Australia. The new species differs from other forms of Hematodinium primarily by the size of the trophont (vegetative stage), the ovoid plasmodium, and the small beaded form of condensed chromatin in the nucleus. Infection experiments indicated that the parasite may be transmitted within and between the 2 host species. in addition, the pre-patent period of the new form was at least 16 d which is much greater than that reported from other forms
The Use of a Cap-mounted Tri-axial Accelerometer for Measurement of Distance, Lap Times and Stroke Rates in Swim Training
This paper will report some of the findings from a trial which recorded accelerometer data from six elite level swimmers (three female and three male, varying primary event stroke and distance) over the course of a regular 15 week training block. Measurements from a head-mounted accelerometer are used to determine when the athlete is swimming, marking of turning points (and therefore distance and lap-time measurements), and is processed by frequency analysis to determine stroke-rate. Comparison with video where available, and with training plans and literature where not, have proven this method to be accurate and reliable for determining these performance metrics. The primary objective of this project was to develop a low-cost, simple and highly usable system for use in swim coaching, feedback from elite coaches has indicated that development of this could be an extremely useful addition to their training regime
A comparison of the galaxy peculiar velocity field with the PSCz gravity field-- A Bayesian hyper-parameter method
We constructed a Bayesian hyper-parameter statistical method to quantify the
difference between predicted velocities derived from the observed galaxy
distribution in the \textit{IRAS}-PSC redshift survey and peculiar
velocities measured using different distance indicators. In our analysis we
find that the model--data comparison becomes unreliable beyond 70 \hmpc
because of the inadequate sampling by \textit{IRAS} survey of prominent,
distant superclusters, like the Shapley Concentration. On the other hand, the
analysis of the velocity residuals show that the PSC gravity field provides
an adequate model to the local, \le 70 \hmpc, peculiar velocity field. The
hyper-parameter combination of ENEAR, SN, A1SN and SFI++ catalogues in the
Bayesian framework constrains the amplitude of the linear flow to be
. For an rms density fluctuations in the PSC galaxy
number density , we obtain an estimate of the
growth rate of density fluctuations ,
which is in excellent agreement with independent estimates based on different
techniques.Comment: 14 pages, 32 figures, MNRAS in press, matched the MNRAS published
versio
A viscous active shell theory of the cell cortex
The cell cortex is a thin layer beneath the plasma membrane that gives animal
cells mechanical resistance and drives most of their shape changes, from
migration, division to multicellular morphogenesis. It is mainly composed of
actin filaments, actin binding proteins, and myosin molecular motors.
Constantly stirred by myosin motors and under fast renewal, this material may
be well described by viscous and contractile active-gel theories. Here, we
assume that the cortex is a thin viscous shell with non-negligible curvature
and use asymptotic expansions to find the leading-order equations describing
its shape dynamics, starting from constitutive equations for an incompressible
viscous active gel. Reducing the three-dimensional equations leads to a
Koiter-like shell theory, where both resistance to stretching and bending rates
are present. Constitutive equations are completed by a kinematical equation
describing the evolution of the cortex thickness with turnover. We show that
tension and moment resultants depend not only on the shell deformation rate and
motor activity but also on the active turnover of the material, which may also
exert either contractile or extensile stress. Using the finite-element method,
we implement our theory numerically to study two biological examples of drastic
cell shape changes: osmotic shocks and cell division. Our work provides a
numerical implementation of thin active viscous layers and a generic
theoretical framework to develop shell theories for slender active biological
structures.Comment: 37 pages, 13 figures, 1 appendi
Consistently Large Cosmic Flows on Scales of 100 Mpc/h: a Challenge for the Standard LCDM Cosmology
Peculiar velocity surveys have non-uniform spatial distributions of tracers,
so that the bulk flow estimated from them does not correspond to that of a
simple volume such as a sphere. Thus bulk flow estimates are generally not
strictly comparable between surveys, even those whose effective depths are
similar. In addition, the sparseness of typical surveys can lead to aliasing of
small scale power into what is meant to be a probe of the largest scales. Here
we introduce a new method of calculating bulk flow moments where velocities are
weighted to give an optimal estimate of the bulk flow of an idealized survey,
with the variance of the difference between the estimate and the actual flow
being minimized. These "minimum variance" estimates can be designed to estimate
the bulk flow on a particular scale with minimal sensitivity to small scale
power, and are comparable between surveys. We compile all major peculiar
velocity surveys and apply this new method to them. We find that most surveys
we studied are highly consistent with each other. Taken together the data
suggest that the bulk flow within a Gaussian window of radius 50 Mpc/h is 407
km/s toward l=287 and b=8. The large-scale bulk motion is consistent with
predictions from the local density field. This indicates that there are
significant density fluctuations on very large scales. A flow of this amplitude
on such a large scale is not expected in the WMAP5-normalized LCDM cosmology,
for which the predicted one-dimensional r.m.s. velocity is ~110 km/s. The large
amplitude of the observed bulk flow favors the upper values of the WMAP5
error-ellipse, but even the point at the top of the WMAP5 95% confidence
ellipse predicts a bulk flow which is too low compared to that observed at >98%
confidence level.Comment: 19 Pages, 7 Figures, MNRAS in Press. Added some references and text
to reflect post proofs manuscrip
Calcaneal fractures in children
Eight patients with 9 calcaneal fractures were reviewed. Of the fractures 6 were intra articular and 3 extra-articular but in children this distinction appears to have little relevance to treatment or prognosis. While these fractures are relatively uncommon in children, clinical suspicion is important in making the diagnosis, since the presentation may be subtle. The overall prognosis in children is excellent
Cosmic Flows on 100 Mpc/h Scales: Standardized Minimum Variance Bulk Flow, Shear and Octupole Moments
The low order moments, such as the bulk flow and shear, of the large scale
peculiar velocity field are sensitive probes of the matter density fluctuations
on very large scales. In practice, however, peculiar velocity surveys are
usually sparse and noisy, which can lead to the aliasing of small scale power
into what is meant to be a probe of the largest scales. Previously, we
developed an optimal ``minimum variance'' (MV) weighting scheme, designed to
overcome this problem by minimizing the difference between the measured bulk
flow (BF) and that which would be measured by an ideal survey. Here we extend
this MV analysis to include the shear and octupole moments, which are designed
to have almost no correlations between them so that they are virtually
orthogonal. We apply this MV analysis to a compilation of all major peculiar
velocity surveys, consisting of 4536 measurements. Our estimate of the BF on
scales of ~ 100 Mpc/h has a magnitude of |v|= 416 +/- 78 km/s towards Galactic
l = 282 degree +/- 11 degree and b = 6 degree +/- 6 degree. This result is in
disagreement with LCDM with WMAP5 cosmological parameters at a high confidence
level, but is in good agreement with our previous MV result without an
orthogonality constraint, showing that the shear and octupole moments did not
contaminate the previous BF measurement. The shear and octupole moments are
consistent with WMAP5 power spectrum, although the measurement noise is larger
for these moments than for the BF. The relatively low shear moments suggest
that the sources responsible for the BF are at large distances.Comment: 13 Pages, 7 figures, 4 tables. Some changes to reflect the published
versio
Potassium Fertilization in the Production of Vegetables and Fruits
Consumption of vegetables worldwide has increased, not only by population growth but also by the trend of changes in consumers’ eating habits, making it inevitable to increase production. The consumer of vegetables has become more demanding, having to produce them in quantity and quality, as well as maintaining their supply throughout the year. Hydroponics is an alternative technique of cultivation in a protected environment, in which the nutritious solution is replaced by the nutrient solution. Among the essential mineral nutrients for plants, K stands out for its influence on quality attributes that affect the concentration of phytonutrients critical for human health. It acts as the determinants in the commercialization of vegetables, and can be found in various foods such as vegetables, and fruits. Adequate levels of this nutrient will benefit the consumer’s health and also prevent disease. Among the essential plant nutrients, K stands out for its influence on quality attributes that affect the concentration of phytonutrients critical to human health. The horticulturist should prioritize the use of potassic fertilizers with lower salt content, if possible free of chlorine and containing magnesium and sulfur. However, it is essential to remember that the high potassium content in plants can induce deficiency of calcium and magnesium
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