1,202 research outputs found
Understory influence on leafroller pupunations in Hawke's bay organic apple orchard
Leafrollers (Tortricidae) were collected from apple foliage and understorey vegetation in six commercial organic apple orchards in Hawke’s Bay over one season. Assessments were made of plant species present in the understorey at the time of collection. All leafroller larvae were reared to adults on artificial diet to identify leafroller species and parasitoids. Nearly half (47%) of all leafrollers collected in these orchards were located in the understorey, highlighting the importance of understorey and its management for the control of leafroller. Dock, clover and dandeliontype plants contributed 25% to the overall understorey, yet hosted 75% of the leafrollers collected from the understorey. Dolichogenidea sp. was the most abundant parasitoid (79%) attacking leafrollers found amongst the apple foliage, whereas Glyptapanteles demeter was dominant in the understorey (61%). Generally the number of leafrollers in an orchard was proportional to the abundance of broadleaf weeds and inversely proportional to parasitis
Reflection and Ducting of Gravity Waves Inside the Sun
Internal gravity waves excited by overshoot at the bottom of the convection
zone can be influenced by rotation and by the strong toroidal magnetic field
that is likely to be present in the solar tachocline. Using a simple Cartesian
model, we show how waves with a vertical component of propagation can be
reflected when traveling through a layer containing a horizontal magnetic field
with a strength that varies with depth. This interaction can prevent a portion
of the downward-traveling wave energy flux from reaching the deep solar
interior. If a highly reflecting magnetized layer is located some distance
below the convection zone base, a duct or wave guide can be set up, wherein
vertical propagation is restricted by successive reflections at the upper and
lower boundaries. The presence of both upward- and downward-traveling
disturbances inside the duct leads to the existence of a set of horizontally
propagating modes that have significantly enhanced amplitudes. We point out
that the helical structure of these waves makes them capable of generating an
alpha-effect, and briefly consider the possibility that propagation in a shear
of sufficient strength could lead to instability, the result of wave growth due
to over-reflection.Comment: 23 pages, 5 figures. Accepted for publication in Solar Physic
Emergence of influential spreaders in modified rumor models
The burst in the use of online social networks over the last decade has
provided evidence that current rumor spreading models miss some fundamental
ingredients in order to reproduce how information is disseminated. In
particular, recent literature has revealed that these models fail to reproduce
the fact that some nodes in a network have an influential role when it comes to
spread a piece of information. In this work, we introduce two mechanisms with
the aim of filling the gap between theoretical and experimental results. The
first model introduces the assumption that spreaders are not always active
whereas the second model considers the possibility that an ignorant is not
interested in spreading the rumor. In both cases, results from numerical
simulations show a higher adhesion to real data than classical rumor spreading
models. Our results shed some light on the mechanisms underlying the spreading
of information and ideas in large social systems and pave the way for more
realistic diffusion models.Comment: 14 Pages, 6 figures, accepted for publication in Journal of
Statistical Physic
Scaling in Late Stage Spinodal Decomposition with Quenched Disorder
We study the late stages of spinodal decomposition in a Ginzburg-Landau mean
field model with quenched disorder. Random spatial dependence in the coupling
constants is introduced to model the quenched disorder. The effect of the
disorder on the scaling of the structure factor and on the domain growth is
investigated in both the zero temperature limit and at finite temperature. In
particular, we find that at zero temperature the domain size, , scales
with the amplitude, , of the quenched disorder as with and in two
dimensions. We show that , where is the
Lifshitz-Slyosov exponent. At finite temperature, this simple scaling is not
observed and we suggest that the scaling also depends on temperature and .
We discuss these results in the context of Monte Carlo and cell dynamical
models for phase separation in systems with quenched disorder, and propose that
in a Monte Carlo simulation the concentration of impurities, , is related to
by .Comment: RevTex manuscript 5 pages and 5 figures (obtained upon request via
email [email protected]
Algebro-geometric approach in the theory of integrable hydrodynamic type systems
The algebro-geometric approach for integrability of semi-Hamiltonian
hydrodynamic type systems is presented. This method is significantly simplified
for so-called symmetric hydrodynamic type systems. Plenty interesting and
physically motivated examples are investigated
A service evaluation of FIT and anaemia for risk stratification in the two week wait pathway for colorectal cancer
Introduction: New national guidance on urgent referral for investigation for Colorectal Cancer (CRC) included faecal occult blood testing in 2015. We evaluated faecal immunochemical testing (FIT) and anaemia as risk stratification tools in symptomatic patients suspected of having CRC.Methods: Postal FIT was incorporated into the CRC two week wait (2WW) pathway for all patients without rectal bleeding in 2016. Patients were investigated in the 2WW pathway as normal and outcomes of investigations were prospectively recorded. Anaemia was defined as haemoglobin less than 120g/L in women and less than 130g/L in men.Results: FIT kits were sent to 1106 patients with an 80.9% return rate; 810 patients completed investigation with 40 CRCs diagnosed (4.9%). Median FIT results were significantly higher in patients who were anaemic (median 4.8 iqr 0.8-34.1 versus 1.2 iqr 0-6.4, Mann-Whitney p less than 0.001).Some 538 (60.4%) had a result of less than 4 µgHb/gFaeces (limit of detectability) and 621 (69.7%) a result less than 10 µgHb/gFaeces. Sixty per cent of CRCs had a FIT reading of >150 µgHb/gFaeces. Five CRCs diagnosed in patients with a FIT4 µgHb/gFaeces had 97.5% sensitivity and 64.5% specificity for CRC diagnosis. A FIT result of >4 µgHb/gFaeces and/or anaemia had a 100% sensitivity and 45.3% specificity for CRC diagnosis.Conclusion: FIT is most useful at the extremes of detectability; strongly positive readings predict high rates of CRC and other significant pathology, whilst very low readings in the absence of anaemia or palpable rectal mass identify a group with very low risk. High return rates for FIT within this 2WW pathway indicate its acceptability
Measuring the 3D Clustering of Undetected Galaxies Through Cross Correlation of their Cumulative Flux Fluctuations from Multiple Spectral Lines
We discuss a method for detecting the emission from high redshift galaxies by
cross correlating flux fluctuations from multiple spectral lines. If one can
fit and subtract away the continuum emission with a smooth function of
frequency, the remaining signal contains fluctuations of flux with frequency
and angle from line emitting galaxies. Over a particular small range of
observed frequencies, these fluctuations will originate from sources
corresponding to a series of different redshifts, one for each emission line.
It is possible to statistically isolate the fluctuations at a particular
redshift by cross correlating emission originating from the same redshift, but
in different emission lines. This technique will allow detection of clustering
fluctuations from the faintest galaxies which individually cannot be detected,
but which contribute substantially to the total signal due to their large
numbers. We describe these fluctuations quantitatively through the line cross
power spectrum. As an example of a particular application of this technique, we
calculate the signal-to-noise ratio for a measurement of the cross power
spectrum of the OI(63 micron) and OIII(52 micron) fine structure lines with the
proposed Space Infrared Telescope for Cosmology and Astrophysics. We find that
the cross power spectrum can be measured beyond a redshift of z=8. Such
observations could constrain the evolution of the metallicity, bias, and duty
cycle of faint galaxies at high redshifts and may also be sensitive to the
reionization history through its effect on the minimum mass of galaxies. As
another example, we consider the cross power spectrum of CO line emission
measured with a large ground based telescope like CCAT and 21-cm radiation
originating from hydrogen in galaxies after reionization with an interferometer
similar in scale to MWA, but optimized for post-reionization redshifts.Comment: 21 pages, 6 figures; Replaced with version accepted by JCAP; Added an
example of cross correlating CO line emission and 21cm line emission from
galaxies after reionizatio
Studying Paths of Participation in Viral Diffusion Process
Authors propose a conceptual model of participation in viral diffusion
process composed of four stages: awareness, infection, engagement and action.
To verify the model it has been applied and studied in the virtual social chat
environment settings. The study investigates the behavioral paths of actions
that reflect the stages of participation in the diffusion and presents
shortcuts, that lead to the final action, i.e. the attendance in a virtual
event. The results show that the participation in each stage of the process
increases the probability of reaching the final action. Nevertheless, the
majority of users involved in the virtual event did not go through each stage
of the process but followed the shortcuts. That suggests that the viral
diffusion process is not necessarily a linear sequence of human actions but
rather a dynamic system.Comment: In proceedings of the 4th International Conference on Social
Informatics, SocInfo 201
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