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Pyrethroid insecticides were intensively used against Cydia pomonella in the Río Negro and Neuquén valley, main production area of pome fruits in Argentina. Therefore, the first objective was to evaluate lambda-cyhalothrin resistance levels in C. pomonella larvae from orchards in this area that are currently under pyrethroids treatments. The second objective was to evaluate the frequency of kdr mutation in C. pomonella across Argentina. High levels of resistance to lambda-cyhalothrin (resistance ratios > 30) were determined in all the populations evaluated. The L1014F (kdr) mutation was evaluated in 355 diapausing larvae collected in 12 orchards from San Juan to Santa Cruz provinces (1690 km away from each other). The highest frequency of kdr mutation was determined in larvae from the Río Negro and Neuquén valley (0.61), followed by those from Mendoza (0.36). The kdr allele was absent or present at very low frequencies in orchards subjected to low pyrethroid pressure. The frequency of detection of kdr mutation in C. pomonella from Argentina is related to the use of pyrethroids against this pest in different areas. Target-site insensitivity is, at least, one of the mechanisms involved in resistance to lambda-cyhalothrin in codling moth from the Río Negro and Neuquén valley.
The epidemiology of H5N1 and H7N9 avian viruses of humans infected in China differs despite both viruses being avian reassortants that have inherited six internal genes from a common ancestor, H9N2. The median age of infected populations is substantially younger for H5N1 virus (26 years) compared with H7N9 virus (63 years). Population susceptibility to infection with seasonal influenza is understood to be influenced by cross-reactive CD8+ T cells directed towards immunogenic peptides derived from internal viral proteins which may provide some level of protection against further influenza infection. Prior exposure to seasonal influenza peptides may influence the age-related infection patterns observed for H5N1 and H7N9 viruses. A comparison of relatedness of immunogenic peptides between historical human strains and the two avian emerged viruses was undertaken for a possible explanation in the differences in age incidence observed. There appeared to be some relationship between past exposure to related peptides and the lower number of H5N1 virus cases in older populations, however the relationship between prior exposure and older populations among H7N9 virus patients was less clear.
The component of the neoclassical electrostatic potential that is non-constant on the magnetic surface, that we denote by
, can affect radial transport of highly charged impurities, and this has motivated its inclusion in some modern neoclassical codes. The number of neoclassical simulations in which
is calculated is still scarce, partly because they are usually demanding in terms of computational resources, especially at low collisionality. In this paper the size, the scaling with collisionality and with aspect ratio and the structure of
on the magnetic surface are analytically derived in the
and superbanana-plateau regimes of stellarators close to omnigeneity; i.e. stellarators that have been optimized for neoclassical transport. It is found that the largest
that the neoclassical equations admit scales linearly with the inverse aspect ratio and with the size of the deviation from omnigeneity. Using a model for a perturbed omnigenous configuration, the analytical results are verified and illustrated with calculations by the code KNOSOS. The techniques, results and numerical tools employed in this paper can be applied to neoclassical transport problems in tokamaks with broken axisymmetry.
The collisionless axisymmetric zonal flow residual calculation for a tokamak plasma is generalized to include electromagnetic perturbations. We formulate and solve the complete initial value zonal flow problem by retaining the fully self-consistent axisymmetric spatial perturbations in the electric and magnetic fields. Simple expressions for the electrostatic, shear and compressional magnetic residual responses are derived that provide a fully electromagnetic test of the zonal flow residual in gyrokinetic codes. Unlike the electrostatic potential, the parallel vector potential and the parallel magnetic field perturbations need not relax to flux functions for all possible initial conditions.
Historical outbreaks can be an important source of information in the understanding of norovirus evolution and epidemiology. Here, we revisit an outbreak of undiagnosed gastroenteritis that occurred in Shippensburg, Pennsylvania in 1972. Nearly 5000 people fell ill over the course of 10 days. Symptoms included diarrhea, vomiting, stomach cramps, and fever, lasting for a median of 24 h. Using current techniques, including next-generation sequencing of full-length viral genomic amplicons, we identified an unusual norovirus recombinant (GII.Pg/GII.3) in nine of 15 available stool samples from the outbreak. This particular recombinant virus has not been reported in recent decades, although GII.3 and GII.Pg genotypes have been detected individually in current epidemic strains. The consensus nucleotide sequences were nearly identical among the four viral genomes analysed, although each strain had three to seven positions in the genome with heterogenous non-synonymous nucleotide subpopulations. Two of these resulting amino acid polymorphisms were conserved in frequency among all four cases, consistent with common source exposure and successful transmission of a mixed viral population. Continued investigation of variant nucleotide populations and recombination events among ancestral norovirus strains such as the Shippensburg virus may provide unique insight into the origin of contemporary strains.
In cattle, reduced reproductive efficiency of beef and milk production systems is attributed to nutritional factors, health, climate changes and ultimately to genetic characteristics of animals. However, under warm humid tropics genetic variations between breeds could reduce age first calving, calving interval and increase the life of cows. Sanmartinero and Casanareño creole breeds can improve cattle production due to the contribution of genetic variants that emerged in the process of adaptation to the harsh conditions of the Colombian Orinoqia. Currently, genes with known biological function are used as molecular markers to estimate livestock genetic diversity parameters, facilitating the identification and location of genetic loci within the genome that encode or regulate the expression of traits of economic interest. In Colombia Romosinuano cattle candidate genes of the Growth hormone / Insulin growth factor axis have been identified and are positively associated with age at first calving, calving interval, longevity and protection of the embryo growth to heat stress. However, native Colombian bovine breeds such as Casanareño and Sanmartinero, which are empirically recognized by having those characteristic, have not been subjected to those genetic analysis for candidate genes that may allow to promote added value to animals. The aim of this review is to document some reproductive and genetic parameters of Sanmartinero and Casanareño bovine brees that may give support the need to conduct molecular studies and justify their use in beef and milk production systems in the Colombian Orinoquia.
People with dementia are extremely vulnerable in hospital and unscheduled
admissions should be avoided if possible.
To identify any predictors of general hospital admission in people with
dementia in a well-characterised national prospective cohort study.
A cohort of 730 persons with dementia was drawn from the Scottish
Dementia Research Interest Register (47.8% female; mean age 76.3 years,
s.d. = 8.2, range 50–94), with a mean follow-up period of 1.2 years.
In the age- and gender-adjusted multivariable model (n =
681; 251 admitted), Neuropsychiatric Inventory score (hazard ratio per
s.d. disadvantage 1.21, 95% CI 1.08–1.36) was identified as an
independent predictor of admission to hospital.
Neuropsychiatric symptoms in dementia, measured using the
Neuropsychiatric Inventory, predict non-psychiatric hospital admission of
people with dementia. Further studies are merited to test whether
interventions to reduce such symptoms might reduce unscheduled admissions
to acute hospitals.
Two of the problems that currently affect a large proportion of university students are high levels of anxiety and stress experienced in different situations, which are particularly high during the first years of their degree and during exam periods. The present study aims to investigate whether mindfulness training can bring about significant changes in the manifestations of depression, anxiety, and stress of students when compared to another group undergoing a physical activity program and a control group. The sample consisted of 125 students from the Bachelor of Education Program. The measuring instrument used was the Abbreviated Scale of Depression, Anxiety and Stress (DASS-21). The results indicate that the effects of reducing the identified variables were higher for the mindfulness group than for the physical education group and for the control group F(2) = 5.91, p = .004, η2 = .106. The total scores for all variables related to the mindfulness group decreased significantly, including an important stress reduction t(29) = 2.95, p = .006, d = .667. Mindfulness exercises and some individual relaxing exercises involving Physical Education could help to reduce manifestations of stress and anxiety caused by exams in students.
Stoichiometric 4H-SrMnO3.0 nanoparticles have been successfully synthesized for the first time from thermal decomposition of a new heterometallic precursor [SrMn(edta)(H2O)5]·3/2H2O. From this precursor, highly homogeneous 4H-SrMnO3.0 nanoparticles with average particle size 70 nm are obtained. Local structural information, provided by atomically-resolved microscopy techniques, shows that 4H-SrMnO3.0 nanoparticles exhibit the same general structural features than the bulk material, although structural disorder, due to edge-dislocations, is observed. The nanometric size of particles enables a topotactic reduction process at low temperature stabilizing a metastable 4H-SrMnO2.82 phase. The oxygen deficiency is accommodated through extra cubic layers breaking the …hchc… 4H-sequence. These defect areas are Mn3+ rich as evidenced by high energy resolution EELS data. Magnetic characterization of nano-4H-SrMnO3-δ shows significant variations with respect to the bulk material.
In this work we review the aggregation of variables method for discrete dynamical
systems. These methods consist of describing the asymptotic behaviour of a complex system
involving many coupled variables through the asymptotic behaviour of a reduced system
formulated in terms of a few global variables. We consider population dynamics models
including two processes acting at different time scales. Each process has associated a map
describing its effect along its specific time unit. The discrete system encompassing both
processes is expressed in the slow time scale composing the map associated to the slow one
and the k-th iterate of the map associated to the fast one. In the linear case a result is
stated showing the relationship between the corresponding asymptotic elements of both
systems, initial and reduced. In the nonlinear case, the reduction result establishes the
existence, stability and basins of attraction of steady states and periodic solutions of
the original system with the help of the same elements of the corresponding reduced
system. Several models looking over the main applications of the method to populations
dynamics are collected to illustrate the general results.
Spatial heterogeneity greatly affects the population spread. Although the theory for
biological invasion in heterogeneous spatially continuous habitats have received
considerable attention, spatially discrete models have remained outside of the mainstream.
In this study, we formulate and analyze a Coupled Map Lattice model for a single species
population invading a two dimensional heterogeneous environment. The population growth
rate and dispersal coefficient depend on the site quality. We first find an analytical
criterium for the spread success in terms of the population growth rate and the dispersal
coefficient in unfavorable regions. We then implemented our model for two distinct spatial
configurations: periodical stripe-like and randomized environments. The spread rate is
computed numerically and it shows a decrease with an increase of the fraction of the
hostile sites. However, we observed that invasion success does not depend on the fraction
of favorable sites but crucially depends on the connectivity of favorable regions.
This work deals with the consequences on structural stability of Gause type predator-prey
models, when are considered three standard functional responses and the prey growth rate
is subject to an Allee effect.
An important consequence of this ecological phenomenon is the existence of a separatrix
curve dividing the behavior of trajectories in the phase plane. The origin is an attractor
for any set of parameters and the existence of heteroclinic curves can be also shown.
Conditions on the parameter values are established to ensure the existence of a unique
positive equilibrium, which can be either an attractor or a repellor surrounded by one or
more limit cycles.
The influence of the Allee effect on the number of limit cycles is analyzed and the
results are compared with analogous models without this phenomenon, and which main
features have been given in various above works. Ecological interpretations of these
results are also given.
We present a mathematical model of a fishery on several sites with a variable price. The
model takes into account the evolution during the time of the resource, fishes and boats
movements between the different sites, fishing effort and price that varies with respect
to supply and demand. We suppose that boats and fishes movements as well as prices
variations occur at a fast time scale. We use methods of aggregation of variables in order
to reduce the number of variables and we derive a reduced model governing two global
variables, respectively the biomass of the resource and the fishing effort of the whole
fishery. We look for the existence of equilibria of the aggregated model. We show that the
aggregated model can have 1, 2 or 3 non trivial equilibria. We show that a variation of
the total number of sites can induce a switch from over-exploitation to sustainable
We develop a framework for analysing the outcome of resource competition based on
bifurcation theory. We elaborate our methodology by readdressing the problem of
competition of two species for two resources in a chemostat environment. In the case of
perfect-essential resources it has been extensively discussed using Tilman’s
representation of resource quarter plane plots. Our mathematically rigorous analysis
yields bifurcation diagrams with a striking similarity to Tilman’s method including the
interpretation of the consumption vector and the resource supply vector. However, our
approach is not restricted to a particular class of models but also works with other
trophic interaction formulations. This is illustrated by the analysis of a model
considering interactively-essential or complementary resources instead of
prefect-essential resources. Additionally, our approach can also be used for other
ecosystem compositions: multiple resources–multiple species communities with equilibrium
or oscillatory dynamics. Hence, it gives not only a new interpretation of Tilman’s
graphical approach, but it constitutes an extension of competition analyses to communities
with many species as well as non-equilibrium dynamics.
The release of chemicals following herbivore grazing on primary producers may provide
feeding cues to carnivorous predators, thereby promoting multitrophic interactions. In
particular, chemicals released following grazing on phytoplankton by microzooplankton
herbivores have been shown to elicit a behavioural foraging response in carnivorous
copepods, which may use this chemical information as a mechanism to locate and remain
within biologically productive patches of the ocean. In this paper, we use a 1D spatial
reaction-diffusion model to simulate a tri-trophic planktonic system in the water column,
where predation at the top trophic level (copepods) is affected by infochemicals released
by the primary producers forming the bottom trophic level. The effect of the
infochemical-mediated predation is investigated by comparing the case where copepods
forage randomly to the case where copepods adjust their vertical position to follow the
distribution of grazing-induced chemicals. Results indicate that utilization of
infochemicals for foraging provides fitness benefits to copepods and stabilizes the system
at high nutrient load, whilst also forming a possible mechanism for phytoplankton bloom
formation. We also investigate how the copepod efficiency to respond to infochemicals
affects the results, and show that small increases (2%) in the ability of copepods to
sense infochemicals can promote their persistence in the system. Finally we argue that
effectively employing infochemicals for foraging can be an evolutionarily stable strategy
The introduction of the ragweed leaf beetle in the South of Russia in 1978–1989 was
accompanied by a number of spectacular phenomena that determined the general success of
the ragweed control and further dispersal and acclimatization of the beetles:
(i) formation of solitary population waves (SPW), characterized by an
extremely high density of the phytophage population at the narrow band of the front of a
moving wave defoliating nearly all ragweed plants, and (ii) rapid, within
5-6 generations, development of flight in the leaf beetle species that in its homeland
lost the ability to fly. We present here a demogenetic model capable of reproducing both
these phenomena, assuming that the flight ability of a phytophage population is governed
by a single diallelic locus with flight and flightless alleles that determine three
genotypes of the ragweed leaf beetle. Simulation results agree well with the practical
recommendation of retaining a high density of common ragweed in the release area in order
to provide the necessary conditions for the initial increase of the leaf beetle population
and the formation of the wave. The model confirms the earlier hypothesis that the SPW is
the key factor that determines efficiency of weed biocontrol program. We demonstrate also
that the formation of the wave has crucially accelerated the development of the beetles’
ability to fly.
The formation, persistence and movement of self-organised biological aggregations are
mediated by signals (e.g., visual, acoustic or chemical) that organisms use to communicate
with each other. To investigate the effect that communication has on the movement of
biological aggregations, we use a class of nonlocal hyperbolic models that incorporate
social interactions and different communication mechanisms between group members. We
approximate the maximum speed for left-moving and right-moving groups, and show
numerically that the travelling pulses exhibited by the nonlocal hyperbolic models
actually travel at this maximum speed. Next, we use the formula for the speed of a
travelling pulse to calculate the reversal time for the zigzagging behaviour, and show
that the communication mechanisms have an effect on these reversal times. Moreover, we
show that how animals communicate with each other affects also the density structure of
the zigzags. These findings offer a new perspective on the complexity of the biological
factors behind the formation and movement of various aggregations.