Abstract:
We analyzed the response of T. infestans fifth instar nymphs after exposure to different amounts either of total epicuticular lipid extracts or individual lipid fractions. Assays were performed in a circular arena, employing a binary choice test with filter papers acting as aggregation attractive sites; papers were either impregnated with a hexane-extract of the total lipids, or lipid fraction; or with the solvent. Insects were significantly aggregated around papers impregnated with the epicuticular lipid extracts. Among the lipid fractions separately tested, only the free fatty acid fraction promoted significant bug aggregation. We also investigated the response to different amounts of selected fatty acid components of this fraction; receptiveness varied with the fatty acid chain length. No response was elicited by hexadecanoic acid (C16:0), the major fatty acid component. Octadecanoic acid (C18:0) showed a significant assembling effect in the concentration range tested (0.1 to 2 insect equivalents). The very long chain hexacosanoic acid (C26:0) was significantly attractant at low doses (≤ 1 equivalent), although a repellent effect was observed at higher doses.The detection of contact aggregation pheromones has practical application in Chagas disease vector control. These data may be used to help design new tools against triatomine bugs.The lipid layer on the insect cuticle comprises a complex mixture of hydrocarbons, free and esterified fatty acids and fatty alcohols, and smaller amounts of other oxygenated components [1,2]. Their role protecting insects from water loss and hence preventing lethal desiccation is widely recognized [3-5]. They are also the first barrier against chemical or biological contact insecticides [6,7]. Growing evidence has been gathered for more than 30 years on the role of hydrocarbons in chemical communication in many insect species [8]. However, relatively few reports are available on the participation of oxygenated cuticular lipid compo

Abstract:
capillary gas-liquid chromatography was used to analyse the cuticular hydrocarbons of three triatomine species, triatoma dimidiata, t. barberi and dipetalogaster maxima, domestic vectors of chagas disease in mexico. mixtures of saturated hydrocarbons of straight and methyl-branched chains were characteristic of the three species, but quantitatively different. major methylbranched components mostly corresponded to different saturated isomers of monomethyl, dimethyl and trimethyl branched hydrocarbons ranging from 29 to 39 carbon backbones. sex-dependant, quantitative differences in certain hydrocarbons were apparent in t. dimidiata.

Abstract:
Capillary gas-liquid chromatography was used to analyse the cuticular hydrocarbons of three triatomine species, Triatoma dimidiata, T. barberi and Dipetalogaster maxima, domestic vectors of Chagas disease in Mexico. Mixtures of saturated hydrocarbons of straight and methyl-branched chains were characteristic of the three species, but quantitatively different. Major methylbranched components mostly corresponded to different saturated isomers of monomethyl, dimethyl and trimethyl branched hydrocarbons ranging from 29 to 39 carbon backbones. Sex-dependant, quantitative differences in certain hydrocarbons were apparent in T. dimidiata.

Abstract:
Background Triatoma infestans-mediated transmission of Tripanosoma cruzi, the causative agent of Chagas disease, remains as a major health issue in southern South America. Key factors of T. infestans prevalence in specific areas of the geographic Gran Chaco region—which extends through northern Argentina, Bolivia, and Paraguay—are both recurrent reinfestations after insecticide spraying and emerging pyrethroid-resistance over the past ten years. Among alternative control tools, the pathogenicity of entomopathogenic fungi against triatomines is already known; furthermore, these fungi have the ability to fully degrade hydrocarbons from T. infestans cuticle and to utilize them as fuel and for incorporation into cellular components. Methodology and Findings Here we provide evidence of resistance-related cuticle differences; capillary gas chromatography coupled to mass spectrometry analyses revealed that pyrethroid-resistant bugs have significantly larger amounts of surface hydrocarbons, peaking 56.2±6.4% higher than susceptible specimens. Also, a thicker cuticle was detected by scanning electron microscopy (32.1±5.9 μm and 17.8±5.4 μm for pyrethroid-resistant and pyrethroid-susceptible, respectively). In laboratory bioassays, we showed that the virulence of the entomopathogenic fungi Beauveria bassiana against T. infestans was significantly enhanced after fungal adaptation to grow on a medium containing insect-like hydrocarbons as the carbon source, regardless of bug susceptibility to pyrethroids. We designed an attraction-infection trap based on manipulating T. infestans behavior in order to facilitate close contact with B. bassiana. Field assays performed in rural village houses infested with pyrethroid-resistant insects showed 52.4% bug mortality. Using available mathematical models, we predicted that further fungal applications could eventually halt infection transmission. Conclusions This low cost, low tech, ecologically friendly methodology could help in controlling the spread of pyrethroid-resistant bugs.

Abstract:
Background Current Chagas disease vector control strategies, based on chemical insecticide spraying, are growingly threatened by the emergence of pyrethroid-resistant Triatoma infestans populations in the Gran Chaco region of South America. Methodology and findings We have already shown that the entomopathogenic fungus Beauveria bassiana has the ability to breach the insect cuticle and is effective both against pyrethroid-susceptible and pyrethroid-resistant T. infestans, in laboratory as well as field assays. It is also known that T. infestans cuticle lipids play a major role as contact aggregation pheromones. We estimated the effectiveness of pheromone-based infection boxes containing B. bassiana spores to kill indoor bugs, and its effect on the vector population dynamics. Laboratory assays were performed to estimate the effect of fungal infection on female reproductive parameters. The effect of insect exuviae as an aggregation signal in the performance of the infection boxes was estimated both in the laboratory and in the field. We developed a stage-specific matrix model of T. infestans to describe the fungal infection effects on insect population dynamics, and to analyze the performance of the biopesticide device in vector biological control. Conclusions The pheromone-containing infective box is a promising new tool against indoor populations of this Chagas disease vector, with the number of boxes per house being the main driver of the reduction of the total domestic bug population. This ecologically safe approach is the first proven alternative to chemical insecticides in the control of T. infestans. The advantageous reduction in vector population by delayed-action fungal biopesticides in a contained environment is here shown supported by mathematical modeling.

The worldwide
increase of the publications concerning the assessment of marine renewable
living resources is highlighting long-standing problems with symbols and
annotations. Starting from the symbols presented within the classic
fisheries masterpieces produced, mainly in the fifty of the last century, a
first “Milestone” list was organised. Thereafter, the pertinent literature
was (not exhaustively) browsed in order to integrate this Milestone list on the
base of a set of decisional criteria. The present contribution consists in
using the Latin letters as well established symbols for the corresponding parameters,
leaving free to specific use (with few historical exceptions) the Greek letters
in view to open a discussion among all the fisheries scientists and bodies in
order to move towards a common language and better communication standards.

Abstract:
In this paper, we study the k–Lucas numbers of arithmetic indexes of the form an+r , where n is a natural number and r is less than r. We prove a formula for the sum of these numbers and particularly the sums of the first k-Lucas numbers, and then for the even and the odd k-Lucas numbers. Later, we find the generating function of these numbers. Below we prove these same formulas for the alternated k-Lucas numbers. Then, we prove a relation between the k–Fibonacci numbers of indexes of the form 2rn and the k–Lucas numbers of indexes multiple of 4. Finally, we find a formula for the sum of the square of the k-Fibonacci even numbers by mean of the k–Lucas numbers.

The
atmospheric behaviour of air is largely governed by low and high pressure
systems. However, the relationship between these systems is not linear, as
winds, sea temperatures and solar intensity modulate their dynamics and reduce
predictability. Several other factors are known to affect these atmospheric
dynamics, such as solar cycles. Recent evidence shows however that the earth’s
gravitational field can be quantized in terms of quantum numbers, as recently
published in Nature. The implications of this relationship between gravity and
quantum numbers give rise to the possible key role of a quantum behaviour of
gravity in affecting the formation of high- and low-pressure systems. In this
letter, the author suggests a relation between the recently observed quantized
nature of gravity, the weight of air and the formation of Low and High pressure
areas in the atmosphere. The theory is novel and can aid in the understanding
of interplay between the earths core forces, the gravitational behaviour and
the atmospheric dynamics. There are however several parts of this theory that
need further development, and an initial expression of this putative
relationship is introduced.

Abstract:
In this paper, we will see that
some k -Fibonacci sequences
are related to the classical Fibonacci sequence of such way that we can express the terms of a k -Fibonacci sequence in function of some terms of the
classical Fibonacci sequence. And the formulas will
apply to any sequence of a certain set of k' -Fibonacci sequences. Thus we find k -Fibonacci sequences relating to other k -Fibonacci sequences when σ'_{k} is linearly dependent of .

Proposed here is a new framework for the analysis of
complex systems as a non-explicitly programmed mathematical hierarchy of
subsystems using only the fundamental principle of causality, the mathematics
of groupoid symmetries, and a basic causal metric needed to support measurement
in Physics. The complex system is described as a discrete set S of state variables. Causality is
described by an acyclic partial order w on S, and is considered as a
constraint on the set of allowed state transitions. Causal set (S, w)
is the mathematical model of the system. The dynamics it describes is
uncertain. Consequently, we focus on invariants, particularly group-theoretical
block systems. The symmetry of S by
itself is characterized by its symmetric group, which generates a trivial block
system over S. The constraint of
causality breaks this symmetry and degrades it to that of a groupoid, which may
yield a non-trivial block system on S.
In addition, partial order w determines a partial order for the blocks, and the set of blocks becomes a
causal set with its own, smaller block system. Recursion yields a multilevel
hierarchy of invariant blocks over S with the properties of a scale-free mathematical fractal. This is the invariant
being sought. The finding hints at a deep connection between the principle of
causality and a class of poorly understood phenomena characterized by the
formation of hierarchies of patterns, such as emergence, selforganization, adaptation, intelligence, and semantics.
The theory and a thought experiment are discussed and previous evidence is
referenced. Several predictions in the human brain are confirmed with wide
experimental bases. Applications are anticipated in many disciplines, including
Biology, Neuroscience, Computation, Artificial Intelligence, and areas of
Engineering such as system autonomy, robotics, systems integration, and image
and voice recognition.