135 research outputs found
Insect pestsâ incidence and variations due to forest landscape degradation in the humid forest zone of Southern Cameroon: farmersâ perception and need for adopting an integrated pest management strategy
Group surveys were conducted in five villages in each of the three resource-use zones of the humid forest zone of Southern Cameroon, to assess insect pestsâ incidence and the variation due to forest landscape degradation in the agricultural production systems. 389 farmers were interviewed. The results show that: (1) In annual crop systems, insect pests in general rank together with vertebrate pests and diseases amongst the most important agronomic constraints. No differences were found between the intensification zones, except for weeds, which appeared to be a greater constraint in the slightly degraded area. Within the insect pest, the greatest damage to crops according to farmers originated from borers and scales, followed by variegated grasshopper. Only the termites showed a difference between zones - the problem being greatest in the high-degraded areas. (2) In the young perennial crop systems, all the categories of agronomic constraints were equally important. Within the insect pest, mirids were identified as the greatest constraint, followed by borers and caterpillars. There were more variations in the responses according to zones compared to annual crops. Termites and scales were relatively more important in the high-degraded area. In term of control strategy, we recommended an integrated pest management.Keywords: Farmers, pest, insect, annual crop, perennial crop, integrated pest managemen
Farmers' perception on the importance of variegated grasshopper (Zonocerus variegatus (L.)) in the agricultural production systems of the humid forest zone of Southern Cameroon
BACKGROUND: Zonocerus variegatus (Linnaeus, 1758) (Orthoptera: Pyrgomorphidae) is known as an agricultural pest in West and Central Africa. However, its importance in the agricultural production system in Cameroon has not been investigated. The study assesses farmers' perception on the importance of Z. variegatus in the agricultural production systems of the humid forest zone of Southern Cameroon. METHODS: Research was carried out in 5 villages of each of three Agro-Ecological, Cultural and Demographic Blocks (AECD-Blocks) of the Forest Margin Benchmark Area (FMBA). In each village, a semi-structured survey was used; male and female groups of farmers were interviewed separately. RESULTS: Z. variegatus is present throughout the humid forest zone of Southern Cameroon, where it is ranked as the third most economically important insect pest of agriculture. In the farmers' opinion, Z. variegatus is a polyphagous insect with little impact on young perennial crops. The length of the pre-farming fallow does not affect Z. variegatus pest pressure in the following crops. The increased impact of the grasshopper observed today in the fields, compared to what existed 10 years ago is as a result of deforestation and increase in surface of herbaceous fallow. The damage caused by Z. variegatus is higher in fields adjacent to C. odorata and herbaceous fallows than in those adjacent to forests and shrubby fallows. The fight against this grasshopper is often done through physical methods carried out by hand, for human consumption. The farmers highlight low usage of the chemical methods and a total absence of biological and ecological methods. CONCLUSION: Farmers' perception have contributed to understanding the status of Z. variegatus in the humid forest zone of Southern Cameroon. The results are in general similar to those obtained in other countries
Approche dĂ©cisionnelle gĂ©ospatiale et multicritĂšre dans lâidentification des zones potentielles de recharge des eaux souterraines : cas du bassin versant du Mayo Bocki au Nord Cameroun
La prĂ©sente Ă©tude a Ă©tĂ© effectuĂ©e pour dĂ©terminer les zones potentielles de recharge des eaux souterraines. Pour ce faire, la dĂ©marche mĂ©thodologique Ă©tait basĂ©e sur lâanalyse multicritĂšre associĂ©e aux techniques gĂ©ospatiales. Les donnĂ©es utilisĂ©es Ă©taient entre autres les images satellitaires, les fonds cartographiques, les donnĂ©es pluviomĂ©triques et les niveaux statiques. Ces donnĂ©es ont permis dâexprimer sous forme de carte thĂ©matique les facteurs rĂ©gissant la recharge (pente, drainage, lithologie, fracturation, sol, pluviomĂ©trie et occupation du sol). Lâanalyse de sensibilitĂ© par suppression dâun paramĂštre a permis dâĂ©tablir lâordre dâinfluence suivant : Lit > Sol > AACH > Df > Pl > Pe > Dd > OS. Le croisement de tous ces paramĂštres aprĂšs pondĂ©ration a conduit Ă lâĂ©laboration de la carte qui montre que les zones Ă ort potentiel occupent 3 % de la zone dâĂ©tude pendant que les zones de faible Ă faible potentialitĂ© sont de lâordre de 58 % dans le bassin. Les zones Ă potentialitĂ© moyenne quant Ă elles reprĂ©sentent 39%. Ce support cartographique constitue indĂ©niablement un outil dâaide Ă la dĂ©cision pour les gestionnaires de lâeau.
This study was carried out to determine potential groundwater recharge areas. To do this, the methodological approach was based on multi-criteria analysis associated with geospatial techniques. The data used were, among others, satellite images, base maps, rainfall data and static levels. These data made it possible to express in the form of a thematic map the factors governing the recharge (slope, drainage, lithology, fracturing, soil, rainfall and land use). The sensitivity analysis by deletion of a parameter made it possible to establish the following order of influence: Lit > Sol > AACH > Df > Pl > Pe > Dd > OS. The crossing of all these parameters after weighting led to the development of the map of potential recharge zones which revealed that the zones with high potential occupy 3% of the study zone while the zones with low to low potentiality are around 58% in the basin. Areas with average potential represent 39%. This cartographic support is undeniably a decision-making tool for water managers
Numérotation des graphes sociaux basée sur les communautés pour la réduction des défauts de cache
Last version asked for publication 10th may; finally accepted in 6th April 2017; Accepted after minor changes in 17th October 2016,International audienceABSTRACT. One of social graph's properties is the community structure, that is, subsets where nodes belonging to the same subset have a higher link density between themselves and a low link density with nodes belonging to external subsets. Futhermore, most social network mining algorithms comprise a local exploration of the underlying graph, which consists in referencing nodes in the neighborhood of a particular node. The idea of this paper is to use the community structure during the storage of large graphs that arise in social network mining. The goal is to reduce cache misses and consequently, execution time. After formalizing the problem of social network ordering as a problem of optimal linear arrangement which is known as NP-Complet, we propose NumBaCo, a heuristic based on the community structure. We present for Katz score and Pagerank, simulations that compare classic data structures Bloc and Yale to their corresponding versions that use NumBaCo. Results on a 32 cores NUMA machine using amazon, dblp and web-google datasets show that NumBaCo allows to reduce from 62% to 80% of cache misses and from 15% to 50% of execution time.L'une des propriĂ©tĂ©s des graphes sociaux est leur structure en communautĂ©s, c'est-Ă -dire en sous-ensembles oĂč les noeuds ont une forte densitĂ© de liens entre eux et une faible den-sitĂ© de liens avec l'extĂ©rieur. Par ailleurs, la plupart des algorithmes de fouille des rĂ©seaux sociaux comportent une exploration locale du graphe sous-jacent, ce qui amĂšne Ă partir d'un noeud, Ă faire rĂ©fĂ©rence aux noeuds situĂ©s dans son voisinage. L'idĂ©e de cet article est d'exploiter la structure en communautĂ©s lors du stockage des grands graphes qui surviennent dans la fouille des rĂ©seaux so-ciaux. L'objectif est de rĂ©duire le nombre de dĂ©fauts de cache avec pour consĂ©quence l'amĂ©lioration du temps d'exĂ©cution. AprĂšs avoir formalisĂ© le problĂšme de numĂ©rotation des noeuds des rĂ©seaux sociaux comme un problĂšme d'arrangement linĂ©aire optimal qui est connu comme NP-Complet, nous proposons NumBaCo, une heuristique basĂ©e sur la struture en communautĂ©s. Nous prĂ©sentons pour le score de Katz et Pagerank, des simulations comparant les structures de donnĂ©es classiques Bloc et Yale Ă leurs versions exploitant NumBaCo. Les rĂ©sultats obtenus sur une machine NUMA de 32 coeurs Ă partir des jeux de donnĂ©es amazon, dblp et web-google montrent que NumBaCo contribue Ă diminuer les dĂ©fauts de cache de 62% Ă 80% et le temps d'exĂ©cution de 15% Ă 50%
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Tracking the Development of Muscular Myoglobin Stores in Mysticete Calves
For marine mammals, the ability to tolerate apnea and make extended dives is a defining adaptive trait, facilitating the exploitation of marine food resources. Elevated levels of myoglobin within the muscles are a consistent hallmark of this trait, allowing oxygen collected at the surface to be stored in the muscles and subsequently used to support extended dives. In mysticetes, the largest of marine predators, details on muscular myoglobin levels are limited. The developmental trajectory of muscular myoglobin stores has yet to be documented and any physiological links between early behavior and the development of muscular myoglobin stores remain unknown. In this study, we used muscle tissue samples from stranded mysticetes to investigate these issues. Samples from three different age cohorts and three species of mysticetes were included (total sample size = 18). Results indicate that in mysticete calves, muscle myoglobin stores comprise only a small percentage (17â23%) of conspecific adult myoglobin complements. Development of elevated myoglobin levels is protracted over the course of extended maturation in mysticetes. Additionally, comparisons of myoglobin levels between and within muscles, along with details of interspecific differences in rates of accumulation of myoglobin in very young mysticetes, suggest that levels of exercise may influence the rate of development of myoglobin stores in young mysticetes. This new information infers a close interplay between the physiology, ontogeny and early life history of young mysticetes and provides new insight into the pressures that may shape adaptive strategies in migratory mysticetes. Furthermore, the study highlights the vulnerability of specific age cohorts to impending changes in the availability of foraging habitat and marine resources
Opposite-side flavour tagging of B mesons at the LHCb experiment
The calibration and performance of the oppositeside
flavour tagging algorithms used for the measurements
of time-dependent asymmetries at the LHCb experiment
are described. The algorithms have been developed using
simulated events and optimized and calibrated with
B
+ âJ/ÏK
+, B0 âJ/ÏK
â0 and B0 âD
ââ
Ό
+
ΜΌ decay
modes with 0.37 fbâ1 of data collected in pp collisions
at
â
s = 7 TeV during the 2011 physics run. The oppositeside
tagging power is determined in the B
+ â J/ÏK
+
channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty
is statistical and the second is systematic
Measurement of the CP-violating phase phi_s in the decay Bs->J/psi phi
We present a measurement of the time-dependent CP-violating asymmetry in B_s
-> J/psi phi decays, using data collected with the LHCb detector at the LHC.
The decay time distribution of B_s -> J/psi phi is characterized by the decay
widths Gamma_H and Gamma_L of the heavy and light mass eigenstates of the
B_s-B_s-bar system and by a CP-violating phase phi_s. In a sample of about 8500
B_s -> J/psi phi events isolated from 0.37 fb^-1 of pp collisions at sqrt(s)=7
TeV we measure phi_s = 0.15 +/- 0.18 (stat) +/- 0.06 (syst) rad. We also find
an average B_s decay width Gamma_s == (Gamma_L + Gamma_H)/2 = 0.657 +/- 0.009
(stat) +/- 0.008 (syst) ps^-1 and a decay width difference Delta Gamma_s ==
Gamma_L - Gamma_H} = 0.123 +/- 0.029 (stat) +/- 0.011 (syst) ps^-1. Our
measurement is insensitive to the transformation (phi_s,DeltaGamma_s --> pi -
phi_s, - Delta Gamma_s.Comment: 9 pages, 3 figure
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
Search for CP violation in decays
A model-independent search for direct CP violation in the Cabibbo suppressed
decay in a sample of approximately 370,000 decays is
carried out. The data were collected by the LHCb experiment in 2010 and
correspond to an integrated luminosity of 35 pb. The normalized Dalitz
plot distributions for and are compared using four different
binning schemes that are sensitive to different manifestations of CP violation.
No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
Measurement of charged particle multiplicities in collisions at TeV in the forward region
The charged particle production in proton-proton collisions is studied with
the LHCb detector at a centre-of-mass energy of TeV in different
intervals of pseudorapidity . The charged particles are reconstructed
close to the interaction region in the vertex detector, which provides high
reconstruction efficiency in the ranges and
. The data were taken with a minimum bias trigger, only requiring
one or more reconstructed tracks in the vertex detector. By selecting an event
sample with at least one track with a transverse momentum greater than 1 GeV/c
a hard QCD subsample is investigated. Several event generators are compared
with the data; none are able to describe fully the multiplicity distributions
or the charged particle density distribution as a function of . In
general, the models underestimate the charged particle production
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