299 research outputs found
Diversité des espÚces de mouches des fruits (Diptera : Tephritidae) dans un verger mixte dans la localité de Malang (Ngaoundéré, Cameroun)
La prĂ©sente Ă©tude avait pour but dâinventorier les espĂšces de mouches des fruits (Diptera :Tephritidae) infĂ©odĂ©es au manguier dans la localitĂ© de Malang, situĂ©e dans la rĂ©gion de lâAdamaoua (NgaoundĂ©rĂ©, Cameroun), en zone Soudano-GuinĂ©enne. Pour cela, nous avons identifiĂ© les principales espĂšces prĂ©sentes dans le verger grĂące Ă un piĂ©geage de dĂ©tection dâavril 2008 Ă avril 2009, et, dâautre part, nous avons cherchĂ© Ă connaĂźtre les espĂšces responsables des dĂ©gĂąts Ă partir du ramassage des mangues dans le verger. Au total, 83 052 adultes de mouches des fruits appartenant Ă neuf espĂšces ont Ă©tĂ© capturĂ©s et huit espĂšces ont Ă©tĂ© dĂ©terminĂ©es. LâespĂšce invasive Bactrocera invadens Drew Tsuruta & White est la plus abondante dans les piĂšges (66,55% des captures), suivie de Dacus punctatifrons (Karsch) (29,92% des captures). La troisiĂšme espĂšce par ordre dâimportance est Ceratitis cosyra (Walker) (3,38% des captures).Six autres espĂšces sont prĂ©sentes mais en trĂšs faible effectif (avec au total 0,15% des captures). Les adultes de Tephritidae qui ont Ă©mergĂ© des mangues mĂ»res ramassĂ©es sous les arbres appartiennent Ă deux espĂšcesB. invadens (98,5%) et D. punctatifrons (1,5%). Le pic de pullulation de B. invadens coĂŻncide avec celui des mangues arrivĂ©es Ă maturitĂ© alors que D. punctatifrons est surtout prĂ©sent aprĂšs la pĂ©riode de maturitĂ©des mangues. B. invadens est la principale espĂšce de Tephritidae responsable des dĂ©gĂąts sur mangues Ă Malang. Les organisations de protection phytosanitaire doivent mettre en oeuvre dans les meilleurs dĂ©lais des programmes de lutte intĂ©grĂ©e afin de pouvoir rĂ©duire les dĂ©gĂąts de cette nouvelle espĂšce invasive en dessous dâun seuil Ă©conomique de nuisibilitĂ©
ZnO Nanorods via Spray Deposition of Solutions Containing Zinc Chloride and Thiocarbamide
In this work we present the results on formation of ZnO nanorods prepared by spray of aqueous solutions containing ZnCl2and thiocarbamide (tu) at different molar ratios. It has been observed that addition of thiocarbamide into the spray solution has great impact on the size, shape and phase composition of the ZnO crystals. Obtained layers were characterized by scanning electron microscopy (SEM) equipped with energy selected backscattered electron detection system (ESB), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). Small addition of thiocarbamide into ZnCl2solution (ZnCl2:tu = 1:0.25) supports development of significantly thinner ZnO nanorods with higher aspect ratio compared to those obtained from ZnCl2solution. Diameter of ZnO rods decreases from 270 to 100 nm and aspect ratio increases from âŒ2.5 to 12 spraying ZnCl2and ZnCl2:tu solutions, respectively. According to XRD, well crystallized (002) orientated pure wurtzite ZnO crystals have been formed. However, tiny âspotââlike formations of ZnS were detected on the side planes of hexagonal rods prepared from the thiocarbamide containing solutions. Being adsorbed on the side facets of the crystals ZnS inhibits width growth and promotes longitudinalc-axis growth
Morphology-Controllable Synthesis of CeO2on a Pt Electrode
Nanoscale cerium dioxides with shape of nanoparticles, nanorods, and nanotubes were electrochemically synthesized. The morphology of CeO2was modulated by changing electrode potential and potential direction. CeO2nanorods and CeO2nanotubes were synthesized via the potentiostatic and cyclic voltammeteric methods, respectively. The morphology and structure of the obtained CeO2were characterized by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). A possible formation mechanism has been suggested to illuminate the relationship between the preparation condition and the morphology of CeO2
Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte
A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the currentâtime transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 ÎŒm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 Ă 108 cmâ2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially
Developing 1D nanostructure arrays for future nanophotonics
There is intense and growing interest in one-dimensional (1-D) nanostructures from the perspective of their synthesis and unique properties, especially with respect to their excellent optical response and an ability to form heterostructures. This review discusses alternative approaches to preparation and organization of such structures, and their potential properties. In particular, molecular-scale printing is highlighted as a method for creating organized pre-cursor structure for locating nanowires, as well as vaporâliquidâsolid (VLS) templated growth using nano-channel alumina (NCA), and deposition of 1-D structures with glancing angle deposition (GLAD). As regards novel optical properties, we discuss as an example, finite size photonic crystal cavity structures formed from such nanostructure arrays possessing highQand small mode volume, and being ideal for developing future nanolasers
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