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Search Results: 1 - 10 of 202556 matches for " William G MacKay "
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External quality assessment of cytomegalovirus DNA detection on dried blood spots
Maria Barbi, William G MacKay, Sandro Binda, Anton M van Loon
BMC Microbiology , 2008, DOI: 10.1186/1471-2180-8-2
Abstract: The 27 responding laboratories from 14 countries submitted 33 datasets obtained by means of conventional PCR (n = 5) or real-time PCR (n = 28) technologies. A correct positive result was reported in at least 91% of datasets in samples with a viral load of 8.8 × 104 copies/ml or higher. However only 59% and 12% identified the 9.4 × 103 and 7.3 × 102 copies/ml samples, respectively, correctly as positive. False positive results were reported by 9% of laboratories and in 11% of datasets.These results indicate a clear need for improvement of methods as sensitivity and false-positivity still appear to be a major problem in a considerable number of laboratories.Congenital CMV infection is the most widespread congenital infection in humans and is a major cause of neurological damages such as hearing loss, visual impairment and mental retardation in children. Diagnosis of congenital CMV infection requires laboratory testing done on samples collected in the first three weeks of life. Testing for CMV-DNA in neonatal blood collected on filter-paper (dried blood spot, DBS) has proved a valid means of diagnosis with both clinical and epidemiological relevance. Applications of this assay range from diagnosis in the neonatal period as an alternative to the conventional urine culture method to the unique quality of ascertaining whether damages arising during infancy are due to congenital infection [1,2].Most laboratories use an in-house developed assay for detection of CMV-DNA in DBS. However, no international standard is available and previous external quality assessment studies have shown that the quality of nucleic acid amplification methods such as PCR varies considerably between laboratories [3,4]. Therefore a quality assessment study for the detection of CMV-DNA on DBS was recommended by the European Congenital CMV Initiative (ECCI) group and was organised by QCMD (Quality Control for Molecular Diagnostics). We report the results of the CMV-DNA amplification assays performed
Dos especies nuevas de hormigas de la tribu Attini de Costa Rica y México: Mycetosoritis vinsoni y Mycocepurus curvispinosus (Hymenoptera: Formicidae)
Mackay,William P.;
Revista de Biología Tropical , 1998,
Abstract: i describe mycetosoritis vinsoni from loma barbudal, guanacaste prov., costa rica, based on a holotype worker. it is most closely related to m. hartmanni, but can be easily separated as the hairs on the scapes are curved and appressed (straight and semierect in m. hartmanni), the median pronotal denticles are absent (present and well developed in m. hartmanni) and the petiolar teeth are poorly developed (well developed in m. hartmanni). mycocepurus curvispinosus is described based on five workers from costa rica, guanacaste prov., loma barbudal and mexico, chiapas, 24 km southeast of cintalpa. it can be easily recognized as the propodeal spines are thickened and bent upwards, and the mid pronotal denticles are absent. these two characters separate this new species from all others in the genus.
Dos especies nuevas de hormigas de la tribu Attini de Costa Rica y México: Mycetosoritis vinsoni y Mycocepurus curvispinosus (Hymenoptera: Formicidae)
William P. Mackay
Revista de Biología Tropical , 1998,
Abstract: Se describe Mycetosoritis vinsoni de Loma Barbudal, Guanacaste Prov. de Costa Rica, con base en el obrera holotipo. Es similar a M. hartmanni, pero se puede diferenciar gracias a que los pelos de los escapos son curvos y oprimidos (derechos y erectos en M. hartmanni), los dentículos de la mitad del pronoto están ausentes (presentes y bien desarrollados en M. hartmanni), y los dientes del peciolo son poco diferenciados (bien desarrollados en M. hartmanni). Mycocepurus curvispinosus es descrito con base en cinco obreras de Costa Rica, Guanacaste Prov., Loma Barbudal y de México, Chiapas, 24 km suroeste de Cintalpa. Se puede separar Mycocepurus curvispinosus fácilmente porque las espinas principales del propodeo son curvadas hacia arriba y gruesas, y los dientecillos de la mitad del pronoto están ausentes. Estas dos características separan esta nueva especie del resto de las especies en el género. I describe Mycetosoritis vinsoni from Loma Barbudal, Guanacaste Prov., Costa Rica, based on a holotype worker. It is most closely related to M. hartmanni, but can be easily separated as the hairs on the scapes are curved and appressed (straight and semierect in M. hartmanni), the median pronotal denticles are absent (present and well developed in M. hartmanni) and the petiolar teeth are poorly developed (well developed in M. hartmanni). Mycocepurus curvispinosus is described based on five workers from Costa Rica, Guanacaste Prov., Loma Barbudal and Mexico, Chiapas, 24 km southeast of Cintalpa. It can be easily recognized as the propodeal spines are thickened and bent upwards, and the mid pronotal denticles are absent. These two characters separate this new species from all others in the genus.
Science and public trust
Dr. William MacKay
University of Toronto Journal of Undergraduate Life Sciences , 2007,
Abstract:
A Comparison of the Nest Phenologies ofThree Species of Pogonomyrmex Harvester Ants (Hymenoptera: Formicldae)
William P. MacKay
Psyche , 1981, DOI: 10.1155/1981/78635
Abstract:
Affine Toda Solitons and Automorphisms of Dynkin Diagrams
Niall MacKay,William McGhee
Physics , 1992, DOI: 10.1142/S0217751X93001119
Abstract: Using Hirota's method, solitons are constructed for affine Toda field theories based on the simply-laced affine algebras. By considering automorphisms of the simply-laced Dynkin diagrams, solutions to the remaining algebras, twisted as well as untwisted, are deduced.
Lasius Xerophilus (Hymenoptera: Formicidae), a New Ant SpeciesFrom White Sands National Monument, New Mexico
William P. Mackay,Emma E. Mackay
Psyche , 1994, DOI: 10.1155/1994/72694
Abstract:
A New Species of Neotropical Carpenter Ant in the Genus Camponotus (Hymenoptera: Formicidae), Apparently without Major Workers
William Mackay,Paola A. Barriga
Psyche , 2012, DOI: 10.1155/2012/382938
Abstract: We describe a new species of carpenter ants from Ecuador, which apparently has an obligatory relationship with the ant plants Cecropia membranacea Trécul, C. herthae Diels and C. marginalis Cuatrec. The workers are relatively small and hairy, and based on a number of collections, it does not appear to have major workers. We compare the new species to Camponotus balzani, to which it appears to be similar and which has normal major workers, and also lives in Cecropia spp. 1. Introduction Camponotus carpenter ants have a worldwide distribution and form one of the hyperdiverse genera together with Pheidole [1]. It is still unknown which of these two largest genera has the greater number of species as many new species await discovery. In the New World, about 650 taxa have been named in Camponotus, which will be reduced to about 440 valid species, including about 140 new species (Mackay, unpublished, manuscript available at http://www.utep.edu/leb/antgenera.htm). Other species of neotropical Camponotus have been recently described [2–4]. The revision of such a large group has taken nearly 20 years, with several more needed to complete the work. Occasionally names are needed for ecological studies, which cannot wait the completion of the entire work. We here describe an interesting new species to provide a name for an ant whose interaction with Cecropia will be described by the junior author in future papers. This species is unusual in that the workers appear to be monomorphic. The majority of the carpenter ants are dimorphic, but monomorphic workers are also found in the montivagus species complex [5, 6], subgenus Dendromyrmex [7], and some of the species in the subgenus Myrmobrachys are only weakly dimorphic. Placement of this species into a subgenus is difficult because of the lack of major workers. Based on its similarity to C. balzani and several characters listed below, we placed it in the subgenus Tanaemyrmex. The clypeal carinae of the minor worker, female, and to some extent the male are well developed. The sides of the clypeus diverge anteriorly in all three castes. The head of the minor worker is longer than broad, with large eyes that?reach the sides of the head. The minor worker is relatively large, with an elongated mesosoma, which is typical for the subgenus Tanaemyrmex. The dorsum of the mesosoma of the minor is convex and rounded and somewhat angulate between the two faces. The propodeal spiracle is elongated. The petiole is somewhat thickened (viewed from side). Appressed pubescence is sparse. The head and mesosoma are coriaceous, and the
On the effective permittivity of silver-insulator nanocomposites
Tom G. Mackay
Physics , 2006,
Abstract: The Bruggeman formalism provides an estimate of the effective permittivity of a composite material comprising two constituent materials, with each constituent material being composed of electrically small particles. When one of the constituent materials is silver and the other is an insulating material, the Bruggeman estimate of the effective permittivity of the composite exhibits resonances with respect to volume fraction that are not physically plausible.
On extended homogenization formalisms for nanocomposites
Tom G. Mackay
Physics , 2008,
Abstract: In a long wavelength regime, the effective properties of particulate composites, including nanocomposites, may be estimated using one of various homogenization formalisms, such as the Bruggeman and Maxwell Garnett formalisms, and the approach of the strong--property--fluctuation theory (SPFT). In the conventional implementations of these formalisms, the constituent particles are treated as point--like scattering centres. However, extended formalisms have been established--which involve integral formulations--that take account of the spatial extent of the constituent particles. In particular, the extended second--order SPFT takes account of both the size of the constituent particles and their statistical distributions. We derive explicit representations of the extended second--order SPFT appropriate to isotropic chiral and uniaxial dielectric homogenized composite mediums. These results may also be employed in extended versions of the Bruggeman and Maxwell Garnett formalisms.
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