Petrogenesis of alkalic and calcalkalic volcanic rocks of Mormon Mountain Volcanic Field, Arizona

The Cenozoic Mormon Mountain Volcanic Field (MMVF) of northern Arizona is situated in the transition zone between the Basin and Range and the Colorado Plateau. It is composed of alkalic to sub-alkalic basalts and calcalkalic andesites, dacites, and rhyodacites. Despite their spatial and temporal association, the basalts and the calcalkalic suite do not seem to be co-genetic. The petrogenesis of primitive MMVF basalts can be explained as the result of different degrees of partial melting of a relatively homogenous, incompatible element-enriched peridotitic source. The variety of evolved basalt types was the result of subsequent fractional crystallization of olivine, spinel, and clinopyroxene from the range of primitive basalts. Crustal contamination seems to have occurred, but affected only the highly incompatible element abundances. The formation of MMVF calcalkalic rocks is most readily explained by small to moderate amounts of partial melting of an amphibolitic lower crust. This source is LREE-enriched but depleted in Rb and relatively unradiogenic Sr ( 87 Sr/ 86 Sr ∼0.7040). Calcalkalic rhyodacites may also be derived from andesitic parents by fractional crystallization. The overall petrogenesis of the MMVF complex is the result of intra-plate volcanism where mantle-derived magmas intrude and pass through thick continental crust.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47345/1/410_2004_Article_BF00376335.pd

Molecular epidemiology of mastitis pathogens of dairy cattle and comparative relevance to humans

Mastitis, inflammation of the mammary gland, can be caused by a wide range of organisms, including gram-negative and gram-positive bacteria, mycoplasmas and algae. Many microbial species that are common causes of bovine mastitis, such as Escherichia coli, Klebsiella pneumoniae, Streptococcus agalactiae and Staphylococcus aureus also occur as commensals or pathogens of humans whereas other causative species, such as Streptococcus uberis, Streptococcus dysgalactiae subsp. dysgalactiae or Staphylococcus chromogenes, are almost exclusively found in animals. A wide range of molecular typing methods have been used in the past two decades to investigate the epidemiology of bovine mastitis at the subspecies level. These include comparative typing methods that are based on electrophoretic banding patterns, library typing methods that are based on the sequence of selected genes, virulence gene arrays and whole genome sequencing projects. The strain distribution of mastitis pathogens has been investigated within individual animals and across animals, herds, countries and host species, with consideration of the mammary gland, other animal or human body sites, and environmental sources. Molecular epidemiological studies have contributed considerably to our understanding of sources, transmission routes, and prognosis for many bovine mastitis pathogens and to our understanding of mechanisms of host-adaptation and disease causation. In this review, we summarize knowledge gleaned from two decades of molecular epidemiological studies of mastitis pathogens in dairy cattle and discuss aspects of comparative relevance to human medicine