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Search Results: 1 - 10 of 219381 matches for " JOHN G; KLEIER "
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Plant community variation across a puna landscape in the Chilean Andes
LAMBRINOS,JOHN G; KLEIER,CATHERINE C; RUNDEL,PHILIP W;
Revista chilena de historia natural , 2006, DOI: 10.4067/S0716-078X2006000200009
Abstract: we describe patterns of plant species and growth form abundance in the puna vegetation of parque nacional lauca, chile. at more than 4,300 m, the extreme habitat of the study site supported relatively few species. these few species, however, represented a diverse array of growth forms that were organized with respect to distinct environmental gradients. both species richness and growth form diversity increased with the degree of habitat rockiness and on more xeric north and east facing slopes. these xeric, rocky sites supported the greatest overall abundance of cushion forms. less rocky sites with more soil development supported a greater abundance of tussock grass and shrub forms. congeneric species occupied distinct microhabitats and were often markedly divergent in growth form. these patterns suggest that water and thermal stress are critical forces shaping functional form as well as community organization in the high andean puna
Plant community variation across a puna landscape in the Chilean Andes Variación en la comunidad vegetal de un paisaje de puna en los Andes chilenos
JOHN G LAMBRINOS,CATHERINE C KLEIER,PHILIP W RUNDEL
Revista chilena de historia natural , 2006,
Abstract: We describe patterns of plant species and growth form abundance in the puna vegetation of Parque Nacional Lauca, Chile. At more than 4,300 m, the extreme habitat of the study site supported relatively few species. These few species, however, represented a diverse array of growth forms that were organized with respect to distinct environmental gradients. Both species richness and growth form diversity increased with the degree of habitat rockiness and on more xeric north and east facing slopes. These xeric, rocky sites supported the greatest overall abundance of cushion forms. Less rocky sites with more soil development supported a greater abundance of tussock grass and shrub forms. Congeneric species occupied distinct microhabitats and were often markedly divergent in growth form. These patterns suggest that water and thermal stress are critical forces shaping functional form as well as community organization in the high Andean puna Describimos los patrones de abundancia de las especies vegetales y las formas de vida en la vegetación de puna en el Parque Nacional Lauca, Chile. A una altitud que excede los 4.300 m de altitud, el hábitat extremo de nuestro sitio de estudio presenta relativamente pocas especies. Dichas especies, sin embargo, representan un arreglo diverso de formas de vida organizadas con respecto a distintos gradientes ambientales. Tanto la riqueza de especies como el hábito de crecimiento aumentaron en los suelos más rocosos y en las pendientes expuestas al norte y al este, cuya vegetación es más xerófila. Dichos sitios presentaron la mayor abundancia en formas de cojines. Los sitios menos rocosos con un suelo más desarrollado presentaron una mayor abundancia de pastos y arbustos. Distintos microhábitats fueron ocupados por especies congénericas que con frecuencia divergieron en su hábito de crecimiento. Los patrones observados sugieren que el agua y el estrés térmico son fuerzas críticas que moldean la forma funcional de las especies vegetales así como la organización de las comunidades de plantas en la puna altoandina
Diabetes mortality and environmental heavy metals in North Carolina counties: An ecological study  [PDF]
John G. Spangler
Journal of Diabetes Mellitus (JDM) , 2012, DOI: 10.4236/jdm.2012.24057
Abstract: Introduction: Arsenic, beryllium, cadmium and nickel have been associated with the prevalence of diabetes mellitus in populations exposed to these elements. However, diabetes mortality has not been evaluated. This ecological study correlated airborne concentrations of these metals with diabetes mortality in North Carolina counties. Methods: County level data were extracted from the 2000 US Census, the 1999 US Environmental Protection Agency National Air Toxins Assessment, and 2001-2005 diabetes mortality rates by county from the North Carolina State Center for Health Statistics. Multivariable linear regression correlated airborne concentrations of each element with diabetes mellitus mortality rates in all 100 North Carolina counties controlling for county-level characteristics. Airborne concentrations were logarithmically transformed to normalize their distribution. Results: The lowest air concentrations detected were beryllium and cadmium, with nickel showing the highest concentration. Logarithmic concentrations spanned from 3.74 to 4.02 orders of magnitude. County-level diabetes mortality rates were negatively associated with median county income, but positively associated with county-level air concentrations of arsenic, beryllium, cadmium and nickel. Conclusions: These results support diabetes mortality effects of air pollution, and agree with other studies correlating arsenic, beryllium, cadmium and nickel with diabetes prevalence. Policy implications include regulating point source air pollution.
The myocardial microcirculation: A key target for salvaging ischemic myocardium?  [PDF]
John G. Kingma
World Journal of Cardiovascular Diseases (WJCD) , 2013, DOI: 10.4236/wjcd.2013.35A002
Abstract: Clinical management of patients with acute myocardial infarction for the most part involves re-opening of an infarct-related coronary vessel by the use of clot-busting pharmacologic treatment or percutaneous coronary interventions. While blood flow in the epicardial coronary vessel is restored downstream, effects remain largely unexplored; progressive injury at the microvessel level has significant repercussions on restoration of cardiocyte viability and the ventricular blood flow and contractile function relationship. This review focuses on the cardiac microcirculation and the fact that it should be a principle target of future studies to permit improvement of clinical outcomes in patients presenting with evolving myocardial infarction.

Population dynamics and orientation of the central Andean cushion Azorella compacta
Catherine Kleier,Tim Trenary,Eric A Graham,Philip W Rundel
PeerJ , 2015, DOI: 10.7287/peerj.preprints.607v1
Abstract: Azorella compacta (llareta; Apiaceae), a large woody cushion plant, is a remarkable species forming dense cushions and characterizing the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was found at 5250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr-1. Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20o from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant and recolonization of disturbed habitats.
Correlation between diabetes prevalence and subsequent cancer mortality in North Carolina counties  [PDF]
John G. Spangler, Julienne Kirk
Journal of Diabetes Mellitus (JDM) , 2014, DOI: 10.4236/jdm.2014.41001
Abstract:

Worldwide, over 250 million people live with diabetes mellitus, a disease which has been described as an epidemic. While much is known about the cardiovascular risks associated with this condition, its association with cancer has been less appreciated at the population level. This study assessed the relationship between colo-rectal, breast and prostate cancer mortality, and diabetes prevalence measured years earlier at the county level in the 100 counties of North Carolina. Methods: County level data were obtained from the 2000 US Census, the Centers for Disease Control and Prevention, and the North Carolina State Center for Health Statistics. The 2004 diabetes prevalence data by county and county level mortality from 2005 to 2009 for colorectal, breast and prostate cancer mortality were analyzed descriptively. Then multivariate linear regression was carried out to evaluate the contribution of pre-existing diabetes prevalence to cancer mortality, controlling county level covariates. Results: Average North Carolina county level prevalence of diabetes mellitus in 2004 (9%) was higher than the average prevalence of diabetes nationally in 2004 (7%). Mortality rates for breast, colorectal and prostate cancers at the county level were also higher than those nationally. In multivariate analysis, county level 2005-2009 total cancer mortality as well as mortality from colon and prostate cancers (but not breast cancer) correlated with county level 2004 diabetes prevalence rates. Diabetes mellitus prevalence in 2004 explained 31%, 34% and 42% of the variance of mortality from prostate, colorectal and total cancers. Conclusions: These findings support the relationship between diabetes mellitus and cancer at the population level. Direct and indirect costs of cancer care in North Carolina in 2004 were $5.57 billion. Because diabetes explained 42% of the variance of total county level cancer mortality, prevention and control of diabetes could save the state over $2 billion.

Export Promotion, Import Substitution and Economic Integration in Nigeria  [PDF]
Tunde G. Monogbe, O. John Okah
iBusiness (IB) , 2017, DOI: 10.4236/ib.2017.94010
Abstract:

This paper empirically integrates the interplay between import substitution and export promote on the Nigerian economy in conjunction with the theoretical position of the protectionist and the free trade activist and how this has helped in promoting the Nigerian economy over the years. A disaggregate analysis of importation and exportation is conducted using a time series data between the periods 1981 to 2016. Series of econometric estimation tools were adopted in this study. Findings reveal that Non-oil export and Non-oil import seems to significantly promote economic integration in Nigeria. This report further gave in a support to trade protectionist and the trade liberalize advocates. The result of the causality test shows that before any nation could attract foreign inflows, the economy must be in good form as foreign investor only invests in an economy whose receiving capacity can sustain their investment. The study therefore concludes that before any nation could embrace liberalization, there must have been a level of threshold of industrial development in such nation.

Air Manganese Levels and Chronic Liver Disease Mortality in North Carolina Counties: An Ecological Study
John G. Spangler
International Journal of Environmental Research and Public Health , 2012, DOI: 10.3390/ijerph9093258
Abstract: Manganese is an essential trace element which is toxic in high doses. Over the past several decades, manganese has replaced lead as the anti-knock agent in gasoline, raising concern about air and road-side contamination with this element. In addition, manganese is absorbed by the liver, making specific populations (e.g., pregnant women, infants and children, and patients with liver disease) susceptible to its toxic effects. Using data from the US Census Bureau, the North Carolina State Center for Health Statistics, and the US Environmental Protection Agency, this ecological study evaluated chronic liver disease mortality rates in North Carolina’s 100 counties. It correlated these rates with county-level demographics as well as on-road and non-road air borne manganese concentrations. Median income by county was inversely associated with chronic liver disease mortality, while the logarithmically transformed airborne concentrations of on-road manganese were positively correlated with county-level chronic liver disease mortality. Because environmental manganese near roads is likely to increase over time, these pilot findings potentially have regulatory implications and argue for further research.
Oxidative stress responses - what have genome-scale studies taught us?
John G Scandalios
Genome Biology , 2002, DOI: 10.1186/gb-2002-3-7-reviews1019
Abstract: Reactive oxygen species (ROS) such as superoxide (O2?-), hydrogen peroxide (H2O2), and the hydroxyl radical (OH?) are produced in all aerobic organisms within the cell and are normally in balance with antioxidant molecules. Oxidative stress occurs when this critical balance is disrupted because of depletion of antioxidants or excess accumulation of ROS (Figure 1).ROS were originally considered to be exclusively detrimental to cells, but it is now recognized that redox regulation involving ROS is key to the modulation of critical cellular functions (Figure 2) [1]. Regardless of how or where they are generated, an increase in intracellular oxidants results in two very important effects: damage to various cell components and activation of specific signaling pathways, both of which influence numerous cellular processes leading to proper cell functions or to cell death [1]. Mounting evidence links oxidants and oxidative stress to a variety of human diseases and aging [2], as well as to senescence, impaired photosynthesis, and necrosis in plants [1]. On the other hand, there are clear examples of how ROS are put to constructive uses, the most powerful being the crucial role that O2?- plays against invading microbes, by serving as a broad-spectrum antibiotic [3]. Plants also mount a broad-range response to invading pathogens by a rapid and transient production of ROS via the 'oxidative burst' [4]. This article considers a number of recent genome-wide analyses of the response to ROS in bacteria, yeasts and Arabidopsis in the light of previous knowledge about oxidative stress responses.When oxidative stress occurs, cells function to counteract the resulting oxidant effects and to restore the redox balance. All organisms have adaptive responses to oxidative stress, with antioxidant defense enzymes being induced by changes in the levels of H2O2 or O2?-, leading to the activation or silencing of genes encoding defensive enzymes, transcription factors and structural proteins [5]
Brachyplatystom a promagdalena, new species, a fossil goliath catfish (Siluriformes: Pimelodidae) from the Miocene of Colombia, South America
Lundberg, John G.;
Neotropical Ichthyology , 2005, DOI: 10.1590/S1679-62252005000400017
Abstract: a fossil weberian complex of a large pimelodid catfish from the middle miocene la venta fauna of central colombia originally identified as brachyplatystoma sp. is described as a new, extinct species. brachyplatystoma promagdalena, new species, is diagnosed by three autapomorphic characters: fifth centrum with a massive midventral expansion containing deep cavities and heavy ridges; first and compound centra contribute to a pair of prominent anterolateral processes before the ventral ends of the ossa suspensoria; and compound centrum with an anteriorly concave low ridge crossing its ventral surface posterior to aortic canal foramen. brachyplatystoma promagdalena is compared to modern congeneric species and placed in the subgenus malacobagrus with b. filamentosum, b. capapretum and b. rousseauxii. this group is characterized by synapomorphies of the texture and form of the first vertebra; texture and form of the dorsal side of the fourth transverse process; and presence of a bony gas bladder platform on the ventral side of the fourth transverse process. today brachyplatystoma ranges widely across the lowland orinoco and amazon and some river basins of the guianas. the genus does not occur west or north of the andes or venezuelan coastal ranges. the miocene species of brachyplatystoma signals the former large river and biotic connection between the paleo-amazonas-orinoco system and central colombia, a region now drained by the río magdalena. other fossils of aquatic vertebrates from the la venta fauna show this same biogeographic relationship.
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