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Search Results: 1 - 10 of 223132 matches for " Carl C Swisher III "
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Progress and Challenges Using 40Ar/39Ar Geochronology in Costa Rica and Nicaragua
Saginor1,Ian; Gazel,Esteban; Michael J,Carr; Swisher III,Carl C; Turrin,Brent;
Revista Geológica de América Central , 2011,
Abstract: to better estimate the extrusive flux of the central american arc, from 2002-2008, we obtained sixty one high precision 40ar/39ar ages on geographically well-situated lavas and tephra from costa rica and nicaragua. here, we describe a number of observations encountered during this study using four examples that well document the precision, accuracy and general reliability of the 40ar/39ar ages. first, low k2o values, particularly in samples from nicaragua, is a major limitation in or attempts to obtain reliable dates on samples under 1 my. second, extensive weathering of samples due to the tropical climate of central america has resulted in various levels of argon loss even when the hand sample appeared unaltered. third, our field and geochronological data lead us to conclude that eruptive rates have not been constant over the past 15 to 20 my, but rather appears punctuated by gaps of up to several million years. we attempted to address the temporal gaps in several ways. first, geochemical analyses were used to identify samples that may have erupted during time periods without known volcanism. for example, u/th values in the active central american arc are significantly higher than those obtained from the miocene coyol group except for four samples with intermediate values that were dated to determine if their ages were intermediate as well. however, all of these samples were found to be from a period with known volcanism. second, we sought to locate the oldest sections of the active arc and the youngest sections of the coyol group in order to better constrain the timing and duration of the apparent gap in volcanic productivity. this approach also failed to locate samples from periods without known volcanism. when these methods proved largely unsuccessful, our focus shifted to dating regions of minor volcanism between the active and coyol volcanic fronts as well as between cosigüina and san cristóbal, the longest stretch of the central american volcanic front withou
Progreso y retos de la geocronología 40Ar/39Ar en Costa Rica y Nicaragua Progress and Challenges Using 40Ar/39Ar Geochronology in Costa Rica and Nicaragua
Ian Saginor1,Esteban Gazel,Carr Michael J,Carl C Swisher III
Revista Geológica de América Central , 2011,
Abstract: Con el principal objetivo de realizar mejores cálculos de la producción volcánica, en el Arco Volcánico de América Central, realizamos 61 dataciones 40Ar/39Ar en tefras y lavas en localidades de frente volcánico de Costa Rica y Nicaragua por medio de varias campa as de campo y análisis de laboratorio (preparación de muestras, envió al reactor nuclear, espectroscopía de masas de las muestras radiactivas, al laboratorio de gases nobles del Departamento de Ciencias de la Tierra y Planetarias de la Universidad Rutgers) del 2002-2008. En este artículo presentamos diferentes observaciones que resultaron de este estudio donde se describe la precisión, exactitud y la confiabilidad de las edades 40Ar/39Ar. El primer resultado muestra las limitaciones de esta técnica en muestras baja en K2O con edades < 1 Ma, especialmente en Nicaragua. El segundo resultado muestra los efectos de la pérdida de Ar por los procesos de meteorización típicos del trópico, inclusive afectando las muestras sanas a nivel críptico. El tercer resultado sugiere que las razones eruptivas del frente volcánico no han sido constantes durante los últimos 15-20 Ma, sino más bien representan ciclos eruptivos. Con el propósito de evaluar los hitos entre diferentes ciclos eruptivos, evaluamos los datos geoquímicos a lo largo del frente volcánico, en especial las relaciones U/Th, cuyos valores son inferiores (Grupo Coyol) en Nicaragua, comparados con el frente volcánico activo. Sin embargo, las muestras seleccionadas con base en geoquímica, resultaron ser de edades conocidas y no produjeron datos que llenan los hiatos entre ciclos de actividad volcánica. La siguiente estrategia que manejamos fue extender el muestreo en el Grupo Coyol, inmediatamente detrás del frente volcánico activo, sin embargo, esta estrategia no fue exitosa para encontrar muestras que llenaran los hiatos de actividad. No obstante, obtuvimos edades de 1.1-3,6 Ma entre los volcanes Cosiguina and San Cristóbal, los cuales limitan el hiato de actividad y mejoran nuestra percepción de los ciclos de actividad volcánica en América Central. To better estimate the extrusive flux of the Central American Arc, from 2002-2008, we obtained sixty one high precision 40Ar/39Ar ages on geographically well-situated lavas and tephra from Costa Rica and Nicaragua. Here, we describe a number of observations encountered during this study using four examples that well document the precision, accuracy and general reliability of the 40Ar/39Ar ages. First, low K2O values, particularly in samples from Nicaragua, is a major limitation in or attempts to obtain
The Age of the 20 Meter Solo River Terrace, Java, Indonesia and the Survival of Homo erectus in Asia
Etty Indriati,Carl C. Swisher III,Christopher Lepre,Rhonda L. Quinn,Rusyad A. Suriyanto,Agus T. Hascaryo,Rainer Grün,Craig S. Feibel,Briana L. Pobiner,Maxime Aubert,Wendy Lees,Susan C. Antón
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021562
Abstract: Homo erectus was the first human lineage to disperse widely throughout the Old World, the only hominin in Asia through much of the Pleistocene, and was likely ancestral to H. sapiens. The demise of this taxon remains obscure because of uncertainties regarding the geological age of its youngest populations. In 1996, some of us co-published electron spin resonance (ESR) and uranium series (U-series) results indicating an age as young as 35–50 ka for the late H. erectus sites of Ngandong and Sambungmacan and the faunal site of Jigar (Indonesia). If correct, these ages favor an African origin for recent humans who would overlap with H. erectus in time and space. Here, we report 40Ar/39Ar incremental heating analyses and new ESR/U-series age estimates from the “20 m terrace" at Ngandong and Jigar. Both data sets are internally consistent and provide no evidence for reworking, yet they are inconsistent with one another. The 40Ar/39Ar analyses give an average age of 546±12 ka (sd±5 se) for both sites, the first reliable radiometric indications of a middle Pleistocene component for the terrace. Given the technical accuracy and consistency of the analyses, the argon ages represent either the actual age or the maximum age for the terrace and are significantly older than previous estimates. Most of the ESR/U-series results are older as well, but the oldest that meets all modeling criteria is 143 ka+20/?17. Most samples indicated leaching of uranium and likely represent either the actual or the minimum age of the terrace. Given known sources of error, the U-series results could be consistent with a middle Pleistocene age. However, the ESR and 40Ar/39Ar ages preclude one another. Regardless, the age of the sites and hominins is at least bracketed between these estimates and is older than currently accepted.
40Ar/39Ar dating of the lower Yixian FM, Liaoning Province, Northeastern China
Carl C. Swisher,Wang Yuanqing,Wang Xiaolin,Xu Xing,Wang Yuan
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891590
Abstract:
An Efficiency Wage—Imperfect Information Model of the Phillips Curve  [PDF]
Carl M. Campbell III
Open Journal of Social Sciences (JSS) , 2017, DOI: 10.4236/jss.2017.52004
Abstract: This study develops an efficiency wage model in which workers have imperfect information about wages elsewhere. Firms’ profit-maximizing behavior results in a Phillips curve relationship. Three types of Phillips curves are derived: a wage-wage Phillips curve, a wage-price Phillips curve, and a price-price Phillips curve. The wage-wage Phillips curve is a reduced form relationship with the coefficient on lagged wage inflation equaling 1. To obtain the wage-price and the price-price Phillips curves, stochastic shocks to the growth rate of demand are modeled, yielding expressions over time for wage inflation, price inflation, and unemployment. These expressions are used in a regression of current wage or price inflation on unemployment and lagged price inflation, and it is demonstrated that the coefficient on lagged inflation asymptotically approaches 1. In addition, the model predicts that real wages are strictly procyclical in response to technology shocks, but can be either procyclical, acyclical, or countercyclical in response to demand shocks. Thus, this study can explain why economists have reached different conclusions about the cyclical behavior of real wages.
Further support for a Cretaceous age for the feathered-dinosaur beds of Liaoning, China: New 40Ar/39Ar dating of the Yixian and Tuchengzi

C C Swisher III,WANG Xiaolin,ZHOU Zhonghe,WANG Yuanqing,JIN Fan,ZHANG Jiangyong,XU Xing,ZHANG Fucheng,WANG Yuan,

科学通报(英文版) , 2002,
Abstract: We report new 40Ar/39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar/39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar/39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca/K ratios, excellent reproducibility and gave a mean age of 125.0 ± 0.18 (1SD) ± 0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar/39Ar analyses of the Hengdaozi tuff gave a mean age of 125.0 ± 0.19 (1SD) ± 0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4 ± 0.19 (1SD) ± 0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.
New Orleans: The Long-Term Demographic Trends
Carl L. Bankston III
Sociation Today , 2010,
Abstract: The City of New Orleans is frequently portrayed as an urban center that underwent great changes following the damage wrought by Hurricane Katrina in 2005, and much of the attention given to the city has dealt with its revival and reconstruction following the storm. But what has been ignored has been the long-term decline in the population of New Orleans. If this view is taken, New Orleans is currently about where the population would have been expected to be even without Hurricane Katrina's damages to the community.
Evaluation of alternative methods for estimating reference evapotranspiration  [PDF]
Daniel K. Fisher, H. C. Pringle III
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.48A008
Abstract:

Evapotranspiration is an important component in water-balance and irrigation scheduling models. While the FAO-56 Penman-Monteith method has become the de facto standard for estimating reference evapotranspiration (ETo), it is a complex method requiring several weather parameters. Required weather data are oftentimes unavailable, and alternative methods must be used. Three alternative ETo methods, the FAO-56 Reduced Set, Hargreaves, and Turc methods, were evaluated for use in Mississippi, a humid region of the USA, using only measurements of air temperature. The Turc equation, developed for use with measured temperature and solar radiation, was tested with estimated radiation and found to provide better estimates of FAO-56 ETo than the other methods. Mean bias errors of 0.75, 0.28, and -0.19 mm, mean absolute errors of 0.92, 0.68, and 0.62 mm, and percent errors of 22.5%, 8.5%, and -5.7% were found for daily estimates for the FAO-56 Reduced Set, Hargreaves, and Turc methods, respectively.

On the supercongruence conjectures of van Hamme
Holly Swisher
Mathematics , 2015,
Abstract: In 1997, van Hamme developed $p-$adic analogs, for primes $p$, of several series which relate hypergeometric series to values of the gamma function, originally studied by Ramanujan. These analogs relate truncated sums of hypergeometric series to values of the $p-$adic gamma function, and are called Ramanujan type supercongruences. In all, van Hamme conjectured 13 such formulas, three of which were proved by van Hamme himself, and five others have been proved recently using a wide range of methods. Here, we explore four of the remaining five van Hamme supercongruences, revisit some of the proved ones, and provide some extensions.
HALO: Report and Predicted Response Times
Matthew Swisher
Computer Science , 2015,
Abstract: HALO: Heterogeneity-Aware Load Balancing is a paper that proposes a class of heterogeneity-aware Load Balancers (LBs) for cluster systems. LBs that are heterogeneity-aware are able to detect when servers differ in speeds and in number of cores. Response times for heterogeneous systems are calculated and presented.
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