Global Health Studies Based on Local Realities     

Pat Butler 《Global Change & Human Health》2001,2(2):150-152

A major new programme launched by the US Bureau of Educational and Cultural Affairs and the Council forInternational Exchange of Scholars will examine the "Challenges of Health in a Borderless World". The Fulbright New Century Scholars (NCS)Program is intended to build on the strengths of the traditional Fulbright ScholarProgram, which sponsors individual researchers to spend some time working in a country other than their own. The new programme aims to extend the idea of individual exchange, to provide a forum for international, interdiscipli-nary collaboration among groups of researchers.In choosing health as the subject for the first such collaboration, the Program recognises the key significance of the topic to developed and developing countries alike, as well as theneed for a coordinated global response to many of the health problems facing the world today.  相似文献   

New Insights from Well Responses to Fluctuations in Barometric Pressure     

J.J. Butler Jr.  W. Jin  G.A. Mohammed  E.C. Reboulet 《Ground water》2011,49(4):525-533

Hydrologists have long recognized that changes in barometric pressure can produce changes in water levels in wells. The barometric response function (BRF) has proven to be an effective means to characterize this relationship; we show here how it can also be utilized to glean valuable insights into semi‐confined aquifer systems. The form of the BRF indicates the degree of aquifer confinement, while a comparison of BRFs between wells sheds light on hydrostratigraphic continuity. A new approach for estimating hydraulic properties of aquitards from BRFs has been developed and verified. The BRF is not an invariant characteristic of a well; in unconfined or semi‐confined aquifers, it can change with conditions in the vadose zone. Field data from a long‐term research site demonstrate the hydrostratigraphic insights that can be gained from monitoring water levels and barometric pressure. Such insights should be of value for a wide range of practical applications.  相似文献   

Precious metal enrichment in the Platreef,Bushveld Complex,South Africa: evidence from homogenized magmatic sulfide melt inclusions     

D. A. Holwell  I. McDonald  I. B. Butler 《Contributions to Mineralogy and Petrology》2011,161(6):1011-1026

Magmatic sulfide deposits are the most significant source of platinum-group elements (PGE) in the world. Key to understanding their genesis is determining the processes and timing of sulfide saturation, metal enrichment and crustal contamination. In this study, we have identified droplets of magmatic sulfide from the Platreef, South Africa, where droplets of sulfide have been trapped in the earliest crystallising phase, chromite. Due to their early entrapment at high temperatures, metal concentrations and ratios that they display are indicative of a very early-stage sulfide liquid in the system, as they will have cooled and fractionated within an essentially closed system, unlike interstitial blebs that crystallise in an open system as the magma cools. Analysis of these droplets in an opaque mineral like chromite by LA-ICP-MS is problematic as some of the fractionated inclusion is necessarily lost during cutting and polishing to initially identify the inclusion. This particularly affects the ability to representatively sample the most fractionated phases such as gold and platinum minerals. Here, using a novel technique whereby the inclusions are homogenized and quickly quenched, so that any cutting, polishing and subsequent LA-ICP-MS analysis samples a truly representative portion of the droplet. This has been used to show that early sulfide liquids in the Platreef were highly PGE-rich and had Pt/Pd ratios of close to unity that supports genetic models invoking sulfide saturation and metal enrichment prior to intrusion, with pre-enriched sulfides entrained within the Platreef magma.  相似文献   

Mercury in the Southern Ocean     

Daniel Cossa  Lars-Eric Heimbürger  Stephen R. Rintoul  Edward C.V. Butler  Andrew R. Bowie  Roslyn J. Watson 《Geochimica et cosmochimica acta》2011,75(14):4037-4052

We present here the first mercury speciation study in the water column of the Southern Ocean, using a high-resolution south-to-north section (27 stations from 65.50°S to 44.00°S) with up to 15 depths (0-4440 m) between Antarctica and Tasmania (Australia) along the 140°E meridian. In addition, in order to explore the role of sea ice in Hg cycling, a study of mercury speciation in the “snow-sea ice-seawater” continuum was conducted at a coastal site, near the Australian Casey station (66.40°S; 101.14°E). In the open ocean waters, total Hg (Hg_T) concentrations varied from 0.63 to 2.76 pmol L⁻¹ with “transient-type” vertical profiles and a latitudinal distribution suggesting an atmospheric mercury source south of the Southern Polar Front (SPF) and a surface removal north of the Subantartic Front (SAF). Slightly higher mean Hg_T concentrations (1.35 ± 0.39 pmol L⁻¹) were measured in Antarctic Bottom Water (AABW) compared to Antarctic Intermediate water (AAIW) (1.15 ± 0.22 pmol L⁻¹). Labile Hg (Hg_R) concentrations varied from 0.01 to 2.28 pmol L⁻¹, with a distribution showing that the Hg_T enrichment south of the SPF consisted mainly of Hg_R (67 ± 23%), whereas, in contrast, the percentage was half that in surface waters north of PFZ (33 ± 23%). Methylated mercury species (MeHg_T) concentrations ranged from 0.02 to 0.86 pmol L⁻¹. All vertical MeHg_T profiles exhibited roughly the same pattern, with low concentrations observed in the surface layer and increasing concentrations with depth up to an intermediate depth maximum. As for Hg_T, low mean MeHg_T concentrations were associated with AAIW, and higher ones with AABW. The maximum of MeHg_T concentration at each station was systematically observed within the oxygen minimum zone, with a statistically significant MeHg_Tvs Apparent Oxygen Utilization (AOU) relationship (p < 0.001). The proportion of Hg_T as methylated species was lower than 5% in the surface waters, around 50% in deep waters below 1000 m, reaching a maximum of 78% south of the SPF. At Casey coastal station Hg_T and Hg_R concentrations found in the “snow-sea ice-seawater” continuum were one order of magnitude higher than those measured in open ocean waters. The distribution of Hg_T there suggests an atmospheric Hg deposition with snow and a fractionation process during sea ice formation, which excludes Hg from the ice with a parallel Hg enrichment of brine, probably concurring with the Hg enrichment of AABW observed in the open ocean waters. Contrastingly, MeHg_T concentrations in the sea ice environment were in the same range as in the open ocean waters, remaining below 0.45 pmol L⁻¹. The MeHg_T vertical profile through the continuum suggests different sources, including atmosphere, seawater and methylation in basal ice. Whereas Hg_T concentrations in the water samples collected between the Antarctic continent and Tasmania are comparable to recent measurements made in the other parts of the World Ocean (e.g., Soerensen et al., 2010), the Hg species distribution suggests distinct features in the Southern Ocean Hg cycle: (i) a net atmospheric Hg deposition on surface water near the ice edge, (ii) the Hg enrichment in brine during sea ice formation, and (iii) a net methylation of Hg south of the SPF.  相似文献   

CFSv2 ensemble prediction of the wintertime Arctic Oscillation     

Emily E. Riddle  Amy H. Butler  Jason C. Furtado  Judah L. Cohen  Arun Kumar 《Climate Dynamics》2013,41(3-4):1099-1116

Lagged ensembles from the operational Climate Forecast System version 2 (CFSv2) seasonal hindcast dataset are used to assess skill in forecasting interannual variability of the December–February Arctic Oscillation (AO). We find that a small but statistically significant portion of the interannual variance (>20 %) of the wintertime AO can be predicted at leads up to 2 months using lagged ensemble averages. As far as we are aware, this is the first study to demonstrate that an operational model has discernible skill in predicting AO variability on seasonal timescales. We find that the CFS forecast skill is slightly higher when a weighted ensemble is used that rewards forecast runs with the most accurate representations of October Eurasian snow cover extent (SCE), hinting that a stratospheric pathway linking October Eurasian SCE with the AO may be responsible for the model skill. However, further analysis reveals that the CFS is unable to capture many important aspects of this stratospheric mechanism. Model deficiencies identified include: (1) the CFS significantly underestimates the observed variance in October Eurasian SCE, (2) the CFS fails to translate surface pressure anomalies associated with SCE anomalies into vertically propagating waves, and (3) stratospheric AO patterns in the CFS fail to propagate downward through the tropopause to the surface. Thus, alternate boundary forcings are likely contributing to model skill. Improving model deficiencies identified in this study may lead to even more skillful predictions of wintertime AO variability in future versions of the CFS.  相似文献   

Tree-Ring Analysis And Natural Hazard Chronologies: Minimum Sample Sizes And Index Values*     

David R. Butler  George P. Malanson  Jack G. Oelfke 《The Professional geographer》1987,39(1):41-47

Tree-ring dating is employed to reconstruct chronologies of occurrence for a variety of natural hazards. The number of trees sampled varies greatly as does the minimum number of tree-ring responses. The number of trees to be sampled and an acceptable tree-ring response index should be dictated by the nature and geographical extent of the specific hazard under study. Repetitive sampling of different numbers of 30 avalanche-damaged trees showed significant differences in number of tree-ring responses over a 55-year-period. More sampling and use of a higher minimum response index allowed greater confidence in the chronology constructed from tree-rings and compared to historical records. Three geographic scales of analysis that can confound tree-ring responses are identified, and three guidelines for choosing sample size, given variations in processes, are suggested.  相似文献   

Processes affecting transfer of sediment and colloids,with associated phosphorus,from intensively farmed grasslands: an overview of key issues     

P. M. Haygarth  G. S. Bilotta  R. Bol  R. E. Brazier  P. J. Butler  J. Freer  L. J. Gimbert  S. J. Granger  T. Krueger  C. J. A. Macleod  P. Naden  G. Old  J. N. Quinton  B. Smith  P. Worsfold 《水文研究》2006,20(20):4407-4413

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On the effects of a sudden change in the albedo of the Earth     

Elizabeth J. Butler  Fred Hoyle 《Astrophysics and Space Science》1979,60(2):505-511

Acquisition by the upper atmosphere of some 10¹⁴ gm of cometary dust would have major implications on the Earth's climate. Pluvial activity would increase dramatically as temperature differences between sea and land widened. Global distribution of precipitation would be controlled by the density of the dust in the atmosphere; for a partially reflective blanket, a fraction of solar energy would still reach ground level creating new climatic zones. The totally undecomposed state of the interiors of Siberian Mammoths and the curious distribution, often uphill, of erratic boulders point to unbelievably sudden and severe conditions at the onset and possibly end of a glacial period. We suggest that a reflective blanket of particles could produce such conditions.  相似文献   

Visual bias in R-mode dendrograms due to the effect of closure     

John C. Butler 《Mathematical Geology》1978,10(2):243-252

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Imagery Scale and Type for Natural Hazards Analysis: Classroom Examples Using Forest Fires and Snow Avalanches     

David R. Butler  Hilary J.M. Sandford 《国际地球制图》2013,28(1):73-78

Abstract

The type of remotely sensed imagery best suited for natural hazards analysis is largely dependent on the geographic size and discreteness of the hazard in question. Some forms of imagery that are appropriate for analyses of spatially fixed, relatively fine‐scale hazards are inappropriate for use with geographically widespread and transient hazards, and vice versa. In this paper we utilize one study area, Waterton‐Glacier International Peace Park (Canada and USA), and two natural hazard types (snow avalanches and forest fires), to illustrate how these remote sensing principles can be presented to students of natural hazards. We also address the issue of familiarity, or lack thereof, that students have with different images from a variety of platforms.  相似文献