Networking   总被引：1，自引：1，他引：0  

Susan Hanson 《The Professional geographer》2000,52(4):751-758

This essay outlines the ways that networks structure opportunities foremployment and advancement and the ways that networks build frameworks of support, particularly for women in geography. I consider the evidence supporting the contention that personal contacts and social networks affect careeroutcomes. I then note that each person's networks are likely to be biased in favor of others who share common interests and concerns. In particular, gender affects network composition in significant ways. Because network composition affects how a network functions, it is worth considering the personal and professional advantages of building diverse networks. In the final section I suggest ways to build such networks.  相似文献   

Contrasting changes between the northern and southern Gulf of St. Lawrence ecosystems associated with the collapse of groundfish stocks     

Lyne Morissette  Martin Castonguay  Claude Savenkoff  Douglas P. Swain  Denis Chabot  Hugo Bourdages  Mike O. Hammill  J. Mark Hanson 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):2117

In order to have a global view of ecosystem changes associated with the collapse of groundfish species in the Gulf of St. Lawrence during the early 1990s, Ecopath mass-balance models were constructed incorporating uncertainty in the input data. These models covered two ecosystems (northern and southern Gulf of St. Lawrence; NAFO divisions 4RS and 4T), and two time periods (before the collapse, in the mid-1980s, and after it, in the mid-1990s). Our analyses revealed that the ecosystem structure shifted dramatically from one previously dominated by piscivorous groundfish and small-bodied forage species during the mid-1980s to one now dominated only by small-bodied pelagic species during the mid-1990s in both southern and northern Gulf. The species structure in the northern Gulf versus southern Gulf was different, which may explain why these two ecosystems did not recover the same way from the collapse in the early 1990s. Productivity declined in the northern Gulf after the collapse but increased in the southern Gulf. The collapse of groundfish stocks resulted in declines in the mean trophic level of the landings in both the northern and the southern Gulf. Even though fishing mortality was then intentionally reduced, this part of the total mortality was taken up by predation. The temporal changes in the internal structure of both ecosystems are reflected in their overall emergent properties.  相似文献   

Calculation of beach change under interacting cross-shore and longshore processes     

Hans Hanson  Magnus Larson  Nicholas C. Kraus 《Coastal Engineering》2010

This paper presents a mathematical approach and numerical model that simulates beach and dune change in response to cross-shore processes of dune growth by wind and dune erosion by storms, and by gradients in longshore sand transport that will alter shoreline position. Sub-aerial transport processes are represented, whereas sub-aqueous transport is neglected. The system is tightly coupled morphologically, with the berm playing a central role. For example, the potential for sand to be transported to the dune by wind depends on berm width, and sand lost in erosion of the dune during storms can widen the berm. Morphologic equilibrium considerations are introduced to improve reliability of predictions and stability of the non-linear model. An analytical solution is given under simplification to illustrate properties of the model. Sensitivity tests with the numerical solution of the coupled equations demonstrate model performance, with one test exploring beach and dune response to potential increase in storm-wave height with global warming. Finally, the numerical model is applied to examine the consequences of groin shortening at Westhampton Beach, Long Island, New York, as an alternative for providing a sand supply to the down-drift beach. Results indicate that the sand will be released over several decades as the shoreline and dune move landward in adjustment to the new equilibrium condition with the shortened groins.  相似文献   

Resonant Absorption as Mode Conversion? II. Temporal Ray Bundle     

Chris S. Hanson  Paul S. Cally 《Solar physics》2011,269(1):105-110

A fast-wave pulse in a simple, cold, inhomogeneous MHD model plasma is constructed by Fourier superposition over frequency of harmonic waves that are singular at their respective Alfvén resonances. The pulse partially reflects before reaching the resonance layer, but also partially tunnels through to it to convert to an Alfvén wave. The exact absorption/conversion coefficient for the pulse is shown to be given precisely by a function of transverse wavenumber tabulated in Paper I of this sequence, and to be independent of frequency and pulse width.  相似文献   

Lichenometric Dating of Rock Surfaces in the Northern Cascade Range,USA     

Michael A. O'Neal  Nicholas T. Legg  Brian Hanson  Daniel J. Morgan  Allison Rothgeb 《Geografiska Annaler: Series A, Physical Geography》2013,95(3):241-248

This study presents a growth curve developed from direct and indirect growth rates of Rhizocarpon geographicum lichens from study sites on Mounts Baker, Rainier, Adams, and Hood in the northern Cascade Range of the western USA. Our observations of direct growth rates are based on 31 measurements of 11 lichens growing on different surfaces. This direct growth rate dataset is complemented by indirect growth rates based on measurements of the largest lichen observed on 20 different surfaces over 24–33‐yr periods. The direct and indirect datasets produce statistically indistinguishable mean radial growth rates of 0.48 and 0.50 mm yr^?1, respectively. Statistical analysis of zero and first order fits of our growth rate data suggests that lichen growth is best characterized by the average of our mean growth rate (zero order) models at 0.49 mm yr^?1. Our revised growth curve for the study area extends the applicable range for dating rock surface in the study area to the seventeenth century, approximately 175 years longer than previous calibrated curves.  相似文献   

Implications of sea-level rise and extreme events around Europe: a review of coastal energy infrastructure   总被引：1，自引：0，他引：1  

Sally Brown  Susan Hanson  Robert J. Nicholls 《Climatic change》2014,122(1-2):81-95

Sea-level rise and extreme events have the potential to significantly impact coastal energy infrastructure through flooding and erosion. Disruptions to supply, transportation and storage of energy have global ramifications and potential contamination of the natural environment. On a European scale, there is limited information about energy facilities and their strategic plans for adapting to climate change. Using a Geographical Information System this paper assesses coastal energy infrastructure, comprising (1) oil/gas/LNG/tanker terminals and (2) nuclear power stations. It discusses planning and adaptation for sea-level rise and extreme events. Results indicate 158 major oil/gas/LNG/tanker terminals in the European coastal zone, with 40 % located on the North Sea coast. There are 71 operating nuclear reactors on the coast (37 % of the total of European coastal countries), with further locations planned in the Black, Mediterranean and Baltic Seas. The UK has three times more coastal energy facilities than any other country. Many north-west European countries who have a high reliance on coastal energy infrastructure have a high awareness of sea-level rise and plan for future change. With long design lives of energy facilities, anticipating short, medium and long-term environmental and climatic change is crucial in the design, future monitoring and maintenance of facilities. Adaptation of coastal infrastructure is of international importance, so will be an ongoing important issue throughout the 21^st century.  相似文献   

Fish assemblages in a north Atlantic coastal ecosystem: Spatial patterns and environmental correlates     

S.H. Bosman  D.A. Methven  S.C. Courtenay  J.M. Hanson 《Estuarine, Coastal and Shelf Science》2011

Analyses of six years of bottom trawl data collected from Northumberland Strait, southern Gulf of St. Lawrence revealed four major fish assemblages, two of which occurred in the same two geographic areas each year. One of the two persistent assemblages occurred in deeper water off northwestern Prince Edward Island and consisted mostly of demersal fishes. The other persistent assemblage contained a mixture of demersal and pelagic fishes and occurred primarily in shallow water of central Northumberland Strait. Analyses of abiotic (depth, bottom temperature, substratum type) and biotic (presence of American lobster Homarus americanus, northern lady crab Ovalipes ocellatus) factors revealed bottom temperature and catches of lady crab correlate best with the fish assemblage structure each year, but correlation values were low (ρ_w ≤ 0.48). Combinations of all abiotic and biotic variables only marginally improved the strength of the correlations in four of six years (2002, 2003, 2005, 2006). Changes observed in the Northumberland Strait ecosystem over the six years included an increase in the ratio of pelagic to demersal fishes, disappearance of one of the four assemblages, and increased spatial overlap between the two persistent assemblages, which coincided with an increase in bottom temperature. The increasing importance of pelagic fishes, relative to demersal fishes, suggests a shift in food web structure may be occurring in Northumberland Strait.  相似文献   

A New Sigmoid Catalog from Hinode and the Solar Dynamics Observatory: Statistical Properties and Evolutionary Histories     

A. S. Savcheva  S. C. McKillop  P. I. McCauley  E. M. Hanson  E. E. DeLuca 《Solar physics》2014,289(9):3297-3311

We present a new sigmoid catalog covering the duration of the Hinode mission and the Solar Dynamics Observatory (SDO) until the end of 2012. The catalog consists of 72 mostly long-lasting sigmoids. We collect and make available all X-ray and EUV data from Hinode, SDO, and the Solar TErrestrial RElations Observatory (STEREO), and we determine the sigmoid lifetimes, sizes, and aspect ratios. We also collect the line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) for SDO or the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) to measure flux versus time for the lifetime of each region. We determine that the development of a sigmoidal shape and eruptive activity is more strongly correlated with flux cancelation than with emergence. We find that the eruptive properties of the regions correlate well with the maximum flux, largest change, and net change in flux in the regions. These results have implications for constraining future flux-rope models of ARs and gaining insight into their evolutionary properties.  相似文献   

The Distribution and Redox Chemistry of Iron in the Pettaquamscutt Estuary     

D.W. O’Sullivan  A.K. Hanson  Jr  D.R. Kester 《Estuarine, Coastal and Shelf Science》1997,45(6):769-788

A series of high resolution (10 cm) vertical profiles of iron were determined across the oxic/anoxic boundary in the Lower Pond of the Pettaquamscutt Estuary. Selective chemical treatments and multiple analytical methods were used to detemine the oxidation state and lability of iron across the oxic/anoxic boundary. The vertical distributions of dissolved and total iron were determined by atomic absorption spectroscopy, and dissolved Fe(II) and reducible iron were determined using a modified Ferrozine spectrophotometric method. Well-developed maxima of total dissolved iron ≈7·5 μM occurred within the oxic/anoxic transition zone. Analysis of Fe(II) by the FZ method indicates that more than 95% of the dissolved iron determined by atomic absorption spectroscopy within the maximum is in the form of Fe(II). The concentration of dissolved Fe(II) ranged from <4 nM in oxygenated surface waters to between 7 and 8 μM at the total dissolved iron maximum.Both dissolved and total iron samples were treated with ascorbic acid to quantify the fraction of iron that was reducible in this system. Dissolved iron is quantitatively reduced to Fe(II) by 3·5 m depth, and particulate iron was almost completely dissolved by 6 m. Thermodynamic speciation calculations indicate that the dominant species of Fe(II) in the anoxic waters is the Fe(HS)⁺complex. In addition, the concentration of Fe(II) in the anoxic zone appears to be controlled by precipitation of a sulfide phase, the ion activity product for waters below 7 m is in good agreement with the solubility product of mackinawite.The vertical distribution of oxidation states of the metals indicates non-equilibrium conditions due to microbiological and chemical processes occurring in the redox transition zone. A one-dimensional vertical, eddy diffusion model is presented that incorporates redox reactions of iron, sulfide and oxygen. The modeling suggests the maximum in Fe(II) can be achieved through inorganic oxidation and reduction reactions, however the depth at which the maximum occurs is sensitive to sulfide oxidation, which appears to be dominated by biological oxidation. The magnitude of the Fe(II) maximum depends on the flux of iron into the basin, and reductive dissolution of particulate iron.  相似文献   

Effects of age, sex and reproductive status on persistent organic pollutant concentrations in “Southern Resident” killer whales     

Margaret M. Krahn  M. Bradley Hanson  Candice K. Emmons  Jennie L. Bolton  Gina M. Ylitalo 《Marine pollution bulletin》2009,58(10):1522-10202

“Southern Resident” killer whales (Orcinus orca) that comprise three fish-eating “pods” (J, K and L) were listed as “endangered” in the US and Canada following a 20% population decline between 1996 and 2001. Blubber biopsy samples from Southern Resident juveniles had statistically higher concentrations of certain persistent organic pollutants than were found for adults. Most Southern Resident killer whales, including the four juveniles, exceeded the health-effects threshold for total PCBs in marine mammal blubber. Maternal transfer of contaminants to the juveniles during rapid development of their biological systems may put these young whales at greater risk than adults for adverse health effects (e.g., immune and endocrine system dysfunction). Pollutant ratios and field observations established that two of the pods (K- and L-pod) travel to California to forage. Nitrogen stable isotope values, supported by field observations, indicated possible changes in the diet of L-pod over the last decade.  相似文献