Are oranges the only fruit? A comment on the 2004 Ukrainian presidential election     

Adam Swain 《Geoforum》2005,36(6):141-687

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Palaeolimnology of Lake Zeribar, Iran, and its climatic implications     

Krystyna Wasylikowa  Andrzej Witkowski  Adam Walanus  Andrzej Hutorowicz  Stefan W. Alexandrowicz  Jerzy J. Langer 《Quaternary Research》2006,66(3):477-493

Lake Zeribar sediments covering the time period of the last 25,000 years were examined for the contents of seeds, fruits, Characeae, diatoms, and molluscs. Reconstructions of the variations in the lake water level, salinity, and trophy suggest a sequence of climatic changes. Three pronounced stages of low and varying lake-water level occurred ca. 17,700–15,400, 12,600–12,000, and 10,000–6000 cal yr BP. Some water-level changes were correlated with variations in salinity. The most pronounced increase of salinity occurred 17,700–15,700 and 12,600–12,000 cal yr BP, and less distinct ones occurred about 6400–5900 and 2500 cal yr BP. Diatom assemblages indicated a strong increase of lake trophy ca. 20,200 cal yr BP. Between 6000 and 5000 cal yr BP diatoms characteristic of eutrophy increased in core 63J, and at about 3200 cal yr BP a distinct increase in mesotrophic forms occurred in core 70B. The changes in the occurrence of various organisms indicate increased temperatures about 21,000 cal yr BP, between 15,400 and 12,600, about 12,000, and about 11,700 cal yr BP. The reduced occurrence or disappearance of some of them suggest temperature decreases about 17,700–15,400 and 12,600–12,000 cal yr BP.  相似文献   

GIMA ground penetrating radar system for monitoring concrete bridge decks     

Dryver Huston  Jing Qiong Hu  Kenneth Maser  William Weedon  Chris Adam 《Journal of Applied Geophysics》2000,43(2-4)

Ground Penetrating Radar (GPR) has been investigated as a non-destructive method for evaluating damage in concrete structures. However, the commercially available techniques are limited to detection of gross quantities of deterioration, due to the limited resolution of the system. The objective of this research is to evaluate a ground penetrating radar system with a novel Good Impedance Match Antenna (GIMA) for concrete structural assessment. This system has the capacity to detect concrete cracks as small as 1 mm thick, while being able to reflect from and detect features at depths of up to 360 mm. Laboratory results of testing of the GIMA antenna by using a step-frequency and a high-frequency impulse system are presented. The experimental results reveal that the GIMA antenna is capable for use in frequency ranges, at least as broad as 500 Mhz to 6 GHz for the step-frequency and 1 to 16 GHz for the high-frequency impulse system.  相似文献   

Dimensionless cosmology     

Ali Narimani  Adam Moss  Douglas Scott 《Astrophysics and Space Science》2012,341(2):617-629

Although it is well known that any consideration of the variations of fundamental constants should be restricted to their dimensionless combinations, the literature on variations of the gravitational constant G is entirely dimensionfull. To illustrate applications of this to cosmology, we explicitly give a dimensionless version of the parameters of the standard cosmological model, and describe the physics of both Big Bang Nucleosynthesis and recombination in a dimensionless manner. Rigorously determining how to talk about the model in a way which avoids physical dimensions is a requirement for proceeding with a calculation to constrain time-varying fundamental constants. The issue that appears to have been missed in many studies is that in cosmology the strength of gravity is bound up in the cosmological equations, and the epoch at which we live is a crucial part of the model. We argue that it is useful to consider the hypothetical situation of communicating with another civilization (with entirely different units), comparing only dimensionless constants, in order to decide if we live in a Universe governed by precisely the same physical laws. In this thought experiment, we would also have to compare epochs, which can be defined by giving the value of any one of the evolving cosmological parameters. By setting things up carefully in this way one can avoid inconsistent results when considering variable constants, caused by effectively fixing more than one parameter today. We show examples of this effect by considering microwave background anisotropies, being careful to maintain dimensionlessness throughout. We present Fisher matrix calculations to estimate how well the fine structure constants for electromagnetism and gravity can be determined with future microwave background experiments. We highlight how one can be misled by simply adding G to the usual cosmological parameter set.  相似文献   

Aerogel tracks made by impacts of glycine: Implications for formation of bulbous tracks in aerogel and the Stardust mission     

Adam NIXON  Mark J. BURCHELL  Mark C. PRICE  Anton T. KEARSLEY  Steven JONES 《Meteoritics & planetary science》2012,47(4):623-633

Abstract– Impacts of small particles of soda‐lime glass and glycine onto low density aerogel are reported. The aerogel had a quality similar to the flight aerogels carried by the NASA Stardust mission that collected cometary dust during a flyby of comet 81P/Wild 2 in 2004. The types of track formed in the aerogel by the impacts of the soda‐lime glass and glycine are shown to be different, both qualitatively and quantitatively. For example, the soda‐lime glass tracks have a carrot‐like appearance and are relatively long and slender (width to length ratio <0.11), whereas the glycine tracks consist of bulbous cavities (width to length ratio >0.26). In consequence, the glycine particles would be underestimated in diameter by a factor of 1.7–3.2, if the glycine tracks were analyzed using the soda‐lime glass calibration and density. This implies that a single calibration for impacting particle size based on track properties, as previously used by Stardust to obtain cometary dust particle size, is inappropriate.  相似文献   

Detecting communities with the multi-scale Louvain method: robustness test on the metropolitan area of Brussels     

Arnaud Adam  Jean-Charles Delvenne  Isabelle Thomas 《Journal of Geographical Systems》2018,20(4):363-386

Detecting communities in large networks has become a common practice in socio-spatial analyses and has led to the development of numerous dedicated mathematical algorithms. Nowadays, however, researchers face a deluge of data and algorithms, and great care must be taken regarding methodological questions such as the values of the parameters and the geographical characteristics of the data. We aim here at testing the sensitivity of multi-scale modularity optimized by the Louvain method to the value of the resolution parameter (introduced by Reichardt and Bornholdt (Phys Rev Lett 93(21):218701, 2004.  https://doi.org/10.1103/PhysRevLett.93.218701) and controlling the size of the communities) and to a number of spatial issues such as the inclusion of internal loops and the delineation of the study area. We compare the community structures with those found by another well-known community detection algorithm (Infomap), and we further interpret the final results in terms of urban geography. Sensitivity analyses are conducted for commuting movements in and around Brussels. Results reveal slight effects of spatial issues (inclusion of the internal loops, definition of the study area) on the partition into job basins, while the resolution parameter plays a major role in the final results and their interpretation in terms of urban geography. Community detection methods seem to reveal a surprisingly strong spatial effect of commuting patterns: Similar partitions are obtained with different methods. This paper highlights the advantages and sensitivities of the multi-scale Louvain method and more particularly of defining communities of places. Despite these sensitivities, the method proves to be a valuable tool for geographers and planners.  相似文献   

Field spectroradiometer and simulated multispectral bands for discriminating invasive species from morphologically similar cohabitant plants     

Solomon G. Tesfamichael  Solomon W. Newete  Elhadi Adam  Bambo Dubula 《地理信息系统科学与遥感》2018,55(3):417-436

One of the challenges in fighting plant invasions is the inefficiency of identifying their distribution using field inventory techniques. Remote sensing has the potential to alleviate this problem effectively using spectral profiling for species discrimination. However, little is known about the capability of remote sensing in discriminating between shrubby invasive plants with narrow leaf structures and other cohabitants with similar ecological niche. The aims of this study were therefore to (1) assess the classification performance of field spectroradiometer data among three bushy and shruby plants (Artemesia afra, Asparagus laricinus, and Seriphium plumosum) from the coexistent plant species largely dominated by acacia and grass species, and (2) explore the performance of simulated spectral bands of five space-borne images (Landsat 8, Sentinel 2A, SPOT 6, Pleiades 1B, and WorldView-3). Two machine-learning classifiers (boosted trees classification and support vector machines) were used to classify raw hyperspectral (n = 688) and simulated multispectral wavelengths. Relatively high classification accuracies were obtained for the invasive species using the original hyperspectral bands for both classifiers (overall accuracy, OA = 83–97%). The simulated data resulted in higher accuracies for Landsat 8, Sentinel 2A, and WorldView-3 compared to those computed for bands simulated to SPOT 6 and Pleiades 1B data. These findings suggest the potential of remote-sensing techniques in the discrimination of different plant species with similar morphological characteristics occupying the same niche.  相似文献   

The evolution of a continent: Thirteen years of EarthScope Magnetotelluric Three-Dimensional Imaging of the United States     

Adam Schultz 《《地质学报》英文版》2018,92(Z1):1-2

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Nanogeochemistry of hydrothermal magnetite     

Artur?P.?DeditiusEmail author  Martin?Reich  Adam?C.?Simon  Alexandra?Suvorova  Jaayke?Knipping  Malcolm?P.?Roberts  Sergey?Rubanov  Aaron?Dodd  Martin?Saunders 《Contributions to Mineralogy and Petrology》2018,173(6):46

Magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million (ppm) of elements such as Ti, Si, V, Al, Ca, Mg, Na, which tend to either structurally incorporate into growth and sector zones or form mineral micro- to nano-sized particles. Here, we report micro- to nano-structural and chemical data of hydrothermal magnetite from the Los Colorados iron oxide–apatite deposit in Chile, where magnetite displays both types of trace element incorporation. Three generations of magnetites (X–Z) were identified with concentrations of minor and trace elements that vary significantly: SiO₂, from below detection limit (bdl) to 3.1 wt%; Al₂O₃, 0.3–2.3 wt%; CaO, bdl–0.9 wt%; MgO, 0.02–2.5 wt%; TiO₂, 0.1–0.4 wt%; MnO, 0.04–0.2 wt%; Na₂O, bdl–0.4 wt%; and K₂O, bdl–0.4 wt%. An exception is V₂O₃, which is remarkably constant, ranging from 0.3 to 0.4 wt%. Six types of crystalline nanoparticles (NPs) were identified by means of transmission electron microscopy in the trace element-rich zones, which are each a few micrometres wide: (1) diopside, (2) clinoenstatite; (3) amphibole, (4) mica, (5) ulvöspinel, and (6) Ti-rich magnetite. In addition, Al-rich nanodomains, which contain 2–3 wt% of Al, occur within a single crystal of magnetite. The accumulation of NPs in the trace element-rich zones suggest that they form owing to supersaturation from a hydrothermal fluid, followed by entrapment during continuous growth of the magnetite surface. It is also concluded that mineral NPs promote exsolution of new phases from the mineral host, otherwise preserved as structurally bound trace elements. The presence of abundant mineral NPs in magnetite points to a complex incorporation of trace elements during growth, and provides a cautionary note on the interpretation of micron-scale chemical data of magnetite.  相似文献   

How the Distribution of Anthropogenic Nitrogen Has Changed in Narragansett Bay (RI,USA) Following Major Reductions in Nutrient Loads     

Autumn Oczkowski  Courtney Schmidt  Emily Santos  Kenneth Miller  Alana Hanson  Donald Cobb  Jason Krumholz  Adam Pimenta  Leanna Heffner  Sandra Robinson  Joaquín Chaves  Rick McKinney 《Estuaries and Coasts》2018,41(8):2260-2276

Over the past decade, nitrogen (N) loads to Narragansett Bay have decreased by more than 50%. These reductions were, in large part, the direct result of multiple wastewater treatment facility upgrades to tertiary treatment, a process which employs N removal. Here, we document ecosystem response to the N reductions and assess how the distribution of sewage N in Narragansett Bay has changed from before, during, and shortly after the upgrades. While others have observed clear responses when data were considered annually, our seasonal and regional comparisons of pre- and post-tertiary treatment dissolved inorganic nitrogen (DIN) concentrations and Secchi depth data, from bay-wide surveys conducted periodically from the early 1970s through 2016, resulted in only a few subtle differences. Thus, we sought to use stable isotope data to assess how sewage N is incorporated into the ecology of the Bay and how its distribution may have changed after the upgrades. The nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope measurements of particulate matter served as a proxy for phytoplankton, while macroalgae served as short-term integrators of water column bio-available N, and hard clams (Mercenaria mercenaria) as integrators of water column production. In contrast to other estuarine stable isotope studies that have observed an increased influence of isotopically lower marine N when sewage N is reduced, the opposite has occurred in Narragansett Bay. The tertiary treatment upgrades have increased the effluent δ¹⁵N values by at least 2‰. The plants and animals throughout Narragansett Bay have similarly increased by 1–2‰, on average. In contrast, the δ¹³C values measured in particulate matter and hard clams have declined by about the same amount. The δ¹⁵N results indicated that, even after the N reductions, sewage N still plays an important role in supporting primary and secondary production throughout the bay. However, the δ¹³C suggests that overall net production in Narragansett Bay has decreased. In the 5 years after the major wastewater treatment facilities came on-line for nutrient removal, oligotrophication has begun but sewage remains the dominant source of N to Narragansett Bay.  相似文献