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• 1
Article
Language: English
In: Climatic Change, 2010, Vol.103(3), pp.571-595
Description: Efforts to predict responses to climate change and to interpret modern or paleoclimate indicators are influenced by several levels of potential amplifiers, which increase or exaggerate climate impacts, and/or filters, which reduce or mute impacts. With respect to geomorphic responses and indicators, climate forcings are partly mediated by ecological, hydrological, and other processes which may amplify or filter impacts on surface processes and landforms. Then, geomorphic responses themselves may be threshold-dominated or dynamically unstable, producing disproportionately large and long-lived responses to climate changes or disturbances. Or, responses may be dynamically stable, whereby resistance or resilience of geomorphic systems minimizes the effects of changes. Thus a given geomorphic response to climate could represent (at least) two levels of amplification and/or filtering. An example is given for three fluvial systems in Kentucky, U.S.A, the Kentucky, Green, and Big South Fork Rivers. Climate impacts in the early Quaternary were amplified by glacially-driven reorganization of the ancestral Ohio River system to the North, and by dynamical instability in the down-cutting response of rivers incising plateau surfaces. Effects of more recent climate changes, however, have been filtered to varying extents. Using alluvial terraces as an example, the study rivers show distinctly different responses to climate forcings. The lower Green River has extensive, well-developed terraces recording several episodes of aggradation and downcutting, while the Big South Fork River has no alluvial terraces. The Kentucky River is intermediate, with limited preservation of relatively recent terraces. The differences can be explained in terms of differences among the rivers in (1) filtering effects of constraints on fluvial responses imposed by strongly incised, steep-walled bedrock controlled valleys; and (2) amplifier effects of periodic damming of lower river reaches by glaciofluvial outwash.
Keywords: Climate Change -- Research ; Geomorphology -- Research ; Rivers -- Environmental Aspects;
ISSN: 0165-0009
E-ISSN: 1573-1480
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• 2
Article
In: Clinical Orthopaedics and Related Research, 2012, Vol.470(8), pp.2313-2318
Description: BACKGROUND: The developing world contains more than ¾ of the world’s population, and has the largest burden of musculoskeletal disease. Published studies provide crucial information that can influence healthcare policies. Presumably much information regarding burden in the developing world would arise from authors from developing countries. However, the extent of participation of authors from the developing world in widely read orthopaedic journals is unclear. PURPOSE: We surveyed four influential English-language orthopaedic journals to document the contributions of authors from developing countries. METHODS: We surveyed Clinical Orthopaedics and Related Research, Journal of Orthopaedic Trauma, and the American and British volumes of The Journal of Bone and Joint Surgery, from May 2007 through May 2010. The country of origin of all authors was identified. We used the designations provided by the International Monetary Fund to define countries as either developed or developing. RESULTS: Two hundred sixty-five of 3964 publications (7%) included authors from developing countries. Ninety percent of these had authors from developing countries with industrialized and emerging-market economies. Publications from Sub-Saharan Africa accounted for only 0.4% of the 3964 articles reviewed and 5.6% of the 265 articles with developing world authorship. Countries with the least robust economies were least represented. Less than 1/3 of articles with authors from the developing world had coauthors from developed or other developing countries. CONCLUSION: Additional studies are needed to determine the reasons for the low representation noted and to establish strategies to increase the number of orthopaedic publications from parts of the world where the burden of musculoskeletal disease is the greatest.
Keywords: Emerging Markets -- Surveys ; Developing Countries -- Surveys ; Orthopedic Surgery -- Surveys;
ISSN: 0009-921X
E-ISSN: 15281132
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• 3
Article
Language: English
In: Mathematical Geosciences, 2016, Vol.48(7), pp.743-765
Description: Evolution of Earth surface systems (ESS) comprises sequential transitions between system states. Treating these as directed graphs, algebraic graph theory was used to quantify complexity of archetypal structures, and empirical examples of forest succession and alluvial river channel change. Spectral radius measures structural complexity and is highest for fully connected, lowest for linear sequential and cyclic graphs, and intermediate for divergent and convergent patterns. The irregularity index $$\beta$$ β represents the extent to which a subgraph is representative of the full graph. Fully connected graphs have $$\beta = 1$$ β = 1 . Lower values are found in linear and cycle patterns, while higher values, such as those of divergent and convergent patterns, are due to a few highly connected nodes. Algebraic connectivity ( $$\mu (\mathrm{G}))$$ μ ( G ) ) indicates inferential synchronization and is inversely related to historical contingency. Highest values are associated with fully connected and strongly connected mesh graphs, whereas forking structures and linear sequences all have $$\mu (G)$$ μ ( G ) = 1, with cycles slightly higher. Diverging vs. converging graphs of the same size and topology have no differences with respect to graph complexity, so complexity change is dependent on whether development results in increased or reduced richness. Convergent-divergent mode switching, however, would generally increase ESS complexity, decrease irregularity, and increase algebraic connectivity. As ESS and associated graphs evolve, none of the possible trends reduces complexity, which can only remain constant or increase. Algebraic connectivity may increase, however. As improving shortcomings in ESS evolution models generally result in elaborating possible state changes, this produces more structurally complex but less historically contingent models.
Keywords: Complexity ; Evolutionary trajectory ; Directed graph ; Algebraic graph theory
ISSN: 1874-8961
E-ISSN: 1874-8953
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• 4
Article
Language: English
In: Metallurgical and Materials Transactions B, 2013, Vol.44(1), pp.115-122
Description: Recently the reductive expansion synthesis (RES) method was introduced as a means to create nano- and sub-micron metal particles and alloys by rapid heating of physical mixtures of urea with a metal nitrate. In the present work the generality of the RES method was demonstrated by creating metal micron and sub-micron particles from oxide and hydroxide precursors, and outlining the impact of temperature, precursor ratio, and gas flow rate on the product. For example, precursor selection impacted the temperature required for complete reduction, the amount of carbon present, and the size of the metal particles. For complete NiO reduction to micron scale particles, high urea content and a high temperature [ ca. 1073 K (800 °C)] were required. In contrast, Ni(OH) 2 was reduced to metal at far lower temperatures. Moreover, the Ni particles formed from NiOH were sub-micron ( ca. 200 nm) in size and carbon encapsulated. Other parameter variations had a similarly significant impact. Indeed, the reciprocal relationship between inert gas flow rate and the extent of reduction supports the supposition that the primary mechanism of reduced metal particle formation is the reduction of metal oxide particles by gases produced by urea decomposition. Collectively these and other findings indicate the RES method can be manipulated to create a range of micron and sub-micron reduced metal particle architectures appropriate for different applications.
Keywords: Hydroxides ; Alloys ; Architecture ; Urea;
ISSN: 1073-5615
E-ISSN: 1543-1916
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• 5
Article
Language: English
In: International Urogynecology Journal, 2013, Vol.24(9), pp.1547-1551
Description: Byline: Ilias Giarenis (1), Jonathan Phillips (2), Heleni Mastoroudes (1), Sushma Srikrishna (1), Dudley Robinson (1), Cornelius Lewis (2), Linda Cardozo (1) Keywords: Effective dose; Radiation exposure; Urinary incontinence; Videourodynamics; Videocystourethrography Abstract: Introduction and hypothesis Our aim was to calculate the total radiation exposure and the dose absorbed by specific organs during videourodynamics (VUDS) in women. Methods This was a retrospective study of consecutive women attending for VUDS in a tertiary referral urodynamics unit. Tests with missing data and those that were terminated during the filling phase of the cystometry were excluded from the study. The VUDS examination was tailored according to the indication for the test and the urodynamic question to be answered. The PCXMC simulation program (version 2.0) was utilised to calculate the effective dose and the dose absorbed by individual organs. Results Out of 345 consecutive VUDS, 264 were included in the study. The mean effective dose was 0.34 mSv (SD: 0.15) and the mean fluoroscopic time was 63.15 s (SD: 21.81). Multivariate linear regression analysis of factors affecting the radiation dose showed that BMI (p=0.009) and fluoroscopy time (p〈0.001) were the only statistically significant factors. The final linear regression model for the estimation of the effective dose was Eff. Dose (mSv)=-0.049+0.003*BMI (kg/m.sup.2)+0.005*fluoroscopy time (s). Conclusions This study reveals that women are exposed to relatively small amounts of radiation during VUDS. The use of fluoroscopy only without additional static radiographic images minimises exposure to a level consistent with the "as low as reasonably achievable" radiological principle. Author Affiliation: (1) Department of Urogynaecology, King's College Hospital, London, SE5 9RS, UK (2) Department of Medical Engineering and Physics, King's College Hospital, London, UK Article History: Registration Date: 27/01/2013 Received Date: 12/10/2012 Accepted Date: 26/01/2013 Online Date: 22/02/2013
Keywords: Effective dose ; Radiation exposure ; Urinary incontinence ; Videourodynamics ; Videocystourethrography
ISSN: 0937-3462
E-ISSN: 1433-3023
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• 6
Article
Language: English
In: Journal of Electronic Materials, 2015, Vol.44(5), pp.1367-1376
Description: To test a theory of the recently discovered phenomenon of super dielectric behavior at very low frequency, the dielectric constants of several ‘pastes’, composed of porous alumina powders filled to the point of incipient wetness with water containing dissolved sodium chloride, were measured. The effective dielectric low frequency constants of some of the pastes were greater than 10 10 , dramatically higher than that of any material ever reported. Moreover, the total energy density reported for one capacitor generated with NaCl-based super dielectric material is marginally higher than found in any prior report. These results are consistent with this recently postulated model of low frequency super dielectric behavior in porous, non-conductive materials saturated with ion-containing liquids: upon the application of an electric field, ions dissolved in the saturating liquid contained in the pores will travel to the ends of pore-filling liquid droplets creating giant dipoles. The fields of these giant dipoles oppose the applied field, reducing the net field created per unit of charge on the capacitor plates, effectively increasing charge/voltage ratio, hence capacitance. This is simply a version of the theory of ‘polarizable media’ found in most classic texts on electromagnetism. Other observations reported here include (1) the impact of ion concentration on dielectric values, (2) a maximum voltage similar to that associated with the electrical breakdown of water, (3) the loss of capacitance upon drying, (4) the recovery of capacitance upon the addition of water to a dry super dielectric material, and (5) the linear relationship between capacitance and inverse thickness. All observations are consistent with the earlier proposed model of the super dielectric phenomenon. An extrapolation of results suggests this technology can lead to energy density greater than the best lithium-ion battery.
Keywords: Dielectric ; capacitors ; energy storage
ISSN: 0361-5235
E-ISSN: 1543-186X
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• 7
Article
Language: English
In: International Orthopaedics, 2012, Vol.36(10), pp.2007-2013
Description: Eighty per cent of severe fractures occur in developing countries. Long bone fractures are treated by conservative methods if proper implants, intraoperative imaging and consistent electricity are lacking. These conservative treatments often result in lifelong disability. Locked intramedullary nailing is the standard of care for long bone fractures in the developed world. The Surgical Implant Generation Network (SIGN) has developed technology that allows all orthopaedic surgeons to treat fracture patients with locked intramedullary nailing without the need for image intensifiers, fracture tables or power reaming. Introduced in 1999, SIGN nails have been used to treat more than 100,000 patients in over 55 developing world countries. SIGN instruments and implants are donated to hospitals with the stipulation that they will be used to treat the poor at no cost. Studies have shown that patients return to function more rapidly, hospital stays are reduced, infection rates are low and clinical outcomes excellent. Cost-effectiveness analysis has confirmed that the system not only provides better outcomes, but does so at a reduced cost. SIGN continues to develop new technologies, in an effort to transform lives and bring equality in fracture care to the poorest of regions.
ISSN: 0341-2695
E-ISSN: 1432-5195
Source: Springer Science & Business Media B.V.
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• 8
Article
Language: English
In: European Spine Journal, 2012, Vol.21(9), pp.1880-1886
Description: Purpose: The incidence of osteoporotic fractures is increasing with an ageing population. This has potential consequences for health services, patients and their families. Treatment of osteoporotic vertebral compression fractures (OVCFs) has been limited to non-surgical measures so far. The social and functional consequences of balloon kyphoplasty, a recent development for the treatment of VCF, were assessed in this cohort study. Methods: Data collected prospectively from 53 patients undergoing balloon kyphoplasty for symptomatic OVCF in our hospital's spinal unit were compared with data from an historical age-matched group of 51 consecutive patients treated conservatively for symptomatic OVCF. Social functionality was recorded prior to the injury, and at 6-month and 1-year follow-up; mortality was recorded at 6 months and 1 year. Results: The mortality rate in the balloon kyphoplasty group was 11 % (6/53) at 1 year post-OVCF, versus 22 % (11/51) in the conservatively treated controls. A drift to a lower level of social functionality (defined by a lower level of independence) was observed at 1 year in 21 % of patients in the balloon kyphoplasty group versus 53 % of patients in the conservatively treated group. A drift to a lower level of independence was noted in 67 % of the conservatively treated patients who started at a lower level of functionality versus 20 % drift in a similar group who were treated with balloon kyphoplasty. Conclusions: The reduction in mortality and drift in social functionality at 1 year following treatment with balloon kyphoplasty suggests that it is a viable option for the management of OVCFs.
Keywords: Balloon kyphoplasty ; Osteoporosis ; Social function ; Vertebral compression fractures
ISSN: 0940-6719
E-ISSN: 1432-0932
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• 9
Article
Language: English
In: Journal of Soils and Sediments, 2010, Vol.10(4), pp.640-651
Description: Byline: Michael C. Slattery (1), Lee M. Todd (1), Jonathan D. Phillips (2), John A. Breyer (1) Keywords: Radiocarbon dating; Sea level rise; Sediment accretion; Trinity River delta Abstract: Purpose This study uses sediment cores to quantify Holocene sedimentation rates in the Trinity River delta, Texas. An important question is whether modern fluvial sediment input from the Trinity River is adequate to sustain sedimentation in the delta, thereby combating subsidence and further wetland loss. Our objective was to quantify sedimentation rates within the delta in order to assess whether the delta is in- or out-of-phase with modern sediment delivery rates. Materials and methods Two core samples were retrieved from the subaerial Trinity River delta, an intricate system of anastomosing/bifurcating channels, levees, lakes, and interdistributary marshes covering an area of 126.1 km.sup.2. Detailed descriptions of sample characteristics were recorded, including wet and dry color, texture, moisture content, and plasticity. Bulk density and grain-size measurements were also conducted on the cores. Shell fragments from each sediment core were subjected to accelerator mass spectrometry 14.sup.C dating. Results and discussion Radiocarbon dating of shell fragments recovered from sediment cores (292--536 cm) ranged from 2.8 to 3.2 Ka. Mean sediment accumulation rates varied between 1.2 and 1.8 mm year.sup.--1 for two areas of the delta, consistent with previous research. The amount of sediment needed to cover the surface area of the modern Trinity River delta was calculated to obtain the approximate amount necessary for accretion rates from 0.25 to 3.0 mm year.sup.--1. Using the mean Holocene sediment accretion rate from this study (1.5 mm year.sup.--1) to cover 100% of the Trinity River delta, the amount of sediment needed per year was calculated to be 265,000 Mg year.sup.--1, which is 3.8 times the amount of sediment (i.e., 70,000 Mg year.sup.--1) currently delivered to the delta by the Trinity River. Modern fluvial sediment input from the Trinity River is thus inadequate to account for Holocene sedimentation rates in the delta. Conclusions Sediment accumulation rates of 1.2 and 1.8 mm year.sup.--1 were attained for two interdistributary marshes in the Trinity River delta by radiocarbon dating of shell fragments recovered from sediment cores. These accumulation rates are well within the ranges established in previous studies. However, modern fluvial sediment input from the Trinity River to the delta is occurring at a rate of approximately 0.4 mm year.sup.--1, which is insufficient to combat subsidence and wetland loss and keep pace with future sea level rise. Author Affiliation: (1) Institute for Environmental Studies and Department of Environmental Science, Texas Christian University, Fort Worth, TX, 76129, USA (2) Department of Geography, University of Kentucky, Lexington, KY, 40506-0027, USA Article History: Registration Date: 29/03/2010 Received Date: 28/01/2010 Accepted Date: 28/03/2010 Online Date: 27/04/2010 Article note: Responsible editor: Marcel van der Perk
Keywords: Radiocarbon dating ; Sea level rise ; Sediment accretion ; Trinity River delta
ISSN: 1439-0108
E-ISSN: 1614-7480
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• 10
Article
Language: English
In: Environmental Management, 1989, Vol.13(4), pp.493-502
Description: Nonpoint source pollution control requires assessment of the influence of dispersed runoff-contributing areas on downstream water quality. This evaluation must consider two separate phases: site-to-stream loading and downstream fluvial transport. Any model, combination of models, or procedure for making this assessment can be generalized to a simple spatial model or framework, which considers runoff or pollutant loading per unit area and down-stream attenuation, with drainage area as a scaling factor. This spatial model has a probabilistic interpretation and can be used in conjunction with a standard dilution model to give a probabilistic estimate of the impacts at the basin mouth of runoff from a specific upstream contributing area. It is illustrated by applying it to an assessment of the probability that various copper concentrations at the mouth of the urbanized South Platte River basin in Denver, Colorado, USA, will be exceeded as a result of runoff from a subbasin within the city. Determining the probability that a concentration of a pollutant at the basin mouth can be attributed to runoff from a discrete area within the basin is useful for targeting and risk assessment because it enables quantitative risk-based comparisons. The spatial framework is also useful for evaluating management and control options, since actions within the basin can be directly linked to water quality at a downstream point.
Keywords: Nonpoint source pollution ; Spatial model ; Basin ; Risk assessment ; Targeting ; Contributing areas
ISSN: 0364-152X
E-ISSN: 1432-1009
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