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Search Results: 1 - 10 of 719662 matches for " M. A. Smith "
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The Role of Phragmites australis in Mediating Inland Salt Marsh Migration in a Mid-Atlantic Estuary
Joseph A. M. Smith
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0065091
Abstract: Many sea level rise adaptation plans emphasize the protection of adjacent uplands to allow for inland salt marsh migration, but little empirical information exists on this process. Using aerial photos from 1930 and 2006 of Delaware Estuary coastal habitats in New Jersey, I documented the rate of coastal forest retreat and the rate of inland salt marsh migration across 101.1 km of undeveloped salt marsh and forest ecotone. Over this time, the amount of forest edge at this ecotone nearly doubled. In addition, the average amount of forest retreat was 141.2 m while the amount of salt marsh inland migration was 41.9 m. Variation in forest retreat within the study area was influenced by variation in slope. The lag between the amount of forest retreat and salt marsh migration is accounted for by the presence of Phragmites australis which occupies the forest and salt marsh ecotone. Phragmites expands from this edge into forest dieback areas, and the ability of salt marsh to move inland and displace Phragmites is likely influenced by salinity at both an estuary-wide scale and at the scale of local subwatersheds. Inland movement of salt marsh is lowest at lower salinity areas further away from the mouth of the estuary and closer to local heads of tide. These results allow for better prediction of salt marsh migration in estuarine landscapes and provide guidance for adaptation planners seeking to prioritize those places with the highest likelihood of inland salt marsh migration in the near-term.
The properties of XO-5b and WASP-82b redetermined using new high-precision transit photometry and global data analyses
A. M. S. Smith
Physics , 2014,
Abstract: This paper presents new transit photometry from the Isaac Newton Telescope of two transiting exoplanetary systems, XO-5 and WASP-82. In each case the new transit light curve is more precise than any other of that system previously published. The new data are analysed alongside previously-published photometry and radial velocities, resulting in an improved orbital ephemeris and a refined set of system parameters in each case. The observational baseline of XO-5 is extended by very nearly four years, resulting in a determination of the orbital period of XO-5b to a precision of just 50 ms. The mass and radius of XO-5b are 1.19$\pm$0.03 and 1.14$\pm$0.03 times those of Jupiter, respectively. The light curve of WASP-82 is only the second published for this system. The planetary mass is 1.25$\pm$0.05 $M_{\rm Jup}$, and the radius is 1.71$\pm$0.08 $M_{\rm Jup}$.
Influence of model resolution on the atmospheric transport of 10Be
U. Heikkil ,A. M. Smith
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Understanding the transport path of the solar activity proxy 10Be from source to archive is crucial for the interpretation of its observed variability. The extent of mixing of the strong production signal has been quantified in a previous study (Heikkil et al., 2009). In this study we perform sensitivity studies to investigate the influence of model resolution on the degree of mixing and transport path of 10Be in the atmosphere using the ECHAM5-HAM aerosol-climate model. This study permits us to choose an acceptable resolution, and so minimum CPU time, to produce reconstructions as physically accurate as possible. Five model resolutions are applied: T21L19: a coarse horizontal and vertical resolution with model top at ca. 30 km, T42L31: an average horizontal and fine vertical one, T42L39: similar vertical resolution than L19 but including the middle atmosphere up to ca. 80 km, T63L31: a fine horizontal and vertical resolution and T63L47: a fine resolution horizontally and vertically with middle atmosphere. Comparison with observations suggests that a finer horizontal and vertical resolution might be beneficial, producing a reduced meridional gradient, although the spread between observations was much larger than between the five model runs. In terms of atmospheric mixing the differences became more distinguishable. All resolutions agreed that the main driver of deposition variability, observed in natural archives, is the input of stratospheric 10Be (total contribution 68%) which is transported into the troposphere at latitudes 30–50°. In the troposphere the model resolutions deviated largely in the dispersion of the stratospheric component over latitude. The finest resolution (T63L47) predicted the least dispersion towards low latitudes but the most towards the poles, whereas the coarsest resolution (T21L19) suggested the opposite. The tropospheric components of 10Be differed less between the five model runs. The largest differences were found in the polar tropospheric components, which contribute the least to total production (≈ 4%). We conclude that the use of the T42 horizontal resolution seems to be sufficient in terms of atmospheric mixing of a stratospheric tracer because no substantial improvement was seen when the resolution was increased from T42 to T63. The use of the middle atmospheric configuration is a trade-off between correctly describing stratospheric dynamics and having to reduce vertical resolution. The use of a high vertical resolution seemed more beneficial than the middle atmospheric configuration in this study. The differences found between the T42L31 and T63L31 resolutions were so small that T42L31 is a good choice because of its computational efficiency.
Influence of model resolution on the atmospheric transport of 10Be
U. Heikkil?,A. M. Smith
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012, DOI: 10.5194/acp-12-10601-2012
Abstract: Understanding the transport path of the solar activity proxy 10Be from source to archive is crucial for the interpretation of its observed variability. The extent of mixing of the strong production signal has been quantified in a previous study (Heikkil et al., 2009). In this study we perform sensitivity studies to investigate the influence of model resolution on the degree of mixing and transport path of 10Be in the atmosphere using the ECHAM5-HAM aerosol-climate model. This study permits us to choose an acceptable resolution, and so minimum CPU time, to produce reconstructions as physically accurate as possible. Five model resolutions are applied: T21L19: a coarse horizontal and vertical resolution with model top at ca. 30 km, T42L31: an average horizontal and fine vertical one, T42L39: similar vertical resolution than L19 but including the middle atmosphere up to ca. 80 km, T63L31: a fine horizontal and vertical resolution and T63L47: a fine resolution horizontally and vertically with middle atmosphere. Comparison with observations suggests that a finer horizontal and vertical resolution might be beneficial, producing a reduced meridional gradient, although the spread between observations was much larger than between the five model runs. In terms of atmospheric mixing the differences became more distinguishable. All resolutions agreed that the main driver of deposition variability, observed in natural archives, is the input of stratospheric 10Be (total contribution 68%) which is transported into the troposphere at latitudes 30–50°. In the troposphere the model resolutions deviated largely in the dispersion of the stratospheric component over latitude. The finest resolution (T63L47) predicted the least dispersion towards low latitudes but the most towards the poles, whereas the coarsest resolution (T21L19) suggested the opposite. The tropospheric components of 10Be differed less between the five model runs. The largest differences were found in the polar tropospheric components, which contribute the least to total production (≈ 4%). We conclude that the use of the T42 horizontal resolution seems to be sufficient in terms of atmospheric mixing of a stratospheric tracer because no substantial improvement was seen when the resolution was increased from T42 to T63. The use of the middle atmospheric configuration is a trade-off between correctly describing stratospheric dynamics and having to reduce vertical resolution. The use of a high vertical resolution seemed more beneficial than the middle atmospheric configuration in this study. The differences fou
Word learning under infinite uncertainty
Richard A. Blythe,Andrew D. M. Smith,Kenny Smith
Computer Science , 2014,
Abstract: Language learners learn the meanings of many thousands of words, despite encountering them in complex environments where infinitely many meanings might be inferred by the learner as their true meaning. This problem of infinite referential uncertainty is often attributed to Willard Van Orman Quine. We provide a mathematical formalisation of an ideal cross-situational learner attempting to learn under infinite referential uncertainty, and identify conditions under which this can happen. As Quine's intuitions suggest, learning under infinite uncertainty is possible, provided that learners have some means of ranking candidate word meanings in terms of their plausibility; furthermore, our analysis shows that this ranking could in fact be exceedingly weak, implying that constraints allowing learners to infer the plausibility of candidate word meanings could also be weak.
Comparison of Hard-Core and Soft-Core Potentials for Modelling Flocking in Free Space
J. A Smith,A. M Martin
Physics , 2009,
Abstract: An investigation into the properties of a two dimensional (2D+1) system of self propelled particles (known as boids) in free space is conducted using a Lagrangian Individual-Based Model. A potential, associated with each boid is specified and a Lagrangian is subsequently derived in order to obtain the equations of motion for each particle in the flock. The Morse potential and the Lennard-Jones potential, both well understood in atomic and molecular physics, are specified. In contrast to the original model proposed by Vicsek [Phys. Rev. Lett. 75, 1226 (1995)] systems are considered with open boundary conditions. These two models successfully replicate the phases observed in Vicsek's original model, as well as several other significant phases, providing a realistic model of a wide range of flocking phenomena.
Is bigger better: The association between follicle size and livebirth rate following IVF?  [PDF]
Jaime M. Knopman, James A. Grifo, Akiva P. Novetsky, Meghan B. Smith, Alan S. Berkeley
Open Journal of Obstetrics and Gynecology (OJOG) , 2012, DOI: 10.4236/ojog.2012.24075
Abstract: Purpose: To analyze the correlation between lead follicle size at hCG trigger and IVF outcome. Methods: A review of all patients undergoing their first IVF cycle between 1/2005-12/2009 was performed. Four groups were evaluated (<18 mm, 18 - 18.9mm, 19 - 19.9 mm and ≥20 mm), based on the mean diameter of the two largest follicles on day of ovulation trigger (OT); cycle parameters and outcomes were analyzed. Results: 1577 cycles were reviewed. There were no significant differences noted for cycle parameters or outcomes for the 4 groups. However, although LBR was not significantly different, there was a decline noted as lead follicle size increased. Conclusions: Delaying the administration of OT to enhance follicular growth does not appear to improve IVF outcome. Larger lead follicles do not yield a higher percentage of mature oocytes, embryos available for transfer or LBR. A misguided zest to achieve a higher quantity of fertilizable oocytes may impair oocyte and embryo quality.
Genotypic covariance matrices and their inverses for models allowing dominance and inbreeding
SP Smith, A M?ki-Tanila
Genetics Selection Evolution , 1990, DOI: 10.1186/1297-9686-22-1-65
Abstract:
MalHaploFreq: A computer programme for estimating malaria haplotype frequencies from blood samples
Ian M Hastings, Thomas A Smith
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-130
Abstract: An appropriate method for obtaining frequencies from prevalence data is by Maximum Likelihood analysis. A computer programme has been developed that allows the frequency of markers, and haplotypes defined by up to three codons, to be estimated from blood phenotype data.The programme has been fully documented [see Additional File 1] and provided with a user-friendly interface suitable for large scale analyses. It returns accurate frequencies and 95% confidence intervals from simulated dataset sets and has been extensively tested on field data sets.The programme is included [see Additional File 2] and/or may be freely downloaded from [1]. It can then be used to extract molecular marker and haplotype frequencies from their prevalence in human blood samples. This should enhance the use of frequency data to inform antimalarial drug policy choice.The identification of molecular markers (mutations) associated with drug resistance in P. falciparum, and the ability to detect these markers in the blood of infected people, means that large-scale population surveys can be used to infer the likely efficacy of antimalarial drug treatment regimes [2]. This allows their use in large scale surveillance surveys [3]. These surveys measure, and generally report, the prevalence of the marker i.e. the proportion of patient blood samples in which the marker is detected. This is clinically-useful information (it is related to a patient's probability of failing drug treatment) but it is less appropriate as a public health surveillance tool. It is the frequency of the drug resistant mutation, defined as the proportion of parasite clones in which the marker is present, and the rate at which it is increasing which determines the likely time before a drug becomes ineffective and requires replacement. Prevalence and frequency may differ markedly because several parasites clones often simultaneously co-infect the same patient: for example if patients have three clones (a 'multiplicity of infectio
A Comparison of Placement in First-Year University Mathematics Courses Using Paper and Online Administration of a Placement Test
Phyllis A. Schumacher,Richard M. Smith
International Electronic Journal of Mathematics Education , 2008,
Abstract: Today, many universities in the United States use mathematics placement tests in combination with high school grades and SAT scores to place students in freshman mathematics courses. In an attempt to make this process more convenient for students and universities, these tests are beginning to be given online. This paper describes the history of a university mathematics placement test, originally given in 1992, which was converted to an online format in 2005. The placement method is described and a logistic regression is used to evaluate the accuracy of the online placement procedure in comparison to the placement with the paper test.
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