bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photophysics of Eumelanin: Ab Initio Studies on the Electronic Spectroscopy and Photochemistry of 5,6‐Dihydroxyindole
Authors: Sobolewski Andrzej L. , Domcke Wolfgang 
Published: February 2007

AbstractExcited‐state reaction paths and energy profiles of 5,6‐dihydroxyindole (DHI), one of the elementary building blocks of eumelanin, have been determined with the approximated singles‐and‐doubles coupled‐cluster (CC2) method. 6‐Hydroxy‐4‐dihydro‐indol‐5‐one (HHI) is identified as a photochromic species, which is formed via nonadiabatic hydrogen migration from the dangling OH group of DHI to the neighboring carbon atom of the six‐membered ring. It is shown that HHI is a typical excited‐state hydrogen‐transfer (ESIHT) system. HHI absorbs strongly in the visible range of the spectrum. A barrierless hydrogen transfer in the 1ππ* excited state, followed by barrierless torsion of the hydroxyl group, lead to a low‐lying S1–S0 conical intersection and thus to ultrafast internal conversion. This very efficient mechanism of excited‐state deactivation provides HHI with a high degree of intrinsic photostability. It is suggested that the metastable photochemical product HHI plays an essential role for the photoprotective biological function of eumelanin.
An image analysis approach for automatic malignancy determination of prostate pathological images
Authors: Farjam Reza , Soltanian‐Zadeh Hamid , Jafari‐Khouzani Kourosh , Zoroofi Reza A. 
Published: February 2007

AbstractBackground:Determining malignancy of prostate pathological samples is important for treatment planning of prostate cancer. Traditionally, this is performed by expert pathologists who evaluate the structure of prostate glands in the biopsy samples. However, this is a subjective task due to inter‐ and intra‐observer differences among pathologists. Also, it is time‐consuming and difficult to some extent. Therefore, automatic determination of malignancy of prostate pathological samples is of interest.Methods:A texture‐based technique is first used to segment the prostate glands in the image. Features related to size and shape of these glands are then extracted and combined to generate an index, which is proportional to malignancy of cancer. A linear classifier is employed to classify the specimens into benign (low potential for malignancy) and malignant.Results:The leave‐one‐out technique is employed to evaluate the method using two datasets. The first has 91 images with similar magnifications and illuminations while the second has 199 images with different magnifications and illuminations. In the experiments, accuracies of about 98 and 95% have been achieved for these two datasets, respectively.Conclusions:An image analysis approach is employed to evaluate prostate pathological images. Experimental results show that the proposed method can successfully classify the prostate biopsy samples into benign and malignant. They also show that the proposed method is robust to variations in magnification and illumination. © 2007 Clinical Cytometry Society
A one‐dimensional model for simulating armouring and erosion on hillslopes: 2. Long term erosion and armouring predictions for two contrasting mine spoils
Authors: Sharmeen Saniya , Willgoose Garry R. 
Published: February 2007

AbstractThis paper investigates the dynamics of soil armouring as a result of fluvial erosion for a non‐cohesive sandy gravel spoil from the Ranger Mine, Australia, and a cohesive silt loam spoil from the Northparkes Mine, Australia, using a model for hillslope soil armouring. These long term predictions concentrate on the temporal and spatial changes of the spoil grading and erosion over 100–200 years for the flat cap regions (1–2%) and steep batter edges (10–30%) typically encountered on waste rock dumps. The existence of a significant rock fragment fraction in the Ranger spoil means that it armours readily, while Northparkes does not. For Ranger the waste rock showed reductions in (1) cumulative erosion of up to 81% from that obtained by extrapolating the initial erosion rate out 100 years and (2) the erosion/year by more than 10‐fold. For Northparkes reductions were less marked, with the maximum reduction in erosion/year being 37% after 200 years. For Ranger the reductions were greatest and fastest for intermediate gradient hillslopes. For the steepest hillslopes the armouring decreased because the flow shear stresses were large enough to mobilize all material in the armour layer. Model uncertainty was assessed with probabilistic confidence limits demonstrating that these erodibility reductions were statistically significant. A commonly used hillslope erosion model (sediment flux = β1 discharge m1 slope n1) was fitted to these predictions. The erodibility, β1, and m1 decreased with time, which was consistent with our physical intuition about armouring. At Ranger the parameter m1 asymptoted to 1·5–1·6 while at Northparkes it asymptoted to 1·2–1·3. At Ranger transient spatial trends in armouring led to a short term (50–200 years in the future) reduction in n1, to below zero under certain circumstances, recovering to an asymptote of about 0·5–1. At Northparkes n1 asymptoted to about 0·6, with no negative transients predicted. The m1 and n1 parameters predicted for Ranger were shown to be consistent with field data from a 10‐year‐old armoured hillslope and consistent with published relationships between erodibility and rock content for natural hillslopes. Copyright © 2007 John Wiley & Sons, Ltd.
‘Total’ fabric of some till landforms
Authors: Derbyshire Edward , McGown Alan , Radwan Amr 
Published: February 2007

AbstractThe distinction between clast‐dominant, matrix‐dominant and well‐graded tills is important in view of the influence of texture on the definition and function of till fines. Till fabric includes a wide range of features of both primary and secondary origin including folds, thrusts, fissures (the macrofabric), disposition of clasts (the mesofabric) and organization of the matrix (the microfabric). The results of fabric analysis of pebble, granule, sand, silt and clay in small depositional landforms beneath currently‐active glaciers are described. Deformation fabrics are distinguished in freshly deposited end moraines and flutes. The sand‐size material in deformed till may or may not behave in the same way as larger clasts, depending on the degree to which the till is matrix‐dominant. While clasts in saturated subglacial till tend to align themselves sub‐parallel to the depositional surface, the matrix usually retains abundant pore spaces. With slow, unloaded drainage, clast fabrics appear to be little modified. Such material is potentially unstable and any subsequent increase in overburden and hydraulic pressures may cause slope collapse and flowtill development. It is concluded that examination of a wide range of fabric parameters provides a means of distinguishing tills of diverse origins and of assessing their potential instability.
The morphology and hydrology of some Jamaican karst depressions
Authors: Day Michael 
Published: February 2007

AbstractAn area of shallow karst depressions in St. Ann parish, Jamaica is examined. Shallow, ‘temperate’ forms such as these are common in tropical karst areas.Depressions are analyzed morphometrically and a considerable degree of structural control appears to be exhibited. Some morphometric parameters, in particular the depth/diameter ratio, which have been used to postulate depression origin, are examined.Depression hydrology is investigated. Depressions appear to exhibit characteristics of small drainage basins. The occurrence of sporadic flood events is suggested as an important element in the development of surface channel networks. The integration of the depressions into the regional drainage system is investigated by water tracing of ‘underground flow sections’.Chemical analysis of waters in various parts of the drainage system reveals variations which point to the importance of solutional activity at the soil‐bedrock interface. The influence of a soil cover in promoting solutional activity is indicated.
Soils and geomorphology of the chalk in south‐east England
Authors: Catt J. A. , Hodgson J. M. 
Published: February 2007

AbstractSoil mapping and soil profile studies on the Chalk of south‐east England outline the distribution and origin of superficial deposits more clearly than hitherto, and do not support the widely accepted history of landscape development proposed by Wooldridge and Linton (1955). Deposits formed by weathering and periglacial disturbance of a thin cover of basal Tertiary deposits occur on all parts of the dip‐slope interfluves, suggesting that the exhumed sub‐Tertiary surface, somewhat lowered by dissolution of the Chalk, is much more extensive than supposed by Wooldridge and Linton. The evidence for high Plio‐Pleistocene sea levels is reviewed, with particular reference to their limited effect on soils and superficial deposits and on the morphology of the dip‐slope. Alternative explanations for the so‐called Calabrian marine platform and cliff are considered. Emphasis is placed on periglacial processes in the later Pleistocene denudation of the Chalk, and on the protective role played by the cover of disturbed basal Tertiary sediment.
Applications of the random model of drainage basin composition
Authors: Smart J. S. , Werner C. 
Published: February 2007

AbstractThe random model of drainage basin composition is founded on the assumptions that (a) natural channels are topologically random in the absence of geological controls and (b) for channel networks developed in similar environments, the exterior and interior link lengths are independent random variables with a common distribution for each type. The effectiveness of this model in estimating the values of geomorphic variables and in explaining and predicting geomorphic relationships is illustrated by several examples. The data required for these examples were obtained from map studies of 30 channel networks, comprising a total of about 8700 links, in eastern Kentucky. A common factor in the success of all three applications of the model is the way in which the planimetric features of drainage basins are determined by their underlying topologic structure.
Runoff generative process and runoff yield from arid talus mantled slopes
Authors: Yair A. , Lavee H. 
Published: February 2007

AbstractPrevious works dealing with the influence of a stone cover on runoff yield showed that runoff, attributed to the sealing effect of the topsoil by raindrops impact, was negatively related to the per cent of stone cover and stone size. These works were conducted on gentle slopes (3–11·5 degree) with a per cent of stone cover generally lower than 50 per cent, and composed of gravels. The present study deals with the runoff yield of steep talus slopes (26–36 degree) whose per cent of stone cover is very high (90–100 per cent), composed of cobbles and boulders. Three stimulated rainstorms were performed at various rainfall. intensities and durations on each one of six plots representative of the North eastern sector of Sinai. Although the contiguous stony cover prevented surface sealing by raindrops impact, runoff developed quite quickly on most slopes, and reached at peak discharge, after approximately ten minutes, up to 56 per cent of the rainfall. Differences between plots, in time lag, peak discharge and other hydrological variables, could be attributed mainly to the properties of the upper stony layer, with stone size as the most influential factor. Contrary to previous works, a positive relationship, was obtained between stone size to runoff yield. The result is explained by the process of water concentration. Each cobble and boulder behaves, on a smaller scale, like a bare rocky surface and yields per unit area water amounts beyond the infiltration rate of the limited uncovered areas. For a given stony cover the effect of water concentration is quicker with the big blocks than with gravels. A series of graphs trying to relate theoretically the relative importance of sealing and water concentration processes in runoff generation, at various conditions of stone cover and stone size, is proposed. The graphs enable to reconcile the results of the present study with those of previous works.
Lichens and the determination of river channel capacity
Authors: Gregory Ken J. 
Published: February 2007

AbstractThe identification of channel capacity associated with a particular frequency of peak discharges is necessary for discharge estimation for planning purposes at ungauged sites. Although lichen limits have been suggested to be useful for this purpose, previous studies have not elaborated their hydrological significance. Lichen limits are clearly defined on the sides of rock channels in New England. Australia and they are analyzed in relation to discharge at 6 gauging stations with up to 52 years of continuous record. It is demonstrated that the lowest lichen limit is maintained by peak discharges which occur on average at least once or twice each year. Recurrence intervals based on Annual Series and on Annual Exceedance Series are calculated and for the annual series are fairly consistent for the lowest lichen limit and range from 1·14 to 1·37 years. Lichenometry can be applied to the analysis of river channels in relation to the frequency of peak discharges. By reference to growth curves based upon lichens on Armidale tombstones it is shown that lichenometry may be employed to indicate dates for channel modification due to the removal of blocks and to dam construction and also to date the rock surface between lichen limits. Detailed analysis of the record from gauging stations indicates that where several lichen limits occur in a channel cross section each limit is related to periods when peak discharges exceeded the limits on at least 5 occasions. The lichen‐free surfaces were then recolonized by Parmelia spp. and the size of the lichen thalli indicates the time elapsing since these frequent high discharges.
Bedload stresses and Bagnold's bedform theory for water flows
Authors: Leeder Michael R. 
Published: February 2007

AbstractBagnold's theory of bedload stresses and bedforms requires that the tangential stress exerted at the base of a moving bedload dispersion in high stage plane beds is carried entirely by the grain stress T. Derivation of T from experimental data in flow channnels shows, however, that the fluid contribution τ′ is still dominant (≈ 1 to 2 × T). Particle concentrations in the experimental bedload dispersions approached 10 per cent and it is inferred that no appreciable concentration gradient exists. Grain collisions are thought to be most probable whenever more than 1 former stationary grain layer is in forward motion. High stage plane beds may be unstable when grain collisions cease. Current ripples evolve from the amplification and migration of chance defects due to unsteady fluid impulses generated by injection, or burst, phenomena in the viscous sublayer and not through any inherent static shear resistance deficit exerted by stationary bed grains.
The subdivision of a slope profile on the basis of soil properties: A case study from mid‐wales
Authors: Davidson Donald A. 
Published: February 2007

AbstractSedimentological analysis of particle size data from a hillslope profile in mid‐Wales allows the identification of two distinct upper slope units. These are described and analyzed in greater detail for clay and organic matter distribution. The original slope subdivision is substantiated by the results and the major differences in soils between the upper units are attributed to drainage contrasts.
Some comments on the quantitative formulation of geomorphological processes in a theoretical model
Authors: Ahnert Frank 
Published: February 2007

AbstractQuantitative procedures are discussed for the simulation of baselevel lowering, weathering, and several denudation processes within the framework of a three‐dimensional model of landform development Net baselevel lowering is modelled as the outcome of the mass balance at the slope foot Bedrock weathering is seen as a function of waste thickness; a distinction is made between mechanical weathering, with maximum intensity on bare bedrock, and chemical weathering, with maximum intensity under a waste cover thick enough to retain sufficient moisture. Denudation processes considered are splash, viscous flow, plastic flow, and wash‐the latter with a submodel for generating a characteristic spatial distribution of relative runoff discharge. Despite the different empirical results and theoretical considerations that influenced the design of the model equations for these denudation processes, all except suspended load wash denudation produce very similar slope forms. It is shown that these seemingly different equations can be interpreted as special cases of a single general denudation equation.
Modelling drainage headwater development
Authors: Calver A. 
Published: February 2007

AbstractProcesses operative in the divideward sections of streams and channels are reviewed, and the effects of their action over long periods of time are modelled for insight into long‐term valley head development. Upper valley axis profiles eventually become concave upwards over time but may show earlier convexity and convexo‐concavity. After any particular length of development different upper valley axis forms can exist in areas of different climate and hydrological response characteristics.
Simulation of flow geometry in a riffle‐pool stream
Authors: Richards K. S. 
Published: February 2007

AbstractThe nature of the flow in most natural streams is gradually varied rather than uniform. This is particularly true of streams with coarse gravel bed material organized into relatively stable riffle and pool features. In spite of this, there are few applications of the gradually varied flow models (e.g. the Bernoulli equation) to such streams. This paper presents some initial results of a simulation of flow patterns in two riffle‐pool reaches, using an open channel flow profile computation method based on an equation defining an energy balance between successive cross‐sections separated by an incremental distance.
Effect of soil properties on erosion by wash and splash
Authors: Luk S. H. 
Published: February 2007

AbstractThis paper describes laboratory testing of 148 samples collected from Southern Alberta for erosion by wash and splash. Rainfall intensity was held constant during these tests. Soil aggregation was the most significant variable explaining soil loss. The significance of other soil properties, such as organic carbon and clay content is variable, depending on the interrelationships among aggregate stability, organic content, and clay content of particular soils. Variations in erodibility of the major soils examined are explained by the resistance of aggregates to compaction and dispersion. Splash detachment and wash transport are the dominant erosion mechanisms in inter‐rill areas.
‘Bedload’ dynamics: Grain impacts, momentum transfer and derivation of a grain froude number
Authors: Leeder Michael R. 
Published: February 2007

AbstractA test is proposed for Bagnold's postulate that the normal weight stress due to moving ‘bedload’ is balanced by a solid transmitted stress due to the rate of change of momentum produced by grain impacts on unit area of the stationary bed. The test involves derivation of an expression for normal momentum transfer due to saltating grains at moderate transport stages when grain‐to‐grain collisions and partial suspension during saltation may be ignored. A dimensionless number, Φ, (a grain Froude Number) is derived, given by Ū2/g where Ū is the mean grain forward velocity, g is the gravitational acceleration and L̄ is the length of a single saltation ‘jump’. Equilibrium demands that Φ be unity during bedload transport involving saltating grains if Bagnold's postulate is correct. Experimental data shows Φ < 1, the discrepancy between theory and experiment being due to the existence of lift forces acting upon bedload grains. Bagnold's postulate is correct for concentrated dispersions of grains, as in grain flows, when fluid lift forces may be neglected due to high particle concentration.
Problems in the calibration of an acoustic device for the observation of bedload transport
Authors: Richards K. S. , Milne L. M. 
Published: February 2007

AbstractDevelopments in theoretical and empirical modelling of bedload transport processes are hindered by the lack of an adequate data base for testing or establishing the models. Conventional methods of measuring bedload transport rates fail to provide the necessary continuous or frequent record of variations at a single section. Acoustic techniques have the potential to overcome this deficiency, but their application has been very limited. Some of the problems of calibrating an acoustic device in the field and in a laboratory flume are discussed, and a possible circuit design described which might minimize calibration difficulties by automatically subtracting the noise generated by flow turbulence.
Intra‐catchment variability in solute response an east devon example
Authors: Foster I. D. L. 
Published: February 2007

AbstractModifications to the land use of a small catchment, including clearance, cultivation and an increase in drainage density, are shown to have influenced a number of solute characteristics. Contrasts are drawn between three source areas; an unmodified subcatchment draining an area of mixed deciduous woodland, and a tile drain system and drainage ditch receiving water from cultivated areas. Not only are the modifications identified in terms of mean solute concentrations, but it is also shown that a change in land use alters the interaction between independent hydrological and meteorological variables, and solute response. A tentative explanation is provided for long term solute behaviour in relation to a number of biological geochemical and hydrological controls.
Factors influencing the growth of miniature ice lenses
Authors: Burt T. P. 
Published: February 2007

AbstractExperiments involving six soil types indicated that the production of miniature ice lenses is dependent on soil moisture content and grain size with lenses being produced in finer‐grained soils at lower moisture contents than is possible in coarser soils. Explanation of the results involves consideration of the unsaturated hydraulic conductivity of the unfrozen soil through which water migrated to the freezing plane to allow ice lens growth.
A quantitative evaluation of pyrite weathering
Authors: Vear Alwyn , Curtis Charles 
Published: February 2007

AbstractNamurian sediments at Mam Tor, Derbyshire are cut by a major landslide and a geological fault. Both channel oxygenated waters into fragmented pyritic shales. Pyrite is rapidly oxidized to sulphuric acid, 1.5 g being destroyed by each litre of water passing through the fault‐crush. More than 99 per cent of the acid, however, is immediately consumed in clay‐mineral transformation and carbonate dissolution reactions. The typical acid‐sulphate ‘ochre’ springs thus retain less than 1 per cent of the acid generated in the crush zone. These very rapid and large scale chemical transformations probably contribute to the slide's continuing activity.