bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Application of Oxysilane Sol–Gel Electrochemical Glucose Biosensors Based on Cobalt Hexacyanoferrate Modified Carbon Film Electrodes
Authors: Florescu Monica , Barsan Madalina , Pauliukaite Rasa , Brett Christopher M. A. 
Published: February 2007

AbstractThe evaluation and characterization of a new glucose oxidase (GOx) electrochemical enzyme biosensors on a carbon film electrode support and using two types of sol–gel precursor mixture for enzyme immobilization was carried out in order to be employed as a short‐time‐use or as a disposable sensor. Carbon film electrodes were modified with films of CoHCF mediator by potential cycling. The sol–gel was prepared using a combination of 3‐glycidoxypropyltrimethoxysilane (GOPMOS) with methyltrimethoxysilane (MTMOS) or tetraethoxysilane (TEOS).
Semicontinuous Monitoring of Cadmium and Lead with a Screen‐Printed Sensor Modified by a Membrane
Authors: Betelu Stéphanie , Parat Corinne , Petrucciani Nathalie , Castetbon Alain , Authier Laurent , Potin‐Gautier Martine 
Published: February 2007

AbstractThe analytical performances of the developed sensor were evaluated in laboratory for the semicontinuous monitoring of Cd and Pb in water samples at μg L−1 level. The effects of oxygen, pH, and stirring on the voltammetric response of these metals were investigated. The O2 removal did not allow to improve the peak current. In return, stirring appeared indispensable to avoid the impoverishment of metals in the diffusion layer. The necessity to control the pH and the solution evolution in laboratory experiments was also clearly established. The semicontinuous monitoring of Cd and Pb was then performed for 42 h in tap water and demonstrated that sensor is a promised tool for semicontinuous environmental analyses.
Photoelectrocatalytic Oxidation of NADH with Electropolymerized Toluidine Blue O
Authors: Dilgin Yusuf , Gorton Lo , Nisli Gurel 
Published: February 2007

AbstractA poly(Toluidine Blue O) (poly‐TBO) modified electrode was successfully prepared by repeated sweeping the applied potential from −0.6 to +0.8 V (vs. SCE) on a glassy carbon electrode (GCE) in borate buffer solution at pH 9.1 containing 0.1 M NaNO3 and 0.4 mM Toluidine Blue O (TBO). The poly‐TBO modified GCE shows electrocatalytic activity toward NADH oxidation in phosphate buffer solution at pH 7.0, with an overpotential of ca. 350 mV lower than that at the bare electrode. The photoelectrocatalytic oxidation of NADH at this electrode was also successfully investigated by using cyclic voltammetry and amperometry at constant potential. When the modified electrode surface was irradiated with a 250 W halogen lamp, a photoelectrocatalytic effect was observed for NADH oxidation and the current was increased about 2.2 times. The applied potential was selected at +100 mV for amperometric and photoamperometric detection of NADH. A linear calibration graph for NADH was obtained in the range between 1.0×10−5 and 1.0×10−3 M and between 5.0×10−6 and 1.0×10−3 M for amperometric and photoamperometric studies, respectively. The effect of some interfering compounds, such as ascorbic acid and dopamine on the electrocatalytic and photoelectrocatalytic oxidation of NADH was tested.
Voltammetric Determination of Metamitron with an Electrogenerated Molecularly Imprinted Polymer Microsensor
Authors: Gómez‐Caballero Alberto , Unceta Nora , Goicolea M. Aranzazu , Barrio Ramón J. 
Published: February 2007

AbstractA molecularly imprinted polymer microsensor was synthesized onto the surface of a carbon fiber microelectrode (CFME) by cyclic voltammetry between −0.1 V and +1.35 V at a scan rate of 50 mV s−1. The monomers aniline and o‐phenylenediamine (o‐PD) were electrocopolymerized in the presence of the template (metamitron) in an aqueous medium of 0.1 M H2SO4. In order to obtain a sensor with the highest number of imprinted sites as possible, different experiments related to the polymerization process were carried out. The response of the synthesized microsensor was linear to the metamitron in the range between 10−6 and 10−4 with sensitivity of 0.143 nA μM−1 with good repeatability (<9% RSD). Employing these experimental conditions, the microsensor was able to distinguish the metamitron from other closely related triazines like metribuzin or isomethiozin.
Resolution of Overlapped Reduction Signals in Short Hetero‐oligonucleotides by Elimination Voltammetry
Authors: Mikelova Radka , Trnkova Libuse , Jelen Frantisek , Adam Vojtech , Kizek Rene 
Published: February 2007

AbstractThe resolution of overlapped reduction voltammetric signals of adenine (A) and cytosine (C) residues in short synthetic hetero‐oligodeoxynucleotides (ODNs) with different sequences of A and C, but with the same ratio (A/C=1/2), was carried out by elimination voltammetry with linear scan (EVLS). The EVLS, as a mathematical transformation of voltammetric total currents measured at different scan rates, is capable to yield very sensitive resolution of potentially closed signals, which cannot be separated by common electrochemical methods. The best resolution of A and C signals was observed when the EVLS function eliminating the charging and kinetic currents (Ic, Ik) and conserving the diffusion current (Id) was combined with adsorption stripping technique (AdS). The resulting peak‐counterpeak signal made it possible not only to separate the responses of A and C residues, but also to follow the dynamics of adsorption processes on mercury electrode surfaces. Together with the effect of the accumulation time on peak‐counterpeak signal, the effect of pH and temperature on this signal was studied. The relation between elimination signals and the structure changes of ODNs was discussed.
Amperometric Biosensors Based on Choline Oxidase Entrapped in Polyacrylamide Microgels
Authors: Sánchez‐Paniagua López M. , Hervás Pérez J. P. , López‐Cabarcos E. , López‐Ruiz B. 
Published: February 2007

AbstractA choline amperometric biosensor has been designed using as biological component choline oxidase (ChOx) entrapped in polyacrylamide microgels. The working electrode was prepared by holding the enzyme loaded microgels on a platinum electrode by a dialysis membrane. It was found that the optimum microgel cross‐linking required to retain ChOx and to allow the diffusion of choline was 7.0%. The response of the biosensor was optimized in relation to pH, temperature and working potential and the following optimal values were obtained: pH 9.0, temperature range between 20 and 30 °C, and potential +0.6 V. Under optimal conditions the sensitivity for choline was 17.45 mA M−1 cm−2, the detection limit 8 μM, and the response linear range from 2×10−5 M to 2×10−4 M. This biosensor has been also used as a nicotine detector due to the inhibition of the catalytic activity of choline oxidase by this compound. Moreover, the simultaneous entrapment of a second enzyme, acetylcholinesterase (AChE), in the microgels makes the biosensor sensible to acetylcholine.
Open tubular CE for in vitro oxidation studies of human very‐low‐density lipoprotein particles
Authors: Ruiz‐Jiménez José , Kuldvee Ruth , Chen Jie , Öörni Katariina , Kovanen Petri , Riekkola Marja‐Liisa 
Published: February 2007

AbstractHuman very‐low‐density lipoprotein (VLDL) particles were immobilised on the inner wall of electrochromatographic fused‐silica capillaries, and the applicability of these capillary columns in oxidation studies was investigated. Capillaries coated with radiolabelled VLDL particles showed a coating efficiency of 97%, and allowed estimation of the amount of VLDL present in a capillary. Radioactivity measurements and atomic force microscopy with tapping mode confirmed the presence of VLDL particles as a monolayer. The pI determined for the VLDL was 4.7–4.8 varying with the human source. The effects of VLDL concentration, coating time and pH on the coating stability were clarified, and the stability was examined in terms of the repeatability of EOF and retention factors of selected steroids. The repeatability of run‐to‐run and the coating‐to‐coating reproducibility ranged from 2.6 to 4.9% and 3.2 to 6.6%, respectively. The lifetime of a coating was at least 7 days or 84 consecutive runs. The in situ copper‐mediated VLDL oxidation carried out in the capillary with optimised VLDL coating showed that, during the oxidation of VLDL particles, the negative charges of the particles are increased, leading to enhanced EOF mobilities. Several oxidation parameters, including copper sulfate concentration, amount of EDTA needed to stop the reaction, pH and the oxidation procedure, were examined. Effect of the oxidation process on the stability of the coating in one capillary, and in five different capillaries ranged between 0.4–4.1% and 0.8–6.6%, respectively. The in situ oxidation of VLDL particles was compared with that of low‐density lipoproteins.
Problems in the determination of plastic and liquid limits of remoulded soils using a drop‐cone penetrometer
Authors: Davidson Donald A. 
Published: February 2007

AbstractThis short communication describes difficulties of sample preparation associated with the determination of plastic and liquid limits using a drop‐cone penetrometer. Problems of sample packing, soil moisture distribution and degree of remoulding are identified. These problems are particularly relevant in influencing liquid limit values whilst the effects on plastic limits are less marked. It is concluded that if the need is for the quick determination of liquid and plastic limits for general classification purposes, then the traditional Casagrande and thread methods are adequate. If these limits require to be measured with greater precision using the drop‐cone technique, then careful consideration must be given to sample preparation.
The measurement of watertable levels in structured clay soils by means of open auger holes
Authors: Armstrong Adrian C. 
Published: February 2007

AbstractIn structured clay soils, water levels in open auger holes (dipwells) respond to water movement through macropores and may mask the existence of drier zones either at depth or within peds. Variability between replicated dipwells expresses the small scale variation in the soil, and statements about soil water regimes should be made in statistical terms. Suitably replicated dipwells give sufficiently precise measurements of mean watertable position for studies of soil water regimes.
Vertical soil water movement in a tropical rainforest catchment in northeast queensland
Authors: Bonell M. , Cassells D. S. , Gilmour D. A. 
Published: February 2007

AbstractIn a tropical rainforest catchment, shallow piezometers respond almost instantaneously to rainfall, but the dominant ground water recharge mechanisms are not well understood. To improve understanding, the downward movement of soil water on a runoff plot was traced using tritiated water injected at 0·20 m below the surface which marks the lower boundary of active subsurface storm flow. The tritium pulse was translated slowly down the profile, apparently dominated by interstitial piston flow on the lines described by Zimmermann's theoretical model. This recharge mechanism accounted for about 35 per cent of rainfall or 50 per cent of throughfall. The pulse's advance may have also been delayed by the upward movement of soil water indicated by the distribution of hydraulic potential under different hydrological conditions. The result was an increase in soil water transit time particularly below 1·0 m. There was also evidence in the tracer profiles for rapid by‐pass flow but the volumes concerned could not be quantified in this experiment.
Flandrian relative sea level changes in the Ythan Valley, Northeast Scotland
Authors: Smith D. E. , Cullingford R. A. , Brooks C. L. 
Published: February 2007

AbstractRelict Flandrian estuarine deposits in the Ythan valley are confined to an area in the lower valley around the present estuary. They rest upon a discontinuous layer of peat over an irregular surface of sand and gravel, and consist for the most part of a grey silty clay, or carse deposit, which forms terraces or small areas of carseland. At the seaward end of the estuary the grey silty clay contains a layer of grey, micaceous, silty fine sand, which tapers into the basal peat, whilst in places the surface of the grey silty clay is covered by peat and/or blown sand. The vegetational context and age of these deposits have been determined at Waterside, near the mouth of the present estuary. Here, the grey silty clay accumulated as the result of a marine transgression which began in the early Flandrian, and culminated between about 6189·95 and some time prior to 4000·80 radiocarbon years B.P. The carseland surface produced by this phase of accumulation is the highest Flandrian estuarine surface in the valley, at about 4·5 m O.D., and is correlated with the Main Postglacial Shoreline elsewhere in eastern Scotland. Withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached, though this is far from certain. The grey, micaceous, silty fine sand layer is dated at approximately 6850·140 radiocarbon years B.P., and is correlated with similar layers that may have been deposited following a storm surge. The paper concludes with some considerations on the age and distribution of the Main Postglacial Shoreline in eastern Scotland.
Rates of cave and landform development in the Yorkshire Dales from speleothem age data
Authors: Gascoyne Melvyn , Ford Derek C. , Schwarcz Henry P. 
Published: February 2007

AbstractUranium‐series ages have been obtained for 87 speleothems collected from nine major cave systems in the Craven district of northern England. Large systems such as Ease Gill Caverns, the West Kingsdale caves, and Gaping Gill‐Ingleborough Cave, which contain relict high‐level tunnels, are found to be older than 350,000 years (the limit of the 230Th/234U dating method). There is little evidence to indicate a significant enlargement of these passages since this time. Estimates of the age of Victoria Cave from 234U/238U isotopic ratios suggest that the cave has been fully relict for more than 500,000 years. Ages of in situ speleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr. These rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets. Using the present elevation of caves with respect to adjacent valley floor levels, mean maximum valley entrenchment rates are found to range between 5 cm/ky and < 20cm/ky, which corresponds to 6 m to < 24 m of lowering per glacial/interglacial cycle. These rates suggest that upper beds of the limestone were incised to form the Yorkshire Dales between 1 and 2 million years ago.The results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the literature.
The formation of deep topsoils in Orkney
Authors: Davidson Donald A. , Simpson Ian A. 
Published: February 2007

AbstractThe Soil Survey for Scotland, in their mapping of the soils in Orkney, identified a deep top phase of the Bilbster Series. This soil is distinguished by having a topsoil usually in excess of 75 cm and it occurs almost exclusively on the Mainland of Orkney, especially in the west round Marwick and Skaill Bays. An anthropogenic origin to this soil is proposed and the present study is designed to investigate the particular processes of formation which have led to the increase in soil depth. Results from transect and grid surveys indicate how the soil is thickest adjacent to old farms. The historical literature suggests a wide range of possible inputs from seaweed and calcareous sand to turves after they had been used as bedding for cattle. Analytical results support the last process as the dominant one and an accumulation rate of c.1 mm/yr is proposed.
Refinement of a technique for determining rock mass strength for geomorphological purposes
Authors: Moon B. P. 
Published: February 2007

AbstractUse of a field technique recently devised by Selby for the measurement of rock mass strength has resulted in the understanding of the relationship between rock mass strength and slope form. It is suggested that the accuracy of rock mass strength assessments may be enhanced by further subdividing the rating scales for intact rock strength and the spacing of partings. The relationship between rock mass strength and gradient is reformulated using southern African data, and statistically based confidence limits for identifying strength equilibrium slopes are proposed.
Gas‐induced erosion features in the North Sea
Authors: Hovland Martin 
Published: February 2007

AbstractPockmarks are prominent features on the seafloor at two main regions of the North Sea, the South Fladen area and the Norwegian Trench.The pockmarks vary in size from 5 m across to about 150 m and in depth from 1 m to about 20 m. Some of the features consist of several very small ‘unit‐pockmarks’. These are probably gas‐induced erosion features and found only in soft, finegrained, marine and glaciomarine sediments. They are probably caused by shallow‐ or deep‐seated gas (or fluid) release through the seabed, whereby the finest particles are thrown into suspension and redistributed by nearbottom currents.On the North Sea Plateau a small pockmarked area has recently been found. A close relationship exists here between mobile gas in the upper sediments, faulting in the soft sediments and the morphology of the seabed.Other morphological features in the North Sea such as ‘coast parallel depressions’ and ‘elongated depressions’ or terraces are also interpreted here as gas‐induced erosion products. This applies, yet again, to the ‘mottled seabed’ features, which appear as patches of high reflectivity on side scan sonar records from the North Sea Plateau; they correspond to shallow seabed depressions on the deep towed boomer records. Judging from reported observations from several shallow seas world wide volatile transport through the seabed is probably quite common and several morphological features are undoubtably induced by this process. Several erosion features of similar origin are probably common, also, in deep ocean basins.
A test of petrological control in the development of bornhardts and koppies on the Matopos Batholith, Zimbabwe
Authors: Pye K. , Goudie A. S. , Thomas D. S. G. 
Published: February 2007

AbstractThis paper investigates the reasons for the presence of both domed inselbergs (bornhardts) and boulder inselbergs (koppies) on the Matopos Batholith, Zimbabwe. XRF and microprobe analyses of rock samples from 16 bornhardts and 24 koppies have shown no significant chemical or mineralogical differences which might indicate greater weathering resistance of the bornhardts. Many bornhardts are located on massive bodies of slowly‐cooled porphyritic granite which were emplaced at a relatively late stage in the evolution of the batholith. The surrounding rocks are less porphyritic and appear to have been foliated during deformation associated with emplacement of the later bodies. The entire batholith has been affected by post‐emplacement tectonism which has created three major fracture systems. The morphological differences between bornhardts and koppies in this area are therefore considered to reflect differences in jointing which arise both from the primary igneous emplacement process and from tectonic deformation.
Abrupt variation in channel width along part of the River Severn, near Shrewsbury, Shropshire, England
Authors: Dury G. H. 
Published: February 2007

AbstractThe River Severn, near Shrewsbury, Shropshire, England, is formed by the union of the uppermost Severn with the Vyrnwy; both of these major headstreams drain from the Welsh upland. That part of the trunk Severn here under consideration has been under investigation for some years as exemplifying Osage‐type underfitness. In the course of the investigation, a census was made of width between banktops on two reaches, and of water surface width on one of these reaches: the difference between the two types of width gives the value of a third type, the width of batter. All three width types produce Poisson distributions of frequency. Width, particularly width between banktops, varies rapidly in the downstream direction. In view of the observed Poisson distributions, transform rather than arithmetic values have been used in difference‐of‐means tests applied to variation along the channel: cube root transforms are the type selected. Although there is little to choose, on the study reaches, between arithmetic means and Poisson modes, the results obtained do suggest a query about the selection of the most appropriate width values, for instance for the purposes of channel morphology. All types of width are found to vary along the channel far more rapidly than would be expected from mere randomness. Variation in bank strength appears to account for about half the variation in width between banktops. The results obtained for batter width could be applied in the design of a sampling programme designed to identify local difference in bank strength.
Creep processes in landslides
Authors: Van Asch Th. W. J. 
Published: February 2007

AbstractDisplacement of landslide blocks after initial slope failure can be very slow. In most cases movement of the blocks is attributed to sliding along a well‐defined slip surface. It is discussed here whether, in addition to these so‐called plastic movements, (continuous) creep processes are involved in the slow displacement. The study was carried out in the downstream part of the Bonne valley in the French Alps, where landslide complexes have developed in varved clay material. Displacements of landslide blocks were measured during a period of three years. Inclinometer measurements in flexible tubes showed that a creep zone developed above the slip surface in a zone about 1 m thick. These field observations on creep processes were supported by soil mechanical analysis. Threshold values for creep found in the laboratory nearly coincide with threshold values calculated from a field creep model developed by Ter‐Stepanian. During the measuring period ±15 per cent of the displacement of the blocks possibly occurred via continuous creep.
Digging by badgers and rabbits on some wooded slopes in Belgium
Authors: Voslamber Berend , Veen Arthur W. L. 
Published: February 2007

AbstractEight forest areas, totalling 128.7 hectares, located near the northern border area of the Belgian Ardennes, have been surveyed for soil material brought to the surface by burrowing animals. It appeared that at least 7003.6 kg/ha were present, brought up by badgers and rabbits. The amount turned out to vary a factor 103 between the eight regions. During the half year survey period badgers added some 570 kg to their mounds. On this basis the rate of mass transport effected directly by badgers may be estimated at an insignificant 0.02 gcm−1 y−1. Also, production of available sediment by these animals is relatively unimportant in this temperate humid forest environment.