bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory simulation of periglacial solifluction: Significance of porewater pressures, moisture contents and undrained shear strengths during soil thawing
Authors: Harris Charles , Davies Michael C. R. , Coutard Jean‐Pierre 
Published: February 2007

AbstractLaboratory simulation of periglacial solifluction in two natural soils, one a sandy silt, the other a gravelly silty sand, was undertaken on a 12° slope in a thermally controlled 5 m square chamber. Soil freezing and thawing took place from the top downwards in an open hydraulic system. Frost heaving and surface downslope movements were much greater in the silt‐rich soil than in the sandy soil. In both cases, solifluction took place during the thaw period. At any given depth, porewater pressures rose rapidly immediately following soil thaw, and were generally positive for several days, though not in excess of hydrostatic pressure. Soil moisture contents following thaw exceeded the liquid limit and measured in situ undrained shear strengths were low, ranging between 0.8 kPa near the surface and 9.0 kPa at depth. Conventional slope stability analyses based on total stress and effective stress conditions indicated that the thawing slope was not susceptible to rapid failure. It was concluded that the observed soil displacements represent post‐thaw strain when soil moisture contents were high and Theological properties were intermediate between those of a viscous fluid and a plastic creeping solid.
Interannual variations of the thermal regime of the active layer and near‐surface permafrost in northern Alaska
Authors: Romanovsky V. E. , Osterkamp T. E. 
Published: February 2007

AbstractAir, ground surface, active layer and permafrost temperature measurements were made every four hours from 1986 through 1992 near Prudhoe Bay West Dock (WD), Deadhorse Airport (DH) and Franklin Bluffs (FB). Mean annual air temperatures (MAAT) were nearly identical (−12.6 °C at WD, −12.9°C at DH, −12.5°C at FB) while the amplitudes increased from the coast inland (17.2°C at WD, 18.4°C at DH, 20.8°C at FB). Interannual variations were similar (3.2°C at WD, 2.9°C at DH and FB). Mean annual ground surface temperatures (MAGST) were similar at FB (−5.8°C) and DH (−6.2°C) and much colder at WD (−8.8°C) with amplitudes of 14.5°C at WD, 13.5°C at DH and 15.2°C at FB. Interannual variations were about the same at WD (3.8°C) and DH (3.9°C) and much smaller at FB (1.4°C). Differences between MAGST and MAAT were about the same at FB (6.8°C) and DH (6.7°C) and much smaller at WD (3.9°C). The results suggest that the snow cover was thinner at WD and/or its properties were significantly different compared with the inland sites. Mean annual permafrost surface temperatures (MAPST) were the same at FB and DH (−6.8°C) and much colder at WD (−9.1°C) with interannual variations of 2.7°C at WD, 3.0°C at DH and 1.8°C at FB. Thermal offset (MAPST − MAGST) was about the same at WD (−0.7°C) and DH (−0.67°C) and larger at FB (−1.03°C). Generally, thawing at the ground surface began earlier at FB than at DH and WD. Average duration of thawing (99 days at WD, 104 days at DH, 107 days at FB) and dates of the start of ground freezing (16 September at WD, 18 September at DH, 17 September at FB) were similar at all three sites. Average durations for freezing the active layer were similar at FB (62.5 days) and DH (68 days) and much less at WD (42 days). Active layer thicknesses increased from the coast inland (range of 0.21 m to 0.46 m at WD, 0.42 m to 0.69 m at DH, 0.57 m to 0.72 m at FB) and showed systematic temporal variations. These variations in active layer thicknesses may have significant temporal and spatial effects on the carbon balance of the tundra.
Rockslide processes on the north slope of popocatepetl Volcano, Mexico
Authors: Palacios David 
Published: February 2007

AbstractThis paper analyses the geomorphology of the north face of Popocatepetl Volcano (5450 m). The surface of the slope was covered earlier by the northern Popocatepetl Glacier and gradually exposed during the current century. The glacier formed at the time of the last great eruption of Popocatepetl in the seventeenth century, and reached its maximum extension at the end of the nineteenth century, at the peak of the Little Ice Age. A ramp formed at the snout of the glacier, composed primarily of ash dating from the last eruption. The material was mixed with large boulders that have been bulldozed into place by the glacier snout. As the glacier retreated, deep gorges formed on the ramp and glacial hollows appeared at the base of the steep sides of the volanic cone. Today, large‐scale rockslide processes occur on the north face. Layers of snow form a lubricating layer. The ash slides easily over the snow, covering it and later preventing it from melting and sublimation. Blocks fall from the present‐day glacial snout and pile up on the snow. Later, they slide over the snow and infill the hollows and gorges.
Identification of intermolecular disulfide linkages in underivatised peptides using negative ion electrospray mass spectrometry. A joint experimental and theoretical study
Authors: Bilusich Daniel , Bowie John H. 
Published: February 2007

AbstractThe [MH]− ion of a symmetrical peptide containing one intermolecular disulfide linkage cleaves through the disulfide link to produce up to four fragment anions. Two of these characteristic fragments are formed by a cleavage initiated from the Cys enolate anion on the peptide backbone. The other fragment anions are formed by a cleavage directed from an anion site on the disulfide side chain. In the case of an unsymmetrical peptide containing one intermolecular disulfide, the [MH]− anion may cleave through the disulfide unit to give a maximum of eight cleavage anions. These fragmentations are low‐energy processes as determined by theoretical calculations carried out at the HF/6‐31G(d)//AM1 level of theory. Collision‐induced mass spectra of the fragment anions may provide the sequence of the peptide. Copyright © 2007 John Wiley & Sons, Ltd.
Does the electron ionization induced fragmentation of partly saturated stereoisomeric pyrrolo‐ and isoindoloquinazolinones show stereospecificity?
Authors: Pihlaja Kalevi , Martiskainen Olli , Stájer Géza 
Published: February 2007

AbstractThe electron ionization mass spectrometric behavior of pyrroloquinazolinones (1–6) and isoindoloquinazolinones (7–14) was studied. These compounds were further classified as partly saturated pyrroloquinazolinones (1–3), benzologues (7–11), methylene‐bridged derivatives (4–6, 12, 13) and a bisacyl compound (14). The mass spectra of the pyrrolo‐ and isoindoloquinazolinones did not exhibit stereospecific retro‐Diels‐Alder (RDA) fragmentations. The cyclohexane‐fused compounds 7 (cis annelated) and 8 (trans annelated) did display some other ions differing in their abundances that could be used to differentiate this pair of stereoisomers. Also the cyclohexene‐fused compounds 2, 3, 9 and 10 exhibited somewhat different ion abundances pairwise that could be utilized for isomeric differentiation. Earlier hypothesis of pyrrolo ring cleavage via the loss of C3H5O. was strengthened by the fragmentation of compounds 1–4. RDA(±H) fragmentation is more favorable than the formation of [M–R]+ ions (RH, C6H4CH3, or C6H4Cl) when an unsaturated bicyclic group is present but both RDA fragmentation and [M–R]+ formation occur for cyclohexene‐fused compounds, possibly because of the lower ring strain than with norbornene‐fused compounds. The [M–H]+ ion was abundant for compounds 7 and 8 as was [M–Ar]+ for 1–4 and 11. Although the compounds studied might participate in amide‐imidol tautomerism, no indication of such tautomerism was detected. Copyright © 2007 John Wiley & Sons, Ltd.
Rapid determination of six metabolites from multiple cytochrome P450 probe substrates in human liver microsome by liquid chromatography/mass spectrometry: application to high‐throughput inhibition screening of terpenoids
Authors: He Fan , Bi Hui‐chang , Xie Zhi‐yong , Zuo Zhong , Li Jian‐kang , Li Xin , Zhao Li‐zi , Chen Xiao , Huang Min 
Published: February 2007

AbstractA rapid liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the determination of six cytochrome P450 (CYP) probe substrate metabolites including paracetamol (PAR) for CYP1A2, 4‐hydroxytolbutamide (OHTOL) for CYP2C9, 5‐hydroxyomeprazole (OHOMe) for CYP2C19, dextrorphan (DEXM) for CYP2D6, 6‐hydroxychlorzoxazone (OHCHL) for CYP2E1 and dehydronifedipine (DNIF) for CYP3A4. The triple‐quadrupole mass spectrometer was operated in both positive and negative modes, and selective reaction monitoring was used for quantification. The method was validated over the concentration ranges (0.075/0.04/0.05/0.02/0.1/0.0625 µM to 4.8/2.56/3.2/1.28/6.4/4.0 µM) for PAR/OHTOL/OHOME/DEXP/OHCHL/DNIF analytes with acceptable accuracy and precision. The inhibitory effect on the six CYP enzymes has been verified with their known specific inhibitors. This high‐throughput inhibition screening approach has been successfully applied to study the inhibitory effects of 18 terpenoids on CYP enzymes. Among them, tanshinone IIA and cryptotanshinone are found to be potent inhibitors to CYP1A2, while artemisinin is a marginal inhibitor to CYP1A2 and glycyrrhetic acid is a weak inhibitor to CYP2C9. Copyright © 2007 John Wiley & Sons, Ltd.
Size matters! Fragmentation chemistry of [Cu(L)n]2+ complexes of diacylglycerophosphocholines as a function of coordination number (n = 2–7)
Authors: James Patrick F. , Perugini Matthew A. , O'Hair Richard A. J. 
Published: February 2007

Abstract[Cu(L)n]2+ complexes of 1,2‐dihexanoyl‐sn‐glycero‐3‐phosphocholine (L = D6PC) are formed upon electrospray ionization mass spectrometry (ESI‐MS) of an 8 mM solution of D6PC with 4 mM CuCl2 in 10 mM ammonium acetate buffer, pH 6.1. The collision‐induced dissociation (CID) reactions of the [Cu(L)n]2+ complexes were examined in a linear ion trap mass spectrometer. A rich fragmentation chemistry was observed, including: loss of a neutral ligand; intermolecular ligand‐ligand SN2 methylation; metal ion induced ligand fragmentation via carboxylate abstraction; and phosphate abstraction. The dominant reaction channel depends on the size (n) of the complex. Thus loss of neutral ligand(s) is the sole reaction channel for n = 5–7. At n = 4, SN2 methylation and carboxylate abstraction start to compete with neutral ligand loss. At n = 2 the carboxylate abstraction and phosphate abstraction reactions dominate the CID spectrum. The carboxylate abstraction and phosphate abstraction reactions are likely to be driven via neighboring group pathways. PM3 calculations, carried out to compare competing neighboring pathways based on the relative stabilities of the product ions, suggest a preference for five‐membered ring formation for ligand fragmentation involving both carboxylate and phosphate abstraction. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of polyether mixtures using thin‐layer chromatography and matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Watanabe Takehiro , Kawasaki Hideya , Kimoto Takashi , Arakawa Ryuichi 
Published: February 2007

AbstractThin‐layer chromatography (TLC) and matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) were combined to achieve characterization of polyether mixtures. Three polyethers, polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetramethylene glycol (PTMG), or mixtures of these compounds, were studied. One shortcoming of mixture analysis of synthetic polymers using MALDI‐MS is that individual polymers in the mixture may display different detection sensitivities. For example, the MALDI mass spectrum of an equimolar mixture of PEG, PPG and PTMG displayed a high intensity of PPG ions, while no PTMG ions were detectable; however, PTMG ions were detected after the mixture had been separated by TLC. This combined TLC and MALDI‐MS analysis of a PPG polymer bearing reactive epoxy groups showed that the polymer contained byproducts with different end‐groups. These byproducts were identified as chloro‐substituted polymers formed during polymer synthesis. Our study shows TLC to be a rapid and low‐cost separation technique, and that it can be combined with MALDI‐MS to achieve effective analysis of synthetic polymers. Copyright © 2007 John Wiley & Sons, Ltd.
Developing technology for surgery in the UK: a multidisciplinary meeting of engineers and surgeons
Authors: Taylor G. W. 
Published: February 2007

AbstractThere is an increasing necessity for surgeons and engineers to work together in order to target future technological developments at clinical need and cost‐effectiveness. This is a report of two linked meetings with these objectives, held at the Institute of Mechanical Engineers, London, UK. The two meetings were organized by the same faculty members and held on consecutive days. Delegates included surgeons, academic mechanical engineers, researchers and industrial representatives. The programme was made up of varied presentations by surgeons and engineers as well as open discussion of the topics covered. Delegates were updated on the current state of surgical robotics in the UK in four surgical specialties; urology, neurosurgery, orthopaedics and ENT. This included clinical and experimental evidence, together with discussion of future advances. Minimally invasive surgery, real‐time imaging and the development of more compact and cost effective surgical robots were identified as key areas for future research. Copyright © 2007 John Wiley & Sons, Ltd.
Modes of colonization of an heterogenous alluvial area on the edge of the garonne river by Phalaris arundinacea L
Authors: Conchou O. , Pautou G. 
Published: February 2007

AbstractThe modes of colonization of a heterogenous alluvial area by Phalaris arundinacea L., a pioneer species, were studied on the edge of the Garonne river downstream of Toulouse (S.W. France). The heterogeneity of the location is essentially represented (1) by the type of soil: sands and gravels on the banks of the Garonne and silts in the hollows at a certain distance from the river; (2) by the period of submersion: zones flooded only during short periods and zones submerged during six months of the year; and (3) by the fertility of the substratum.The response of the Phalaris arundinacea population were measured using vegetation structure parameters and descriptions of the development cycle. Water plays the most important part in the identification of space colonization modes. Two types of individual plants appear. Those living in submerged environments for a very short time are characterized by both a high biomass and sexual reproduction energy allowance, and by unimodal growth. Those living in environments flooded over long periods are characterized by both a low biomass and sexual reproduction energy allowance, and by a bimodal growth in two successive generations: a submersion generation and a low‐water generation. Specific competition reduces the differences between the two types of individual plants from the point of view of population cover and of the structure and density of the individual plants. Phalaris arundinacea L. is shown to have a remarkable capacity for colonizing sites with distinctive ecological characteristics.
Effect of a changed temperature regime on the benthos of a norwegian regulated river
Authors: Saltveit Svein Jakob , Bremnes Trond , Brittain John E. 
Published: February 2007

AbstractThe lowermost 20 km of the River Surna, north‐western Norway receives cool water during summer from a hypolimnetic release mountain reservoir. The benthic fauna is completely dominated by insects. Benthic densities immediately below the power station are much lower than at all other localities. Although benthic densities increase downstream of the power station, they never exceed the densities above. The dominant insect group, chironomids, can be divided into four categories according to their abundance and distribution above and below the power station: (1) rare or absent above, but common or abundant below; (2) abundant or common above but rare or absent below; (3) slightly less abundant below; (4) unchanged abundance. No major differences in the species composition were recorded for stonefilies, mayflies and caddisflies.
Effects of dams, regulation and pollution on fish stocks in the Vltava river in Prague
Authors: Kubečka Jan , Vostradovský Jiři 
Published: February 2007

AbstractFish abundance and size composition in a 28 km stretch of the Vltava River in the Czech capital of Prague were studied using horizontal dual‐beam scientific sonar. Very low fish densities (0.6–0.7 fish/100m3) were found above Prague where the river is influenced by a cascade of reservoirs. These have a retention time of more than 100 days and release hypolimnetic water. A significant increase in fish density was found in the Berounka River confluence (a tributary with a normal, seasonal temperature pattern) just above the city (about 10 fish/100 m3). The fish stock is fairly low in the city itself because of channelization of the river bed (1.3–3.5 fish/100 m3), but much greater densities (14.9–16.9 fish/100 m3) were found below the city where the river receives a high organic load of partially treated sewage and has a semi‐natural shoreline. The largest average fish size and biomass were also reported from this section.
Effects of hydropower peaking on epilithon and invertebrate community trophic structure
Authors: Valentin S. , Wasson J. G. , Philippe M. 
Published: February 2007

AbstractHydropower generation induces rapid and frequent fluctuations of hydrodynamic parameters in rivers downstream of hydroelectric impoundments. On the FontauliéGre river (ArdéGche basin, France), water releases come from the Loire basin and the flow varies from 1.3 to 20 m3/s for one reach and from 0.1 to 20 m3/s for another reach. A reference site upstream was chosen to compare the communities with two downstream impacted sites. These two sites enabled two different base flow situations to be studied simultaneously and also the effect of base flow enhancement at one site. Benthic and epilithic samples were collected at the three sites on three dates. Epilithon development was linked to hydraulic regimes, with a major increase in algal biomass, dominated by filamentous algae, linked to the minimum base flow level and to the duration of periods without peaks. The macroinvertebrate communities of impacted reaches were less diversified and more specialized, with predominance of one or two taxa, whereas communities in upstream reaches were more diverse. The different morphological units specificity was attenuated in hydropeaking situations. In the case of a very low base flow, the lentic units with very low velocities (less than 4 cm s−1) had different fauna. The downstream algal development explained part of the change in benthic community structure in trophic groups (i.e. dominance of scrapers) in the site with the higher base flow. When the base flow was too low, a trophic discordance was observed and excess algal biomass represented a limiting factor. Thus, this study indicated that base flow level and duration had important effects on epilithic development and on invertebrate trophic structure in terms of mean velocities and of number of days without peaks.
Dispersal, growth and mortality of brown trout (Salmo trutta L.) stocked in a regulated West Norwegian river
Authors: Fjellheim Arne , Raddum Gunnar G. , Barlaup Bjosrn T. 
Published: February 2007

AbstractAs part of a fishery enhancement scheme, 70 000 fingerlings of anadromous brown trout (Salmo trutta L.) were stocked in the regulated River Teigdal, western Norway. To evaluate the stocking programme 10 000 of the hatchery reared fish were marked and released at 10 different localities. The results showed that the hatchery reared fish were inferior to wild brown trout. During the first weeks densities were high in the areas of stocking, varying between 27 and 680 individuals per m2. Stocked fish colonizing adjacent areas were mostly found upstream. Very few fish were found to cross the river from the point of release. One week after stocking food consumption of the hatchery reared fish was low compared with wild trout. Stocked trout had a lower growth rate (0.05 mm d−1) than native fish (0.08 mm d−1). However, fish stocked in deeper, slower flowing areas grew faster than those stocked in shallow riffle areas. The mortality of the stocked trout was 99% from July to April, being highest during the winter. Wild fish survived better, having a mortality of 79% over the same period. The value of the stocking programme is questioned. As an alterative, methods of biotope adjustment are proposed to increase the carrying capacity of wild trout in the river.
Macrozoobenthos in some rapids in a lowland river in Finland before and after the construction of a hydroelectric power plant
Authors: Nyman Curt 
Published: February 2007

AbstractIn the beginning of the 1980s a hydroelectric power plant was constructed in the middle course of the lowland river Perhonjoki in western Finland. Some shallow lakes upstream of the power plant were enlarged for use as a reservoir and some rapids downstream were dredged and remodelled. As a consequence of the construction, the flow was almost completely diverted from a 2.5 km stretch of the river and the former rapids in this area were remodelled with weirs. The discharge from the power plant was regulated in the short term during low flow seasons in winter and summer. The effects of this project on the stream bottom fauna has been studied. The sampling started in 1980 before any major impact took place and has continued until 1992.In the low flow stretch of the river the lotic fauna of the former rapids has withdrawn to small rivulets and several species have disappeared, including the large caddisfly Arctopsyche ladogensis. In the remodelled rapids downstream from the power plant large numbers of black fly larvae have appeared every spring since the power plant was completed. The reason for this was probably dredging of the rapids, which wiped out the natural moss vegetation on the stones in the rapids and generated large areas of bare stone surfaces in places with suitable current velocities for the larvae. A lake outlet effect might also be part of the reason, even if samples of the phytoplankton could not demonstrate higher amounts of plankton downstream of the power plant reservoir than upstream. In late summer the number of filter‐feeding trichopterans has increased and the species composition has changed. Neurclipsis bimaculata and Ceratopsyche nevae have become more abundant and Arctopsyche ladogensis as well as several species commonly found among water moss have disappeared.
Migration of a fast‐growing population of brown trout (Salmo trutta l.) through a fish ladder in relation to water flow and water temperature
Authors: Jensen Arne J. , Aass Per 
Published: February 2007

AbstractThe ascent of brown trout spawners (Salmo trutta L.) in the fish ladder at the Hunder dam on the River Gudbrandsdalslågen, eastern Norway was correlated with water flow and water temperature from 1983 to 1990. Ascent took place from the end of June to the middle of October. The majority of the trout entered the fishway during August and the first half of September. Before arriving at the fish ladder, ascending trout must pass through two sections of river with differing flow regimes and optimum flows for migration. Conditions in the section below the dam are critical for ascent. When discharge over the dam exceeded about 180m3s−1, it was difficult for the fish to locate the entrance to the fishway. High discharges often occurred in June and July, delaying or preventing ascent. At flows below 20m3 s−1 it was difficult for fish larger than 80 cm to approach the ladder entrance. When flow decreased to below 10 m3 s−1, ascent was difficult for all sizes. Water temperature was of less importance. Lengths of brown trout ascending the ladder were most often between 55 and 75 cm. Large fish arrived earlier than small fish, females before males, and naturally recruited fish before stocked fish.