bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Diastereo‐ and Enantioselective Aldol Reactions in Common Organic Solvents Using N‐Arylprolinamides as Organocatalysts with Enhanced Acidity
Authors: Moorthy Jarugu Narasimha , Saha Satyajit 
Published: December 2008

AbstractA broad set of N‐arylprolinamides 1–8 with increasing NH acidity and steric crowding has been synthesized and its catalytic activity explored for enantioselective aldol reactions. In DMF containing 10 mol‐% of TFA, all arylamides are found to catalyze the reaction between cyclohexanone and a variety of electrophilic aldehydes leading to aldols in excess of 90 % yield and >95 % enantioselectivity. The perfluorophenyl catalyst 8 is found to perform best with a broad substrate scope as compared to all other N‐arylamides 1–7. It is shown that 8 can indeed be employed in highly nonpolar as well as polar solvents including brine to afford high yields of aldols with excellent diastereo‐ as well as enantioselectivity. The results observed for 8 are amongst the best reported so far for prolinamides that do not contain additional stereogenic center(s) and hydrogen‐bonding site(s). The molecular structures of 7 and 8, determined by X‐ray crystallography and presumed to reflect the most stable conformations, reveal a notable difference in the conformations of the N‐aryl rings; the aryl ring exhibits tendency to lie coplanar with the amide functionality in the case of 7, while the perfluorophenyl ring twists almost orthogonally with respect to the plane of the amide of functionality in 8. The superior performance of the latter is attributed to, in addition to the enhanced NH acidity, the tendency of the perfluorophenyl ring to lie orthogonally to the amide group, which may facilitate a stronger binding of the electrophilic aldehyde via hydrogen bonding in the transition state.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Stereoselectivity of Glycosylation May Change During the Reaction Course: Highly α‐Stereoselective Sialylation Achieved by Supramer Approach
Authors: Kononov Leonid O. , Malysheva Nelly N. , Orlova Anna V. 
Published: December 2008

AbstractThe stereoselectivity of NIS/TfOH‐promoted glycosylation with O‐acetylated N‐acetylneuraminic acid phenyl thioglycoside was found to be dependent on the reaction time. Highly α‐stereoselective sialylation (27:1 anomer ratio) was achieved by decreasing the reaction time (from 3 h to 15 min) and by adding a non‐reacting compound (1 equiv.) capable of modifying the structure of hydrogen‐bonded supramolecular aggregates (supramers) of the glycosyl donor. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
The role of floodplains in attenuating contaminated sediment fluxes in formerly mined drainage basins
Authors: Dennis Ian A. , Coulthard Tom J. , Brewer Paul , Macklin Mark G. 
Published: December 2008

AbstractMany upland river catchments in the UK have been historically mined for metals such as lead (Pb) and zinc (Zn), and as part of the mining process large quantities of metal contaminated sediment were released into the river system. The levels of sediment associated heavy metal contamination in river systems are largely controlled by the volumes of contaminated sediment released into the river and fluvial processes (e.g. erosion and deposition). As a consequence, the contamination patterns are often highly variable, which can make it difficult to create accurate assessments of the volumes of contaminated sediment remaining within the system. This paper uses a combination of techniques to establish the volumes of metal contaminated sediment remaining within the River Swale, UK. Firstly, using detailed field sampling and a geographical information system (GIS), it estimates the volumes of sediment remaining within one formerly mined tributary (Gunnerside Beck) which is then extrapolated to represent the contaminant volumes on other tributaries of the River Swale. Secondly, combining fresh field data with a range of existing data, volumes of contaminated sediment on the main stream of the River Swale are established. This two tier approach shows that significant volumes of contaminated sediment remain within the River Swale, with over 32 000 tonnes of Pb within the mined tributaries and 123 000 tonnes within the main channel belt of the River Swale itself. This represents approximately 28% of the Pb produced in the Swale catchment. Given these volumes and present day rates of removal, it may take over 5000 years for all of the metal rich sediment to be removed from the catchment. If the contaminated sediment is used as a tracer, present day rates of reworking of floodplain sediment can be calculated to be 0·02% per year. Copyright © 2008 John Wiley & Sons, Ltd.
Transmission reservation and transactions modeling in electricity markets
Authors: Hao Shangyou , Shirmohammadi Dariush 
Published: January 2009

AbstractSignificant progresses have been made in developing analytical models for electricity markets to schedule and price supply and demand resources. However, transmission‐specific service products such as bilateral energy transactions, transmission capacity reservations, and transmission rights transactions have been left largely as the by‐product of market development. For instance, a bilateral transaction across multiple interconnected systems is normally preconditioned on acquiring transmission capacity reservation in market or non‐market systems. To be economically efficient, such a transaction should be considered simultaneously with the aggregated use from all market participants in order to price the true transmission costs. In most of today's electricity markets, it is difficult for market participants to directly schedule an economic transmission capacity reservation, or an economic purchase of transmission rights from markets.This paper presents a new optimization formulation for forward electricity markets, extending traditional market capabilities from the scheduling and pricing of energy resources to the scheduling of economic transmission transactions and transmission capacity reservation by considering the economic costs of transmission. Examples are provided to illustrate the applications and features of the proposed model. The proposed model helps markets improve the utilization of transmission. It may also be used to manage cross‐border transactions of market and non‐market systems reducing seams between them. Copyright © 2008 John Wiley & Sons, Ltd.
An improved leader progression model for the analysis of the shielding performance of 1000 kV UHVAC transmission lines
Authors: Wei Bengang , Fu Zhengcai , Yuan Haiyan , Du Patrick Y. 
Published: December 2008

AbstractThis paper presents an improved leader progression model (LPM). The model uses the proposed leader inception criterion for the analysis of lightning shielding performance of UHVAC transmission lines. It focuses on the discussion of the leader inception voltage of bundle conductors. The improved LPM is validated on 500 kV EHV transmission lines. The shielding performance of a UHVAC transmission line to be constructed in a Chinese Test Line Project is then evaluated. The results indicate that the power frequency operating voltage and the bundle conductor configuration have a greater influence on the shielding failure flashover rate (SFFOR) of 1000 kV UHV lines than that of 500 kV EHV lines. It is found that the UHVAC line to be built will not cause trip accidents due to shielding failure in flat terrain. In broken terrain, the SFFOR is only 0.0012 times/100 km·year, which is less than the design limit. Copyright © 2008 John Wiley & Sons, Ltd.
Integral equations method for the analysis and design of ELF conductive and magnetic shields
Authors: Lucca Giovanni 
Published: December 2008

AbstractThe need to shield ELF (extremely low frequency) magnetic fields generated by power and industrial installations arises for two main reasons: the first one is a typical EMC (electromagnetic compatibility) problem related to possible interference among electric and electronic devices while the second one is related to potential health effects due to magnetic field exposure. Different techniques exist to reduce the magnetic field mainly depending on the kind of source considered; here we treat only the shielding action offered by long and metallic structures like slabs, sheets, and foils with respect to the field produced by long sources like power cables, bus‐bars, and wires. In particular, we focus our attention on magnetic metallic shields where the shielding action is due to both ‘magnetic flux shunting’ and ‘eddy current cancellation’ mechanisms. From the design point of view, it is useful to have at disposal a calculation tool able to predict the magnetic field reduction, in a given region of space, as a function of the shield characteristics (geometry, material) and source characteristics (conductors disposition, distance from the shield). The typical calculation technique used in this kind of problem is based on the finite elements method (FEM) that is broadly described in the technical literature. Here, we want to propose a different approach that is based on integral equations (IE) and is able to model shields made by materials like iron, steel, and mumetal having both conductive and magnetic properties; nevertheless, as special cases, the algorithm is also able to deal with purely conductive shields like copper and aluminium, (frequently used in applications) where only the eddy current shielding action exists, and with purely magnetic shields, under the action of a d.c. source, where only the magnetic flux shunting effect is present. The main hypothesis that is necessary to adopt in the model is the linear behaviour of the magnetic material; such hypothesis is certainly reasonable in many real situations where the material is far from saturation. Copyright © 2008 John Wiley & Sons, Ltd.
A high‐resolution relative time scale for the Viséan Stage (Carboniferous) of the Kulm Basin (Rhenish Mountains, Germany)
Authors: Korn Dieter , Kaufmann Bernd 
Published: December 2008

AbstractThe Viséan (Carboniferous) sedimentary succession of the basinal Kulm facies (Rhenish Mountains) was investigated in detail in order to achieve a high‐resolution stratigraphic subdivision and correlation. Additionally, the ranges of fossil index taxa (ammonoids), fossil marker beds, volcaniclastic horizons and sedimentary features (e.g. colour changes) were integrated in the correlation. As a result, a comprehensive database was compiled, which contains 190 stratigraphic events of the Viséan interval of this area.Several sections are almost completely composed of shales, which are regarded to represent a slow but constant basinal background sedimentation of the Kulm facies. The thickness of lithological homogeneous sections thus indicates an approximately linear record of time and the average thicknesses of biozones and positions of stratigraphic events can easily be calculated from the compiled database. The result is an approximately time‐linear biostratigraphic scale for the Viséan Stage of the Kulm Basin. Given a numerical length of the Viséan Stage of ca. 19 Ma, 190 stratigraphic events give a mean resolution of 100 000 years. This is unique in Palaeozoic stratigraphy. Copyright © 2008 John Wiley & Sons, Ltd.
P2 receptor‐mediated stimulation of the PI3‐K/Akt‐pathway in vivo
Authors: Franke H. , Sauer C. , Rudolph C. , Krügel U. , Hengstler J. G. , Illes P. 
Published: December 2008

AbstractATP acts as a growth factor as well as a toxic agent by stimulating P2 receptors. The P2 receptor‐activated signaling cascades mediating cellular growth and cell survival after injury are only incompletely understood. Therefore, the aim of the present study was to identify the role of the phosphoinositide 3 kinase (PI3‐K/Akt) and the mitogen‐activated protein kinase/extracellular signal regulated protein kinase (MAPK/ERK) pathways in P2Y receptor‐mediated astrogliosis after traumatic injury and after microinfusion of ADPβS (P2Y1,12,13 receptor agonist) into the rat nucleus accumbens (NAc). Mechanical damage and even more the concomitant treatment with ADPβS, enhanced P2Y1 receptor‐expression in the NAc, which could be reduced by pretreatment with the P2X/Y receptor antagonist PPADS. Quantitative Western blot analysis indicated a significant increase in phosphorylated (p)Akt and pERK1/2 2 h after ADPβS‐microinjection. Pretreatment with PPADS or wortmannin abolished the up‐regulation of pAkt by injury alone or ADPβS‐treatment. The ADPβS‐enhanced expression of the early apoptosis marker active caspase 3 was reduced by PPADS and PD98059, but not by wortmannin. Multiple immunofluorescence labeling indicated a time‐dependent expression of pAkt and pMAPK on astrocytes and neurons and additionally the colocalization of pAkt, pMAPK, and active caspase 3 with the P2Y1 receptor especially at astrocytes. In conclusion, the data show for the first time the involvement of PI3‐K/Akt‐pathway in processes of injury‐induced astroglial proliferation and anti‐apoptosis via activation of P2Y1 receptors in vivo, suggesting specific roles of P2 receptors in glial cell pathophysiology in neurodegenerative diseases. © 2008 Wiley‐Liss, Inc.
The Alzheimer's disease drug memantine increases the number of radial glia‐like progenitor cells in adult hippocampus
Authors: Namba Takashi , Maekawa Motoko , Yuasa Shigeki , Kohsaka Shinichi , Uchino Shigeo 
Published: December 2008

AbstractNew neurons are continuously generated in the hippocampus of the adult mammalian brain, and N‐methyl‐D‐aspartate receptor (NMDA‐R) antagonists have been found to increase the number of newly generated neurons in the dentate gyrus (DG) of the adult hippocampus. In this study, we examined the effect of memantine, an NMDA‐R antagonist that is clinically used for the treatment of Alzheimer's disease, on primary progenitor cells exhibiting a radial glia‐like (RGL) morphology in the DG. We injected 3‐month‐old mice with memantine (50 mg/kg body weight, intraperitoneally [i.p.]); 3 days later, we injected the mice with 5‐bromo‐2‐deoxyuridine (BrdU; 75 mg/kg body weight, i.p.). We then counted the number of BrdU‐labeled RGL progenitor cells in the DG 1 or 7 days after the BrdU‐injection. The number of BrdU‐labeled RGL progenitor cells had increased significantly by 5.1‐fold on day 1 and by 13.7‐fold on day 7 after BrdU‐injection. Immunohistochemical staining revealed that the BrdU‐labeled RGL progenitor cells expressed two primary progenitor cell marker proteins, nestin and Sox2. These results clearly demonstrated that memantine promotes the proliferation of RGL progenitor cells. We also found that memantine increased the ratio of horizontally aligned RGL progenitor cells, which are probably produced by symmetric division. These findings suggest that memantine increases the proliferation of primary progenitor cells and expands the primary progenitor cell pool in the adult hippocampus by stimulating symmetric division. © 2008 Wiley‐Liss, Inc.
Patients' attitudes of dementia screening across the Atlantic
Authors: Justiss Michael D. , Boustani Malaz , Fox Chris , Katona Cornelius , Perkins Anthony J. , Healey Patrick J. , Sachs Greg , Hui Siu , Callahan Christopher M. , Hendrie Hugh C. , Scott Emma 
Published: December 2008

AbstractBackgroundDementia is a common and growing global public health problem. It leads to a high burden of suffering for society with an annual cost of $100 billion in the US and $10 billion in the UK. New strategies for both treatment and prevention of dementia are currently being developed. Implementation of these strategies will depend on the presence of a viable community or primary care based dementia screening and diagnosis program and patient acceptance of such a program.ObjectiveTo compare the acceptance, perceived harms and perceived benefits of dementia screening among older adults receiving their care in two different primary health care systems in two countries.DesignA Cross‐sectional study.SettingPrimary care clinics in Indianapolis, USA and Kent, UK.ParticipantsA convenience sample of 245 older adults (Indianapolis, n = 125; Kent, n = 120).OutcomesAcceptance of dementia screening and its perceived harms and benefits as determined by a 52‐item questionnaire (PRISM‐PC questionnaire).ResultsFour of the five domains were significantly different across the two samples. The UK sample had significantly higher dementia screening acceptance scores (p < 0.05); higher perceived stigma scores (p < 0.05); higher perceived loss of independence scores (p < 0.01); and higher perceived suffering scores (p < 0.01) than the US sample. Both groups perceived dementia screening as beneficial (p = 0.218). After controlling for prior experience with dementia, acceptance and stigma were marginalized.ConclusionsOlder adults attending primary care clinics across the Atlantic value dementia screening but have significant concerns about dementia screening although these concerns differed between the two countries. Low acceptance rates and high rates of perceived harms might be a significant barrier for the introduction of treatment or preventive methods for dementia in the future. Copyright © 2008 John Wiley & Sons, Ltd.
Climate–river flow relationships across montane and lowland environments in northern Europe
Authors: Kingston Daniel G. , Hannah David M. , Lawler Damian M. , McGregor Glenn R. 
Published: December 2008

AbstractTo assess hydrological sensitivity to climate variability, improved understanding is needed of the process cascade linking large‐scale climate to river flow. For northern Europe such knowledge is limited, and is further complicated by mountainous terrain. This research gap is addressed through composite analysis of large‐scale climate drivers of monthly high and low river flow across northern Europe for the period 1968–1997. As an organizational framework for this investigation, the study is performed on a regional basis, using cluster analysis for identification of river flow regions. Results of the composite analysis show that the occurrence of high and low flow across northern Europe is associated with large‐scale patterns of temperature and precipitation variation. Especially in winter, these patterns are linked to changes in large‐scale geopotential height and wind fields, and in particular variation in the Azores High and Icelandic Low atmospheric centres of action. This is suggestive of a link between the North Atlantic Oscillation (NAO) and river flow, but is too complex to be described solely in terms of the NAO. Outside the winter half‐year, an inverse climate–river flow relationship is found between northern and southern Scandinavian river flow regions. This relationship is associated with differences in the relative contribution of meltwater to river flow between these regions, their latitudinal separation and orographic effects on precipitation distribution. Copyright © 2008 John Wiley & Sons, Ltd.
Glaciermelt of a small basin contributing to runoff under the extreme climate conditions in the summer of 2003
Authors: Koboltschnig Gernot R. , Schöner Wolfgang , Holzmann Hubert , Zappa Massimiliano 
Published: December 2008

AbstractThis paper gives an overview on the regional hydrological impact of the heatwave, which affected Europe in the summer of 2003. We investigated the small, glacierized Goldbergkees basin in the Austrian Alps, which is situated directly beneath the high Alpine Sonnblick observatory (3106 m a.s.l.). We analysed the long‐term air temperature time series and quantified the extreme anomaly of the mean summer (JJA) air temperature for 4·4 times the standard deviation of the long‐term mean (1886–2000). The mean summer air temperature was 4·7 °C. In 2003, the solid fraction of precipitation was only 35%. This was the lowest value observed from 1927 to 2005. To quantify the impact of the warm temperatures on the Goldbergkees glacier positive degree‐day sums were calculated. The ‘hot’ conditions of the summer of 2003 rapidly melted the snow covering the glacier and finally melted the ice beneath. The winter balance of the Goldbergkees did not show anomalies. The specific net balance of Goldbergkees was − 1·8 m water equivalent (w.e.) for the 2002/2003 period and has been the most negative observed. Snowmelt was accelerated by low albedo, which was a result of Sahara dust‐falls. The hydrological response unit (HRU)‐based model PREVAH was applied to simulate hourly runoff, which was observed at the outlet of this small and topographically heterogeneous basin. All components contributing to runoff were separated. The model was driven using hourly meteorological data gained from the Sonnblick observatory. Snow‐ and icemelt were modelled based on an advanced temperature index‐based approach. The model was validated using observed glacier mass balance data. The maximum simulated icemelt rate was 2·7 mm/h (4·9 mm/h assigned to the glacier surface). During August 2003, glaciermelt contributed 81% to the total runoff. Copyright © 2008 John Wiley & Sons, Ltd.
Analyses of seasonal snow disappearance in an alpine valley from micro‐ to meso‐scale (Loetschental, Switzerland)
Authors: Schmidt S. , Weber B. , Winiger M. 
Published: December 2008

AbstractThe seasonal snow cover duration depends on climatic conditions, vegetation and topography. Conventional approaches of snow cover monitoring, based on point measurements or remote sensing techniques, are not suitable for meso‐scale spatial and temporal observations, or for analyses of the snow extent. However, these meso‐scale analyses are the basis for an understanding of ecological, hydrological and climatic systems in high mountains. Therefore, new approaches are required to monitor and to analyse the meso‐scale spatial snow cover distribution.In the presented study, we used 30 point measurement data and terrestrial images, which were taken by two digital cameras. The micro‐scale point measurements show the snow cover duration in several topographical positions. The terrestrial images monitor the variation of snow extent on a northwest and southeast‐facing slope. They provide a spatial resolution of 10 m, and due to bad weather conditions, a temporal resolution of 5 days. Both, the micro‐ as well as meso‐scale data enabled statistical analyses of the impact of topography on snow cover duration.The combination of terrestrial images and point measurements facilitated the verification of the representativeness of point measurements as well as their extrapolation capabilities. One important conclusion of the presented study is that snow cover duration can be explained just partly by topographical features. Copyright © 2008 John Wiley & Sons, Ltd.