bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Ring Contraction Rearrangement of 2,5- and 3,6-Di-tert-butyl-3H-azepines to Pyridine Derivatives
Authors: Satake Kyosuke , Takaoka Koichi , Hashimoto Michiaki , Okamoto Hideki , Kimura Masaru , Morosawa Shiro 
Published: March 2006

Abstract
A new ring contraction reaction giving pyridine derivatives from 3,6- and 2,5-di-tert-butyl-3H-azepines was observed by a successive treatment with bromine and aqueous K2CO3. A plausible mechanism via azatropilium cation for the rearrangement was discussed based on the product’s distribution from respective 3H-azepines.
Benzoin Oxidation at Extreme Temperature by Bis (1,2-benzenedithiolato)dioxotungstate(VI) Complex: A Model Study for Hyperthermostable Tungsten Oxidoreductases
Authors: Oku Hiroyuki , Ueyama Norikazu , Nakamura Akira 
Published: March 2006

Abstract
The oxidation of benzoin by (NEt4)2[MVIO2(S2C6H4)2] (M = W (1) and Mo (2)) (S2C6H4 = 1,2-benzenedithiolate) was studied to clarify the role of tungsten ions in hyperthermostable enzymes. The reaction was analyzed by saturation kinetics, primary isotope effects of kH/kD, and the high temperture reaction at 100 °C. The rate constants were also compared with those of the selenolato analogs.
Synthesis and Characterization of [RuIIICl2(TPA)]+ (TPA = Tris(2-pyridylmethyl)amine) and Its Reactivity toward Alkane Functionalization
Authors: Kojima Takahiko 
Published: March 2006

Abstract
A new ruthenium(III) monomer complex having a tripodal ligand TPA was synthesized and characterized by X-ray crystallography and cyclic voltammetry. The title compound was revealed to catalyze alkane functionalization with m-chloroperbenzoic acid.
N-Oxidation of π-Conjugated Poly(heterocycle)s Containing Nitrogen and Electrically Conducting Properties of the N-Oxidized Products
Authors: Yamamoto Takakazu , Saito Nobuo 
Published: March 2006

Abstract
Oxidation of poly(quinoline-2,6-diyl) and its analogue with H2O2 gives N-oxidized products, which show dc conductivity of 2.3–3.2 × 10−6 S cm−1 without doping.
Stereocontrolled Elongation of a Functionalized Isoprene Unit on the E or Z Terminal Methyl of Terpenoids via N-Ylide Rearrangement of the Common Ammonium Salts
Authors: Honda Kiyoshi , Tabuchi Masayuki , Inoue Seiichi 
Published: March 2006

Abstract
Stereocontrolled elongation of a functionalized isoprene unit on the E or Z terminal methyl of terpenoids was achieved by the N-ylide rearrangement of the common ammonium salts under the selected reaction conditions. One of rearrangement products, all-(E)-sesquiterpene carboxylate was converted into β-sinensal, a component of the essential oil of Chinese orange. General aspects of these transformations were described.
Direct Observation of Hydrogen-Deuterium Exchange Reaction in Cobaloxime Crystal by Neutron Diffraction
Authors: Ohgo Yoshiki , Ohashi Yuji , Klooster Wim T , Koetzle Thomas F 
Published: March 2006

Abstract
After a crystal of [(R)-1-cyanoethyl-dα][(S)-1-phenylethylamine]bis(dimethylglyoximato)cobalt(III) was exposed to a xenon lamp for two weeks, its structure was analyzed by neutron diffraction. The deuterium atom was exchanged partially with one of the three methyl hydrogenes of the cyanoethyl group. The exchanged one is located closest to the deuterium atom.
Incorporation and Direct Electron Transfer of Chlorella Ferredoxin in the Bilayer Films of Cationic Lipids on Electrodes
Authors: Tominaga Masato , Yanagimoto Junko , Nassar Alaa-Eldin F , Rusling James F , Nakashima Naotoshi 
Published: March 2006

Abstract
Chlorella ferredoxin in solution was found to be incorporated into the cast films of ammonium lipids on basal plane pyrolytic graphite (BPG) electrodes via ion exchange between the lipid counter anion and negatively charged ferredoxin and was embedded in them without denaturation in a way to undergo direct electron transfer reactions with the electrode.
A Catalytic Amount of Titanium Tetrahalide as Promoter for the Addition Reaction of Silyl Ketene Acetals to Imines
Authors: Shimizu Makoto , Kume Kouji , Fujisawa Tamotsu 
Published: March 2006

Abstract
In the presence of a catalytic amount of TiBr4 or TiI4, the reaction of silyl ketene acetals with imines smoothly proceeds to give the corresponding β-amino esters in high yield with high anti-selectivity.
Unique Temperature Dependence of NMR and UV-visible Spectra of Poly(3-hexylthiophene-2,5-diyl) and Its Related Compounds
Authors: Yamamoto Takakazu 
Published: March 2006

Abstract
Lowering temperature of solutions of poly(3-hexylthiophene-2,5-diyl) P3HxTh below −10 – −20 °C leads to decrease in signal intensity of aromatic-H and α-CH2 in 1H-NMR spectrum. A shift of the π-π* absorption band to a longer wavelength by 26–60 nm is also observed. These results are accounted for by aggregation of P3HxTh through intermolecular interaction of the π-conjugated system.
Ruthenium Complexes Containing an Azobipyridine Ligand as Redox-Responsive Molecular Switches
Authors: Otsuki Joe , Sato Kinu , Tsujino Masayuki , Okuda Naotoshi , Araki Koji , Seno Manabu 
Published: March 2006

Abstract
Mononuclear and dinuclear ruthenium complexes containing an azobipyridine ligand serve as reversible redox-responsive molecular switches modulating electron localization in the excited-state that can be read out through the emission intensity.
Synthesis and Characterization of Novel Phosphido-Bridged Bimetallic Complexes of Molybdenum and Tungsten
Authors: Minato Makoto , Nakamura Takashi , Ito Takashi , Koizumi Takeaki , Osakada Kohtaro 
Published: March 2006

Abstract
The phosphido-bridged molybdenum and tungsten complexes [Cp2M(H)(μ-PPh2)M′(H)Cp2]+(OTs)− (M, M′ = Mo, W) were prepared and characterized. The X-ray crystallography for the complex (M = M′ = Mo) indicated that it has a novel symmetrical structure with regard to two metal centers.
Photodimerizations of 3-Methoxy-1,5-azulenequinone via Consecutive Pericyclic Reactions
Authors: Mori Akira , Kawakami Hiroko , Takeshita Hitoshi , Nozoe Tetsuo 
Published: March 2006

Abstract
3-Methoxy-1,5-azulenequinone gave dimers when irradiated with a high-pressure mercury lamp. The product distribution was dependent on the polarity of the solvent. In a polar solvent, a head-to-head dimer was predominant whereas a head-to-tail dimer was mainly formed in a nonpolar solvent.
Boundary‐layer friction in midlatitude cyclones
Authors: Adamson D. S. , Belcher S. E. , Hoskins B. J. , Plant R. S. 
Published: February 2006

AbstractResults from an idealized three‐dimensional baroclinic life‐cycle model are interpreted in a potential vorticity (PV) framework to identify the physical mechanisms by which frictional processes acting in the atmospheric boundary layer modify and reduce the baroclinic development of a midlatitude storm. Considering a life cycle where the only non‐conservative process acting is boundary‐layer friction, the rate of change of depth‐averaged PV within the boundary layer is governed by frictional generation of PV and the flux of PV into the free troposphere. Frictional generation of PV has two contributions: Ekman generation, which is directly analogous to the well‐known Ekman‐pumping mechanism for barotropic vortices, and baroclinic generation, which depends on the turning of the wind in the boundary layer and low‐level horizontal temperature gradients. It is usually assumed, at least implicitly, that an Ekman process of negative PV generation is the mechanism whereby friction reduces the strength and growth rates of baroclinic systems. Although there is evidence for this mechanism, it is shown that baroclinic generation of PV dominates, producing positive PV anomalies downstream of the low centre, close to developing warm and cold fronts. These PV anomalies are advected by the large‐scale warm conveyor belt flow upwards and polewards, fluxed into the troposphere near the warm front, and then advected westwards relative to the system. The result is a thin band of positive PV in the lower troposphere above the surface low centre. This PV is shown to be associated with a positive static stability anomaly, which Rossby edge wave theory suggests reduces the strength of the coupling between the upper‐ and lower‐level PV anomalies, thereby reducing the rate of baroclinic development. This mechanism, which is a result of the baroclinic dynamics in the frontal regions, is in marked contrast with simple barotropic spin‐down ideas. Finally we note the implications of these frictionally generated PV anomalies for cyclone forecasting. Copyright © 2006 Crown copyright
Equatorial waves in the lower stratosphere. I: A novel detection method
Authors: Tindall J. C. , Thuburn J. , Highwood E. J. 
Published: February 2006

AbstractWavenumber–frequency spectral analysis and linear wave theory are combined in a novel method to quantitatively estimate equatorial wave activity in the tropical lower stratosphere. The method requires temperature and velocity observations that are regularly spaced in latitude, longitude and time; it is therefore applied to the ECMWF 15‐year re‐analysis dataset (ERA‐15). Signals consistent with idealized Kelvin and Rossby‐gravity waves are found at wavenumbers and frequencies in agreement with previous studies. When averaged over 1981–93, the Kelvin wave explains approximately 1 K2 of temperature variance on the equator at 100 hPa, while the Rossby‐gravity wave explains approximately 1 m2s−2 of meridional wind variance. Some inertio‐gravity wave and equatorial Rossby wave signals are also found; however the resolution of ERA‐15 is not sufficient for the method to provide an accurate climatology of waves with high meridional structure. Copyright © 2006 Royal Meteorological Society
Equatorial waves in the lower stratosphere. II: Annual and interannual variability
Authors: Tindall J. C. , Thuburn J. , Highwood E. J. 
Published: February 2006

AbstractThe annual and interannual variability of idealized, linear, equatorial waves in the lower stratosphere is investigated using the temperature and velocity fields from the ECMWF 15‐year re‐analysis dataset. Peak Kelvin wave activity occurs during solstice seasons at 100 hPa, during December–February at 70 hPa and in the easterly to westerly quasi‐biennial oscillation (QBO) phase transition at 50 hPa. Peak Rossby‐gravity wave activity occurs during equinox seasons at 100 hPa, during June–August/September–November at 70 hPa and in the westerly to easterly QBO phase transition at 50 hPa. Although neglect of wind shear means that the results for inertio‐gravity waves are likely to be less accurate, they are still qualitatively reasonable and an annual cycle is observed in these waves at 100 hPa and 70 hPa. Inertio‐gravity waves with n=1 are correlated with the QBO at 50 hPa, but the eastward inertio‐gravity n=0 wave is not, due to its very fast vertical group velocity in all background winds. The relative importance of different wave types in driving the QBO at 50 hPa is also discussed. The strongest acceleration appears to be provided by the Kelvin wave while the acceleration provided by the Rossby‐gravity wave is negligible. Of the higher‐frequency waves, the westward inertio‐gravity n=1 wave appears able to contribute more to the acceleration of the 50 hPa mean zonal wind than the eastward inertio‐gravity n=1 wave. Copyright © 2006 Royal Meteorological Society
Assimilation of stratospheric ozone from MIPAS into a global general‐circulation model: The September 2002 vortex split
Authors: Geer A. J. , Peubey C. , Bannister R. N. , Brugge R. , Jackson D. R. , Lahoz W. A. , Migliorini S. , O'Neill A. , Swinbank R. 
Published: February 2006

AbstractOzone and temperature profiles from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) have been assimilated, using three‐dimensional variational assimilation, into a stratosphere‐troposphere version of the Met Office numerical weather‐prediction system. Analyses are made for the month of September 2002, when there was an unprecedented split in the southern hemisphere polar vortex. The analyses are validated against independent ozone observations from sondes, limb‐occultation and total column ozone satellite instruments. Through most of the stratosphere, precision varies from 5 to 15%, and biases are 15% or less of the analysed field. Problems remain in the vortex and below the 60 hPa level, especially at the tropopause where the analyses have too much ozone and poor agreement with independent data. Analysis problems are largely a result of the model rather than the data, giving confidence in the MIPAS ozone retrievals, though there may be a small high bias in MIPAS ozone in the lower stratosphere. Model issues include an excessive Brewer‐Dobson circulation, which results both from known problems with the tracer transport scheme and from the data assimilation of dynamical variables. The extreme conditions of the vortex split reveal large differences between existing linear ozone photochemistry schemes. Despite these issues, the ozone analyses are able to successfully describe the ozone hole split and compare well to other studies of this event. Recommendations are made for the further development of the ozone assimilation system. Copyright © 2006 Royal Meteorological Society. D. R. Jackson and R. Swinbank contributions are Crown copyright
Entropy sources in a dynamical core atmosphere model
Authors: Woollings Tim , Thuburn John 
Published: February 2006

AbstractNumerical atmosphere models are not generally constructed to ensure accurate treatment of entropy, but little is known about the significance of the resulting errors. This paper examines the entropy changes during a baroclinic wave simulation in a typical dynamical core model, specifically a σ‐coordinate spectral model, which includes scale‐selective dissipation terms in the form of a numerical hyperdiffusion. Lagrangian entropy conservation is found to be badly represented, with numerical transport errors resulting in cross‐isentrope mass fluxes which are of the same size as those associated with some real diabatic processes. In a global average, the total entropy increases at a rate of just 0.5 mW m−2K−1. This, however, is seen to be the residual of two opposing numerical effects which are several times larger, namely the destruction of entropy by dispersion and Gibbs errors, and its creation by diffusion. The entropy generated by diffusion is shown to be remarkably insensitive to the details of the diffusion scheme. This leads us to hypothesize that the entropy source from diffusion is determined by the rate at which small scales are generated by the deformation field of the large‐scale flow so that, while the diffusion mechanism is clearly unrealistic, the magnitude of the entropy source is, we argue, representative of that generated by physical dissipative processes in the real atmosphere. Even in this simple model it is not possible to quantify precisely the different entropy sources and sinks which combine to give the overall entropy change. However, we can say that if there is a systematic spurious entropy source in this model, then it is small, i.e. of size 0.5 mW m−2K−1 or smaller. Copyright © 2006 Royal Meteorological Society
Estimating vertical velocity and radial flow from Doppler radar observations of tropical cyclones
Authors: Lee J. L. , Lee W. C. , Macdonald A. E. 
Published: February 2006

AbstractThe mesoscale vorticity method (MVM) is used in conjunction with the ground‐based velocity track display (GBVTD) to derive the inner‐core vertical velocity from Doppler radar observations of tropical cyclone (TC) Danny (1997). MVM derives the vertical velocity from vorticity variations in space and in time based on the mesoscale vorticity equation. The use of MVM and GBVTD allows us to derive good correlations among the eye‐wall maximum wind, bow‐shaped updraught and echo east of the eye‐wall in Danny. Furthermore, we demonstrate the dynamically consistent radial flow can be derived from the vertical velocity obtained from MVM using the wind decomposition technique that solves the Poisson equations over a limited‐area domain. With the wind decomposition, we combine the rotational wind which is obtained from Doppler radar wind observations and the divergent wind which is inferred dynamically from the rotational wind to form the balanced horizontal wind in TC inner cores, where rotational wind dominates the divergent wind. In this study, we show a realistic horizontal and vertical structure of the vertical velocity and the induced radial flow in Danny's inner core. In the horizontal, the main eye‐wall updraught draws in significant surrounding air, converging at the strongest echo where the maximum updraught is located. In the vertical, the main updraught tilts vertically outwards, corresponding very well with the outward‐tilting eye‐wall. The maximum updraught is located at the inner edge of the eye‐wall clouds, while downward motions are found at the outer edge. This study demonstrates that the mesoscale vorticity method can use high‐temporal‐resolution data observed by Doppler radars to derive realistic vertical velocity and the radial flow of TCs. The vorticity temporal variations crucial to the accuracy of the vorticity method have to be derived from a high‐temporal‐frequency observing system such as state‐of‐the‐art Doppler radars. Copyright © 2006 Royal Meteorological Society
Limited‐area model error statistics over Western Africa: Comparisons with midlatitude results
Authors: Montmerle. Thibaut , Lafore Jean‐Philippe , Berre Loïk , Fischer Claude 
Published: February 2006

AbstractIn the context of the African Monsoon Multidisciplinary Analyses experiment, a new forecast error covariance matrix has been computed for data assimilation purposes, using the spectral mesoscale limited‐area model ALADIN. The so‐called ‘lagged NMC’ method has been applied using sets of forecast differences performed during the summer overWestern Africa. Multiple linear regressions on these differences have been computed in order to determine statistics and balance features between forecast errors of divergence, vorticity, specific humidity, temperature and surface pressure. The resulting auto‐ and cross‐covariances display very different features from those obtained over Western Europe, and they reflect the uncertainty of forecasting the main meteorological features of the West African Monsoon. While the geostrophic coupling with vorticity is predominant in midlatitudes, over western Africa the main mass/wind couplings instead involve divergence in the low troposphere and below the tropopause. The couplings between e.g. low‐level humidity, temperature and divergence are strengthened over Africa. The vertical correlations are broader for increasing horizontal scales but in a much less pronounced manner than in midlatitudes. The mean vertical correlations for humidity are much more localized in the low troposphere over Africa. Copyright © 2006 Royal Meteorological Society
The impact of urban areas on weather
Authors: Collier C. G. 
Published: February 2006

AbstractThe industrial revolution led to a rapid development of urban areas. This has continued unremittingly over the last 200 years or so. In most urban areas the surface properties are heterogeneous, which has significant implications for energy budgets, water budgets and weather phenomena within the part of the earth's atmosphere that humans live. In this paper I discuss the structure of the planetary boundary layer, confining our analysis to the region above the rooftops (canopy layer) up to around the level where clouds form. It is in this part of the atmosphere that most of the weather impacting our lives occurs, and where the buildings of our cities impact the weather.In this review, observations of the structure of the urban atmospheric boundary layer are discussed. In particular the use of Doppler lidar provides measurements above the canopy layer. The impact of high‐rise buildings is considered.Urban morphology impacts energy fluxes and airflow leading to phenomena such as the urban heat island and convective rainfall initiation. I discuss in situ surface‐based remote sensing and satellite measurements of these effects. Measurements have been used with simple and complex numerical models to understand the complexity and balance of the interactions involved. Cities have been found to be sometimes up to 10 degC warmer than the surrounding rural areas, and to cause large increases in rainfall amounts. However, there are situations in which urban aerosol may suppress precipitation.Although much progress has been made in understanding these impacts, our knowledge remains incomplete. These limitations are identified. As city living becomes even more the norm for large numbers of people, it is imperative that we ensure that urban effects on the weather are included in development plans for the built environment of the future. Copyright © 2006 Royal Meteorological Society
Some numerical properties of approaches to physics–dynamics coupling for NWP
Authors: Dubal Mark , Wood Nigel , Staniforth Andrew 
Published: February 2006

AbstractAt the present time there exist a number of different approaches to the problem of coupling parametrized physical processes to the dynamical core in operational numerical weather‐prediction (NWP) and climate models. Motivated by the various strategies in use, some idealized representative coupling schemes are constructed and subsequently analysed using a methodology in which the physics and dynamics terms are represented in a simplified way. Particular numerical properties of the idealized schemes which are of interest are the ability to capture correct steady‐state solutions and to be second‐order accurate in time. In general, the schemes require specific choices for the time‐differencing of certain coupled processes if correct steady‐state solutions are to be obtained. This has implications for the overall numerical stability of a coupling strategy. An alternative physics–dynamics coupling approach is then described and analysed. A multiple‐sweep predictor–corrector coupling scheme is shown to capture the correct steady‐state solution and to allow for second‐order accuracy, provided that the convective process is coupled explicitly. This approach has a number of advantages over those currently used in operational NWP models. Copyright © 2006 Crown copyright
Intense convective systems in West Africa and their relationship to the African easterly jet
Authors: Mohr Karen I. , Thorncroft Chris D. 
Published: February 2006

AbstractFor May–September 1998, convective systems in West Africa were identified from observations by the Tropical Rainfall Measuring Mission satellite Microwave Imager at 85 GHz. Using re‐analysis data, the 10‐day average position of the African easterly jet (AEJ) was diagnosed from the 700 hPa zonal winds. The distance from each convective system's centroid to the axis of the AEJ was calculated. Each convective system's minimum brightness temperatures were ranked so that intense convective systems were defined as those in the 10th percentile or lower. The weak (>10th percentile) and intense convective systems were represented statistically as two separate populations, the weak by the skewed Gumbel distribution and the intense by the normal distribution. From May to August, the peak in activity of weak convective systems remained south of 10°N but shifted east of 10°E. The peak in activity of the intense convective systems followed the seasonal migration of the AEJ northwards and became increasingly separate from the peak in activity of weak convective systems. The majority of both weak and intense convective systems occurred within 0.50° of high terrain. The high convective available potential energy, high‐shear AEJ environment in the vicinity of high terrain appeared to have the greatest probability of generating intense convective systems in the study area. Copyright © 2006 Royal Meteorological Society