bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer‐aided design of selective COX‐2 inhibitors: comparative molecular field analysis and docking studies of some 3,4‐diaryloxazolone derivatives
Authors: Desiraju G. R. , Sarma J. A. R. P. , Raveendra D. , Gopalakrishnan B. , Thilagavathi R. , Sobhia M. E. , Subramanya H. S.
Published: August 2002

The recent discovery of a second, inducible isoform of cyclooxygenase, COX‐2, has stimulated the search for highly selective non‐steroidal anti‐inflammatory drugs (NSAIDs). These NSAIDs have the ability to treat pain and inflammation caused by arthritis with less risk of gastrointestinal or renal toxicity. We report here the results of 3D‐quantitative structure–activity relationship and docking studies, performed on a series of 3,4‐diaryloxazolones. Comparative moleculer field analysis studies provided a good model with cross‐validated and conventional r2 values of 0.688 and 0.969 respectively for 24 analogues in the training set with six components. Docking studies with both COX‐1 and COX‐2 indicate good selectivity for COX‐2. The binding energies between COX‐2 and some of the most active oxazolones are comparable to those of celecoxib or rofecoxib. These compounds adopt similar orientations and form similar sets of hydrogen bonds involving the sulfonyl group of the ligand and His 90, Leu 352, Ser 353, Arg 513, Phe 518 and Ser 530 residues of the receptor. Copyright © 2001 John Wiley & Sons, Ltd.
Catalysis of poly(urethane imidine) copolymer formation from amine‐blocked isocyanate and bisphthalide
Authors: Iyer N. Padmanabha , Gnanarajan T. Philip , Radhakrishnan Ganga
Published: August 2002

The catalysis of imidine formation between an amine‐blocked polyurethane prepolymer and bisphthalide was studied with a series of metal alkoxides, phenoxides, and organotin compounds and tertiary amines. The carbon dioxide released during the reaction was followed for monitoring of the reaction. The metal alkoxides and phenoxides catalyzed the imidine formation reaction but did not catalyze the deblocking reaction, whereas the organotin compounds and tertiary amines showed no catalytic activity in the reaction between isocyanate and phthalide. With tin catalysts, the imidine formation reaction depended on the deblocking of the blocked prepolymer, but it was independent of deblocking with amine catalysts. The resultant poly(urethane imidine) copolymers were characterized with Fourier transform infrared, 1H NMR, 13C NMR, gel permeation chromatography, and thermogravimetric analysis techniques. The thermal stability of polyurethane increased significantly with the incorporation of imidine groups. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4236–4242, 2001
Preparation of aromatic polyimides highly soluble in conventional solvents
Authors: Huang Wei , Yan Deyue , Lu Qinghua , Tao Ping
Published: August 2002

Several highly soluble polyimides were synthesized from various aromatic tetracarboxylic dianhydrides and an aromatic diamine containing tert‐butyl pendent groups [4,4′‐methylenebis(2‐tert‐butylaniline)]. All the polyimides showed excellent solubility in common solvents such as chloroform, tetrahydrofuran, and dioxane at room temperature. The number‐average molecular weight ranged from 3.6 × 104 to 1.3 × 105 according to gel permeation chromatography relative to a polystyrene standard, and the polydispersity index was between 1.9 and 2.5. The glass‐transition temperatures of the resulting polyimides ranged from 213 to 325 °C, as measured by differential scanning calorimetry, and little weight loss was observed up to 450 °C in N2 by thermogravimetric analysis. These experimental data indicated that the tert‐butyl pendent groups reduced the interactions among polymer chains to improve their solubility in organic solvents without the loss of thermal stability. Transparent and flexible films of these polyimides were obtained via casting from solution. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 229–234, 2002
Particle formation in interval III of the emulsion polymerization of styrene with aerosol‐MA as an emulsifier
Authors: Sajjadi Shahriar
Published: August 2002

Particle nucleation in the seeded emulsion polymerization of styrene in the presence of Aerosol‐MA emulsifier micelles and in the absence of monomer droplets (interval III) was investigated. The seed particles were swollen with different amounts of the styrene monomer before the experiments. A larger number of polymer particles formed in interval III than in the corresponding seeded batch operation in the presence of monomer droplets. The increase in the number of particles could be attributed to the reduced rate of growth of new particles, which retarded the depletion of emulsifier micelles. The number of secondary particles initially increased with the initial polymer weight ratio in the seed particles (wp0) but decreased at a higher range of wp0, after reaching a maximum at wp0 = 0.60, and eventually was reduced to zero. At high values of wp0 (>0.75), polymerization occurred in the seed particles, whereas few or no new particles were formed despite the presence of micelles. The cessation of particle formation at high conversions was ascertained with a semibatch process in which the neat monomer feed was added to the reaction vessel containing the seed particles and emulsifier micelles. For wp0 > 0.85, the emulsifier micelles were disintegrated to stabilize the seed particles with no secondary particle formation. The possible reasons for the cessation of particle formation at high wp0 were examined. The size distribution of secondary particles showed a positive skewness in terms of volume because of the declining rate of growth for particles, together with a low rate of growth for small particles. The distribution breadth of new particles sharpened with increasing wp0. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1652–1663, 2002
Grafting of polymers onto a carbon‐fiber surface by ligand‐exchange reaction of poly(vinyl ferrocene‐co‐vinyl monomer) with polycondensed aromatic rings of the surface
Authors: Tsubokawa Norio , Abe Nobuyuki , Wei Gang , Chen Jinhua , Saitoh Satoshi , Fujiki Kazuhiro
Published: August 2002

To improve the surface of carbon fiber, the grafting reaction of copolymer containing vinyl ferrocene (VFE) onto a carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with vinyl monomers, such as methyl methacrylate (MMA) and styrene, using 2,2′‐azobisisobutyronitrile as an initiator. By heating the carbon fiber with poly(VFE‐co‐MMA) (number‐average molecular weight: 2.1 × 104) in the presence of aluminum chloride and aluminum powder, the copolymer was grafted onto the surface. The percentage of grafting reached 46.1%. On the contrary, in the absence of aluminum chloride, no grafting of the copolymer was observed. Therefore, it is considered that the copolymer was grafted onto the carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber. The molar number of grafted polymer chain on the carbon‐fiber surface decreased with increasing molecular weight of poly(VFE‐co‐MMA) because the steric hindrance of grafted copolymer on the carbon‐fiber surface increases with increasing molecular weight of poly(VFE‐co‐MMA). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1868–1875, 2002
Synthesis of a novel methacrylic monomer iniferter and its application in surface photografting on crosslinked polymer substrates
Authors: Luo Ning , Hutchison J. Brian , Anseth Kristi S. , Bowman Christopher N.
Published: August 2002

(Methacryloyl ethylenedioxycarbonyl) benzyl N,N‐diethyldithiocarbamate (HEMA‐E‐In) was synthesized and used as a monomer iniferter to develop a novel, photopatternable grafting technology. This molecule functions as both a methacrylic monomer and a photoiniferter (photoinitiator–transfer agent–terminator). The structure of HEMA‐E‐In was characterized by 1H NMR, Fourier transform infrared, and ultraviolet–visible spectroscopies. In the presence of the monomer iniferter, methyl methacrylate was polymerized by exposure to 365‐nm ultraviolet radiation, confirming the initiation capability of HEMA‐E‐In. After the copolymerization of HEMA‐E‐In into a methacrylate‐based polymer, attenuated total reflectance Fourier transform infrared spectra revealed that the photoiniferter functionality was present at the surface of this polymeric substrate. Photografting of poly(ethylene glycol) monomethacrylate monomer from the surface caused a significant change in the hydrophobicity of the surface as demonstrated by contact angle measurements. The novel monomer photoiniferter HEMA‐E‐In initiates the polymerization of bulk monomer and provides a reactive functionality that facilitates further initiation and polymer modification by the polymerization of different monomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1885–1891, 2002
Chemical structure of composites derived from poly(silicic acid) and 2‐hydroxyethylmethacrylate
Authors: Habsuda J. , Simon G. P. , Cheng Y.‐B. , Hewitt D. G. , Toh H. , Diggins D. R.
Published: August 2002

Organic–inorganic hybrids from 2‐hydroxyethylmethacrylate (HEMA) and poly(silicic acid)s were prepared and characterized. The molecular architecture of the inorganic phase was studied with 29Si NMR spectroscopy, and the effect of acid concentration and reaction time on the properties of poly(silicic acid) were elucidated. Interactions between phases were studied with NMR spectroscopy and gel permeation chromatography, and the coexistence and connectivity of the two phases were investigated. Contrary to previous assumptions, evidence was found that indicated that the organic and inorganic phases of this class of sol–gel materials were not covalently linked. The curing process was studied by infrared spectroscopy, by which the disappearance of terminal double bonds of HEMA monomer were monitored. Thermogravimetric analysis profiles showed that the inorganic phase content was about 10 wt %, and it was varied slightly by changes in the molar ratio of the components. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1342–1352, 2001
From metal‐catalyzed radical telomerization to metal‐catalyzed radical polymerization of vinyl chloride: Toward living radical polymerization of vinyl chloride
Authors: Asandei A. D. , Percec V.
Published: August 2002

The metal‐catalyzed radical polymerization of vinyl chloride (VC) in ortho‐dichlorobenzene initiated with various activated halides, such as α,α‐dihaloalkanes, α,α,α‐trihaloalkanes, perfloroalkyl halides, benzyl halides, pseudohalides, allyl halides, sulfonyl halides, α‐haloesters, α‐halonitriles, and imidyl halides, in the presence of Cu(0)/2,2′‐bipyridine, Fe(0)/o‐phenantroline, TiCp2Cl2, and other metal catalysts is reported. The formation of the monoadduct between the initiator and VC was achieved with all catalysts. However, propagation was observed only for metals in their zero oxidation state because they were able to reinitiate from geminal dihalo or allylic chloride structures. Poly(vinyl chloride) with molecular weights larger then the theoretical limit allowed by chain transfer to VC were obtained even at 130 °C. In addition, the most elemental features of a living radical polymerization, such as a linear dependence of the molecular weight and a decrease of polydispersity with conversion, were observed for the most promising systems based on iodine‐containing initiators and Cu(0), that is, ICH2PhCH2I/Cu(0)/bpy (where bpy = 2,2′‐bipyridyl), at 130 °C. However, because of the formation of inactive species via chain transfer to VC and other side reactions, the observed conversions were in most cases lower than 40%. A mechanistic interpretation of the chain transfer to monomer in the presence of Cu species is proposed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3392–3418, 2001
Polymorphic behavior in syndiotactic polystyrene/clay nanocomposites
Authors: Wu Tzong‐Ming , Hsu Sung‐Fu , Wu Jeng‐Yue
Published: August 2002

X‐ray diffraction methods were used in an investigation of the structural changes in syndiotactic polystyrene (sPS)/clay nanocomposites. sPS/clay was prepared by the intercalation of sPS polymer into layered montmorillonite. Both X‐ray diffraction data and transmission electron microscopy micrographs of sPS/clay nanocomposites indicated that most of the swellable silicate layers were exfoliated and randomly dispersed in the sPS matrix. The X‐ray diffraction data also showed the presence of polymorphism in the sPS/clay nanocomposites. This polymorphic behavior was strongly dependent on the thermal history of the sPS/clay nanocomposites from the melt and on the content of clay in the sPS/clay nanocomposites. Quenching from the melt induced crystallization into the α‐crystalline form, and the addition of montmorillonite probably increased heterophase nucleation of the α‐crystalline form. The effect of the melt crystallization of sPS and sPS/clay nanocomposites at different temperatures on the crystalline phases was also examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 736–746, 2002
Temperature dependence of the fluorescence quantum yields of diphenylsiloxane‐based copolymers in dilute solutions
Authors: Itoh Takao , Yang Mei‐Hui
Published: August 2002

The monomer and excimer fluorescence quantum yields of well‐defined poly(dimethylsiloxane‐co‐diphenylsiloxane)s with different diphenylsiloxane (Ph2SiO) contents have been determined, along with those of 1,1,3,3‐tetraphenyl‐1,3‐dimethyldisiloxane and 1,1,3,3,5,5‐hexaphenyltrisiloxane‐1,5‐diol used as model compounds, in a dilute organic solvent at different temperatures. The measured fluorescence quantum yields of the copolymers are correlated with the fraction of the (CH3)2SiO (Ph2SiO)n(CH3)2SiO structures. The monomer fluorescence yield for copolymers with low Ph2SiO contents is dominated mainly by the isolated (CH3)2SiO (Ph2SiO)(CH3)2SiO unit, and the apparent mean binding energy of the excimer does not increase significantly with increasing Ph2SiO content. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 854–861, 2002
Phase separation induced by shear quenching in polymer blends with a diblock copolymer
Authors: Jeon H. S. , Kim S. , Han C. C.
Published: August 2002

The effects of adding A–B diblock copolymer to a polymer blend (A/B) on phase‐separation kinetics and morphology have been investigated in a fixed shallow‐quench condition (ΔT = 1.5 °C) by in situ time‐resolved light scattering and phase‐contrast optical microscopy. A shear‐quench technique was used in this study instead of a conventional temperature‐quench method. Mixtures of nearly monodisperse low relative‐molecular masses of polybutadiene (Mw = 2.8 kg/mol), polystyrene (Mw = 2.6 kg/mol), and a near‐symmetric butadiene–styrene diblock copolymer (Mw = 6.3 kg/mol) as an interfacial modifier were studied. We observed that the addition of the diblock copolymer could either retard or accelerate the phase‐separation kinetics depending on the concentration of the diblock copolymer in the homopolymer blends. In contrast to the conventional temperature quench, we observed complex phase‐separation kinetics in the intermediate and late stages of phase separation by the shear‐quench technique. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 819–830, 2001
Configurations conducive to the formation of intramolecular excimers in poly(N‐vinyl carbazole) and its copolymers
Authors: Gallego Javier , Pérez‐Foullerat David , Mendicuti Francisco , Mattice Wayne L.
Published: August 2002

The ratios of the intensity of excimer and monomer emissions, denoted IE/IM, in poly(N‐vinyl carbazole) and copolymers of N‐vinyl carbazole and methyl methacrylate were measured with steady‐state fluorescence. Measurements were performed in dilute solutions of several fluid solvents at 25 °C and in a solid matrix of poly(methyl methacrylate) at room temperature. The values of IE/IM depended on the nature of the solvent, the emission wavelength, and the copolymer composition. Molecular dynamics simulations were performed for diastereoisomers of 2,4‐di(N‐carbazolyl)pentane and for isotactic and syndiotactic trichromophoric copolymer fragments to assist in the identification of the thermally accessible conformations capable of forming intramolecular excimers and the configurational relationship of the carbazole units in these complexes. Nearest neighbor carbazole groups made the dominant contribution to the excimers. Excimers were more likely in isotactic sequences than in syndiotactic sequences, as was also the case for the low‐energy excimer arising from the complete overlap of two carbazole units. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1272–1281, 2001
Thermal and infrared spectroscopic studies on hydrogen‐bonding interactions between poly‐(ε‐caprolactone) and some dihydric phenols
Authors: Li Jianchun , He Yong , Inoue Yoshio
Published: August 2002

The effects of three dihydric phenols on the thermal properties of poly‐(ε‐caprolactone) (PCL) were investigated by DSC. The thermal properties of PCL were found to be greatly modified by the addition of 4,4′‐dihydroxydiphenyl ether (DHDPE). When the content of DHDPE reached 40%, PCL that was a semicrystalline polymer in the pure state changed to a fully amorphous elastomer. Fourier transform infrared (FTIR) spectroscopy was also applied to investigate the specific interaction between PCL and DHDPE. The formations of intermolecular hydrogen bonds between the carbonyl groups of PCL and the hydroxyl groups of DHDPE were discovered. By applying the Beer–Lambert law and a curve‐fitting program, the fractions of hydrogen‐bonded carbonyl groups were quantitatively analyzed. Although one DHDPE molecule had the potentiality to form two hydrogen bonds with PCL chains, the values of the fraction of the hydroxyl group involved in the intermolecular hydrogen bond were so little that from a statistical point of view, the formation of two hydrogen bonds was very difficult for every DHDPE molecule. Both DSC and FTIR revealed that 4,4′‐dihydroxydiphenyl methane and 4,4′‐dihydroxyphenyl had the ability to form hydrogen bonds with PCL, which were strongly affected by the polarity of the group linking two hydroxyphenyls and the flexibility of the molecular chain. The stronger the polarity of the group and the better the flexibility of molecular chain, the more tendencies dihydric phenol had to form intermolecular hydrogen bonds with PCL. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2108–2117, 2001
Soil moisture conditions during thawing on a slope in the Daisetsu Mountains, Hokkaido, Japan
Authors: Matsumoto Hotaka , Kurashige Yoshimasa , Hirakawa Kazuomi
Published: August 2002

Precise monitoring of total potential, thawing front depth and groundwater level indicate the soil moisture conditions in a turf‐banked terrace during the thawing season in the Daisetsu Mountains, Japan. During thaw, the soil was in an almost unsaturated condition, and unsaturated soil water infiltrated downward. A small saturated zone sometimes appeared on the frost table with a duration of less than one day. In such cases the water in the saturated zone moved upward to a low total potential layer. The saturated zone was formed not by vertical water infiltration from the surface, but most likely by melting of ice lenses. Copyright © 2001 John Wiley & Sons, Ltd.

Des enregistrements précis du potentiel hydraulique total, du front de dégel du sol et du niveau de l'eau ont révélé quelles étaient les conditions d'humidité pendant la saison de dégel dans une terrasse à front végétalisé des montagnes de Daisetsu au Japon. Pendant le dégel, le sol a été presque insaturé et l'eau de ce sol insaturé s'est infiltré en profondeur. Une petite zone saturée apparaît parfois pendant moins d'un jour au dessus de la table gelée. Dans de teles situations, l'eau de la zone saturée se déplace vers le haut vers une couche de potentiel moins élevée. La zone saturée ne résulte pas d'une infiltration verticale de l'eau depuis la surface, mais plus probablement de la fusion de lentilles de glace. Copyright © 2001 John Wiley & Sons, Ltd.
New geophysical methods of investigating the nature and distribution of mountain permafrost with special reference to radiometry techniques
Authors: Mühll Daniel Vonder , Hauck Christian , Gubler Hansueli , McDonald Robert , Russill Nick
Published: August 2002

A series of geophysical surveys were undertaken within the PACE geophysical work package. Various methods were applied including refraction seismics, DC resistivity, ground penetrating radar (GPR), electromagnetic induction, radiometry and bottom temperature of snow cover (BTS). The focus of the surveys was to determine the internal structures and distribution of mountain permafrost. This paper gives a preliminary overview of progress. The two‐dimensional DC resistivity tomography combines the geoelectrical sounding and mapping and makes it possible to model internal structures. This method was applied at all PACE drill sites. Electromagnetic induction methods showed good results, in particular the EM‐31 for determining the permafrost distribution and the PROTEM to assess the overall permafrost thickness. A major new development discussed here is the use of passive microwave (11.4 GHz) for airborne remote measurement of the bottom temperature of snow cover (BTS). Manual BTS measurements agreed very well with the BTS determined by radiometry. To reduce ambiguity, several geophysical methods should be deployed at the same locality. As a further step, such measurements could be interpreted using joint inversions. Copyright © 2001 John Wiley & Sons, Ltd.

Une série de levés géophysiques a été réalisé dans le cadre des travaux de PACE. Différentes méthodes ont été utilisées y compris la séismique réfraction, la résistivité DC, le radar pénétrant le sol (GPR), l'induction électro‐magnétique, la radiométrie et la température à la base de la couverture nelgeuse (BTS). Le but de ces levés était de déterminer les structures internes et la distribution du pergélisol de montagne. Le présent article donne une vue générale préliminaire des progrès réalisés. La tomographie en deux dimensionns par résistivité. DC qui combine le sondage géoélectrique et la cartographie, rend possible la reconnaissance des structures internes. Cette méthode a été appliquée dans tous les sites de sondage. Les méthodes par induction électromagnétique ont donné de bons résultats, en particulier la méthode par EM‐31 pour déterminer la distribution du pergéllisol, tandis que la méthode PROTEM a été utile pour estimer l'épaisseur totale du pergélisol. Un imporant nouveau développement discuté ici est l'emploi de micro‐ondes passives (11.4 GHz) dans des mesures aéroportées de la température de la base de la converture de neige (BTS). Des mesures manuelles BTS se sont révélées bien en accord avec les données BTS obtenues par radiométrie.

Pour diminuer les ambiguités, plusieurs methodes géophysiques devraient toujours être utilisées. Copyright © 2001 John Wiley & Sons, Ltd.
Results of permafrost modelling of the lowlands and shelf of the Laptev Sea Region, Russia
Authors: Romanovskii Nikolai N. , Hubberten Hans‐W.
Published: August 2002

Permafrost thickness evolution models for the Laptev Sea shelf and coastal lowlands describe a palaeogeographic scenario, a geological model, and the choice of lower and initial boundary conditions. The model covers four climatic and glacio‐eustatic cycles. The temperature zonation of permafrost, the freezing of seawater‐saturated deposits, and the accumulation of ice‐rich syncryogenic sediments with fresh ice on the emergent shelf surface are all included into the model. Different values of geothermal heat flow are used. Results indicate an increase in the magnitude of oscillations of the permafrost bottom, an increase in differences in permafrost thickness during the warmer parts of climatic cycles, a lag in the appearance of the maximum permafrost thickness after the climate extreme, and a degradation of permafrost on the shelf and coastal lowlands at the present time. Copyright © 2001 John Wiley & Sons, Ltd.

Des modèles d'évolution de l'épaisseur du pergélisol sur la plate‐forme de la mer de Laptev et sur les basses terres côtières décrivent un scénario paléogéographique, un modèle géologique et imposent le choix de conditions de départ. Les modèles couvrent quatre cycles climatiques et glacio‐eustatiques. La zonation des temératures du pergélisol, le gel des dépôts saturés en eau de mer et l'accumulation de sédiments riches en glace sur la plate‐forme émergente sont des données incluses dans ce modèle. Différentes valeurs sont employées pour le flux géothermique. Les résultats indiquent une augmentation de l'ampleur des oscillations de la base du pergélisol, une augmentation des différences d'épaisseur du pergélisol pendant les parties chaudes des cycles climatiques, un retard dans l'apparition de l'épaisseur maximum du pergélisol après le minimum climatique et une dégradation actuelle du pergélisol sur la plate‐forme et les basses terres côtières. Copyright © 2001 John Wiley & Sons, Ltd.
Temperature regime of a small sandstone tor, latitude 80 °N, Ellesmere Island, Nunavut, Canada
Authors: Lewkowicz Antoni G.
Published: August 2002

Near‐surface rock temperatures were recorded hourly for more than one year around a sandstone tor located on a ridge‐crest at an elevation of 270 m asl. There were significant differences between air and rock temperatures except during the polar night. The SSE‐ and WSW‐facing sides experienced large amplitude diurnal temperature cycles in the late‐winter and spring, and these crossed through 0 °C from mid‐April to May, well before air temperatures rose above freezing. Rock temperatures at a depth of 15 mm on the SSE‐face exceeded air temperature by up to 31 °C. During most of the summer, rock faces and air temperatures remained above 0 °C. Diurnal temperature cycles were smaller in amplitude in the autumn and few cycles through 0 °C were measured because of persistent cloud cover and the absence of a radiation‐reflecting snowpack. Modelling using a constant environmental lapse rate shows that although the timing and number of temperature cycles through 0 °C are influenced by altitude, the importance of rock‐face orientation on the relative numbers of cycles is independent of tor elevation. The average rate of micro‐weathering measured on several tors over four years was 0.012 mm a−1. No loss of larger clasts was observed at the monitored tor over 11 years suggesting that the combined rate of all types of weathering is low. Copyright © 2001 John Wiley & Sons, Ltd.
Levalbuterol hydrochloride*
Authors: Slattery D. , Wong S.W. , Colin A.A.
Published: August 2002

Racemic albuterol, a commonly used bronchodilator, is an exact 50:50 mixture of two enantiomers, R‐ and S‐albuterol. Concern regarding increased mortality associated with the use of this beta‐2 (β2) agonist triggered the study of both of these enantiomers separately.

In vitro studies suggest that the two enantiomers have different binding affinities for β‐adrenoreceptors, may exert opposing effects on inflammation, demonstrate different effects on mucocilary transport, and display differing pharmacokinetics. Clinical studies comparing both enantiomers are few, of short duration, and often in small patient populations, and their results vary. R‐albuterol has greater bronchodilatory effects than the racemate and may have anti‐inflammatory properties. S‐albuterol has markedly less affinity for the β‐adrenoreceptor. It was found to cause bronchoconstriction in animal models, but neither bronchoconstrictive nor pro‐inflammatory effects have been conclusively demonstrated in human studies.

The data available at present, while suggestive, are insufficient to conclusively recommend R‐albuterol over the racemate. Further basic research and investigations in humans comparing both enantiomers at increasing doses over longer time periods are required to clarify the precise roles of R‐ and S‐albuterol. Pediatr Pulmonol. 2002; 33:151–157. © 2002 Wiley‐Liss, Inc.
Effect of airway inflation pressure on forced expiratory maneuvers from raised lung volume in infants*
Authors: Lum Sooky , Hoo Ah‐Fong , Stocks Janet
Published: August 2002

The raised lung volume technique is increasingly used to measure forced expiratory maneuvers in infants. However, there is no consensus regarding the optimal airway inflation pressure (Pinf) required for such maneuvers, or the influence of small changes in Pinf within and between infants. The aim of this study was to assess the effect of small differences (0.2–0.3 kPa) in Pinf on forced vital capacity (FVC), forced expired volume in 0.5 sec (FEV0.5), and forced expired flow at 75% of vital capacity (FEF75), all derived from the raised volume rapid thoraco‐abdominal compression (RVRTC) technique. Randomized paired forced expiratory maneuvers were obtained in 32 healthy infants ( 3.9–39.3 weeks old, 3.8–9.9 kg) with the safety pressure relief valve for Pinf set to 2.7 kPa or 3.0 kPa (27 or 30 cm H20).

When mean (SD) Pinf was increased by 8.4 (2.8)%, there was a significant (P < 0.01) increase in mean (SD) FVC, FEV0.5, and FEF75 by 5.8 (5.7)%, 6.1 (6)%, and 8.3 (16.2)%, respectively.

In conclusion, relatively small differences in Pinf will result in significant differences in FVC, FEV0.5, and FEF75 by RVRTC technique. Precision in setting and reporting the applied Pinf is therefore essential, particularly if data are to be compared between centers. Pediatr Pulmonol. 2002; 33:130–134. © 2002 Wiley‐Liss, Inc.
Analysis of antibodies of known structure suggests a lack of correspondence between the residues in contact with the antigen and those modified by somatic hypermutation
Authors: Ramirez‐Benitez Maria del Carmen , Almagro Juan Carlos
Published: August 2002

Forty unique murine antibody–antigen complexes determined at 2.5 Å or less resolution are analyzed to determine whether the residues in direct contact with the antigen are modified by somatic hypermutation. This was done by taking advantage of the recent characterization of the pool of Vκ germline genes of the mouse. The average number of residues in contact with the antigen in the VL gene, which contains the CDRL‐1, CDRL‐2, and all but one residue of CDRL‐3, was six. The average number of somatic mutations was similar (around five). However, as many as 53% of the antibodies did not show somatic replacements of residues in contact with the antigen. Another 28% had only one. Overall, the frequency of antibodies with increasing number of somatic replacements in residues in contact with the antigen decreased exponentially. A possible explanation of this finding is that mutations in the contacting residues have an adverse effect on the antigen–antibody interaction. This implies that most of the observed mutations are those remaining after negative (purifying) selection. Therefore, efficient strategies of site‐directed mutagenesis to improve the affinity of antibodies should be focused on residues other than those directly interacting with the antigen. Proteins 2001;45:199–206. © 2001 Wiley‐Liss, Inc.
Fungicidal activity of β‐thujaplicin analogues
Authors: Baya Mounir , Soulounganga Patrice , Gelhaye Eric , Gérardin Philippe
Published: August 2002

The fungicidal activity of analogues of β‐thujaplicin, a natural product responsible for the durability of heartwood of several cupressaceous trees, was investigated in vitro on the growth of different white and brown rot fungi involved in wood biodegradation, Coriolus versicolor, Phanerochaete chrysosporium, Poria placenta and Gloephyllum trabeum. The study shows that 2‐hydroxycyclohepta‐2,4,6‐trienone (tropolone), easily prepared according to a literature procedure, possesses interesting fungicidal activity when compared to β‐thujaplicin, azaconazole, tebuconazole and copper oxine, which suggests this compound should be examined further as a potential biocide for wood preservation.

© 2001 Society of Chemical Industry
Studies on the hypoglycaemic activity of Punica granatum seed in streptozotocin induced diabetic rats
Authors: Das Asish K. , Mandal Subhash C. , Banerjee Sanjay K. , Sinha Sanghamitra , Saha B. P. , Pal M.
Published: August 2002

The hypoglycaemic activity of Punica granatum Linn. (Family Punicaceae) seed extract on rats made diabetic by streptozotocin (STZ) was investigated. The methanol extract of the seed at doses of 300 and 600 mg/kg, and chlorpropamide 200 mg/kg was administered to STZ diabetic rats. The seed extract (150, 300 and 600 mg/kg, orally) caused a significant reduction of blood glucose levels in STZ induced diabetic rats by 47% and 52%, respectively, at the end of 12 h. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of curcumin on ethanol‐induced stress on mononuclear cells
Authors: Rajakrishnan V. , Shiney S. J. , Sudhakaran P. R. , Menon V. P.
Published: August 2002

Blood cells in circulation are exposed to a wide variety of stress‐causing agents, causing a number of changes including interactions with other cells and the extracellular matrix of the endothelial wall. In order to understand the role of curcumin, an antioxidant principle from Curcuma longa Linn., on blood mononuclear cells from rabbits given ethanol for 30 days and ethanol with curcumin, cells were isolated and an attachment assay was carried out. The monocytes from ethanol‐treated rabbits showed a lesser attachment to collagen, the major component of the vessel wall subendothelium, and those from curcumin treated animals along with ethanol showed a higher affinity to collagen, causing an alteration in the attachment of monocyte to collagen due to ethanol‐induced stress. Copyright © 2002 John Wiley & Sons, Ltd.
Antiprotozoal activity of Neurolaena lobata
Authors: Berger Ingeborg , Passreiter Claus Martin , Cáceres Armando , Kubelka Wolfgang
Published: August 2002

Extracts, fractions and sesquiterpene lactones from Neurolaena lobata (L.) R. Br. (Asteraceae), a traditional medicinal plant from Guatemala, were tested in vitro against Leishmania spp. promastigotes, Trypanosoma cruzi trypomastigotes and epimastigotes and Trichomonas vaginalis trophozoites. The ethanol extract inhibited the parasite growth of L. mexicana, T. cruzi and T. vaginalis significantly. The pure germacranolides 1 and a mixture of 2 and 3, isolated from the ethonal extract, were highly active against L. mexicana and T. cruzi. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of Mimosa pudica root powder on oestrous cycle and ovulation in cycling female albino rat, Rattus norvegicus
Authors: Valsala S. , Karpagaganapathy P. R.
Published: August 2002

Mimosa pudica root powder (150 mg/kg body weight) when administered intragastrically, altered the oestrous cycle pattern in female Rattus norvegicus. Nucleated and cornified cells were absent in all rats. The smear was characterized by leucocytes only, as in dioestrus, which persisted for 2 weeks. There was a significant reduction in the number of normal ova in rats treated with the root powder compared with the control rats, and a significant increase in the number of degenerated ova. Copyright © 2002 John Wiley & Sons, Ltd.
Liquid crystalline polymer pouches for local ­anaesthetic emulsion
Authors: Flodberg G. , Axelson‐Larsson L. , Hedenqvist M. S. , Gedde U. W.
Published: August 2002

In order to enhance the long‐term properties of a high‐pH local anaesthetic drug, emulsion tests were conducted where the emulsion was stored in pouches made of a compression moulded high‐barrier liquid‐crystalline polymer, Vectra A950. The oxygen permeability of the pouch material was too low to be detected at 23°C and 0% relative humidity with the instrument used. The water vapour transmission rate was 0.135 (g.mm/m2.day) at 38°C and 100% relative humidity. The emulsion, containing prilocain and lidocain as active substances, was stored in pouches which were sealed by the thermal impulse technique at 260°C for 1.08 s. It was possible to obtain good quality films and good quality seals by optimization of the compression moulding and sealing operations. The concentrations of prilocain and lidocain in the emulsion were studied for 14 weeks at two different temperatures, 40°C and 60°C, and at 100% relative humidity. The decrease in concentration was higher for prilocain (5.4–8.3%) than for lidocain (3.4–3.6%). The loss of the substances from the emulsion was due mainly to adsorption onto the polar surface of the liquid crystalline polymer. Copyright © 2001 John Wiley & Sons, Ltd.
Properties of atoms in crystals: Dielectric polarization
Authors: Bader Richard F. W. , Matta Chérif F.
Published: August 2002

It is shown that the polarization of a molecule or an extended system, permanent or induced can, like all measurable properties, be equated to a sum of atomic contributions. While it has been previously shown that a change in the polarization of a dielectric can be considered a consequence of a geometric quantum phase and obtainable from a Berry phase in a parameter space, such a possibility does not exclude a real space description, stated in terms of the charge distributions of the system's composite atoms or cells. The cells are defined as bounded regions of real space whose properties are described by the physics of a proper open system, a description that applies to any system regardless of the nature of the interactions between the atoms. This approach necessarily leads to the inclusion of a contribution to the polarization arising from the transfer of charge across the boundary of a cell, in addition to that from the cell's internal polarization, thereby correcting the textbook description of polarization that considers only the latter contribution. It is shown that a neutral repeating cell in a dielectric behaves as an atomic capacitor which mimics the macroscopic behavior, with the internal charge transfer leading to the creation of what Feynman terms the “surface polarization charge.” © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Factors determining the performance of triple quadrupole, quadrupole ion trap and sector field mass spectrometers in electrospray ionization tandem mass spectrometry of oligonucleotides. 1. Comparison of performance characteristics
Authors: Premstaller Andreas , Ongania Karl‐Hans , Huber Christian G.
Published: August 2002

The performance of triple‐stage quadrupole (TSQ), quadrupole ion trap (QIT), and double focusing sector field (DFSF) mass spectrometers for the generation of fragment ions to obtain sequence information about oligonucleotides was compared. Upon electrospray ionization (ESI), the charge‐state distribution of candidate precursor ions not only varied significantly with the type of mass spectrometer, but also with the size and sequence of the investigated oligonucleotides. While concentration limits of detection for an octanucleotide were in the 100 pmol/L range on the QIT and in the 5–10 nmol/L range on the TSQ and DFSF instruments, those of a 24‐mer were in the 2–13 nmol/L range on all three instruments. Reproducibility of mass determination, an important prerequisite for reliable identification of fragment ions, was highest on the TSQ with 0.0037% relative standard deviation over three days. Finally, the tandem mass spectra of a dimethoxytritylated pentanucleotide recorded on the three instruments were compared. Relatively simple spectra dominated by complete series of fragment ions of the (a‐B) and w type were obtained on the QIT. Complete series of (a‐B) and w ions were also observed on the TSQ. However, additional fragments belonging to the b, c, d, x and z series were found in the spectrum. In the spectrum recorded after in‐source fragmentation in the DFSF, only fragments corresponding to the loss of a nucleobase and a complete series of w ions were observed. All three mass spectrometers were suitable for the generation of fragment ions, from which the complete nucleotide sequence of the pentanucleotide could be deduced. Copyright © 2001 John Wiley & Sons, Ltd.
Factors determining the performance of triple quadrupole, quadrupole ion trap and sector field mass spectrometer in electrospray ionization mass spectrometry. 2. Suitability for de novo sequencing
Authors: Premstaller Andreas , Huber Christian G.
Published: August 2002

The sequence coverage by fragment ions resulting from collision‐induced dissociation in a triple stage quadrupole (TSQ) and a quadrupole ion trap (QIT) mass spectrometer of 10–20‐mer oligonucleotides was investigated. While (a‐B) and w ion series were the most abundant on both instruments, additional ion series of sequence relevance were preferably formed in the TSQ. Thus, a total number of 83 fragment ions were used to deduce the complete sequence of a 10‐mer oligonucleotide of mixed sequence from a tandem mass spectrum recorded on the TSQ. The complete sequence was also encoded in the 28 fragments that were obtained from the QIT under comparable fragmentation conditions. Spectrum complexity increased considerably at the cost of signal‐to‐noise ratio upon fragmentation of a 20‐mer oligonucleotide in the TSQ, whereas spectrum interpretation with longer oligonucleotides was significantly more straightforward in spectra recorded on the QIT. The extent of fragmentation had to be optimized by appropriate setting of collision energy and choice of precursor ion charge state in order to obtain full sequence coverage by fragments for de novo sequencing. Moreover, full sequence information was also dependent on base sequence because of the low tendency of backbone cleavage at thymidines. Tandem mass spectrometry on the QIT yielded redundant information that was successfully utilized to deduce the complete sequence of 20‐mer oligonucleotides with high confidence. Copyright © 2001 John Wiley & Sons, Ltd.
Application of DNA‐binding polymers for preparation of DNA for analysis by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Smirnov Igor P. , Hall Laura R. , Ross Philip L. , Haff Lawrence A.
Published: August 2002

The susceptibility of matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) to the presence of salts in a sample, especially salts of alkali metals, requires careful and often tedious desalting procedures which complicate and slow the throughput of MS‐based methods. A novel approach to sample preparation was developed based on the extraction of DNA out of solution onto a solid surface with an attached DNA‐binding polymer, such as polyethyleneimine or polyvinylpyrrolidone. The observed binding is strong enough to sustain washing, and, as a result, desalting and concentration can be performed in a single fast step. After DNA has been immobilized on the surface and supernatant solution removed, subsequent addition of MALDI matrix releases material from the surface, which co‐crystallizes with matrix. The mass spectrometric analysis is then performed directly from this support. Analysis of oligonucleotides and three‐fold multiplexed SNP typing reactions performed by this method shows improved sensitivity and excellent resolution for various DNA fragments, together with high tolerance to various buffer components, such as alkali metals and surfactants. Simplicity and speed make it attractive for high‐throughput sample preparation and analysis of oligonucleotide mixtures by MALDI‐MS. Copyright © 2001 John Wiley & Sons, Ltd.
Maturation of the lantibiotic subtilin: matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry to monitor precursors and their proteolytic processing in crude bacterial cultures
Authors: Stein Torsten , Entian Karl‐Dieter
Published: August 2002

Bacillus subtilis synthesizes the lanthionine containing 32‐amino‐acid peptide antibiotic (lanti‐biotic) subtilin from a ribosomally generated 56‐amino‐acid precursor pre‐propeptide by extensive posttranslational modifications. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) was used to monitor the production of matured subtilin within crude samples taken from B. subtilis culture media without prior fractionation. The processing reaction of subtilin was blocked with the serine protease inhibitor phenylmethylsulfonyl fluoride and different subtilin precursor peptides in the molecular mass range up to 6220 were observed. Two of these species were isolated by reversed‐phase high‐performance liquid chromatography (HPLC) and structurally analyzed by post‐source decay MALDI‐TOFMS. We provide evidence that the precursor species comprise the posttranslational modified C‐terminal part of subtilin to which leader peptide moieties with different chain lengths are attached. These antimicrobial‐inactive species could be processed to antibiotic‐active subtilin by incubation with culture media of different subtilin‐nonproducing B. subtilis strains as indicated by a combination of antimicrobial growth assays and MALDI‐TOFMS analyses. These achievements are strong evidence for the sensitivity of MALDI‐TOFMS methodology that allows straightforward investigations of analytes even in complex mixtures without time‐consuming sample preparations. Copyright © 2001 John Wiley & Sons, Ltd.
Double resonance ejection in a micro ion trap mass spectrometer
Authors: Moxom Jeremy , Reilly Peter T. A. , Whitten William B. , Ramsey J. Michael
Published: August 2002

Ion ejection from a cylindrical micro ion trap by resonance excitation of the secular motion is observed to be strongly dependent on the frequency of the secular motion at resonance. Both the intensity of the ion signal and the mass resolution of the resulting mass spectrum are increased when the ion secular frequency is approximately that of a nonlinear resonance of the trap. The resonances are attributed to electrical as well as geometrical considerations. Copyright © 2002 John Wiley & Sons, Ltd.
On‐line measurement of intramolecular carbon isotope distribution of acetic acid by continuous‐flow isotope ratio mass spectrometry
Authors: Yamada Keita , Tanaka Misato , Nakagawa Fumiko , Yoshida Naohiro
Published: August 2002

Molecular and intramolecular carbon isotope measurements of acetic acid present in natural environments have been performed by off‐line procedures. The off‐line method is complicated and time‐consuming and requires micromolar to millimolar amounts of sample. This limits geochemical isotopic studies, especially at the intramolecular level, on acetic acid present in natural samples. Here, we examine an on‐line measurement of intramolecular carbon isotope distribution of acetic acid using continuous‐flow isotope ratio mass spectrometry (CF‐IRMS) coupled with an on‐line pyrolysis system. This is achieved by measurement of the respective carbon isotope ratios of CH4 and CO2 produced by on‐line pyrolysis of acetic acid. Results for authentic standards of pure acetic acid demonstrated the practicality of this on‐line method, although the carbon isotope ratio of the methyl group could not be determined directly. The precision of the carbon isotope measurements was 0.4‰ (1σ). The carbon isotope distribution determined by the on‐line method was identical to that determined by the conventional off‐line method within analytical error. The advantages of the on‐line method compared with the conventional off‐line method are that it is less laborious, requires less analytical time (less than one hour per sample) and, most importantly, uses smaller sample sizes (ca. 10 nanomole). An application of this on‐line method to natural geochemical samples will provide an insight into the geochemical cycle of acetic acid. Copyright © 2002 John Wiley & Sons, Ltd.