bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inter‐decadal variability in daily rainfall at Durham (UK) since the 1850s
Authors: Burt T. P. , Horton B. P. 
Published: December 2006

AbstractRecords of daily rainfall at Durham (UK) are analysed from 1850 to the present. The most notable wet period is the 1870s, followed by a protracted period of below‐average rainfall. Other than the 1870s, summers tended to be much wetter than winters during the latter part of the 19th century. In the 20th century, summers had become drier and winters wetter. To analyse large daily totals, three thresholds, 15, 22.6, and 25 mm, are used. For all three indices, the frequency of large falls was highest from the 1860s to the 1880s, followed by a low frequency in the 1900s. Since then, the general trend has been for totals to gradually increase. There is a clear division for the annual total rainfall, number of heavy falls (≥15 mm), and proportion of total rainfall provided by heavy falls in the winter (154 mm, 147 days, 12%, respectively) and spring (140 mm, 180 days, 16%) seasons in comparison to the summer (181 mm, 329 days, 28%) and autumn (186 mm, 304 days, 23%) seasons. However, since 1990, winter total rainfall (164 mm) has overtaken the summer total (154 mm). Furthermore, since 1990, heavy falls of rain in spring (23 days) and the proportion of total rainfall (26%) have overtaken summer heavy rain (17 days) and the proportions of rainfall in both summer (24%) and autumn (24%). In terms of heavy rainfall, winters have seen only a small increase in its relative importance, whereas its relative importance declined from the 1960s to the mid‐1990s for summers. The widely recognised increase in the winter:summer ratio of rainfall since the 1960s is clearly evident. Overall, there has been a narrowing of the differences between seasons in terms of the frequency of heavy falls of rain in the 1990s. Copyright © 2006 Royal Meteorological Society
Binary logistic regression models for short term prediction of premonsoon convective developments over Kolkata (India)
Authors: Dasgupta S. , De U. K. 
Published: December 2006

AbstractScientists have identified certain dynamic and thermodynamic parameters, which are significant for the occurrence of convective developments in the premonsoon period (March–May) in Kolkata (India). In this paper Binary Logistic Regression Models have been considered for prediction of these convective developments from a prior knowledge of the values of the significant parameters. Analyses have been carried out for lead times of 12 h. Initially the evening radiosonde information (1200 UTC) has been considered as these convective developments occur in Kolkata mostly toward the evening. The performance of the model for similar developments in the morning has also been taken up at a later point. As some of the identified parameters are correlated, the dimension of the problem has been reduced and uncorrelated explanatory variables generated for the Logistic Regression Model. Two conventional variable selection methods, for example, forward and backward selections have been used for this purpose. A comparative study of the two variable selection procedures in the light of the predictive power of the resulting models has been presented. The probable causes underlying the poor performance of the models in case of correct prediction of morning convection over the city has been explored and possible remedies suggested at the end. Copyright © 2006 Royal Meteorological Society
A new quantitative Raman measurement scheme using Teflon as a novel intensity correction standard as well as the sample container
Authors: Nah Sanghee , Kim Donghyuk , Chung Hoeil , Han Sung‐Hwan , Yoon Moon‐Young 
Published: December 2006

AbstractA novel and reliable quantitative Raman measurement scheme has been proposed for the analyses of ethanol and isopropanol solutions. Teflon tubing was employed as an effective intensity correction standard as well as the sample cell. This allowed for the synchronous collection of the mixed Raman spectrum from the Teflon standard and the sample without any extra optical configuration. A non‐overlapping Teflon band was used as the standard peak to correct the Raman intensity changes resulting from laser power variations. In addition to the use of Teflon tubing,a wide area illumination (WAI) scheme was employed, which made the laser illumination into a circle of 6 mm diameter (area: 28.7 mm2), to cover a wide sample area. The WAI scheme improved the reliability of the Raman measurement by significantly increasing the reproducibility of the sampling owing to a decreased sensitivity to sample placement with respect to the focal plane as well as a wider sample coverage area. The resulting Raman spectra were more reproducible and more representative of the correct sample composition. Overall, a superior prediction performance was achieved using the WAI scheme compared to the conventional Raman collection method. The proposed system has great potential for use in the quantitative analysis of diverse liquid samples with good reproducibility. Copyright © 2006 John Wiley & Sons, Ltd.
Competition between Host Aggregates and Isolated Guest Chromophores in Trapping Excitons in Polybenzazole Copolymers and Blends
Authors: Wang Shanfeng , Chen Yan , Zhuang Qixin , Li Xinxin , Wu Pingping , Han Zhewen 
Published: December 2006

AbstractSummary: Host–guest systems have been prepared using the blends and copolymers consisting of the host molecule poly(p‐phenylene benzobisoxazole) (PBO) with a higher bandgap of 2.93 eV and the guest molecule poly(2,5‐thienylbenzobisoxazole) (PBOT) with a lower bandgap of 2.57 eV. These systems have been investigated using photoluminescence (PL) spectra and time‐resolved PL decay dynamics. Both PBOT‐PBO copolymers and PBOT/PBO blends with the PBOT compositions less than 20% demonstrate higher intensities and narrower bandwidths in solid‐state emission compared to that of PBOT, as well as larger fractions of the shorter lifetime component in PL decay dynamics. A general scheme on intrachain and interchain exciton migration and trapping mechanism has been proposed to interpret the phenomena in both solutions and thin films. Particularly, a competition in trapping exciton between PBO aggregates and isolated PBOT chromophores has been revealed.General scheme of exciton migration and trapping paths for host (D: donor)–guest (A: acceptor) systems involving the isolated chromophores (A and D) and aggregates (AA and DD) in both ground state and excited state marked without or with an asterisk.magnified imageGeneral scheme of exciton migration and trapping paths for host (D: donor)–guest (A: acceptor) systems involving the isolated chromophores (A and D) and aggregates (AA and DD) in both ground state and excited state marked without or with an asterisk.
Preparation of Magnetite Nanoparticles Coated with an Amphiphilic Block Copolymer: A Potential Drug Carrier with a Core‐Shell‐Corona Structure for Hydrophobic Drug Delivery
Authors: Bai Yunpeng , Teng Bao , Chen Shizhen , Chang Yu , Li Zhaolong 
Published: December 2006

AbstractSummary: The synthesis of magnetic magnetite nanoparticles coated with amphiphilic block copolymers of poly(ethyl methacrylate)‐block‐poly(2‐hydroxyethyl methacrylate) for use as new potential carriers for hydrophobic drug delivery is reported. The results show that a new core‐shell‐corona structural material is obtained with a very narrow molecular weight distribution of the hydrophobic segment (PDI = 1.10). UV‐Vis results show that 37% of progesterone is released from the nanoparticles after 22 h, much slower than free release (99% after 14 h), which demonstrates that the presence of the hydrophobic segment can effectively control the release of hydrophobic drugs.Synthesis of an amphiphilic block polymer poly(ethyl methacrylate)‐block‐poly(2‐hydroxyethyl methacrylate) on magnetite nanoparticles and their use as potential drug carriersmagnified imageSynthesis of an amphiphilic block polymer poly(ethyl methacrylate)‐block‐poly(2‐hydroxyethyl methacrylate) on magnetite nanoparticles and their use as potential drug carriers
Redesigning network topology with technology considerations
Authors: Habib Sami J. 
Published: December 2006

AbstractWe present a redesign methodology that automatically redesigns a network topology while considering the different network technology interfaces. The network redesign problem is to preserve as many as possible of the network devices within the original network topology to satisfy the redesign factors while minimizing the redesign cost and time. The redesign factors can be various parameters that are involved in the design of a network topology, such as the workload and number of clients. In this paper we used a uniform growth of the network workload as the main factor for topology redesign; moreover, our methodology attempts to maintain as many as possible of the network devices within the original topology while satisfying the extra growth of the clients' loads. We formulated the network redesign problem as an optimization problem and used an evolutionary approach to search the redesign space. The experimental results for a three‐level network redesign problem described here demonstrate how valuable the redesign methodology is in finding good solutions with low redesign cost and short redesign time for an enterprise networks consisting of 65 client nodes. Copyright © 2006 John Wiley & Sons, Ltd.
Comparison of p16INK4a expression with p53 alterations in head and neck cancer by tissue microarray analysis
Authors: Karsai S , Abel U , Roesch‐Ely M , Affolter A , Hofele C , Joos S , Plinkert PK , Bosch FX 
Published: December 2006

AbstractWe investigated whether there is a relationship between loss of p16INK4a protein expression and p53 alterations in head and neck squamous cell carcinomas (HNSCCs). For this purpose, immunohistochemistry was performed on tissue microarrays of 664 tumours; this represents the largest HNSCC cohort studied for molecular biomarkers. Loss of p16INK4a protein expression was associated with aberrant p53 expression (negative or overexpressed) in the total cohort, and with TP53 mutations in 200 tumours analysed (p < 0.0001 each). Both loss of p16INK4a expression and p53 alterations differed significantly across both tumour sites and stages, being more prevalent in the hypopharynx than in the other tumour sites and in advanced tumour stages. As a possible link between p53 status and p16INK4a loss, we found that increased DNA methyltransferase 1 protein levels occurred preferentially in tumours with aberrant p53 (p = 0.001) and negative p16INK4a expression (p = 0.0004). In the total cohort, there was a borderline significant difference in patient survival across three p16INK4a expression levels (negative, positive, high), with loss of p16INK4a expression showing shortest survival. It is suggested that loss of p16INK4a expression and p53 alterations should be viewed as related events involved in the early carcinogenic process. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Controlled helical orientation of carbazole in amino acid derived poly(N‐propargylamide)s
Authors: Zhao Haichao , Sanda Fumio , Masuda Toshio 
Published: December 2006

AbstractNovel L‐alanine and L‐glutamic acid derivatized, carbazole‐containing N‐propargylamides [N‐(9‐carbazolyl)ethyloxycarbonyl‐L‐alanine N′‐propargylamide and N‐(9‐carbazolyl)ethyloxycarbonyl‐L‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] were synthesized and polymerized with (nbd)Rh+[η6‐C6H5B−(C6H5)3] (nbd = norbornadiene) as a catalyst to obtain the corresponding polymers with moderate molecular weights in high yields. Polarimetry, circular dichroism, and ultraviolet–visible spectroscopy studies revealed that both poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] took a helical structure with a predominantly one‐handed screw sense in tetrahydrofuran, CHCl3, and CH2Cl2. The helix content of poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L‐alanine N′‐propargylamide] could be tuned by heat or the addition of a protic solvent, and the helical sense of poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] was inverted by heat in CHCl3 or in mixtures of tetrahydrofuran and CH2Cl2. Poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] also took a helical structure in film states. They showed small fluorescence in comparison with the monomers and redox activity based on carbazole. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 253–261, 2007
Aging of a donor conjugated polymer: Photochemical studies of the degradation of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene]
Authors: Chambon Sylvain , Rivaton Agnès , Gardette Jean‐Luc , Firon Muriel , Lutsen Laurence 
Published: December 2006

AbstractThis article is devoted to the study of the photoaging and thermal aging of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene] (MDMO–PPV; also called OC1C10–PPV) used in organic solar cells. Thin MDMO–PPV films (thickness < 1 μm) were exposed to ultraviolet‐light irradiation (λ > 300 nm) in the presence of air or thermooxidized at 60 °C. The modifications of the chemical structure of the matrix were analyzed with ultraviolet–visible and infrared spectroscopy. The oxidation products that formed were identified by postirradiation treatments, including chemical derivatization reactions. On the basis of the identification of the various products formed, a two‐step radical mechanism is proposed to account for the modification of the chemical structure of the polymeric matrix. It involves first the oxidation of the ether substituent followed by the oxidation of the double bonds. These reactions are responsible for a loss of conjugation of MDMO–PPV, chain scissions, and a decrease in the visible absorbance, which are anticipated to drastically impair the photovoltaic properties of the material. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 317–331, 2007
Multiblock copolymers of poly(2,5‐benzophenone) and disulfonated poly(arylene ether sulfone) for proton‐exchange membranes. I. Synthesis and characterization
Authors: Wang Hang , Badami Anand S. , Roy Abhishek , McGrath James E. 
Published: December 2006

AbstractNanophase‐separated, hydrophilic–hydrophobic multiblock copolymers are promising proton‐exchange‐membrane materials because of their ability to form various morphological structures that enhance transport. A series of poly(2,5‐benzophenone)‐activated, telechelic aryl fluoride oligomers with different block molecular weights were successfully synthesized by the Ni(0)‐catalyzed coupling of 2,5‐dichlorobenzophenone and the end‐capping agent 4‐chloro‐4′‐fluorobenzophenone. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide‐terminated, disulfonated poly(arylene ether sulfone)s (hydrophilic) by nucleophilic, aromatic substitution to form hydrophilic–hydrophobic multiblock copolymers. High‐molecular‐weight multiblock copolymers with number‐average block lengths ranging from 3000 to 10,000 g/mol were successfully synthesized. Two separate glass‐transition temperatures were observed via differential scanning calorimetry in the transparent multiblock copolymer films when each block length was longer than 6000 g/mol. Tapping‐mode atomic force microscopy also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of the block length as it increased from 6000 to 10,000 g/mol. Transparent and creasable films were solvent‐cast and exhibited moderate proton conductivity and low water uptake. These copolymers are promising candidates for high‐temperature proton‐exchange membranes in fuel cells, which will be reported separately in part II of this series. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 284–294, 2007
Quantitative Structure–Activity Relationships Study on the Ah Receptor Binding Affinities of Polybrominated Diphenyl Ethers Using a Support Vector Machine
Authors: Zheng Gang , Xiao Man , Lu Xiaohua 
Published: December 2006

AbstractPolybrominated Diphenyl Ethers (PBDEs), which are widely distributed in the environment due to their use as flame retardant, may cause long‐term health problems in humans. Their structural similarity to Polychlorinated Biphenyls (PCBs) implies their possible dioxin‐like toxicity. By the use of Partial Least Square Regression (PLS ) with Leave‐One‐Out (LOO) Cross‐Validation (CV), seven net atomic charge descriptors have been extracted from more than 80 quantum descriptors for predicting the Aryl hydrocarbon Receptor Relative Binding Affinities (RBA) of PBDEs. Using Support Vector Machines (SVM) and Radial Basis Function Neural Networks (RBFNs), the RBAs of 15 PBDE congeners have been correlated with the extracted seven quantum chemical descriptors. The SVM models generalize better than the RBFN models. The CV correlation coefficients (q2) for the SVM models based on three‐ and five‐fold CVs are 0.889 and 0.896, respectively. The good performance of the QSAR models based on net atomic charges suggests that electrostatic interactions may play important roles in the Aryl hydrocarbon Receptor (AhR) binding of PBDEs.
Quantitative Structure–Activity Relationship Study on a Series of Novel Ligands Binding to Central Benzodiazepine Receptor By Using the Combination of Heuristic Method and Support Vector Machines
Authors: Qin Shen , Liu Huanxiang , Wang Jie , Yao Xiaojun , Liu Mancang , Hu Zhide , Fan Botao 
Published: December 2006

AbstractIn this study, Heuristic Method (HM) and Support Vector Machines (SVMs) were used for Quantitative Structure–Activity Relationship (QSAR) study of a series of 2‐aryl (heteroaryl)‐2,5‐dihydropyrazolo [4,3‐c] quinolin‐3‐(3H)‐ones, which have high affinity with central Benzodiazepine Receptor (BzR). Seven molecular descriptors selected by the HM in CODESSA were used as inputs for SVM. The prediction results are in good agreement with the experimental values. The correlation coefficients R2 of the nonlinear SVM model were 0.93 and 0.96 for the training and testing sets, respectively. This paper proposes a new and effective method to design new ligands of BzR based on QSAR study.
Estimation of Phosphate Ester Hydrolysis Rate Constants. II. Acid and General Base Catalyzed Hydrolysis
Authors: Whiteside Tad , Carreira Lionel , Hilal Said 
Published: December 2006

AbstractSPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate acid and neutral hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition states of the reactant molecule. This difference is a function of the reference rate and internal and external perturbations to the reference rate. The internal perturbations are comprised of electrostatic and resonance effects. The external perturbations quantify solute‐solvent interactions based on the dielectric constant of the solvent and the steric size of substituent groups. The neutral hydrolysis model has been tested against 89 observed hydrolysis rate constants at multiple temperatures. The RMS deviation of the calculated versus observed values was 1.08 log M−1 s−1. The acid hydrolysis model has been tested on 83 rate constants over a variety of temperatures. The RMS deviation of the acid hydrolysis model was 0.41 log M−1 s−1.
A Virtual Screening Filter for Identification of Cytochrome P450 2C9 (CYP2C9) Inhibitors
Authors: Byvatov Evgeny , Baringhaus Karl‐Heinz , Schneider Gisbert , Matter Hans 
Published: December 2006

AbstractCytochrome P450 2C9 (CYP2C9) is one of the most important phase 1 metabolizing enzymes in humans for therapeutically relevant pharmaceuticals. Any new compound inhibiting this membrane‐associated protein would notably affect the metabolism of physiologically important molecules and drugs, resulting in clinically significant drug‐drug interactions. In search for computational tools to identify potential CYP2C9 inhibitors early in discovery, we present here the construction of filters based on 1100 structurally diverse molecules tested for CYP2C9 inhibition under identical conditions. Their chemical structures were encoded using various 2D descriptors including Three‐Point Pharmacophoric (3PP) fingerprints, followed by generation of statistical models using Support Vector Machines (SVM) and Partial Least Squares (PLS). This consistently led to significant and predictive models for regression and classification of CYP2C9 inhibitors. Their predictive ability was underscored by successfully applying them to different test sets of 238 diverse and 344 GPCR‐targeted compounds. Even more important for early drug discovery is the ability of these models to correctly discriminate CYP2C9 inhibitors from inactive molecules. These models collectively are able to identify true CYP2C9 inhibitors with relatively low rates of false positives. The 3PP‐based filter also allows visualizing important substructures and functional groups, which are linked to protein‐ligand interactions for CYP2C9, as illustrated for selected structure‐activity series. The application of these models to the substrate S‐warfarin, recently co‐crystallized with CYP2C9, revealed that the important substructures are indeed involved in the interaction with the CYP2C9 binding site. For example, the model correctly indicated aromatic stacking interactions with Phe114 and Phe476 as well as a hydrogen bond with Phe100. Hence, these models consistently provide guidelines for reducing CYP2C9 inhibition in novel candidate molecules.
Conformational analysis and the binding sites of nitrilotriacetamide: A computational study
Authors: Singh Ajeet , Chakraborty Shampa , Ganguly Bishwajit 
Published: December 2006

AbstractThe conformational analysis of nitrilotriacetamide has been carried out computationally, at both the semi‐empirical AM1 and density functional theory (DFT) (B3LYP/6‐31+G*) levels of theory. The lowest‐energy conformation predicted with the Monte Carlo search method, using the AM1 model, has two amide functionalities aligned on the same side; however, the DFT calculations at B3LYP/6‐31+G* predicted the global minimum with all three acetamide functionalities on the same side in the gas phase. In the aqueous phase, the DFT results predicted the orientations of amides similar to that of the reported crystal structure. The rotation barriers to transition to different low‐energy conformers of nitrilotriacetamide are lower in energy (5.0 kcal/mol) in water. The molecular electrostatic isopotentials (MESP) generated for the selected conformers at DFT level show that the nitrilotriacetamide could interact more effectively with the sodium chloride surface than that of its monomeric unit nitrilomonoacetamide. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007