bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new insight into the mechanism of influence of different inorganic salts on optical properties of water‐soluble cationic conjugated polymers
Authors: Liu Qianqian , Lü Xiaodan , Geng Lei , Lü Changli 
Published: May 2011

AbstractThe water‐soluble conjugated polyelectrolyte poly{2,5‐bis[3‐(N,N,N‐triethylammoniumbromide)‐1‐oxapropyl]‐1,4‐phenylenevinylene} (P2) was synthesized and the influences of different inorganic salts on the optical properties of the polyelectrolyte were studied. New absorption and emission peaks at longer wavelength can be observed in the case of P2 with addition of different concentrations of Cl− or NO3−, whereas addition of I− or ClO4− only induces a red shift. Interestingly, addition of SO42− or F− does not result in considerable changes in optical spectra. Through UV‐visible spectrometry, photoluminescence, 1H NMR and cyclic voltammetry, we showed that the nature of the inorganic salts brings these different changes. The special structure of the $\prod{_{4}}^{6}$ bond of NO3− and the large electronegativity of chlorine lead to an electron transfer between the conjugated polymer and the negative ions. The large radius of I− and the weak electron withdrawing ability of ClO4− only bring a red shift of optical spectra. In addition, SO42− and F− do not affect the spectra significantly, except that the fluorescence intensity falls slightly indicating that P2 is not sensitive to these ions. Copyright © 2011 Society of Chemical Industry
Perceptions of declining classmate and teacher support following the transition to high school: Potential correlates of increasing student mental health difficulties
Authors: Wit David J. De , Karioja Kim , Rye B. J. , Shain Martin 
Published: May 2011

AbstractEmotional support from classmates and teachers is a powerful protective factor in averting or reducing student mental health problems. Yet, longitudinal evidence indicates that there is decreased support from these groups as students advance to higher grade levels, a change that may be linked to diminishing mental health. This study followed 2,616 students from 23 high schools to test the hypothesis that perceptions of declining classmate and teacher support are associated with declining mental health. Growth curve analysis revealed significant decreases in support and self‐esteem and increases in symptoms of depression and social anxiety. Boys demonstrated steeper declines than girls in classmate support and self‐esteem and sharper increases in depression. As hypothesized, declining classmate and teacher support was associated with worsening self‐esteem and depression. Only declines in classmate support were associated with increases in social anxiety. Results were similar across gender categories. Implications for school‐based practices targeting social support are discussed. © 2011 Wiley Periodicals, Inc.
Surface‐Grafted conjugated polymers for hybrid cellulose materials
Authors: Peterson Joseph J. , Willgert Markus , Hansson Susanne , Malmström Eva , Carter Kenneth R. 
Published: May 2011

AbstractConjugated polymers were grafted onto cellulose substrates in an effort to create a general method for the synthesis of conjugated polymer/cellulose hybrid materials. In this report, we describe the grafting of poly(fluorene), poly(fluorenevinylene), and a poly(fluorene‐ethynylene‐phenylene) onto modified cellulose paper substrates using Suzuki, Heck, and Sonogashira‐type polymerizations, respectively. The application of these three widely used coupling chemistries to surface‐grafted conjugated polymers on cellulose provides a general route to cellulose‐based hybrid materials tunable with almost any aromatic repeat structure for specific applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Alternating narrow band gap copolymers derived from indeno[1,2‐b]fluorene and thiophene‐cored‐thieno[3,4‐b]pyrazine derivatives—Synthesis, characterization and comparative studies of photochemical stability
Authors: Xia Yangjun , Tong Junfeng , Li Bin , Wang Chenglong , Liu Hongzhong 
Published: May 2011

AbstractAlternating narrow band gap (NBG) conjugated polymers derived from 6,6′,12,12′‐tetraoctylindeno[1,2‐b]fluorene (IF) and 2,3‐dimethyl‐5,7‐dithien‐2‐yl‐thieno[3,4‐b]pyrazine (DTTP), 2,3‐diphenyl‐5,7‐dithien‐2‐yl‐thieno[3,4‐b]pyrazine (DPTP) or 2,3‐dioctyl‐5,7‐dithien‐2‐yl‐thieno[3,4‐b]pyrazine (DOTP), named as PIF‐DTTP, PIF‐DPTP, and PIF‐DOTP, respectively, were synthesized by Suzuki coupling reaction and characterized. The photochemical stabilities of the copolymers and copolymer derived from IF and 5,7‐dithien‐2‐yl‐thieno[3,4‐b]pyrazine (DTP) were investigated by the UV absorptions, PL spectra, FT‐IR spectra, and photovoltaic properties of the copolymers as a function of UV irradiation time. The studies revealed that the degradation of thieno[3,4‐b]pyrazine (TP) ring under UV irradiation can be retarded or eliminated by introducing phenyl group into the 2,3‐positions of TP ring, and indicated that 2,3‐diphenylthieno[3,4‐b]pyrazine could be used as durable electron deficient moiety to achieve donor–acceptor NBG‐conjugated polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis of low grafting density molecular brush from a poly(N‐alkyl urea peptoid) backbone
Authors: Chen Xiaoping , Ayres Neil 
Published: May 2011

AbstractThe synthesis of a molecular brush was accomplished by combining step‐growth polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization in a “grafting from” methodology. A symmetrical N‐alkyl urea peptoid sixmer containing alkyne functional groups was prepared using a divergent strategy, and the structure of the product was confirmed using NMR spectroscopy and mass spectrometry. A step‐growth process was used to prepare a linear poly(N‐alkyl urea peptoid) by reacting the diamine‐functionalized N‐alkyl urea peptoid sixmer with a diisocyanate. RAFT chain transfer agents were coupled to the poly(N‐alkyl urea peptoid) backbone through a copper‐catalyzed azide/alkyne cycloaddition reaction. The afforded macro‐RAFT agent was used to sequentially polymerize styrene and tert‐butyl acrylate block copolymer arms from the poly(N‐alkyl urea peptoid) backbone. The tert‐butyl groups were removed using dilute trifluoroacetic acid affording hydrophilic polyacrylic acid segments. The molecular brushes were observed to generate micelles in aqueous solution. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Poly[(sodium sulfamate/carboxylate)isoprene‐b‐2‐vinyl pyridine] block polyampholytes: Synthesis and self‐assembly in aqueous media
Authors: Mantzaridis Christos , Pispas Stergios 
Published: May 2011

AbstractWe report on the synthesis of poly[(sodium sulfamate/carboxylate) isoprene‐b‐2‐vinyl pyridine] block polyampholytes (SCPI‐P2VP), utilizing anionic polymerization and post polymerization functionalization reactions. The precursor poly(isoprene‐b‐(2‐vinylpyridine)) diblock copolymers (PI‐P2VP), containing a polyisoprene (PI) block with high 1,4 microstructure, were prepared by anionic polymerization high vacuum techniques, in two steps, involving change of the polymerization solvent. Subsequent functionalization of the PI block with chlorosulfonyl isocyanate, introduced sulfamate and carboxylate groups in the polymer chains and produced the desired block polyampholytes. The successful synthesis of the polyampolytes was corroborated by elemental analysis and IR spectroscopy measurements. The self‐assembly behaviour of the aforementioned polyampholytes was studied in aqueous solutions as a function of pH, by aid of dynamic and static light scattering, zeta potential, fluorescence spectroscopy and atomic force microscopy. Experimental results indicate that the block polyampholytes form micellar structures with P2VP cores and SCPI coronas at pH > 6, whereas more compact nanoparticles are formed at pH < 4 from the complexation of positively charged P2VP and SCPI, stabilized by excess negative charges of uncomplexed SCI segments. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Separation of single‐walled carbon nanotubes with aromatic group functionalized polymethacrylates and building blocks contribution to the enrichment
Authors: Pan Xiaoyong , Chan‐Park Mary B. 
Published: May 2011

AbstractWe previously showed that in N,N‐dimethylformamide (DMF), poly(9‐anthracenylmethyl methacrylate) (PAMMA) and poly(2‐naphthylmethacrylate) selectively disperse semiconducting and metallic single‐walled carbon nanotubes (SWNTs), respectively. We have also proposed a new noncovalent polymer interaction based on photon induced dipole–dipole interaction to account for the metallicity‐based selectivity. In this article, we investigate two other polymethacrylates, that is, poly(benzyl methacrylate) (PBMA) and poly(methylmethacrylate)‐co‐(9‐anthracenylmethyl acrylate) (PMMA‐c‐PAMA) in the light of our previously proposed photon‐induced dipole–dipole interaction. We find that PBMA and PMM‐c‐PAMMA in DMF show no metallicity selectivity. The different selective behavior of the four polymers in DMF manifests the decisive influence of the side aromatic group in determining their metallicity selectivity. The nonpreferential energy transfer from PMMA‐c‐PAMA to SWNTs and the nonoverlap of PBMA fluorescence (in the ultraviolet range) with nanotube absorption account for their nonselectivity of specific nanotube species. Further, the parallel relationship between the diameters of extracted tube species and the affinity between polymers and solvents suggests the leading role of the polymeric conformation on the diameter selectivity. A sufficient (i.e., 2 weeks) standing time of the SWNTs solution after sonication, during which the polymers presumably optimize their conformation to the SWNTs, was found to be essential to the enrichment. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Interactions in a blend of two polymers greatly differing in glass transition temperature
Authors: Kratochvíl Jaroslav , Šturcová Adriana , Sikora Antonín , Dybal Jiří 
Published: May 2011

AbstractBlends of poly(N‐methyldodecano‐12‐lactam) PMDL with poly(4‐vinyphenol) PVPh have been studied by the DSC and ATR FTIR methods. The difference in glass transition temperature Tg between the components is 206 °C. A single composition‐dependent Tg suggests miscibility of the system, that is, homogeneity on the scale of about 10 nm. Fitting of the equation of Brostow et al. to the Tg data indicates relatively strong specific interactions and high complexity of the system. The Schneider's equation applied separately to low‐ and high‐PVPh regions provides good agreement with experiment; the calculated curves cross at the point of PVPh weight fraction 0.27. In the low‐PVPh region, the analysis indicates weak interactions with predominance of segment homocontacts and strong involvement of conformational entropy. In the high‐PVPh region, strong specific interactions predominate and entropic effects are suppressed. Composition dependences of the heat capacity difference at Tg and the width of glass transition indicate strong interactions in the system and existence of certain heterogeneities on segmental level, respectively. According to ATR FTIR, hydrogen bonds between PVPh as proton donor and PMDL as proton acceptor induce miscibility in blends of higher PVPh content (above about 0.28 weight fraction). In low‐PVPh blends, it is conformational entropy that enables intimate intermolecular mixing. Hydrogen bonds adopt several (distorted) geometries and are on average stronger than average hydrogen bonds formed in self‐associating PVPh. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Characterization and Tribological Behaviour of Siloxane‐based Plasma Coatings on HNBR Rubber
Authors: Verheyde Bert , Havermans Danny , Vanhulsel Annick 
Published: May 2011

AbstractA cold atmospheric pressure plasma jet (PlasmaSpot) was developed in our department and was successfully used to deposit siloxane‐based coatings on elastomer materials for tribological improvement. This paper reports on the deposition of a low‐friction atmospheric plasma coating on an HNBR sample using (3‐aminopropyl)triethoxysilane (APEO) as precursor. The chemical structure of the coating was examined with XPS and FTIR spectroscopy. Monitoring the top surface of the coating by optical microscopy showed 2–3 µm wide cracks appearing in the coating some days after deposition. Furthermore, a migration of waxes was seen from the bulk rubber through the cracks. The chemical nature of these products was revealed by FTIR analysis. Although these waxes act as lubricant and are added to the rubber for better processability, a tribological evaluation in a ball‐on‐disc test rig revealed that they did not contribute to the lower friction coefficient. A significant decrease of the friction coefficient was measured for the plasma coated HNBR sample compared to the untreated HNBR sample. magnified image
A Century (1910–2008) of Change in a Collapsing Pingo, Parry Peninsula, Western Arctic Coast, Canada
Authors: Mackay J. R. , Burn C. R. 
Published: May 2011

ABSTRACTAn isolated, eroding pingo at the southern end of Parry Peninsula, N.W.T., Canada was first photographed in about 1910. The photograph allows examination of a century of landform change. Since 1910, the pingo crater pond has drained, the north side of the pingo has become well vegetated, the serrated crest has been smoothed, and the lake bottom has become colonised by willows and other vegetation. The height of the feature was over 100 ft (30 m) in 1910 and is now about 50 ft (15–17 m). The erosion of the pingo has probably been dominated by the strong southerly katabatic winds in the area, as the vegetation on the south side of the pingo is poorly developed in comparison with the north side. A secondary cause of erosion has been the numerous excavations by ground squirrels (Spermophilus parryii) and foxes (Vulpes lagopus) on the slopes of the pingo. It is unusual to detect change of collapsed pingos near the western Arctic coast of Canada unless ground ice is exposed in the core or on the sides of the pingo. The increases since 1996 in height and cover of willows are the first record of such change from western Arctic Canada. Copyright © 2011 John Wiley & Sons, Ltd.
Pedotransfer functions for isoproturon sorption on soils and vadose zone materials
Authors: Moeys Julien , Bergheaud Valérie , Coquet Yves 
Published: May 2011

AbstractBACKGROUND: Sorption coefficients (the linear KD or the non‐linear KF and NF) are critical parameters in models of pesticide transport to groundwater or surface water. In this work, a dataset of isoproturon sorption coefficients and corresponding soil properties (264 KD and 55 KF) was compiled, and pedotransfer functions were built for predicting isoproturon sorption in soils and vadose zone materials. These were benchmarked against various other prediction methods.RESULTS: The results show that the organic carbon content (OC) and pH are the two main soil properties influencing isoproturon KD. The pedotransfer function is KD = 1.7822 + 0.0162 OC1.5 − 0.1958 pH (KD in L kg−1 and OC in g kg−1). For low‐OC soils (OC < 6.15 g kg−1), clay and pH are most influential. The pedotransfer function is then KD = 0.9980 + 0.0002 clay − 0.0990 pH (clay in g kg−1). Benchmarking KD estimations showed that functions calibrated on more specific subsets of the data perform better on these subsets than functions calibrated on larger subsets.CONCLUSION: Predicting isoproturon sorption in soils in unsampled locations should rely, whenever possible, and by order of preference, on (a) site‐ or soil‐specific pedotransfer functions, (b) pedotransfer functions calibrated on a large dataset, (c) KOC values calculated on a large dataset or (d) KOC values taken from existing pesticide properties databases. Copyright © 2011 Society of Chemical Industry
Translocation and degradation of pyrazosulfuron‐ethyl in rice soil
Authors: Singh Neera , Singh Shashi B 
Published: May 2011

AbstractBACKGROUND: Pyrazosulfuron‐ethyl {ethyl 5‐[(4,6‐dimethoxypyrimidin‐2‐ylcarbamoyl)‐sulfamoyl]‐1‐methylpyrazole‐4‐carboxylate} is a new rice herbicide belonging to the sulfonylurea group. This study reports the translocation of 14C‐pyrazosulfuron‐ethyl to rice plants and its degradation in rice‐planted and unplanted soil.RESULTS: Pyrazosulfuron‐ethyl did not show any appreciable translocation to rice shoots, as 14C‐activity translocated to the aerial portion never exceeded 1% of the initially applied 14C‐activity over a 25 day period. Results suggested that the dissipation of pyrazosulfuron‐ethyl from soils followed first‐order kinetics with a half‐life of 5.5 and 6.9 days in rice‐planted and unplanted soils respectively. HPLC analysis of the organic extract of soil samples showed the formation of three metabolites, namely ethyl 5‐(aminosulfonyl)‐1‐methyl‐1‐H‐pyrazole‐4‐carboxylate, 5‐[({[(4,6‐dimethoxy‐2 pyrimidinyl)‐amino]‐carbonyl} amino)‐sulfonyl]‐1‐methyl‐1H‐pyrazole‐4‐carboxylic acid and 2‐amino‐4,6‐dimethoxy pyrimidine, in both rice‐planted and unplanted soils.CONCLUSION: The study indicates that pyrazosulfuron‐ethyl was a short‐lived compound in the soil and was degraded relatively faster in rice‐planted soil than in unplanted soil. The herbicide did not show any appreciable translocation to rice plants. Copyright © 2011 Society of Chemical Industry
Extensive studies of large‐amplitude Kelvin–Helmholtz billows in the lower atmosphere with VHF middle and upper atmosphere radar
Authors: Fukao Shoichiro , Luce Hubert , Mega Tomoaki , Yamamoto Masayuki K. 
Published: May 2011

AbstractIn the present work, characteristics of large‐amplitude (>150 m) Kelvin–Helmholtz (KH) billows in the lower atmosphere are analysed, with emphasis on the turbulent properties. First, past studies are reviewed. Almost all the studies reported gradient Richardson number (Ri) close to 0.25. Results of observations in the height range 1.32–20.34 km using 46.5 MHz middle and upper atmosphere radar (MUR; Japan, 34.85°N, 136.10°E) are then described. A total of ∼600 h of data at high vertical and range resolutions was used. Except for very few cases, trains of KH braids are not followed by layer splitting, which can eventually result from turbulent mixing. A particular event shows some sort of turbulent plumes at the interface between a nearly neutral layer and a stable layer in the tropopause region. These turbulent plumes likely arose as the result of entrainment at the stable layer interface produced by still active turbulent mixing. Statistics on the characteristics of the KH billows are also presented. Large‐amplitude KH billows in the lower atmosphere were only present less than 0.6% of the time and height. The typical depth, horizontal wavelength and depth‐to‐wavelength ratio of the KH braids are about 600 m, 2600 m and 0.22, respectively. They are thus relatively shallow and the quasi‐absence of layer splitting may suggest that they are more frequently generated when Ri falls just below 0.25 (so that the large‐amplitude KH billows are not sufficiently energetic for breaking and mixing). Vertical shears of horizontal wind are about 23 ms−1 km−1 on average. Finally, attempts at estimating (maximum) energy dissipation rate ε and (minimum) vertical eddy diffusivity K are made. Mean values of εmax and Kmin are typically ∼1 mW kg−1 (77% in the range 0.15–3.0 mW kg−1) and ∼5 m2 s−1 (70% in the range 1–10 m2 s−1), respectively. Copyright © 2011 Royal Meteorological Society
Observation of the marine atmospheric boundary layer in the Gulf of Guinea during the 2006 boreal spring
Authors: Leduc‐Leballeur Marion , Eymard L. , de Coëtlogon G. 
Published: May 2011

AbstractIn situ, satellite and model analyses data in April–July 2006 are used to investigate the links between sea surface temperature (SST) and the marine atmospheric boundary layer (MABL) in the Gulf of Guinea. The study region between 10°W and 6°E is divided into three areas with different characteristics: the North Area (4.5°N to 1°N) with the wettest atmosphere and the warmest SST, the Upwelling Area (1°N to 4°S) with the strongest SST decrease, and the South Area (4°S to 8°S) with a drier atmosphere and a more slowly decreasing SST than in the Upwelling Area. The key zone of the air‐sea interactions in this region seems to be the SST front between North and Upwelling Areas. On the one hand, the study of the MABL on either side of the front shows a well‐mixed layer between the surface and about 500 m high, sensitive to surface variations, which gets shallower (deeper) when the SST decreases (increases). The MABL height (about 1500 m) follows the same variations but is not exactly collocated with the SST variations. On the other hand, the observation of the MABL across the SST front shows a strengthening of southeasterlies in the South Area coinciding with a strong SST decrease in the Upwelling Area. In the latter, the wind weakens above the colder SST. Besides, in the North Area, the wind strengthens above the warmer SST. However, the wind acceleration spans from the equator to 2°N in April and as far as 4°N in June. A convergence zone is observed in the vicinity of 2°N in April, suggesting a convection activity there, favoured by the SST front. Copyright © 2011 Royal Meteorological Society
Cooperative control of autonomous systems
Authors: Holsapple Raymond W. , Kingston Derek B. 
Published: May 2011

AbstractThis special issue contains a collection of papers on task assignment problems, path planning problems, cooperative control problems and coordinated control problems. Each of the authors has concentrated his or her efforts on both theory development and application to enhance the overall academic contribution of each paper. The theme of this special issue was motivated by the many collaborations of the Cooperative and Intelligent Control of Unmanned Aerial Vehicles (UAV) group in the Control Science Center of Excellence of the Air Force Research Laboratory (AFRL). Published 2011. This article is a US Government work and is in the public domain in the USA.
Positive state‐bounding observer for positive interval continuous‐time systems with time delay
Authors: Li Ping , Lam James 
Published: May 2011

SUMMARYThis paper is concerned with the problem of positive observer synthesis for positive systems with both interval parameter uncertainties and time delay. Conventional observers may no longer be applicable for such kind of systems due to the positivity constraint on the observers, and they only provide an estimate of the system state in an asymptotic way. A pair of positive observers with state‐bounding feature is proposed to estimate the state of positive systems at all times in this paper. A necessary and sufficient condition for the existence of desired observers is first established, and the observer matrices can be obtained easily through the solutions of a set of linear matrix inequalities (LMIs). Then, to reduce the error signal between the system state and its estimates, an iterative LMI algorithm is developed to compute the optimized state‐bounding observer matrices. Finally, a numerical example is presented to show the effectiveness and applicability of the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.