bluuebunny/crossref_metadata_2025 huggingface dataset:
Specific interactions in ternary system quaternized polysulfone/mixed solvent
Authors: Filimon Anca , Avram Ecaterina , Ioan Silvia
Published: November 2008

Theoretical and experimental aspects on the specific interactions developed via electrostatic interactions and hydrogen‐bonding in a ternary system formed of a proton‐donor solvent (N,N‐dimethylformamide or methanol), a proton‐acceptor solvent (water), and a quaternized polysulfone with various contents of ionic chlorine, which indicates a proton‐acceptor character, are investigated. Thus, the interactions of the ternary systems are corrected on the basis of the association phenomena defined through association constants. Numerical values for these constants were evaluated as a function of the system composition, by mathematical simulations for an accurate adjustment of preferential adsorption, determined by the Flory–Huggins–Pouchly theoretical approach applied to the experimental data. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Orientated crystallization in drawn thermoplastic polyimide modified by carbon nanofibers
Authors: Smirnova Valentina E. , Gofman Iosif V. , Yudin Vladimir E. , Dobrovolskaya Irina P. , Shumakov Alexander N. , Didenko Andrey L. , Svetlichnyi Valentine M. , Wachtel Ellen , Shechter Rinat , Harel Hannah , Marom Gad
Published: November 2008

The solid state crystallization in drawn thermoplastic polyimide films is studied as a function of draw ratio (DR) under the effect of vapor grown carbon fiber nanoinclusions. The nucleating effect of the nanoinclusions coupled with the orientation effect of drawing generates a unique orientated layered lamellar structure, characteristic of smectic‐like mesophase. The degree of draw induced orientated crystallization increases with the content of nanoinclusions and with the DR, and is reflected in the mechanical behavior of the film. Generally, the Young's modulus and the yield point of the drawn crystalline films in the drawing direction are significantly higher compared with the noncrystalline counterparts. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Poly(methacrylic acid)‐modified chitosan for enhancement adsorption of water‐soluble cationic dyes
Authors: Xing Yun , Sun Xiaomei , Li Buhai
Published: November 2008

The preparation of poly(methacrylic acid)‐modified chitosan microspheres and its application for the removal of cationic dyes, methylene blue (MB) and malachite green (MG), in aqueous solution in a batch system were described. The modified chitosan was characterized using SEM, FTIR, and XPS analyses. The effects of the pH of the solution, contact time, and initial dye concentration were studied. The adsorption capacities of the microspheres for the two cationic dyes increased significantly after the modification because a large number of carboxyl groups were introduced. The equilibrium process was better described by the Langmuir than the Freundlich isotherm. According to the Langmuir equation, the maximum adsorption capacities were 1000.0 and 523.6 mg g−1 for MB and MG, respectively. Kinetic studies showed better correlation coefficients for a pseudo‐second‐order kinetic model, confirming that the sorption rate was controlled by a chemisorption process. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Influences of blend proportions and curing systems on dynamic, mechanical, and morphological properties of dynamically cured epoxidized natural rubber/high‐density polyethylene blends
Authors: Nakason Charoen , Jarnthong Methakarn , Kaesaman Azizon , Kiatkamjornwong Suda
Published: November 2008

Thermoplastic elastomers (TPEs) based on dynamically cured epoxidized natural rubber/high‐density polyethylene (ENR/HDPE) blends were prepared. Influence of the process oil, blend proportion, and curing systems were investigated. It was found that the oil‐extended thermoplastic vulcanizates (TPVs) exhibited better elastomeric properties and improved ease of the injection process. Increasing the proportion of ENR caused increasing elastic response of elongation at break, tension set properties, and tan δ. It was also found that the TPV treated with phenolic resin exhibited superior mechanical properties and the smallest vulcanized rubber domains. The TPV treated with the conventional peroxide co‐agent curing system showed superior strength properties but had poor elastomeric properties. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Relationships among optimism, well‐being, self‐transcendence, coping, and social support in women during treatment for breast cancer
Authors: Matthews Ellyn E. , Cook Paul F.
Published: November 2008

Objective: The impact of diagnosis and treatment for breast cancer, stressors that affect emotional well‐being, is influenced by several psychosocial factors and the relationships among them. The purpose of this study was to investigate the relationship between optimism and emotional well‐being (EWB) and the individual and combined mediation of this relationship by perceived social support (SS), problem focused coping (PFC), and self‐transcendence in women with breast cancer during radiation therapy.

Methods: Ninety‐three women receiving radiation treatment for breast cancer completed questionnaires that measured EWB, optimism, SS, PFC, and self‐transcendence.

Results: Correlational and multiple regression analysis revealed that optimism was positively related to EWB. Of the three mediators, self‐transcendence alone was found to partially mediate the relationship between optimism and EWB. The relationship between optimism and PFC was not significant. Optimism was related to SS, but its indirect effect on EWB through SS did not reach significance.

Conclusions and implications: During breast cancer treatment, the positive effects of optimism on EWB are partially mediated by a woman's level of self‐transcendence. Brief screening of women's optimism may help identify women at risk for psychological distress. Early detection and interventions to promote psychological adjustment throughout the cancer trajectory (e.g. enhancing self‐transcendence) should receive attention in future research. Copyright © 2008 John Wiley & Sons, Ltd.
Strain effect on polarized optical properties of c ‐plane GaN and m ‐plane GaN
Authors: Tao Renchun , Yu Tongjun , Jia Chuanyu , Chen Zhizhong , Qin Zhixin , Zhang Guoyi
Published: November 2008

The polarized optical property of c ‐plane and m ‐plane GaN with varying strain was discussed by analyzing the changes of relative oscillator strength (ROS) of the three transitions related to the top three valence bands. The ROS was calculated by applying the effective‐mass Hamiltonian based on k · p perturbation theory. For c ‐plane GaN, it was found that ROS of |X 〉 state and |Y 〉 state were superposed with each other. Especially, they increased with compressive strain, while that of |Z 〉 decreased in the second band. For m ‐plane GaN under compressive strain, the first three bands were dominated by |X 〉, |Z 〉 and |Y 〉 states, respectively, which led to nearly linearly‐polarized light emissions. With compressive strain, the ROS of |X 〉 state increased more rapidly than |Z 〉 state in the topmost valence band. As a result, TE mode emissions from both c ‐plane and m ‐plane GaN increased more rapidly than TM mode emission with compressive strain, leading to larger polarization degree. Experimental results of luminescences from InGaN/GaN quantum wells showed good coincidence with our theoretical calculations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of nitrogen incorporation on surface properties of silicon oxynitride films
Authors: Hong Jongin , Kim Yunseok , Paik Hanjong , No Kwangsoo , Lukes Jennifer R.
Published: November 2008

In order to investigate the surface heterogeneity of silicon oxynitride films, we observed the nanoscale variation of the surface potential by Kelvin probe force microscopy (KFM), the molecular bonding characteristics by Fourier transform infrared spectrometry (FTIR), and the wetting behavior by contact angle measurement. Nitrogen incorporation into silicon oxynitride films influenced the decrease in the surface potential and the polar component of the surface free energy. We present the first correlation between the nanoscale measurement of the surface potential and the macroscopic measurement of the surface free energy in silicon oxynitride films grown by a standard plasma‐enhanced chemical vapor deposition (PECVD) technique. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The derivation of a numerical diagnostic model for the forcing of the geopotential
Authors: Yuan Zhuojian , Wu Junjie , Cheng Xuhua , Jian Maoqiu
Published: November 2008

Simply applying the divergence operator to the horizontal velocity equation in spherical‐isobaric coordinates yields a more solvable linear geopotential equation (than the geopotential tendency and the omega equations) for diagnosing the geopotential and its anomalies responsible for global floods and droughts. This geopotential model is freed from the zero‐denominator problem caused by the observed neutral stability which affects the geopotential tendency and omega equations. The geopotential equation's forcing terms 2–5 (the direct operation results of the horizontal advection term in the velocity equation) can identify the synoptic signals mixed up by the classical divergence equation's quadratic and Jacobian terms (the manipulated results of the above terms 2–5). Solving this geopotential equation with the successive‐over‐relaxation method and the neutral stability as calculated from the reanalysis data produces reasonably good reconstructions of the global and local geopotential fields. The additional advantages of the present geopotential model over the geopotential tendency, omega and divergence models are that the geopotential model reveals and explains the following mechanisms which received less attention in previous studies. (1) The saddle patterns favour the high systems. (2) The equatorial easterlies favour the low systems. (3) The contributions of ageostrophic processes associated with jets and saddle flows to the transitions of weather patterns might be overlooked by the geopotential tendency model in which neutral stability and static instability in cold domes as well as jet‐induced inertial instability are smoothed out artificially. Copyright © 2008 Royal Meteorological Society
Bonding and correlation analysis of various Si2CO isomers on the potential energy surface
Authors: Zhou Zhong‐Jun , Liu Hui‐Ling , Yu Jian‐Kang , Yu Guang‐Tao , Huang Xu‐Ri
Published: November 2008

At various levels of theory, singlet and triplet potential energy surfaces (PESs) of Si2CO, which has been studied using matrix isolation infrared spectroscopy, are investigated in detail. A total of 30 isomers and 38 interconversion transition states are obtained at the B3LYP/6‐311G(d) level. At the higher CCSD(T)/6‐311+G(2d)//QCISD/6‐311G(2d)+ZPVE level, the global minimum 11 (0.0 kcal/mol) corresponds to a three‐membered ring singlet O‐cCSiSi (1A′). On the singlet PES, the species 12 (0.2 kcal/mol) is a bent SiCSiO structure with a 1A′ electronic state, followed by a three‐membered ring isomer Si‐cCSiO (1A′) 13 (23.1 kcal/mol) and a linear SiCOSi 14 (1Σ+) (38.6 kcal/mol). The isomers 11, 12, 13, and 14 possess not only high thermodynamic stabilities, but also high kinetic stabilities. On the triplet PES, two isomers 31 (3B2) (18.8 kcal/mol) and 37 (3A″) (23.3 kcal/mol) also have high thermodynamic and kinetic stabilities. The bonding natures of the relevant species are analyzed. The similarities and differences between C3O, C3S, SiC2O, and SiC2S are discussed. The present results are also expected to be useful for understanding the initial growing step of the CO‐doped Si vaporization processes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Are the Hirshfeld and Mulliken population analysis schemes consistent with chemical intuition?
Authors: Saha Soumen , Roy Ram Kinkar , Ayers Paul W.
Published: November 2008

In the present article, we report a comparative study between the Hirshfeld and Mulliken population analysis schemes (abbreviated as HPA and MPA, respectively). Trends of atomic charges derived from these two population analysis schemes are compared with those expected from other commonly used chemical concepts like electronegativity, inductive effects, and resonance effects. Although previous studies on intramolecular reactivity sequences demonstrated that HPA generates reliable and non‐negative (and thus physically more realistic) condensed Fukui function (FF) values, the present study reveals problems with the HPA charge partitioning technique. Specifically, HPA fails to reproduce reliable intermolecular and intramolecular charge trends in several systems. Reasons for the success and failure of HPA are discussed and a method for improving the Hirshfeld charge partitioning is proposed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Comparative study on the nonadditivity of methyl group in lithium bonding and hydrogen bonding
Authors: Li Qingzhong , Cheng Jianbo , Li Wenzuo , Gong Baoan , Sun Jiazhong
Published: November 2008

Quantum chemical calculations at the second‐order Moeller–Plesset (MP2) level with 6‐311++G(d,p) basis set have been performed on the lithium‐bonded and hydrogen‐bonded systems. The interaction energy, binding distance, bond length, and stretch frequency in these systems have been analyzed to study the nonadditivity of methyl group in the lithium bonding and hydrogen bonding. In the complexes involving with NH3, the introduction of one methyl group into NH3molecule results in an increase of the strength of lithium bonding and hydrogen bonding. The insertion of two methyl groups into NH3molecule also leads to an increase of the hydrogen bonding strength but a decrease of the lithium bonding strength relative to that of the first methyl group. The addition of three methyl groups into NH3molecule causes the strongest hydrogen bonding and the weakest lithium bonding. Although the presence of methyl group has a different influence on the lithium bonding and hydrogen bonding, a negative nonadditivity of methyl group is found in both interactions. The effect of methyl group on the lithium bonding and hydrogen bonding has also been investigated with the natural bond orbital and atoms in molecule analyses. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Determination of polybrominated biphenyls in Tasmanian devils (Sarcophilus harrisii) by gas chromatography coupled to electron capture negative ion tandem mass spectrometry or electron ionization high‐resolution mass spectrometry
Authors: Vetter Walter , Recke Roland von der , Symons Robert , Pyecroft Stephen
Published: November 2008

Two gas chromatography/mass spectrometry (GC/MS) methods for the determination of polybrominated biphenyls (PBBs) by isotope dilution analysis (IDA) using 13C12‐PBB 153 in the presence of polybrominated diphenyl ethers (PBDEs) were compared. Recovery of 13C12‐PBB 153 which was added to the extracted lipids before sample purification was commenced ranged from 88–117% (mean value 98.2 ± 8.9%). Nevertheless, IDA analysis of PBBs using 13C12‐labelled congeners is limited by the potential co‐elution of PBBs with polybrominated diphenyl ethers (PBDEs). The pair PBB 153 and BDE 154 was inspected since M+ and [M–2Br]+ ions of 13C12‐PBB 153 and BDE 154 were only separated by 4 u. Gas chromatography/electron ionization high‐resolution mass spectrometry with selected ion monitoring (GC/EI‐HRMS‐SIM) was suitable when m/z 475.7449 and m/z 477.7429 were used for 13C12‐PBB 153 because they are below the monoisotopic peak of the [M–2Br]+ fragment ion of hexaBDEs at m/z 479.7. Gas chromatography/electron capture negative ion tandem mass spectrometry selected reaction monitoring (GC/ECNI‐MS/MS‐SRM) measurements could be applied because 13C12‐PBB 153 and BDE 154 were separated by GC on a 25‐m Factor Four CP‐Sil 8MS column.

Comparative measurements with GC/EI‐HRMS‐SIM and GC/ECNI‐MSMS‐SRM were carried out with samples of Tasmanian devils from Tasmania (Australia), an endangered species due to a virus epidemy which has already proved fatal for half of the population. Both techniques verified concentrations of PBB 153 in the range 0.3–11 ng/g lipids with excellent agreement of the levels in all but two samples. The PBB residue pattern demonstrated that PBB pollution originated from the previous discharge with technical hexabromobiphenyl which is dominated by PBB 153. Other congeners such as PBB 132 and PBB 138 were detected in the Tasmanian devils but the proportions relative to PBB 153 were lower than in the technical product. Samples of healthy and affected Tasmanian devils showed no significant difference in the PBB pollution level. The PBB concentrations in the Tasmanian devils were significantly below those causing toxic effects. On the other hand, PBB concentrations were one level or even higher than PBDEs. Copyright © 2008 John Wiley & Sons, Ltd.
Stress of needle specimen on the three‐dimensional atom probe (3DAP)
Authors: Mayama N. , Yamashita C. , Kaito T. , Nojima M. , Owari M.
Published: November 2008

The three‐dimensional atom probe (3DAP) is one of the ways to image materials three‐dimensionally on atomic scale. However, some technical issues in 3DAP are still unresolved. One of them is the rupture of a specimen that sometimes occurs when the atoms are field‐evaporated at the apex of a needle specimen. This is caused by the high electric stress around the tip of the needle specimen. One way to reduce the stress is to enlarge the taper angle of the needle specimen. In this study, adapting this idea to 3DAP, we estimated the appropriate values of not only the taper angle of the needle specimen but also its diameter, length, radius of curvature, and distance between the tip and local electrode by simulation. Furthermore, we calculated the average value of field‐induced stress on each plane for z‐direction in the specimen. Copyright © 2008 John Wiley & Sons, Ltd.
Response of a magneto‐rheological fluid damper subjected to periodic forcing in a high frequency limit
Authors: Litak G. , Borowiec M. , Kasperek R.
Published: November 2008

We have explored vibrations of a single‐degree of freedom oscillator with a magneto‐rheological damper subjected to kinematic excitations in a high frequency limit. Using fast and slow scales decoupling procedure we derived an effective damping coefficient in the limit of high frequency excitation. Damping characteristics, as functions of velocity, change considerably especially by terminating the singular non‐smoothness points. This effect was more transparent for a larger control parameter which was defined as the product of the excitation amplitude and its frequency.
Comparative analysis of rocky reef fish community structure in coastal islands of south-eastern Brazil
Authors: de Carvalho Teixeira Chaves Laís , Monteiro-Neto Cassiano
Published: November 2008

Reef fish community structures at three sites in the state of Rio de Janeiro (Pedra Vermelha (PV), Cabo Frio Island—Arraial do Cabo; Mãe Island (MI), Itaipu—Niterói; Comprida Island (CI), Cagarras Archipelago—Rio de Janeiro) were investigated to assess differences in fish species composition, density and distribution of trophic groups, between sites, correlating the observed patterns of fish distribution with environmental factors. Thirty-six visual strip-transects yielded 67 species of 34 families. Studied locations shared at least 40% of all species, mostly of western Atlantic distribution. The three sites presented significant differences on diversity, density and species dominance. CI presented the highest values, except for total density, which was higher at PV, probably due to its partial degree of protection. MI showed the lowest values, suggesting possible impacts from the proximity to the shore. The main trophic categories were omnivores followed by mobile invertebrate feeders, in similarity to what was previously observed for south-eastern Brazil. Inherent habitat features of each location regarding depth, declivity, visibility and rugosity resulted in different species distribution and dominance patterns.
IS SHOULDER DYSTOCIA WITH BRACHIAL PLEXUS INJURY PREVENTABLE?
Authors: HAMILTON EMILY F , CIAMPI ANTONIO , DYACHENKO ALINA , LERNER HENRY M , MINER LOUISE , SANDMIRE HERBERT F.
Published: November 2008

The sequelae of shoulder dystocia with persistent brachial plexus injury (BPI) are among the most serious of obstetrical complications. Shoulder dystocia with BPI generally places second or third in the list of the top causes of permanent birth-related neonatal injuries. Apart from the devastating medical and social consequences of lifelong impairment for the family, ensuing litigation with its allegations regarding poor care exacts a heavy toll on the medical profession.
The pollen metamorphosis phenomenon in Panax ginseng, Aralia elata and Oplopanax elatus; an addition to discussion concerning the Panax affinity in Araliaceae
Authors: Reunov Arkadiy A. , Reunova Galina D. , Alexandrova Yana N. , Muzarok Tamara I. , Zhuravlev Yuriy N.
Published: November 2008

To find more morphological characteristics useful for discussion on aralian or non-aralian Panax affinity, pollen morphological diversity was comparatively analysed in P. ginseng, Aralia elata and Oplopanax elatus collected during their pollination periods. In the anthers of both the buds and open flowers, the pollen average diameter varied between some species-specific maximum and minimal measurement. However, the larger pollen grains were typically found in the buds whereas the smaller pollen prevailed in the open flowers, testifying to the pollen size diminution during anther maturation. Based on this finding, the subsequent examination of pollen according to size decrease was put into operation as a method of pollen modification for the study. The structural mechanisms of pollen metamorphosis were identified as not being species specific but rather universal. These mechanisms are suggested to be the shrinkage of the pollen vegetative cytoplasm, the intine enlargement, the deepening of three colporate apertures provided by exine sunken into enlarged intine areas, the aperture accretion as well as the transformation of the exine from thick/sculptured into thin/less sculptured. During ‘size-reducing metamorphosis’, the pollen grains changed dramatically, going through a species-specific set of intermediate morphs to the final species-specific morphotype. In P. ginseng this morphotype is round (diameter is about 16 μm), in A. elata it is round with a single projection (diameter is about 15 μm) and in O. elatus it is ovoid with a single projection (average diameter is about 18 μm). In addition, every species is peculiar in having the unique vegetative cytoplasm inclusions and individual construction of the largest pollen exine. From a phylogenetic perspective, these findings presumably add support to the option of equal remoteness of P. ginseng from A. elata and O. elatus. The characteristics found seem to be suitable for examination of Panax affinity, by the subsequent study of more Araliaceae representatives.
The Ideology of Wifely Submission: A Challenge for Feminism?
Authors: Snyder-Hall R. Claire
Published: November 2008

This article examines the writings of women who explicitly embrace wifely
submission, including those who advocate corporal punishment. Through a close
reading of primary sources, the article seeks to illuminate the biblical
literalist theology that underlies the ideology of wifely submission and to
explain the reasons why many heterosexual women find such an ideology appealing.
While many readers might be tempted to dismiss such women as antifeminist, the
question of desire that their writing raises goes to the heart of a major
challenge faced by contemporary feminist theory, which since the “sex
wars” often remains divided between those who accept whatever women
choose as feminist and those who stand in judgment of other women's
choices. This article uses the case of wifely submission to examine the problem
of desire, the concept of consent, and the benefits and limitations of
“choice” discourse within feminist theory. It argues for a
middle-ground approach that respects women as agents in their own lives, while
also engaging them in reflective conversation about desire and its
ramifications.
“Backlash” and Its Utility to Political Scientists
Authors: Thomas Sue
Published: November 2008

The global warming backlash, the managed care backlash, the Bush backlash, the corporate backlash, the 9/11 backlash, the Obama backlash, the Clinton backlash, the Foreign Intelligence Surveillance Act (FISA) bill backlash, the antigay backlash, the immigration backlash, the backlashes against globalization, student testing, the social, economic, and political progress of Latinos, African Americans, and Asian Americans, and, central to this “Critical Perspectives,” the backlash against the feminist movement—these were just some of the many politically related backlashes that appeared when I performed a general Google search of the words: “backlash” and “politics” in July of 2008.
Heterogeneous reactions of methacrolein and methyl vinyl ketone: Kinetics and mechanisms of uptake and ozonolysis on silicon dioxide
Authors: Chen Z. M. , Jie C. Y. , Li S. , Wang H. L. , Wang C. X. , Xu J. R. , Hua W.
Published: November 2008

Methacrolein (MAC) and methyl vinyl ketone (MVK), two major first‐generation products in the oxidation of isoprene, play important roles in tropospheric chemistry. However, little is known about their heterogeneous fate. Here we investigated the heterogeneous reactions of MAC and MVK on particles of silicon dioxide (SiO2), the major constituent of mineral dust in the troposphere, under simulated tropospheric conditions. We first investigated the adsorption and desorption processes. It was found that MAC and MVK molecules were adsorbed onto the surface of SiO2 particles by van der Waals forces and hydrogen bonding forces in a non‐reactive state, and the presence of water vapor did not result in the formation of new substances but could decrease the adsorption ability by consuming isolated hydroxyl groups on the surface of SiO2 particles. The initial adsorption and desorption rates, initial uptake coefficients, and adsorption concentrations at equilibrium were determined at different relative humidities. Notably, in the desorption process, a considerable amount of MAC or MVK molecules remained on SiO2 particles in dry air but were almost completely desorbed in high‐humid air. We also investigated the heterogeneous ozonolysis of MAC and MVK adsorbed onto SiO2 particles, determining product yields at different relative humidities. The heterogeneous ozonolysis of MAC and MVK adsorbed onto SiO2 particles yielded formaldehyde and methylglyoxal as the major secondary carbonyl products and formic acid and acetic acid as the major organic acid products, as in their gas‐phase ozonolysis. However, the yield of two major organic peroxides, methyl hydroperoxide and hydroxymethyl hydroperoxide, was much greater in their heterogeneous ozonolysis than in their gas‐phase ozonolysis. The mechanisms of heterogeneous ozonolysis of MAC and MVK onto the SiO2 surface are deduced.
Biomorphodynamics: Physical‐biological feedbacks that shape landscapes
Authors: Murray A. B. , Knaapen M. A. F. , Tal M. , Kirwan M. L.
Published: November 2008

Plants and animals affect morphological evolution in many environments. The term “ecogeomorphology” describes studies that address such effects. In this opinion article we use the term “biomorphodynamics” to characterize a subset of ecogeomorphologic studies: those that investigate not only the effects of organisms on physical processes and morphology but also how the biological processes depend on morphology and physical forcing. The two‐way coupling precipitates feedbacks, leading to interesting modes of behavior, much like the coupling between flow/sediment transport and morphology leads to rich morphodynamic behaviors. Select examples illustrate how even the basic aspects of some systems cannot be understood without considering biomorphodynamic coupling. Prominent examples include the dynamic interactions between vegetation and flow/sediment transport that can determine river channel patterns and the multifaceted biomorphodynamic feedbacks shaping tidal marshes and channel networks. These examples suggest that the effects of morphology and physical processes on biology tend to operate over the timescale of the evolution of the morphological pattern. Thus, in field studies, which represent a snapshot in the pattern evolution, these effects are often not as obvious as the effects of biology on physical processes. However, numerical modeling indicates that the influences on biology from physical processes can play a key role in shaping landscapes and that even local and temporary vegetation disturbances can steer large‐scale, long‐term landscape evolution. The prevalence of biomorphodynamic research is burgeoning in recent years, driven by societal need and a confluence of complex systems–inspired modeling approaches in ecology and geomorphology. To make fundamental progress in understanding the dynamics of many landscapes, our community needs to increasingly learn to look for two‐way, biomorphodynamic feedbacks and to collect new types of data to support the modeling of such emergent interactions.
Estimating stream chemistry during the snowmelt pulse using a spatially distributed, coupled snowmelt and hydrochemical modeling approach
Authors: Molotch Noah P. , Meixner Thomas , Williams Mark W.
Published: November 2008

We used remotely sensed snow cover data and a physically based snowmelt model to estimate the spatial distribution of energy fluxes, snowmelt, snow water equivalent, and snow cover extent over the different land cover types within the Green Lakes Valley, Front Range, Colorado. The spatially explicit snowpack model was coupled to the Alpine Hydrochemical Model (AHM), and estimates of hydrochemistry at the basin outlflow were compared with the baseline AHM approach, which implicitly prescribes snowmelt. The proportions of total meltwater production from soil, talus, and rock subunits were 46, 25, and 29%, respectively, for the baseline simulation without our advanced snowmelt representation. Conversely, simulations in which the AHM was coupled to our distributed snowmelt model ascribed the largest meltwater production to talus (47%) subunits, with 37% ascribed to soil and 16% ascribed to rock. Accounting for these differences in AHM reduced model overestimates of cation concentration during snowmelt; modeled Ca2+ estimates explained 82 and 70% (P values < 0.01) of observations with and without the coupled model, respectively. Similarly, the coupled model explained more variability in nitrate concentrations, with 83 versus 70% (P values < 0.01) explained by the coupled and baseline models, respectively. Early snowmelt over talus subunits was not detected at the basin outflow, confirming earlier reports that deeper flow paths are needed in biogeochemical models of alpine systems. Realistic treatment of snowmelt within these models will allow efforts to improve understanding of flow paths and predict catchment response to increases in atmospheric deposition and climate change.
Response of the northern stratospheric polar vortex to the seasonal alignment of QBO phase transitions
Authors: Anstey J. A. , Shepherd T. G.
Published: November 2008

This study considers the strength of the Northern Hemisphere Holton‐Tan effect (HTE) in terms of the phase alignment of the quasi‐biennial oscillation (QBO) with respect to the annual cycle. Using the ERA‐40 Reanalysis, it is found that the early winter (Nov–Dec) and late winter (Feb–Mar) relation between QBO phase and the strength of the stratospheric polar vortex is optimized for subsets of the 44‐year record that are chosen on the basis of the seasonality of QBO phase transitions at the 30 hPa level. The timing of phase transitions serves as a proxy for changes in the vertical structure of the QBO over the whole depth of the tropical stratosphere. The statistical significance of the Nov–Dec (Feb–Mar) HTE is greatest when 30 hPa QBO phase transitions occur 9–14 (4–9) months prior to the January of the NH winter in question. This suggests that there exists for both early and late winter a vertical structure of tropical stratospheric winds that is most effective at influencing the interannual variability of the polar vortex, and that an early (late) winter HTE is associated with an early (late) progression of QBO phase towards that structure. It is also shown that the seasonality of QBO phase transitions at 30 hPa varies on a decadal timescale, with transitions during the first half of the calendar year being relatively more common during the first half of the tropical radiosonde wind record. Combining these two results suggests that decadal changes in HTE strength could result from the changing seasonality of QBO phase transitions.
Tide gauge datum continuity at Brest since 1711: France's longest sea‐level record
Authors: Wöppelmann Guy , Pouvreau Nicolas , Coulomb Alain , Simon Bernard , Woodworth Philip L.
Published: November 2008

The issue of a possible tide gauge datum discontinuity at Brest, caused by the bombing of the city in August 1944, is discussed. This issue is very important, as many scientists have used this long record to derive a long‐term sea level trend estimate for use within global sea level rise studies. A detailed analysis of historical leveling information, and comparison of sea level data between adjacent stations, proved to be worthwhile, even beyond this initial scope of the study: it led to an accurate datum connection between recently rediscovered 18th century sea level data (back to 1711) and those of the present day. The study provides additional evidence that the onset of recent rapid sea level rise most likely took place in the late 19th century, in agreement with the nearby Liverpool sea‐level record and with independent results from sediment cores collected in salt marshes located in both hemispheres.
Small‐scale, localized electromagnetic waves observed by Cluster: Result of magnetosphere‐ionosphere interactions
Authors: Streltsov A. V. , Karlsson T.
Published: November 2008

We present results from a numerical study of small‐scale, localized electromagnetic structures measured by the Cluster satellites on May 19, 2002, in the nightside magnetosphere. A comprehensive analysis of these structures by Karlsson et al. (2004), Johansson et al. (2004) and Marklund et al. (2004) demonstrates that they can be interpreted as two relatively stationary magnetic field‐aligned currents and higher frequency shear Alfvén waves, populating the region in between, but no explanation was given of what physical mechanism may cause such particular combination of waves and currents in the plasma sheet boundary layer. Our simulations demonstrate that these structures can be interpreted as a characteristic signature of the active ionospheric feedback, which appears when large‐scale magnetic field‐aligned currents interact with the ionosphere.
Crucial role of ring current H+ in electromagnetic ion cyclotron wave dispersion relation: Results from global simulations
Authors: Gamayunov K. V. , Khazanov G. V.
Published: November 2008

The effect of ring current (RC) H+ in the real part of electromagnetic ion cyclotron (EMIC) wave dispersion relation is studied on the global magnetospheric scale. The simulations of the 2–3 May 1998 storm are done using our model of the He+‐mode EMIC waves self‐consistently interacting with RC ions. The wave model describes EMIC waves bouncing between the off‐equatorial magnetic latitudes, which correspond to the bi‐ion hybrid frequencies in conjugate hemispheres, along with tunneling across the reflection zones and subsequent strong absorption in the ionosphere. This model explicitly includes the EMIC wave growth/damping, propagation, refraction, reflection, and tunneling in a multi‐ion magnetospheric plasma. An analysis of the wave observations is presented and strongly supports our wave model. The main findings from our simulations can be summarized as follows: First, RC H+ only contributes a few percent to the total plasma density near the inner edge of the plasmasphere boundary layer, but it can dominate outside the plasmapause. About 90% of the RC H+ density in the dawn MLT sector is formed by the suprathermal ions (≲2 keV), while a major contribution in dusk comes from the 10–100 keV ions, allowing not more than 10‐20% for the suprathermal ions. Second, RC H+ in the real part of the wave dispersion relation increases local growth rate leading to a dramatic change in the wave global patterns. The “new” EMIC waves are generated not only on the plasmapause, as expected from previous global simulations, but also inside and outside the plasmapause consistent with the observations.
Experimental measurements of permeability evolution during triaxial compression of initially intact crystalline rocks and implications for fluid flow in fault zones
Authors: Mitchell T. M. , Faulkner D. R.
Published: November 2008

Detailed experimental studies of the development of permeability of crustal rock during deformation are essential in helping to understand fault mechanics and constrain larger‐scale models that predict bulk fluid flow within the crust. Permeability is particularly enhanced in the damage zone of faults, where microfracture damage accumulates under stress less than that required for macroscopic failure. Experiments performed in the prefailure region can provide data directly applicable to these zones of microfracture damage surrounding faults. The strength, permeability, and pore fluid volume evolution of initially intact crystalline rocks (Cerro Cristales granodiorite and Westerly granite) under increasing differential load leading to macroscopic failure has been determined at water pore pressures of 50 MPa and varying effective pressures from 10 to 50 MPa. Permeability is seen to increase by up to, and over, 2 orders of magnitude prior to macroscopic failure, with the greatest increase seen at lowest effective pressures. Postfailure permeability is shown to be over 3 orders of magnitude higher than initial intact permeabilities and approaches the lower limit of predicted in situ bulk crustal permeabilities. Increasing amplitude cyclic loading tests show permeability‐stress hysteresis, with high permeabilities maintained as differential stress is reduced and the greatest permeability increases are seen between 90 and 99% of the failure stress. Prefailure permeabilities are nearly 7 to 9 orders of magnitude lower than that predicted by some high‐pressure diffusive models suggesting that if these models are correct, microfracture matrix flow cannot dominate, and that bulk fluid flow must be dominated by larger‐scale structures such as macrofractures. We present a model, based on our data, in which the permeability of a highly stressed fault tip process zone in low‐permeability crystalline rocks increases by more than 2 orders of magnitude. Stress reduction related to the onward migration of the fault tip close damage zone cracks, while some permeability is maintained due to hysteresis from permanent microfracture damage.
Force chains in seismogenic faults visualized with photoelastic granular shear experiments
Authors: Daniels Karen E. , Hayman Nicholas W.
Published: November 2008

Natural faults have many characteristics in common with granular systems, including granular fault rocks, shear localization, and stick‐slip dynamics. We present experimental results which provide insight into granular behavior in natural faults. The experiments allow us to directly image force chains within a deforming granular media through the use of photoelastic particles. The experimental apparatus consists of a spring‐pulled slider block which deforms the photoelastic granular aggregate at a constant velocity. Particles that carry more of the load appear brighter when viewed through crossed polarizers, making the internal stresses optically accessible. The resulting pattern is a branched, anisotropic force chain network inclined to the shear zone boundaries. Under both constant volume and dilational boundary conditions, deformation occurs predominantly through stick‐slip displacements and corresponding force drops. The particle motion and force chain changes associated with the deformation can either be localized to the central slip zone or span the system. The sizes of the experimental slip events are observed to have power law (Gutenberg‐Richter‐like) distributions; the minimum dimensions of events and the behavior of force chains suggest that a particle scale controls the lower limits of the power law distributions. For large drops in pulling force with slip, the shape of the size distributions is strongly affected by the choice of boundary condition, while for small to moderate drops the probability distributions are approximately independent of boundary condition. These size‐dependent variations in stick‐slip behavior are associated with different spatial patterns: on average, small events typically correspond to localized force chain or particle rearrangements, whereas large events correspond to system‐spanning changes. Such force chain behavior may be responsible for similar size‐dependent behaviors of natural faults.
Large interannual CO2 and energy exchange variability in a freshwater marsh under consistent environmental conditions
Authors: Rocha Adrian V. , Goulden Michael L.
Published: November 2008

We analyzed a 5‐year record of the CO2 and energy exchange, Aboveground Net Primary Production (ANPP), maximum Leaf Area Index (LAImax), and Enhanced Vegetation Index (EVI) for a Typha marsh in Southern California. The marsh was a net source of carbon over the study, despite high rates of ANPP. Interannual Net Ecosystem Production (NEP) variability was the largest that has been reported for any terrestrial ecosystem and was attributed to changes in maximum photosynthetic rates (GEEmax). The variation in energy and mass exchange was coupled between years; years with higher than average rates of carbon uptake were associated with lower than average sensible heat fluxes. Remotely sensed measures of surface greenness (EVI) were closely related to GEEmax variation, providing further evidence of interannual variability. We were unable to attribute the fluctuations in GEEmax to the direct effects of weather on ecosystem physiology, or to interannual variation in LAImax. GEE did not vary systematically with air temperature or the presence of standing water in the marsh; GEEmax did not vary with LAImax between years. Rather, interannual variation in carbon exchange at the SJFM resulted from shifts in the marsh's production efficiency (the rates of gross or net CO2 exchange per LAI) that were not caused by changes in the weather. Our findings challenge the assumptions that interannual variation of land‐atmosphere exchange is universally caused by the direct effect of weather on ecosystem physiology, and that an ecosystem's physiological response to the physical environment is consistent from year‐to‐year.
Standing litter as a driver of interannual CO2 exchange variability in a freshwater marsh
Authors: Rocha A. V. , Potts D. L. , Goulden M. L.
Published: November 2008

The San Joaquin Freshwater Marsh (SJFM) is a seasonally flooded Typha wetland in Southern California that is characterized by high rates of Aboveground Net Primary Production (ANPP) and a large accumulation of standing leaf litter. The ANPP, Gross and Net Ecosystem CO2 Exchange (GEE and NEE), and Enhanced Vegetation Index (EVI) at the SJFM fluctuate by ∼40% from year to year, in ways that are not directly attributable to variation in weather or the maximum green Leaf Area Index (LAImax). We tested the hypothesis that this variation is caused by a negative feedback between ANPP, the buildup of leaf litter, shading of green leaves by litter, a reduction in GEE and NEE, and a subsequent reduction in ANPP. Litter manipulations on replicated plots demonstrated that the presence of standing litter decreased plot‐level NEE by 17 to 47% and surface EVI by 25 to 48%, even as green Leaf Area Index (LAIgreen) was held constant. Plot level NEE and surface EVI remained tightly correlated, and largely decoupled from LAIgreen, as standing litter was varied. This pattern paralleled that observed for the entire marsh, where NEE and EVI remained tightly correlated, and largely decoupled from LAImax, from year to year. Correcting LAIgreen and LAImax for the amount of shading caused by standing litter improved the correlations between LAI and EVI and NEE, indicating that EVI and NEE are most sensitive to the amount of unshaded LAI. The accumulation of standing litter at the SJFM decouples the relationships between LAI and EVI and NEE, and appears to be important for controlling the interannual variability observed at the site.
Numerical solution of an inverse conductive boundary value problem
Authors: Yaman F.
Published: November 2008

In this paper, we derive a numerical solution of an inverse obstacle scattering problem with conductive boundary condition. The aim of the direct problem is the computation of the scattered field for a given arbitrarily shaped cylinder with conductive boundary condition on its surface.The inverse problem considered here is the reconstruction of the conductivity function of the scatterer from meausurements of the far field. A potential approach is used to obtain boundary layer integral equations both for the solution of the direct and the inverse problem. The numerical solutions of the integral equations which contain logarithmically singular kernels are evaluated by a Nyström method and Tikhonov regularization is used to solve the first kind of integral equations occuring in the solution of the inverse problem. Finally, numerical simulations are carried out to test the applicability and the effectiveness of the method.
Determining forecast and decision horizons for reservoir operations under hedging policies
Authors: You Jiing‐Yun , Cai Ximing
Published: November 2008

Hedging policies for reservoir operations makes a small deficit in current supply to reduce the probability of a severe water shortage in the future. One of the critical questions for hedging research is how long the forecast period should be so that reliable inflow forecast in the period can be used for decision making under hedging. Decision makers always hope to look further into the future; however, the longer the forecast period, the more uncertain and less reliable the involved information, which will have a diminishing influence on decision making. For dynamic reservoir operation optimization models, the decision horizon (DH) may be defined as the initial periods in which decisions are not affected by forecast data beyond a certain period, defined as the forecast horizon (FH). This paper determines FH with given DH for dynamic reservoir operation problems through both theoretical and numerical analysis. We use order of magnitude analysis and numerical modeling to identify the impact of various factors such as water stress level (the deficit between water availability and demand), reservoir size, inflow uncertainty, evaporation rate, and discount rate. Three types of inflow time series are used: stationary, nonstationary with seasonality, and random walk. Results show that inflow characteristics and reservoir capacity have major impacts on FH when water stress is modest; larger reservoir capacity and the deterministic component of inflow such as seasonality require a longer FH. Economic factors have strong impacts when water stress levels are high.