bluuebunny/crossref_metadata_2025 huggingface dataset:
Dimethyl sulfide in the Amazon rain forest
Authors: Jardine K. , Yañez‐Serrano A. M. , Williams J. , Kunert N. , Jardine A. , Taylor T. , Abrell L. , Artaxo P. , Guenther A. , Hewitt C. N. , House E. , Florentino A. P. , Manzi A. , Higuchi N. , Kesselmeier J. , Behrendt T. , Veres P. R. , Derstroff B. , Fuentes J. D. , Martin S. T. , Andreae M. O.
Published: December 2014

Surface‐to‐atmosphere emissions of dimethyl sulfide (DMS) may impact global climate through the formation of gaseous sulfuric acid, which can yield secondary sulfate aerosols and contribute to new particle formation. While oceans are generally considered the dominant sources of DMS, a shortage of ecosystem observations prevents an accurate analysis of terrestrial DMS sources. Using mass spectrometry, we quantified ambient DMS mixing ratios within and above a primary rainforest ecosystem in the central Amazon Basin in real‐time (2010–2011) and at high vertical resolution (2013–2014). Elevated but highly variable DMS mixing ratios were observed within the canopy, showing clear evidence of a net ecosystem source to the atmosphere during both day and night in both the dry and wet seasons. Periods of high DMS mixing ratios lasting up to 8 h (up to 160 parts per trillion (ppt)) often occurred within the canopy and near the surface during many evenings and nights. Daytime gradients showed mixing ratios (up to 80 ppt) peaking near the top of the canopy as well as near the ground following a rain event. The spatial and temporal distribution of DMS suggests that ambient levels and their potential climatic impacts are dominated by local soil and plant emissions. A soil source was confirmed by measurements of DMS emission fluxes from Amazon soils as a function of temperature and soil moisture. Furthermore, light‐ and temperature‐dependent DMS emissions were measured from seven tropical tree species. Our study has important implications for understanding terrestrial DMS sources and their role in coupled land‐atmosphere climate feedbacks.
Full‐wave multiscale anisotropy tomography in Southern California
Authors: Lin Yu‐Pin , Zhao Li , Hung Shu‐Huei
Published: December 2014

Understanding the spatial variation of anisotropy in the upper mantle is important for characterizing the lithospheric deformation and mantle flow dynamics. In this study, we apply a full‐wave approach to image the upper‐mantle anisotropy in Southern California using 5954 SKS splitting data. Three‐dimensional sensitivity kernels combined with a wavelet‐based model parameterization are adopted in a multiscale inversion. Spatial resolution lengths are estimated based on a statistical resolution matrix approach, showing a finest resolution length of ~25 km in regions with densely distributed stations. The anisotropic model displays structural fabric in relation to surface geologic features such as the Salton Trough, the Transverse Ranges, and the San Andreas Fault. The depth variation of anisotropy does not suggest a lithosphere‐asthenosphere decoupling. At long wavelengths, the fast directions of anisotropy are aligned with the absolute plate motion inside the Pacific and North American plates.
Phytoplankton plasticity drives large variability in carbon fixation efficiency
Authors: Ayata Sakina‐Dorothée , Lévy Marina , Aumont Olivier , Resplandy Laure , Tagliabue Alessandro , Sciandra Antoine , Bernard Olivier
Published: December 2014

Phytoplankton C:N stoichiometry is highly flexible due to physiological plasticity, which could lead to high variations in carbon fixation efficiency (carbon consumption relative to nitrogen). However, the magnitude, as well as the spatial and temporal scales of variability, remains poorly constrained. We used a high‐resolution biogeochemical model resolving various scales from small to high, spatially and temporally, in order to quantify and better understand this variability. We find that phytoplankton C:N ratio is highly variable at all spatial and temporal scales (5–12 molC/molN), from mesoscale to regional scale, and is mainly driven by nitrogen supply. Carbon fixation efficiency varies accordingly at all scales (±30%), with higher values under oligotrophic conditions and lower values under eutrophic conditions. Hence, phytoplankton plasticity may act as a buffer by attenuating carbon sequestration variability. Our results have implications for in situ estimations of C:N ratios and for future predictions under high CO2 world.
Variation of the global electric circuit and Ionospheric potential in a general circulation model
Authors: Mareev E. A. , Volodin E. M.
Published: December 2014

A general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modeling the global electric circuit short‐time variability and long‐term evolution. The ionospheric potential parameterization is proposed which takes into account quasi‐stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The diurnal, seasonal, and interannual variations of the ionospheric potential (IP) are modeled and compared with available data. Numerical simulations suggest that the IP decreases in the mean with the global warming due to increasing greenhouse gas emission (by about 10% during the 21st century if the Representative Concentration Pathway 8.5 Wm−2 scenario is assumed). At the same time the lightning flash rate increases with global warming by about 5 fl/s per degree. Interannual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature in the Pacific Ocean (El Niño area).
Return stroke speed of cloud‐to‐ground lightning estimated from elve hole radii
Authors: Blaes P. R. , Marshall R. A. , Inan U. S.
Published: December 2014

We present the first measurements of the lightning return stroke speed that directly relate to the current return stroke, as opposed to its optical manifestation. The shape of elves is determined by the electromagnetic pulse (EMP) radiation pattern at D region altitudes, which is in turn controlled by the geometry and current propagation properties of the return stroke channel. In particular, numerical simulation of the EMP‐ionosphere interaction shows a strong relationship between the elve “hole” radius and the current return stroke speed. The hole radii are measured from a data set of 55 elves observed with the PIPER photometer. Using these radii observations in conjunction with numerical simulations of the EMP, we perform Bayesian inference to estimate the distribution of return stroke speeds. The results show a maximum a posteriori probability return stroke speed estimate of 0.64c for elve producing lightning.
Mars Express radio‐occultation data: A novel analysis approach
Authors: Grandin M. , Blelly P.‐L. , Witasse O. , Marchaudon A.
Published: December 2014

The Mars Express Radio Science (MaRS) experiment on board Mars Express has been providing radio‐occultation data since early 2004. The analysis method currently used to retrieve neutral atmosphere and ionosphere profiles is based on the resolution of a complex inverse problem. The solution to such a problem is obtained under strong assumptions on the atmosphere and the ionosphere and with some limitations. Here we developed a novel method for radio‐occultation data analysis based on a direct approach which overcomes some of the difficulties related to the standard inversion. This new method is based on a numerical model of the atmosphere and the ionosphere of Mars computing the propagation of the radio waves from the spacecraft to the receiver on Earth. The main interest of such an approach lies in the intrinsic and coherent coupling between the neutral part and the ionized part of the planetary environment, which gives physical constrains on the retrieved profiles. We have applied this new method to radio occultation experiments performed by MaRS, and we present the results obtained in two different occultation configurations. We discuss the differences which emerge from the standard analysis and the gain that such a method can give to the analysis of planetary environments.
Effects of a low‐viscosity lower crust on topography and gravity at convergent mountain belts during gravitational instability of mantle lithosphere
Authors: Molnar Peter , Houseman Gregory A.
Published: December 2014

We examine the gravitational stability of a stratified structure consisting of a low‐density crust through which viscosity decreases exponentially, over a denser mantle lithosphere of constant viscosity, which in turn overlies an inviscid, slightly less dense layer like the asthenosphere. The most important aspect of the viscosity structure is the contrast in viscosity at the Moho. Surface uplift above a mantle downwelling is greatest when the viscosity contrast at the Moho is negligible. The surface is depressed when the viscosity of the lowermost crust is much greater than mantle viscosity. For a wide range of viscosity structures, calculated gravity anomalies and in particular admittances (ratios of the Fourier transform of gravity to that of topography) produced by Rayleigh‐Taylor instability differ markedly from those observed across convergent mountain belts. In particular, whereas values of calculated admittance are negative, or very small, observed admittances are consistently positive. Thus, if downwelling of mantle lithosphere directly beneath mountain ranges plays an important role in the construction of mountain belts, it cannot be the main process that induces crustal thickening.
Beyond‐laboratory‐scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation
Authors: Ishibashi Takuya , Watanabe Noriaki , Hirano Nobuo , Okamoto Atsushi , Tsuchiya Noriyoshi
Published: December 2014

The present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory‐scale granite fractures under confining stress. As a significant result of the laboratory investigation, the contact area in fracture plane was found to be virtually independent of scale. By combining this characteristic with the self‐affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. Validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture‐fracture length relations, which are reported in the literature, for natural fractures. The present study finally predicts conceivable scale dependencies of fluid flows through joints (fractures without shear displacement) and faults (fractures with shear displacement). Both joint and fault aperture distributions are characterized by a scale‐independent contact area, a scale‐dependent geometric mean, and a scale‐independent geometric standard deviation of aperture. The contact areas for joints and faults are approximately 60% and 40%. Changes in the geometric means of joint and fault apertures (µm), em, joint and em, fault, with fracture length (m), l, are approximated by em, joint = 1 × 102 l0.1 and em, fault = 1 × 103 l0.7, whereas the geometric standard deviations of both joint and fault apertures are approximately 3. Fluid flows through both joints and faults are characterized by formations of preferential flow paths (i.e., channeling flows) with scale‐independent flow areas of approximately 10%, whereas the joint and fault permeabilities (m2), kjoint and kfault, are scale dependent and are approximated as kjoint = 1 × 10−12 l0.2 and kfault = 1 × 10−8 l1.1.
Synthetic earthquake catalogs simulating seismic activity in the Corinth Gulf, Greece, fault system
Authors: Console Rodolfo , Carluccio Roberto , Papadimitriou Eleftheria , Karakostas Vassilis
Published: December 2014

The characteristic earthquake hypothesis is the basis of time‐dependent modeling of earthquake recurrence on major faults. However, the characteristic earthquake hypothesis is not strongly supported by observational data. Few fault segments have long historical or paleoseismic records of individually dated ruptures, and when data and parameter uncertainties are allowed for, the form of the recurrence distribution is difficult to establish. This is the case, for instance, of the Corinth Gulf Fault System (CGFS), for which documents about strong earthquakes exist for at least 2000 years, although they can be considered complete forM ≥ 6.0 only for the latest 300 years, during which only few characteristic earthquakes are reported for individual fault segments. The use of a physics‐based earthquake simulator has allowed the production of catalogs lasting 100,000 years and containing more than 500,000 events of magnitudes ≥ 4.0. The main features of our simulation algorithm are (1) an average slip rate released by earthquakes for every single segment in the investigated fault system, (2) heuristic procedures for rupture growth and stop, leading to a self‐organized earthquake magnitude distribution, (3) the interaction between earthquake sources, and (4) the effect of minor earthquakes in redistributing stress. The application of our simulation algorithm to the CGFS has shown realistic features in time, space, and magnitude behavior of the seismicity. These features include long‐term periodicity of strong earthquakes, short‐term clustering of both strong and smaller events, and a realistic earthquake magnitude distribution departing from the Gutenberg‐Richter distribution in the higher‐magnitude range.
Second‐order structure function analysis of scatterometer winds over the Tropical Pacific
Authors: King Gregory P. , Vogelzang Jur , Stoffelen Ad
Published: December 2014

Kolmogorov second‐order structure functions are used to quantify and compare the small‐scale information contained in near‐surface ocean wind products derived from measurements by ASCAT on MetOp‐A and SeaWinds on QuikSCAT. Two ASCAT and three SeaWinds products are compared in nine regions (classified as rainy or dry) in the tropical Pacific between 10°S and 10°N and 140° and 260°E for the period November 2008 to October 2009. Monthly and regionally averaged longitudinal and transverse structure functions are calculated using along‐track samples. To ease the analysis, the following quantities were estimated for the scale range 50 to 300 km and used to intercompare the wind products: (i) structure function slopes, (ii) turbulent kinetic energies (
), and (iii) vorticity‐to‐divergence ratios. All wind products are in good qualitative agreement, but also have important differences. Structure function slopes and
differ per wind product, but also show a common variation over time and space. Independent of wind product, longitudinal slopes decrease when sea surface temperature exceeds the threshold for onset of deep convection (about 28°C). In rainy areas and in dry regions during rainy periods, ASCAT has larger divergent
than SeaWinds, while SeaWinds has larger vortical
than ASCAT. Differences between SeaWinds and ASCAT vortical
and vorticity‐to‐divergence ratios for the convectively active months of each region are large.
Thermal variations in the South China Sea associated with the eastern and central Pacific El Niño events and their mechanisms
Authors: Liu Qin‐Yan , Wang Dongxiao , Wang Xin , Shu Yeqiang , Xie Qiang , Chen Ju
Published: December 2014

In this study, we investigate the interannual variability of the sea surface temperature (SST) in the South China Sea (SCS) associated with two types of El Niño, namely, the eastern Pacific (EP) El Niño and the central Pacific (CP) El Niño. First, double warm peaks can occur during both types of El Niño events in the SCS. However, the strong warm basin mode can only develop in the EP El Niño, while the warm semibasin mode exists during the CP El Niño. Associated with an anomalous positive (negative) net surface heat flux in the EP (CP) El Niño, along with a shallower thermocline with weaker (stronger) northeasterly wind anomalies, the SST anomalies become warmer (cooler) in the developing autumn. Over the background of cooling SST in autumn of CP El Niño, therefore, only a weak warming can occur in the subsequent years, which is limited in the western boundary area under the forcing of warm ocean advection. Second, the SST oscillation periods are different in these two types of El Niño. The SST evolution in the EP El Niño is negative‐positive with a quasi‐biennial oscillation, but that in the CP El Niño is positive‐negative‐positive‐negative with an annual oscillation. It seems that the double cooling in the CP El Niño is phase‐locked to the late autumn season.
The effect of stratospheric sulfur from Mount Pinatubo on tropospheric oxidizing capacity and methane
Authors: Bândă Narcisa , Krol Maarten , van Noije Twan , van Weele Michiel , Williams Jason E. , Sager Philippe Le , Niemeier Ulrike , Thomason Larry , Röckmann Thomas
Published: December 2014

The eruption of Mount Pinatubo in 1991 injected a large amount of SO2 into the stratosphere, which formed sulfate aerosols. Increased scattering and absorption of UV radiation by the enhanced stratospheric SO2 and aerosols decreased the amount of UV radiation reaching the troposphere, causing changes in tropospheric photochemistry. These changes affected the oxidizing capacity of the atmosphere and the removal rate of CH4 in the years following the eruption. We use the three‐dimensional chemistry transport model TM5 coupled to the aerosol microphysics module M7 to simulate the evolution of SO2 and sulfate aerosols from the Pinatubo eruption. Their effect on tropospheric photolysis frequencies and concentrations of OH and CH4 is quantified for the first time. We find that UV attenuation by stratospheric sulfur decreased the photolysis frequencies of both ozone and NO2 by about 2% globally, decreasing global OH concentrations by a similar amount in the first 2 years after the eruption. SO2 absorption mainly affects OH primary production by ozone photolysis, while aerosol scattering also alters OH recycling. The effect of stratospheric sulfur on global OH and CH4 is dominated by the effect of aerosol extinction, while SO2 absorption contributes by 12.5% to the overall effect in the first year after the eruption. The reduction in OH concentrations causes an increase in the CH4 growth rate of 4 and 2 ppb/yr in the first and second years after the eruption, respectively, contributing 11 Tg to the 27 Tg observed CH4 burden change in late 1991 and early 1992.
A review of volume‐area scaling of glaciers
Authors: Bahr David B. , Pfeffer W. Tad , Kaser Georg
Published: December 2014

Volume‐area power law scaling, one of a set of analytical scaling techniques based on principals of dimensional analysis, has become an increasingly important and widely used method for estimating the future response of the world's glaciers and ice caps to environmental change. Over 60 papers since 1988 have been published in the glaciological and environmental change literature containing applications of volume‐area scaling, mostly for the purpose of estimating total global glacier and ice cap volume and modeling future contributions to sea level rise from glaciers and ice caps. The application of the theory is not entirely straightforward, however, and many of the recently published results contain analyses that are in conflict with the theory as originally described by Bahr et al. (1997). In this review we describe the general theory of scaling for glaciers in full three‐dimensional detail without simplifications, including an improved derivation of both the volume‐area scaling exponent γ and a new derivation of the multiplicative scaling parameter c. We discuss some common misconceptions of the theory, presenting examples of both appropriate and inappropriate applications. We also discuss potential future developments in power law scaling beyond its present uses, the relationship between power law scaling and other modeling approaches, and some of the advantages and limitations of scaling techniques.
Nowcast model for low‐energy electrons in the inner magnetosphere
Authors: Ganushkina N. Yu. , Amariutei O. A. , Welling D. , Heynderickx D.
Published: December 2014

We present the nowcast model for low‐energy (<200 keV) electrons in the inner magnetosphere, which is the version of the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) for electrons. Low‐energy electron fluxes are very important to specify when hazardous satellite surface‐charging phenomena are considered. The presented model provides the low‐energy electron flux at all L shells and at all satellite orbits, when necessary. The model is driven by the real‐time solar wind and interplanetary magnetic field (IMF) parameters with 1 h time shift for propagation to the Earth's magnetopause and by the real time Dst index. Real‐time geostationary GOES 13 or GOES 15 (whenever each is available) data on electron fluxes in three energies, such as 40 keV, 75 keV, and 150 keV, are used for comparison and validation of IMPTAM running online. On average, the model provides quite reasonable agreement with the data; the basic level of the observed fluxes is reproduced. The best agreement between the modeled and the observed fluxes are found for <100 keV electrons. At the same time, not all the peaks and dropouts in the observed electron fluxes are reproduced. For 150 keV electrons, the modeled fluxes are often smaller than the observed ones by an order of magnitude. The normalized root‐mean‐square deviation is found to range from 0.015 to 0.0324. Though these metrics are buoyed by large standard deviations, owing to the dynamic nature of the fluxes, they demonstrate that IMPTAM, on average, predicts the observed fluxes satisfactorily. The computed binary event tables for predicting high flux values within each 1 h window reveal reasonable hit rates being 0.660–0.318 for flux thresholds of 5 ·104–2 ·105 cm−2 s−1 sr−1 keV−1 for 40 keV electrons, 0.739–0.367 for flux thresholds of 3 ·104–1 ·105 cm−2 s−1 sr−1 keV−1 for 75 keV electrons, and 0.485–0.438 for flux thresholds of 3 ·103–3.5 ·103 cm−2 s−1 sr−1 keV−1 for 150 keV electrons but rather small Heidke Skill Scores (0.17 and below). This is the first attempt to model low‐energy electrons in real time at 10 min resolution. The output of this model can serve as an input of electron seed population for real‐time higher‐energy radiation belt modeling.
Agricultural virtual water flows within the United States
Authors: Dang Qian , Lin Xiaowen , Konar Megan
Published: December 2014

Trade plays an increasingly important role in the global food system, which is projected to be strained by population growth, economic development, and climate change. For this reason, there has been a surge of interest in the water resources embodied in international trade, referred to as “global virtual water trade.” In this paper, we present a comprehensive assessment of virtual water flows within the United States (U.S.), a country with global importance as a major agricultural producer and trade power. This is the first study of domestic virtual water flows based upon intranational food transfer empirical data and it provides insight into how the properties of virtual water transfers vary across scales. We find that the volume of virtual water flows within the U.S. is equivalent to 51% of international flows, which is slightly higher than the U.S. food value and mass shares, due to the fact that water‐intensive meat commodities comprise a much larger fraction of food transfers within the U.S.. The U.S. virtual water flow network is more social, homogeneous, and equitable than the global virtual water trade network, although it is still not perfectly equitable. Importantly, a core group of U.S. States is central to the network structure, indicating that both domestic and international trade may be vulnerable to disruptive climate or economic shocks in these U.S. States.
History of Clinical Medicine
Authors: Weatherall MW , Weatherall DJ
Published: December 2014

The history of clinical medicine reflects both the complex nature of the relationship between doctors and patients, and the slow evolution of knowledge in natural philosophy and, more recently, the biomedical sciences. This article provides an overview of these issues as they have developed over the last 2500 years, specifically focussing on the application of science and natural philosophy to the control and management of human disease. Despite the expansion of, and remarkable advances in, the biomedical sciences during the past two centuries, the multilayered complexities of disease processes and the ever changing environments of sick people ensure that clinical medicine still remains very much a mix of applied science and the art of healing.

Key Concepts:

The history of clinical medicine reflects the slow development of the science and art of medical care set against the background of changes in political, cultural, environmental and economic factors.

The Greco‐Roman concept that health reflects the balance of the four humours lasted for two millennia.

Disease was believed to reflect an imbalance of the humours.

During the Renaissance the humoural concept of disease was discarded and the fields of anatomy, chemistry and surgery began to influence the development of medical practice.

During the seventeenth century there were major advances in the understanding of human physiology and the importance of clinical practice at the bedside was emphasised.

During the eighteenth and nineteenth centuries the scientific basis of clinical care and the beginnings of statistical approaches to its applications continued to develop.

During the twentieth and early years of the twenty‐first centuries there were dramatic advances in every aspect of scientific medicine, culminating in the description of disease at the molecular level, and accompanied by changes in the patterns of provision of health care in many countries.
The Importance of Implementation Fidelity Data for Evaluating Program Effectiveness
Authors: Fisher Rochelle , Smith Kristen , Finney Sara , Pinder Kathryn
Published: December 2014

The authors explain implementation fidelity and demonstrate its impact on real–life programming.
Strain Gradient in Micro‐Hardness Testing and Structural Relaxation in Metallic Glasses
Authors: Champion Yannick , Perrière Loïc
Published: December 2014

An analytical model is proposed to quantitatively describe the depth‐dependence of Vickers micro‐hardness in metallic glasses. The approach is based on a shear bands distribution‐induced strain gradient during testing and was used to analyze thermal relaxation in the Zr55Cu20Al10Ni10Ti5, Ni53Nb20Zr8Ti10Co6Cu3, and Mg65Cu12.5Ni12.5MM10 metallic glasses. It was shown that a decrease of the free volume leads systematically to a decrease of the alloy hardness. This analysis also gives an evaluation of the shear band thickness and the role of the elastic properties in the depth‐dependence of the Vickers micro‐hardness.
Epoxy Toughening with Low Graphene Loading
Authors: Park Yong Tae , Qian Yuqiang , Chan Clement , Suh Taewon , Nejhad Mehrdad Ghasemi , Macosko Christopher W. , Stein Andreas
Published: December 2014

The toughening effects of graphene and graphene‐derived materials on thermosetting epoxies are investigated. Graphene materials with various structures and surface functional groups are incorporated into an epoxy resin by in situ polymerization. Graphene oxide (GO) and GO modified with amine‐terminated poly(butadiene‐acrylonitrile) (ATBN) are chosen to improve the dispersion of graphene nanosheets in epoxy and increase their interfacial adhesion. An impressive toughening effect is observed with less than 0.1 wt% graphene. A maximum in toughness at loadings as small as 0.02 wt% or 0.04 wt% is observed for all four types of graphene studied. An epoxy nanocomposite with ATBN‐modified GO shows a 1.5‐fold improvement in fracture toughness and a corresponding 2.4‐fold improvement in fracture energy at 0.04 wt% of graphene loading. At such low loadings, these graphene‐type materials become economically feasible components of nanocomposites. A microcrack mechanism is proposed based on microscopy of the fracture surfaces. Due to the stress concentration by graphene nanosheets, microcracks may be formed to absorb the fracture energy. However, above a certain graphene concentration, the coalescence of microcracks appears to facilitate crack propagation, lowering the fracture toughness. Crack deflection and pinning likely contribute to the slow increase in fracture toughness at higher loadings.
Relating the Physical Structure and Optoelectronic Function of Crystalline TIPS‐Pentacene
Authors: Sharifzadeh Sahar , Wong Cathy Y. , Wu Hao , Cotts Benjamin L. , Kronik Leeor , Ginsberg Naomi S. , Neaton Jeffrey B.
Published: December 2014

Theory and experiment are combined to investigate the nature of low‐energy excitons within ordered domains of 6,13‐bis(triisopropylsilylethynyl)‐pentacene (TIPS‐PEN) polycrystalline thin films. First‐principles density functional theory and many‐body perturbation theory calculations, along with polarization‐dependent optical absorption spectro‐microscopy on ordered domains, show multiple low‐energy absorption peaks that are composed of excitonic states delocalized over several molecules. While the first absorption peak is composed of a single excitonic transition and retains the polarization‐dependent behavior of the molecule, higher energy peaks are composed of multiple transitions with optical properties that can not be described by those of the molecule. The predicted structure‐dependence of polarization‐dependent absorption reveals the exact inter‐grain orientation within the TIPS‐PEN film. Additionally, the degree of exciton delocalization can be significantly tuned by modest changes in the solid‐state structure and the spatial extent of the excitations along a given direction is correlated with the degree of electronic dispersion along the same direction. These findings pave the way for tailoring the singlet fission efficiency of organic crystals by solid‐state structure.
Enhanced Light‐Harvesting by Integrating Synergetic Microcavity and Plasmonic Effects for High‐Performance ITO‐Free Flexible Polymer Solar Cells
Authors: Yao Kai , Xin Xu‐Kai , Chueh Chu‐Chen , Chen Kung‐Shih , Xu Yun‐Xiang , Jen Alex K.‐Y.
Published: December 2014

In this work, a high‐performance ITO‐free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO‐free microcavity architecture. By carefully controlling the sizes of embedded Ag nanoprisms and their doping positons in the stratified device, a significant enhancement in power conversion efficiency (PCE) is shown from 8.5% (reference microcavity architecture) to 9.4% on flexible substrates. The well‐manipulated plasmonic resonances introduced by the embedded Ag nanoprisms with different LSPR peaks allow the complementary light‐harvesting with microcavity resonance in the regions of 400–500 nm and 600–700 nm, resulting in the substantially increased photocurrent. This result not only signifies that the spectral matching between the LSPR peaks of Ag nanoprisms and the relatively low absorption response of photoactive layer in the microcavity architecture is an effective strategy to enhance light‐harvesting across its absorption region, but also demonstrates the promise of tailoring two different resonance bands in a synergistic manner at desired wavelength region to enhance the efficiency of PSCs.
Bacterial Attachment to Polymeric Materials Correlates with Molecular Flexibility and Hydrophilicity
Authors: Sanni Olutoba , Chang Chien‐Yi , Anderson Daniel G. , Langer Robert , Davies Martyn C. , Williams Philip M. , Williams Paul , Alexander Morgan R. , Hook Andrew L.
Published: December 2014

A new class of material resistant to bacterial attachment has been discovered that is formed from polyacrylates with hydrocarbon pendant groups. In this study, the relationship between the nature of the hydrocarbon moiety and resistance to bacteria is explored, comparing cyclic, aromatic, and linear chemical groups. A correlation is shown between bacterial attachment and a parameter derived from the partition coefficient and the number of rotatable bonds of the materials' pendant groups. This correlation is applicable to 86% of the hydrocarbon pendant moieties surveyed, quantitatively supporting the previous qualitative observation that bacteria are repelled from poly(meth)acrylates containing a hydrophilic ester group when the pendant group is both rigid and hydrophobic. This insight will help inform and predict the further development of polymers resistant to bacterial attachment.
Interfacial Friction Control
Authors: Wu Yang , Wei Qiangbing , Cai Meirong , Zhou Feng
Published: December 2014

This review outlines the up‐to‐date research progress on controllable interfacial friction on both solid/solid and solid/liquid surfaces. Environment‐sensitive materials at a frictional interface react to certain external stimuli and provoke changes in surface chemistry, interfacial charge, and/or topography, which then cause a change in the coefficient of friction. The external stimuli might be solvent, electrolyte, pH, temperature, light, electric potential, and magnetic field etc. In a similar way, controllable fluid–solid friction (i.e., boundary slippage versus non‐slippage) can also be achieved by reversibly generating a gas lubricating layer at the interface or by changing the fluid–solid adhesion via physicochemical methods. The author comments are presented and outlooks proposed.
Ultrathin MoS2 Nanosheets as Anode Materials for Sodium‐Ion Batteries with Superior Performance
Authors: Su Dawei , Dou Shixue , Wang Guoxiu
Published: December 2014

Few‐layer MoS2 nanosheets are successfully synthesized using a simple and scalable ultrasonic exfoliation technique. The thicknesses of the MoS2 nanosheets ares about 10 nm as measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The unique nanosheet architecture renders the high‐rate transportation of sodium ions due to the short diffusion paths provided by ultrathin thickness and the large interlayer space within the MoS2 crystal structure (d(002) = 6.38 Å). When applied as anode materials in sodium‐ion batteries, MoS2 nanosheets exhibit a high, reversible sodium storage capacity and excellent cyclability. The MoS2 nanosheets also demonstrate good electrochemical performance at high current densities.
Efficient Water Splitting Using a Simple Ni/N/C Paper Electrocatalyst
Authors: Ren Jiawen , Antonietti Markus , Fellinger Tim‐Patrick
Published: December 2014

An efficient water splitting electrocatalyst is presented. Cheap and sustainable cellulose filter paper, infiltrated with nickel acetate as the nickel source, and phenanthroline as a ligand and nitrogen source are carbonized together. Nitrogen functionalities turn out to be crucial coordination sites for the supported Ni/NiO(OH) particles. This simple and scalable one step procedure leads to powders, but also to complete membranes made of ≈10 wt% Ni, supported on nitrogen functionalized carbon. The non‐noble catalyst shows a low onset potential (330 mV vs reversible hydrogen electrode), high current density (e.g., j > 25 mA cm−­2 at η = 430 mV), excellent kinetics (Tafel slope of 44 mV dec−1), and a very favorable stability (<5% decay after 10 h electrolysis) in the oxygen evolution. The performance is similar or even better compared to state‐of‐the‐art noble metal catalysts (e.g., IrO2, Ir/C, Ru/C, and Pt/C). Because of the simple, cheap, and scalable preparation procedure the catalyst is highly promising for practical low price/tech applications. Interestingly, the system is also active in the hydrogen evolution reaction, leading to a promising bifunctional catalyst. The benchmark characteristics are η10 = 390 mV for oxygen evolution and η10 = 190 mV for hydrogen evolution, that is, an overall efficiency of 68% at 10 mA current density.
A Simple Electrochemical Route to Access Amorphous Mixed‐Metal Hydroxides for Supercapacitor Electrode Materials
Authors: Li Hongbo , Gao Yuqian , Wang Chengxin , Yang Guowei
Published: December 2014

Supercapacitors or electrochemical capacitors, as energy storage devices, require very stable positive electrode materials for useful applications. Although most positive electrodes are based on crystalline mixed‐metal hydroxides, their pseudocapacitors usually perform poorly or have a short cycle life. High activities can be achieved with amorphous phases. Methods to produce amorphous materials are also not typically amenable towards mixed‐metal compositions. It is demonstrated that electrochemistry in an ambient environment can be used to produce a series of amorphous mixed‐metal hydroxides with a homogeneous distribution of metals for use as positive electrode materials in a supercapacitor. The integrated performance of the amorphous ternary mixed‐metal hydroxide pseudocapacitor is superior to that of crystalline materials. The amorphous Ni‐Co‐Fe hydroxide supercapacitor is characterized by a long‐term cycling stability that retained 94% of its capacity after 20 000 cycles. This is much higher than the cycle life of crystalline devices. These results show the broad applicability of this methodology towards new electrode materials for high‐performance supercapacitors, especially amorphous mixed‐metal hydroxides, as advanced electrode materials.
Interactions between MAOA and SYP polymorphisms were associated with symptoms of attention—deficit/hyperactivity disorder in Chinese Han subjects
Authors: Gao Qian , Liu Lu , Li Hai‐Mei , Tang Yi‐Lang , Wu Zhao‐Min , Chen Yun , Wang Yu‐Feng , Qian Qiu‐Jin
Published: December 2014

As candidate genes of attention—deficit/hyperactivity disorder (ADHD), monoamine oxidase A (MAOA), and synaptophysin (SYP) are both on the X chromosome, and have been suggested to be associated with the predominantly inattentive subtype (ADHD‐I). The present study is to investigate the potential gene–gene interaction (G × G) between rs5905859 of MAOA and rs5906754 of SYP for ADHD in Chinese Han subjects. For family‐based association study, 177 female trios were included. For case‐control study, 1,462 probands and 807 normal controls were recruited. The ADHD Rating Scale‐IV (ADHD‐RS‐IV) was used to evaluate ADHD symptoms. Pedigree‐based generalized multifactor dimensionality reduction (PGMDR) for female ADHD trios indicated significant gene interaction effect of rs5905859 and rs5906754. Generalized multifactor dimensionality reduction (GMDR) indicated potential gene–gene interplay on ADHD RS‐IV scores in female ADHD‐I. No associations were observed in male subjects in case‐control analysis. In conclusion, our findings suggested that the interaction of MAOA and SYP may be involved in the genetic mechanism of ADHD‐I subtype and predict ADHD symptoms. © 2014 Wiley Periodicals, Inc.
Racemic DNA Crystallography
Authors: Mandal Pradeep K. , Collie Gavin W. , Kauffmann Brice , Huc Ivan
Published: December 2014

Racemates increase the chances of crystallization by allowing molecular contacts to be formed in a greater number of ways. With the advent of protein synthesis, the production of protein racemates and racemic‐protein crystallography are now possible. Curiously, racemic DNA crystallography had not been investigated despite the commercial availability of L‐ and D‐deoxyribo‐oligonucleotides. Here, we report a study into racemic DNA crystallography showing the strong propensity of racemic DNA mixtures to form racemic crystals. We describe racemic crystal structures of various DNA sequences and folded conformations, including duplexes, quadruplexes, and a four‐way junction, showing that the advantages of racemic crystallography should extend to DNA.
Stiffness‐Dependent In Vitro Uptake and Lysosomal Acidification of Colloidal Particles
Authors: Hartmann Raimo , Weidenbach Marcel , Neubauer Martin , Fery Andreas , Parak Wolfgang J.
Published: December 2014

The physico‐chemical properties of colloidal particles determine their uptake into cells. For a series of microparticles only one parameter, the mechanical stiffness, was varied, whereas other parameters such as size, shape, and charge were kept constant. The uptake was monitored in situ by analyzing individual particle trajectories including the progress of endocytosis, derived from local pH measurements around each particle. Evidence is presented that soft particles with low stiffness are transported faster to lysosomes than stiffer ones.
Short, Enantioselective Total Synthesis of Chatancin
Authors: Zhao Yu‐Ming , Maimone Thomas J.
Published: December 2014

An enantioselective total synthesis of the polycyclic diterpene (+)‐chatancin, a potent PAF antagonist, is reported. Proceeding in seven steps from dihydrofarnesal, this synthetic route was designed to circumvent macrocyclization‐based strategies to complex, cyclized cembranoids. The described synthesis requires only six chromatographic purifications, is high yielding, and avoids protecting‐group manipulations. An X‐ray crystal structure of this fragile marine natural product was obtained.
Turn‐On Luminescence Sensing and Real‐Time Detection of Traces of Water in Organic Solvents by a Flexible Metal–Organic Framework
Authors: Douvali Antigoni , Tsipis Athanassios C. , Eliseeva Svetlana V. , Petoud Stéphane , Papaefstathiou Giannis S. , Malliakas Christos D. , Papadas Ioannis , Armatas Gerasimos S. , Margiolaki Irene , Kanatzidis Mercouri G. , Lazarides Theodore , Manos Manolis J.
Published: December 2014

The development of efficient sensors for the determination of the water content in organic solvents is highly desirable for a number of chemical industries. Presented herein is a Mg2+ metal–organic framework (MOF), which exhibits the remarkable capability to rapidly detect traces of water (0.05–5 % v/v) in various organic solvents through an unusual turn‐on luminescence sensing mechanism. The extraordinary sensitivity and fast response of this MOF for water, and its reusability make it one of the most powerful water sensors known.
Polymeric membrane modification using SPEEK and bentonite for ultrafiltration of dairy wastewater
Authors: Pagidi Aruna , Lukka Thuyavan Y. , Arthanareeswaran G. , Ismail A. F. , Jaafar Juhana , Paul Diby
Published: December 2014

The different polymeric membrane materials were fabricated using modifiers such as sulfonated poly(ether ether ketone) (SPEEK) and bentonite for effective ultrafiltration of proteins from dairy effluent. Polyvinylidene fluoride (PVDF), polyethersulfone (PES), polyetherimide (PEI), polyamide‐imides (PAI), cellulose acetate (CA), and polyphenylsulfone (PPSU) were selected for modification. Membrane morphology and functional group analysis were characterized using scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR). Pure water permeability (64.66 × 10−9m/s kPa) was higher for the PES/SPEEK/bentonite membrane when compared with other polymeric membranes. Contact angle (54.05°) value was lower for CA/SPEEK/bentonite membranes and which indicates that hydrophilicity has got enhanced. The membrane performance was tested using model dairy wastewater by ultrafiltration under longer run mode. Further it was evaluated using resistance in series model. This study infers that modification of membranes using charged SPEEK polymer and nanofiller as bentonite can be used to alleviate the fouling in the treatment of dairy wastewater. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41651.
Microwave processing of SiC nanoparticles infused polymer composites: Comparison of thermal and mechanical properties
Authors: Rabby Md. Reza‐E‐ , Jeelani Shaik , Rangari Vijaya K.
Published: December 2014

The goal of this study is to compare thermal and mechanical properties of an epoxy resin system reinforced with SiC nanoparticles using both conventional thermal curing and microwave irradiation techniques. The microwave curing technique has shown potential benefits in processing polymeric nanocomposites by reducing the curing time without compromising the thermo‐mechanical performances of the materials. It was observed from this investigation that, the curing time was drastically reduced to ∼30 min for microwave curing instead of 12 h room temperature curing with additional 6 h post curing at 75°C. Ductile behavior was more pronounced for microwave curing technique while thermal curing showed brittle like behavior as revealed from flexural test. The maximum strain to failure was increased by 25–40% for microwave‐cured nanocomposites over the room temperature cured nanocomposites for the same loading of nanofillers. The glass transition temperature (Tg) also increased by ∼14°C while curing under microwave irradiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41708.
Recent advances in nanocellulose for biomedical applications
Authors: Jorfi Mehdi , Foster E. Johan
Published: December 2014

Nanocellulose materials have undergone rapid development in recent years as promising biomedical materials because of their excellent physical and biological properties, in particular their biocompatibility, biodegradability, and low cytotoxicity. Recently, a significant amount of research has been directed toward the fabrication of advanced cellulose nanofibers with different morphologies and functional properties. These nanocellulose fibers are widely applied in medical implants, tissue engineering, drug delivery, wound‐healing, cardiovascular applications, and other medical applications. In this review, we reflect on recent advancements in the design and fabrication of advanced nanocellulose‐based biomaterials (cellulose nanocrystals, bacterial nanocellulose, and cellulose nanofibrils) that are promising for biomedical applications and discuss material requirements for each application, along with the challenges that the materials might face. Finally, we give an overview on future directions of nanocellulose‐based materials in the biomedical field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41719.
Structure‐property relationships in copolyester elastomer‐layered silicate nanocomposites
Authors: Alosime Eid M. , Edwards Grant A. , Martin Darren J.
Published: December 2014

While the field of polymer–clay nanocomposites is reaching maturity, some parts of the studied systems still present researchers with possibilities for the improvement of material properties. This study entails the understanding of the relationships in copolyester elastomer/organically modified layered silicate nanocomposite and the structure–property relationships within the system of the nanocomposite. A series of these nanocomposites was prepared via twin‐screw extrusion melt compounding. The experiments included the following three types of synthetic organosilicates: high aspect ratio Somasif (ME100) fluoromica and two lower aspect ratio Laponite synthetic hectorites, (WXFN) and (WXFP). These organosilicates were modified with quaternary octadecyltrimethylammonium bromide (ODTMA) and were used to prepare the nanocomposites. The nanocomposite structure on a micro‐ and nanometre scales was evaluated by two techniques, such as X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties of the nanocomposites were examined to determine the impact aspect ratio of the nanofiller and wt % loading have on performance. The addition of the 2 wt % high aspect ratio of ME100‐ODTMA, in particular, showed statistically improved tensile strength, tear resistance, creep resistance, and water vapor permeation barrier enhancement. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41742.