bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of sea surface temperature by chlorophyll concentration in the Atlantic upwelling systems
Authors: Hernandez O. , Jouanno J. , Echevin V. , Aumont O. 
Published: May 2017

AbstractThe influence of the chlorophyll on the upper Tropical Atlantic Ocean is investigated with long‐term (1979–2012) regional oceanic simulations with 1/4° horizontal resolution based on the NEMO3.6 model. The model solar radiation penetration scheme depends on the chlorophyll concentration. Simulations with time and spatially varying concentrations obtained from satellite ocean color observations are compared with a simulation forced with constant chlorophyll concentration of 0.05 mg m−3, representative of chlorophyll depleted waters. Results indicate that regions of the Tropical Atlantic with chlorophyll concentrations larger than in the reference simulation (i.e., [chl] > 0.05 mg m−3) get warmer at the surface, with the exception of the main upwelling regions where high chlorophyll concentrations are associated with a significant cooling of the sea surface (∼1°C in the Benguela upwelling). The analysis of the model heat balance shows that the biological differential heating causes negative temperature anomalies in subsurface source waters prior to their upwelling at the coast. The shallow mixed‐layer in the eastern equatorial and tropical Atlantic favors the persistence of these subsurface anomalies and may explain why the Benguela is particularly sensitive to the biological differential heating. In spite of the presence of high chlorophyll concentrations in the upwelling regions, both the larger amount of shortwave radiation captured in the surface layers and the modifications of the horizontal and vertical advection at the coast are found to play a secondary role in the SST change in the upwelling region.
The role of turbulence in thunderstorm, snowstorm, and dust storm electrification
Authors: Mareev Evgeny A. , Dementyeva Svetlana O. 
Published: May 2017

AbstractIn this paper the contribution of turbulence into the electrification of thunderstorms, snowstorms, and dust storms is investigated for the first time. A model of large‐scale electric field generation in a weakly conducting medium, containing two types of particles charging by collisions, is used. Thunderstorm and snowstorm electrification are considered in detail in this paper; dust storm electrification is also considered, despite being substantially different from the two other cases, to demonstrate the universality of the proposed method. A comparison of the results with the experimental data for thunderstorms, blizzards, and dust storms is carried out. It is found that the situation is notably different for inductive and noninductive charge separations. For inductive charge separation there is a range of thunderstorm and snowstorm parameters (conductivity and the particle radii being the most important factors) for which the electric field grows exponentially with time. This effect can make the inductive mechanism dominant near the breakdown field in turbulent zones of thunderclouds. For noninductive (or triboelectric) charge separation caused by intense velocity fluctuations, the electric field strength grows only linearly with time. The most substantial effect of turbulence on noninductive charging is expected to occur in snowstorms and dust storms, whereas noninductive turbulent charging has a little impact on the thunderstorm electrification.
A cloud‐resolving model study of aerosol‐cloud correlation in a pristine maritime environment
Authors: Nishant Nidhi , Sherwood Steven C. 
Published: May 2017

AbstractIn convective clouds, satellite‐observed deepening or increased amount of clouds with increasing aerosol concentration has been reported and is sometimes interpreted as aerosol‐induced invigoration of the clouds. However, such correlations can be affected by meteorological factors that affect both aerosol and clouds, as well as observational issues. In this study, we examine the behavior in a 660 × 660 km2 region of the South Pacific during June 2007, previously found by Koren et al. (2014) to show strong correlation between cloud fraction, cloud top pressure, and aerosols, using a cloud‐resolving model with meteorological boundary conditions specified from a reanalysis. The model assumes constant aerosol loading, yet reproduces vigorous clouds at times of high real‐world aerosol concentrations. Days with high‐ and low‐aerosol loading exhibit deep‐convective and shallow clouds, respectively, in both observations and the simulation. Synoptic analysis shows that vigorous clouds occur at times of strong surface troughs, which are associated with high winds and advection of boundary layer air from the Southern Ocean where sea‐salt aerosol is abundant, thus accounting for the high correlation. Our model results show that aerosol‐cloud relationships can be explained by coexisting but independent wind‐aerosol and wind‐cloud relationships and that no cloud condensation nuclei effect is required.
Isostatic equilibrium in spherical coordinates and implications for crustal thickness on the Moon, Mars, Enceladus, and elsewhere
Authors: Hemingway Douglas J. , Matsuyama Isamu 
Published: May 2017

AbstractIsostatic equilibrium is commonly defined as the state achieved when there are no lateral gradients in hydrostatic pressure, and thus no lateral flow, at depth within the lower viscosity mantle that underlies a planetary body's outer crust. In a constant‐gravity Cartesian framework, this definition is equivalent to the requirement that columns of equal width contain equal masses. Here we show, however, that this equivalence breaks down when the spherical geometry of the problem is taken into account. Imposing the “equal masses” requirement in a spherical geometry, as is commonly done in the literature, leads to significant lateral pressure gradients along internal equipotential surfaces and thus corresponds to a state of disequilibrium. Compared with the “equal pressures” model we present here, the equal masses model always overestimates the compensation depth—by ∼27% in the case of the lunar highlands and by nearly a factor of 2 in the case of Enceladus.
Scale‐free distribution of Dead Sea sinkholes: Observations and modeling
Authors: Yizhaq H. , Ish‐Shalom C. , Raz E. , Ashkenazy Y. 
Published: May 2017

AbstractThere are currently more than 5500 sinkholes along the Dead Sea in Israel. These were formed due to the dissolution of subsurface salt layers as a result of the replacement of hypersaline groundwater by fresh brackish groundwater. This process has been associated with a sharp decline in the Dead Sea water level, currently more than 1 m/yr, resulting in a lower water table that has allowed the intrusion of fresher brackish water. We studied the distribution of the sinkhole sizes and found that it is scale free with a power law exponent close to 2. We constructed a stochastic cellular automata model to understand the observed scale‐free behavior and the growth of the sinkhole area in time. The model consists of a lower salt layer and an upper soil layer in which cavities that develop in the lower layer lead to collapses in the upper layer. The model reproduces the observed power law distribution without involving the threshold behavior commonly associated with criticality.
Internal variability in a coupled general circulation model in radiative‐convective equilibrium
Authors: Coppin David , Bony Sandrine 
Published: May 2017

AbstractNumerical models run in non‐rotating radiative‐convective equilibrium (RCE) using prescribed sea surface temperatures (SSTs) show that convection can spontaneously aggregate into dry and moist areas, and that convective aggregation tends to increase with temperature. Using a general circulation model coupled to an ocean mixed layer, we show that in RCE the coupled ocean‐atmosphere system exhibits some internal variability. This variability arises from the interplay between mean surface temperature, SST gradients and convective aggregation, and its timescale is proportional to the depth of the ocean mixed layer. For an ocean layer deeper than 10 m, the variability occurs at the interannual timescale, and variations of convective aggregation are almost out of phase with those of surface temperature. The coupled RCE framework might be relevant to understand some internal modes of variability of the tropical ocean‐atmosphere system such as El Niño Southern Oscillation.
Electron‐acoustic solitons and double layers in the inner magnetosphere
Authors: Vasko I. Y. , Agapitov O. V. , Mozer F. S. , Bonnell J. W. , Artemyev A. V. , Krasnoselskikh V. V. , Reeves G. , Hospodarsky G. 
Published: May 2017

AbstractThe Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with energy above 200 eV provide the dominant contribution to the total electron density, while the density of cold electrons (below a few eV) is less than a few tenths of the total electron density. We show that velocities of the asymmetric ESW are close to velocity of electron‐acoustic waves (existing due to the presence of cold and hot electrons) and follow the Korteweg‐de Vries (KdV) dispersion relation derived for the observed plasma conditions (electron energy spectrum is a power law between about 100 eV and 10 keV and Maxwellian above 10 keV). The ESW spatial scales are in general agreement with the KdV theory. We interpret the asymmetric ESW in terms of electron‐acoustic solitons and double layers (shocks waves).
Small‐scale longitudinal variations in the daytime equatorial thermospheric wave dynamics as inferred from oxygen dayglow emissions
Authors: Karan Deepak K. , Pallamraju Duggirala 
Published: May 2017

AbstractThe equatorial upper atmospheric dynamic processes show both latitudinal and longitudinal variabilities. While the variability in latitudes can exist over small distances (approximately hundreds of kilometers), the longitudinal behavior has been shown to be existing mainly over large spatial separations (approximately thousands of kilometers). In the present work we have used variations in thermospheric optical dayglow emissions at OI 557.7, 630.0, and 777.4 nm, as tracers of neutral dynamics. These emissions are obtained simultaneously from a high‐resolution slit spectrograph, Multi wavelength Imaging Spectrograph using Echelle grating, from a low‐latitude location, Hyderabad (17.5°N, 78.4°E; 8.9°N magnetic latitude) in India, to investigate the longitudinal differences in the upper atmospheric processes over short separations. Spectral analyses of gravity waves carried out on the dayglow emission intensity variations for different independent viewing directions on some days show dissimilar periodicities suggesting the existence of longitudinal differences. Gravity wave scale sizes and the propagation characteristics on these days are different from those in which longitudinal differences are not seen. Further, the zenith diurnal emission intensity patterns are different on the days with and without the observed longitudinal variability. This work shows for the first time that longitudinal differences in upper atmospheric processes can exist at even as small as 3° longitude separations. Such longitudinal differences seen in the neutral dayglow emission intensities are attributed to the zonal variation in the daytime equatorial electrodynamics.
Ion Bernstein instability as a possible source for oxygen ion cyclotron harmonic waves
Authors: Min Kyungguk , Denton Richard E. , Liu Kaijun , Gary S. Peter , Spence Harlan E. 
Published: May 2017

AbstractThis paper demonstrates that an ion Bernstein instability can be a possible source for recently reported electromagnetic waves with frequencies at or near the singly ionized oxygen ion cyclotron frequency,
, and its harmonics. The particle measurements during strong wave activity revealed a relatively high concentration of oxygen ions (∼15%) whose phase space density exhibits a local peak at energy ∼20 keV. Given that the electron plasma‐to‐cyclotron frequency ratio is
, this energy corresponds to the particle speed
, where vA is the oxygen Alfvén speed. Using the observational key plasma parameters, a simplified ion velocity distribution is constructed, where the local peak in the oxygen ion velocity distribution is represented by an isotropic shell distribution. Kinetic linear dispersion theory then predicts unstable Bernstein modes at or near the harmonics of
and at propagation quasi‐perpendicular to the background magnetic field, B0. If the cold ions are mostly protons, these unstable modes are characterized by a low compressibility (
), a small phase speed (vph∼0.2vA), a relatively small ratio of the electric field energy to the magnetic field energy (between 10−4 and 10−3), and the Poynting vector directed almost parallel to B0. These linear properties are overall in good agreement with the properties of the observed waves. We demonstrate that superposition of the predicted unstable Bernstein modes at quasi‐perpendicular propagation can produce the observed polarization properties, including the minimum variance direction on average almost parallel to B0.
Enzymatic Modification of Plant Cell Wall Polysaccharides
Authors: Øbro Jens , Hayashi Takahisa , Mikkelsen Jørn Dalgaard 
Published: May 2017

AbstractPlant cell walls are intricate structures with remarkable properties, widely used in almost every aspect of our life. Cell walls consist largely of complex polysaccharides and there is often a need for chemical and biochemical processing before industrial use. There is an increasing demand for sustainable processes that replace chemical treatments with white biotechnology. Plants can contribute significantly to this sustainable process by producing plant or microbial enzymesin plantathat are necessary for plant cell wall modification or total degradation. This will give rise to superior food fibres, hydrocolloids, paper, textile, animal feeds or biofuels. Classical microbial‐based fermentation systems could in the future face serious competition from plant‐based expression systems for enzyme production. Plant expressed enzymes can either be targeted to specific cellular compartments for accumulation and storage, or targeted to the cell wall for immediate modification of the polysaccharides. Furthermore, thermoactivated enzymes can successfully be employed to avoid undue degradation of the cell wall and detrimental phenotypes resulting from this. A further use of enzyme expressionin plantais the possibility of elucidating the biological role of specific polymers, such as the involvement of xyloglucan in tree bending, or to decrease the level of pectin in flax to simplify the retting step in the textile refinery process.
100 Years of Ethylene – A Personal View
Authors: Grierson Don 
Published: May 2017

AbstractDuring the last 100 years, our view of ethylene has progressed from it being an environmental factor with profound effects on plants to an endogenous plant hormone controlling growth, development and reproduction. The ethylene story began with the work of Neljubov, a Russian graduate student. Previous work had indicated the adverse effect of illuminating gas on trees, but Neljubov (1901) was the first to describe the triple growth response of etiolated pea seedlings: (1) reduced stature, (2) exaggerated hypocotyl hook and (3) inhibited root growth (see Figure 1), which was subsequently shown to be due to hydrocarbons such as ethylene in the illuminating gas. When the method of heating banana‐ripening rooms was switched from coke ovens to electric arc furnaces, it was noted that the fruit did not ripen so effectively, and it was eventually realized that the production of ethylene and other hydrocarbons during the combustion of coke actually stimulated ripening of the fruit. Later, it was found that hydrocarbons emanating from the lacquer coating the ballast chokes of lighting equipment, when in use, could affect the growth of plants in controlled environment rooms (Wills & Patterson, 1970).
Perception of Ethylene by Plants – Ethylene Receptors
Authors: Binder Brad M. , Chang Caren , Schaller G. Eric 
Published: May 2017

AbstractThe first step in the perception of ethylene occurs when ethylene binds to its receptors. Over the past few decades, since the cloning of the first ethylene receptor ETR1 fromArabidopsisin 1993, a large number of studies have steadily improved our understanding about how the receptors function in the ethylene‐signalling pathway. After providing a historical overview of ethylene receptor research, what is known about several aspects of the receptors is summarized including our understanding about the evolution of the receptors from cyanobacteria into plants. Much of our knowledge about ethylene receptors comes from mutational and biochemical studies. These studies have led to a model where a copper co‐factor is delivered to the receptors by the RAN1 copper transporter. This model predicts that when ethylene binds to this copper ion in the receptor, the receptor passes through a transition state to a non‐signalling conformation. The exact nature of the output from the receptors is unknown, but current models predict that ethylene binding to the receptors deactivates the kinase activity of CONSTITUTIVE TRIPLE RESPONSE 1 (CTR1). It is now clear from published studies in several species that the receptors are not entirely overlapping in function. Several new papers are highlighted showing that the control of a particular phenotype can be under the control of a subset of receptor isoforms or even just a single receptor isoform. These differing roles are, in part, likely to be caused by differential regulation of each receptor isoform. Recent research has uncovered a number of post‐translational mechanisms that can regulate the receptors including receptor clustering, differential proteolysis of specific receptor isoforms, and regulatory proteins that specifically regulate certain receptor isoforms. Finally, models for receptor function and ethylene signal transduction are provided to explain the ability of plants to respond to a wide concentration range of ethylene as well as to re‐sensitize and recover after ethylene levels drop.
Ethylene Signalling: TheCTR1 Protein Kinase
Authors: Zhong Silin , Chang Caren 
Published: May 2017

AbstractCONSTITUTIVE TRIPLE RESPONSE(CTR1) is an important negative regulator of ethylene signalling that was first identified by the isolation of a constitutive ethylene‐response mutant inArabidopsis. In the absence of ethylene treatment,ctr1mutants exhibit the same phenotypes as ethylene‐treated wild‐type plants.Arabidopsishas only oneCTR1gene in ethylene signalling, whereas in tomato (Solanum lycopersicon), threeCTR1homologues are involved in ethylene signalling and display differential gene expression patterns that might reflect specific functions.CTR1encodes a Raf‐like serine/threonine (Ser/Thr) protein kinase with anN‐terminal regulatory domain and aC‐terminal kinase domain. CTR1 acts downstream of the ethylene receptors and upstream of EIN2. When the receptors perceive ethylene, CTR1 kinase activity is shut off, thereby leading to responses. CTR1 has been shown to physically associate with the ethylene receptors at the endoplasmic reticulum membrane, but the biochemical mechanisms of CTR1 regulation remain unclear at this point. The downstream substrate(s) of CTR1 are unknown as well. CTR1 has the highest sequence similarity to Raf protein kinases, so it has been long assumed that CTR1 functions in a mitogen‐activated protein kinase (MAPK) cascade. The existence of a MAPK cascade in ethylene signalling has been controversial however, and functional similarities between CTR1 and MAP kinase kinase kinase (MAPKKKs) remain speculative. Thus, the remaining critical questions surrounding CTR1 are the regulation of CTR1 and how the signal is transduced from CTR1 to downstream components. The study of non‐ethylene‐response phenotypes inctr1mutants has been useful for revealing interactions between ethylene signalling and other plant signals, including gibberellin, auxin and abscisic acid.
EIN2 andEIN3 in Ethylene Signalling
Authors: Cho Young‐Hee , Lee Sangho , Yoo Sang‐Dong 
Published: May 2017

AbstractEthylene was the first plant hormone for which a receptor‐dependent signalling pathway was established. The signal transduction pathway is framed around genetically identified factors encompassing membrane receptors through to intra‐cellular regulators and then nuclear transcription factors. Recently, the cellular and biochemical connections among these genetic factors have been characterized to reveal a complex and intertwined signalling scheme. For ethylene signalling, the short‐lived ETHYLENE INSENSITIVE2 (EIN2) and ETHYLENE INSENSITIVE3 (EIN3) proteins play central roles, and so regulation of the turnover of these proteins by specific E3 ligases serves as a key regulatory step in the pathway. Two antagonistic mitogen‐activated protein kinase (MAPK) cascades that modify EIN3 appear to mediate intra‐cellular signalling from membrane receptors to nuclear transcription factors. The identification of further genomic and genetic components and elucidation of their cellular and biochemical roles in EIN2 and EIN3 regulation are thus required to complete the whole ethylene signal transduction pathway. Such a comprehensive understanding of ethylene signal transduction will provide useful information for the selection of genes that can enhance plant adaptations to unfavourable environmental conditions and so secure food production and plant‐based renewable bio‐energy for human society.
Ethylene and Cell Separation Processes
Authors: Gonzalez‐Carranza Zinnia H. , Roberts Jeremy A. 
Published: May 2017

AbstractCell separation is a critical process for the successful growth and development of a plant. It contributes to the earliest phase of the life cycle to enable germination to take place and is a prerequisite for the softening of fleshy fruits to enable the next generation to be dispersed as seeds. In this chapter, we consider the evidence that ethylene plays a role in coordinating events associated with cell separation and the mechanisms that may be involved. Cell wall remodelling is primarily driven by the action of a cocktail of hydrolytic enzymes whose expression is spatially and temporally regulated. For phenomena such as organ abscission, ripening of climacteric fruit and aerenchyma development, there is convincing evidence that ethylene plays a regulatory role, but for cell separation at other sites this is not clear. Many of the recent breakthroughs in our understanding in this area have originated from work on the model plantArabidopsisand the challenge is to translate these discoveries into crop species to optimize resource efficiency and make production more sustainable.
Gymnosperms
Authors: Stevenson Dennis Wm. 
Published: May 2017

AbstractThis chapter focuses on the oddities of gymnosperm anatomy, morphology, and life cycles. Of particular interest are those seemingly intractable aspects that now seem tractable by combining recent developments in plant molecular biology with plant anatomy, morphology, and development. In most examples, there is available data from plant morphology in the widest sense that can provide the framework for experimental and molecular approaches. These include, but are not limited to, leaf development, senescence, stem growth in diameter, phylloclade development, the structure of reproductive axes and their reciprocal transitions to vegetative growth, free nuclear gametophytes and embryos, and unique features associated with seeds.