bluuebunny/crossref_metadata_2025_split huggingface dataset:
First detection of fluorine on Mars: Implications for Gale Crater's geochemistry
Authors: Forni Olivier , Gaft Michael , Toplis Michael J. , Clegg Samuel M. , Maurice Sylvestre , Wiens Roger C. , Mangold Nicolas , Gasnault Olivier , Sautter Violaine , Le Mouélic Stéphane , Meslin Pierre‐Yves , Nachon Marion , McInroy Rhonda E. , Ollila Ann M. , Cousin Agnès , Bridges John C. , Lanza Nina L. , Dyar Melinda D. 
Published: January 2015

AbstractVolatiles and especially halogens (F and Cl) have been recognized as important species in the genesis and melting of planetary magmas. Data from the Chemical Camera instrument on board the Mars Science Laboratory rover Curiosity now provide the first in situ analyses of fluorine at the surface of Mars. Two principal F‐bearing mineral assemblages are identified. The first is associated with high aluminum and low calcium contents, in which the F‐bearing phase is an aluminosilicate. It is found in conglomerates and may indicate petrologically evolved sources. This is the first time that such a petrologic environment is found on Mars. The second is represented by samples that have high calcium contents, in which the main F‐bearing minerals are likely to be fluorapatites and/or fluorites. Fluorapatites are found in some sandstone and may be detrital, while fluorites are also found in the conglomerates, possibly indicating low‐T alteration processes.
Activation of very low frequency earthquakes by slow slip events in the Ryukyu Trench
Authors: Nakamura Mamoru , Sunagawa Naoya 
Published: January 2015

AbstractLong‐term activity of shallow very low frequency earthquakes (VLFEs) in the Ryukyu Trench, unassociated with recent large thrust earthquakes, was analyzed using a broadband seismometer network. The distribution of shallow VLFEs was divided into three large clusters. The activity of the VLFEs is modulated by repetitive slow slip events, and the activity of these VLFEs increases to 2–3 times its ordinary rate at 10–20 days after the onset of the slow slip events. The activation of VLFEs could be generated by small increases on the order of approximately 0.1–0.5 kPa in Coulomb failure stress, suggesting that stress in the plate interface where the VLFEs occur is frequently released in small amounts. Moreover, the distribution of VLFEs is complementary to the historical tsunami source area and locked area. The distribution of the VLFEs indicates heterogeneity in interplate coupling along the trench.
Distinguishing between pulsed and continuous reconnection at the dayside magnetopause
Authors: Trattner K. J. , Onsager T. G. , Petrinec S. M. , Fuselier S. A. 
Published: January 2015

AbstractMagnetic reconnection has been established as the dominant mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy and momentum to flow into the magnetosphere. One of the persistent problems of magnetic reconnection is the question of whether the process is continuous or intermittent and what input condition(s) might favor one type of reconnection over the other. Observations from imagers that record FUV emissions caused by precipitating cusp ions demonstrate the global nature of magnetic reconnection. Those images show continuous ionospheric emissions even during changing interplanetary magnetic field conditions. On the other hand, in situ observations from polar‐orbiting satellites show distinctive cusp structures in flux distributions of precipitating ions, which are interpreted as the telltale signature of intermittent reconnection. This study uses a modification of the low‐velocity cutoff method, which was previously successfully used to determine the location of the reconnection site, to calculate for the cusp ion distributions the “time since reconnection occurred.” The “time since reconnection” is used to determine the “reconnection time” for the cusp magnetic field lines where these distributions have been observed. The profile of the reconnection time, either continuous or stepped, is a direct measurement of the nature of magnetic reconnection at the reconnection site. This paper will discuss a continuous and pulsed reconnection event from the Polar spacecraft to illustrate the methodology.
Medieval pulse of great earthquakes in the central Himalaya: Viewing past activities on the frontal thrust
Authors: Rajendran C. P. , John Biju , Rajendran Kusala 
Published: January 2015

AbstractThe Himalaya has experienced three great earthquakes during the last century—1934 Nepal‐Bihar, 1950 Upper Assam, and arguably the 1905 Kangra. Focus here is on the central Himalayan segment between the 1905 and the 1934 ruptures, where previous studies have identified a great earthquake between thirteenth and sixteenth centuries. Historical data suggest damaging earthquakes in A.D. 1255, 1344, 1505, 1803, and 1833, although their sources and magnitudes remain debated. We present new evidence for a great earthquake from a trench across the base of a 13 m high scarp near Ramnagar at the Himalayan Frontal Thrust. The section exposed four south verging fault strands and a backthrust offsetting a broad spectrum of lithounits, including colluvial deposits. Age data suggest that the last great earthquake in the central Himalaya most likely occurred between A.D. 1259 and 1433. While evidence for this rupture is unmistakable, the stratigraphic clues imply an earlier event, which can most tentatively be placed between A.D. 1050 and 1250. The postulated existence of this earlier event, however, requires further validation. If the two‐earthquake scenario is realistic, then the successive ruptures may have occurred in close intervals and were sourced on adjacent segments that overlapped at the trench site. Rupture(s) identified in the trench closely correlate with two damaging earthquakes of 1255 and 1344 reported from Nepal. The present study suggests that the frontal thrust in central Himalaya may have remained seismically inactive during the last ~700 years. Considering this long elapsed time, a great earthquake may be due in the region.
Magnetic anisotropy in clinopyroxene and orthopyroxene single crystals
Authors: Biedermann Andrea R. , Pettke Thomas , Bender Koch Christian , Hirt Ann M. 
Published: January 2015

AbstractPyroxenes constitute an important component in mafic igneous and metamorphic rocks. They often possess a prismatic habit, and their long axis, the crystallographic c axis, helps define a lineation in a textured rock. Anisotropy of magnetic susceptibility (AMS) serves as a fabric indicator in igneous and metamorphic rocks. If a rock's AMS is carried by pyroxenes, it can be related to their crystallographic preferred orientation and degree of alignment. This requires knowing the intrinsic AMS of pyroxene single crystals. This study provides a comprehensive low‐field and high‐field AMS investigation of chemically diverse orthopyroxene and clinopyroxene crystals in relation to crystal structure, chemical composition, oxidation state of Fe, and the possible presence of ferromagnetic inclusions. The paramagnetic anisotropy, extracted from high‐field data, shows clear relationships to crystallographic directions and Fe concentration both in clinopyroxene and orthopyroxene. In the diopside‐augite series, the intermediate susceptibility is parallel to b, and the maximum is at 45° to the c axis. In aegirine, the intermediate axis remains parallel to b, while the maximum susceptibility is parallel to c. The AMS of spodumene depends on Fe concentration. In enstatite, the maximum susceptibility aligns with c and the minimum with b, and in the case of hypersthene, the maximum susceptibility is normal to the exsolution lamellae. Magnetite inclusions within augite possess a ferromagnetic anisotropy with consistent orientation of the principal susceptibilities, which dominates the low‐field anisotropy. These results provide better understanding of magnetic anisotropy in pyroxenes and form a solid basis for interpretation of magnetic fabrics in pyroxene‐bearing rocks.
Evolving efficiency of restraining bends within wet kaolin analog experiments
Authors: Hatem Alexandra E. , Cooke Michele L. , Madden Elizabeth H. 
Published: January 2015

AbstractRestraining bends along strike‐slip fault systems evolve by both propagation of new faults and abandonment of fault segments. Scaled analog modeling using wet kaolin allows for qualitative and quantitative observations of this evolution. To explore how bend geometry affects evolution, we model bends with a variety of initial angles, θ, from θ = 0° for a straight fault to θ = 30°. High‐angle restraining bends (θ ≥ 20°) overcome initial inefficiencies by abandoning unfavorably oriented restraining segments and propagating multiple new, inwardly dipping, oblique‐slip faults that are well oriented to accommodate convergence within the bend. Restraining bends with 0° < θ ≤ 15° maintain activity along the restraining bend segment and grow a single new oblique slip fault on one side of the bend. In all restraining bends, the first new fault propagates at ~5 mm of accumulated convergence. Particle Image Velocimetry analysis provides a complete velocity field throughout the experiments. From these data, we quantify the strike‐slip efficiency of the system as the percentage of applied plate‐parallel velocity accommodated as slip in the direction of plate motion along faults within the restraining bend. Bends with small θ initially have higher strike‐slip efficiency compared to bends with large θ. Although they have different fault geometries, all systems with a 5 cm bend width reach a steady strike‐slip efficiency of 80% after 50 mm of applied plate displacement. These experimental restraining bends resemble crustal faults in their asymmetric fault growth, asymmetric topographic gradient, and strike‐slip efficiency.
Spatial variances of wind fields and their relation to second‐order structure functions and spectra
Authors: Vogelzang Jur , King Gregory P. , Stoffelen Ad 
Published: January 2015

AbstractKinetic energy variance as a function of spatial scale for wind fields is commonly estimated either using second‐order structure functions (in the spatial domain) or by spectral analysis (in the frequency domain). Both techniques give an order‐of‐magnitude estimate. More accurate estimates are given by a statistic called spatial variance. Spatial variances have a clear interpretation and are tolerant for missing data. They can be related to second‐order structure functions, both for discrete and continuous data. Spatial variances can also be Fourier transformed to yield a relation with spectra. The flexibility of spatial variances is used to study various sampling strategies, and to compare them with second‐order structure functions and spectral variances. It is shown that the spectral sampling strategy is not seriously biased to calm conditions for scatterometer ocean surface vector winds. When the second‐order structure function behaves like
, its ratio with the spatial variance equals
. Ocean surface winds in the tropics have
between 2/3 and 1, so one‐sixth to one‐fifth of the second‐order structure function value is a good proxy for the cumulative variance.
Mechanisms of surface wave energy dissipation over a high‐concentration sediment suspension
Authors: Traykovski Peter , Trowbridge John , Kineke Gail 
Published: January 2015

AbstractField observations from the spring of 2008 on the Louisiana shelf were used to elucidate the mechanisms of wave energy dissipation over a muddy seafloor. After a period of high discharge from the Atchafalaya River, acoustic measurements showed the presence of 20 cm thick mobile fluid‐mud layers during and after wave events. While total wave energy dissipation (D) was greatest during the high energy periods, these periods had relatively low normalized attenuation rates (κ = Dissipation/Energy Flux). During declining wave‐energy conditions, as the fluid‐mud layer settled, the attenuation process became more efficient with high κ and low D. The transition from high D and low κ to high κ and low D was caused by a transition from turbulent to laminar flow in the fluid‐mud layer as measured by a Pulse‐coherent Doppler profiler. Measurements of the oscillatory boundary layer velocity profile in the fluid‐mud layer during laminar flow reveal a very thick wave boundary layer with curvature filling the entire fluid‐mud layer, suggesting a kinematic viscosity 2–3 orders of magnitude greater than that of clear water. This high viscosity is also consistent with a high wave‐attenuation rates measured by across‐shelf energy flux differences. The transition to turbulence was forced by instabilities on the lutocline, with wavelengths consistent with the dispersion relation for this two‐layer system. The measurements also provide new insight into the dynamics of wave‐supported turbidity flows during the transition from a laminar to turbulent fluid‐mud layer.
Interannual Caribbean salinity in satellite data and model simulations
Authors: Grodsky Semyon A. , Johnson Benjamin K. , Carton James A. , Bryan Frank O. 
Published: January 2015

AbstractAquarius sea surface salinity (SSS) reveals the presence of interannual variations in the Caribbean with about 0.5 psu change between salty and fresh events, which propagate westward across that basin at an average speed of 11 cm/s and are preceded by corresponding SSS anomalies east of the Lesser Antilles. These upstream SSS anomalies are produced by interannual changes in the Amazon plume. Their presence is verified using in situ measurements from the northwest tropical Atlantic station. In contrast to SSS, which displays westward propagation, SST changes almost immediately across the Caribbean, suggesting large‐scale atmospheric processes have a primary role in regulating interannual SST in contrast to SSS. A global 1/10° mesoscale ocean model is used to quantify possible origination mechanisms of the Caribbean salinity anomalies and their fate. Simulations confirm that they are produced by anomalous horizontal salt advection, which conveys these salinity anomalies from an area east of the Lesser Antilles across the Caribbean. Anomalous horizontal advection is dominated by mean currents acting on anomalous salinity. The model suggests that interannual Caribbean salinity anomalies eventually enter the Florida Current and reach the Gulf Stream 6–12 months after crossing the central Caribbean. Previous studies link the origin of salinity anomalies in the Amazon plume to variations in the annual freshwater discharge from the continent. In this model interannual discharge variations are absent while simulated SSS variability is in line with observations. This suggests that interannually forced ocean dynamics plays a key role in river plume variability and its spatial dispersion.
Comparing and contrasting extreme stratospheric events, including their coupling to the tropospheric circulation
Authors: Dunn‐Sigouin Etienne , Shaw Tiffany A. 
Published: January 2015

AbstractRecent work has emphasized the importance of stratosphere‐troposphere coupling associated with extreme values of the polar vortex strength and stratospheric planetary wave heat flux during Northern Hemisphere winter. Here using ERA‐Interim reanalysis data the evolution of the two types of events are compared. The life cycle of total (anomaly plus climatology) positive/negative heat flux events are associated with vertically deep high‐latitude planetary wave structures and exhibit largely equal but opposite‐signed impacts, including a net deceleration/acceleration of the polar vortex due to EP flux convergence/divergence and an equatorward/poleward tropospheric jet shift in the North Atlantic. The tropospheric wave pattern is westward propagating. High‐latitude stratospheric vertical zonal wind shear plays a key role during both events. A comparison of the stratospheric events reveals that planetary wave events contribute to the development of vortex events. In particular, total negative heat flux events precede strong vortex events showing that strong vortex events represent true dynamical events involving significant wave‐mean flow interaction. Coupling with the North Atlantic jet occurs preceding vortex events when wave‐1 dominates the total eddy heat flux in the lower stratosphere since interference with wave‐2 makes the impacts less clear. The tropospheric impacts in the North Atlantic associated with planetary wave events are found to be comparable if not larger than those following vortex events.
Hydrological extremes in hyperarid regions: A diagnostic characterization of intense precipitation over the Central Arabian Peninsula
Authors: Kumar Kondapalli Niranjan , Entekhabi Dara , Molini Annalisa 
Published: January 2015

AbstractAridity is typically associated with deep and dry daytime boundary layers, stable nighttime stratification, divergent flows, and limited large‐scale moisture advection. All these factors are paramount in regulating the hydroclimatology of hyperarid regions, resulting in extremely intermittent—and often intense—local precipitation patterns. However, the link between synoptic‐scale forcing and intense precipitation over arid regions has been scarcely investigated in the literature and still remains exceedingly unexplored. We present here a diagnostic study of intense precipitation in the Central Arabian Peninsula, based on the analysis of local extreme signatures embedded in synoptic patterns. Special emphasis is given to the genesis of winter extremes over the Peninsula, and to possible effects of synchronization between the atmospheric circulation over the Mediterranean and the Indian Ocean. Based on composites of the tropospheric circulation for a large ensemble of intense events, we show that moisture necessary to trigger winter extremes over the Peninsula starts to build up in average 8 days before heavy rainfall occurrence, mainly as a consequence of the interplay between the Mediterranean and the Monsoonal circulation. Moisture advection is in turn associated with an upper troposphere cyclonic circulation and pronounced potential vorticity intrusions. Overall, our results demonstrate how large‐scale precursors can be effectively used to improve the predictability of rainfall extremes in hyperarid regions.
The sensitivity of wet and dry tropical forests to climate change in Bolivia
Authors: Seiler C. , Hutjes R. W. A. , Kruijt B. , Hickler T. 
Published: January 2015

AbstractBolivia's forests contribute to the global carbon and water cycle, as well as to global biodiversity. The survival of these forests may be at risk due to climate change. To explore the associated mechanisms and uncertainties, a regionally adapted dynamic vegetation model was implemented for the Bolivian case, and forced with two contrasting climate change projections. Changes in carbon stocks and fluxes were evaluated, factoring out the individual contributions of atmospheric carbon dioxide ([CO2]), temperature, and precipitation. Impacts ranged from a strong increase to a severe loss of vegetation carbon (cv), depending on differences in climate projections, as well as the physiological response to rising [CO2]. The loss of cv simulated for an extremely dry projection was primarily driven by a reduction in gross primary productivity, and secondarily by enhanced emissions from fires and autotrophic respiration. In the wet forest, less precipitation and higher temperatures equally reduced cv, while in the dry forest, the impact of precipitation was dominating. The temperature‐related reduction of cv was mainly due to a decrease in photosynthesis and only to lesser extent because of more autotrophic respiration and less stomatal conductance as a response to an increasing atmospheric evaporative demand. Under an extremely dry projection, tropical dry forests were simulated to virtually disappear, regardless of the potential fertilizing effect of rising [CO2]. This suggests a higher risk for forest loss along the drier southern fringe of the Amazon if annual precipitation will decrease substantially.
Ruthenium Pincer Complexes: Synthesis and Catalytic Applications
Authors: Younus Hussein A. , Su Wei , Ahmad Nazir , Chen Si , Verpoort Francis 
Published: January 2015

AbstractPincer‐based catalysts possess an exceptional balance of stability versus reactivity, aspects of fundamental interest in catalyst design. This balance has been well‐controlled by systematic ligand modifications along with the variation of the metal center. Ruthenium pincer complexes (RPCs), exhibit a versatile chemistry, serve as excellent precursors and find potential applications in many organic transformations. A large number of novel and valuable reactions has been developed using both stoichiometric and catalytic amounts of RPCs. Compared to the traditional ruthenium catalysts, pincer complexes often present high efficiency, selectivity and functional group tolerance. This review highlights different methodologies for the synthesis of RPCs and their catalytic applications for different reactions reported in the last decade. Additionally, the factors affecting the catalytic reactivity of the RPCs and the reaction mechanisms are discussed.magnified image
A Mild and Efficient Synthesis of Substituted Quinolines via a Cross‐Dehydrogenative Coupling of (Bio)available Alcohols and Aminoarenes
Authors: Mura Manuel G. , Rajamäki Suvi , De Luca Lidia , Cini Elena , Porcheddu Andrea 
Published: January 2015

AbstractA ruthenium‐catalysed dehydrogenative cross‐coupling of primary alcohols and imines in the presence of TFA provided a library of differently substituted quinolines. Imines can be prepared in situ from various anilines and several benzyl alcohols using a ruthenium‐catalysed hydrogen‐transfer procedure. Without changing the catalyst, quinolines can be obtained in moderate to good yields by adding various primary alcohols in the presence of TFA (30 mol%) via a “telescopic” protocol. The use of alcohols, the absence of strong oxidants and the diversity of potential starting materials make this modern version of the Skraup reaction superior to most of the conventional quinoline syntheses.magnified image
Metal‐Free Reagent Dependent SS and CC Homocoupling of α‐Enolic Dithioesters at Room Temperature: Direct Access to Fully Substituted Symmetrical Thiophenes via Chemoselective Paal–Knorr Approach
Authors: Ramulu B. Janaki , Nagaraju Anugula , Chowdhury Sushobhan , Koley Suvajit , Singh Maya Shankar 
Published: January 2015

AbstractAn unprecedented metal‐free oxidative homodimerization of α‐enolic dithioesters has been achieved for the first time at room temperature within 5–10 min. Molecular iodine promotes the SS coupling leading to S,S′‐bis(dithioacetals), while N‐chlorosuccinimide facilitates CC coupling to give α,α′‐bis(β‐oxo dithioesters) in good to excellent yields. Furthermore, the newly generated α,α′‐bis(β‐oxo dithioesters) have been directly employed in the synthesis of fully substituted thiophenes with a unique symmetrical substitution pattern in a one‐pot, two‐step reaction sequence.magnified image
Ruthenium(II)‐Catalyzed Hydrogen Transfer/Annulation Cascade Processes between Alcohols and 2‐Nitrobenzaldehydes
Authors: Li Hui‐Jing , Wang Chen‐Chao , Zhu Shuai , Dai Chun‐Yang , Wu Yan‐Chao 
Published: January 2015

AbstractThe synthesis of quinolines from alcohols and 2‐nitrobenzaldehydes is described. Unreactive alcohols and 2‐nitrobenzaldehydes were concurrently converted to the reactive reactants for a Friedländer annulation via a hydrogen transfer. Tris(triphenylphosphine)ruthenium(II) dichloride [Ru(PPh3)3Cl2] appeared to serve the dual role of an efficient hydrogen transfer catalyst and a suitable Friedländer annulation catalyst.magnified image