bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compressional wave dispersion due to rock matrix stiffening by clay squirt flow
Authors: Ba Jing , Zhao Jianguo , Carcione José M. , Huang Xingxing 
Published: June 2016

AbstractThe standard Biot‐Gassmann theory of poroelasticity fails to explain strong compressional wave velocity dispersion experimentally observed in 12 tight siltstone with clay‐filled pores. In order to analyze and understand the results, we developed a new double‐porosity model of clay squirt flow where wave‐induced local fluid flow occurs between the micropores in clay aggregates and intergranular macropores. The model is validated based on the combined study of ultrasonic experiments on specimens at different saturation conditions and theoretical predictions. The presence of a sub‐pore‐scale structure of clay micropores contained in intergranular macropores, where the fluid does not have enough time to achieve mechanical equilibrium at ultrasonic frequencies and thus stiffens the rock matrix, provides a suitable explanation of the experimental data. Moreover, the model provides a new bound for estimating the compressional wave velocity of tight rocks saturated with two immiscible liquids. The theoretical predictions indicate that the velocity variation between gas‐ and liquid‐saturated specimens is predominantly induced by the clay squirt stiffening effect on the rock matrix and not by fluid substitution. The effect contributes more than 90% to the variation in the porosity range of 0–5%. Thus, clay squirt flow dominates the relationships between compressional wave velocity and pore fluid in tight rocks.
Using timing of ice retreat to predict timing of fall freeze‐up in the Arctic
Authors: Stroeve Julienne C. , Crawford Alex D. , Stammerjohn Sharon 
Published: June 2016

AbstractReliable forecasts of the timing of sea ice advance are needed in order to reduce risks associated with operating in the Arctic as well as planning of human and environmental emergencies. This study investigates the use of a simple statistical model relating the timing of ice retreat to the timing of ice advance, taking advantage of the inherent predictive power supplied by the seasonal ice‐albedo feedback and ocean heat uptake. Results show that using the last retreat date to predict the first advance date is applicable in some regions, such as Baffin Bay and the Laptev and East Siberian seas, where a predictive skill is found even after accounting for the long‐term trend in both variables. Elsewhere, in the Arctic, there is some predictive skills depending on the year (e.g., Kara and Beaufort seas), but none in regions such as the Barents and Bering seas or the Sea of Okhotsk. While there is some suggestion that the relationship is strengthening over time, this may reflect that higher correlations are expected during periods when the underlying trend is strong.
How long does precipitation inhibit wind erosion in the Sahel?
Authors: Bergametti G. , Rajot J. L. , Pierre C. , Bouet C. , Marticorena B. 
Published: June 2016

AbstractSimultaneous measurements of saltation, wind speed, and rainfall performed in Niger before, during, and after 18 rain events are used to investigate how rain events affect wind erosion in the Sahel. The results show that the inhibition of saltation is rapid but progressive after the beginning of a rain event. The decrease of sand transport during the rain event is better linked to the time elapsed from the beginning of the rain event rather than to the cumulative rainfall. In the Sahel, after a rain event, less than 12 h is necessary to almost fully restore the sand transport potential. Our results suggest that assuming that no sand transport and dust emission occur during the 12 h following the end of a rain event could be a reasonable alternative to existing parameterizations of the influence of soil moisture on the wind erosion threshold, at least for the Sahelian conditions.
Paleofluvial landscape inheritance for Jakobshavn Isbræ catchment, Greenland
Authors: Cooper M. A. , Michaelides K. , Siegert M. J. , Bamber J. L. 
Published: June 2016

AbstractSubglacial topography exerts strong controls on glacier dynamics, influencing the orientation and velocity of ice flow, as well as modulating the distribution of basal waters and sediment. Bed geometry can also provide a long‐term record of geomorphic processes, allowing insight into landscape evolution, the origin of which may predate ice sheet inception. Here we present evidence from ice‐penetrating radar data for a large dendritic drainage network, radiating inland from Jakobshavn Isbræ, Greenland's largest outlet glacier. The size of the drainage basin is ∼450,000 km2 and accounts for about 20% of the total land area of Greenland. Topographic and basin morphometric analyses of an isostatically uplifted (ice‐free) bedrock topography suggests that this catchment predates ice sheet initiation and has likely been instrumental in controlling the location and form of the Jakobshavn ice stream, and ice flow from the deep interior to the margin, now and over several glacial cycles.
Stochastic convective parameterization improving the simulation of tropical precipitation variability in the NCAR CAM5
Authors: Wang Yong , Zhang Guang J. , Craig George C. 
Published: June 2016

AbstractThe Plant‐Craig (PC) stochastic convective parameterization scheme is implemented into the National Center for Atmospheric Research Community Atmosphere Model version 5 (CAM5) to couple with the Zhang‐McFarlane deterministic convection scheme. To evaluate its impact on tropical precipitation simulation, two experiments are conducted: one with the standard CAM5 and the other with the stochastic scheme incorporated. Results show that the PC stochastic parameterization decreases the frequency of weak precipitation and increases the frequency of strong precipitation, resulting in better agreement with observations. The most striking improvement is in the probability distribution function (PDF) of precipitation intensity, with the well‐known too‐much‐drizzle problem in CAM5 largely eliminated. In the global tropical belt, the precipitation intensity PDF from the simulation agrees remarkably well with that of Tropical Rainfall Measuring Mission observations. The stochastic scheme also yields a similar magnitude of intraseasonal variability of precipitation to observations and improves the simulation of the eastward propagating intraseasonal signals of precipitation and zonal wind.
The borehole dilatometer network of Mount Etna: A powerful tool to detect and infer volcano dynamics
Authors: Bonaccorso A. , Linde A. , Currenti G. , Sacks S. , Sicali A. 
Published: June 2016

AbstractA network of four borehole dilatometers has been installed on Etna in two successive phases (2010–2011 and 2014). The borehole dilatometers are installed in holes drilled at depths usually greater than 100 m, and they measure the volumetric strain of the surrounding rock with a nominal precision up to 10−11 in a wide frequency range (10−7–25 Hz). Here we describe the characteristics of the network and the results of the in situ calibrations obtained after the installations by different methods. We illustrate short‐term strain changes recorded during several lava fountains erupted by Etna during 2011–2013, and we also show signal changes recorded at all four stations during the lava fountain on 28 December 2014. Analytical and numerical computations constrained the eruptions source depth and also its volume change that is related to the magma volume emitted. Finally, we show the potential of the signal in the medium term to reveal strain changes related to different phases of the volcanic activity.
A 1DVAR retrieval applied to GMI: Algorithm description, validation, and sensitivities
Authors: Duncan David I. , Kummerow Christian D. 
Published: June 2016

AbstractA fully physical, 1‐D variational inversion algorithm (1DVAR) has been developed to simultaneously retrieve total precipitable water (TPW), 10 m wind speed, and cloud liquid water path (CLWP) over ocean. Results presented are for the Global Precipitation Measurement Microwave Imager (GMI), but the algorithm is adaptable to any microwave imager. The Colorado State University 1DVAR is novel in that the observation error covariances are not assumed to be zero and empirical orthogonal functions are utilized to retrieve the structure of the water vapor profile, aided by GMI's high‐frequency channels. Validation against radiosonde and ocean buoy observations demonstrates a near zero bias for wind speed and a small positive bias for water vapor, respectively, with RMS errors that rival those of benchmark products. RMS errors against validation are 2.6 mm and 1.2 m/s for TPW and wind speed. No calibration adjustments were made to achieve these results, and no “truth” data were used to train the algorithm. The advantages of this fully physical inversion are its adaptability, transparency, and full description of retrieval errors. Sensitivities of the algorithm are explored in detail.
Seasonality of global and Arctic black carbon processes in the Arctic Monitoring and Assessment Programme models
Authors: Mahmood Rashed , von Salzen Knut , Flanner Mark , Sand Maria , Langner Joakim , Wang Hailong , Huang Lin 
Published: June 2016

AbstractThis study quantifies black carbon (BC) processes in three global climate models and one chemistry transport model, with focus on the seasonality of BC transport, emissions, wet and dry deposition in the Arctic. In the models, transport of BC to the Arctic from lower latitudes is the major BC source for this region. Arctic emissions are very small. All models simulated a similar annual cycle of BC transport from lower latitudes to the Arctic, with maximum transport occurring in July. Substantial differences were found in simulated BC burdens and vertical distributions, with Canadian Atmospheric Global Climate Model (CanAM) (Norwegian Earth System Model, NorESM) producing the strongest (weakest) seasonal cycle. CanAM also has the shortest annual mean residence time for BC in the Arctic followed by Swedish Meteorological and Hydrological Institute Multiscale Atmospheric Transport and Chemistry model, Community Earth System Model, and NorESM. Overall, considerable differences in wet deposition efficiencies in the models exist and are a leading cause of differences in simulated BC burdens. Results from model sensitivity experiments indicate that convective scavenging outside the Arctic reduces the mean altitude of BC residing in the Arctic, making it more susceptible to scavenging by stratiform (layer) clouds in the Arctic. Consequently, scavenging of BC in convective clouds outside the Arctic acts to substantially increase the overall efficiency of BC wet deposition in the Arctic, which leads to low BC burdens and a more pronounced seasonal cycle compared to simulations without convective BC scavenging. In contrast, the simulated seasonality of BC concentrations in the upper troposphere is only weakly influenced by wet deposition in stratiform clouds, whereas lower tropospheric concentrations are highly sensitive.
Saharan dust outbreaks and iberulite episodes
Authors: Diaz‐Hernandez Jose L. , Sanchez‐Navas Antonio 
Published: June 2016

AbstractMineral dust aerosols coming from the arid and semiarid regions of the world can aggregate and form microspherulites under special atmospheric conditions. This is the case for iberulites, formed in the atmosphere from Saharan dust intrusions into the southern Iberian Peninsula during the summer, prompting a noteworthy case of dust accretion unique in the world. This study consists of a long‐term monitoring of Saharan dust outbreaks producing haze that reaches the southern Iberian Peninsula. Aerosol concentration, relative humidity, and temperature time series available at the ground stations in this area indicate sharp variations of these atmospheric variables during the iberulite‐forming events. Most of these events occurred during the summer (60%), with 65 episodes for the period 2005–2013, in which 107 plumes reached the Iberian Peninsula. Iberulite episodes lasted 5 days on average, during which an initial increase of particulate matter (PM) levels and temperature, accompanied by a decrease in relative humidity, was registered until the third day. These trends reversed when the plume began to abate. Our data also indicate that iberulites form during dusty episodes when a minimum threshold in the content of large aerosol particles (PM10) reached concentrations above 15 µg × m−3. Surface evaporation due to the sharply rising air temperatures give rise to clouds associated with the plume, where the water droplets that formed from condensation capture large amounts of aerosols as they fall. In this sense, muddy raindrop impacts with variable water:dust ratios recorded during red‐rain episodes are interpreted as the precursor of the iberulites. A singular process of dust aggregation is here proposed for the formation of iberulites.
Astronomical calibration and global correlation of the Santonian (Cretaceous) based on the marine carbon isotope record
Authors: Thibault N. , Jarvis I. , Voigt S. , Gale A. S. , Attree K. , Jenkyns H. C. 
Published: June 2016

AbstractHigh‐resolution records of bulk carbonate carbon isotopes have been generated for the Upper Coniacian to Lower Campanian interval of the sections at Seaford Head (southern England) and Bottaccione (central Italy). An unambiguous stratigraphic correlation is presented for the base and top of the Santonian between the Boreal and Tethyan realms. Orbital forcing of carbon and oxygen isotopes at Seaford Head points to the Boreal Santonian spanning five 405 kyr cycles (Sa1 to Sa5). Correlation of the Seaford Head time scale to that of the Niobrara Formation (Western Interior Basin) permits anchoring these records to the La2011 astronomical solution at the Santonian‐Campanian (Sa/Ca) boundary, which has been recently dated to 84.19 ± 0.38 Ma. Among the five tuning options examined, option 2 places the Sa/Ca at the 84.2 Ma 405 kyr insolation minimum and appears as the most likely. This solution indicates that minima of the 405 kyr filtered output of the resistivity in the Niobrara Formation correlate to 405 kyr insolation minima in the astronomical solution and to maxima in the filtered δ13C of Seaford Head. We suggest that variance in δ13C is driven by climate forcing of the proportions of CaCO3 versus organic carbon burial on land and in oceanic basins. The astronomical calibration generates a 200 kyr mismatch of the Coniacian‐Santonian boundary age between the Boreal Realm in Europe and the Western Interior, due either to diachronism of the lowest occurrence of the inoceramid Cladoceramus undulatoplicatus between the two regions or to remaining uncertainties of radiometric dating and cyclostratigraphic records.
Highly selective sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene)/poly(ether sulfone) blend proton exchange membranes for direct methanol fuel cells
Authors: Devi Appadurai Uma , Neelakandan Sivasubramaniyan , Nagendran Alagumalai 
Published: June 2016

ABSTRACTProton exchange membranes (PEMs) based on blends of poly(ether sulfone) (PES) and sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene) (sPVdF‐co‐HFP) were prepared successfully. Fabricated blend membranes showed favorable PEM characteristics such as reduced methanol permeability, high selectivity, and improved mechanical integrity. Additionally, these membranes afford comparable proton conductivity, good oxidative stability, moderate ion exchange capacity, and reasonable water uptake. To appraise PEM performance, blend membranes were characterized using techniques such as Fourier transform infrared spectroscopy, AC impedance spectroscopy; atomic force microscopy, and thermogravimetry. Addition of hydrophobic PES confines the swelling of the PEM and increases the ultimate tensile strength of the membrane. Proton conductivities of the blend membranes are about 10−3 S cm−1. Methanol permeability of 1.22 × 10−7cm2 s−1 exhibited by the sPVdF‐co‐HFP/PES10 blend membrane is much lower than that of Nafion‐117. AFM studies divulged that the sPVdF‐co‐HFP/PES blend membranes have nodule like structure, which confirms the presence of hydrophilic domain. The observed results demonstrated that the sPVdF‐co‐HFP/PES blend membranes have promise for possible usage as a PEM in direct methanol fuel cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43907.
Dual release kinetics of antimalarials from soy protein isolate‐carbopol‐polyacrylamide based hydrogels
Authors: Aderibigbe Blessing Atim , Mhlwatika Zandile 
Published: June 2016

ABSTRACTThe currently used antimalarials suffer from drug resistance which is hampering the global management of malaria infection. To overcome drug resistance, they are administered as combination therapies which involve combination of two or more antimalarials. In this study, chloroquine diphosphate and curcumin were encapsulated onto prepared soy protein isolate‐carbopol‐polyacrylamide based hydrogels. The hydrogels were pH sensitive and exhibited enhanced swelling capability at pH 7.4. The hydrogels were biodegradable which was observed by their SEM images after drug release. The release mechanisms of both drugs were influenced by the degree of crosslinking of the soy protein isolate in the hydrogel network and the presence of the other drug in the network. The release mechanisms of both drugs from the hydrogel networks followed super case transport II. These results suggested that the hydrogels were potential dual drug delivery systems for antimalarials whereby both drugs could work over different period of time and hence, have the potential to overcome drug resistance that is common with the presently used antimalarials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43918.
A functionally integrated thermoplastic microdevice for one‐step solid‐phase‐based nucleic acid purification and isothermal amplification for facile detection of foodborne pathogen
Authors: Ha Minh Luan , Zhang Yu , Lee Nae Yoon 
Published: June 2016

ABSTRACTIn this study, we fabricate a functionally integrated monolithic thermoplastic microdevice for continuous operation of nucleic acid purification and amplification using polycarbonate (PC). A solid‐phase‐based purification and subsequent isothermal amplification, specifically, thermal helicase‐dependent amplification (tHDA), was performed in a single operation in a valve‐free manner. PC microdevice was assembled using modified thermal bonding process under relatively low temperature and pressure condition, realized by surface chemical modification of PC into hydrophilic property using amine‐bearing polyethyleneimine (PEI). After the device sealing, only the microchannel parts were selectively modified to be hydrophobic, using epoxy‐terminated poly(dimethylsiloxane) (PDMS) (epoxy–PDMS) on amine‐coated surface for stepwise introduction of multiple reagents in a valve‐free manner. Using the integrated PC microdevice, nucleic acids from genetically modified Escherichia coli (E. coli) O157:H7 were captured inside a chamber bearing amine functionality, by electrostatic interaction, and were subsequently amplified isothermally in the same chamber. Purified DNA captured inside the microchamber was detected directly inside the chamber by fluorescence measurement, and a 92‐bp long EaeA gene, inserted into the E. coli O157:H7, was successfully amplified using the integrated PC microdevice in less than 90 min, paving the way for facile identification of foodborne pathogens with simple operation and reduced peripheral operations applicable for portable healthcare purposes. Biotechnol. Bioeng. 2016;113: 2614–2623. © 2016 Wiley Periodicals, Inc.
Exploring the N‐terminal role of a heterologous protein in secreting out of Escherichia coli
Authors: Gao Dongfang , Luan Yaqi , Liang Quanfeng , Qi Qingsheng 
Published: June 2016

ABSTRACTEscherichia coli is commonly used as a host for the extracellular production of proteins. However, its secretion capacity is often limited to a frustratingly low level compared with other expression hosts, because E. coli has a complex cell envelope with two layers. In previous report, we identified that the catalytic domain of a cellulase (Cel‐CD) from Bacillus subtilis can be secreted into the medium from recombinant E. coli in large quantities without its native signal peptide. In this study, we proved the N‐terminal sequence of the full length Cel‐CD played a crucial role in transportation through both inner and outer membranes. By subcellular location analysis, we verified that the secretion was a two‐step process via the SecB‐dependent pathway through the inner membrane and an unknown pathway through the outer membrane. However, the N‐terminal region of Cel‐CD is polar and hydrophilic, which showed no similarities to other typical signal sequences. Random mutagenesis experiment suggested that the N‐terminal sequence is a compromising result of transportation through inner and outer membranes. This is the first report that a “non‐classical signal peptide” can guide recombinant proteins out of the cells from cytoplasm. Biotechnol. Bioeng. 2016;113: 2561–2567. © 2016 Wiley Periodicals, Inc.
Newly identified bacteriolytic enzymes that target a wide range of clinical isolates of Clostridium difficile
Authors: Mehta Krunal K. , Paskaleva Elena E. , Wu Xia , Grover Navdeep , Mundra Ruchir V. , Chen Kevin , Zhang Yongrong , Yang Zhiyong , Feng Hanping , Dordick Jonathan S. , Kane Ravi S. 
Published: June 2016

ABSTRACTClostridium difficile has emerged as a major cause of infectious diarrhea in hospitalized patients, with increasing mortality rate and annual healthcare costs exceeding $3 billion. Since C. difficile infections are associated with the use of antibiotics, there is an urgent need to develop treatments that can inactivate the bacterium selectively without affecting commensal microflora. Lytic enzymes from bacteria and bacteriophages show promise as highly selective and effective antimicrobial agents. These enzymes often have a modular structure, consisting of a catalytic domain and a binding domain. In the current work, using consensus catalytic domain and cell‐wall binding domain sequences as probes, we analyzed in silico the genome of C. difficile, as well as phages infecting C. difficile. We identified two genes encoding cell lytic enzymes with possible activity against C. difficile. We cloned the genes in a suitable expression vector, expressed and purified the protein products, and tested enzyme activity in vitro. These newly identified enzymes were found to be active against C. difficile cells in a dose‐dependent manner. We achieved a more than 4‐log reduction in the number of viable bacteria within 5 h of application. Moreover, we found that the enzymes were active against a wide range of C. difficile clinical isolates. We also characterized the biocatalytic mechanism by identifying the specific bonds cleaved by these enzymes within the cell wall peptidoglycan. These results suggest a new approach to combating the growing healthcare problem associated with C. difficile infections. Biotechnol. Bioeng. 2016;113: 2568–2576. © 2016 Wiley Periodicals, Inc.