bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple transgressions and slow evolution shape the phylogeographic pattern of the blind cave-dwelling shrimp Typhlocaris
Authors: Guy-Haim Tamar , Simon-Blecher Noa , Frumkin Amos , Naaman Israel , Achituv Yair
Published: March 2018

Background. Aquatic subterranean species often exhibit disjunct distributions, with high level of endemism and small range, shaped by vicariance, limited dispersal, and evolutionary rates. We studied the disjunct biogeographic patterns of an endangered blind cave shrimp, Typhlocaris, and identified the geological and evolutionary processes that have shaped its divergence pattern.

Methods. We collected Typlocaris specimens of three species (T. galilea, T. ayyaloni, and T. salentina), originating from subterranean groundwater caves by the Mediterranean Sea, and used three mitochondrial genes (12S, 16S, COI) and four nuclear genes (18S, 28S, ITS, H3) to infer their phylogenetic relationships. Using the radiometric dating of a geological formation (Bira) as a calibration node, we estimated the divergence times of the Typhlocaris species and the molecular evolution rates.

Results. The multi-locus ML/Bayesian trees of the concatenated seven gene sequences showed that T. salentina (Italy) and T. ayyaloni (Israel) are more closely related than T. galilea (Israel). The divergence time of T. ayyaloni and T. salentina from T. galilea was according to COI – 6.0 [4.5-7.2] Ma and according to 16S – 5.9 [3.6-7.4] Ma. The computed interspecific evolutionary rates for COI – 0.0074 substitutions/Myr and for 16S – 0.0041 substitutions/Myr.

Discussion. Two consecutive vicariant events have shaped the phylogeographic patterns of Typhlocaris species. First, T. galilea was tectonically isolated from its siblings in the Mediterranean Sea by the arching uplift of the central mountain range of Israel ca. 7 Ma. Secondly, T. ayyaloni and T. salentina were stranded and separated by a marine transgression ca. 6 Ma, occurring just before the Messinian Salinity Crisis. Our estimated molecular evolution rates were in one order of magnitude lower than the rates of closely related crustaceans, as well as of other stygobiont species. We suggest that this slow evolution reflects the ecological conditions prevailing in the highly isolated subterranean enclosures inhabited by Typhlocaris.
Unbalanced sentiment classification: an assessment of ANN in the context of sampling the majority class
Authors: Moraes Rodrigo , Valiati João Francisco , Gavião Neto Wilson Pires
Published: March 2018

Many people make their opinions available on the Internet nowadays, and researchers have been proposing methods to automate the task of classifying textual reviews as positive or negative. Usual supervised learning techniques have been adopted to accomplish such a task. In practice, positive reviews are abundant in comparison to negative's. This context poses challenges to learning-based methods and data undersampling/oversampling are popular preprocessing techniques to overcome the problem. A combination of sampling techniques and learning methods, like Artificial Neural Networks (ANN) or Support Vector Machines (SVM), has been successfully adopted as a classification approach in many areas, while the sentiment classification literature has not explored ANN in studies that involve sampling methods to balance data. Even the performance of SVM, which is widely used as a sentiment learner, has been rarely addressed under the context of a preceding sampling method. This paper addresses document-level sentiment analysis with unbalanced data and focus on empirically assessing the performance of ANN in the context of undersampling the (majority) set of positive reviews. We adopted the performance of SVM as a baseline, since some studies have indicated SVM as being less subject to the class imbalance problem. Results are produced in terms of a traditional bag-of-words model with popular feature selection and weighting methods. Our experiments indicated that SVM are more stable than ANN in highly unbalanced (80%) data scenarios. However, under the discarding of information generated by random undersampling, ANN outperform SVM or produce comparable results.
Identification and characterization of the cytosine-5 DNA methyltransferase gene family inSalvia miltiorrhiza
Authors: Li Jiang , Li Caili , Lu Shanfa
Published: March 2018

Cytosine DNA methylation is highly conserved epigenetic modification involved in a wide range of biological processes in eukaryotes. It was established and maintained by cytosine-5 DNA methyltransferases (C5-MTases) in plants. Through genome-wide identification, eight putativeSmC5-MTasegenes were identified from the genome ofSalvia miltiorrhiza, a well-known traditional Chinese medicine material and an emerging model medicinal plant. Based on conserved domains and phylogenetic analysis, eightSmC5-MTasegenes were divided into four subfamilies, includingMET,CMT,DRMandDNMT2. Genome-wide comparative analysis of theC5-MTasegene family inS. miltiorrhizaandArabidopsis thaliana, including gene structure, sequence features, sequence alignment and conserved motifs, was carried out. The results showed conservation and divergence of the members of each subfamily in plants. The length ofSmC5-MTaseopen reading frames ranges widely from 1,152 (SmDNMT2) to 5,034 bp (SmMET1). The intron number ofSmC5-MTasesvaries between 7 (SmDRM1) and 20 (SmCMT1andSmCMT2b). These features were similar to their counterparts fromArabidopsis. Sequence alignment and conserved motif analysis showed the existence of highly conserved and subfamily-specific motifs in the C5-MTases analyzed. Differential transcript abundance was detected forSmC5-MTases, implying genome-wide variance of DNA methylation in different organs and tissues. Transcriptome-wide analysis showed that the transcript levels of allSmC5-MTasegenes was slightly changed under yeast extract and methyl jasmonate treatments. SixSmC5-MTases, includingSmMET1,SmCMT1,SmCMT2a,SmCMT2b,SmCMT3andSmDRM1, were salicylic acid-responsive, suggesting the involvement ofSmC5-MTases in salicylic acid-dependent immunity. These results provide useful information for demonstrating the role of DNA methylation in bioactive compound biosynthesis and Dao-di herb formation in medicinal plants.
Genetic analysis of ‘CandidatusPhytoplasma aurantifolia’ associated with witches’ broom on acid lime trees
Authors: Al-Ghaithi Aisha G. , Al-Subhi Ali M. , Al-Mahmooli Issa H. , Al-Sadi Abdullah M.
Published: March 2018

“CandidatusPhytoplasma aurantifolia” is associated with witches’ broom disease of lime in Oman and the UAE. A previous study showed that an infection by phytoplasma may not necessarily result in the physical appearance of witches’ broom symptoms in some locations in Oman and the UAE. This study investigated whether phytoplasma strains belonging to “Ca.P. aurantifolia” (based on the 16S rRNA gene analysis) in locations where disease symptoms are expressed are different from phytoplasma in locations where disease symptoms are not expressed. About 21 phytoplasma strains (15 from areas and trees with disease symptoms and six from areas and trees without disease symptoms) were included in the analysis. The study utilized sequences of the imp and SAP11 genes to characterize the 21 strains. Phylogenetic analysis of both genes showed that the 21 strains are similar to each other and to reference strains in GenBank. The study shows that there is a low level of diversity among all phytoplasma strains. In addition, it shows that phytoplasma in places where witches’ broom symptoms are not expressed are similar to phytoplasma in places where disease symptoms are expressed. This may suggest that disease expression is not linked to the presence of different phytoplasma strains, but may be due to other factors such as weather conditions.
Mercury in the Black Sea: New Insights From Measurements and Numerical Modeling
Authors: Rosati G. , Heimbürger L. E. , Melaku Canu D. , Lagane C. , Laffont L. , Rijkenberg M. J. A. , Gerringa L. J. A. , Solidoro C. , Gencarelli C. N. , Hedgecock I. M. , De Baar H. J. W. , Sonke J. E.
Published: March 2018

Redox conditions and organic matter control marine methylmercury (MeHg) production. The Black Sea is the world's largest and deepest anoxic basin and is thus ideal to study Hg species along the extended redox gradient. Here we present new dissolved Hg and MeHg data from the 2013 GEOTRACES MEDBlack cruise (GN04_leg2) that we integrated into a numerical 1‐D model, to track the fate and dynamics of Hg and MeHg. Contrary to a previous study, our new data show highest MeHg concentrations in the permanently anoxic waters. Observed MeHg/Hg percentage (range 9–57%) in the anoxic waters is comparable to other subsurface maxima in oxic open‐ocean waters. With the modeling we tested for various Hg methylation and demethylation scenarios along the redox gradient. The results show that Hg methylation must occur in the anoxic waters. The model was then used to simulate the time evolution (1850–2050) of Hg species in the Black Sea. Our findings quantify (1) inputs and outputs of HgT (~31 and ~28 kmol yr−1) and MeHgT (~5 and ~4 kmol yr−1) to the basin, (2) the extent of net demethylation occurring in oxic (~1 kmol yr−1) and suboxic water (~6 kmol yr−1), (3) and the net Hg methylation in the anoxic waters of the Black Sea (~11 kmol yr−1). The model was also used to estimate the amount of anthropogenic Hg (85–93%) in the Black Sea.
Observations of Blue Discharges Associated With Negative Narrow Bipolar Events in Active Deep Convection
Authors: Liu Feifan , Zhu Baoyou , Lu Gaopeng , Qin Zilong , Lei Jiuhou , Peng Kang‐Ming , Chen Alfred B. , Huang Anjing , Cummer Steven A. , Chen Mingli , Ma Ming , Lyu Fanchao , Zhou Helin
Published: March 2018

On 19 August 2012, the Imager of Sprites and Upper Atmospheric Lightning on board the FORMOSAT‐2 satellite captured a sequence of seven blue discharges within 1 min that emanated from a parent thunderstorm over Lake Taihu in East China. The analysis of lightning activity produced in the thunderstorm indicates that at least six of these events occurred in association with negative narrow bipolar events (NBEs) that were concurrent with the blue discharge by less than 1 ms, and negative cloud‐to‐ground occurred within 6 s before each blue discharge, which is in agreement with the modeling presented by Krehbiel et al. (2008). Therefore, the frequent occurrence of negative cloud‐to‐ground could provide the favorable condition for the production of blue discharges, and negative NBEs are probably the initial event of blue discharges. The detection of negative NBEs might provide a convenient approach to detect the occurrence of blue discharges as lightning bolt shooting upward from the top of energetic thunderstorms.
Slow Earthquakes in the Microseism Frequency Band (0.1–1.0 Hz) off Kii Peninsula, Japan
Authors: Kaneko Lisa , Ide Satoshi , Nakano Masaru
Published: March 2018

It is difficult to detect the signal of slow deformation in the 0.1–1.0 Hz frequency band between tectonic tremors and very low frequency events, where microseism noise is dominant. Here we provide the first evidence of slow earthquakes in this microseism band, observed by the DONET1 ocean bottom seismometer network, after an Mw 5.8 earthquake off Kii Peninsula, Japan, on 1 April 2016. The signals in the microseism band were accompanied by signals from active tremors, very low frequency events, and slow slip events that radiated from the shallow plate interface. We report the detection and locations of events across five frequency bands, including the microseism band. The locations and timing of the events estimated in the different frequency bands are similar, suggesting that these signals radiated from a common source. The observed variations in detectability for each band highlight the complexity of the slow earthquake process.
Geologic Slip‐Rate Determinations on the Talas‐Fergana Fault: Mismatch With Geodetic Slip Rate
Authors: Rust Derek , Korzhenkov Andrey , Tibaldi Alessandro
Published: March 2018

Detailed new paleoseismic field investigations at two sites on the Talas‐Fergana fault, a poorly known strike‐slip structure that transects the Tien Shan mountain range, document late Holocene slip rates of 11–16 mm a−1. This prominent structure is distinctive in striking obliquely NW‐SE across the Tien Shan, which is otherwise dominated by contractional structures striking generally E‐W. Moreover, a satellite‐based Global Positioning System network spanning the Tien Shan orogen records active N‐S contraction rates of ~20 mm a−1, but limits slip on the Talas‐Fergana fault to <2 mm a−1. This profound mismatch between long‐term geologic and short‐term geodetic slip rates, which may suggest temporal variability in slip, highlights the importance of field‐based investigations as a complement to remotely sensed data, particularly in evaluating models of lithosphere behavior and earthquake probabilities on presently locked faults such as the Talas‐Fergana.
ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms
Authors: Bentley S. N. , Watt C. E. J. , Owens M. J. , Rae I. J.
Published: March 2018

Ultralow frequency (ULF) waves in the magnetosphere are involved in the energization and transport of radiation belt particles and are strongly driven by the external solar wind. However, the interdependency of solar wind parameters and the variety of solar wind‐magnetosphere coupling processes make it difficult to distinguish the effect of individual processes and to predict magnetospheric wave power using solar wind properties. We examine 15 years of dayside ground‐based measurements at a single representative frequency (2.5 mHz) and a single magnetic latitude (corresponding to L ∼ 6.6RE). We determine the relative contribution to ULF wave power from instantaneous nonderived solar wind parameters, accounting for their interdependencies. The most influential parameters for ground‐based ULF wave power are solar wind speed vsw, southward interplanetary magnetic field component Bz<0, and summed power in number density perturbations δNp. Together, the subordinate parameters Bz and δNp still account for significant amounts of power. We suggest that these three parameters correspond to driving by the Kelvin‐Helmholtz instability, formation, and/or propagation of flux transfer events and density perturbations from solar wind structures sweeping past the Earth. We anticipate that this new parameter reduction will aid comparisons of ULF generation mechanisms between magnetospheric sectors and will enable more sophisticated empirical models predicting magnetospheric ULF power using external solar wind driving parameters.
The Identification of Waves at Discrete Frequencies at the Geostationary Orbit: The Role of the Data Analysis Techniques and the Comparison With Solar Wind Observations
Authors: Di Matteo S. , Villante U.
Published: March 2018

Following a recent investigation in which we examined the performance of two methods (the Welch method and the multitaper windowing and F test) on the identification of fluctuations of the solar wind dynamic pressure in streams following interplanetary shocks, we extend our analysis to the magnetospheric field fluctuations detected at the geostationary orbit after the occurrence of the related sudden impulses. First, we show that a contamination of the experimental results, dramatic in statistical investigations, might come from the rotation of measurements in the field‐aligned coordinates when the field direction is determined, point by point, by the running averages: this procedure creates spurious events at frequencies related to the length of the running average window. These aspects do not appear in a fixed coordinate system, as determined by evaluating the average field vector for the entire interval. In this system, we examined 124 magnetospheric structures following sudden impulses: the Welch method/multitaper windowing and F test agreement in the wave identification and frequency estimate was achieved for ≈50% of events, and some evidence for higher percentages of events occurs at f ≈ 1.5–1.7, f ≈ 2.2–2.4, ≈3.9–4.2, and, more explicitly, at f ≈ 4.2–4.7 mHz. Oscillation modes with the same characteristics at different local times were rarely observed. An analysis of case events reveals that fluctuations of the solar wind pressure may drive magnetospheric fluctuations at the same frequencies; in addition, the manifestation of modes, not appearing in the solar wind, might be related to the magnetospheric compression or to other processes triggered by the shock arrival.
The Role of Storm Time Electrodynamics in Suppressing the Equatorial Plasma Bubble Development in the Recovery Phase of a Geomagnetic Storm
Authors: Sripathi S. , Banola S. , Emperumal K. , Suneel Kumar B. , Radicella Sandro M.
Published: March 2018

We investigate the role of storm time electrodynamics in suppressing the equatorial plasma bubble (EPB) development using multi‐instruments over India during a moderate geomagnetic storm that occurred on 2 October 2013 where Dst minimum reached ~−80 nT. This storm produced unique signatures in the equatorial ionosphere such that equatorial electrojet strength showed signatures of an abrupt increase of its strength to 150 nT and occurrence of episodes of counter electrojet events. During the main phase of the storm, the interplanetary magnetic field Bz is well correlated with the variations in the equatorial electrojet/counter electrojet suggesting the role of undershielding/overshielding electric fields of magnetospheric origin. Further, observations showed the presence of strong F3 layers at multiple times at multiple stations due to undershielding electric field. Interestingly, we observed simultaneous presence of F3 layers and suppression of EPBs in the dusk sector during the recovery phase. While strong EPBs were observed before and after the day of the geomagnetic storm, suppression of the EPBs on the storm day during “spread F season” is intriguing. Our further analysis using low‐latitude station, Hyderabad, during the time of prereversal enhancement suggests that intense Esb layers were observed on the storm day but were absent/weak on quiet days. Based on these results, we suggest that the altitude/latitude variation of disturbance dynamo electric fields/disturbance winds may be responsible for simultaneous detection of F3 layers, occurrence of low‐latitude Es layers, and suppression of EPBs during the storm day along the sunset terminator.
Understanding the Twist Distribution Inside Magnetic Flux Ropes by Anatomizing an Interplanetary Magnetic Cloud
Authors: Wang Yuming , Shen Chenglong , Liu Rui , Liu Jiajia , Guo Jingnan , Li Xiaolei , Xu Mengjiao , Hu Qiang , Zhang Tielong
Published: March 2018

Magnetic flux rope (MFR) is the core structure of the greatest eruptions, that is, the coronal mass ejections (CMEs), on the Sun, and magnetic clouds are posteruption MFRs in interplanetary space. There is a strong debate about whether or not a MFR exists prior to a CME and how the MFR forms/grows through magnetic reconnection during the eruption. Here we report a rare event, in which a magnetic cloud was observed sequentially by four spacecraft near Mercury, Venus, Earth, and Mars, respectively. With the aids of a uniform‐twist flux rope model and a newly developed method that can recover a shock‐compressed structure, we find that the axial magnetic flux and helicity of the magnetic cloud decreased when it propagated outward but the twist increased. Our analysis suggests that the “pancaking” effect and “erosion” effect may jointly cause such variations. The significance of the pancaking effect is difficult to be estimated, but the signature of the erosion can be found as the imbalance of the azimuthal flux of the cloud. The latter implies that the magnetic cloud was eroded significantly leaving its inner core exposed to the solar wind at far distance. The increase of the twist together with the presence of the erosion effect suggests that the posteruption MFR may have a high‐twist core enveloped by a less‐twisted outer shell. These results pose a great challenge to the current understanding on the solar eruptions as well as the formation and instability of MFRs.
Improved Model Fitting for the Empirical Green's Function Approach Using Hierarchical Models
Authors: Van Houtte Chris , Denolle Marine
Published: March 2018

Stress drops calculated from source spectral studies currently show larger variability than what is implied by empirical ground motion models. One of the potential origins of the inflated variability is the simplified model‐fitting techniques used in most source spectral studies. This study examines a variety of model‐fitting methods and shows that the choice of method can explain some of the discrepancy. The preferred method is Bayesian hierarchical modeling, which can reduce bias, better quantify uncertainties, and allow additional effects to be resolved. Two case study earthquakes are examined, the 2016 MW7.1 Kumamoto, Japan earthquake and a MW5.3 aftershock of the 2016 MW7.8 Kaikōura earthquake. By using hierarchical models, the variation of the corner frequency, fc, and the falloff rate, n, across the focal sphere can be retrieved without overfitting the data. Other methods commonly used to calculate corner frequencies may give substantial biases. In particular, if fc was calculated for the Kumamoto earthquake using an ω‐square model, the obtained fc could be twice as large as a realistic value.
Reconstructing Tropical Pacific Sea Level Variability for the Period 1961–2002 Using a Linear Multimode Model
Authors: Greatbatch Richard J. , Zhu Xiaoting , Claus Martin
Published: March 2018

Monthly mean sea level anomalies in the tropical Pacific for the period 1961–2002 are reconstructed using a linear, multimode model driven by monthly mean wind stress anomalies from the NCEP/NCAR and ERA‐40 reanalysis products. Overall, the sea level anomalies reconstructed by both wind stress products agree well with the available tide gauge data, although with poor performance at Kanton Island in the western‐central equatorial Pacific and reduced amplitude at Christmas Island. The reduced performance is related to model error in locating the pivot point in sea level variability associated with the so‐called “tilt” mode. We present evidence that the pivot point was further west during the period 1993–2014 than during the period 1961–2002 and attribute this to a persistent upward trend in the zonal wind stress variance along the equator west of
W throughout the period 1961–2014. Experiments driven by the zonal component of the wind stress alone reproduce much of the trend in sea level found in the experiments driven by both components of the wind stress. The experiments show an upward trend in sea level in the eastern tropical Pacific over the period 1961–2002, but with a much stronger upward trend when using the NCEP/NCAR product. We argue that the latter is related to an overly strong eastward trend in zonal wind stress in the eastern‐central Pacific that is believed to be a spurious feature of the NCEP/NCAR product.
Spatial Representativeness of PM2.5 Concentrations Obtained Using Observations From Network Stations
Authors: Shi Xiaoqin , Zhao Chuanfeng , Jiang Jonathan H. , Wang Chunying , Yang Xin , Yung Yuk L.
Published: March 2018

Haze has been a focused air pollution phenomenon in China, and its characterization is highly desired. Aerosol properties obtained from a single station are frequently used to represent the haze condition over a large domain, such as tens of kilometers, which could result in high uncertainties due to their spatial variation. Using a high‐resolution network observation over an urban city in North China from November 2015 to February 2016, this study examines the spatial representativeness of ground station observations of particulate matter with diameters less than 2.5 μm (PM2.5). We developed a new method to determine the representative area of PM2.5 measurements from limited stations. The key idea is to determine the PM2.5 spatial representative area using its spatial variability and temporal correlation. We also determine stations with large representative area using two grid networks with different resolutions. Based on the high spatial resolution measurements, the representative area of PM2.5 at one station can be determined from the grids with high correlations and small differences of PM2.5. The representative area for a single station in the study period ranges from 0.25 to 16.25 km2 but is less than 3 km2 for more than half of the stations. The representative area varies with locations, and observation at 10 optimal stations would have a good representativeness of those obtained from 169 stations for the 4 month time scale studied. Both evaluations with an empirical orthogonal function analysis and with independent data set corroborate the validity of the results found in this study.
A Linear Dynamical Systems Approach to Streamflow Reconstruction Reveals History of Regime Shifts in Northern Thailand
Authors: Nguyen Hung T. T. , Galelli Stefano
Published: March 2018

Catchment dynamics is not often modeled in streamflow reconstruction studies; yet, the streamflow generation process depends on both catchment state and climatic inputs. To explicitly account for this interaction, we contribute a linear dynamic model, in which streamflow is a function of both catchment state (i.e., wet/dry) and paleoclimatic proxies. The model is learned using a novel variant of the Expectation‐Maximization algorithm, and it is used with a paleo drought record—the Monsoon Asia Drought Atlas—to reconstruct 406 years of streamflow for the Ping River (northern Thailand). Results for the instrumental period show that the dynamic model and the linear regression benchmark have similar performance but the dynamic model is better at capturing prolonged droughts and pluvials. More importantly, the reconstructed trajectory of the state variable provides valuable insights about the catchment history—e.g., regime‐like behavior—thereby complementing the information contained in the reconstructed streamflow time series. The proposed technique can replace linear regression, since it only requires information on streamflow and climatic proxies (e.g., tree‐rings, drought indices); furthermore, it is capable of readily generating stochastic streamflow replicates. With a marginal increase in computational requirements, the dynamic model brings more desirable features and value to streamflow reconstructions.
Does a Local B‐Minimum Appear in the Tail Current Sheet During a Substorm Growth Phase?
Authors: Sergeev V. A. , Gordeev E. I. , Merkin V. G. , Sitnov M. I.
Published: March 2018

Magnetic configurations with dBz/dr > 0 in the midtail current sheet are potentially unstable to various instabilities associated with the explosive substorm onset. Their existence is hard to confirm with observations of magnetospheric spacecraft. Here we use remote sensing by low‐altitude spacecraft that measured the loss cone filling rate during electron‐rich solar particle event, providing information about magnetic properties of the tail current sheet. We found a latitudinally localized anisotropic 30 keV electron loss cone region embedded inside an extended region of isotropic solar electron precipitation. It was persistently observed for more than 0.5 h during isolated growth phase event by six Polar Operational Environmental Satellites spacecraft, which crossed the premidnight auroral oval. The embedded anisotropic region was observed 1° poleward of the outer radiation belt boundary over 4–5 h wide magnetic local time sector, suggesting a persistent ridge‐type Bz2/j maximum in the equatorial plasma sheet at distances 15–20 RE. We discuss infrequent observations of such events taking into account recent results of global magnetohydrodynamic simulations.
Persistent Environmental Stress Delayed the Recovery of Marine Communities in the Aftermath of the Latest Permian Mass Extinction
Authors: Foster W. J. , Lehrmann D. J. , Yu M. , Ji L. , Martindale R. C.
Published: March 2018

The aftermath of the latest Permian mass extinction is a key interval for the evolution of modern marine ecosystems. It has been hypothesized that the magnitude of the mass extinction delayed the subsequent recovery, and so to test this, we undertook the highest resolution study to date of the post‐extinction (Griesbachian) microbialite unit on the Great Bank of Guizhou, south China. The benthic community from the microbialite unit is taxonomically diverse when compared to other coeval deposits, recording both inarticulate and articulate brachiopods, crinoids, echinoids, bivalves, gastropods, microconchids, and ostracods. Here we recognize 49 taxa from 4,557 individuals, which raise the known diversity of the Great Bank of Guizhou basal microbialite unit to 84 invertebrate species, making it the most diverse Early Triassic community currently reported. About 89% of the genera are Permian holdovers, whilst only 13% of the species are Permian holdovers. These new data record no temporal trends in the species richness, Simpson diversity, Simpson effective diversity, taxonomic distinctness, functional diversity, or body size of the benthos during the post‐extinction microbialite unit. Nevertheless, the small body sizes of the benthic community, prevalence of opportunistic taxa (e.g., Claraia), and the large lophophoral cavity in the lingulid brachiopod, Sinolingularia huananensis, suggests that these animals lived in a highly stressed environment. We propose that the microbialite unit contains a survival fauna in an interval that represents persistent environmental stress from the latest Permian mass extinction event, associated with deoxygenation, high temperatures, elevated atmospheric carbon dioxide levels (pCO2), and elevated primary productivity.
Improving the Ductility of Mg–Gd–Y–Zr Alloy through Extrusion and a Following Rolling
Authors: Wan Yingchun , Liu Chuming , Xiao Hongchao , Gao Yonghao , Jiang Shunong , Chen Zhiyong
Published: March 2018

Ductility of the Mg–8Gd–3Y–0.4Zr alloy is improved through extrusion and a following rolling performed on the as‐cast alloy. Microstructure evolution, texture, and mechanical properties of the alloy are systematically investigated. The results indicate that the continuous‐cluster distributed β phase particles observed in the as‐cast alloy are fragmented and dissolved during the plastic deformation. Nearly random texture, improved ductility (by 60%), and strength (by 23%) are obtained. To uncover the formation mechanism of the texture, uniaxial compression on the alloys with and without homogenization (to obtain alloys without and with β phase) is performed. The microstructure characterization reveals that β phase impedes the grain boundary immigration, resulting in the nearly random texture, thereby improving the mechanical properties, especially the ductility of the alloy.
Miniature Soft Electromagnetic Actuators for Robotic Applications
Authors: Do Thanh Nho , Phan Hung , Nguyen Thuc‐Quyen , Visell Yon
Published: March 2018

Electromagnetic actuators (EMAs) serve the majority of motion control needs in fields ranging from industrial robotics to automotive systems and biomedical devices, due to their unmatched combination of speed, precision, force, and scalability. This paper describes the design and fabrication of miniature soft EMAs that operate based on the Lorentz force principle. The actuators are fabricated from silicone polymer, liquid metal (LM) alloy (eutectic gallium indium, EGaIn), and magnetic (NdFeB) powder. They are small, intrinsically deformable, and can be fabricated using simple techniques. The central elements of the actuators are fine, 3D helical coil conductors, which are used as electromagnetic inductors. The coils are formed from stretchable filaments that are filled with a LM alloy. To achieve high power densities, the filaments themselves may be fabricated from colloids of EGaIn microdroplets in a silicone polymer matrix, allowing them to dissipate heat and accommodate high currents, and thus high forces. Millimeter‐scale cylindrical actuators are demonstrated for linear high frequency motion and articulated devices for bending motion. These actuators are applied in a vibrotactile feedback display and in a miniature soft robotic gripper.
Oxidoreductase‐Initiated Radical Polymerizations to Design Hydrogels and Micro/Nanogels: Mechanism, Molding, and Applications
Authors: Wang Xia , Chen Shuangshuang , Wu Dongbei , Wu Qing , Wei Qingcong , He Bin , Lu Qinghua , Wang Qigang
Published: March 2018

Due to their 3D cross‐linked networks and tunable physicochemical properties, polymer hydrogels with different sizes are applied widely in tissue engineering, drug‐delivery systems, pollution regulation, ionic conducting electrolytes, agricultural drought‐resistance, cosmetics, and the food industry. Novel, environmentally friendly, and efficient oxidoreductase‐initiated radical polymerizations to design hydrogels and micro/nanogels have gained increasing attention. Herein, the recent advances on the use of novel enzyme‐initiated systems for hydrogel polymerization, including the mechanisms, and molding of polymeric and hybrid‐polymeric networks are reviewed. Preliminary progress related to interfacial enzymatic polymerization for the generation of hybrid micro/nanogels is introduced as an emerging initiating approach. In addition, certain biological applications in tissue engineering, bioimaging, and therapy are demonstrated step by step. Finally, some perspectives on the safety profile of enzymatic formed hydrogels, new enzymatic systems, and potential theranostic applications are discussed.
Template Conversion of Covalent Organic Frameworks into 2D Conducting Nanocarbons for Catalyzing Oxygen Reduction Reaction
Authors: Xu Qing , Tang Yanping , Zhang Xiaobin , Oshima Yoshifumi , Chen Qiuhong , Jiang Donglin
Published: March 2018

Progress over the past decades in porous materials has exerted great effect on the design of metal‐free carbon electrochemical catalysts in fuel cells. The carbon material must combine three functions, i.e., electrical conductivity for electron transport, optimal pores for ion motion, and abundant heteroatom sites for catalysis. Here, an ideal carbon catalyst is achieved by combining two strategies—the use of a 2D covalent organic framework (COF) and the development of a suitable template to guide the pyrolysis. The COF produces nanosized carbon sheets that combine high conductivity, hierarchical porosity, and abundant heteroatom catalytic edges. The catalysts achieve superior performance to authentic Pt/C with exceptional onset potential (0 V vs −0.03 V), half‐wave potentials (−0.11 V vs −0.16 V), high limit current density (7.2 mA cm−2 vs 6.0 mA cm−2), low Tafel slope (110 mV decade−1 vs 121 mV decade−1), long‐time stability, and methanol tolerance. These results reveal a novel material platform based on 2D COFs for designing novel 2D carbon materials.
Metal–Organic‐Framework‐Assisted In Vivo Bacterial Metabolic Labeling and Precise Antibacterial Therapy
Authors: Mao Duo , Hu Fang , Kenry  , Ji Shenglu , Wu Wenbo , Ding Dan , Kong Deling , Liu Bin
Published: March 2018

Bacterial infection is one of the most serious physiological conditions threatening human health. There is an increasing demand for more effective bacterial diagnosis and treatment through noninvasive theranostic approaches. Herein, a new strategy is reported to achieve in vivo metabolic labeling of bacteria through the use of MIL‐100 (Fe) nanoparticles (NPs) as the nanocarrier for precise delivery of 3‐azido‐d‐alanine (d‐AzAla). After intravenous injection, MIL‐100 (Fe) NPs can accumulate preferentially and degrade rapidly within the high H2O2 inflammatory environment, releasing d‐AzAla in the process. d‐AzAla is selectively integrated into the cell walls of bacteria, which is confirmed by fluorescence signals from clickable DBCO‐Cy5. Ultrasmall photosensitizer NPs with aggregation‐induced emission characteristics are subsequently designed to react with the modified bacteria through in vivo click chemistry. Through photodynamic therapy, the amount of bacteria on the infected tissue can be significantly reduced. Overall, this study demonstrates the advantages of metal–organic‐framework‐assisted bacteria metabolic labeling strategy for precise bacterial detection and therapy guided by fluorescence imaging.
Nickel‐Catalyzed Tandem Knoevenagel Condensation and Intramolecular Direct Arylation: Synthesis of Pyrazolo[5,1‐a]‐isoquinoline Derivatives
Authors: Dhiman Shiv , Nandwana Nitesh Kumar , Saini Hitesh Kumar , Kumar Dalip , Rangan Krishnan , Robertson Katherine N. , Jha Mukund , Kumar Anil
Published: March 2018

A simple and efficient method for the synthesis of pyrazolo[5,1‐a]isoquinoline derivatives has been developed using the nickel‐catalyzed reaction of 1‐aryl‐2‐(1H‐pyrazol‐1‐yl)ethan‐1‐ones and 2‐bromo aldehydes. The overall transformation involves tandem Knoevenagel condensation and intramolecular direct arylation via activation of the C5−H bond of the pyrazole ring. A series of 27 drug‐like aroyl−substituted pyrazolo[5,1‐a]isoquinolines has been synthesized in moderate to good yields.

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DNA for Assembly and Charge Transport Photocatalytic Reduction of CO2
Authors: Ma Ke , Yehezkeli Omer , He Liangcan , Cha Jennifer N.
Published: March 2018

This report demonstrates the use of DNA to spatially organize photoactive nanocrystals into well‐defined Z‐scheme architectures to facilitate CO2 reduction to usable fuels upon solar irradiation through electron transfer. Coupling donor (Titanium Oxide, TiO2) and acceptor (Cadmium Sulfide, CdS) nanocrystals with DNA yield a 5.25‐fold improvement in CO2 reduction over simply mixing the photocatalysts in solution. In addition, it is demonstrated that electron transfer occurs over distances far greater than those achieved with polyethylene glycol spacer. Efficient Z‐scheme photocatalytic reduction of CO2 is observed for DNA lengths of 10–80 bases, which separate the donor and acceptor nanocrystals by 3–24 nm. More significantly, an interparticle distance of 9–10 nm yields the highest conversion of CO2, which is found for nanocrystals spaced using either linear 30mer double strand DNA (dsDNA) or a 40mer DNA composed of both linear and hairpin DNA. When the amount of 30mer DNA linking the photocatalysts is lowered, a corresponding decrease in CO2 reduction yields is seen, showcasing the role of DNA in mediating electron transfer. These results demonstrate the highly unique attributes of DNA as both a templating agent for precise nanoscale assembly and for enabling charge transport. This work uncovers new research directions for nanoelectronics, electrochemistry, and photocatalysis.
Hydrodynamic Impedance of Bacteria and Bacteria‐Inspired Micro‐Swimmers: A New Strategy to Predict Power Consumption of Swimming Micro‐Robots for Real‐Time Applications
Authors: Tabak Ahmet Fatih
Published: March 2018

Power supply is one of the key issues with bio‐inspired micro‐robots for therapeutic applications. There have been different approaches to predict the hydrodynamic behavior of such systems, most of which are based on the low‐Reynolds‐number approximation of the surrounding flow field, also known as the Stokes flow. However, it has been long debated that the Stokes‐flow approach without corrections for hydrodynamic interactions is inadequate in explaining the dynamics of a particle, even a blunt sphere, following a non‐trivial path subject to spatial and temporal variations. A cargo being towed by a rotating helical tail presents an even more complicated problem which can only be appreciated by numerical solutions of time‐dependent Navier–Stokes equations incorporated with rigid‐body dynamics. In this study, such a solution scheme is presented for the six degrees of freedom motion of both bacteria and bacteria‐inspired micro‐robots, swimming in backward or forward direction. Furthermore, the analysis is extended to characterize the impedance coefficients via parameterized wave geometry. Thus, it is demonstrated that the resistive force theory can be improved to predict time‐dependent fluid resistance acting on bio‐inspired micro‐swimmers via hydrodynamic impedance‐based corrections, allowing accurate calculation of required power to achieve desired actuation strategies.
Dynamics and structure development for biaxial stretching PA6/MXD6 blend packaging films
Authors: Kanai Toshitaka , Okuyama Yoshimune , Takashige Masao
Published: March 2018

The biaxial stretching film of polyamide 6 (PA6) is widely used for food and industrial products packaging, because it has good physical properties, such as high toughness and gas barrier properties. It is expected to improve gas barrier and easy straight cut performance for a larger market such as food packaging. So, in this research, blends of poly(m‐xylene adipamide) (MXD6) to PA6 which are immiscible were investigated in terms of dynamics and structure development for biaxial stretching films. For this reason, the higher order structure and stretching behaviors of the blends were studied. As a result, blends of MXD6 to PA6 which had cylindrical structures improved the properties of easy straight cut and high barrier, but did not have good stretchability and film thickness uniformity. For these reasons, they were studied to develop the biaxial stretching film of polyamide which improved stretchability and film thickness uniformity. Furthermore, blend effects of MXD6 to PA6 and dynamics analyses were investigated.
Influence of wheat, rye, and triticale straw on the properties of natural rubber composites
Authors: Masłowski Marcin , Miedzianowska Justyna , Strzelec Krzysztof
Published: March 2018

The article presents unreported yet in the subject literature results of the research that aim was the examinations of the effect of wheat, rye, and triticale straws obtained from three different fragmentation methods, on the properties of natural rubber composites. Sieve analysis was performed to produce composites with variable filler size fractions. Characterization of mechanical and damping properties, tear strength, hardness, thermo‐oxidative aging performance, and cross‐linking density of obtained biocomposites were reported and studied. It was found that straw fillers with different particle size and shape significantly affected properties of natural rubber composites. The addition of filler (in an appropriate amount and degree of fragmentation) modified natural rubber biocomposites, improving mechanical and physical properties of composites or the ability to damp under the influence of compression stress.
Dynamics and structure development for biaxial stretching polyamide 6 films
Authors: Kanai Toshitaka , Okuyama Yoshimune , Takashige Masao
Published: March 2018

The biaxial stretching film of polyamide 6 (PA6) is widely used for food and industrial products packaging. It is expected to improve stretchability, impact strength, tensile strength, and thermoformability for a larger market. So, in this research, the stretching methods were investigated in terms of dynamics and structure development for the biaxial stretching films. There are three different stretching methods which can produce PA6 films, namely the simultaneous biaxial stretching, the sequential biaxial stretching, and the double bubble tubular process. The physical properties of PA6 film are very much influenced by the biaxial stretching process. But there are no reports which described the difference among the three stretching methods and film properties. For this reason, the higher order structure and stretching behaviors of the three stretching methods were studied. As a result, the sequential biaxial stretching showed strong stretched effect and molecular orientation in the transverse direction (TD) and poor film thickness uniformity, because the strong hydrogen bonds were created during the machine direction (MD) stretching and high stretching stress in the TD stretching was required. In the simultaneous biaxial stretching, the molecular orientation was equal both in the MD and in the TD of the stretched plane. The double bubble tubular process produced well‐balanced film and equal orientation in any direction in terms of the phase difference in the plane of film. The biaxially oriented PA6 film having good stretchability and high physical properties was also investigated.
An Efficient Synthesis of exo/endo‐Hydroxylated Cyclohexenones by Thiol/Amine‐Mediated Tandem Aldol–[2,3]‐Sigmatropic Rearrangement: Amine‐Dependent Complementary Regioselectivity
Authors: Miura Motofumi , Nakakita Toshinori , Toriyama Masaharu , Motohashi Shigeyasu
Published: March 2018

exo/endo‐Hydroxylated cyclohexenones are essential synthetic intermediates for a variety of biologically active compounds. However, methods that lead to efficient and selective preparation of exo/endo‐hydroxylated cyclohexenones remain to be established. Herein, we report the practical and scalable synthesis of exo/endo‐hydroxylated cyclohexenones from readily available 2,6‐diketosulfoxides. We demonstrate that endo and exo geometric isomers of hydroxylated cyclohexenones can be obtained by simple modification of the reaction conditions.
Kohlenstoff‐Nanozyme: Enzymatische Eigenschaften, Katalysemechanismen und Anwendungen
Authors: Sun Hanjun , Zhou Ya , Ren Jinsong , Qu Xiaogang
Published: March 2018

Nanozyme haben spezifische Vorteile gegenüber natürlichen Enzymen, wie ihre einfache Produktion in großen Mengen, lange Lagerzeiten, niedrige Kosten und hohe Stabilität unter harschen Umgebungen. Kohlenstoffnanomaterialien (CNMs), einschließlich Fullerenen, Kohlenstoffnanoröhren, Graphen, Kohlenstoffquantenpunkten und Graphenquantenpunkten, sind zu einer herausragenden Substanzfamilie in den Materialwissenschaften geworden. Über die katalytischen Aktivitäten von CNMs und ihren Hybridverbindungen als eine neue Klasse von Nanozymen wurde ausführlich berichtet. In diesem Kurzaufsatz werden die jüngsten Fortschritte bei CNM‐basierten künstlichen Enzymen zusammengefasst, mit einem Schwerpunkt auf ihrer Peroxidase‐artigen Aktivität. Die enzymatischen Eigenschaften, Katalysemechanismen und neuartige Anwendungen von CNM‐Nanozymen in der Sensorik, der Therapie und der Umwelttechnologie werden diskutiert. Darüber hinaus thematisieren wir die verbleibenden Herausforderungen und ungelöste Probleme. Einhergehend mit dem raschen Voranschreiten der Bionanotechnologie haben die einzigartigen enzymatischen Eigenschaften der CNM‐Nanozyme viel Aufmerksamkeit erfahren, und sie werden auch in Zukunft ein aktives Forschungsfeld darstellen.
Optimization of biodegradable PEG/PLGA nanofiber mats electrospinning process for anti‐adhesion application
Authors: Zhao Yue , Zhu Jinhui , Zhang Junhui , Chen Zaomei , Li Weida , Deng Lejun , Chen Kejun , Wan Huayin , Li Jian , Li Rubing
Published: March 2018

Electrospinning is a direct, continuous, and useful technique to prepare nanofiber by applying electrostatic forces. In this study, poly(lactic‐co‐glycolic acid)/poly(ethylene glycol) (PLGA/PEG) nanofiber mats were prepared, and electrospinning process was optimized to obtain appropriate fiber diameter and hydrophilicity for anti‐adhesion application. Optimization of applied voltage, PEG content, and feeding rate was investigated using response surface methodology. A total of 15 trials were designed to optimize the parameters. Fiber diameter was measured using scanning electron microscopy. Individual and interactive effects of the solution properties were determined. Moreover, the adequacy of the models was verified by validation experiments. For anti‐adhesion test, a nanofiber mat was produced based on the suggested optimum electrospinning conditions. Results showed that optimum fiber diameters were obtained using 7.5% PEG content, applied voltage of 19 kV, and flow rate of 3 mL/h. Experimental results were in good agreement with the predicted fiber diameters. Furthermore, a rat model of sidewall defect‐cecum abrasion was employed to investigate the efficacy of PEG/PLGA in preventing postoperative peritoneal adhesions. Hence, this study provides an overview on the fabrication of PLGA/PEG nanofibers with targeted diameter, which may be used in anti‐adhesion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46282.