bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterizing the Distribution of Temperature and Normal Stress on Flash Heated Granite Surfaces at Seismic Slip Rates
Authors: Barbery M. R. , Chester F. M. , Chester J. S. 
Published: May 2021

AbstractAt seismic slip rates, flash‐weakening can significantly reduce the coefficient of friction, and the magnitude of weakening increases with surface temperature. To quantify the distribution of flash temperature, high‐speed double‐direct shear experiments were conducted on Westerly granite blocks using velocity steps from 1 mm/s to 900 mm/s at 9 MPa normal stress. We employed a high‐speed infrared camera to measure surface temperatures on the moving block during sliding, and utilized a novel sliding‐surface geometry to control the mm‐scale contact history. Following the initial weakening upon the velocity step, the blocks slide at a constant coefficient of friction. Surface temperatures are inhomogeneously distributed across the sliding surface, and increase with displacement. To determine the local normal stress distribution at the mm‐scale, we combine a one‐dimensional thermal model with conventional flash‐weakening models that incorporate a surface temperature‐dependence informed by the controlled, mm‐scale contact history. Early contacts experience local normal stress exceeding 40 times the applied normal stress. As sliding progresses, the local normal stress at the hottest contacts decreases as contact area increases, leading to local normal stresses ranging from 2 to 6 times the applied normal stress on most contacts by 30 mm of slip. Increases in surface temperature, which would decrease the coefficient of friction, are buffered by wear processes that increase contact area and decrease the local normal stress. Treatments of flash heating are advanced by incorporating improved characterization of the state of the sliding surface at the mm and larger scales during sliding.
Petrogenesis of Basaltic Lavas From the West Pacific Seamount Province: Geochemical and Sr‐Nd‐Pb‐Hf Isotopic Constraints
Authors: Yan Quanshu , Milan Luke , Saunders J. Edward , Shi Xuefa 
Published: May 2021

AbstractIn this study, we report new major and trace element, Sr‐Nd‐Pb‐Hf isotopic compositions and Ar‐Ar ages for basaltic lavas from seven poorly studied seamounts/guyots in the Western Pacific Seamount Province (WPSP). A review of new and published Ar‐Ar ages for seamounts/guyots confirm no linear age progression, as would be expected if these seamounts were produced by the Pacific Plate moving over a stationary mantle plume. These samples exhibit an alkalic character and can be produced by small‐degree partial melting of garnet pyroxenite with CO2. Their isotopic data identify four mantle end‐members (DMM, EMI, EMII, and HIMU) in the WPSP source region. These results confirm previous studies that invoke multiple contemporaneous plumelets in the region and a heterogeneous upper mantle reservoir which has been overprinted by multiple discrete hotspots, which create an anomalous and heterogeneous upper mantle because of mixing/overlapping EMI, EMII, and HIMU tracks, and age progressive volcanism is totally obscured. We propose a model where relict fragments of enriched mantle with distinct isotopic compositions residing in the upper mantle were a product of the formation of the adjacent large oceanic plateaus. These events introduce heterogeneity in the depleted mantle. The infiltration and metasomatism of these relict enriched components by carbonatitic fluids from the low‐velocity zone, create a source that then underwent small degrees of decompressional melting. The partial melts exploited pre‐existing lithospheric faults as an upwelling conduit and the resultant seafloor lava flows have obscured evidence to those pre‐existing lithospheric faults.
Long‐Term Trend of Equatorial Atlantic Zonal Sea Surface Temperature Gradient Linked to the Tropical Pacific Cold Tongue Mode Under Global Warming
Authors: Li Yang , Chen Quanliang , Xing Nan , Cheng Zhigang , Qi Yulei , Feng Fan , Li Minggang 
Published: May 2021

AbstractThe equatorial Atlantic zonal sea surface temperature (SST) gradient, which has significant climatic and biogeochemical effects, is closely associated with the equatorial Pacific zonal SST gradient through Walker circulation on seasonal and interannual time scales. However, discrepancies in current SST data sets mean that its long‐term trend is not well understood. Here, using multiple data sets, we find a robust weakening long‐term trend (i.e., greater warming in the east than west) in the equatorial Atlantic zonal SST gradient over the period 1900–2010 in all data sets. We also find that this weakening trend is closely linked to the tropical Pacific cold tongue mode (CTM), which corresponds to a strong increasing long‐term trend of zonal SST gradient along the equatorial Pacific (i.e., warming in the west and cooling in the east). Specifically, the long‐term cooling SST anomalies associated with the CTM modify the Walker circulation, and leads to weaker trade winds over the western equatorial Atlantic. These in turn deepen the thermocline in the eastern equatorial Atlantic, and cause the weakening long‐term trend of SST gradient along the equatorial Atlantic. The long‐term trend of the CTM is induced by ocean dynamical feedback in response to global warming, suggesting that global warming could affect the equatorial Atlantic zonal SST gradient via the CTM. Our results provide a novel explanation of the linkages between the long‐term trend of equatorial Atlantic zonal SST gradient and the CTM under global warming, which carries important implications for the relationship between global warming and the equatorial Atlantic zonal SST gradient.
In Search of the Optimal Atmospheric River Index for US Precipitation: A Multifactorial Analysis
Authors: Zhang Chen , Tung Wen‐wen , Cleveland William S. 
Published: May 2021

AbstractAtmospheric rivers (ARs) affect surface hydrometeorology in the US West Coast and Midwest. We systematically sought optimal AR indices for expressing surface precipitation impacts within the Atmospheric River Tracking Method Intercomparison Project (ARTMIP) framework. We adopted a multifactorial approach. Four factors, moisture fields, climatological thresholds, shape criteria, and temporal thresholds, collectively generated 81 West Coast AR indices and 81 Midwest indices from January 1980 to June 2017. Two moisture fields were extracted from the MERRA‐2 data for ARTMIP: integrated water vapor transport (IVT) and integrated water vapor (IWV). Metrics for precipitation effects included two‐way summary statistics, relating the concurrence of AR and that of precipitation, per event averaged precipitation rate, and per event precipitation accumulation. We found that an optimal AR index for precipitation depends on the types of impact to be addressed, associated physical mechanisms in the affected regions, timing, and duration. In West Coast and Midwest, IWV‐based AR indices identified the most abundant AR event time steps, most accurately associated AR to days with precipitation, and represented the presence of precipitation the best. With a lower climatological threshold, they detected the most accumulated precipitation with the longest event duration. Longer duration thresholds also led to higher accumulated precipitation, holding other factors constant. IWV‐based indices are the overall choice for Midwest ARs under varying seasonal precipitation drivers. IVT‐based indices suitably capture the accumulation of intense orographic precipitation on the West Coast. Indices combining IVT and IWV identify the fewest, shortest, but most intense AR precipitation episodes.
Oversampling Reflectivity Observations From a Geostationary Precipitation Radar Satellite: Impact on Typhoon Forecasts Within a Perfect Model OSSE Framework
Authors: Taylor James , Okazaki Atsushi , Honda Takumi , Kotsuki Shunji , Yamaji Moeka , Kubota Takuji , Oki Riko , Iguchi Toshio , Miyoshi Takemasa 
Published: May 2021

AbstractFor the past two decades, precipitation radars (PR) onboard low‐orbiting satellites such as Tropical Rainfall Measuring Mission (TRMM) have provided invaluable insight into global precipitation variability and led to advancements in numerical weather prediction through data assimilation. Building upon this success, planning has begun on the next generation of satellite‐based PR instruments, with the consideration for a future geostationary‐based PR (GPR), bringing the advantage of higher observation frequency over previous and current PR satellites. Following the successful demonstration by a recent study to test the feasibility of a GPR to obtain three‐dimensional precipitation data, this study takes the first step to investigate the potential usefulness of GPR observations for numerical weather prediction by performing a perfect model observing system simulation experiment (OSSE) for a West Pacific tropical cyclone (TC). Data assimilation experiments are performed assimilating reflectivity observations obtained for a range of beam sampling spans, following a previous finding that oversampling improves observation quality. Results showed observations obtained with finer sampling spans of 5 km and 10 km were able to better capture key tropical cyclone features in analyses, including the eye, heavy rainfall associated with the eyewall, and outer convective rainbands. Results also showed that through increased moistening and upward velocity within the inner storm environment, assimilation of observations drove an intensification of the secondary circulation and deepening of the storm, leading to an improvement in TC intensity error. Intensity forecasts were found improved for assimilation of observations obtained with increasingly finer beam sampling span, suggesting an important benefit of oversampling.
Improved Constraints on Global Methane Emissions and Sinks Using δ13C‐CH4
Authors: Lan X. , Basu S. , Schwietzke S. , Bruhwiler L. M. P. , Dlugokencky E. J. , Michel S. E. , Sherwood O. A. , Tans P. P. , Thoning K. , Etiope G. , Zhuang Q. , Liu L. , Oh Y. , Miller J. B. , Pétron G. , Vaughn B. H. , Crippa M. 
Published: May 2021

AbstractWe study the drivers behind the global atmospheric methane (CH4) increase observed after 2006. Candidate emission and sink scenarios are constructed based on proposed hypotheses in the literature. These scenarios are simulated in the TM5 tracer transport model for 1984–2016 to produce three‐dimensional fields of CH4 and δ13C‐CH4, which are compared with observations to test the competing hypotheses in the literature in one common model framework. We find that the fossil fuel (FF) CH4 emission trend from the Emissions Database for Global Atmospheric Research 4.3.2 inventory does not agree with observed δ13C‐CH4. Increased FF CH4 emissions are unlikely to be the dominant driver for the post‐2006 global CH4 increase despite the possibility for a small FF emission increase. We also find that a significant decrease in the abundance of hydroxyl radicals (OH) cannot explain the post‐2006 global CH4 increase since it does not track the observed decrease in global mean δ13C‐CH4. Different CH4 sinks have different fractionation factors for δ13C‐CH4, thus we can investigate the uncertainty introduced by the reaction of CH4 with tropospheric chlorine (Cl), a CH4 sink whose abundance, spatial distribution, and temporal changes remain uncertain. Our results show that including or excluding tropospheric Cl as a 13 Tg/year CH4 sink in our model changes the magnitude of estimated fossil emissions by ∼20%. We also found that by using different wetland emissions based on a static versus a dynamic wetland area map, the partitioning between FF and microbial sources differs by 20 Tg/year, ∼12% of estimated fossil emissions.
Quadruple Collocation Analysis of In‐Situ, Scatterometer, and NWP Winds
Authors: Vogelzang Jur , Stoffelen Ad 
Published: May 2021

AbstractTriple collocation is an established technique for retrieving linear calibration coefficients and observation error variances of a physical quantity observed simultaneously by three different observation systems. The formalism is extended to an arbitrary number of systems, and representativeness errors and associated cross‐covariances are included in a natural way. It is applied to quadruple collocations of ocean surface vector winds from two scatterometers (ASCAT‐A, ASCAT‐B, or ScatSat), buoy measurements, and NWP model forecasts. There are 15 possible sets of quadruple collocation equations, 12 of which are solvable for the essential variables (calibration coefficients, observation error variances, and common variance) as well as two additional error covariances, each set leading to a different solution. The quadruple collocation equations by themselves give little information on the representativeness errors involved; these have to be estimated using other methods. The spreading in the solutions is a measure of the accuracy of the underlying error model. Variation of the scale at which the spatial variances are evaluated yields an optimal scale of 100–200 km. From triple collocation subsets the error in the scatterometer error standard deviations is found to be 0.03–0.05 m s−1, more than expected on statistical grounds. A more precise determination requires an error model that better describes the data error properties.
Strong Local Evaporative Cooling Over Land Due to Atmospheric Aerosols
Authors: Chakraborty TC , Lee Xuhui , Lawrence David M. 
Published: May 2021

AbstractAerosols can enhance terrestrial productivity through increased absorption of solar radiation by the shaded portion of the plant canopy—the diffuse radiation fertilization effect. Although this process can, in principle, alter surface evaporation due to the coupling between plant water loss and carbon uptake, with the potential to change the surface temperature, aerosol‐climate interactions have been traditionally viewed in light of the radiative effects within the atmosphere. Here, we develop a modeling framework that combines global atmosphere and land model simulations with a conceptual diagnostic tool to investigate these interactions from a surface energy budget perspective. Aerosols increase the terrestrial evaporative fraction, or the portion of net incoming energy consumed by evaporation, by over 4% globally and as much as ∼40% regionally. The main mechanism for this is the increase in energy allocation from sensible to latent heat due to global dimming (reduction in global shortwave radiation) and slightly augmented by diffuse radiation fertilization. In regions with moderately dense vegetation (leaf area index >2), the local surface cooling response to aerosols is dominated by this evaporative pathway, not the reduction in incident radiation. Diffuse radiation fertilization alone has a stronger impact on gross primary productivity (+2.18 Pg C y−1 or +1.8%) than on land evaporation (+0.18 W m−2 or +0.48%) and surface temperature (−0.01 K). Our results suggest that it is important for land surface models to distinguish between quantity (change in total magnitude) and quality (change in diffuse fraction) of radiative forcing for properly simulating surface climate.
Salvage HLA-haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide for graft failure in non-malignant disorders
Authors: Albert Michael H. , Sirin Mehtap , Hoenig Manfred , Hauck Fabian , Schuetz Catharina , Bhattacharyya Rajat , Stepensky Polina , Jacoby Elad , Güngör Tayfun , Beier Rita , Schulz Ansgar 
Published: May 2021

AbstractGraft failure requires urgent salvage HSCT, but there is no universally accepted approach for this situation. We investigated T-cell replete haploidentical HSCT with post-transplantation cyclophosphamide following serotherapy-based, radiation-free, reduced intensity conditioning in children with non-malignant disorders who had rejected their primary graft. Twelve patients with primary or secondary graft failure received T-cell replete bone marrow grafts from haploidentical donors and post-transplantation cyclophosphamide. The recommended conditioning regimen comprised rituximab 375 mg/m2, alemtuzumab 0.4 mg/kg, fludarabine 150 mg/m2, treosulfan 20–24 g/m2 and cyclophosphamide 29 mg/kg. After a median follow-up of 26 months (7–95), eleven of twelve patients (92%) are alive and well with complete donor chimerism in ten. Neutrophil and platelet engraftment were observed in all patients after a median of 18 days (15–61) and 39 days (15–191), respectively. Acute GVHD grade I was observed in 1/12 patients (8%) and mild chronic GVHD in 1/12 patients (8%). Viral reactivations and disease were frequent complications at 75% and 42%, respectively, but no death from infectious causes occurred. In summary, this retrospective analysis demonstrates that a post-transplantation cyclophosphamide-based HLA-haploidentical salvage HSCT after irradiation-free conditioning results in excellent engraftment and overall survival in children with non-malignant diseases.
A method for utilizing automated machine learning for histopathological classification of testis based on Johnsen scores
Authors: Ito Yurika , Unagami Mami , Yamabe Fumito , Mitsui Yozo , Nakajima Koichi , Nagao Koichi , Kobayashi Hideyuki 
Published: May 2021

AbstractWe examined whether a tool for determining Johnsen scores automatically using artificial intelligence (AI) could be used in place of traditional Johnsen scoring to support pathologists’ evaluations. Average precision, precision, and recall were assessed by the Google Cloud AutoML Vision platform. We obtained testicular tissues for 275 patients and were able to use haematoxylin and eosin (H&E)-stained glass microscope slides from 264 patients. In addition, we cut out of parts of the histopathology images (5.0 × 5.0 cm) for expansion of Johnsen’s characteristic areas with seminiferous tubules. We defined four labels: Johnsen score 1–3, 4–5, 6–7, and 8–10 to distinguish Johnsen scores in clinical practice. All images were uploaded to the Google Cloud AutoML Vision platform. We obtained a dataset of 7155 images at magnification 400× and a dataset of 9822 expansion images for the 5.0 × 5.0 cm cutouts. For the 400× magnification image dataset, the average precision (positive predictive value) of the algorithm was 82.6%, precision was 80.31%, and recall was 60.96%. For the expansion image dataset (5.0 × 5.0 cm), the average precision was 99.5%, precision was 96.29%, and recall was 96.23%. This is the first report of an AI-based algorithm for predicting Johnsen scores.
Comparative study for machine learning classifier recommendation to predict political affiliation based on online reviews
Authors: Ullah Hayat , Ahmad Bashir , Sana Iqra , Sattar Anum , Khan Aurangzeb , Akbar Saima , Asghar Muhammad Zubair 
Published: May 2021

AbstractIn the current era of social media, different platforms such as Twitter and Facebook have frequently been used by leaders and the followers of political parties to participate in political events, campaigns, and elections. The acquisition, analysis, and presentation of such content have received considerable attention from opinion‐mining researchers. For this purpose, different supervised and unsupervised techniques have been used. However, they have produced less efficient results, which need to be improved by incorporating additional classifiers with the extended data sets. The authors investigate different supervised machine learning classifiers for classifying the political affiliations of users. For this purpose, a data set of political reviews is acquired from Twitter and annotated with different polarity classes. After pre‐processing, different machine learning classifiers like K‐nearest neighbor, naïve Bayes, support vector machine, extreme gradient boosting, and others, are applied. Experimental results illustrate that support vector machine and extreme gradient boosting have shown promising results for predicting political affiliations.
Beamforming design for MIMO full‐duplex SWIPT IoT system under imperfect CSI
Authors: Liu Dan , Zhong Ling , Xu Zhiguo , Wen Zhigang , Zou Junwei 
Published: May 2021

AbstractThis paper proposes a multiple‐input multiple‐output full‐duplex relay Internet of Things system under imperfect channel state information, where the relay uses time switching relaying protocol to harvest energy. Particularly, due to the uncertainty channel circumstance, the self‐interference in full‐duplex relay cannot be eliminated completely. For such a system, a joint source‐relay beamforming optimization problem which maximizes the system achievable rate subject to the transmit power and harvested energy constraints is studied. In light of the intractability of the problem, a singular value decomposition based geometric programming algorithm is investigated. The considered problem is reformulated to a diagonalized form by using singular value decomposition method. Then, the geometric programming algorithm is adopted to obtain the optimal solution for the reformulated problem. Numerical results validate the effectiveness and superiority of the proposed optimization scheme.
Inter‐numerology interference in OFDM‐IM systems
Authors: Dogan‐Tusha Seda , Tusha Armed , Basar Ertugrul , Althunibat Saud , Qaraqe Khalid , Arslan Hüseyin 
Published: May 2021

AbstractIn 5G and beyond communication systems, distinct numerologies can coexist to serve diverse requirements for users and applications. However, the inter‐numerology interference (INI) is a main challenge that significantly impacts the system performance. Therefore, the performance under INI has become an essential evaluation metric for the suitability of the different transmission schemes in the future communication systems. This paper analyzes the impact of INI on the performance of orthogonal frequency division multiplexing with index modulation (OFDM‐IM) systems. Specifically, an analytical expression of the INI level in OFDM‐IM systems is presented as a function of the subcarrier activation ratio (SAR) and subcarrier activation probability (SAP). Furthermore, aiming at reducing the INI level, an adaptive subcarrier mapping scheme (SMS) is proposed based on the conventional combinatorial mapping scheme. Moreover, analysis and evaluation of SAR and SAP are performed regarding the requirements of 5G and beyond services. It is proved that the INI level in OFDM‐IM systems is highly dependent not only on the number of active subcarriers but also on their position in an OFDM block.
Design and realization of ultra‐wideband absorber from C to K band
Authors: Li Yi , Xiang Zheng , Ren Peng , Feng Lijing 
Published: May 2021

AbstractHere, a novel design of absorber loading dual‐layer frequency selective surfaces (FSSs) in the Salisbury screen is proposed. The design of frequency selective surfaces is mainly composed of cross‐dipole and dual‐loop metal patch. Simulation results show that this absorbing structure can achieve ultra‐wideband absorption from C band to K band and the fractional bandwidth reaches 117.1% below –10 dB. The thickness of the proposed absorbing structure is 0.078 λL and the unit cell size is 0.262 λL, where λL is the wavelength of the lowest absorbing frequency. Moreover, it shows excellent polarization stability in TE and TM modes, and it has great angular stability. Finally, the prototype of this structure is fabricated, and the measured results are in good agreement with the simulation results.