bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diagenetic impacts on hydraulic flow unit properties: insight from the Jurassic carbonate Upper Arab Formation in the Persian Gulf
Authors: Sharifi-Yazdi Masoud , Rahimpour-Bonab Hossain , Nazemi Maziyar , Tavakoli Vahid , Gharechelou Sajjad 
Published: April 2020

AbstractThe Upper Arab reservoir in the central Persian Gulf was examined for depositional, diagenetic, sequence stratigraphic and petrophysical features. This succession is composed of eight sedimentary facies that deposited on a carbonate ramp. Three-third-order sequences prograded across the Late Jurassic Arab Platform. This interval was complicated by multiple diagenetic phases including eogenesis and mesogenesis that strongly influenced reservoir properties. Dolomitization, dissolution, cementation and compaction are major diagenetic processes which played an essential role in increasing or decreasing reservoir quality. Four hydraulic flow units (HFU) were determined by flow zone indicator approach for evaluation of the reservoir quality. In addition to depositional features, diagenetic alterations have changed general HFUs characterizations such as porosity, permeability and pore-throat size. Likewise, via Lucia classification, HFUs of the Arab reservoir were grouped based on the integration of geological and petrophysical attributes in detail. Among diagenetic processes, dolomitization and dissolution have positive effects while cementation and stylolitization have a negative effect on HFUs characteristics in the studied reservoir. Put another way, since diagenetic alterations lead to the intensification of heterogeneity in carbonate reservoir, prediction of the relationship between pore type and pore throat size is a problematic issue. Recognition of the hydraulic flow units considered as a practical tool for grouping reservoir rocks and characterizing heterogeneity using porosity and permeability relationship. Finally, specifying of the contribution of various diagenetic imprints in each hydraulic flow unit in a sequence stratigraphic framework results in a conceptual reservoir model that could predict reservoir quality variations across the field.
Investigation of adsorption mechanism of phosphate(V) ions on the nanostructured Na-A zeolite surface modified with ionic polyacrylamide with regard to their removal from aqueous solution
Authors: Wiśniewska Małgorzata , Urban Teresa , Chibowski Stanisław , Fijałkowska Gracja , Medykowska Magdalena , Nosal-Wiercińska Agnieszka , Franus Wojciech , Panek Rafał , Szewczuk-Karpisz Katarzyna 
Published: April 2020

AbstractThe sorption properties of Na-A-type synthetic zeolite, obtained from fly ash with regard to the phosphate(V) ions, were determined. The Na-A zeolite was prepared using hydrothermal conversion of fly ash with aqueous sodium hydroxide. The effects of solution pH and zeolite surface modification by ionic polyacrylamide (PAM) were examined. Both anionic and cationic forms of PAM were applied. The adsorption and electrokinetic data were obtained by means of spectrophotometric measurements, potentiometric titrations and zeta potential determination. It was shown that the presence of ionic polyacrylamide adsorption layers modifies the surface properties of the solid. The resulting composite material (zeolite/polymer) can be applied for effective removal of phosphate(V) ions from the liquid medium. Its regeneration possibilities are also considerable. Additionally, the use of fly ash for zeolite preparation leads to management of hazardous waste material.
Skull base chordomas review of current treatment paradigms
Authors: Yaniv Dan , Soudry Ethan , Strenov Yulia , Cohen Marc A. , Mizrachi Aviram 
Published: April 2020

BackgroundChordomas are locally invasive neoplasms, arising from notochordal remnants and can appear anywhere along the axial skeleton. Local recurrences are common, and distant metastases may occur years after the initial presentation.MethodsLiterature review of current treatment strategies for chordomas of the skull base.ResultsSurgery is the mainstay of treatment and complete resection has paramount importance for prognosis.When complete resection is not achieved recurrent disease is common. The anatomical complexity of the skull base makes resection complex. Endonasal endoscopic approaches to the clivus has become increasingly favored in recent years although addressing reconstruction of the skull base to prevent CSF leak may be challenging.Evidence suggests that radiotherapy should not be considered as a primary single modality when trying to achieve cure of the disease. Nonetheless, immediate post‐operative radiotherapy improves survival. Many strategies have been suggested to preserve sensitive vital structures in the skull base during treatment but as for survival there is no evidence of advantage when comparing adjuvant therapy with photon radiotherapy, gamma knife surgery, proton beam therapy, and carbon ion radiation therapy.There is no evidence to support cytotoxic chemotherapy in the treatment of chordomas but targeted therapies have started to show promise. Several optional molecular targets exist. Brachyury is overexpressed in 95% of chordomas but not in other mesenchymal neoplasms. However, its precise role in chordoma pathogenesis is currently unclear, and its cellular location in the nucleus makes it difficult to target. The inhibition of brachyury in chordoma cell lines induces growth arrest and apoptosis. This does not have clinical application to date. There are retrospective results with different molecular targeted therapies for advanced chordomas with some effectiveness.ConclusionDespite improvements made in the past 10 years in our knowledge of chordoma biology, available therapies still offer a limited benefit. There is an unmet need for new therapeutic options for patients with advanced disease. Therefore, patients with advanced disease should be encouraged to participate in clinical trials when and where available.
Observed and CMIP5‐Simulated Radiative Flux Variability Over West Africa
Authors: Mackie Anna , Wild Martin , Brindley Helen , Folini Doris , Palmer Paul I. 
Published: April 2020

AbstractWe explore the ability of general circulation models in the Coupled Model Intercomparison Project (CMIP5) to recreate observed seasonal variability in top‐of‐the‐atmosphere and surface radiation fluxes over West Africa. This tests CMIP5 models' ability to describe the radiative energy partitioning, which is fundamental to our understanding of the current climate and its future changes. We use 15 years of the monthly Clouds and the Earth's Radiant Energy System Energy Balanced and Filled (EBAF) product, alongside other satellite, reanalysis, and surface station products. We find that the CMIP5 multimodel mean is generally within the reference product range, with annual mean CMIP5 multimodel mean—EBAF of −0.5 W m−2 for top‐of‐the‐atmosphere reflected shortwave radiation, and 4.6 W m−2 in outgoing longwave radiation over West Africa. However, the range in annual mean of the model seasonal cycles is large (37.2 and 34.0 W m−2 for reflected shortwave radiation and outgoing longwave radiation, respectively). We use seasonal and regional contrasts in all‐sky fluxes to infer that the representation of the West African monsoon in numerical models affects radiative energy partitioning. Using clear‐sky surface fluxes, we find that the models tend to have more downwelling shortwave and less downwelling longwave radiation than EBAF, consistent with past research. We find models that are drier and have lower aerosol loading tend to show the largest differences. We find evidence that aerosol variability has a larger effect in modulating downwelling shortwave radiation than water vapor in EBAF, while the opposite effect is seen in the majority of CMIP5 models.
Large‐Scale Dynamics and Moisture Sources of the Precipitation Over the Western Tibetan Plateau in Boreal Winter
Authors: Liu Xiaolin , Liu Yimin , Wang Xiaocong , Wu Guoxiong 
Published: April 2020

AbstractOne of the heaviest precipitations over the Asian continent in winter is located in the western Tibetan Plateau (TP). In this study, the dynamics of the precipitation over the western TP (PWTP) in boreal winter and its interannual variability are explored. The moisture origins and paths are detected using a Lagrangian Integrated Trajectory model. In climatology, the PWTP is generated as results of upward air motions on the windward side of the TP and ranges from 0.5 to 2.5 mm·day−1. Under the influence of midlatitude westerlies and the subtropical high over the Arabian Peninsula, three key moisture sources (by percentage contribution) are identified: South Asia‐North Indian Ocean (56.6%), Central Eurasia‐North Africa (37.7%), and Central‐North Atlantic (5.6%). The dominant precipitating cloud types are nimbostratus and stratus/stratocumulus derived from satellite data. On the interannual timescale, PWTP variation is closely associated with El Niño‐Southern Oscillation (ENSO) and midlatitude cyclones. ENSO warm events lead to an anomalous anticyclone over the tropical northwest Indian Ocean and intensify moisture transport northward in the lower troposphere, as well as abnormal divergence in upper troposphere. However, ENSO explains only about 38.1% of the PWTP variance. Midlatitude teleconnection also contributes to the PWTP variability, which is comparable to the effect of ENSO. The cyclones imbedded in the subtropical jet are part of the teleconnection, with an anticyclone upstream over the North Atlantic and an cyclone over the western TP. Further evidence suggests that the transient eddies in the North Atlantic help to maintain the teleconnection.
The Role of Vertically and Obliquely Propagating Gravity Waves in Influencing the Polar Summer Mesosphere
Authors: Thurairajah Brentha , Cullens Chihoko Yamashita , Siskind David E. , Hervig Mark E. , Bailey Scott M. 
Published: April 2020

AbstractUsing an 8‐year (2007–2014) data set from two different limb‐viewing instruments, we evaluate the relative roles of vertically versus obliquely propagating gravity waves (GWs) as sources of GWs in the polar summer mesosphere. Obliquely propagating waves are of interest because they are presumed to be generated by the summer monsoons. In the high‐latitude upper mesosphere, the correlation coefficient between the time series of ice water content (IWC) and GW amplitude is 0.48, indicating that the observed GWs enhance polar mesospheric clouds (PMCs). For vertically propagating waves, the correlation coefficient between IWC and stratospheric/lower mesospheric (20–70 km) GW amplitude at the same high latitudes becomes more negative with increasing altitude. This change in correlation from negative in the lower mesosphere to positive at PMC altitudes suggests the presence of another source of GWs. The positive correlation coefficient between the time series of IWC and GW amplitude from 0–50°N, 20–90 km shows a slanted structure suggesting oblique propagation. This slanted structure is more robust in some seasons compared to others, and this interannual variability may be due to the latitudinal gradient of the mesospheric easterly jet where steeper gradients allow for low‐latitude tropospheric GWs to be refracted to the high‐latitude mesosphere more efficiently. Gravity‐Wave Regional or Global Ray Tracer (GROGRAT) ray tracing simulations show that more GWs propagate obliquely compared to vertically propagating waves that reach PMC altitudes. For obliquely propagating waves, GROGRAT simulations indicate that nonorographic tropospheric GWs with faster phase speed (>20 m/s) and longer horizontal wavelength (>400 km) have a higher probability of reaching the polar summer mesosphere.
Resistance Formulations in Shallow Overland Flow Along a Hillslope Covered With Patchy Vegetation
Authors: Crompton Octavia , Katul Gabriel G. , Thompson Sally 
Published: April 2020

AbstractDescribing the effects of surface roughness on flow resistance remains a first‐order challenge for modeling shallow overland flow using the Saint Venant equations (SVE). This challenge has resulted in a proliferation of roughness schemes relating the properties of a uniform rough surface to bulk velocity and resistance, making selection of an appropriate roughness scheme daunting—especially on heterogeneous surfaces. For hydrological predictions, a roughness scheme is appropriate if the resulting SVE solutions predict outcomes such as water balance partitioning between runoff and infiltration, the hillslope hydrograph, and the discharge velocity with uncertainties that are less than or comparable to uncertainty in measurements. To assess the sensitivity of hydrological predictions to the choice of a roughness scheme, multiple schemes are first calibrated to each other under equilibrium flow conditions while imposing the kinematic wave approximation at the outlet. This approach yields analytical relations between the parameters of different roughness schemes when applied to the same hillslope and discharge. The approach is used to provide a parameterization of five commonly used roughness schemes for a common surface, and the predictions of the schemes for multiple patchily vegetated hillslopes are compared. The results suggest that, once calibrated, there is minimal prediction sensitivity to the choice of roughness scheme across a wide range of rainfall conditions. Operationally, the results demonstrate that parameterizing a roughness schemes is of higher significance for predicting hydrological patterns than the precise formulation employed.
Moderately compressed high‐swing class‐C/B VCO with accurate current control
Authors: Zhang G. 
Published: April 2020

A high‐swing class‐C/B VCO without tail current source has been proposed. Accurate current control and dynamic bias generation that are essential to robust start‐up and class‐C operation are achieved through mirroring VCO LDO current and comparing against bias current. The VCO oscillation amplitude is designed to be sufficiently large and the core transistors are compressed moderately, such that the oscillation amplitude is stable while the VCO operates in class‐C mode. A prototype PMOS VCO in a 0.13 μm process demonstrated a measured VCO figure of merit of 192 dB at 4.7 GHz with 1.4 mA current and core VDD at 0.6 V.
Mm‐wave single‐pole single‐throw m‐HEMT switch with low loss and high linearity
Authors: Kim Younghwan , Jeon Sanggeun 
Published: April 2020

This Letter presents a single‐pole single‐throw (SPST) switch for high‐power applications in the mm‐wave frequency band. A stacked‐FET structure is adopted in the shunt switching cell for reducing the insertion loss and improving the linearity of the switch. To enhance the isolation, the parasitic inductance of the stacked‐FET structure is resonated out by connecting a series capacitor. The number of stacked FETs in each shunt cell and the number of the shunt cells are optimised considering the trade‐off among the insertion loss, isolation, and linearity. The SPST switch is fabricated in a 70‐nm GaAs m‐HEMT process. The measurement shows that the insertion loss is <1.1 dB, and the isolation is >25 dB over the frequency from 59 to 77 GHz. Both the insertion loss and isolation are not compressed at all until the input power reaches 19.5 dBm at 75 GHz.
Availability modelling of terrestrial hybrid FSO/RF based on weather statistics from tropical region
Authors: Basahel Ahmed A. , Rafiqul Islam Md. , Habaebi Mohamed Hadi , Zabidi Suriza A. 
Published: April 2020

Free‐space optical (FSO) communication links are point‐to‐point wireless technologies. It provides high data rates up to a gigabit per second. FSO link availability is easily affected by different weather conditions. Radio‐frequency (RF) can be a complimentary link to the FSO link to increase availability. Hybrid FSO/RF is a feasible technology for providing high availability of point‐to‐point wireless links. In tropical regions, normally RF link is relatively sensitive to rain. Availability prediction of hybrid FSO/RF with the selection of suitable RF is indispensable, especially in tropical regions. In this study, empirical models are proposed to predict the link availability of RF, and hybrid FSO/RF over link ranges up to 5 km. The availability prediction models are based on the long‐term statistics of atmospheric attenuations from the tropical climate zone. The RF link availability prediction model is developed for frequency ranges from 10 to 100 GHz using the International Telecommunications Union‐Radio (ITU‐R) rain attenuation model. It is link distance, fade margin, and radio frequency dependent. The proposed availability models can predict carrier as well as enterprise class availability. The availabilities predicted by proposed models are found to be in good agreement with those estimated by the ITU‐R.
Carbon monoxide and carbon dioxide adsorption on alkali metal cation‐exchanged SSZ‐13 zeolites
Authors: Feng Jiawei , Hu Yunfeng , Bao Qiang , Liang Dan , Xu Ying 
Published: April 2020

In this work, chabazite SSZ‐13 samples with different cations were synthesised by hydrothermal method and thoroughly analysed using various characterisation techniques. The role of types of cations in CO2 and CO adsorption measurements was investigated. The adsorption isotherms were fitted by Langmuir, Langmuir‐Freundlich and Toth adsorption models, respectively. The result shows that the Langmuir‐Freundlich model is the most suitable for the adsorption isotherms of SSZ‐13 molecular sieves. The adsorption isotherms of the fitted CO2 and CO were analysed to study the high silicon SSZ‐13 samples of alkali metal cations Li+, Na+, K+ and Cs+ for ion exchange. The result shows that Na+ has the highest adsorption capacity, but the adsorption selectivity is extremely low. K+ has the lowest adsorption capacity, but it has excellent adsorption selectivity, which may be attributed to its large cation radius and the special position of cations in CHA skeleton structure, resulting in the formation of ‘molecular trapdoor’ effect. In addition, Cs+ has a larger ionic radius than K+, but the adsorption selectivity is not significantly improved, similar to Li+. It can be determined that the ‘molecular trapdoor’ effect has a significant relationship with the position of cations in the framework.
Electromagnetic induction heating as a driver of volcanic activity on massive rocky planets
Authors: Kislyakova Kristina , Noack Lena 
Published: April 2020

Aims. We investigate possible driving mechanisms of volcanic activity on rocky super-Earths with masses exceeding 3–4 M⊕. Due to high gravity and pressures in the mantles of these planets, melting in deep mantle layers can be suppressed, even if the energy release due to tidal heating and radioactive decay is substantial. Here we investigate whether a newly identified heating mechanism, namely induction heating by the star’s magnetic field, can drive volcanic activity on these planets due to its unique heating pattern in the very upper part of the mantle. In this region the pressure is not yet high enough to preclude the melt formation.
Methods. Using the super-Earth HD 3167b as an example, we calculate induction heating in the planet’s interiors assuming an electrical conductivity profile typical of a hot rocky planet and a moderate stellar magnetic field typical of an old inactive star. Then we use a mantle convection code (CHIC) to simulate the evolution of volcanic outgassing with time.
Results. We show that although in most cases volcanic outgassing on HD 3167b is not very significant in the absence of induction heating, including this heating mechanism changes the picture and leads to a substantial increase in the outgassing from the planet’s mantle. This result shows that induction heating combined with a high surface temperature is capable of driving volcanism on massive super-Earths, which has important observational implications.
Fast degradation of the circular flare ribbon on 2014 August 24
Authors: Zhang Q. M. , Yang S. H. , Li T. , Hou Y. J. , Li Y. 
Published: April 2020

Context. The separation and elongation motions of solar flare ribbons have extensively been investigated. The degradation and disappearance of ribbons have rarely been explored.
Aims. We report our multiwavelength observations of a C5.5 circular-ribbon flare associated with two jets (jet1 and jet2) on 2014 August 24, focusing on the fast degradation of the outer circular ribbon (CR).
Methods. The flare was observed in ultraviolet (UV) and extreme-ultraviolet (EUV) wavelengths by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory spacecraft. Soft X-ray fluxes of the flare in 0.5−4 and 1−8 Å were recorded by the GOES spacecraft.
Results. The flare, consisting of a short inner ribbon (IR) and outer CR, was triggered by the eruption of a minifilament. The brightness of IR and outer CR reached their maxima simultaneously at ∼04:58 UT in all AIA wavelengths. Subsequently, the short eastern part of the CR faded out quickly in 1600 Å but only gradually in EUV wavelengths. The long western part of the CR degraded in the counterclockwise direction and decelerated. The degradation was distinctly divided into two phases: phase I with faster apparent speeds (58−69 km s−1), and phase II with slower apparent speeds (29−35 km s−1). The second phase stopped at ∼05:10 UT when the western CR disappeared entirely. In addition to the outward propagation of jet1, the jet spire experienced untwisting motion in the counterclockwise direction during 04:55−05:00 UT.
Conclusions. We conclude that the event can be explained by the breakout jet model. The coherent brightenings of the IR and CR at ∼04:58 UT may result from the impulsive interchange reconnection near the null point, whereas sub-Alfvénic slipping motion of the western CR in the counterclockwise direction indicates the occurrence of slipping magnetic reconnection. Another possible explanation of the quick disappearance of the hot loops that are connected to the western CR is that they are simply reconnected sequentially without the need for significant slippage after the null-point reconnection.
Refraktive Hornhautchirurgie: Nachkorrekturen
Authors: Kook Daniel , Mayer Wolfgang J. , Shajari Mehdi , Steinwender Gernot , Kohnen Thomas 
Published: April 2020

ZusammenfassungIn den 30 Jahren seit Beginn der laserassistierten Hornhautchirurgie sind die Techniken zur Korrektur von Fehlsichtigkeiten weiterentwickelt und verbessert worden. Dennoch muss ein Teil der Patienten nachkorrigiert werden, u. a. wegen residualer Refraktionsfehler. Darüber soll im Folgenden berichtet werden.