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In this study, a new bridged bis(β-cyclodextrin) (CD) functionalized urea–formaldehyde monolithic column was prepared by “one-pot” method within 30 minutes. The structures of bridged-CD and the obtained monolithic column were characterized by scanning electron microscopy, nuclear magnetic resonance spectroscopy, infrared spectroscopy and energy dispersive spectroscopy. The chromatographic performance of native-CD-monolith, N,N′-methylenebisacrylamide (MBA)-bridged-CD-monolith and N,N′-(1,2-dihydroxyethylene) bisacrylamide (DAA)-bridged-CD-monolith was systematically evaluated by separating five analytes. As a result, all tested analytes were separated on an MBA-bridged-CD-monolith and DAA-bridged-CD-monolith with high resolutions (1.21–6.80), which showed that the bridged-CD-monolith exhibited a better chromatographic performance with enantioselectivity due to providing mixed-modes such as hydrophilicity, hydrogen bonding, ionic dipole and synergy compared with those of the native-CD-monolith. In addition, the enantioselectivity of the bridged-CD-monolith was related to the polarity of a functional linker. As a new chiral separation material, the bridged-CD functionalized urea–formaldehyde monolithic column may be widely applied in the analysis of chiral compounds due to its rapid preparation and higher enantioseparation performance.

In this study, a double-recognized aptamer-molecularly imprinted monolithic column (Apt-MIP monolithic column) was prepared by introducing both aptamer and MIP to reduce non-specific adsorption. Its preparation parameters such as the time of photo-initiation, the dosage of photo-initiator and the concentration of aptamer were investigated in detail. The recovery ratios of ochratoxin A (OTA) to ochratoxin B (OTB) on Apt-MIP monolithic column, Apt monolithic column and MIP monolithic column were 116.1, 40.8 and 69, respectively. Even if the concentration of OTB was 10 times that of OTA, the recovery of OTB was only about 2.9%. Applied to beer samples, the prepared Apt-MIP monolithic column drastically resisted background adsorption and the high-specificity recognition for OTA was obtained with the recoveries of 95.5-105.9%. This work provided a simple and effective method to selectively identify OTA from complex samples.

Ionospheric irregularities impair GNSS signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident for the high latitudes, which are currently gaining the attention of research and industry branches. These activities should be supported with reliable positioning and navigation services. Such needs motivate us to assess, for the first time, the impact of ionospheric irregularities on GNSS positioning performance in Greenland. We fill the gap and evaluate the performance of positioning methods that were not investigated comprehensively until now but meet the demands of a wide range of users. In this regard, we address the needs of mass-market users that most frequently employ single-frequency receivers and expect a meter to submeter-level accuracy in an absolute mode; and the users who require the highest precision solution based on geodetic-grade dual-frequency receivers. We take advantage of the datasets collected at the GNET permanent network in Greenland during three ionospheric storms, namely the St. Patrick storm of March 17, 2015, June 22, 2015, and August 25–­26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in RTK positioning. Next, assessing the single-frequency ionospheric-free PPP, we demonstrate that the model is generally unaffected by the ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we revealed that phase signals on the L2 frequency band are more prone to the cycle slips induced by ionospheric irregularities than those transmitted on the first one.

The objective of the work is to compare geomagnetic storm impact on the ionosphere parameters measured from ground-based GNSS permanent stations and Swarm satellites. The analyses compare the changes of vertical total electron content (VTEC) measured along the entire ionosphere cross-section to the variations of electron density (ED) on the orbit, at ~500 km altitude. The objective is how sensitive are the measures of electric field variations available on the Earth, with respect to those obtained from the satellite orbit. The study applies Swarm in-situ ED measured by Langmuir Probes (LP), topside TEC from onboard Swarm GNSS receivers and vertical TEC determined from ground-based GNSS stations available in the area of the Northern polar cap. Ground and satellite data were processed in different ways. Ground-based VTEC is available at number of stations providing heterogeneous but useful horizontal coverage. Therefore ROTI values were calculated from VTEC as gradient values capable to indicate the disturbances. These ROTI values were interpolated spatially to obtain maps. Swarm passes over the polar cap starting from 45° lasts for several minutes each, and repeat in this region approximately every 1.5 h. Such along-track collected small data samples are useless in horizontal correlation analysis. Therefore Swarm data disturbances, in this case, are extracted with the use of Fourier transform-based filtering and are also analyzed in the spectrograms based on short-term Fourier transform (STFT). The case study has used three geomagnetic storms, namely: the St. Patrick storm of March 17, 2015, the storm on June 22, 2015, and the storm on August 25-26, 2018. The results reveal differences in storm impact on VTEC measured by GNSS on the Earth, with respect to the storm influence on topside TEC and in-situ ED disturbances measured onboard the Swarm. The overall summary statistics provide some preliminary conclusions on different times of the reaction to the storm. Additionally, some interesting differences between FT filtering and a very popular moving average are shown, with respect to Swarm data. The research was done in the frame of the FORSWAR project (Forecasting Space Weather in the Arctic Region) funded by ESA.

Exosomes that carry large amounts of tumor-specific molecular information have been identified as a potential non-invasive biomarker for early warning of cancer. In this work, we reported an enzyme-assisted photoelectrochemical (PEC) biosensor for quantification of exosomes based on the

This paper addresses the long-term climatology (over two solar cycles) of total electron content (TEC) irregularities from a polar cap station (Thule) using the rate of change of the TEC index (ROTI). The climatology reveals variabilities over different time scales, i.e., solar cycle, seasonal, and diurnal variations. These variations in different time scales can be explained by different drivers/contributors. The solar activity (represented by the solar radiation index F10.7P) dominates the longest time scale variations. The seasonal variations are controlled by the interplay of the energy input into the polar cap ionosphere and the solar illumination that damps the amplitude of ionospheric irregularities. The diurnal variations (with respect to local time) are controlled by the relative location of the station with respect to the auroral oval. We further decompose the climatology of ionospheric irregularities using the empirical orthogonal function (EOF) method. The first four EOFs could reflect the majority (99.49%) of the total data variability. A climatological model of ionospheric irregularities is developed by fitting the EOF coefficients using three geophysical proxies (namely, F10.7P, Bt, and Dst). The data-model comparison shows satisfactory results with a high Pearson correlation coefficient and adequate errors. Additionally, we modeled the historical ROTI during the modern grand maximum dating back to 1965 and made the prediction during solar cycle 25. In such a way, we can directly compare the climatic variations of the ROTI activity across six solar cycles.

In this manuscript, we introduce the Ionospheric Tomographic Common Clock (ITCC) model of undifferenced uncombined GNSS measurements. It is intended for improving the Wide Area precise positioning in a consistent and simple way in the multi-GNSS context, and without the need of external precise real-time products. This is the case, in particular, of the satellite clocks, which are estimated at the Wide Area GNSS network Central Processing Facility (CPF) referred to the reference receiver one; and the precise realtime ionospheric corrections, simultaneously computed under a voxel-based tomographic model with satellite clocks and other geodetic unknowns, from the uncombined and undifferenced pseudoranges and carrier phase measurements at the CPF from the Wide Area GNSS network area. The model, without fixing the carrier phase ambiguities for the time being (just constraining them by the simultaneous solution of both ionospheric and geometric components of the uncombined GNSS model), has been successfully applied and assessed against previous precise positioning techniques. This has been done by emulating real-time conditions for Wide Area GPS users during 2018 in Poland., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The research has been performed under the support of ATOMIC ESA funded project and the manuscript has been written under PYTHIA EC project support. The ground GNSS network data was provided by Leica in Poland and the position of the GPS transmitters from IGS.

A novel hybrid material (ZIF-7-NH

Global ionosphere maps (GIM) computed from dual-frequency GNSS measurements have been widely used for monitoring ionosphere as well as providing ionospheric corrections in Space Geodesy since 1998. This work focuses on a comprehensive study of the influence of time resolution on GIM performance. One and a half solar cycle of the IGS GIM with higher time resolution and accuracy (the UPC-IonSAT Quarter-of-an-hour time resolution Rapid GIM, AKA uqrg) has been taken as baseline to downsample them to all possible sub-daily temporal resolutions. The performance of the resulting GIMs has been assessed by directly comparing with external vertical total electron content (VTEC) measurements from Jason altimeters over oceanic regions. In order to perform a complete assessment and analysis of involved GIMs, the influence of geographical position and solar and geomagnetic activities was also taken into account during more than one solar cycle. In addition, to have a clear view at the smaller time resolutions, a more accurate assessment, the dSTEC test based on external GNSS measurements not used in the GIM generation was also done during two solstice and two equinox days in 2015 over continental regions. The assessment shows that discrepancy among GIMs with different time resolutions becomes more apparent at low latitudes and also at high solar-geomagnetic activity. The results also suggest that the accuracy for GIMs with time resolution smaller or equal to 60 min is consistent during the period from 2002 to 2019 and is more accurate than other GIMs with lower temporal resolution. Accordingly, high time resolution (including 15, 30, 45 and 60 min) is recommended for the application of GIMs with the highest accuracy., The first author is grateful to the financial support of China Scholarship Council(CSC). The Group for Jason-altimeter data were obtained from the NASA EOSDIS Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory, Pasadena, CA (http://dx.doi.org/10.5067/GHGMR-4FJ01) and the National Oceanic and Atmospheric Administration (NOAA). And we are also thankful to GFZ and SWPC for providing Ap index and F10.7 index, respectively. Also many thanks to Heng Yang for his kind advice of GIM id.

The UQRG data are openly accessible (https://cddis.nasa.gov/archive/gnss/products/ionex) from Crustal Dynamics Data Information System (Noll, 2010). The Kp index is available (ftp://ftp.gfz-potsdam.de/pub/home/obs/Kp_ap_Ap_SN_F107) from GeoForschungsZentrum (Matzka et al., 2021) and Dst index is accessible (http://wdc.kugi.kyoto-u.ac.jp/dstdir/) from World Data Center for Geomagnetism, Kyoto (World Data Center for Geomagnetism et al., 2015)., The ionospheric storms have adverse effects on the radio communications, satellite communications and also the Global Navigation Satellite Systems (GNSS) application. A new Ionospheric storm Scale from Universitat Politècnica de Catalunya (UPC) Global Ionosphere Map (GIM), IsUG, is introduced for characterizing the ionospheric state on a global scale. The IsUG is based on the Vertical Total Electron Content (VTEC) derived from the continuously computed UPC Quarter-of-an-hour time resolution Rapid GIM (UQRG), taking as reference the ones during the period 1997 to 2014. It is similar to the I-scale index previously introduced, although it was over Japan and based on raw GNSS data. The dependence of the VTEC on season, local time and geographical location at each grid point of UQRG is removed by normalizing (i.e., by substracting the mean and dividing by the corresponding standard deviation) the percentage deviation of hourly median VTEC. After validating IsUG versus I-scale, the IsUG distribution is presented and analyzed at global scale during a severe geomagnetic storm from 7 to 10 November 2004 as an example of the potentialities of the new index. The results suggest that the IsUG global map has a great potential for the scientific study of ionospheric storms from a global perspective and also for space weather warning considering the accuracy of the recently developed real-time GIMs., The first author is grateful for the financial support of the China Scholarship Council (CSC). This research has been done under the partial support of the European Space Agency and European Commission funded eMONITOR/MoNEWIC (H2020-ESA-037) project and the European Commission funded PITHIA-NRF (H2020-INFRAIA-2018-2020 101007599) project.

In this paper, a novel adsorbent based on aptamer was prepared via “thiol-ene” click chemistry reaction and used for selective adsorbing the trace phthalic acid esters (PAEs) from drinking water and juice samples, which depended on the group selectivity of aptamers to the ester and the benzoyl groups of PAEs. The morphological structures of the obtained adsorbents were characterized by Fourier Transform infrared spectroscopy (FT-IR), fluorescence spectra, Energy Dispersive Spectrometer (EDS), Brunauer-Emmett-Teller (BET). The selectivity of the prepared adsorbent was evaluated and the results showed that the recovery of the adsorbent with aptamer for PAEs was 66.10–108.90%, while the recovery of adsorbent without aptamer was only 32.41–37.59%. The limit of detection (LOD) (S/N = 3) and limit of quantitation (LOQ) (S/N = 10) of PAEs coupled with HPLC-UV were obtained in the range of 0.11–0.88 μg L−1 and 0.22–1.33 μg L−1, respectively. This work gave a facile and efficient approach to for specific enrichment and highly sensitivity detection of PAEs.

In this work, we introduce a new way of improving the sligthly best performing global ionospheric model (GIM) within the International GNSS Service, the UQRG produced by UPC-IonSAT with the TOMION dual-layer voxel model solved with ground-based dual-frequency carrier phase GPS data combined with kriging interpolation. This is done by increasing its vertical resolution consistently with the heights of the now involved GNSS and DORIS LEO receivers. This has allowed the synergestic combination of vessel-, LEO- and ground-based measurements, providing an increase of the VTEC accuracy at global scale in large regions with sparse GPS ground-based data. The performance of the new resulting multiTOMION model is illustrated with a first application to one of the infrequent datasets, including the whole day of June 5, 2017, with all the involved input data collocated, in particular the vessel-based GNSS ones. The results show in particular: (1) an overall GIM improvement of 3% in standard deviation versus independent JASON-3 VTEC measurements when LEO- and ground- based GPS data are combined with DORIS measurements. And (2) a local improvement of 6–9% in performance versus observed differences of STEC from independent GPS receivers placed at several hundreds of km far from the vessel., This work has been developed thanks to the Atmosfiller project funded by the European Space Agency (ESA) and leaded by Rokubun S.L.

A novel 1-propylene-3-methylimidazolium chloride ([AMIM]Cl) ionic liquid-functionalized Mg/Al layered double hydroxide (IL-LDH) was synthesized via a thiol-ene click reaction and applied to adsorb Congo Red (CR) from aqueous solution. The structure of the prepared adsorbent was characterized mainly using X-ray diffraction (XRD), infrared spectrum (IR), thermogravimetric analysis (TGA), and N2 Brunauer-Emmett-Teller surface area measurements. Batch adsorption experimental factors including initial pH, the amount of adsorbent and adsorption time were investigated. Under optimal conditions, the maximum adsorption capacity of CR on IL-LDH was 288.63 mg·g−1, which was higher than that of Mg-Al-LDHs intercalated with sodium dodecylsulfate (LDH-SDS) (90.86 mg·g−1). In addition, the adsorption of CR on IL-LDH had no obvious change when initial pH values were changed from 5.0 to 10.0, which indicated the adsorbent was pH-independent. Based on the above results, ionic liquid-modified layered double hydroxide may constitute a potential adsorbent for water purification.

Ionospheric irregularities impair Global Navigation Satellite System (GNSS) signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident at low and high latitudes, which are currently gaining the attention of research and industry sectors. This study evaluates the impact of ionospheric irregularities on GNSS positioning in Greenland. We assess the performance of positioning methods that meet the demands of a wide range of users. In particular, we address the needs of the users of mass-market single-frequency receivers and those who require a solution of high precision provided by geodetic dual-frequency receivers. We take advantage of the datasets collected during three ionospheric storms: the St. Patrick’s Day storm of March 17, 2015, the storm on June 22, 2015, and another on August 25–26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in Real Time Kinematics (RTK) positioning. Next, assessing the single-frequency ionosphere-free Precise Point Positioning (PPP), we demonstrate that the model is generally unaffected by ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we reveal that phase signals on the L2 frequency band are more prone to cycle slips induced by ionospheric irregularities than those transmitted on the L1. Such signal properties explain a noticeable decline in the dual-frequency RTK performance during the ionospherically disturbed period and merely no effect for the single-frequency ionosphere-free PPP model.

Intricate Fenton-like catalysts composed of mixed transition metal oxides (TMOs) frequently outperform simple TMOs in scavenging organic contaminants in wastewater. Nonetheless, their activity and/or reusability may sharply decline when abundant heavy metal ions in wastewater adsorb on the catalytic surface and passivate it. This study shows that mesoporous Ca–Mn mixed oxides prepared from a facile combination of Mn and an alkaline earth metal (i.e., Ca) (denoted as CaMnx) can readily overcome this problem. CaMnx without any additive (e.g., H2O2) was able to degrade organic contaminants (e.g., indigo carmine as a model contaminant) fast within 10 seconds, outperforming many other reported heterogeneous Fenton catalysts. Besides organics, the coexisting heavy metal ions (e.g., Cu2+ and Pb2+ as indicators) were also rapidly extracted. The outstanding performance was attributed to the synergy of Ca and Mn. CaO in CaMnx efficiently extracted metal ions via an ion exchange process, and MnOx generated abundant H2O2 and degraded the organics through an uncommon Fenton-like reaction. Therein, Cu species extracted by CaO catalyzed the decomposition of H2O2 into HO˙ radicals, speeding up the degradation reaction of the organics by 81 times. Benefiting from the gradual exposure of fresh Mn-sites protected by unreacted CaO, CaMnx without regeneration treatment maintained high efficiency in scavenging organics and heavy metal ions in cycling tests. CaMnx also showed great promise in treating complex water samples containing various heavy metal ions (e.g., Pb2+, Cu2+, Cd2+, Ag+, Zn2+ and Cr3+) and organic pollutants. The findings of this work enrich the rational design of related functional nanomaterials.

In this work, a novel molecular imprinted polymer (MIP) was prepared with “one-pot” process using acrylamide-2-methylpropanesulfonic acid (AMPS) as the functional monomer and ochratoxin A (OTA) as the template molecule. The morphology and structure of the resulted MIP were characterized, and its adsorption performance and mechanism for the analytes were also investigated. The results showed that the recovery of MIP for OTA was 84.8%, while that of non-imprinted polymer (NIP) was only 4.5%. Moreover, the recovery ratio of OTA to ochratoxin B (OTB) on MIP was 74.4 at pH 8.5, even though OTB content was 100 times as much as OTA content in the mixture of mycotoxins. The limit of detection of this method based on MIP combined with high performance liquid chromatography-fluorescence detection (HPLC-FLD) for OTA was 0.07 ng mL−1, which was lower than 2 ng mL−1 from the European Union limit for beer. The spiked recoveries of OTA were in the range of 95.0 ± 1.5%–97.1 ± 3.1%, which showed that the obtained MIP had great potential to be applied as a specific adsorbing material for mycotoxins in complex samples.

The electron content distribution of the north and south polar ionosphere from 2001 to the beginning of 2019 is analyzed by using the UQRG global ionospheric map (GIM) of vertical total electron content (VTEC), computed every 15 min by UPC-IonSAT with a tomographic-kriging combined technique. We first show that the accuracy of UQRG GIM is slightly better than that of the GIMs of other analysis centers on the whole and also over both poles. Second, we show examples of polar VTEC features in UQRG GIM, previously reported by different authors and with higher-resolution techniques. Third, by means of an unsupervised clustering algorithm, learning vector quantization, we characterize the main features of the ionospheric electron content climatology, separately for the north and south polar regions., The UQRG GIMs, baseline of this work, are openly accessible from IGS server (ftp://cddis.gsfc.nasa.gov/gps/products/ionex/YEAR/DOY/uqrgDOY0.YYi.Z) and from UPC server (https://chapman.upc.es/tomion/rapid/YEAR/DOY_YYMMDD.15min/uqrgDOY0.YYi.Z) being YEAR and YY the four‐ and two‐digit year identifiers, MM is month number, DD is day of month, and DOY is the day of year, all of them with leading zeros when needed (see, for instance, ftp://cddis.gsfc.nasa.gov/gps/products/ionex/2002/003/uqrg0030.02i.Z and https://chapman.upc.es/tomion/rapid/2002/003_020103.15min/uqrg0030.02i.Z). Any missing file can be requested from the authors, in particular from Manuel Hernández‐Pajares (manuel.hernandez@upc.edu). This work has been supported by the POLarGIMs project funded by European Commission Joint Research Centre (JRC). We thank the National Space Science Data Center (NSSDC), Space Physics Data Facility (SPDF), and Principal Investigator K. W. Ogilvie at GSFC, A. J. Lazarus at MIT, and A. Aran at Universitat de Barcelona (UB), for the access of IMF data.

The electron content distribution of the north and south polar ionosphere is analyzed from 2001 to the beginning of 2019 from the Global Ionospheric Maps of VTEC computed each 15 minutes by UPC-Ion...

This paper summarizes the definition and validation of two complementary new strategies, to invert incomplete Global Navigation Satellite System Radio-Occultation (RO) ionospheric measurements, such as the ones to be provided by the future EUMETSAT Polar System Second Generation. It will provide RO measurements with impact parameter much below the Low Earth Orbiters' height (817 km): from 500 km down approximately. The first presented method to invert truncated RO data is denoted as Abel-VaryChap Hybrid modeling from topside Incomplete Global Navigation Satellite System RO data, based on simple First Principles, very precise, and well suited for postprocessing. And the second method is denoted as Simple Estimation of Electron density profiles from topside Incomplete RO data, is less precise, but yields very fast estimations, suitable for Near Real-Time determination. Both techniques will be described and assessed with a set of 546 representative COSMIC/FORMOSAT-3 ROs, with relative errors of 7% and 11% for Abel-VaryChap Hybrid modeling from topside Incomplete Global Navigation Satellite System RO data and Simple Estimation of Electron density profiles from topside Incomplete RO data, respectively, with 20 min and 15 s, respectively, of computational time per occultation in our Intel I7 PC.

In this paper, an ionic liquid mediated molecularly imprinted polymer (IL-MIP) was prepared, in which synthesis system 1-butyl-3-methylimidazolium tetrafluoroborate (IL) was introduced to improve its selectivity and adsorption for the target. The structures of the prepared materials were characterized by SEM, BET, 13CNMR and FTIR, and the adsorption performance of the resultant IL-MIP for BPA and its analogues (phenol, 4-NP, 4-CAP and 1-naphthol) in strong polar media were investigated in detail. The experimental data showed that the adsorption capacities of IL-MIP and molecularly imprinted polymer (MIP) for Bisphenol A (BPA) were 116.16 mg/g and 87.30 mg/g, with imprinting factor of 3.77 and 2.72, respectively. In addition, several other competitive analogues with different polarities (phenol, 4-NP, 4-CAP and 1-naphthol) were chosen to evaluate the selectivity of IL-MIP and the experimental results demonstrated that the synthesized IL-MIP displayed selectivity toward BPA and against analogue molecules. This work provided a simple and effective method to selectively extract BPA from aqueous medium or strong polar organic solvent.

An organic-silica hybrid monolith was prepared by a single-step ring-opening polymerization of octaglycidyldimethylsilyl polyhedral oligomeric silsesquioxane (POSS-epoxy), polyethylenimine (PEI), and β-cyclodextrin (β-CD) in a ternary porogenic solvent consisting of polyethylene glycol, 1,4-butanediol, and 1-propanol. The framework of POSS-PEI hybrid monolith could offer well-defined 3D skeleton, while β-CD with the ability of forming a host-guest inclusion complexes with a variety of compounds could show an ability of specific selection. The obtained hybrid monoliths were successfully applied for separation of phenols, benzoic acids, and nucleobases. Especially due to the introduction of β-CD, positional isomers including hydroquinone and resorcinol, o-nitrophenol and p-nitrophenol, as well as p-chlorophenol and o-chlorophenol were baseline separated and the column efficiency reached 82 300 plates/m for hydroquinone.

This is a post-peer-review, pre-copyedit version of an article published in Gps solutions. The final authenticated version is available online at: http://dx.doi.org/10.1007/s10291-018-0731-0 A simple way of improving the Global Navigation Satellite Systems (GNSS) slant ionospheric correction from Vertical Total Electron Content (VTEC) models is presented. In many GNSS applications, a mapping function is required to convert from VTEC, which may be provided in Global Ionospheric Maps (GIMs), to Slant TEC (STEC). Typical approaches assume a single ionospheric shell with constant height, which is unrealistic, especially for low-elevation signals. To reduce the associated conversion error, we propose the Barcelona Ionospheric Mapping Function and its first implementation at northern mid-latitudes (BIMF-nml). BIMF is based on a climatic prediction of the distribution of the topside vertical electron content fraction of VTEC (hereinafter µ2). BIMF is convenient to be applied since no external data are required in practice. To evaluate its performance, we use as independent reference the STEC difference (so-called dSTEC) values directly measured from mid-latitude dual-frequency Global Positioning System (GPS) receivers that have not been used in the computation of the VTEC GIMs under assessment. It is shown that the use of BIMF improves the GIM STEC estimation compared to the single-layer assumptions. This is the case for the mapping functions used by the International GNSS Service (IGS) and Satellite-Based Augmentation Systems (SBAS). This improvement is valid not only for the UPC GIMs, up to 15% for the year 2014, but especially for the GIMs of other analysis centers, such as those produced by CODE and JPL, up to 32 and 29%, respectively.

In this paper, a 3D hierarchical layered double hydroxide (LDH)/carbon sphere (CS) composite was prepared via self-assembly method. After calcination, the hollow structure with high surface area was formed due to removing the carbon core, meanwhile, LDH turned into layered double oxide (LDO) which exhibited superior anion adsorption capacity. The formation of the prepared material was confirmed and characterized, and the adsorption mechanism of the obtained material for different charge anionic dyes was further discussed in detail. Under the optimal conditions, the maximum adsorption capacities of the prepared materials for amaranth and Orange II were 638.634 and 849.674 mg/g, separately, which revealed that the materials can be applied into the effective adsorption of anionic dyes, especially those with less charges.