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In this work, we have successfully introduced the nitrogen‐rich aromatic ligand 5,5′‐bipyrimidine (BYPM) as auxiliary ligands into the 3‐nitrophthalic acid (NPTA) system, and a Zn(II)‐based coordination polymer [Zn2(BYPM)(NPTA)2]n (1) has been synthesized under solvothermal condition. The 1 is characterized by elemental analysis, Thermogravimetric analysis (TGA), single‐crystal X‐ray diffraction, and X‐ray diffraction patterns (PXRD). The single‐crystal X‐ray analysis indicates that 1 propagates into a layer‐like framework along the ac plane through the coordination Zn2+ ions and further forms a three‐dimensional supramolecular framework through intermolecular C−H⋅⋅⋅O and C−H⋅⋅⋅N hydrogen bonds. Thermogravimetric analysis and powder X‐ray diffraction experiments indicate that 1 has high thermal and solvent stability. Meanwhile, the fluorescence of 1 has been explored. [ABSTRACT FROM AUTHOR]

This work describes a straightforward approach to preparing a hierarchical porous carbon and reduced graphene oxide framework immobilized magnetite nanocrystal composite (Fe 3 O 4 @PC/RGO) using sodium carboxymethylcellulose (Na-CMC), ferric chloride (FeCl 3) and graphene oxide (GO) as starting materials. [Display omitted] Immobilizing nanosized electrochemically active materials with supportive carbonaceous framework usually brings in improved lithium-ion storage performance. In this work, magnetite nanoparticles (Fe 3 O 4) are stabilized by both porous carbon domains (PC) and reduced graphene oxide sheets (RGO) to form a hierarchical composite (Fe 3 O 4 @PC/RGO) via a straightforward approach. The PC confined iron nanoparticle intermediate sample (Fe@PC) was first fabricated, where sodium carboxymethylcellulose (Na-CMC) was employed not only as a cross-linker to trap ferric ions for synthesizing a Fe-CMC precursor sample, but also as the carbon source for PC domains and iron source for Fe nanoparticles in a pyrolysis process. The final redox reaction between Fe@PC and few-layered graphene oxide (GO) sheets contributed to the formation of Fe 3 O 4 nanoparticles with reduced size, avoiding any severe aggregation or excessive exposure. The Fe 3 O 4 @PC/RGO sample delivered a specific capacity of 522.2 mAh·g−1 under a current rate of 1000 mA·g−1 for 650 cycles. The engineered Fe@PC and Fe 3 O 4 @PC/RGO samples have good prospects for application in wider fields. [ABSTRACT FROM AUTHOR]

In this study, we used a combination of graphene oxide-based porous carbon (GC) and titanium chloride (TiCl 3 ) to improve the reversible dehydrogenation properties of magnesium hydride (MgH 2 ). Examining the effects of GC and TiCl 3 on the hydrogen storage properties of MgH 2 , the study found GC was a useful additive as confinement medium for promoting the reversible dehydrogenation of MgH 2 . And TiCl 3 was an efficient catalytic dopant. A series of controlled experiments were carried out to optimize the sample preparation method and the addition amount of GC and TiCl 3 . In comparison with the neat MgH 2 system, the MgH 2 /GC-TiCl 3 composite prepared under optimized conditions exhibited enhanced dehydrogenation kinetics and lower dehydrogenation temperature. A combination of phase/microstructure/chemical state analyses has been conducted to gain insight into the promoting effects of GC and TiCl 3 on the reversible dehydrogenation of MgH 2 . Our study found that GC was a useful scaffold material for tailoring the nanophase structure of MgH 2 . And TiCl 3 played an efficient catalytic effect. Therefore, the remarkably improved dehydrogenation properties of MgH 2 should be attributed to the synergetic effects of nanoconfinement and catalysis. [ABSTRACT FROM AUTHOR]

In this study, nanostructured graphite (nano-G) was added to LiBH 4 and examined with respect to its effect on the hydrogen storage properties of the system. Our study found that nano-G is an effective additive for promoting the reversible dehydrogenation of the LiBH 4 . A series of control experiments were carried out to optimize the sample preparation method, milling time and addition amount of nano-G. In comparison with the pure LiBH 4 , the LiBH 4 /nano-G composite prepared under optimized conditions exhibits enhanced dehydrogenation kinetics and improved cyclic stability. Particularly, after addition of LiH to the LiBH 4 /nano-G composite, the reversibility was further improved. A combination of phase/chemical state analyses has been conducted to gain insight into the promoting effect of nano-G on the reversible dehydrogenation of the LiBH 4 . Our study found that nano-G exerts its promoting effect via interaction with LiBH 4 and as grinding aid. [ABSTRACT FROM AUTHOR]

The 2LiBH 4 –MgH 2 reactive hydride composite is a promising hydrogen storage system due to the combined high hydrogen capacity and relatively moderate reaction enthalpy. However, the sluggish de/rehydrogenation kinetics severely impedes its practical applications. In this study, graphitic carbon nitride (C 3 N 4 ) as a metal-free additive was added to the 2LiBH 4 –MgH 2 composite and examined with respect to the promoting effect on the hydrogen storage properties of the composite. Our study found that mechanically milling with small amount of C 3 N 4 additive can eliminate the incubation period between two dehydrogenation steps and thus markedly enhance the dehydrogenation kinetics of the LiBH 4 –MgH 2 composite. Further cyclic study found that the composite with C 3 N 4 additive exhibits improved cyclic dehydrogenation property although it also shows capacity loss upon cycling, particularly in the second cycle. Combined dehydrogenation property, phase analysis and a series of designed experiments suggested that the C 3 N 4 additive could react with both LiBH 4 and MgH 2 in heating process, and the resulting products may improve the reversible dehydrogenation property of the composite system. [ABSTRACT FROM AUTHOR]

Abstract: In this study, activated carbon (AC) was added to the 2LiBH4–MgH2 composite and examined with respect to its effect on the hydrogen storage properties of the system. Our study found that AC is an effective additive for promoting the reversible dehydrogenation of the 2LiBH4–MgH2 composite. A series of control experiments were carried out to optimize the sample preparation method, milling time and addition amount of AC. In comparison with the neat LiBH4–MgH2 system, the LiBH4–MgH2–AC composite prepared under optimized conditions exhibits enhanced dehydrogenation kinetics, improved cyclic stability and particularly, eliminated incubation period between the two dehydrogenation stages. A combination of phase/microstructure/chemical state analyses has been conducted to gain insight into the promoting effect of AC on the reversible dehydrogenation of the 2LiBH4–MgH2 system. Our study found that AC exerts its promoting effect via tailoring nanophase structure of the 2LiBH4–MgH2 composite. [Copyright &y& Elsevier]

Abstract: A sensitive and selective method for the paraoxon detection based on enzyme inhibition and fluorescence quenching was presented in this study. Under the catalytic effect of acetylcholinesterase (AChE), acetylthiocholine (ATCh) hydrolysis released thiocholine (TCh) which could react with N-(7-dimethylamino-4-methylcoumarin-3-yl) maleimide (DACM) to produce a blue fluorescence compound. Subsequently, AChE catalytic activity was inhibited with the addition of paraoxon, which caused TCh decreased, leading to a significant decrease of the blue fluorescent compound. Meanwhile, p-nitrophenol, the hydrolysis product of paraoxon, would lead to a quenching of the fluorescence. Therefore, fluorescence intensity of the system would decrease dramatically by a combined effect of enzyme inhibition and fluorescence quenching. Under optimal experimental conditions, an excellent linear relationship between the decrease of fluorescence intensity and paraoxon concentration over the range from 5.5×10−12 to 1.8×10−10 molL−1 was obtained. Fluorescence background caused by nonenzymatic hydrolysis of ATCh or other matters was relatively low, the proposed approach offered adequate sensitivity for the detection of paraoxon at 3.5×10−12 molL−1. [Copyright &y& Elsevier]

[Display omitted] • Primary ozonides persist long periods in the ozonolysis of guaiacol. • Criegee intermediates mainly transfer to dioxirane-type compounds. • The formation of secondary ozonides is negligible. • Rate constant positively depends on temperature but not sensitive to pressure. • Frontier molecular orbital property determines the selectivity and reactivity. Quantum chemical calculations with the M06-2X method were performed to uncover the ozonolysis mechanism of guaiacol and several hydroxylated, methoxylated, and methylated phenols to improve the understanding of the ozone-induced attenuation of phenolic compounds. The detailed kinetic properties were obtained by the transition state theory (TST) and the Rice − Ramsperger − Kassel − Marcus (RRKM) theory. Results confirm that the primary ozonides originated from guaiacol occupy considerably long retention time than the short-lived primary ozonides formed from vinyl-type compounds in the air. The TST rate constant of guaiacol ozonolysis is calculated with a value of 8.81 × 10−20 cm3 molecule−1 s−1 at room temperature. The RRKM results prove that the rate constant is positively dependent on temperature but shows no relation with pressure. The reactivity of substituted phenols exhibits a strong correlation with the ozone affinity of carbon atoms and the orbital energy difference (E L o -H ac) between the lowest unoccupied molecular orbital of O 3 and the highest occupied molecular orbital of phenols. The substituents can reduce the value of E L o -H ac and improve the phenols' reactivity, especially when they locate at the ortho - and para -position. The substituents also improve the ozone affinity of carbon atoms due to the electron-withdrawing effect. The methyl group delivers a moderate impact on the reactivity compared to hydroxyl and methoxy groups. [ABSTRACT FROM AUTHOR]

Hashing has been extensively studied for large-scale cross-modal retrieval. However, there are still some unexplored issues with existing methods. First, both the initially-provided similarity graph and one-hot label vector only logically describe the yes or no information, which cannot exactly reflect the correlation between instances. Second, all bits in a binary code contribute equally to Hamming distance, which limits its discriminability to preserve refined semantics. To address these limitations, this paper presents a new method, dubbed Weighted Cross-Modal Hashing (WCMH). It introduces the topological structure of categories to enhance the logical labels, i.e., to recover the real-valued distribution of categories. Moreover, we design a weighted Hamming distance that can enlarge the range of distance values by adaptively learning the weights of different hash bits. In light of this, more discriminative information is embedded into hash codes, and the enhanced semantics can be preserved as much as possible. Extensive experiments validate the superior performance of our WCMH, in comparison with some state-of-the-art cross-modal hashing approaches. [ABSTRACT FROM AUTHOR]

Transition Metal Oxides (TMOs) have drawn significant attention due to their diverse range of properties and applications. The partially filled d orbitals of the transition metal ions, with highly electronegative oxygen atoms, give rise to unique electronic structures that lead to multiple applications due to their magnetic, optical, and structural properties. These properties have a direct influence on chemical reactions that enable tailoring materials for specific applications in catalysis, such as electrocatalysis and photocatalysis. While the potential of TMOs is promising, their development for enhanced functional properties poses numerous challenges. Among these challenges, identifying the appropriate synthesis processes and employing optimal characterization techniques are crucial. In this comprehensive review, an overview of recent trends and challenges in the synthesis and characterization of highly functional TMOs as well as ceramics will be covered with emphasis on catalytic applications. Mesoporous materials play a key role in augmenting their functionality for various applications and will be covered. Ab-initio modeling aspects for the design and development of novel TMO will be also discussed. [ABSTRACT FROM AUTHOR]

• A novel Multi-Scale Differential Feature for ECG Biometrics with Collective Matrix Factorization is proposed. • The micro texture and multi-scale differential signal characteristics of ECG is efficiently captured. • The intra-subject and inter-subject similarities are maximally preserved. • The extracted discriminative ECG representation is more descriptive and robust towards noise. Electrocardiogram (ECG) biometrics has recently received considerable attention and is considered to be a promising biometric trait. Although some promising results on ECG biometrics have been reported, it is still challenging to perform this technique robustly and precisely. To address these issues, this paper presents a novel ECG biometrics framework: Multi-Scale Differential Feature for ECG biometrics with Collective Matrix Factorization (CMF). First, we extract the Multi-Scale Differential Feature (MSDF) from the one-dimensional ECG signal and then fuse MSDF with 1DMRLBP to generate the MSDF-1DMRLBP, which acts as the base feature of the ECG signal. Second, to extract discriminative information from the intermediate base features, we leverage the CMF technique to generate the final robust ECG representations by simultaneously embedding MSDF-1DMRLBP and label information. Consequently, the final robust features could preserve the intra-subject and inter-subject similarities. Extensive experiments are conducted on four ECG databases, and the results demonstrate that the proposed method can outperform the state-of-the-art in terms of both accuracy and efficiency. [ABSTRACT FROM AUTHOR]

For the catalyst for water splitting, low overpotential and longer stability is very important. Here, we developed a simple strategy to prepare an efficient catalyst for oxygen evolution by partially phosphating NiFe-LDH and then etching and growing Prussian blue analogues on it. Benefiting from its unique hierarchical structure, the synthesized NiFeCo PBA-NiFeP catalyst showed excellent electrocatalytic performance in 1 M KOH. At 100 mA/cm2, the overpotential of the oxygen evolution reaction (OER) is only 245 mV and exhibits stability for over 50 h. This is superior to most of the OER catalysts reported so far. Its excellent performance is due to its unique hierarchical structure and the synergistic effect between polymetals, which enables it to have abundant active sites and efficient electron transfer. This controllable and universal strategy will provide a new idea for developing interfacial composites and preparing high efficiency electrocatalysts. • A new NiFeCo-PBA-NiFeP composite was prepared by hydrothermal-phosphating-etching process. • The unique hierarchical structure facilitates gas release and contact between the active site and the solution. • The synergistic effect between multiple metals improves the OER properties of the materials. • The combination of NiFeP and NiFeCo PBA improves the OER performance of the material. [ABSTRACT FROM AUTHOR]

• We propose a method of generating multiple views by using single lead signal. • We introduce the sample diversity information into multi-view learning to seek the more effective discriminant subspace. • To reduce the influence of noise, we introduce a constraint to adaptively learn the relationships between different views. Currently, electrocardiogram (ECG) biometric recognition is a novel research trend, and many methods have been developed. Due to the influence of physical and psychological activities, there are heartbeats diversities of the same person. However, the existing ECG biometric recognition methods do not make use of sample diversity information. In this paper, we present a multi-view discriminant analysis approach in the consideration of sample diversity for ECG biometric recognition. Firstly, we propose a method of generating multiple views by using single lead ECG signal. Secondly, we present a multi-views learning framework, which takes sample diversity into account to generate a more discriminative subspace. Thirdly, to obtain a more robust solution, we introduce a denoising constraint to learn the relationships between different views, which can create a stable representation against ECG noise. At last, experimental results demonstrate that compared with the state-of-the-art methods on four databases, the proposed method can achieve competitive performance compared to state-of-the-art ECG biometric recognition methods. [ABSTRACT FROM AUTHOR]

• Synthesized accordion-like Ti 3 C 2 T x MXene with large layer spacing. • Synthesized Ti 3 C 2 T x /TiO 2 /PANI composites with sandwich structure. • The optimal absorption was up to −65.61 dB at 2.18 mm and EAB to 5.92 GHz at 2.10 mm. Ti 3 C 2 T x MXene is an excellent electromagnetic wave (EMW) absorber with excellent electrical conductivity and abundant surface functional groups. In this research, Ti 3 C 2 T x /TiO 2 /PANI multi-layer composites were successfully synthesized by HCl and LiF etching, one-step hydrothermal method and in-situ polymerization. Ti 3 C 2 T x can provide more electron transfer paths due to its unique multilayer structure and high specific surface area. The growth of TiO 2 particles on the surface of Ti 3 C 2 T x through hydrothermal reaction enhances the interface polarization, and then polyaniline (PANI) is doped on the surface of Ti 3 C 2 T x where TiO 2 particles are grown by in-situ polymerization. Due to the excellent dielectric properties and synergistic effects of the material itself, Ti 3 C 2 T x /TiO 2 /PANI composites have excellent EMW absorption property. In this study, the Ti 3 C 2 T x /TiO 2 /PANI composites showed the strong reflection loss (RL) of at 13.92 GHz, which was −65.61 dB, and the thickness was only 2.18 mm. Moreover, the composites also exhibit a wide absorption band, with an effective absorption bandwidth (RL < -10 dB) of 5.92 GHz (11.84 GHz to 17.76 GHz) at 2.10 mm. The results show that the Ti 3 C 2 T x /TiO 2 /PANI composites are expected to become EMW absorber with thin thickness and high absorption strength. [ABSTRACT FROM AUTHOR]

• We propose a structural sparse representation algorithm with class-specific dictionary for ECG biometric recognition. • A mixed regularization is employed to heartbeats which belong to same subject for obtaining a robust and stable feature. • A graph regularization is used to minimize the difference between heartbeats of intra-class. • We also learn a sub-dictionary for each class making the feature more discriminative. For traditional person recognition, most methods are knowledge-based and token-based such as the methods using password, ID number or other secret information, and to enhance its security, biometric recognition is widely used in many areas. As a biometric trait, electrocardiogram (ECG) signal is gaining more attention due to the fact that it is not easy to be faked compared with other traits and only exists in living subjects. However, ECG signals are influenced by numerous factors easily and have low stability, resulting in unsatisfied recognition performance. In this paper, we propose a structural sparse representation algorithm for ECG signals and learn class-specific dictionary for each class to address these problems. Firstly, we segment heartbeats for each subject's signal. Moreover, the mixed regularization l 2,1 norm is utilized for ECG heartbeats to obtain a robust and stable feature. It is encouraged that if the atom is used to describe the heartbeat of one subject's heartbeat, it may be used to describe other heartbeats of the same subject. In addition, a graph regularization is used to minimize the difference between heartbeats of intra-class. Finally, we conduct experiments on three public ECG databases to verify the proposed method and the subject recognition accuracy can reach to 99.66% on PTB database. From the experimental result, the proposed method can take full advantage of ECG structural characteristic and get a better performance compared with state-of-the-art methods. [ABSTRACT FROM AUTHOR]

• GNMF method is used to integrate the ECG data information, geometry and label information. • GNMF also achieves dimensionality reduction and primary feature extraction. • Sparse representation is utilized to obtain final features to perform ECG matching. • Our method shows robust recognition performance on two public datasets. As a vital sign, Electrocardiogram (ECG) has highly discriminative characteristics in the field of biometrics. This paper aims to propose a novel robust ECG biometric method based on graph regularized non-negative matrix factorization (GNMF) and sparse representation. First, after ECG signal pre-processing and heartbeat segmentation, GNMF is used to reduce the dimensions of each heartbeat. In GNMF, an affinity graph is constructed to encode the geometrical information and label information in order to obtain more discriminative features. Second, in order to seek highly discriminability of ECG, the sparse representation is utilized to perform final feature extraction. We evaluate the method on two public datasets: ECG-ID and MIT-BIH Arrhythmia (MITDB). When fusing three heartbeats as a test sample, the accuracy achieves 98.03% and 100% on the ECG-ID dataset and the MITDB dataset, respectively. Experimental results show that the proposed method is robust for within-session and across-session of the ECG signal. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction is a momentous part of electrochemical energy storage and conversion devices such as rechargeable metal–air batteries. It is particularly urgent to develop low-cost and efficient electrocatalysts for oxygen evolution reactions. As a potential substitute for noble metal electrocatalysts, transition metal selenides still prove challenging in improving the activity of oxygen evolution reaction and research into reaction intermediates. In this study, a simple one-step solvothermal method was used to prepare a polymetallic compound carbon matrix composite (Co9Se8/Ni3Se4/Fe3O4@C) with a multilayered nanosheets structure. It exhibited good OER activity in an alkaline electrolyte solution, with an overpotential of 268 mV at 10 mA/cm2. In addition, this catalyst also showed excellent performance in the 24 h stability test. The composite presents a multi-layer sheet structure, which effectively improves the contact between the active site and the electrolyte. The selenide formed by Ni and Co has a synergistic effect, and Fe3O4 and Co9Se8 form a heterojunction structure which can effectively improve the reaction activity by initiating the electronic coupling effect through the interface modification. In addition, carbon quantum dots have rich heteroatoms and electron transferability, which improves the electrochemical properties of the composites. This work provides a new strategy for the preparation of highly efficient OER electrocatalysts utilizing the multi-metal synergistic effect. [ABSTRACT FROM AUTHOR]

MgH2 has a high hydrogen content of 7.6 wt% and possesses good reversibility under normal conditions. However, pristine MgH2 requires a high temperature above 300 °C to release hydrogen, with very slow kinetics. In this work, we utilized Ti3CN MXene to reduce the operating temperature and enhance the kinetics of MgH2. The initial temperature of MgH2 decomposition can be lowered from 322 °C for pristine MgH2 to 214 °C through the employment of Ti3CN. The desorbed MgH2 + 7.5 wt% Ti3CN can start absorption at room temperature, while the desorbed pristine MgH2 can only start absorption at 120 °C. The employment of Ti3CN can significantly improve the hydrogen release kinetics of MgH2, with the desorption activation energy decreasing from 121 to 80 kJ mol−1. Regarding thermodynamics, the desorption enthalpy changes of MgH2 and MgH2 + 7.5 wt% Ti3CN were 79.3 and 78.8 kJ mol−1, respectively. This indicates that the employment of Ti3CN does not alter the thermal stability of MgH2. Phase evolution studies through the use of X-ray diffraction and electron diffraction both confirm that Ti3CN remains stable during the hydrogen release and uptake process of the composite. This work will help understand the impact of a transition metal carbonitride on the hydrogen storage of MgH2. [ABSTRACT FROM AUTHOR]

[Display omitted] Sluggish kinetics of the oxygen evolution reaction during the water splitting requires high-performance electrocatalysts with low cost and good stability. Metal-organic frameworks (MOFs) have attracted much attention as electrocatalysts owing to their unique properties. To improve their electrocatalytic activity and stability, we report a selenylation method to modulate the morphology and interfaces by forming flower-like MOF-selenide nanocomposites. The optimal sample exhibits high activity with an overpotential of 260 mV at 10 mA cm−2, much better than commercial RuO 2 and the control samples. Moreover, the optimal sample has the lowest Tafel slope of 54.3 mV dec-1, indicating the fast reaction kinetics, which can be attributed to the lower charge-transfer resistance and high intrinsic activity. Chronoamperometry shows that the optimal sample can maintain the current density for 60 h at 10 mA cm−2 after the initial surface reconstruction, demonstrating good stability. This study provides a new perspective on the development of highly efficient electrocatalysts based on polymetallic MOFs. [ABSTRACT FROM AUTHOR]

Oil shale (OS), from which petroleum-like shale oil can be obtained via retorting, is one of the most promising alternative fossil fuels due to its huge reserve. A main obstacle to OS retorting is the required high-energy input, particularly for underground retorting. Recently a low-energy-input route via self-heating retorting (SHR) was developed (Guo et al., 2013 and 2014). However, its unclear reaction mechanism hinders its further development. Herein, the reaction mechanism of SHR was analyzed by using Huadian OS and thermal analysis techniques. The results suggest anaerobic retorting (AR) used for preparing shale oil produces substantial residual carbon (RC) byproduct, and the heat contained in RC is more than the energy input needed by an AR process. While in SHR process, by reaction-kinetics control, part of kerogen is first pyrolized into oil and RC before exposed to air, and then RC in-situ reacts with the diffused air to release heat for progressing SHR and replacing external heat supply. In-situ utilizing RC by SHR process partly explains why SHR itself provides heat to increase retorting temperature but without obviously lost shale-oil yield. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heterogeneous MnNiCoP/FeOOH was successfully prepared by electrodeposition phosphating electrodeposition. • The interfacial synergism results in excellent HER and OER electrocatalytic activity and stability. • The catalyst can provide 1.627 V battery voltage at 100 mA cm−2, and shows good stability and durability. The production of three-dimensional heterogeneous structures is a vital approach for the creation of high-performance bifunctional electrocatalysts. Herein, three-dimensional heterostructure MnNiCoP/FeOOH (MNC-P/FeOOH) supported by Ni foam was prepared by simple electrodeposition and phosphorylation as a bifunctional electrocatalyst. The results showed that the required overpotential for MNC-P/FeOOH catalyst to reach 100 mA cm−2 current density was 124 mV and 251 mV in 1.0 M KOH solution, respectively. Construction of heterojunction not only improves the OER performance of MnNiCoP, but also reduces the potential required to drive the integral water splitting at 100 mA cm−2 current density. The electrocatalytic activity of MNC-P/FeOOH is greatly increased due to a distinctive interface synergy and strong electronic contacts in the MNC-P/FeOOH heterojunction. This design approach of bifunctional transition metal phosphides provides a potential route to achieve total water splitting. [ABSTRACT FROM AUTHOR]

Recently a facile low-energy-input retorting route but without marked loss in the shale-oil yield is developed, which is achieved by a self-heating effect, that is, spontaneously increasing retorting temperature in the absence of external heat provision (Guo et al., 2013, 2014). In this work, the applicability of self-heating retorting (SHR) process to three Chinese oil shales from different places (i.e., Longkou, Huadian and Fushun) is studied. Of these three oil shales, Fushun oil shale is associated with coal and was previously abandoned during coal mining due to its not high kerogen or oil content. The results show that it’s hard for Fushun oil shale to obtain satisfying self-heating effect, while Longkou or Huadian oil shale with higher kerogen or oil content shows satisfactory SHR. However, by adding suitable amounts of Longkou or Huadian oil shale into Fushun oil shale, a satisfying self-heating effect can be obtained as well. Thus, the relatively low-grade Fushun oil shale can also be well utilized to produce shale oil via this facile SHR route. Moreover, to utilize Fushun oil shale with a greener SHR process, the process can be performed by co-retorting Fushun oil shale with pine needles, a kind of renewable biomass. This finding also provides a new starting point for exploring plentiful biomass resources to utilize low-grade oil shale to produce oil in the future work. [ABSTRACT FROM AUTHOR]

• We propose a robust multi-feature collective non-negative matrix factorization model. • We learn an unified representation in the semantic space from multiple LBP histograms. • We integrate label information and multiple norms to enhance the discrimination. The field of electrocardiogram (ECG) biometrics has received considerable attention in recent years. Although some promising methods have been proposed, it is challenging to design a robust and precise method to improve the recognition performance of ECG signals with noise and sample variation. While the advantage of improved local binary pattern (LBP) for establishing identities has been widely recognized, extracting the latent semantics from multiple LBP features has attracted little attention. We propose a robust multi-feature collective non-negative matrix factorization (RMCNMF) model to handle noise and sample variation in ECG Biometrics. We extract multiple LBP histograms as feature descriptors from segmented ECG signals, and propose a multi-feature learning framework that learns unified representations in the shared latent semantic space via collective non-negative matrix factorization. To further enhance the discrimination of learned representations, we integrate label information and multiple norms in the proposed model, which not only preserves intra- and inter-subject similarities but also mitigates the influence of noise and sample variation. RMCNMF can be solved by an efficient iteration method, for which we provide a convergence analysis in detail. Extensive experiments on four ECG databases show that it performs competitively with state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report a novel method of improving the reversible dehydrogenation properties of the 2LiBH4–MgH2 composite. Our study found that mechanically milling with small amount of Al powder can markedly shorten or even eliminate the problematic incubation period that interrupts the dehydrogenation steps of the 2LiBH4–MgH2 composite. But the resulting composite showed serious kinetics degradation upon cycling. In an effort to solve this problem, we found that combined usage of small amounts of Al and MgO enabled the 2LiBH4–MgH2 composite to rapidly and reversibly deliver around 9 wt% hydrogen at 400 °C under 0.3 MPa H2, which compares favorably with the dehydrogenation performance of the composites with transition-metal additives. A combination of phase/microstructural analyses and series of control experiments has been conducted to gain insight into the promoting effects of Al and MgO. It was found that Al and MgO additives act as precursor and promoter for the formation of AlB2 heterogeneous nucleation sites, respectively. [Copyright &y& Elsevier]

• Ruddlesden-Popper type polycrystals La 3 Ni 2 O 7 /LaNiO 3 and La 2 NiO 4 /La 2 O 3 were synthesized. • The structural and electromagnetic properties were analyzed. • The interstitial O2– and V O in polycrystals were studied based on XPS and XRD. • The RL of La 3 Ni 2 O 7 /LaNiO 3 and La 2 NiO 4 /La 2 O 3 reached –22.63 and −50.06 dB in S-band. Given the remarkable performances of Ruddlesden-Popper (RP) type oxides in electronic devices, the study of their intrinsic dielectric, magnetic and electromagnetic microwave (EMW) absorption properties are still missing. Herein, two kinds of Lead-free relaxor-ferroelectric BNT-based ceramic hierarchical polycrystalline alloys (La 3 Ni 2 O 7 /LaNiO 3 , La 2 NiO 4 /La 2 O 3) were prepared via a facile solvothermal and high-temperature annealing technique as high-performance EMW absorption materials (MAMs). By a means of adjustment of solvothermal time in the precursor systems, Nickel salt layers precipitation declined gradually. The phase and crystal state of the powders were characterized by X-ray diffraction (XRD) with refinement treatment (Rietveld analysis). XPS was utilized on the determination of interstitial O2– quantitatively in La 3 Ni 2 O 7+δ (δ = 1.95) and La 2 NiO 4+δ (δ = 0.75). Responsible to the synergistic effect of dielectric and magnetic response and well-matched impedance, the as-fabricated MAMs performed excellent wave absorbability, especially in low frequency (S-band). In details, La 3 Ni 2 O 7 /LaNiO 3 achieved optimal effective absorption band (f E) 3.36 GHz at 9.52–12.80 GHz and a minimum reflection loss (RL min) −43.30 dB with a thickness of 2.2 mm. Moreover, La 3 Ni 2 O 7 /LaNiO 3 and La 2 NiO 4 /La 2 O 3 overcame the challenge of absorbers' thickness in S-band, of which the RL reached –22.63 and −29.90 dB at 0.7 mm, respectively. Noteworthily, La 3 Ni 2 O 7 /LaNiO 3 obtained RL value of −50.06 dB at 10.72 GHz with a device thickness of 2.8 mm. It is emphasized that this report has interpreted the EMW absorption capacity and mechanism exhaustively, which will initiate simultaneous enhancement of recoverable energy density and efficiency application of RPs. [ABSTRACT FROM AUTHOR]

Multiple loss mechanisms of conductive loss, interface polarization loss, dipolar polarization and magnetic resonance loss endow excellent performance of Fe 3 N@C composites. • Fe 3 N@C hybrid composites were synthesized by using amino acids as nitrogen sources. • The relaxation times were calculated by Debye theory to investigate dielectric behavior of hybrid composites. • The optimal performance with RL min of −77.6 dB and EAB max of 7.76 GHz were achieved. Fe 3 N has been considered as a new generation of ideal ferromagnetic materials with the virtues of high saturated magnetization and high resistance to oxidation. However, a facile and eco-friendly fabrication of Fe 3 N still needs to be investigated. Herein, the gelatin derived from fish skin was chosen as the raw material of carbon and the amino acid inherent in fish skin can act as a nitrogen source for the generation of Fe 3 N. Besides, the influence of graphitization degree to dielectric behavior of composites was further investigated. In this work, the composites fabricated by 0.8 mmol Fe(NO 3) 3 exhibited optimal absorption performance with the minimum reflection loss of −77.6 dB at 2.2 mm. Besides, the absorption bandwidth was detected as 7.76 GHz (covering from 10.24 to 18 GHz) at the matching thickness of 2.7 mm. According to the analysis of dielectric constant, the degree of graphitization affects the dielectric behavior mainly in determining the orientation speed of the dipole and the conductive loss. This work provides a new thought for the investigation of the electromagnetic absorption mechanism of composite. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) with sluggish kinetics is a bottleneck for the large-scale application of water electrolysis. Herein, solid-solution hexagonal Ni0.5Co0.5Se nanoflakes are designed and successfully synthesized via a facile hydrothermal method with a much lower overpotential of 216 mV at 10 mA cm−2 and a Tafel slope of 37.08 mV dec−1. [ABSTRACT FROM AUTHOR]

Oil shale (OS) is a particularly promising alternative fossil fuel source. However, very different from coal, its inorganic mineral content is very high. The organic matters (mainly kerogen) are finely distributed in the inorganic minerals. Therefore, the minerals may affect the processing of OS, whose elucidation is critical to the choice of processing conditions. In this work, different minerals (SiO2, CaCO3, and Al2O3) were added to OS with different mass ratios of OS to mineral, respectively. Then, the thermogravimetric (TG) technique was employed to analyze the reaction behavior of these different OS/mineral mixtures in N2and in air for studying the influence of minerals on the OS pyrolysis in N2(i.e., retorting) and on the OS combustion in air. The results show that CaCO3and Al2O3have a promoting effect on both pyrolysis and combustion of OS, and they can decrease the reaction activation energy of both kinds of processes. However, SiO2has an inhibitive effect and can increase the reaction activation energy for both kinds of processes. It is hoped that the present study can further increase the understanding toward the effect of different minerals on the OS reactions. [ABSTRACT FROM PUBLISHER]

Electronic structure regulation is one of the essential strategies for developing advanced electrocatalysts. Herein, FeOOH was electrodeposited on the surface of NiSe 2 /Ni 2 O 3 , resulting in a layered NiSe 2 /Ni 2 O 3 /FeOOH interfacial composite with a unique hierarchical structure and strong electronic interactions. This sheet-like nanostructure provides sufficient space for mass transfer, fully exposes the active sites, and accelerates the reaction kinetics. The optimal sample exhibits excellent oxygen evolution reaction (OER) activity with a low overpotential of 270 mV at a current density of 100 mA cm−2 and a Tafel slope of only 54.7 mV dec−1. It also has excellent durability. This study provides a new perspective for developing efficient electrocatalysts by constructing interfacial composites. [Display omitted] • Construction of nanocomposites was built by facile electrodeposition. • The electrocatalyst exhibits an overpotential of 270 mV and a Tafel slope of 54.7 mV dec−1 at 100 mA cm−2. • Interfacial electron redistribution is the fundamental reason for improving electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Finger vein pattern, as a promising hand-based biometric technology, has been well studied in recent years. In this paper, a new superpixel-based finger vein recognition method is presented. In the proposed method, we develop two types of effective superpixels, i.e. stable superpixel and discriminative superpixel to represent finger vein image and these superpixels are expected to play different roles in matching stage. In detail, the stable and discriminative superpixels are firstly learned from the training images for each enrolled class. When verifying a testing image, we just compare the superpixels at the same location as the two types of superpixels in template. Then, the two types of superpixels are combined utilizing a reversible weight-based fusion method in score level. Additionally, to further improve the recognition performance, we explore the superpixel context feature (SPCF). For each superpixel the SPCF is obtained by comparing the current superpixel with its surrounding neighbors. In the final matching stage, we integrate the matching score of two types of superpixels and it of the SPCF using the weighted SUM fusion method. The experimental results on two open finger vein databases, i.e. PolyU and SDUMLA-FV, show that our method not only performs better than the existing superpixel-based method, but also has advantages in comparison with some traditional ones. [ABSTRACT FROM AUTHOR]

Caustic calcined magnesia (main component is MgO) can be used to produce Mg(OH) 2 by ammonium-circulation method (reaction steps: (1) MgO + 2NH 4 + → Δ Mg 2 + + 2NH 3 ↑ + H 2 O and (2) Mg 2 + + 2NH 3 ↑ + 2H 2 O → Mg(OH) 2 ↓ + 2NH 4 + ; Overall: MgO + H 2 O → Mg(OH) 2 ↓). NH 4 Cl, NH 4 NO 3 and (NH 4 ) 2 SO 4 have exhibited the ability to be used as a circulation medium. In this work, ammonium acetate (NH 4 Ac) was investigated as a circulation medium. The purity of the used caustic calcined magnesia (i.e., MgO content) is 85 wt.%. The results show that NH 4 Ac is a much more efficient circulation medium than NH 4 Cl, NH 4 NO 3 or (NH 4 ) 2 SO 4 is. Step (1) in the ammonium-circulation method can be significantly accelerated if NH 4 Ac is used as the circulation medium. The reason for the high efficiency of NH 4 Ac was also analyzed. By using NH 4 Ac as the circulation medium, rose petal-like Mg(OH) 2 precipitate can be prepared in the presence of polyethylene glycol. The purity of the prepared Mg(OH) 2 is more than 99 wt.%. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiCoP electrocatalyst was prepared by two-step hydrothermal phosphating process. • A simple and controllable method was used to construct layered porous plates to reduce the charge transfer resistance of NiCoP materials and showed the best catalytic performance. • NiCoP porous sheet has a large electrochemical active surface area and catalytic activity and the stability of the catalyst was investigated. Research on the stable and high-efficiency transition metal-based electrocatalyst to achieve hydrogen evolution reaction (HER) becomes one of the core solutions for water decomposition. Non-precious metals phosphide has the potential to become a non-noble metal electrocatalyst due to its good electronic structure effect, extremely low price, and expected durability in a larger pH range. In this paper, hexagonal NiCoP porous nanosheets were synthesized using a facile hydrothermal and post-phosphating method. We anticipate that bimetal doping can further enhance electrocatalyst activity as well as improve the capability of absorbing hydrogen from the materials by modifying the electronic structure. The obtained NiCoP electrocatalyst behaves outstanding catalytic performances for HER in alkaline media with 83 mV initial overpotential at 10 mA cm−2, as well as the low Tafel slopes of 41 mV dec−1. In addition, the current density showed almost no attenuation in the 10 h chronoamperometry experiment. The outstanding catalytic function can be attributed to the nanosheets with many orifices, which can expand the effective reaction specific surface area, promote mass transport and boost the water decomposition efficiency. And the collaboration of Ni and Co in NiCoP nanosheets can also improve the electrochemical function. Moreover, the current work offers a feasible approach for synthesizing a cheap and efficient NiCoP electrocatalyst for HER, which is especially appealing to practical application. [ABSTRACT FROM AUTHOR]

Oxides can be utilized in various industries. They are frequently doped with other cations to improve some key properties. Although doping is common, the doping mechanism related to transport of doped metallic cations in the oxide grain on the atomic scale still needs to be clarified. Here, with MgO as a prototype, Zn cations in a polycrystalline MgO film was investigated utilizing microstructure observation and chemical composition analyses. Results show that although there are various defects such as vacancies, dislocations, voids, grain boundaries and impurity ions in the polycrystalline MgO film, a Zn cation could penetrate the overall polycrystalline MgO film. Although a Zn cation move relative randomly in an individual MgO grain, as there is a constant source and a constant sink for Zn located at opposite sides of the MgO film, the Zn cation could move directionally on a relatively macro scale from the source to the sink. Unlabelled Image • A Zn doped MgO film could be obtained by a powder thermal diffusion alloying method on a magnesium alloy. • Many Zn dots can be observed at the surface of the MgO lattice. • The Zn dots are deduced to be substitutional cations in the MgO lattice. • A Zn cation could penetrate the overall polycrystalline MgO film. • The Zn cation could move directionally on a relatively macro scale from the source to the sink. [ABSTRACT FROM AUTHOR]

• Hydrogen storage properties of LaNi 4.75 Mn 0.25 alloy within 1000 cycles is studied. • Degradation process is revealed from both property and structure points of view. • Microstrains cause pulverization and crystal damage, degrading H 2 storage properties. • c / a increases with cycling, decreasing hysteresis and degradation trend. AB 5 -type hydrogen storage alloys have been extensively studied due to their wide applications, but their degradation process is still controversial, hindering the improvement in their cycling performance. In this work, the degradation mechanism of an AB 5 -type LaNi 4.75 Mn 0.25 alloy with single CaCu 5 -type phase structure has been investigated based on its long-term hydrogen storage properties and the structural changes during cycling. It is found that within 1000 hydrogen absorption/desorption cycles in the temperature range of 343–383 K, the P-C-T curves remain a single plateau, but the plateau slope becomes steeper and the hydrogen storage capacity decreases. These degradation phenomena are caused by the structural evolution of the alloy including particle pulverization and crystal lattice damage. The internal driving force of the structural changes is found to be the microstrains generated during hydrogen absorption/desorption. But with cycling, the isotropic parameter c / a increases, decreasing the hysteresis and slowing down the degradation process. [ABSTRACT FROM AUTHOR]

• Highly crystalline MHCFs have been synthesized in the presence of citrate. • The method is applicable to MHCFs with different transition metals. • The MHCFs show little Fe(CN) 6 vacancies and rich alkaline ions. • Improved performance for Na ion storage is achieved. In this work, highly crystalline transition-metal hexacyanoferrates (MHCFs) have been synthesized in the presence of citrate, which is found not only to mediate the precipitation reaction rate but also prevent the MHCF crystals from aggregation. This method is applicable to a wide range of MHCFs with different transition metals (e.g., Co, Ni, Mn and Zn). The highly crystalline MHCFs with little Fe(CN) 6 vacancies and rich alkaline ions exhibited significantly improved electrochemical performance for Na ion storage in both aqueous and organic electrolytes. The effect of transition metals in MHCFs on the Na ion storage performance has been investigated in an aqueous electrolyte. Results showed that the CoHCF nanocube sample displayed the highest electrochemical performance than other MHCFs samples synthesized in this work. This CoHCF sample exhibits a specific capacity of 85 mAh g−1 at 1 A g−1. The CoHCF sample also displays a good cycling stability with capacity retentions of 92% after 12,000 cycles in aqueous electrolyte (0.5 M Na 2 SO 4) and 78% after 10,000 cycles in organic electrolyte (NaClO 4 in PC + EC with 5% FEC). [ABSTRACT FROM AUTHOR]

• Highly dispersed WN quantum dots confined within porous BCN is prepared. • The composite as anode material exhibits high rate performance in Li ion batteries. • Porous BCN and ultra-small WN particles synergistically contribute to the high performance. Electrode materials play a paramount role in developing high-performance lithium ion batteries (LIBs). Nanostructured electrode materials can offer unique advantages, such as high rate capability. Here, we describe a strategy for synthesizing advanced anode materials with tungsten nitride (WN) quantum dots (2–5 nm) firmly anchored on mesoporous ternary borocarbonitride (BCN). A composite sample exhibited reversible capacities of 683.4 and 366.9 mAh g−1 at current densities of 0.1 and 4 A g−1, respectively, suggesting good rate capability. The electrode is also stable against cycling with only 2.7% capacity loss after 500 cycles at 1 A g−1. This high performance can be ascribed to the highly dispersed WN quantum dots, which provide a high active surface for lithium ions, and significantly shortened pathways for charge transport. In addition, the porous BCN framework facilitates transfer of the electrolyte and offers a strong binding interaction with the WN quantum dots to alleviate the volume expansion and particle agglomeration issues. Further analysis of lithium storage kinetics revealed the important role that the pseudocapacitive mechanism played in the charge storage process. This work demonstrates the great potential of tungsten-based composite as high-rate anode for high-performance LIBs. [ABSTRACT FROM AUTHOR]

Silicon has been regarded as a promising anode materials for lithium ion battery. However, large volume change during lithiation/delithiation process impedes its application for energy storage. Two-dimensional titanium carbide or carbonitride nanosheet, known as MXene, possesses layered-stacked structure and high electrical conductivity. So MXene has a great potential to improve the cycle life of silicon anode because its layered-stacked structure can accommodate the volume expansion of silicon. Herein, we present a facile process to prepare sandwich-like silicon/Ti 3 C 2 T x MXene composite directed by electrostatic self-assembly. This unique architecture could accommodate silicon expansion during lithiation and enhance electronical conductivity. The silicon/Ti 3 C 2 T x MXene composite delivers an initial reversible capacity of 1067.6 mAh g−1 at a current of 300 mA g−1. Moreover, it shows a steady cycling ability of 643.8 mAh g−1 at 300 mA g−1 after 100 cycles. This work may shed lights on the development of high energy density silicon-based anode materials for lithium ion battery. • Two-dimensional titanium carbide (Ti 3 C 2 T x MXene) is successfully synthesized. • Ti 3 C 2 T x MXene tends to attract positively charged Si by electrostatic self-assembling. • Si/Ti 3 C 2 T x MXene could accommodate Si expansion and enhance electronical conductivity. • The capacity of Si/Ti 3 C 2 T x MXene is 643.8 mAh g−1 at 300 mA g−1 at 100th cycle. • The capacity retention of Si/Ti 3 C 2 T x MXene is superior to that of similar Si/C anode. [ABSTRACT FROM AUTHOR]

The shielding mechanism for conversional electromagnetic shielding material is mainly dependent on the reflection, thus the electromagnetic interference (EMI) or pollution can't be really solved, owing to the 2nd interference or pollution. To overcome this barrier, we developed an absorption dominate EMI shielding material, using low permittivity component (TiO 2 , amorphous carbon and SiO 2) to decorate magnetic carbonyl iron (CIF). Consequently, the impedance matching ability can be greatly improved, simultaneously showing desirable dual magnetic and dielectric loss ability. The varied morphology, crystal phases and EMI shielding performance of resultants have been well studied. It has been confirmed that the reflection coefficient of SiO 2 decorated CIF sample could be reduced from 90 to 56.6%, suggesting the improved EM absorption ability. Meanwhile, it corresponding absorption coefficient could up to 43.3%, which is also much better than TiO 2 or amorphous decorated CIF. The method for the successfully use low-dielectric component to decorate magnetic metal has been demonstrated as a useful strategy for the preparation of achieving absorption dominate EM shielding material. Carbonyl iron decorated by the component with low dielectric exhibits excellent absorption dominate electromagnetic shielding performance. Image 1 • Low-dielectric component (SiO 2 , C and TiO 2) can be easily coated on carbonyl iron. • The as-prepared shows dual magnetic and dielectric loss ability. • The impedance matching ability can be greatly improved. • The optimal sample has an excellent absorption dominate ability with a absorption coefficient of 43.3%. • The total shielding effectiveness was ~29 dB under a thickness of 1.5 mm. [ABSTRACT FROM AUTHOR]

Laminated hybrid carbon of amorphous carbon and RGO (reduced graphene oxide) perovskite composite, La 0.8 FeO 3 /C/RGO-BD, was fabricated by a simple method in one pot. The amorphous carbon was carbonized from d -glucose which also played a role as reducing agent. RGO provided a great condition for the formation of conductive loops. While A-site cation deficiency perovskite La 0.8 FeO 3 doped at carbon nanosheets was induced to adjust the comprehensive microwave absorption properties. The phase and composition characteristics were studied by X-ray diffraction patterns (XRD), Raman and FT-IR spectrums and X-ray photoelectron spectroscopy (XPS), especially the confirmation of the existence of A-site cation deficiency and Oxygen vacancy. The morphology and microstructure of samples were visualized by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The electromagnetic microwave absorption properties were further studied, as the reflection loss of La 0.8 FeO 3 /C/RGO-BD reached −42.69 dB at 8.08 GHz with an effective band 2.72 GHz at 3.15 mm. And the excellent microwave absorption properties were confirmed by impedance matching, one quarter-wavelength theory, Debye relaxation polarization theory and eddy current loss. Image 1 [ABSTRACT FROM AUTHOR]