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In this work, a pH-tunable multicolor luminescent lanthanide-based hydrogel (CS/DEX/CP) was prepared based on lanthanide coordination polymer (CP), dextran aldehyde (DEX) and chitosan (CS). The CP was obtained by the self-assembly of guanosine acid (GMP), ciprofloxacin (CIP), Eu3+, and Tb3+. As-prepared CS/DEX/CP hydrogel could emit blue, green, and red luminescence of CIP, Tb3+, and Eu3+, respectively. It was also found that the luminescence of CS/DEX/CP hydrogel exhibited visual color change in the pH range of 5.5 to 8. Such pH-sensitive hydrogel was multicolor-responsive to protons produced by bacterial growth, therefore, it could provide early warning of bacterial infection by Naked-eye. In addition, the increased acidity resulted in not only the degradation of acid-labile Schiff base linkages between DEX and CS, but also the fracture of coordination between CIP and lanthanide ions. As a result, the released CIP and CS showed significantly antibacterial activity against both S.aureus and E. coli.

Radio frequency (RF) heating is a novel thermal stimulation method in developing coalbed methane (CBM). Various research has been conducted on the effect of electromagnetic (EM) heating on the physical properties of coal. However, few studies considered the working conditions of underground coal seam heating. This paper calculates the coal seam temperature distribution based on the coupling between electromagnetic wave propagation and heat transfer in a vertical well to study the influence of coal seam metamorphism and thermoelectric characteristics on temperature distribution. The reservoir thermophysical parameters related to temperature are considered in the heat transfer and wave equations, respectively. Numerical simulations reveal the influence of coal ranks and thermo-electrical properties on heating efficacy. Results indicate that the temperature in the vicinity of the RF heater is relatively high, and the whole heated zone forms an elliptical shape. Low-metamorphism coal, such as lignite, is more functional for RF heating and has a broad heating range, leading to a uniform diffusion coefficient enhancement and good thermal homogeneity. Higher thermal conductivity, lower specific heat capacity, and water saturation can expand the heating area and reduce the temperature near the borehole, benefiting the maintenance of wellbore integrity. The coal seam relative permittivity has little effect on the reservoir temperature when its value is between 2.4 and 6.4.

Background: The present work was conducted to screen the potential biomarkers affecting nasopharyngeal carcinoma (NPC) progression through RNA-sequencing (RNA-seq), bioinformatic analysis and functional experiments. Materials and Methods: Six normal samples and five NPC clinical samples were collected for RNA-seq analysis. The expression levels in both groups were determined through student’s t-test. We identified genes of P < 0.01 as the differentially expressed genes (DEGs). In addition, gene set enrichment analysis (GSEA) was conducted. Afterwards, STRING V10 database was employed to extract protein interactions among the DEGs. Later, we established a protein-protein interaction (PPI) network, and used the Cytoscape software for network visualization. qRT-PCR was conducted to verify hub genes from clinical samples. Then, the function of CXCL10 in cell proliferation, apoptosis, invasion and migration was evaluated. Results: A total of 2024 DEGs were identified, among which, 1449 were down-regulated and 575 were up-regulated. The PPI was constructed, and the hub genes including Insulin Like Growth Factor 1 (IGF1), C-X-C Motif Chemokine Ligand 10 (CXCL10), Interleukin 13 (IL13), Intercellular Adhesion Molecule 1 (ICAM1), G Protein Subunit Gamma Transducin 1 (GNGT1), Matrix Metallopeptidase 1 (MMP1), Neurexin 1 (NRXN1) and Matrix Metallopeptidase 3 (MMP3) were obtained. The expression levels of CXCL10, IGF1, MMP3, MMP1, ICAM1, and IL-13 were significantly up-regulated in tumor tissues. High expression levels of CXCL10, MMP3 and ICAM1 predicted poor prognosis of NPC patients. CXCL10 silencing suppressed NPC cell proliferation and migration. Conclusions: CXCL10 may serve as a potential key gene affecting NPC genesis and progression.

The cationic complex BeOCO+ is produced in a solid neon matrix. Infrared absorption spectroscopic study shows that it has a very high antisymmetric OCO stretching vibration of 2418.9 cm-1, which is about 71 cm-1 blue-shifted from that of free CO2. The quantum chemical calculations are in very good agreement with the experimental observation. Depending on the theoretical method, a linear or quasi-linear structure is predicted for the cation. The analysis of the electronic structure shows that the bonding of Be+ to one oxygen atom induces very little charge migration between the two moieties, but it causes a significant change in the σ-charge distribution that strengthens the terminal C-O bond, leading to the observed blue shift. The bonding analysis reveals that the Be+ ← OCO donation results in strong binding due to the interference of the wave function and a charge polarization within the CO2 fragment and hybridization to Be+ but only negligible charge donation.

The carbon suboxide anion C3O2 − is generated in solid neon matrix. It is characterized by infrared absorption spectroscopy as well as quantum chemical calculations to have a planar C s structure where two CO groups with significantly different bond lengths and angles are attached in a zigzag fashion to the central carbon atom. Bonding analysis indicates that it is best described by the bonding interactions between a neutral CO in a triplet excited state and a doublet excited state of CCO−., The carbon suboxide anion C3O2 − is generated in a solid neon matrix, and is characterized to have an unsymmetrical structure by the bonding interactions between a neutral CO in a triplet excited state and a doublet excited state of CCO−.

The boron atoms react with carbon monoxide and dinitrogen forming the end‐on bonded NNBCO complex in solid neon or in nitrogen matrices. The NNBCO complex rearranges to the (η 2‐N2)BCO isomer with a more activated side‐on bonded dinitrogen ligand upon visible light excitation. (η 2‐N2)BCO and its weakly CO‐coordinated complexes further isomerize to the NBNCO and B(NCO)2 molecules with N−N bond being completely cleaved under UV light irradiation. The geometries, energies and vibrational spectra of the molecules are calculated with quantum chemical methods and the electronic structures are analyzed with charge‐ and energy‐partitioning methods., CO‐induced dinitrogen fixation and cleavage mediated by boron atoms is reported. The experimental and theoretical results show that the N≡N activation processes proceed with the initial formation of an end‐on bonded NNBCO complex, which rearranges to the NBNCO and B(NCO)2 isocyanate complexes via a side‐on bonded (η2‐N2)BCO intermediate. The geometries, energies and vibrational spectra of the molecules are calculated with quantum chemical methods and the electronic structures are analyzed with charge‐ and energy‐partitioning methods.

In this work, we reported a multi-responsive luminescent hydrogel with properties of encryption, naked eye sensing of glucose, shape memory, self-healing, and antibacterial activity. The hydrogel (GA/CCS/DNSA/Eu3+) was obtained by mixing phenylboronic acid-modified gelatin (GA-DBA), catechol-modified carboxymethyl chitosan (CCS-PCA), 3,5-dinitrosalicylic acid (DNSA), and Eu3+ ions through a facile heating-cooling process. The resultant hydrogel exhibits reversible luminescence and color and phase changes in response to temperature, acid/base, salt, and redox stimuli. Based on the multiple responsiveness, information encryption and decryption, naked eye sensing of glucose, remarkable shape memory, and enhanced mechanical properties of the as-prepared hydrogel were realized. In addition, the self-healing capacity was also achieved due to the dynamic bonds in GA/CCS/DNSA/Eu3+ hydrogels. Specifically, the GA/CCS/DNSA/Eu3+ hydrogels possess antibacterial activity owing to the bacteriostasis of the CCS-PCA and DNSA/Eu3+ complex. Thus, GA/CCS/DNSA/Eu3+ hydrogels have potential applications in the fields of anticounterfeiting, wearable devices, biomedicine, sensing, etc.

The CaCO

Packers based on shape memory polymers (SMPs) are an emerging technology that have the advantages of compact structure, easy manufacture, and adaptability to complex wells. This paper proposes a finite element model to simulate the setting process and mechanical response of an SMP packer. The investigated material is an epoxy-based thermal responsive SMP, whose relaxation modulus and thermal expansion coefficient were measured at different temperatures. Based on the experimental data, the model describes the viscoelastic behavior of the SMP using the generalized Maxwell model. The results show that the SMP packer could provide sufficient contact stress under downhole conditions, even after the stress was relaxed. A further parametric study revealed that the most significant factor in sealing effects is the wellbore pressure, followed by the interference between the packer and the annular, the seal length, the pre-compression, and the setting temperature. High downhole pressures require more significant contact stress and increase the risk of slip between the packer and casing wall by promoting shear stress. Increasing the seal length and interference enhances the contact stress and mitigates the shear stress to improve the seal performance. Pre-compression and setting temperatures are minor factors that have little influence on sealability.

Shape memory polymers (SMPs) possess multiple advantages as a sealing element for a packer. The contact stress between the SMP rubber and a casing (or the formation) is an essential indicator in evaluating the sealability of packers. This work conducts a finite element simulation based on the generalized Maxwell viscoelastic model and the time-temperature equivalence (TTE) principle to analyze the contact stress during the setting. The proposed model simulates the mechanical response of the polymer, including the stretch at a high temperature, cooling with a fixed shape, unloading at a low temperature, the shape recovery with reheating, and the stress relaxation. The results show that the contact stress distribution in the middle section of the packer is relatively uniform. The average contact stress is over 7.5 MPa and meets sealing needs. More significant stresses occur at the shoulders of the packer due to stress concentration. Both the shape recovery and the stress relaxation finish fast that it needs about 228.7 s to obtain stable contact stress after shape recovery. This study provides a method to evaluate the performance of the packer based on SMPs.

Wells are often cemented to provide zonal isolation and structural support through their entire service lifetime. Even if a cement sheath is set properly, it may inevitably contain small cracks which tend to propagate under harsh environmental and operational conditions. This work presents a mechanical model to predict the stress intensity factor at a radial crack tip in the cement under high pressure/high temperature (HPHT) conditions. The well section comprised of casing-cement-formation is modeled as three isotropic material domains under plane strain condition. The model calculates the stress field in the well section and estimates the stress intensity factor by a distributed dislocation technique. Two failure factors corresponding to the material strength criterion and fracture propagation criterion are introduced to evaluate the cement integrity. The influence of loading conditions and cement's mechanical and thermal properties on the failure factors is also investigated. The results indicate the predominant failure mode under HPHT conditions. The proposed model provides guidelines for the assessment of cement sheath integrity based on fracture mechanics.

A sensitive spectrophotometric method was developed for the determination of trace-level Co2+ in water based on the acetate enhanced catalytic decolorization of methylene blue (MB) with Co2+ as a catalyst and peroxymonosulfate (PMS) as an oxidizing agent. This indirect spectrophotometric method was easy to operate due to the strong absorption of MB at a maximum absorption wavelength of 664 nm with a molar absorptivity of 5.88 × 104 L mol−1 cm−1. Under the selected reaction conditions of 10.0 mg L−1 MB, 60.0 mg L−1 PMS and 100.0 mg L−1 Ac−, the depletion extent of MB was linearly correlated with the concentration of Co2+ from 0.20 to 7.0 μg L−1 (R2 = 0.986) and then from 7.0 to 50.0 μg L−1 (R2 = 0.991), with a detection limit (3 s/k) of 0.10 μg L−1. It was found that this method possessed excellent anti-interference capability to various coexisting ions including similar transitional metals. The developed method was used to determine the Co2+ concentration in practical samples with satisfactory results.

Micelle-hybridized supramolecular hydrogels were constructed through the self-assembly of gelator N,N-dibenzoyl-L-cystine (DBC) and micelles formed from a Gemini surfactant (G12-8-12). A phosphor, palladium meso-tetra (4-carboxyphenyl) porphyrin (Pd-TCPP) and Al3+ ions were loaded within the hybrid system. Interestingly, the room temperature phosphorescence (RTP) of Pd-TCPP can be efficiently enhanced and modulated by the concentration of Al3+ ions. The enhancement effect could be attributed to the interactions between Al3+ and DBC as well as porphyrin, which verified by 1H NMR analysis. The study of transmission electron microscopy and scanning electron microscopy indicated that a more compact 3D network structure of the gel system was formed upon the addition of Al3+. In addition, measurement of critical micelle concentration indicated that Al3+ ions increase the surface activity of G12-8-12 to promote micelle formation, thereby increasing the dispersion of Pd-TCPP in the hybrid gels. Based on the synergistic effect of these results, the non-radiative transition of Pd-TCPP was efficiently inhibited, resulting in highly efficient RTP. Furthermore, the enhanced RTP of as-prepared gel system shows potential application to detect trace Hg2+ ions because the RTP can be quenched by Hg2+. A linear relationship between RTP against the logarithmic concentration of Hg2+ was found over the range of 6 × 10−8 and 1 × 10−6 mol/L. The detection limit was found to be 0.017 nmol/L.

The cationic complex BeOCO

Cement is one of the primary barriers in a wellbore and critical to well integrity. Radial cracking is a pervasive failure mode in cement due to the temperature and pressure variation during drilling, completion, or production. This work presents a comprehensive analysis of radial cracking in cement under various loading events. The proposed model estimates the stress intensity factor and fracture surface displacement as indicators for crack propagation and opening, respectively, through a distributed dislocation technique. Three types of radial cracks, divided by their tips terminating at the casing–cement interface, inside cement, or at the cement–formation interface, are considered. Based on this model, we conduct a parametric study for radial cracking under typical loading events such as steam injection, CO2 injection, and high-pressure and high-temperature (HPHT) drilling. Results indicate that the crack near the casing–cement interface has an increased risk for steam injection and HPHT drilling, while all three types of radial cracks are destructive during CO2 injection. The thermal expansion coefficient of cement is a significant parameter for steam and CO2 injection wells. The fluid pressure and the cement’s thickness are crucial to radial cracking under HPHT conditions. Stiffer cement could promote crack opening for steam injection but prohibit the crack deformation for CO2 injection or HPHT wells. Thicker cement would accelerate radial cracking under the three loading events. These findings are helpful in designing cement to maintain long-term integrity.

BackgroundHypopharyngeal squamous cell cancer (HSCC) is a head and neck tumor with a poor prognosis. Chemotherapy lacks effectiveness because of multidrug resistance (MDR), which has increased toxic side effects. Thus, there is an urgent need to identify the molecular markers of MDR of chemotherapy for HSCC.MethodsFifty clinical samples of HSCC were derived from patients including 12 sensitive or resistant to chemotherapy drugs. Proteomic screening was performed using liquid chromatography-tandem mass spectrometry (LC-MS), which was based on data-independent acquisition. Molecular markers of MDR of chemotherapy in patients with HSCC were identified with clinical data and validated with ELISA.ResultsA total of 673 differentially expressed proteins were identified in HSCC samples, where 172 were upregulated and 501 were downregulated. A total of 183 differentially expressed proteins including 102 upregulated and 81 downregulated proteins, were identified by comparing cancer sensitive to chemotherapy with cancer resistant to chemotherapy. Clinical HSCC samples had significantly higher expression of FADD and significantly lower expression of RIPK1. Expressions of FADD and RIPK1 proteins were significantly lower in the chemotherapy-sensitive group. These expression differences were not correlated with clinical data. RIPK1 and FADD are involved in necroptosis and the signaling pathway of PRRs. Using ELISA, the low expression of RIPK1 and FADD was found in the patients sensitive to chemotherapy.ConclusionLC-MS proteomics is an effective method to identify the molecular markers of HSCC. FADD and RIPK1 can act as molecular markers of MDR of chemotherapy in patients with HSCC and may function through necroptosis and the PRR signaling pathway.

Extreme downhole conditions often apply a high pressure on tubing or casing that poses a severe challenge to well integrity. Imperfections in these tubular elements are very prone to cause rupture under high pressures. The American Petroleum Institute (API) proposed a method to calculate the rupture pressure for the tubing or casing with radial cracks perpendicular to their inner surface. Stress analysis indicates that an inclined crack would propagate in mixed modes. This study presents an investigation on the stress intensity factor at an oblique fracture initiating from the inner surface of tubing based on finite element methods. The simulation shows that the shear mode would dominate the crack extension as the incline angle increases. Both stress intensity factors in traction and shear modes rise with the pressure inside the tubing. Thicker tubing would mitigate the stress intensity factor. A conservative criterion for crack propagation in mixed modes provides the minimum pressure under which the inclined crack would grow. This criterion also estimates a burst strength factor used for rupture pressure prediction. Results show that the burst strength factor increases firstly and then decreases with the incline angle. Its maximum value reaches 3.2 and occurs at about 20°, which is much higher than the default value by API. This work demonstrates the necessity of considering the crack propagation in mixed modes in rupture failure of tubing.

In this work, the luminescence of lanthanide supramolecular metallogel formed by the self-assembly of 5,5′,5″-(1,3,5-triazine-2,4,6-triyl)tris(azanediyl)triisophthalate (H6L) and Tb3+ was efficiently promoted by carboxymethyl chitosan (CMCS). The total quantum yield of the resultant metallogel (denoted as H6L/Tb3+/CMCS gel) was 9 times higher than the gel without CMCS. The average lifetime of H6L/Tb3+/CMCS gel increased from 0.51 ms to 1.20 ms. More importantly, the aqueous dispersion of H6L/Tb3+/CMCS xerogels showed a stable and pH-dependent luminescence. Based on the selective affinity of CMCS to different metal ions as well as with the aid of principal component analysis, H6L/Tb3+ /CMCS can be used as a sensor array to distinguish 11 metal ions (P

Sulfonyl azide isocyanate, (OCN)S(O)2N3, was prepared and characterized by IR (gas, matrix-isolation), Raman (liquid), and UV-vis spectroscopy. Upon flash vacuum pyrolysis (FVP) at ca. 1000 K, gaseous (OCN)S(O)2N3 decomposes completely and yields fragments N2, SO2, SO3, NCN, N3, NCO, CO, CN, and NO. In contrast, the azide splits off N2 and furnishes a transient triplet sulfonyl nitrene intermediate (OCN)S(O)2N upon a 266 nm laser irradiation in solid Ne-matrix at 2.8 K. Subsequent photolysis of the nitrene with visible light (λ = 380-450 nm) results in oxygen-shifted Curtius rearrangement to a novel nitroso sulfoxide (OCN)S(O)NO. For comparison, the photodecomposition of the closely related sulfonyl diazide O2S(N3)2 in a solid Ar matrix was also studied. Upon an ArF excimer laser (193 nm) photolysis, O2S(N3)2 decomposes and yields N2, SO2, and OSNNO via the intermediacy of an elusive sufonyl nitrene N3S(O)2N. Further visible light irradiation (λ > 395 nm) leads to depletion of N3S(O)2N and OSNNO and concomitant formation of SO2 and N2. The identification of the intermediates in cryogenic matrixes by IR spectroscopy was supported by 15N-labeling experiments and quantum chemical calculations. The mechanism for the decomposition of both sulfonyl azides (OCN)S(O)2N3 and O2S(N3)2 was discussed on the basis of the observed intermediates and the calculated potential energy profiles.

The simplest aminosulfinyl radical H2 NSO has been generated in the gas phase through flash vacuum pyrolysis of CF3 S(O)NH2 at approximately 1000 K. Upon UV light irradiation (365 nm), 1,3-H migration occurs in H2 NSO and furnishes an elusive N-amidyl radical HNSOH in syn and anti conformations in cryogenic matrices (N2 or Ar, 15 K). Further 266 nm laser irradiation results in dissociation of HNSOH to H2 O and SN and concomitant reformation of H2 NSO in trace amount. The identification of H2 NSO, syn-HNSOH, and anti-HNSOH by matrix-isolation IR spectroscopy is supported by high-level quantum chemical computations.

Fibrous materials, such as cellulose papers, fibres, or textiles, are regarded as potential evaporation materials used in evaporative cooling systems. The fibrous material’s wettability and evaporation characteristic have significant influences on heat and mass transfer performance of evaporative cooling systems. This paper studied the wicking performance of selected fibrous materials including cellulose/PET fibre, Coolmax fabric and wood pulp paper by numerical modelling and dedicated experiment based on transient weight and optical measurements. The effect of evaporation on the performance of wicking rise were analysed in depth using the obtained experimental data. The measured data show good agreements with the predicted results, within ± 6.67%, 7.47% and 3.78% errors for the three types of materials, respectively. The microstructure parameters that control water diffusion performance of porous materials, i.e., permeability to effective pore radius ratio, were found to be highest for cellulose/PET fibre followed by Coolmax. Additionally, the study compared water evaporation rate of the selected materials by a few validated preliminary tests operating under various ambient air velocities and surface temperatures. Coolmax and cellulose/PET fibres were found to have similar higher evaporation rate than wood pulp paper. This paper presented numerical and experimental approaches for accurately characterising and differentiating wicking and evaporation performance of fibrous materials which would contribute to optimise evaporation materials for evaporative cooling systems.

Recently there has been growing interest in regenerative evaporative coolers (REC), which can reduce the temperature of the supply air to below the wet-bulb of intake air and approach its dew-point. In this paper, we designed, fabricated and experimentally tested a counter-flow REC in laboratory. The REC’s core heat and mass exchanger was fabricated using stacked sheets composed of high wicking evaporation (wickability of available materials was measured) and waterproof aluminium materials. The developed REC system has a much higher cooling performance compared to conventional indirect evaporative cooler. However, the decision to use the REC for China buildings depends on a dedicated evaluation of the net energy saved against the capital expended. Such an evaluation requires the hourly-based data on the availability of cooling capacity provided by the REC for various climates. The paper used an experiment-based method to estimate the cooling capacity and energy savings provided by the proposed REC for China’s various climates. By using the experimental results and regional hourly-based weather data, the energy saving potential of the REC against an equivalent-sized mechanical air conditioner alone was analysed. The results indicate that, for all selected regions, the REC could reduce 53–100% of cooling load and 13–58% of electrical energy consumption annually.

In this work, we consider the diffusion mechanisms for different metal elements during oxidation and extend the stress–diffusion coupled model for stress-aided grain boundary oxidation ahead of cracks (Evans et al. in Scr Mater 69:179–182, 2013) to a more general situation including both outward and inward diffusion at the crack tip during oxidation. The analyses show that the transformation stress generated due to oxide formation near the crack tip could in principle promote the growth of Cr2O3 oxide at the crack tip in the intrusion direction but has no enhancement effect on NiO oxide in the extrusion direction with respect to the original position of the crack tip.

There remains a significant need for developing new photocatalytic system to degrade perfluorooctanoic acid (PFOA), a typical persistent organic pollutant. In this study, highly efficient BiOCl nanosheets were prepared by a simple hydrolytic method and employed to decompose PFOA. The UV irradiation BiOCl system decomposed nearly all the added PFOA after 12 h, yielding a defluorination of 59.3% and a minimization ratio of 52.5%. The photocatalytic defluorination rate constant of PFOA on BiOCl was 16.53 μmol L −1 h −1 , being 1.7 and 14.6 times higher than that on commercial In 2 O 3 and TiO 2 (P25), respectively. It was demonstrated the photocatalytic degradation of PFOA on BiOCl mainly followed the direct hole-induced oxidative pathway, and the PFOA degradation was positively correlated with the amount of oxygen vacancies in BiOCl. The oxygen vacancies not only acted as the electron scavengers to suppress the charge recombination, but also favored to bind PFOA tightly on the BiOCl surface through a special monodentate coordination, which is beneficial for the hole oxidation of PFOA.

A new strategy for the facile access to multi-functionalized benzofurans and 4,5-dihydrobenzofurans has been explored. The advantages of the present protocol include readily obtainable starting materials, mild and metal-free conditions, expedient and practical processes, excellent yields, and easy scale-up. The reaction demonstrated high efficiency to construct two rings in a single step. The zwitterionic intermediate generated from the conjugated attack of PPh3 to the ene-yne-ketone was proposed to be the key intermediate toward these valuable scaffolds.

Preparing luminescence-stable lanthanide materials in a facile manner has always been an intriguing challenge. Herein we report an easy approach to the preparation of a heat-set lanthanide-based metallogel (H6L/Tb gel) with stable luminescence from 5,5',5''-(1,3,5-triazine-2,4,6-triyl)tris(azanediyl) triisophthalate (H6L) as a Tb3+ coordinating ligand. The heat-set H6L/Tb gel exhibits luminescence that mostly retains its intensity in the 0-90 °C temperature range and under mechanical stimulus. In addition, the H6L/Tb xerogel is also luminescent in aqueous solution. UV-vis and FT-IR spectroscopy and XRD studies reveal that the stable luminescence of the H6L/Tb gel depends on heat-set-induced strong hydrogen bonding, π-π stacking, and metal-ligand interactions. This study provides a heat-set approach to the preparation of luminescence-stable metallogel materials, such metallogels are potentially useful in anti-counterfeiting and sensing fields, among others.

The analysis of siliceous matrix samples may adopt a two-step pretreatment, which includes melting with ammonium hydrogen fluoride and redissolving with nitric acid. However, the residual of substrate silicon unfavorable to the determination of trace elements in the samples due to serious matrix effects. Here, a new digestion method using simultaneously both ammonium bifluoride and nitric acid under normal pressure was developed for high-purity quartz sand sample. The digestion pretreatment is a two step process: melting/dissolving with both ammonium bifluoride and nitric acid at 200 °C for 2 h, and evaporating the solution at 250 °C to dryness. As confirmed by XRD analysis, silicates in the sample were converted to (NH4)3SiF6NO3 in the melting/dissolving step. TGA analysis shows that the generated (NH4)3SiF6NO3 could be decomposed and evaporated completely at 250 °C, which ensured a complete removal of silicon by the followed evaporation of the solution at 250 °C. As a result, the followed ICP-OES and ICP-MS analysis needed a solution dilution of only 100 times for the determination of Ca, Mg, Al, Rb, Ba, REE and other trace elements. The new method was applied to the analysis of three certified reference materials, and the results were well consistent with the standard value with RSD% values between 0.62% and 9.73%. Therefore, this method can be applied to the analysis of trace elements in high purity silica-based samples, with the advantages of time-saving, small dilution factor (only 100 times) and low detection limit.

In this work, rare minnow (Gobiocypris rarus) was applied as a sentinel organism and set in cages at control and test sampling sites in Donghu Lake for 4 weeks in March, June, September, and December 2016 to assess the biological toxicity of in situ water. Sampling for active biomonitoring and physicochemical variables was performed weekly. The control was obtained from the outdoor pool of the Institute of Hydrobiology, China. Superoxide dismutase, lipoperoxidation, metallothioneins, acetylcholinesterase activity, and Vtg mRNA expression were determined as biomarkers during the field exposure period. Survival and growth also were monitored to evaluate the overall physiological condition of the fish. The seasonal changes of organic pollutants and trace metals (As, Hg, Cr, Cu, Zn, Cd, Pb) in surface water were determined. The integrated biomarker response (IBR) index was applied to summarize biomarker responses and correlate stress levels with concentrations of organic pollutants and trace metals in the surface water. Results indicated that complex pollution by persistent organic pollutants and heavy metals was present in Donghu Lake and that the in situ exposed organisms were stressed. Moreover, the complex pollution of Donghu Lake in summer and autumn was more serious than that in spring and winter. Active biomonitoring combined with IBR analysis enabled good discrimination among different exposure seasons. The proposed protocol with caged rare minnow revealed marked biological effects caused by the investigated Lake and a useful approach that can easily be extended to monitor water pollution.

Carbon capture and sequestration (CCS) is one of the most promising technologies to mitigate greenhouse gas levels. To ensure an effective underground storage, well integrity is critical to isolating the injected fluid between different zones or back to the surface. Among the wellbore components, the cement sheath is the most important sealing element for zonal isolation. However, cement is vulnerable and prone to cracking that may provide leakage pathways for CO2. Both laboratory study and field test show that thermal stresses caused by the temperature variation in the wellbore are a major factor for the mechanical integrity loss of cement. This work focuses on the mechanical response of the casing-cement-formation section above the injection zone. We firstly propose a wellbore flow model to predict the temperature distribution along the well depth. Then we calculate the induced stress in cement during injection by a finite element simulation. To identify the cement failure mode, we introduce failure factors by the Mogi-Coulomb criterion, tensile strength and interfacial strength corresponding to shear compressive failure, radial cracking and debonding at the casing/cement or cement/formation interfaces, respectively. A parametric study is conducted to investigate the influence of the injection temperature and rate as well as casing eccentricity on failure factors. The results show that radical cracking and debonding at the cement/formation interface are the main failure modes during CO2 injection. Both the two failure factors would increase linearly as the injection temperature decreases while they grow non-linearly with the injection rate. In addition, the casing eccentricity exacerbates the risk of cement integrity loss by increasing failure factors. This study provides a failure assessment of CO2 geological sequestration and guidelines for injection operations.

The development of reversible redox supramolecular gels capable of concurrent luminescence switch and visible color change with the facile redox process has always been an intriguing challenge. A redox-responsive supramolecular lanthanide metallogel with strong luminescence and yellow color is obtained via coordination interaction between 3,5-dinitrosalicylic acid (DNSA) and europium (Eu

Elevated As(III) and Fe(II) in shallow reducing groundwater can be frequently re-oxidized by introducing O2 due to natural/anthropogenic processes, thus leading to oxidative precipitation of As as well as Fe. Nevertheless, the geochemical process may be impacted by co-existing engineered black carbon due to its considerable applications, which remains poorly understood. Taking rice husk-derived biochar prepared at 500 °C as an example, we explored its impact on the process particularly for the As(III) oxidation and (im)mobilization during the oxygenation. The presence of the biochar had a negligible effect on the As(III) oxidation and immobilization extents within 1 d, while accelerating their rates. However, the immobilized As(III) was significantly liberated from the formed Fe(III) minerals afterward within 21 d, which was 2.2-fold higher than that in the absence of the biochar. The enhanced As(III) liberation was attributed to the presence of the surface silicon-carbon structure, consisting of the outer silicon and inner carbon layers, of the rice husk-derived biochar. The outer silicon components, particularly for the dissolved silicate primarily promoted the As(III) release via ligand exchange, while significantly impeding the transformation of ferrihydrite to lepidocrocite and goethite still resulted secondarily in the As(III) release. Our findings reveal the possible impact of biochar on the environmental behavior and fate of As(III) in the Fe(II)-rich groundwater during the oxygenation. This work highlights that biochar, particularly for its structural features should be a concern in re-mobilizing As in such scenarios when the oxygenation time reaches several days or weeks.

The present work investigated the mechanochemical (MC) treatment of powdery decabromodiphenyl ether (BDE209) with Bi2O3 and/or Fe powders as co-milling reagents. The simultaneous use of Bi2O3 and Fe with a Bi:Fe:Br molar ratio of 1:1:1 led to a BDE209 degradation of 96.6% within 2 h of ball milling at rotation speed of 400 rpm, whereas only 66.0% and 24.0% of BDE209 was removed in the MC-Bi2O3 and MC-Fe system, respectively. It was demonstrated that the MC process activated the lattice oxygen (O2−) of Bi2O3 and promoted its reaction with BDE209, whereas Fe initiated the reduction of BDE209. The MC treatment of BDE209 through a single reductive in the MC-Fe system or oxidative process in the MC-Bi2O3 system was not efficient, due to that BDE209 is rather difficultly oxidized and the debrominated intermediates are resistant to reduction. When combining Bi2O3 with Fe, the reductive debromination of BDE209 over Fe and the subsequent oxidation of debrominated products over Bi2O3 were integrated into a concerted process. The rapid reduction of BDE209 over Fe not only released Br− ions, which acted as the dopant to improve the activity of O2− in Bi2O3, but also generated less brominated intermediates, which were more susceptible to the O2−-participating reaction over Bi2O3. Thus, a strong synergistic effect between Bi2O3 and Fe was observed on the MC degradation of BDE209.

The thermal-decomposition and photo-decomposition of benzenesulfonyl azide, PhS(O)2N3, have been studied by combining matrix-isolation IR spectroscopy and quantum chemical calculations. Upon flash vacuum pyrolysis at 800 K, the azide splits off molecular nitrogen and exclusively furnishes phenylnitrene (PhN) and SO2 in the gas phase. In contrast, the azide favors stepwise photodecomposition in solid Ar and Ne matrices at 2.8 K. Specifically, the UV laser photolysis (193 and 266 nm) of PhS(O)2N3 results in the formation of the key nitrene intermediate PhS(O)2N in the triplet ground state, which undergoes pseudo-Curtius rearrangement into N-sulfonyl imine PhNSO2 under subsequent visible light irradiation (380–450 nm). Further fragmentation of PhNSO2 into SO2 and PhN followed by ring-expansion to didehydroazepine also occurs upon visible light irradiation. The preference of the stepwise mechanism for the decomposition of PhS(O)2N3 is supported by quantum chemical calculations using DFT B3LYP/6-311++G(3df,3pd) and CBS-QB3 methods.

A biologically relevant reactive sulfur species (RSS), the hypothiocyanite radical OSCN, is generated in the gas phase through flash vacuum pyrolysis (FVP) of trifluoromethyl sulfinyl cyanide CF3S(O)CN at ca. 1000 K. Upon UV light irradiation (365 nm), OSCN rearranges to novel isomers OSNC and SOCN, and further visible light irradiation (400 ± 20 nm) leads to reverse isomerization. The identification of OSCN, OSNC, and SOCN in cryogenic matrices (Ar and N2, 2.8 K) with IR spectroscopy is supported by quantum chemical calculations up to the CCSD(T)-F12/VTZ-F12 level. The potential energy surface for the interconversion of OSCN isomers and their bonding properties are computationally explored by using the CCSD(T)-F12/VTZ-F12 and EDA-NOCV methods, respectively.

Scanning probe microscopy (SPM) equipped in high temperature nanoindentation instrument is adopted to in situ characterize the oxide film growth on Ni-base single crystal at nanoscale. SPM images reveal a transition of oxide film configuration that the originally flat surface roughens during oxidation. Based on the stress-diffusion coupling effect during oxidation, the stress evolution in the oxide film and the evolution of surface configuration are analyzed. A new method to infer the critical stress in the oxide film at the transition point is proposed by measuring the undulated surface wavelength based on the surface morphology obtained by SPM.

A highly stereoselective sequential annulation reaction between γ-substituted allenoates and ketimines was reported. By using bifunctional N-acyl aminophosphine catalysts, poly-heterocycle rings were obtained with high stereocontrol in good to excellent yields. The desired products have four contiguous stereogenic centers (one quaternary and three tertiary carbon centers), and only one isomer was obtained in all reactions.

This paper aims to investigate the operational performance and impact factors of a counter-flow regenerative evaporative cooler (REC). This was undertaken through a dedicated experimental process. Temperature, humidity and flow rate of the air flows at the inlet, outlet and exhaust opening of the cooler were tested under various operational conditions, i.e., different inlet air conditions, feed water temperature and evaporation rate were also correspondingly measured. It was found that the wet-bulb effectiveness of the presented cooler ranged from 0.55 to 1.06 with Energy Efficiency Ratio (EER) rated from 2.8 to 15.5. The major experimental results were summarised below: 1) the wet-bulb effectiveness was significantly enhanced through either ways of increasing inlet wet-bulb depression or reducing intake air velocity, or alternatively by increasing working-to-intake air ratio; 2) the cooling capacity and EER of cooler was rapidly increased by means of increasing inlet wet-bulb depression or increasing intake air velocity, or reducing working-to-intake air ratio instead; 3) the effectiveness reduced by less 5% while feed water temperature increased from 18.9 to 23.1 °C; 4) apparent acceleration in water evaporation rate was gained from increasing inlet wet-bulb depression or air velocity. The presented cooler showed 31% increase in wet-bulb effectiveness and 40% growth in EER compared to conventional indirect evaporative cooler. The research helped identifying the performance of a new REC with enhanced performance and thus contributed to development of energy efficient air conditioning technologies, which eventually lead to significant energy saving and carbon emissions reduction in air conditioning sector.

Stress-diffusion coupling effects during oxidation have attracted extensive attention. In this work, an analytical model is developed for oxidation kinetics and stress evolution considering stress-diffusion coupling effects for three-point bending tests under high temperature. With the oxide thickening, growth strain can be generated and induces compressive stress in the oxide. The total stress in the oxide is estimated by superimposing the stress caused by oxidation and the applied load. The oxidation kinetics and stress evolution at typical locations where maximum tensile or compressive stress occurs are discussed. The theoretical analysis reveals that tensile stress accelerates the oxidation rate, while compressive stress would decelerate it. The model prediction for the parabolic rate constant of the oxidation kinetics is consistent with experimental observation, which validates this analysis. In addition, the influence of the applied load on oxidation kinetics is investigated.

Carbon capture and storage (CCS) projects inject large amounts of CO2 into deep saline aquifers or depleted oil and gas reservoirs. This operation requires a leakage risk analysis for the injected CO2. The subsurface flow of CO2 at the injection formation is dependent on injection operations. This study proposes a method to combine a wellbore flow model and an analytical solution to the CO2 plume to investigate the influence of the injection temperature, pressure, and rate on the interface evolution between the CO2 and the brine. Using the wellbore flow model, the proposed mothed estimates the volume injection rate at the bottom hole under different injection parameters. Then it illustrates the effects of injection operations on the CO2 plume and its maximum radius at the interface between the caprock and formation. The results provide an estimation of the plume radius under different injection rate and duration that would help field operators manage leakage risks.

A facile fabrication strategy of fluorescence-phosphorescence dual emissive materials based on the supramolecular gels was proposed in this work. In comparison with complicated fabrication of conversional dual emissive materials, supramolecular gels are formed just through a simple heating and cooling of solution containing a gelator and phosphor. The gel system is pure organic without any metal ions. Herein, the self-assembly of gelator N, N-dibenzoyl- l -cystine (DBC) resulted in the formation of gel system. The phosphor 3,5-Dibromoquinoline (BrQ) entrapped in the gels endowed gels with fluorescence-phosphorescence dual emission. Upon 315 nm UV irradiation, strong room temperature fluorescence and phosphorescence emission were observed at 367 and 550 nm, respectively. The ability of dual emission at room temperature could be attributed to the ordered microstructure of the supramolecular gels, effectively avoiding the non-radiative transition of BrQ. In addition, the gel system exhibited environmental responsiveness including thermal, pH and redox response due to the structural feature of DBC gels. The dual emission can be tuned by this responsiveness. Particularly, the deoxygenation of gel system is not required. Conversely, the dissolved oxygen in the system can be employed for redox reaction without the addition of any other oxidant.

It is urgently needed to develop highly efficient and selective adsorbents for enrichment and separation of Re(VII) from Mo(VI) to obtain metallic rhenium. By tuning cross-link of chitosan, ionic gel capsules (CSN) were prepared, which had a core-shell structure and wrapped N263 (methyl trioctyl ammonium chloride) as an extractant. After being characterized, the CSN capsules were used as a green adsorbent for separation of ReO4− from MoO42−. It was found that the gel yielded good adsorption capacities for Re(VII) in a wide pH range from pH 2 to 12. The adsorption of Re(VII) on the gel followed the Langmuir model, exhibiting a maximum adsorption capacity of 222 mg g−1 for Re. The adsorbent showed good adsorption capacities for Mo(VI) at pH 3.5. Therefore, the enrichment and separation of Re(VII) from Mo(VI) could be easily achieved by using the gel adsorbent in a wide pH range from 4 to 12, showing a separation factor βRe/Mo with values of 103–5 × 104. A mechanism was proposed for the selective adsorption of Re(VII). The extractant N263 wrapped in the capsule core provides excellent extractive adsorption ability for Re(VII) through ion association extraction, generating ion association complex R4N+∙ReO4− in the adsorbent. The gel shell was composed of cross-linked chitosan induced by sodium tripolyphosphate, and functioned as a blocking layer for the adsorption of Mo(VI), being possibly related to a special interaction between Mo and P as observed in the formation of phosphorus molybdenum heteropolyacid and/or the crosslinking with Mo and chitosan. The CSN gel was successfully applied to separate ReO4− from a practical alkaline solution.