Search

ispartof: SEPARATION AND PURIFICATION TECHNOLOGY vol:313 status: accepted

Poly(phenylene sulfide benzimidazole) has been synthesized and tested as a potential material for high-temperature proton transport. A high content of sulfide bonds has been implemented in the polymer chains to endow a high antioxidant capacity and, in combination with bulky benzimidazole pendant units, to significantly suppress crystallinity and thereby improve the solubility in highly polar aprotic solvents. The amorphous polymer has high thermal stability and high glass transition temperature (Tg). Freestanding, insoluble, and robust membranes were obtained via thermal cross-linking of the benzimidazole moieties with octa-glycidyl polyhedral oligomeric silsesquioxane (g-POSS). The series of hybrid networks (cPPSBi_X, with X being the g-POSS content wt %) showed excellent oxidative stability, with cPPSBi_15 having weight loss lower than 5% after 264 h in Fenton's reagent at 80 °C. Elastic moduli as high as 868 MPa with reduced strain at break (1.8%) were obtained. After doping the membranes with phosphoric acid, proton conductivity in the range of 2.3 × 10-2 S cm-1 at 180 °C was obtained, and the membranes show a stress at break of 2.3 MPa. Dimensional and mechanical stability were maintained also at high doping levels thanks to the inclusion of g-POSS which provides the resulting hybrid networks with increased free volume and high cross-link density. more...

Organocatalysts are increasingly gaining attention for the ring opening polymerization (ROP) of lactones due to numerous advantages. In this work, the goal is to expand the scope of catalysts for the ROP of alkyl substituted caprolactones: a mixture of beta,delta-trimethyl-epsilon-caprolactones (TMCL). Several organocatalysts were evaluated, with a focus on bifunctional organophosphorus catalysts including two novel categories, namely phosphonic acids and phosphinic acids. The effects of initial monomer concentration, temperature, catalyst loading and catalyst type on the monomer conversion at equilibrium and the reaction kinetics were addressed. The ceiling temperature of TMCL is 302 degrees C in bulk and 34 degrees C at 1 M, as determined experimentally. During polymerization, higher conversion and reaction rates were observed for the most substituted lactone ( proximal lactone). This difference of reactivity between the two regio-isomeric lactones was greater for lower reaction temperatures. Density functional theory (DFT) calculations on the ring opening of the lactones demonstrated that the difference of reactivity can be attributed to a lower enthalpic contribution of the proximal lactone making the ring opening of this lactone more energetically favored. The difference in calculated Gibbs free energy was found to increase with lower temperature. more...

The use of calcined clays as supplementary cementitious materials provides the opportunity to significantly reduce the cement industry’s carbon burden; however, use at a global scale requires a deep understanding of the extraction and processing of the clays to be used, which will uncover routes to optimise their reactivity. This will enable increased usage of calcined clays as cement replacements, further improving the sustainability of concretes produced with them. Existing technologies can be adopted to produce calcined clays at an industrial scale in many regions around the world. This paper, produced by RILEM TC 282-CCL on calcined clays as supplementary cementitious materials (working group 2), focuses on the production of calcined clays, presents an overview of clay mining, and assesses the current state of the art in clay calcination technology, covering the most relevant aspects from the clay deposit to the factory gate. The energetics and associated carbon footprint of the calcination process are also discussed, and an outlook on clay calcination is presented, discussing the technological advancements required to fulfil future global demand for this material in sustainable infrastructure development. more...

(1) Objective: The aim of this study was to compare the demineralization around brackets bonded with different types of adhesive agents in a cariogenic suspension environment. (2) Methods: In the study, 60 extracted upper first premolar teeth were divided into three groups with 20 teeth in each group. In Group 1, Transbond XT Primer + Transbond XT Light Cure Adhesive (3M Unitek, Monrovia, CA, USA), in Group 2, GC Ortho Connect Light Cure Adhesive (GC Crop, Tokyo, Japan) and in Group 3, Transbond™ Plus Self Etching Primer + Transbond XT Light Cure Adhesive (3M Unitek, Monrovia, CA, USA) adhesive agents were used. In Group 1 and 2, buccal enamel surfaces were etched for 30 s, washed for 15 s and dried for 15 s. All groups were bonded with Gemini metal (3M Unitek, Monrovia, CA, USA) brackets. Gingival, occlusal and proximal enamel surfaces of the brackets were measured with a DIAGNOdent pen (KaVo, Biberach, Germany), and demineralization values were recorded. Measurements were performed after bracketing (T0) and after 28 days in a cariogenic environment (T1), which was renewed every 48 h. The Kolmogorov–Smirnov test was used to determine whether or not the data were homogeneously distributed, the Wilcoxon test was used for comparisons within groups, and the Mann–Whitney U and Kruskal–Wallis tests were used for comparisons between groups. (3) Results: In all groups, demineralization values on all enamel surfaces of the brackets were found to be statistically significantly higher in the T1 period than in the T0 period (p < 0.05). In the T1 period, demineralization values of occlusal enamel surfaces in Groups 1 and 2 were found to be significantly higher than in Group 3 (p < 0.05). The amount of increase in occlusal enamel surface demineralization value between T0 and T1 periods in Groups 1 and 2 was significantly higher than in Group 3 (p < 0.05). There was no statistically significant difference in demineralization values of proximal and gingival enamel surfaces between the groups in the T1 period (p > 0.05). (4) Conclusion: Significantly less occlusal enamel surface demineralization was observed in teeth in which the Transbond™ Plus Self Etching Primer adhesive agent was not applied with acid etching. more...

An alkaline-earth metal catalytic system for environmentally benign allylic alkylation was developed. Allylic alcohols can be utilized directly at room temperature in this transition-metal-free process, producing water as the only byproduct. A variety of allylic compounds, including the ones containing all-carbonyl quaternary centers, can be obtained with high yields. Ministry of Education (MOE) We gratefully acknowledge the financial support from the National Natural Science Foundation of China (21702108), the Natural Science Foundation of Jiangsu Province, China (BK20160977), the Six Talent Peaks Project in Jiangsu Province (YY-033), the grant from Ministry of Education of Singapore MOE2016-T1-002-043 (RG111/16), and Nanjing Tech University (39837101). more...

Inan, Suleyman/0000-0003-4185-0979, WOS: 000504534100001, The recovery of rare earth is an essential problem from scientific and technological point of view. in this study, we focused on sorption of trivalent lanthanides using D2EHPA-impregnated XAD7 resin. the solvent-impregnated resin was characterized by SEM, FT-IR, TGA-DSC and surface-area and porosity. the factors influencing the distribution of metals, such as extractant loading ratio, pH, shaking time and ratio of the solution volume to the sorbent amount were investigated. the remarkable K-d difference between Gd and La was achieved at pH 1 and 20% loading ratio., TUBITAK (Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [115M527]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK), This research was financially supported by TUBITAK (Scientific and Technological Research Council of Turkey, Project No: 115M527). the authors would like to thank TUBITAK for funding the project. more...

The lanthanides (Ln) are an essential part of many advanced technologies. Our societal transformation toward renewable energy drives their ever-growing demand. The similar chemical properties of the Ln pose fundamental difficulties in separating them from each other, yet high purity elements are crucial for specific applications. Here, we propose an intralanthanide separation method utilizing a group of titanium(IV) butyl phosphate coordination polymers as solid-phase extractants. These materials are characterized, and they contain layered structures directed by the hydrophobic interaction of the alkyl chains. The selective Ln uptake results from the transmetalation reaction (framework metal cation exchange), where the titanium(IV) serves as sacrificial coordination centers. The “tetrad effect” is observed from a dilute Ln3+ mixture. However, smaller Ln3+ ions are preferentially extracted in competitive binary separation models between adjacent Ln pairs. The intralanthanide ion-exchange selectivity arises synergistically from the coordination and steric strain preferences, both of which follow the reversed Ln contraction order. A one-step aqueous separation of neodymium (Nd) and dysprosium (Dy) is quantitatively achievable by simply controlling the solution pH in a batch mode, translating into a separation factor of greater than 2000 and 99.1% molar purity of Dy in the solid phase. Coordination polymers provide a versatile platform for further exploring selective Ln separation processes via the transmetalation process. more...

RATIONALE For clumped isotope analysis (Δ47 ), hydrocarbon and organic molecules present an important contaminant that cannot always be removed by CO2 purification through a Porapak-Q trap. Low-temperature oxygen plasma ashing (OPA) is a quick and easy approach for treatment; however, the impact of this treatment on the original carbonate clumped isotope values has never been fully studied. METHODS We tested the isotopic impact of OPA using three natural samples with a large range of initial Δ47 values. Crushed and sieved (125 μm mesh) samples were placed into a Henniker Plasma HPT-100 plasma system and treated at a flow rate of 46 mL/min and a power of 100 W at a vacuum of 0.2 mbar for 10, 20, 30 and 60 min before clumped isotope analysis using two MAT 253 isotope ratio mass spectrometers modified to measure masses 44-49. RESULTS OPA treatment for 30 min or more on calcite powder samples has the potential to alter the clumped isotopic composition of the samples beyond analytical error. A systematic positive offset is observed in all samples. The magnitude of this alteration translates to a temperature offset from known values ranging from 4°C to 13°C. We postulate that the observed positive offset in Δ47 occurs because the bonds within lighter isotopologues are preferentially broken by plasma treatment, leading to an artificial increase in the 'clumping' value of the sample. CONCLUSIONS We recommend that any laboratory performing OPA treatments should reduce the runs to 10-20 min or carry out successive runs of 10 min followed by sample stirring, as this procedure showed no alteration in the initial Δ47 values. Our results validate the use of OPA for clumped isotope applications and will allow future research to use clumped isotopes for challenging samples such as oil-stained carbonates, bituminous shales or host rocks with very high organic carbon content. more...

OBJECTIVE: Enamel bond durability of three new alternative etchants combined with three representative adhesives was determined. METHODS: The 'immediate' and 'aged' micro-tensile bond strength (μTBS) of the 3-step etch&rinse adhesive OptiBond FL ('O-FL', Kerr), 2-step self-etch (SE) adhesive Clearfil SE Bond 2 ('C-SE2', Kuraray Noritake) and universal adhesive Adhese Universal ('ADU', Ivoclar Vivadent) were measured when bonded to enamel following either a proprietary organic acid-containing Enamel Conditioner ('EC', Shofu), a phosphoric-acid monomer-containing Multi Etchant ('ME', Yamakin: 10-methacryloyloxy tetraethylene glycol dihydrogenphosphate or MTEGP), or a metal salt-based ZON etchant ('ZON', Ivoclar Vivadent: ZrO(NO3)2). All alternative etchants were used in replacement of phosphoric acid, the latter (K-Etchant, Kuraray Noritake) also used with O-FL and ADU, in addition to C-SE2 that was solely used in SE mode (controls). The enamel-etching patterns and de-bonded fracture surfaces were examined by SEM, while the interfaces with enamel were ultra-morphologically characterized by TEM. RESULTS: No statistically significant difference in immediate and aged μTBS, obtained by combining the three alternative etchants with the three adhesives, was recorded as compared with the respective controls, except for ME combined with O-FL. Upon aging, significant reduction in μTBS was recorded for the ME/C-SE2 and ME/ADU combinations. The percentage of adhesive failures increased with aging. SEM revealed similar etching patterns produced by EC and ZON as by classic phosphoric-acid etching, for which also numerous micro-resin tags at the adhesive-enamel interface were disclosed. SIGNIFICANCE: Durable bonding to enamel was generally obtained for all etchant/adhesive combinations with the exception of the ME/O-FL combination. ispartof: DENTAL MATERIALS vol:35 issue:10 pages:1415-1429 ispartof: location:England status: published more...

Mechanistic insights gained through density functional theory (DFT M06 and B3LYP) computations on a three-component cooperative asymmetric catalytic reaction between a diazo ester, a carbamate, and an imine, catalyzed by dirhodium acetate and chiral phosphoric acid (Bronsted acid), are presented. The addition of the dirhodium-bound enol to the imine yielding an alpha,beta-diamino ester is energetically more preferred over a potentially competitive protonation of the same enol leading to an alpha-amino ester. more...

Much debate exists on the extent to which early dolomites recrystallize and preserve the signature of their primary diagenetic setting. Here, we combine clumped isotopes thermometry with X-ray diffraction and thin section petrography to study dolomite recrystallization under shallow burial ( more...

This work aims to study an aluminosilicate phosphate cementitious matrix. The cementitious matrix was studied on paste samples. The synthesis of metakaolinite phosphate cement (MKPC) was investigated using calorimetric techniques. A systematic study was performed by emphasizing a broad range of Al/P molar ratios, covering the different behavior of the material to the extremes, as well as the optimum composition. X-ray diffraction and scanning electron microscopy revealed that the final structure was mainly an amorphous network, albeit with some non-reacted phases. The compressive strength was studied on mortars using a cement/sand ratio of 1:3. MKPC specimens with Al/P ratios close to 1/1 showed optimal behavior. MKPCs with Al/P ratios above 1/1 were characterized by high porosity and low strength, whereas MKPCs with Al/P &lt, 1 contained an excess of phosphates. The influence of the Al/P molar ratio on compressive strength was also studied, reaching a maximum of 68 MPa for the optimum composition. Based on the results, MKPC may be a promising candidate for construction purposes. more...

Diffusing wave spectroscopy (DWS) is a powerful optical technique suitable to investigate turbid samples in a nondestructive and reproducible way, providing information on the static and dynamic properties of the system. This includes the relative displacement of emulsion droplets over time and changes in the viscoelastic properties. Here, novel and promising cellulose-based oil-in-water (O/W) emulsions were prepared and studied, for the first time, by DWS. Cellulose plays the role of a novel eco-friendly emulsifying agent. The hydrolysis time of cellulose was observed to affect the average size of the emulsion droplets and their stability; the longer the hydrolysis time, the more dispersed and stable the emulsions were found to be. Additionally, a good complementarity between the microrheology (DWS) and macrorheology (mechanical rheometer) data was found. Our work suggests that DWS is a highly attractive method to investigate the stability, aging and microrheology properties of cellulose-based emulsions, providing valuable insights on their microstructure. This technique is thus highly appealing for the characterization and design of novel emulsion formulations. (C) 2018 The Authors. Published by Elsevier Inc. Portuguese Foundation for Science and Technology (FCT) [PTDC/AGR-TEC/4814/2014, 030619 (02/SAICT/2017), IF/01005/2014]; Sodra Skogsagarnas Stiftelse; Stiftelsen Nils och Dorthi Troedssons forskningsfond; Swedish Research Council VR [2015-04290] more...

Transition state models are proposed for chiral counterion induced stereoselectivity in cooperative dual catalysis access to the amination of alcohols., Asymmetric catalysis using two chiral catalysts in combination using one-pot reaction conditions is in its initial stages of development and understanding. We employ density functional theory (SMD(toluene)/M06/6-31G**,SDD(Ir)) computations to shed light on the action of chiral phosphoric acid and a chiral Cp*Ir(diamine) in stereoinduction in an asymmetric amination reaction of an alcohol. First, the protonation of the Ir–diamine complex by the phosphoric acid forms an ion-pair of the active catalytic dyad. Both chiral catalysts are involved throughout the catalytic cycle, thus constituting an important example of true cooperative catalysis. A borrowing hydrogen mechanism operates, wherein the phosphate abstracts the hydroxyl proton of the alcohol while the electrophilic Ir(iii) simultaneously extracts the α-hydrogen to form a [Ir]–H species. The ketone thus derived from the alcohol through dehydrogenation condenses with aniline to form an imine. In the diastereocontrolling transition state, the hydride adds to the activated iminium, held in position in the chiral pocket of the catalytic dyad through a network of noncovalent interactions (C–H···π, N–H···O and C–H···O). The enantioselectivity in this DYKAT process is identified as taking place at an earlier stage of the catalytic cycle prior to the diastereo-determining transition state. more...

International audience; Three new organic compounds primarily based on 8-hydroxyquinoline have been successfully synthesized and characterized via different spectroscopic methods (FTIR, H-1, and C-13 NMR). The synthesized compounds, namely 5-propoxymethyl-8-hydroxyquinoline (PMHQ), 5-methoxymethyl-8-hydroxyquinoline (MMHQ) and 5-hydroxymethyl-8-hydroxyquinoline (HMHQ), were evaluated as corrosion inhibitors for carbon steel in 1 M HCl solution using electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss measurements at 298 K. Electrochemical measurements confirmed that the newly synthesized 5-alkoxymethyl-8-hydroxyquinoline derivatives are mixed type corrosion inhibitors and confirmed maximum protection efficiencies of 94, 89 and 81% for PMHQ, MMHQ, and HMHQ, respectively, at the optimum concentration of 10(-3) M. The EIS spectra confirmed a slightly depressed semi-circle profile with a single time constant in Bode diagrams for the three organic compounds over the whole concentration and temperature ranges studied. The adsorption of PMHQ, MMHQ, and HMHQ on the carbon steel surface followed the Langmuir adsorption isotherm. In addition, the kinetic and thermodynamic parameters for carbon steel corrosion and inhibitor adsorption, respectively, were determined and discussed. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses supported the formation of a protective film on carbon steel in the presence of PMHQ, MMHQ, and HMHQ. Density functional theory calculations (DFT) showed that the effectiveness of the inhibitive actions of the studied compounds correlates well with their electron donating ability, whilst Monte Carlo simulations revealed that the extent and favourability of adsorption of inhibitor molecules on the carbon steel surface establish their corrosion inhibition performances. more...

PURPOSE: To determine the microtensile bond strength (µTBS) of two 2-step self-etch adhesives (SEAs) to bur-cut and uncut enamel. MATERIALS AND METHODS: The buccal and lingual enamel surfaces of 15 teeth were ground flat ("bur-cut" enamel), while the enamel surface of another set of 15 teeth was solely prophylactically cleaned ("uncut" enamel). Resin composite was bonded to the surfaces using the GPDM-based SEA OptiBond XTR (Kerr), the 10-MDP-based SEA Clearfil SE Bond (Kuraray Noritake), or the 3-step etch-and-rinse adhesive (E&RA) OptiBond FL (Kerr) that served as the gold-standard control. After 1-week water storage at 37°C, specimens were serially cut into 1-mm2 stick-shaped microspecimens, of which half per tooth were further subjected to 20,000 thermocycles (TC) prior to µTBS testing. Data were statistically analyzed using ANOVA and the post-hoc Tukey test. The interfacial ultrastructure of the GPDM-based SEA OptiBond XTR with uncut and bur-cut enamel was additionally characterized with transmission electron microscopy (TEM). RESULTS: After 1-week water storage and upon TC aging, both SEAs bonded significantly (p < 0.05) less effectively to both bur-cut and uncut enamel than did the control OptiBond FL, except when OptiBond XTR was bonded to bur-cut enamel; then a similarly high µTBS was recorded (p > 0.05). TEM interfacial characterization revealed a tight interaction of Optibond XTR with both bur-cut and uncut enamel. CONCLUSION: The best bonding efficacy to enamel is still achieved by etching with phosphoric acid, following an E&R approach, while the higher etching efficacy of the GPDM-based SEA may result in equally effective bonding, provided that the enamel is bur-roughened first. ispartof: JOURNAL OF ADHESIVE DENTISTRY vol:20 issue:2 pages:113-120 ispartof: location:Germany status: published more...

Suitability of TBP for recovery of uranium(VI) from dilute HNO3 using LEM extraction is investigated. TBP co-extracts significant amount of HNO3 along with U(VI). Beyond a critical time, extraction of U(VI) ceases due to attainment of critical acid level when the strip phase is unable to break TBP-U(VI) complex. The observed critical time is in good agreement with that estimated from rate of acid extraction. Optimal conditions at which the relative extraction of HNO3 is minimal with respect to U(VI) is arrived at. The extraction efficiency of TBP is compared with other ligands viz., TiAP, TEHP, TOPO, TOA and D2EHPA. more...

The response surface methodology is used to obtain optimal rate and extent of extraction of low concentration U(VI) (a parts per thousand currency sign100 mg/L) by liquid emulsion membrane technique. Three different ligands viz. Tri-n-octyl phosphine oxide (TOPO), Tri-n-octyl amine (TOA) and Di-(2-ethylhexyl)phosphoric acid (D2EHPA), are used. 2(3) factorial design is applied to generate second order regression equation for studying the effect of concentration of ligand, surfactant and feed acidity. The regression model is in good agreement with the experimental data for all ligands. The rate of extraction of U(VI) by LEM is found to be in the order TOA > TOPO > D2EHPA. more...

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) It has been hypothesized that cysteine cathepsins (CTs) along with matrix metalloproteases (MMPs) may work in conjunction in the proteolysis of mature dentin matrix. The aim of this study was to verify simultaneously the distribution and presence of cathepsins B (CT-B) and K (CT-K) in partially demineralized dentin; and further to evaluate the activity of CTs and MMPs in the same tissue. The distribution of CT-B and CT-K in sound human dentin was assessed by immunohistochemistry. A double-immunolabeling technique was used to identify, at once, the occurrence of those enzymes in dentin. Activities of CTs and MMPs in dentin extracts were evaluated spectrofluorometrically. In addition, in situ gelatinolytic activity of dentin was assayed by zymography. The results revealed the distribution of CT-B and CT-K along the dentin organic matrix and also indicated co-occurrence of MMPs and CTs in that tissue. The enzyme kinetics studies showed proteolytic activity in dentin extracts for both classes of proteases. Furthermore, it was observed that, at least for sound human dentin matrices, the activity of MMPs seems to be predominant over the CTs one. Univ Estadual Campinas, Fac Dent Piracicaba, BR-13414903 Piracicaba, Brazil Univ Sao Paulo, Bauru Sch Dent, Dept Biol Sci, BR-17012901 Bauru, SP, Brazil Univ Bologna, Dept Biomed & Neuromotor Sci, I-40126 Bologna, Italy Univ Trieste, Dept Med Sci, I-34128 Trieste, Italy Univ Iowa, Coll Dent, Dept Operat Dent, 801 Newton Rd, Iowa City, IA 52246 USA CNR, IGM, Unit Bologna, IOR, I-40136 Bologna, Italy Univ Fed Ceara, Dept Pharm Dent & Nursing, BR-60020181 Fortaleza, Ceara, Brazil Univ Carlo Bo, Dept SteVA, I-61029 Urbino, Italy Georgia Hlth Sci Univ, Dent Coll Georgia, Oral Biol, Augusta, GA 30912 USA Univ Oulu, Inst Dent, FI-90014 Oulu, Finland Oulu Univ Hosp, Med Res Ctr Oulu, FI-90014 Oulu, Finland Univ Oulu, FI-90014 Oulu, Finland Univ Helsinki, Dept Oral & Maxillofacial Dis, FI-00014 Helsinki, Finland Helsinki Univ Hosp, FI-00014 Helsinki, Finland Univ Fed Sao Paulo, Dept Biochem, BR-04021001 Sao Paulo, Brazil Univ Mogi das Cruzes, Ctr Interdisciplinar Invest Bioquim, BR-08773520 Mogi Das Cruzes, Brazil Anhanguera Univ Sao Paulo UNIAN SP, Biomat Dent Program, BR-05145200 Sao Paulo, Brazil Anhanguera Univ Sao Paulo UNIAN SP, Biotechnol & Innovat Hlth Program, BR-05145200 Sao Paulo, Brazil Univ Fed Sao Paulo, Dept Biochem, BR-04021001 Sao Paulo, Brazil FAPESP: 2007/54618-4 FAPESP: 2009/14005-9 CNPq: 312768/2013-3 Web of Science more...

Building up on an available synthetic methodology, phosphate monoesters ROPO3H2 have been synthesized in good yields. The synthetic procedure employed features acetic anhydride mediated activation of phosphoric acid in the presence of alcohols, leading to the formation of phosphate monoesters. The products have been isolated as their cyclohexyl amine salts, [CyNH3](2)[(MeO)PO3]center dot 3H(2)O (1) and [CyNH3][(RO)PO3H] (Cy = cyclohexyl; R = Et (2), iPr (3), or tBu (4)). Neutralization of 1-4 by readily available inexpensive ion exchange resin Amberlite produces monoalkylphosphates (RO)P(O).OH)(2) (R = Me (5), Et (6), iPr (7), or tBu (8)). Thermally labile 1-4 and 7 have been structurally characterized by single crystal X-ray diffraction studies. Due to their intrinsic thermal instability due to beta-H elimination, these compounds can be used as ligands for the preparation of single-source precursors for ceramic phosphates by reacting them with suitable metals ions. It is also possible to isolate co-crystals of the anionic and neutral forms of these phosphates as it has been demonstrated in the isolation and structural characterization of [(iPrO)PO3H2]center dot{[CyNH3][(iPrO)PO3H]} (9). To demonstrate the utility of these monoalkylphosphates in the low-temperature synthesis of metal phosphate bioceramics, isopropyl phosphate 7 has been employed to prepare calcium phosphate [{Ca((iPrO)PO3)(OH2)}center dot H2O] n (10), which undergoes neat thermal decomposition in two stages to lose water and propene to yield beta-Ca2P2O7 at low temperatures (280 degrees C). more...

Enamides with a free NH group have been evaluated as nucleophiles in chiral Bronsted acid-catalyzed enantioselective alpha-amidoalkylation reactions of bicyclic hydroxylactams for the generation of quaternary stereocenters. A quantitative structure-reactivity relationship (QSRR) method has been developed to find a useful tool to rationalize the enantioselectivity in this and related processes and to orient the catalyst choice. This correlative perturbation theory (PT)-QSRR approach has been used to predict the effect of the structure of the substrate, nucleophile, and catalyst, as well as the experimental conditions, on the enantioselectivity. In this way, trends to improve the experimental results could be found without engaging in a long-term empirical investigation. Ministerio de Economia y Competitividad (CTQ2013-41229-P), IKERBASQUE foundation, Gobierno Vasco (IT-623-13) and Universidad del Pais Vasco/Euskal Herriko Unibertsitatea UPV/EHU are gratefully acknowledged for their financial support. Technical and human support provided by Servicios Generales de Investigacion SGIker (UPV/EHU, MINECO, GV/EJ, ERDF and ESF) is also acknowledged. more...

Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near-constant temperature, salinity, and pH and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop “clumped” isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate-related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly substituted isotopologue 13C18O16O2 in carbonate minerals, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 in live-collected aragonitic scleractinian (Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ47 values were compared to in situ temperatures, and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ47–temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ47–temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset between the corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect high-Mg and aragonite crystals attaining nominal mineral equilibrium clumped isotope signatures due to conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological “vital effect” influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological vital effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ47 is a subject that warrants further investigation. more...

International audience; Activated carbons are widely used as supports for industrial catalysts based on metal nanoparticles. The catalytic performance of carbon-supported catalysts is strongly influenced by the carbon activation method. Notwithstanding this important role, the effect induced by different activation methods has been rarely investigated in detail. This work deals with two carbons of wood origin, activated either by steam or by phosphoric acid, and the corresponding catalysts based on supported Pd nanoparticles. We demonstrate that the catalysts perform in a different way in hydrogenation reactions depending on the nature of the carbon used as a support, being the palladium dispersion the same. We propose a multi-technique approach to fully characterize both carbons and catalysts at the micro-and nanoscale. In particular, we investigate how the activation procedure influences the texture (by N-2 physisorption), the morphology (by Scanning Electron Microscopy), the structure (by Solid State Nuclear Magnetic Resonance, Raman spectroscopy and X-ray Diffraction) and the surface properties (by X-ray Photoelectron Spectroscopy, Diffuse Reflectance Infrared Spectroscopy and Inelastic Neutron Scattering) of carbons and of the related catalysts. The comprehensive characterization approach proposed in this work allows the rationalization, at least in part, of the role of activated carbons in enhancing the performance of a hydrogenation catalyst more...

New composite free standing films were fabricated by solution casting poly(diethyl, dipropyl)phosphazene, phosphoric acid and a naphthalenic sulfonated copolyimide. The proton conductivity data in dry environment obtained for these films allow to conclude that the presence of strong sulfonic acid proton donors and of phosphazene N proton acceptor sites is not sufficient to allow good conductivity in dry environment, and that the content of phosphoric acid appears the most critical factor for the proton mobility. more...

International audience; Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermo-physiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endo-therms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but B6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to modern birds, but was able to elevate its body temperature above environmental temperatures. Therefore, we observe no strong evidence for end-member ectothermy or endothermy in the species examined. Body temperatures for these two species indicate that variable thermoregulation likely existed among the non-avian dinosaurs and that not all dinosaurs had body temperatures in the range of that seen in modern birds. more...

Objectives. This study evaluated the endogenous matrix metalloproteinase (MMP) activity of demineralized dentin matrix following 1 or 5 min pretreatment by various collagen crosslinkers. Generic MMP activity assay, total protein analysis, in situ zymography, gelatin zymography and multiplex bead technology were used to evaluate matrix-bound MMP activity. Methods. Six different crosslinkers; glutaraldehyde, riboflavin/UVA, riboflavin-5-monophospate/UVA, sumac berry extract, grape seed extract, and curcumin were used. Demineralized dentin beams were pretreated with respective crosslinkers for 1 or 5 min. Demineralized dentin beams with no crosslinker pretreatment served as control. The reduction in the total activity of dentin matrices were measured using generic MMP activity assay. Dentin slabs were used for in situ zymography and evaluated by using hydrolysis of self-quenched fluorescein-conjugated gelatin under confocal microscopy. Dentin beam extracts were used for total protein assay and multiplex analysis and powder extracts were used for gelatin zymography. Results. MMP activity in crosslinker pretreated samples decreased significantly between 21% and 70%, whereas untreated control samples' activity increased up to 84%. Zymograms confirmed a decrease in the gelatinolytic activity and in the amount of extractable total protein content. Multiplex analysis of extracts of crosslinker-treated dentin showed a reduction in the MMP-8, MMP-2 and MMP-9 release. Significance. The result of this work suggests that the effect of the crosslinkers is source dependent. The use of crosslinkers for as little as 1 min on demineralized dentin can inactivate the endogenous protease activity of dentin matrices. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. more...

2-(tert-butyldimethylsilyl)-5-(10-bromodecyl)-1-(N,N-dimethylsulfamoyl)-imidazole and NaPO3 Et2 react at room temperature to yield the corresponding imidazole diethyl phosphonate, which when reflux... more...

Polybenzimidazole (PBI) has become a popular polymer of choice for the preparation of membranes for potential use in high-temperature proton exchange membrane polymer fuel cells. Phosphoric acid-doped composite membranes of poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI4N) impregnated with hafnium oxide nanofiller with varying content levels (0-18 wt %) have been prepared. The structureproperty relationships of both the undoped and acid-doped composite membranes are studied using thermogravimetric analysis, modulated differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray scattering, infrared spectroscopy, and broadband electrical spectroscopy. Results indicate that the presence of nanofiller improves the thermal and mechanical properties of the undoped membranes and facilitates a greater level of acid uptake. The degree of acid dissociation within the acid-doped membranes is found to increase with increasing nanofiller content. This results in a conductivity, at 215 degrees C and a nanofiller level x = 0.04, of 9.0 x 10(-2) S cm(-1) for [PBI4N(HfO2)(x)](H3PO4)(y). This renders nanocomposite membranes of this type as good candidates for use in high temperature proton exchange membrane fuel cells (HT-PEMFCs). more...

INTRODUCTION: The aims of this study were to systematically review the available literature regarding in-vitro orthodontic shear bond strength testing and to analyze the influence of test conditions on bond strength.METHODS: Our data sources were Embase and Medline. Relevant studies were selected based on predefined criteria. Study test conditions that might influence in-vitro bond strength were independently assessed by 2 observers. Studies reporting a minimum number of test conditions were included for meta-analysis by using a multilevel model with 3 levels, with author as the highest level, study as the second level, and specimens in the study as the lowest level. The primary outcome measure was bond strength.RESULTS: We identified 121 relevant studies, of which 24 were included in the meta-analysis. Methodologic drawbacks of the excluded studies were generally related to inadequate reporting of test conditions and specimen storage. The meta-analysis demonstrated that 3 experimental conditions significantly affect in-vitro bond strength testing. Although water storage decreased bond strength on average by 10.7 MPa, each second of photopolymerization time and each millimeter per minute of greater crosshead speed increased bond strength by 0.077 and 1.3 MPa, respectively.CONCLUSIONS: Many studies on in-vitro orthodontic bond strength fail to report test conditions that could significantly affect their outcomes. more...

International audience; Activated carbons were prepared from biomass of Algerian date pits for developing efficient and cheap adsorbents in the aim to remove heavy metals from waste water. Carbon adsorbents were obtained following two successive treatments: pyrolysis under dry nitrogen flow and physical activation under wet nitrogen flow. Pyrolysis process was optimized by varying some operating parameters such as temperature, nitrogen flow, heating rate and pyrolysis hold time in order to determine their effects on the porous structure development of date pits activated carbon. Chars obtained from pyrolysis process were activated with the same operating conditions (activation temperature of 700 degrees C, 50% nitrogen + 50% water flow rate of 150 cm(3)/min and heating rate of 10 degrees C/min) except for the activation hold time which varied from 0.5 to 4h. Experimental results showed that pyrolysis conditions have significant effects on the chars and activated carbons properties prepared from date pits. The best rnicroporous activated carbon (surface area of 464 m(2)/g, microporous volume of 0.203 cm(3)/g and total pore volume of 0.220 cm(3)/g) was obtained by pyrolysis at 10 degrees C/min up to 700 degrees C for 1 h under 150 cm(3)/min of nitrogen. Activation hold time has also an impact on activated carbons porosity. The best surface area. microporous volume and total pore volume were obtained after activation for 4 h: 1467 m(2)/g. 0.711 cm(3)/g and 0.725 cm(3)/g respectively. The best adsorbents prepared from date pits were then tested for the removal of Fe3+ and Cu2+ from aqueous solutions. Results show that these adsorbents have higher metallic cation adsorption capacities than usual commercial activated carbons because of the presence of both carboxylic and phenolic groups at the surface witch improves the cation-exchange and complexation properties of these adsorbents in addition of the greater specific surface area. Adsorption data were analyzed with Langmuir and Freundlich isotherms. The better fit is obtained with the Langmuir model. more...

A novel one-pot, three-component synthesis of N-acyl or N-carbamoyl-alpha-amidosulfides 4 is described. The three-component reaction of aldehydes 1, primary carbamates (or amides) 2 and phenylsulfinic acid (6a) afforded alpha-amidosulfones 7, which after addition of sodium thiolate were in situ transformed into stable alpha-amidosulfides 4 in good to excellent yields. We demonstrated that silver salts or Bronsted acids were able to promote the formation of aliphatic and aromatic N-acylimines from 4 in quantitative yield under mild conditions. The phosphoric acid catalyzed Friedel-Crafts alkylation of 3-substituted indoles with alpha-amidosulfides 4 leading to 2,3-disubstitued indoles was also documented. more...

Carbon blacks such as Vulcan XC-72 are widely used to support platinum (Pt) or Pt alloy catalysts in proton exchange membrane fuel cells. Despite their widespread use, carbon blacks are susceptible to corrosion during fuel cell operations. In this work, the corrosion behaviors of platinized Vulcan XC-72 nanoparticles under thermal and electrochemical conditions were monitored by transmission electron microscopy (TEM). The thermal corrosion experiment was carried out in a gas-cell TEM, which allows for a direct observation of the thermal oxidation behavior of the nanoparticles. The electrochemical corrosion experiment was performed outside of the TEM by loading the nanoparticles on a TEM grid and then electrochemically corroding them step by step followed by taking TEM images from exactly the same nanoparticles after each step. This work revealed four types of structural changes: (i) total removal of structurally weak aggregates, (ii) breakdown of aggregates via neck-breaking, (iii) center-hollowed primary particles caused by an inside-out corrosion starting from the center to outer region, and (iv) gradual decrease in the size of primary particles caused by a uniform removal of material from the surface. These structural changes took place in sequence or simultaneously depending on the competition of carbon corrosion dynamical processes. The results obtained from this work provide insight on carbon corrosion and its effects on fuel cells' long-term performance and durability. more...

Introduction The aims of this study were to systematically review the available literature regarding in-vitro orthodontic shear bond strength testing and to analyze the influence of test conditions on bond strength. Methods Our data sources were Embase and Medline. Relevant studies were selected based on predefined criteria. Study test conditions that might influence in-vitro bond strength were independently assessed by 2 observers. Studies reporting a minimum number of test conditions were included for meta-analysis by using a multilevel model with 3 levels, with author as the highest level, study as the second level, and specimens in the study as the lowest level. The primary outcome measure was bond strength. Results We identified 121 relevant studies, of which 24 were included in the meta-analysis. Methodologic drawbacks of the excluded studies were generally related to inadequate reporting of test conditions and specimen storage. The meta-analysis demonstrated that 3 experimental conditions significantly affect in-vitro bond strength testing. Although water storage decreased bond strength on average by 10.7 MPa, each second of photopolymerization time and each millimeter per minute of greater crosshead speed increased bond strength by 0.077 and 1.3 MPa, respectively. Conclusions Many studies on in-vitro orthodontic bond strength fail to report test conditions that could significantly affect their outcomes. more...

ispartof: Operative Dentistry pages:119-144 ispartof: location:Charleston status: published

Low frequency dielectric measurements in triglycine sulpho-phosphate (TGSP) and gamma-irradiated TGSP crystals were carried out around the ferroelectric to paraelectric phase transition. The dispersion found in the ferroelectric phase cannot be explained only by a Debye equation with a single relaxation time. The ratio of the Curie constants in the para- and ferroelectric phase (C-p/C-f) for the irradiated TGSP samples show that the crystal is partially clamped. The deviations from the typical single relaxation behaviour are more pronounced in irradiated samples clearly indicating the contribution of defects in addition to the impurities to the dynamics of the system more...