catena-Poly[(μ3-2-hy­droxy-4-isopropyl­cyclo­hepta-2,4,6-trien-1-onato)(μ2-2-hy­droxy-4-isopropyl­cyclo­hepta-2,4,6-trien-1-onato)lead(II)]

In the title compound, [Pb(C10H11O2)2]n or [Pb(hino)2]n, the lead(II) ion is chelated by two hinokitiolate ligands in a distorted square-pyramidal configuration, with Pb—O bond lengths in the range 2.327 (6)–2.479 (9) Å. The 6s 2 lone electron pair of the lead(II) ion becomes stereochemically active and is directed towards the apex of this pyramid. The crystal structure of the title compound consists of chains formed by the bis­(hinokitiolato)lead(II) mol­ecules situated along the twofold screw axis. The coordination sphere around the lead(II) ion is completed by three additional O atoms, at 2.625 (7), 3.016 (8) and 3.064 (8) Å, from the two neighbouring Pb(hino)2 units. Both isopropyl groups are rotationally disordered

The design of pipe thread rolling rollers

Prezentirana je analiza distribucije tolerancije kod valjanja cijevnog navoja s valjcima identičnog polumjera zaobljenja vrha navoja. Razrađeni su teorijski odnosi i metodologija za računanje promjera utiskivanja navoja s pretpostavljenom distribucijom tolerancije utiskivanja koje je mjereno pomoću istisnutog volumena materijala. Dani su ilustrirani primjeri razrađenih odnosa.The analysis of the allowance distribution in pipe thread rolling with rollers of the identical thread crest rounding radius has been presented. Theoretical relationships and methodology for computing the embossing thread diameter with the assumed distribution of the embossing allowance as measured by the displaced material volume have been elaborated. Examples illustrated elaborated relationships have been given

Soft Mass Spectrometry in Drinking Water Analysis Using Differential Ion Mobility Spectroscopy

The analysis of labile ions that easily decompose at various stages of the analytical process is a significant challenge for any analytical method. In this thesis, a new analytical approach based on “soft” mass spectrometry and differential ion mobility was developed that enables the detection of such labile analytes in a quick and convenient fashion, without the need for extensive sample preparation and column separation. Soft mass spectrometry approach combines techniques of electrospray ionization (ESI), differential ion mobility spectroscopy (FAIMS) and mass/tandem mass spectrometry (QTOF-MS/MS). The key feature of ESI-FAIMS-QTOF-MS is the replacement of liquid chromatography by a FAIMS separation technique which eliminates chemical background during the analysis. It also improves the quality of spectral data and provides the detection of thousands of analytes down to a part-per-trillion concentration level. Most importantly, the technique offers extremely soft conditions for ion introduction and their transport through the mass spectrometer. The greatest advantage, in using the soft mass spectrometry approach is that fragile species which were beyond the scope of conventional mass spectrometry approaches can now be analyzed. This thesis demonstrates unique capabilities of the soft ESI-FAIMS-QTOF-MS technique in non-target analysis, which led to the discovery of sulphur-containing polar congeners of thiotetronic acids (TA) in drinking water from underground sources in Canada, United States and Europe. Polar TAs accumulate in underground aquifers and appear to be the most abundant class of organic compounds in groundwater but cannot be detected by conventional mass spectrometry methods due to their extremely fragile nature. Structural elucidation of TAs detected in this study was accomplished using de novo identification approach in which the elemental composition from accurate mass measurements and the manual interpretation of MS/MS data were utilized. TA derivatives were originally isolated from soil bacteria and are investigated in the pharmaceutical industry for their potent activity against a broad spectrum of pathogenic bacteria and negligible toxicity to mammals. We suspect, TA congeners characterized in this study are natural disinfection agents protecting groundwater from bacterial contamination and have minimal biological impact on humans

Alum sludge as an efficient sorbent for hydrogen sulfide removal: Experimental, mechanisms and modeling studies

International audienceThis paper firstly reported a systematic study of using alum sludge (waterworks residue) for H2S adsorption. Various trials were performed at ambient temperature in a fixed bed column to study the effects of H2S flow rate, sorbent bed depth on the alum sludge adsorption efficiency of H2S. The Breakthrough Curves were simulated by the Thomas model, Bed Depth Service Time model and Yoon-Nelson models. The mechanisms of H2S adsorption onto alum sludge was examined by different physiochemical characterizations of exhausted and raw alum sludge. Moreover, the mass transfer coefficients were determined from mathematical descriptions of breakthrough curves. The alum sludge adsorption capacity was determined to be 374.2 mg of H2S/g, slightly decreasing with the increasing flow rate and increasing with the increasing bed depth. All the three models successfully predict breakthrough curves which could be used for scaling-up purposes. The microporous structure, alkaline pH and the inherent metal species of the alum sludge promoted the formation of metal sulphate species. This study demonstrated that alum sludge could be used as cost-effective, largely available, and efficient sorbent for H2S removal

Characterization of LiFePO4/C Cathode for Lithium Ion Batteries

International audienceLiFePO4/C was synthesized from a mixture of different precursors of Li, Fe, and C by solid-state reaction. The initial mixture obtained was heated in different calcination conditions under inert atmosphere. The precursor of LiFePO4 doped with carbon was studied using different techniques such as thermal analysis, chemical and physical characterizations, and Mosbauer spectroscopy. A calculation of the crystallinity of the final product with two different methods is also presented. The chemical analysis techniques used were IRTF, XRD, and SEM. This characterization confirmed that we obtained a well-crystallized LiFePO4/C in all the operating conditions tested. The SEM showed aggregation and sintering during the calcination process, which were confirmed by the particle-size distribution measurements and by the physical characterizations. Mosbauer spectroscopy was used to determine the quantity of Fe(II) and Fe(III) contained in the final product. Our calcination conditions did not significantly modify the quantity of the two oxidation states

110th Anniversary: Syngas production enhancement using calcium and potassium impregnated chars

International audienceSyngas production enhancement via catalytic methane cracking onto metal-loaded chars, with a specific focus on the activity of two inherent alkali and alkaline earth metals (AAEMs), Ca and K, was investigated. Chars produced from the gasification of poplar wood pellets were heated to 700°C in inert atmosphere and then tested as catalysts for methane cracking at 700°C. Methane is one of the most abundant biomass gasification by-product. The cracking of this component is relevant in increasing the syngas production and yield. The syngas production was increased by a factor 1.9 to 2.7 using metal-loaded chars. Results were explained by the catalytic effect of AAEMs on both the desorption of oxygenated functional groups and on the catalytic methane cracking. AAEMs promoted methane molecules combination with the active sites such as oxygenated groups available at the surface of the chars enhancing both H2 and CO production. It was observed that potassium loaded char (K-char) showed the best performance. The calcium-loaded char (Ca-char) was less efficient, due to a higher amount of silicon which interacted with calcium to form silicates. No synergetic effect was observed on the syngas production with the Ca+K_char

Anaerobic co-digestion of food waste and FOG with sewage sludge – realising its potential in Ireland

International audienceThe severe environmental pollution in many countries is caused by indiscriminate discharge of large quantities of food waste (FW), fat oil and grease (FOG) and sewage sludge (SS) to the environment. There are many possible treatment routes, but anaerobic digestion (AD) is now well accepted for treating several kinds of organic wastes. But AD of FW alone presents some operational challenges because of substrates and variability. Anaerobic co-digestion of two or more substrates is better than single substrate digestion. This can use a plant’s unused capacity, in line with the trend to renewable energy. Co-digestion technology, although well established in many European countries, is still in its infancy in Ireland. There are problems with different regulatory arrangements. They should be resolved. The paper reviews anaerobic co-digestion technology is reviewed, with special focus on possible application in Ireland

Poly[bis­(μ3-acetato-κ4 O,O′:O:O′)bis­(μ2-acetato-κ3 O,O′:O)(μ2-2,5-dimethyl­benzene-1,4-diol-κ2 O:O′)dilead(II)]

The title compound, [Pb2(C2H3O2)4(C8H10O2)]n, has a polymeric structure, with acetatolead(II) chains and 2,5-dimethyl­benzene-1,4-diol mol­ecules forming bridges between two PbII ions from neighbouring chains. Each PbII centre is surrounded by eight O atoms; four belong to bidentate acetate ions, three to neighbouring bridging acetate groups and one to the 2,5-dimethyl­benzene-1,4-diol mol­ecule. The PbII ions are chelated symmetrically and asymmetrically by acetate ligands. The coordination environment of the PbII ion can be described as a hemidirected PbIIO6 core with the empty space around the metal ion filled by the stereochemically active 6s 2 electron pair and two longer Pb—O contacts. The Pb—O distances are in the range of 2.355 (3)–2.994 (3) Å. Additionally, the crystal structure is stabilized by O—H⋯O hydrogen bonds

Stress relaxation behavior of organically modified montmorillonite filled natural rubber/nitrile rubber nanocomposites

International audienceTo reduce material consumption, it is important to have reinforced material with longer life time. Incorporation of nanoparticles to reinforce and compatibilize polymer blends is one of the widely undergoing research areas in polymer science technology. A series of natural rubber and nitrile rubber (NR/NBR) nanocomposite vulcanazite, reinforced with two different organically modified clay (OMt) were prepared. To predict the performance of a material over long periods of time, stress relaxation studies with both the reinforced systems were done. The effects of loading, blend composition, filler polarity and temperature on stress relaxation of OMt reinforced NR/NBR nanocomposites were carefully measured. Based on the stress relaxation measurements, it was observed that due to its polarity difference, O1Mt (Mt modified with dimethyl, benzyl, HT modification provided by Southern Clay Products) was preferentially located at the NBR phase while O2Mt (Mt modified with mercapto silane provided by English India Clay) had more affinity with natural rubber in the NR/NBR nanocomposites. The preferential localization of OMt has been analyzed by HRTEM. The nature of interaction of the nanoclay was found to influence the stress relaxation rate. NR/NBR nanocomposites with higher filler loading showed higher rates of relaxation rate due to the presence of more filler-filler interactions. At 70 degrees C, the viscosity ratio was found to influence the reinforcement, and consequently relaxation rate of the 50/50 NR/NBR nanocomposites. It was found that the rearrangements of the polymer chains are dependent on the blend composition, temperature, filler/polymer interactions etc. To explain and predict observed phenomena, the stretched-exponential Kohlrausch equation and Maxwell-Weichert model were used. For both models, the experimental curve fitted well with the theoretical models. (C) 2013 Elsevier B.V. All tights reserved

High bubble concentrations produced by ultrasounds in binary mixtures

7th Meeting of the European‐Society‐of‐Sonochemistry, BIARRITZ GUETHARY, FRANCE, MAY 14‐18, 2000International audienceIt was discovered that simultaneous insonification and air blowing of different aqueous binary solutions such as water/sodium‐dodecyl‐sulphate (SDS), water/methanol or water/potassium‐sulphate yields a very concentrated bubble cloud invading the whole vessel in a few seconds. After the end of insonification, this cloudiness remained in the solution for about 1 min. The phenomenon was investigated by computer‐treatment of solution pictures recorded every second after the end of insonification. Turbidity appeared to increase with ultrasound power, and also with SDS concentration. During the disappearance of the cloud, a turbidity front appeared rising and spreading upward. This front was studied in the characteristic plane and interpreted as a spatial segregation of different bubble sizes rising with different terminal velocities. The bubble sizes involved were estimated to about 10 mum. Adsorption of surface active species are invoked to explain the cloud formation and its abnormally slow disappearance, but the occurrence of the phenomenon for potassium‐sulphate salt remains unexplained