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A kinetic model was developed for the prediction of HTL product yields based on a chemical mechanism. The model was developed after experimental studies on food wastes and food processing wastes. The model parameters were determined by training the model on experimental data on HTL of food wastes. Two other models from the literature were also tested. The calculated yields were compared with a large range of experimental data from the literature. Yields of bio-oil and char can be predicted from the process conditions, temperature, holding time, dry matter content, and the biochemical composition of the resource. Differences in the experimental recovery procedure and polarity of the extraction solvent are taken into account. This study shows that a kinetic model based on compositions allows a more detailed representation of the hydrothermal reactions than models purely based on resources and products. The precision of any model remains, however, largely dependent on the quality of the input data.

The hydroxyl radical is the most powerful oxidant after fluorine, and is the key reactant of theadvanced oxidation processes AOP. Monitoring the kinetics of formation and reaction of this short life speciesis one of the challenging tasks from an experimental point of view. Thus, modelling is suggested to be oneefficient tool for a comprehensive and predictive study of AOPs, particularly the Galvano-Fenton process. In thepresent study, mathematical modelling is used to describe the kinetics of hydroxyl radical 𝐻𝑂• generation andorganic substrate 𝑅𝑂 degradation within the Galvano-Fenton process, based on the spontaneous galvaniccorrosion of iron waste and in situ ferrous ion catalyst generation. A range of typical absolute kinetic constantsof 106 à 1010 M-1.s-1 is considered to characterize the attack of 𝑅𝑂 species by 𝐻𝑂•. Phenol is presented as amodel pollutant for a total mineralization model. The numerical simulations demonstration a quasi-linearevolution of hydroxyl radical production during the first stage of the Galvano-Fenton process. A comparison ofthe Galvano-Fenton process with the classic Fenton in terms of kinetics, and electro-Fenton in terms ofenergetic performance, revealed that the spontaneous galvanic generation of ferrous ions in the Galvano-Fentonprocess leads to a higher rate of the reaction a higher instantaneous concentration of ferric ions accompanyingthe release of hydroxyl radicals and hence a better oxidation efficiency, as well as a positive energy balance. Aparticular attention was given to the ratio of the degradation efficiency to the released energy.

One of the oldest and most well-known cosmetics, hair color has been used by numerous ancient cultures throughout history on both men and women. It involves treating hair with various chemical compounds for changing hair color. According to how long they remain in the hair, these products are primarily divided into two categories: temporary and permanent. This classification is consistent with the types of active substances used in the dyeing process as well as the dyeing method itself, which are referred to as non-oxidative and oxidative hair dye products, respectively. Permanent hair dyes often consist of active chemicals that are not dyed but are oxidized to provide the desired color. As a result, the phrase "oxidative hair dye" was emerged. The precursor part and coupler part are the two main ingredients in formulations for oxidative hair dyes. Quinonediimine intermediates are momentary compounds that are generated when combined with hydrogen peroxide (developer). As a result, the coupler agent and these compounds interact to form the appropriate hair dye molecule. Notably, the entire dyeing process requires both an alkaline medium and an oxidizing agent, often hydrogen peroxide, to ensure that the staining agents reach the cuticle widely. This review's objective is to provide information about hair dye formulations and mechanisms of action as well as repairing damaged hair and new applications.

We have structure, a wealth of kinetic data, thousands of chemical ligands and clinical information for the effects of a range of drugs on monoamine oxidase activity in vivo. We have comparative information from various species and mutations on kinetics and effects of inhibition. Nevertheless, there are what seem like simple questions still to be answered. This article presents a brief summary of existing experimental evidence the background and poses questions that remain intriguing for chemists and biochemists researching the chemical enzymology of and drug design for monoamine oxidases (FAD-containing EC 4.1.3.4).

12 pags, 4 figs, 3 tabs. -- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.1c03160., We present a new chemical mechanism for Hg0/HgI/HgII atmospheric cycling, including recent laboratory and computational data, and implement it in the GEOS-Chem global atmospheric chemistry model for comparison to observations. Our mechanism includes the oxidation of Hg0 by Br and OH, subsequent oxidation of HgI by ozone and radicals, respeciation of HgII in aerosols and cloud droplets, and speciated HgII photolysis in the gas and aqueous phases. The tropospheric Hg lifetime against deposition in the model is 5.5 months, consistent with observational constraints. The model reproduces the observed global surface Hg0 concentrations and HgII wet deposition fluxes. Br and OH make comparable contributions to global net oxidation of Hg0 to HgII. Ozone is the principal HgI oxidant, enabling the efficient oxidation of Hg0 to HgII by OH. BrHgIIOH and HgII(OH)2, the initial HgII products of Hg0 oxidation, respeciate in aerosols and clouds to organic and inorganic complexes, and volatilize to photostable forms. Reduction of HgII to Hg0 takes place largely through photolysis of aqueous HgII-organic complexes. 71% of model HgII deposition is to the oceans. Major uncertainties for atmospheric Hg chemistry modeling include Br concentrations, stability and reactions of HgI, and speciation and photoreduction of HgII in aerosols and clouds., This work was funded by the USEPA Science to Achieve Results (STAR) Program. This work was also supported by the Slovak Grant Agency VEGA (grant 1/0777/19), the highperformance computing facility of the Centre for Information Technology (https://uniba.sk/en/HPC-Clara) at Comenius University, and the U.S. National Science Foundation under awards 1609848 and 2004100. We thank Helene Angot (CU Boulder) for the Hg measurement data.

Surface enhanced Raman scattering (SERS) is a fingerprint spectral technique whose performance is highly dependent on the physicochemical properties of the substrate materials. In addition to the traditional plasmonic metal substrates that feature prominent electromagnetic enhancements, boosted SERS activities have been reported recently for various categories of non-metal materials, including graphene, MXenes, transition-metal chalcogens/oxides, and conjugated organic molecules. Although the structural compositions of these semiconducting substrates vary, chemical enhancements induced by interfacial charge transfer are often the major contributors to the overall SERS behavior, which is distinct from that of the traditional SERS based on plasmonic metals. Regarding charge-transfer-induced SERS enhancements, this short review introduces the basic concepts underlying the SERS enhancements, the most recent semiconducting substrates that use novel manipulation strategies, and the extended applications of these versatile substrates., Public Summary • Surface-enhanced Raman scattering (SERS) is a fingerprint spectral technique highly dependent on the substrate materials. • Charge transfer transitions are commonly the major contributors to the boosted SERS activities in non-metal substrates. • Novel manipulation strategies and extended applications of the versatile substrates are illustrated on the basis of interfacial charge transfer., Graphical Abstract

International audience; 3-Methyl-4-aza[6]helicene (A6H) enantiomers were synthesized and proposed as high-performance visible light photoinitiators and/or photosensitizers for the free radical polymerization (FRP) of (meth)acrylates upon visible light exposure using inexpensive and safe light-emitting diodes (LEDs) at 405 nm. Excellent polymerization initiating abilities were found, and high final conversions were obtained. Remarkably, an exceptional strongly enhanced chiral property of the polymer films was observed in the presence of the enantiopure azahelicenes. This is the first example of chiral properties introduced in polymer films by the photoinitiator through photopolymerization processes. It is of high interest as these latter are very fast and inexpensive polymerization techniques. Remarkably, contrary to chiral properties introduced by using a combination of commercial photoinitiator and chiral dopant, a dual behavior is found here for A6H. A full picture of the involved chemical mechanisms is given. © 2018 American Chemical Society.

To better understand precursors of dicarboxylic acids in ambient secondary organic aerosol (SOA), we studied C4–C9 dicarboxylic acids present in SOA formed from the oxidation of toluene, naphthalene, α-pinene, and isoprene. C4–C9 dicarboxylic acids present in SOA were analyzed by offline derivatization gas chromatography–mass spectrometry. We revealed that C4 dicarboxylic acids including succinic acid, maleic acid, fumaric acid, malic acid, DL-tartaric acid, and meso-tartaric acid are produced by the photooxidation of toluene. Since meso-tartaric acid barely occurs in nature, it is a potential aerosol tracer of photochemical reaction products. In SOA particles from toluene, we also detected a compound and its isomer with similar mass spectra to methyltartaric acid standard; the compound and the isomer are tentatively identified as 2,3-dihydroxypentanedioic acid isomers. The ratio of detected C4–C5 dicarboxylic acids to total toluene SOA mass had no significant dependence on the initial VOC/NOx condition. Trace levels of maleic acid and fumaric acid were detected during the photooxidation of naphthalene. Malic acid was produced from the oxidation of α-pinene and isoprene. A trace amount of succinic acid was detected in the SOA produced from the oxidation of isoprene.

The present study provides a fundamental understanding of the mechanism of action of special new phosphate glass (P-glass) systems, having different glass transition temperatures (Tg), in polyamide 66 (PA66). Dynamic mechanical analysis (DMA) revealed that the Tg of PA66/low Tg P-glass (ILT-1) was significantly shifted to a lower Tg (65 &deg, C), and another transition appeared at high temperature (166 &deg, C). This was supported by a drop in the melting point and the crystallinity of the PA66/ILT-1 hybrid material as detected by differential scanning calorimetry (DSC). The dielectric spectroscopic investigation on the networks&rsquo, molecular level structural variations (Tg and sub-Tg relaxations) agreed very well with the DMA and DSC findings. Contrary to intermediate Tg(IIT-3) and high Tg P-glass (IHT-1) based materials, the PA66/ILT-1 hybrid material showed an evidence of splitting the PA66 Tg relaxations into two peaks, thus confirming a strong interaction between PA66 and ILT-1 (low Tg P-glass). Nevertheless, the three different P-glass compositions did not show any effect on the PA66 sub-Tg relaxations (related to the &ndash, NH2 and &ndash, OH chain end groups&rsquo, motion).

The electromagnetic/plasmonic (SERS-PL) and the chemical (usually involving resonant photoinduced metal-adsorbate (M-A) charge transfer processes (SERS-CT:M-A+hn-->M+-A-)) mechanisms are recognized as the two main contributions to the enhancement of a particular band in a SERS record. The key problem is to know which mechanism dominates the spectrum and to apply the corresponding selection rules. Many spectra have been analyzed according to the so-called “SERS propensity rules” of the PL mechanism. In this way, it would be possible to get information about the perpendicular/parallel orientation of the adsorbate on the nanoparticle if in-plane/out-of-plane vibrations of planar aromatic molecules show relative enhancement. The SERS of pyridazine (Pdz) on a silver electrode (Figure 1) is a very special case where the relative intensities are tuned by the electrode potential. Three different types of spectra are recorded showing no selective intensification (0 V) or in-plane (-0.5 V) and out-of-plane (-0.75 V) enhancements. The relative activity of both in-plane (8a and 19b modes) and out-of-plane (16b mode) vibrations can be explained under the same resonant SERS-CT chemical mechanism due to Franck-Condon factors related to differences between the equilibrium geometries (A1 vibrations, DQ≠0) and gradients (B1 vibrations, Dn≠0 and DQ≠0), respectively, of the potential energy surfaces of the involved ground and photoinduced CT electronic states. Therefore, it is not necessary to resort to any change in the orientation of the adsorbate, which is the standard explanation based on the propensity rules of the SERS-PL mechanism. This conclusion is supported on the basis of electronic structure calculations of the properties of Ag2-Pdz clusters in the ground (S0;A1) and excited states with CT characteristics (CT0;A2 and CT1;B1). Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Arylalkylamine N-acyltransferases (AANATs) catalyze the formation of an N-acylamide from an acyl-CoA thioester and an amine. One well known example is the production of N-acetylserotonin from acetyl-CoA and serotonin, a reaction in the melatonin biosynthetic pathway from tryptophan. AANATs have been identified from a variety of vertebrates and invertebrates. Considerable efforts have been devoted to the mammalian AANAT because a cell-permeable inhibitor specifically targeted against this enzyme could prove useful to treat diseases related to dysfunction in melatonin production. Insects are an interesting model for the study of AANATs because more than one isoform is typically expressed by a specific insect and the different insect AANATs (iAANATs) serve different roles in the insect cell. In contrast, mammals express only one AANAT. The major role of iAANATs seem to be in the production of N-acetyldopamine, a reaction important in the tanning and sclerotization of the cuticle. Metabolites identified in insects including N-acetylserotonin and long-chain N-fatty acyl derivatives of dopamine, histidine, phenylalanine, serotonin, tyrosine, and tryptophan are likely produced by an iAANAT. In vitro studies of specific iAANATs are consistent with this hypothesis. In this review, we highlight the current metabolomic knowledge of the N-acylated aromatic amino acids and N-acylated derivatives of the aromatic amino acids, the current mechanistic understanding of the iAANATs, and explore the possibility that iAANATs serve as insect “rhymezymes” regulating photoperiodism and other rhythmic processes in insects.

Atmospheric chambers have been widely used to study secondary organic aerosol (SOA) properties and formation from various precursors under different controlled environmental conditions and to develop parameterization to represent SOA formation in chemical-transport models (CTM). Chamber experiments are however limited in number, performed under conditions that differ from the atmosphere and can be subject to potential artifacts from chamber walls. Here the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) modelling tool has been used in a box model under various environmental conditions to (i) explore the sensitivity of SOA formation and properties to changes on physical and chemical conditions and (ii) to develop a Volatility Basis Set type parameterization. The set of parent hydrocarbons includes n-alkanes and 1-alkenes with 10, 14, 18, 22, and 26 carbon atoms, α-pinene, β-pinene and limonene, benzene, toluene, o-xylene, m-xylene and p-xylene. Simulated SOA yields and their dependences on the precursor structure, organic aerosol load, temperature and NOx levels are consistent with the literature. GECKO-A was used to explore the distribution of molar mass, vaporization enthalpy, OH reaction rate and Henry's law coefficient of the millions of secondary organic compounds formed during the oxidation of the different precursors and under various conditions. From these explicit simulations, a VBS-GECKO parameterization designed to be implemented in 3D air quality models has been tuned to represent SOA formation from the 18 precursors using GECKO-A as a reference. Its evaluation shows that VBS-GECKO captures the dynamic of SOA formation for a large range of conditions with a mean relative error on organic aerosol mass temporal evolution lesser than 20 % compared to explicit simulations. The optimization procedure has been automated to facilitate the update of the VBS-GECKO on the basis of the future GECKO-A versions, its extension to other precursors and/or its modification to carry additional information.

NO X is one of the main compositions in the modern engine emissions and the reduction requirements of NO X have turned to be more stringent. To control NO X emissions better, the technologies of NO X sensors are forced to achieve much faster response and higher accuracy. In this paper, the correlation between ion current signals and NO X emissions has been investigated by both experiments and simulations based on a direct-injection controlled auto-ignition (CAI) engine, which could provide a novel method to detect NO X emissions within combustion cycle. The simulation results presented this positive correlation from the chemical kinetics point of view, which could also directly reflect the formation order of the chemical products and the influence of temperature on the rates of main ionization and NO X generated reactions. Furthermore, the distributions of both ions and NO products have been shown with the CFD results, to illustrate their in-cylinder space correlation. Combined with the simulation results, the experimental results not only validated the positive correlation with two different fuels, but also provided the evidences fitting linear function. Based on the results, the cycle-based NO X emissions were estimated.

© 2016 The Combustion Institute. This paper improves the tetraethoxysilane (TEOS) oxidation mechanism proposed by Nurkowski et al. (2015) [17] by refining the rate parameters of the key reaction channels in the mechanism. A skeletal version of the mechanism is proposed for hydrogen-oxygen environment. The rates of ethylene-loss from (tetra-, tri-, di- and dimethyldi-) ethoxysilane are computed using transition state theory. The energetics of the main pathways are refined by performing detailed ab initio calculations using the CBS-Q technique. An analysis of ethanol formation via silicates is also performed resulting in the addition of 27 new silica species to the model. Thermodynamic properties for these species are calculated via the balanced reactions method. Reasonably good agreement between the improved model and available experimental data is observed. The subsequent elimination of unimportant species and reactions is achieved via a three-stage reduction procedure. The first and second stages involve the Direct Relation Graph with Error Propagation (DRGEP) method, whereas the third stage analyses rate of progress of each reaction. The investigated conditions are taken from the experimental studies of TEOS oxidation in oxygen-hydrogen flames. The final skeletal mechanism comprises 70 species and 457 reactions and retains good reproduction of the key model properties across the chosen operating conditions as compared to the full mechanism.

The Leuven Isoprene Mechanism, proposed earlier to aid in rationalizing the unexpectedly high hydroxyl radical (OH) concentrations in isoprene-rich, low-nitric-oxide (NO) regions (Peeters et al. Phys. Chem. Chem. Phys. 2009, 11, 5935), is presented in an upgraded and extended version, LIM1. The kinetics of the crucial reactions in the proposed isoprene-peroxy radical interconversion and isomerisation pathways are re-evaluated theoretically, based on energy barriers computed at the much higher CCSD(T)/aug-cc-pVTZ//QCISD/6-311G(d,p) level of theory, and using multi-conformer partition functions obtained at the M06-2X/6-311++G(3df,2p) level that, different from the B3LYP level used in our earlier work, accounts for the crucial London dispersion effects in the H-bonded systems involved. The steady-state fraction of the specific Z-δ-OH-peroxy radical isomers/conformers that can isomerise by 1,6-H shift is shown to be largely governed by hydrogen-bond strengths, while their isomerisation itself is found to occur quasi-exclusively by hydrogen atom tunneling. The isomer-specific Z-δ-OH-peroxy 1,6-H shift rate coefficients are predicted to be of the order of 1 s-1 at 298 K, but the experimentally accessible bulk rate coefficients, which have to be clearly distinguished from the former, are two orders of magnitude lower due to the very low Z-δ-OH-peroxy steady-state fractions that are only around or below 0.01 at low to moderate NO and depend on the peroxy lifetime. Two pathways subsequent to the peroxy radical 1,6-H shift are identified, the earlier predicted route yielding the photolabile hydroperoxy-methyl-butenals (HPALDs), and a second, about equally important path, to di-hydroperoxy-carbonyl peroxy radicals (di-HPCARP). Taking this into account, our predicted bulk peroxy isomerisation rate coefficients are about a factor 1.8 higher than the available experimental results for HPALD production (Crounse et al. Phys. Chem. Chem. Phys. 2011, 13, 13607), which is within the respective uncertainty margins. We also show that the experimental temperature dependence of the HPALD production rates as well as the observed kinetic isotope effect for per-deuterated isoprene support quantitatively our theoretical peroxy interconversion rates. Global modeling implementing LIM1 indicates that on average about 28% of the isoprene peroxys react via the 1,6-H shift isomerisation route, representing 100 - 150 Tg carbon per year. The fast photolysis of HPALDs we proposed earlier as primary OH regeneration mechanism (Peeters and Muller, Phys. Chem. Chem. Phys. 2010, 12, 14227) found already experimental confirmation (Wolfe et al. Phys. Chem. Chem. Phys. 2012, 14, 7276); based on further theoretical work in progress, reaction schemes are presented of the oxy co-product radicals from HPALD photolysis and of the di-HPCARP radicals from the second pathway following peroxy isomerisation that are both expected to initiate considerable additional OH recycling. Invited Feature Article, with journal cover ispartof: Journal of Physical Chemistry A vol:118 issue:38 pages:8625-8643 ispartof: location:United States status: published

In this study, the mechanism of the xanthine oxidase (XO) inhibitory activity of pyrogallol, the main inhibitor found in roasted coffee, was investigated. Pyrogallol was unstable and readily converted to purpurogallin in a pH 7.4 solution, a physiological model of human body fluids. The XO inhibitory activity of the produced purpurogallin was higher than that of pyrogallol, as evidenced by comparing their IC50 values (0.2µmolL-1 for purpurogallin, 1.6µmolL-1 for pyrogallol). The XO activity of pyrogallol was enhanced by pre-incubation in pH 7.4 solution. Although the initial XO inhibitory activity of 4-methylpyrogallol was weak (IC50 33.3µmolL-1), its XO inhibitory activity was also enhanced by pre-incubation in the pH 7.4 solution. In contrast, 5-methylpyrogallol, which could not be transformed into corresponding purpurogallin derivatives, did not show XO inhibitory activity before or after incubation in pH 7.4 solution. Molecular docking simulations clarified that purpurogallins have stronger affinities for XO than corresponding pyrogallols. These results revealed that the potent XO inhibitory activity seemingly observed in pyrogallol is actually derived from its chemical conversion, under alkaline conditions, into purpurogallin.

Spray ignition and flame stabilisation in the frame of diesel-like combustion conditions combine fundamental and complex physical and chemical processes. In this work, a numerical investigation has been performed to evaluate the potential of integrating detailed chemistry into CFD calculations, in order to improve predictions and gain more insight in involved processes. This work has been carried out using the capabilities of OpenFOAM ©code, which provides an opensource framework for 3D-CFD simulations, including an ODE solver for solving chemical kinetics. As a general methodology, this study is based on simulating free n-heptane sprays injected into a constant volume vessel, corresponding to the conditions of the experimental database provided by Sandia National Laboratories. Calculations results have been compared to experiments, evaluating the effect of a wide range of ambient conditions on spray ignition and combustion characteristics. Specifically, this research checks the performance of some relevant n-heptane oxidation mechanisms found in the literature, with different degree of complexity, for modelling the chemical history of the fuel. The results of this investigation show the relative influence of chemical mechanism on spray/flame structure in terms of ignition delay and also ignition and flame stabilisation sites. The comprehensive mechanism performs generally better than more simplified chemistry models. However, its accuracy is also compromised for modelling advanced diesel-like combustion concepts based on injecting the spray into a low oxygen concentration environment. © 2010 Elsevier Ltd.

Numerical investigation of laminar counterflow premixed methane-hydrogen-air flames at a low strain rate is presented. Simulations are carried out with a numerical model incorporated with C2 chemical mechanism having 25 species and 121 reaction steps, and with an optically thin radiation submodel. The numerical model is validated using the experimental data reported in the literature in terms of temperature and species concentrations in flames from opposed flow premixed methane-air and hydrogen-air streams. Parametric studies are performed for opposed flowing methanehydrogen and air mixtures. A premixed methane-hydrogen and air with a rich mixture equivalence ratio (1.75) flows from the top duct, and one having a lean mixture equivalence ratio (0.25) flows from the bottom duct. The volumetric fraction of hydrogen in the fuel mixture has been varied from 20 to 80%. The strain rate used in the present study is kept constant at 50 s -1. Variation of velocity, temperature, species concentrations, and net reaction rates of oxygen, methane and hydrogen along the axis for various cases are presented and discussed in detail. Double flame zones are observed for all the cases. The addition of hydrogen to the rich side stream is seen to be effective in modifying the extents of both reaction zones. The reaction rate of methane is seen to be enhanced with the addition of hydrogen. � 2011 by Begell House, Inc.

Numerical investigations of burning and emission characteristics of laminar methane diffusion flames in a coflowing preheated oxidizer are presented. The preheated oxidizer stream contains hot products of combustion, such as carbon dioxide and water vapor, along with oxygen and nitrogen, and is equivalent to that obtained in an exhaust gas recirculation process. Numerical simulations are carried out using a numerical model incorporated with a C2 chemical mechanism having 25 species and 121 reactions and an optically thin radiation submodel. The numerical results are validated against the experimental results for methane-air coflow flames reported in the literature. Parametric studies have been carried out by changing the temperature and composition of the coflowing oxidizer stream. The effects of these parameters on flame height, flame stability, and emission characteristics are analyzed. It is observed that the increase in the temperature of the oxidizer has a stabilizing effect on the flame, even with a lesser concentration of oxygen in the oxidizer. By investigating the stable flame cases in which a maximum temperature of around 2000 K is achieved, it can be concluded that the preheated oxidizer stream (higher temperature and reduced oxygen) helps in significant reduction of emissions such as nitric oxide and carbon monoxide. � 2010 by Begell House, Inc.

cited By 18; International audience; Carbon multi-walled nanotubes (MWCNTs) may have several dangerous effects on different cell systems, but the mechanisms responsible for their cytotoxicity are not well known yet. At present, very little is known about the electrical interactions between nanomaterials and cells. We aimed to verify whether MWCNT electrical properties could affect the so called "charge-sensitive" cell parameters, interacting with cellular electrical activity. Human macrophages were challenged with two fully characterised MWCNT samples, one tested as-prepared (MWCNT), the other one purified (by annealing at 2400 °C) and better electro-conductive (a-MWCNT). Our findings show that a-MWCNTs are less cytotoxic but possess a higher inflammatory potential, as compared to MWCNTs. Moreover, only annealed and better conductive MWCNTs affect significantly the mitochondrial membrane polarity, the intracellular pH and the reorganisation of cytoskeleton actin filaments, cell functions strictly dependent on electro-chemical mechanisms. Based on our results, there is evidence for electro-chemical interactions taking place between cell membranes and electro-conductive MWCNTs. Such a specific behaviour could have wide-range applications in the biomedical field, not only concerning those cellular systems (neuronal and bone cells) sensitive to electrical stimuli, but also other cell systems.

Fourier transform Raman (FT-Raman) spectra of neat pyridine (Py) and surface enhanced Raman scattering (SERS) spectra of Py with silver nanoparticles (AgNPs) solution at different molar concentrations (X = 1.5 M, 1.0 M, 0.50 M, 0.25 M, and 0.125 M) were recorded using 1064 nm excitation wavelength. The intensity of Raman bands at similar to 1003 (nu(11)) and similar to 1035 (nu(21)) cm(-1) of Py is enhanced in the SERS spectra. Two new Raman bands were observed at similar to 1009 (nu(12)) and similar to 1038 (nu(22)) cm(-1) in the SERS spectra. These bands correspond to the ring breathing vibrations of Py molecules adsorbed at the AgNPs surface. The value of intensity ratios (I-12/I-11) and (I-21/I-22) is increased with dilution and attains a maximum value at X = 0.5 M and upon further dilution (0.25 and 0.125 M) it drops gradually. The theoretically calculated Raman spectra were found to be in good agreement with experimentally observed Raman spectra. Both, experimental and theoretical investigations have confirmed that the Py interacts with AgNPs via the end-on geometry. (C) 2015 Elsevier B.V. All rights reserved.

Acetohydroxy acid synthase (AHAS) is one of several enzymes that require thiamine diphosphate and a divalent cation as essential cofactors. Recently, the three-dimensional structure of the enzyme from yeast has been determined [Pang et al., J. Mol. Biol. 317 (2002) 249–262]. While this structure sheds light on the binding of the cofactors and the reaction mechanism, the interactions between the substrates and the enzyme remain unclear. We have studied the pH dependence of kinetic parameters in order to obtain information about the chemical mechanism in the active site. Data are consistent with a mechanism in which substrate selectively catalyzed to the enzyme with an unprotonated base having a p K of 6.48, and a protonated group having a p K of 8.25 for catalysis. The temperature dependence of kinetic parameters was pH-dependent, and the enthalpies of ionization, Δ H ion , calculated from the slope of p K 1 and p K 2 are both pH-independent. The solvent perturbation of kinetic parameters was pH-dependent, and the p K 1 from the acidic side and the p K 2 from the basic side were shifted down 0.4 pH units and shifted up 0.6 units as water was replaced by 15% ethanol, respectively. The data are discussed in terms of the acid–base chemical mechanism.

Log wood burning is a significant source of volatile organic compounds including aromatic hydrocarbons (ArHC). ArHC are harmful, are reactive in the ambient atmosphere, and are important secondary organic aerosol (SOA) precursors. Consequently, SOA represents a major fraction of the sub-micron organic aerosol pollution from log wood burning. ArHC reduction is thus critical in the mitigation of adverse health and environmental effects of log wood burning. In this study, two Pt-based catalytic converters were prepared and tested for the mitigation of real-world log wood burning emissions, including ArHC and SOA formation, as well as toxic carbon monoxide and methane, a greenhouse gas. Substantial removal of mono- and polycyclic ArHC and phenolic compounds was achieved with both catalysts operated at realistic chimney temperatures (50% conversion was achieved at 200 and 300 degrees C for non-methane hydrocarbons in our experiments for Pt/Al2O3 and Pt/CeO2-Al2O3, respectively). The catalytically cleaned emissions exhibited a substantially reduced SOA formation already at temperatures as low as 185-310 degrees C. This reduces the sub-micron PM burden of log wood burning significantly. Thus, catalytic converters can effectively reduce primary and secondary log wood burning pollutants and, thereby, their adverse health impacts and environmental effects.

Surface-enhanced Raman spectroscopy (SERS) coupled with density functional theory (DFT) computations can characterise the adsorption orientation of a molecule on a nanoparticle surface. When using DFT to simulate SERS on a silver surface, one typically employs an atom (Ag), ion (Ag+), or cluster (Ag-x or Ag-x(+)) as the model surface. Here, by examining the nucleobase 2,6-diaminopurine (2,6-DAP) and then generalising our strategy to three other molecules, we show that employing silver oxide (Ag2O) as the model surface can quantitatively improve the accuracy of simulated SERS.