The Effect of Cyclodextrins in Polymer Particles Synthesis

The free radical polymerization of styrene in water in the presence of β-cyclodextrin (β-CD) is described.It is found that β-CD could greatly accelerate the polymerization,enhance the final conversion of monomer.The particle-size distribution of the final polymer is also improved than that without β-CD in the system.     

Synthesis of Monodisperse α-Fe2O3 Particles in Short Periods

Asanimportantmaterialusedformagnetic,pigment,catalysis,gas-sensitiveandmedicalimagingapplications,monodispersehematite(a-Fe2O3)particleshaveattractedmoreattentionsinrecentyears1,2.Althoughvariousmorphologica-Fe2O3particleshavebeensynthesizedbyforcedhydrolysisprocess3,4,inwhichthepropertiesofa-Fe2O3particlesvaryconsiderablywithalargenumberofsynthesisparameterssuchaspH,theconcentrationofreactants,thecoexistentanionsetc.,thereisalackofmethodforpreparingmonodispersea-Fe2O3particlesinshortperiod…     

The Cytotoxic Effect of α-Synuclein Aggregates

Parkinson's disease is a neurodegenerative disorder involving a functional protein, α-synuclein, whose primary function is related to vesicle trafficking. However, α-synuclein is prone to form aggregates, and these inclusions, known as Lewy bodies, are the hallmark of Parkinson's disease. α-synuclein can alter its conformation and acquire aggregating capacity, forming aggregates containing β-sheets. This protein's pathogenic importance is based on its ability to form oligomers that impair synaptic transmission and neuronal function by increasing membrane permeability and altering homeostasis, generating a deleterious effect over cells. First, we establish that oligomers interfere with the mechanical properties of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membrane, as demonstrated by nanoindentation curves. In contrast, nanoindentation revealed that the α-synuclein monomer's presence leads to a much more resistant lipid bilayer. Moreover, the oligomers’ interaction with cell membranes can promote lactate dehydrogenase (LDH) release, suggesting the activation of cytotoxic events.     

Stability of Suspensions of Bioactive Particles Using Hybrid Organic–Inorganic Solutions as Dispersing Media

Functional coatings incorporating different types of particles developed by the sol–gel method have been proposed in the last few years for diverse applications. This work focuses on the preparation of homogeneous coatings prepared from stable suspensions with 10 wt% of glass and glass ceramic particles in a hybrid organic–inorganic solution as dispersing media. For this purpose, the pH was shifted up to 6–7 by adding tetrapropylammonium hydroxide (TPAH) which behaves as a cationic surfactant being probably adsorbed on the particles surface, while the sol maintains stable. Rheological measurements were performed to study the stability of the suspensions prepared at different conditions such as the kind and concentration of dispersant and the pH conditions. After sintering at 450^∘C/30 min, coatings around 2 μ m in thickness were obtained.     

The Effect of Silver Perchlorate of the Reaction of Trialkyl Phosphite with α-Halogenoketones

Abstract

Trialkyl phosphites are known to react with α-halogenoketones to yield β-ketophosphonates (Arbuzov product) or vinyl phosphates (Perkow product) according to coniiitions.¹ α-Hydroxyphosphonate may be formed in addition, in prcltic media.² We have now shown that none of these products is formed in the presence of silver perchlorate (in benzene sclutim); nor could we detect the ketophosphonium perchlorate reported previously. Phosphorus-31 nmr showed the formation of trimethyl phosphate and tetramethyl pyrophosphate as the exclusive phosphorus-containing products. The sequence of possible reaction is complex and the overall stoichiometry may vary somewhat according to the rate and order of rixing. Trialkyl phosphate could be formed by elimination of alkyne from vinyloxyphosphonium intermediate produced together with silver iodine in first stage of the interaction. Pyrophosphate formation would then result from nucleophilic attack of trimethyl phosphate on the trimethoxy(1-nethylvinyloxy)phosphoniun ion, which may be formed as a reactive intermediate. Evidence for formation of methyl perchlorate in the final dealkylation of the quasiphosphonium intermediate is provided by proton nmr spectroscopy and by the formation of the N-methylquino-linium salt on addition of quinoline. No change in the ³¹P nmr spectrum occurs at this stage. Other by-products of the main reactions include the dehalogenated ketone (acetone from iodoacetone or acetnphenone from α-iodoacetophenone).     

Effect of Temperature on The Solubility of α-Amino Acids and α,ω-Amino Acids in Water

The aqueous solubilities of glycine, dl-α-alanine (2-aminopropanoic acid), dl-α-aminobutyric acid (2-aminobutanoic acid), dl-α-norvaline (2-aminopentanoic acid), dl-α-norleucine (2-aminohexanoic acid), β-alanine (3-aminopropanoic acid), γ-aminobutyric acid (4-aminobutanoic acid), 5-aminovaleric acid (5-aminopentanoic acid), and 6-aminocaproic acid (6-aminohexanoic acid) were determined from 293.15 to 323.15 K at intervals of 5.00 K using the gravimetric method. The temperature dependence of the solubility of α-amino acids and α,ω-amino acids in water is well described by the van’t Hoff equation. Linear van’t Hoff plots were used to determine the differential enthalpy of solution. The results obtained are compared with reported values in literature and are discussed in terms of the position of the ionic groups in the hydrocarbon chain.     

Covalent Immobilization of β-Glucosidase on Magnetic Particles for Lignocellulose Hydrolysis

β-Glucosidase hydrolyzes cellobiose to glucose and is an important enzyme in the consortium used for hydrolysis of cellulosic and lignocellulosic feedstocks. In the present work, β-glucosidase was covalently immobilized on non-porous magnetic particles to enable re-use of the enzyme. It was found that particles activated with cyanuric chloride and polyglutaraldehyde gave the highest bead-related immobilized enzyme activity when tested with p-nitrophenyl-β-D-glucopyranoside (104.7 and 82.2 U/g particles, respectively). Furthermore, the purified β-glucosidase preparation from Megazyme gave higher bead-related enzyme activities compared to Novozym 188 (79.0 and 9.8 U/g particles, respectively). A significant improvement in thermal stability was observed for immobilized enzyme compared to free enzyme; after 5 h (at 65 °C), 36 % of activity remained for the former, while there was no activity in the latter. The performance and recyclability of immobilized β-glucosidase on more complex substrate (pretreated spruce) was also studied. It was shown that adding immobilized β-glucosidase (16 U/g dry matter) to free cellulases (8 FPU/g dry matter) increased the hydrolysis yield of pretreated spruce from ca. 44 % to ca. 65 %. In addition, it was possible to re-use the immobilized β-glucosidase in the spruce and retain activity for at least four cycles. The immobilized enzyme thus shows promise for lignocellulose hydrolysis.     

Effect of Chemical Treatment on TiO2 Particles by IMPS

The photodegradation reaction rate of CHCl3 in TiO2 particulate suspension was imperoved significantly by HCl-treatment.The effect of HCl-treatment on the photocatalytic activity of TiO2 was strdied in a PEC cell by using Intensity-Modulated Photocurrent Spectroscopy(IMPS).The magntude of photocurrent response and the characteristic frequencies of the upper and lower semicircles in the complex plane of IMPS response were analyzed,and the ccathodic and anodic reaction processes of photogenerated holes and electrons were discussed.The increases in the cathodic and anodic photocurrent response and in the time constants of both cathodic and anodic reaction processes of photogenerated holes and electrons were discussed.The increases in the cathodic and anodic photocurrent response and in the time constants of both cathodic and anodic reaction processes indicate that HCl-treatment leads to the improvement of the photocatalytic activity of TiO2 and a change of the photocatalytic kinetic mechanism.     

Magnetic and electronic properties of α-graphyne nanoribbons

Based on the first-principles calculations, we investigate the magnetic and electronic properties of α-graphyne nanoribbons (NRs). We show that all the armchair α-graphyne NRs are nonmagnetic semiconductors with band gaps as a function of ribbon widths. The zigzag α-graphyne NRs are found to have magnetic semiconducting ground state with ferromagnetic ordering at each edge and opposite spin orientation between the two edges. Under the application of transverse electric field, we further predict the existence of half-metallicity in the zigzag NRs which strongly depends on the width of the ribbon.     

Enhanced photochemical activity of α-Fe2O3 films supported on SrTiO3 substrates under visible light illumination

The visible light photochemical reactivity of a 50 nm thick α-Fe(2)O(3)(0001) (hematite) film on a SrTiO(3)(111) substrate is compared to the reactivities of bulk hematite and the same film supported by α-Al(2)O(3)(0001). The hematite film supported by SrTiO(3)(111) is far more reactive then the other two cases.     

The Aggregation Kinetics of Colloidal Particles of Basic Yttrium Carbonate

Studyofthegrowthprocessofcolloidalparticlesofnonequilibriumandirreversibilityisanactiveareaofresearch.Therecognitionofcolloidalaggregatesasfractalobjectshasinspiredalargenumberofexperimentalandtheoreticalstudiesonthestructuralandkineticaspectsofaggregationprocesses"'.Morerecently,kineticsofhematiteaggregationbypolyacrylicacidhavebeenstudiedbyzhangandBume3.Theprimaryhematiteparticleswerequiteuniformandfairlyspherical.Inthispaper,wewillreportthesizeevolutionoffractalaggregatesofinitiallypolydis…     

Dynamic Nuclear Polarization in Suspensions Consisting of Xylene Isomers and Asphaltene Extracted from MC‐800 Liquid Asphalt

Overhauser effect type dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in the xylene isomers (o‐, m‐, p‐) at a low magnetic field of 1.44 mT and three different temperatures (15, 25, and 35°C). The asphaltene was extracted from MC‐800 liquid asphalt. Intermolecular spin‐spin interactions occur between nuclear spins of hydrogen in the solvent medium and the free electron spins in the asphaltene micelles. The electron paramagnetic resonance spectrum of the asphaltene was obtained and the saturation experiments were applied to the samples prepared in vacuum. For all media, the dipole‐dipole interaction is predominant due to the negative signal enhancements. In all temperatures, the ultimate enhancement is the smallest for the p‐xylene solvent medium which has the lowest electrical dipole moment. The normalized low frequency relaxation components were calculated for 25°C, and the behavior of the nuclear‐electron coupling parameter according to this component is in agreement with the other works in the literature.     

Effect of MnO2 and α-Fe2O3 on organic binders degradation investigated by Raman spectroscopy

Vibrational spectroscopy and GC–MS were used to investigate the effect of MnO₂ and α-Fe₂O₃ on the degradation of methyl linoleate and vegetal and animal fatty. The metal oxides are among the most employed pigments in rock art paintings, whereas the organic compounds were used to mimic organic binders potentially used in such paintings.Both oxides were very effective in the catalytic oxidation of the organic substrates and light had no significant effect, qualitatively or quantitatively, on the final products. In the case of methyl linoleate without metal oxide, the effect of light (visible) was investigated and it was demonstrated that the samples kept in the dark produced relatively less oxidation products, although the main products were the same (hexanal, methyl 9-oxononanoate and methyl octanoate). In the presence of MnO₂ and α-Fe₂O₃ methyl 9-oxononanoate was the main product, followed by hexanal. The spectral patterns of the oxidation products were different for manganese and iron oxide and GC–MS demonstrated that more compounds are formed in the former than with α-Fe₂O₃. Vegetal and animal fatty presented the same behavior that methyl linoleate did.The results here reported indicated that the two pigments considered actively contribute to fat degradation and the presence of inorganic pigments is the main factor to take into account when organic binders degradation in rock art paintings are investigated.     

Preparation of Fe_3O_4/PS Magnetic Particles by Dispersion Polymerization

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The role of cobalt phosphate in enhancing the photocatalytic activity of α-Fe2O3 toward water oxidation

Transient absorption spectroscopy was used to probe the dynamics of photogenerated charge carriers in α-Fe(2)O(3)/CoO(x) nanocomposite photoelectrodes for water splitting. The addition of cobalt-based electrocatalysts was observed to increase the lifetime of photogenerated holes in the photoelectrode by more than 3 orders of magnitude without the application of electrical bias. We therefore propose that the enhanced photoelectrochemical activity of the composite electrode for water photooxidation results, at least in part, from reduced recombination losses because of the formation of a Schottky-type heterojunction.     

The Fascinating Chemistry of α-Haloamides

The aim of this review is to highlight the rich chemistry of α-haloamides originally mainly used to discover new C−N, C−O and C−S bond forming reactions, and later widely employed in C−C cross-coupling reactions with C(sp³), C(sp²) and C(sp) coupling partners. Radical-mediated transformations of α-haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α-halohydroxamate-based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates.     

The gas-phase ozonolysis of α-humulene

α-Humulene contains three double bonds (DB), and after ozonolysis of the first DB the first-generation products are still reactive towards O(3) and produce second- and third-generation products. The primary aim of this study consisted of identifying the products of the three generations, focusing on the carboxylic acids, which are known to have a high aerosol formation potential. The experiments were performed in a 570 litre spherical glass reactor at 295 K and 730 Torr. Initial mixing ratios were 260-2090 ppb for O(3) and 250-600 ppb for α-humulene in synthetic air. Reactants and gas-phase products were measured by in situ FTIR spectroscopy. Particulate products were sampled on Teflon filters, extracted with methanol and analyzed by LC-MS/MS-TOF. Using cyclohexane (10-100 ppm) as an OH-radical scavenger and by monitoring the yield of cyclohexanone by PTR-MS, an OH-yield of (10.5 ± 0.7)% was determined for the ozonolysis of the first DB, and (12.9 ± 0.7)% of the first-generation products. The rate constant of the reaction of O(3) with α-humulene is known as k(0) = 1.17 × 10(-14) cm(3) molecule(-1) s(-1) [Y. Shu and R. Atkinson, Int. J. Chem. Kinet., 1994, 26, 1193-1205]. The reaction rate constants of O(3) with the first-generation products and the second-generation products were, respectively, determined as k(1) = (3.6 ± 0.9) × 10(-16) and k(2) = (3.0 ± 0.7) × 10(-17) cm(3) molecule(-1) s(-1) by Facsimile-simulation of the observed ozone decay by FTIR. A total of 37 compounds in the aerosol phase and 5 products in the gas phase were tentatively identified: 25 compounds of the first-generation products contained C13-C15 species, 9 compounds of the second-generation products contained C8-C11 species, whereas 8 compounds of the third-generation products contained C4-C6 species. The products of all three generations consisted of a variety of dicarboxylic-, hydroxy-oxocarboxylic- and oxo-carboxylic acids. The formation mechanisms of some of the products are discussed. The residual FTIR spectra indicate the formation of secondary ozonides (SOZ) in the gas phase, which are formed by the intramolecular reaction of the Criegee moiety with the carbonyl endgroup. These SOZ revealed to be stable over several hours and its formation was shown not to be affected by the addition of Criegee-radical scavengers such as HCOOH or H(2)O. This suggests that in the ozonolysis of α-humulene at atmospheric pressures the POZ will decompose rapidly, and that a large fraction of the formed exited Criegee Intermediate will be stabilized to form stable SOZ, while the formation of OH-radicals via the hydroperoxide channel will be a minor process.     

Effect of Nano-anatase TiO2 on Spectral Characterization of Photosystem Ⅱ Particles from Spinach

The photosystem Ⅱ (PS Ⅱ ) particles were purified by means of nano-anatase TiO2 treatment of spinach and studied by spectroscopy. The results show that the electron transport and the oxygen-evolving rate of PS Ⅱ are accelerated after it has been treated with nano-anatase TiO2; the UV-Vis absorption spectrum of PS Ⅱ particles is increased; the red shift of fluorescence emission peak of PS Ⅱ is 2 nm; the peak intensity is decreased; the PS Ⅱ signal Ⅱ s of low temperature electron paramagnetic resonanace(EPR) spectrum is intensified under light, and the PS Ⅱ circular dichroism(CD) spectrum is similar to that of control. It is suggested that nano-anatase TiO2 might bind to the PS Ⅱ reaction center complex and intensify the function of the PS Ⅱ electron donor, however, nano-anatase TiO2 treatment does not change the configuration of the PS Ⅱ reaction center complex.     

Effect of Acridine Derivatives on the Dissolution of α-Brass

Acridine derivatives as inhibitors of diffusion- and diffusion–kinetic-controlled dissolution of -brass are studied. Inhibition coefficients of the dissolution and its steps correlate with parameters of a standard reaction series and wavelengths of the longest-wave absorption band of the electronic spectrum.