Investigation of the competitive rate of derivatization of several secondary amines with phenylisocyanate (PHI), hexamethylene-1,6-diisocyanate (HDI), 4,4'-methylenebis(phenyl isocyanate) (MDI) and toluene diisocyanate (TDI) in liquid medium

The stabilization of the isocyanate (NCO) groups during workplace sampling is necessary for their subsequent laboratory analysis. Most derivatization reagents are secondary amines. By carrying out a test in which two secondary amines are added to an isocyanate, the relative rates of these reactions can be evaluated. This evaluation is known for a monoisocyanate, phenylisocyanate (PHI), but is being developed for diisocyanates. This study deals with the relative reactivity (RR) of four diisocyanates: hexamethylene 1,6-diisocyanate (HDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), and the ortho and para isomers of toluene diisocyanate (TDI) in addition to PHI, with four secondary amines: 1-(2-methoxyphenyl)piperazine (MOPIP), 9-(N-methylaminomethyl)anthracene (MAMA), 1-(9-anthracenylmethyl)piperazine (MAP), and dibutylamine (DBA). These competitive derivatization reactions are studied in three reaction solvents, namely acetonitrile, toluene, and acetonitrile doped with water (1% v/v). The results show that the order of reactivity, which doesn't change with the isocyanate as well as with the solvent used, is the following: DBA > MAP > MOPIP > MAMA. The relative difference in reactivity is a function of both the isocyanate and the solvent used. Hindered aromatic diisocyanates (TDI and MDI) show a greater difference in reactivity with the derivatization agents. These differences in reactivity are also modified by the solvent used. For example, larger differences are observed in acetonitrile than in toluene, but the introduction of water to acetonitrile, which does not affect the reaction yield, makes these differences smaller.     

Anhydrous oxygen-free rare earth material preparation and characterization

The present paper addresses the preparation and characterization of anhydrous oxygen-free rare earth materials, such as terbium fluoride (TbF₃). The fluorination of terbium oxide (Tb₄O₇) by ammonium bifluoride (NH₄HF₂) to prepare anhydrous TbF₃ was reported in this work. The parameters affecting fluorination were studied, including the fluorination temperature, excess stoichiometric amount of NH₄HF₂, and time for fluorination. The temperatures of Tb₄O₇ fluorination by NH₄HF₂ determined by thermogravimetric analysis and differential thermal analysis ranged from 350°C to 500°C. The phase structure of the as-prepared products identified by the X-ray diffraction method was indexed to the orthorhombic phase of TbF₃ [space group: Pnma (no. 62)] that exhibited good accordance with the values in the standard cards JCPDS No. 37-1487 for TbF₃. Energy-dispersive X-ray spectroscopy (EDS) methods were used to analyze the elemental compositions in the as-prepared products; the fluorine (F) and terbium (Tb) elemental compositions calculated from the [TbF₃] formula are in good agreement with those calculated from the EDS pattern. The optimum parameters for fluorination were determined from the results, and anhydrous oxygen-free TbF₃ can be used to study the preparation of metallic terbium by the calcinothermic reduction method.     

Rapid microwave assisted esterification method for the analysis of poly-3-hydroxybutyrate in Alcaligenes latus by gas chromatography

In the present study, we used microwave energy instead of conventional heating to transform poly-3-hydroxybutyrate (PHB) into methyl 3-hydroxybutyrate (Me-3HB) in acidified methanol (H2SO4, 10%, v/v) mixture in less than 4 min at 10% microwave power. The microwave assisted method was then applied to analyze PHB produced by Alcaligenes latus. The PHB content in the biomass determined using microwave heating was comparable to the amount found by conventional heating. Moreover, the new esterification method was at least 50 times faster than the conventional method, affording a significant saving of time and energy.     

Stabilizing the nonlinear spherically symmetric backward heat equation via two-parameter regularization method

In this paper, we consider a time-inverse problem for a nonlinear spherically symmetric backward heat equation which is a severely ill-posed problem. Using a modified integral equation method with two regularization parameters: one related to the error in a measurement process and the other is related to the regularity of solution, we regularize this problem and obtain the Hölder-type estimation error for the whole time interval. Numerical results are presented to illustrate the accuracy and efficiency of the method.     

The Influence of Temperature and Viscosity of Polyethylene Glycol on the Rate of Microwave-Induced In Situ Amorphization of Celecoxib

Microwaved-induced in situ amorphization of a drug in a polymer has been suggested to follow a dissolution process, with the drug dissolving into the mobile polymer at temperatures above the glass transition temperature (T_g) of the polymer. Thus, based on the Noyes–Whitney and the Stoke–Einstein equations, the temperature and the viscosity are expected to directly impact the rate and degree of drug amorphization. By investigating two different viscosity grades of polyethylene glycol (PEG), i.e., PEG 3000 and PEG 4000, and controlling the temperature of the microwave oven, it was possible to study the influence of both, temperature and viscosity, on the in situ amorphization of the model drug celecoxib (CCX) during exposure to microwave radiation. In this study, compacts containing 30 wt% CCX, 69 wt% PEG 3000 or PEG 4000 and 1 wt% lubricant (magnesium stearate) were exposed to microwave radiation at (i) a target temperature, or (ii) a target viscosity. It was found that at the target temperature, compacts containing PEG 3000 displayed a faster rate of amorphization as compared to compacts containing PEG 4000, due to the lower viscosity of PEG 3000 compared to PEG 4000. Furthermore, at the target viscosity, which was achieved by setting different temperatures for compacts containing PEG 3000 and PEG 4000, respectively, the compacts containing PEG 3000 displayed a slower rate of amorphization, due to a lower target temperature, than compacts containing PEG 4000. In conclusion, with lower viscosity of the polymer, at temperatures above its T_g, and with higher temperatures, both increasing the diffusion coefficient of the drug into the polymer, the rate of amorphization was increased allowing a faster in situ amorphization during exposure to microwave radiation. Hereby, the theory that the microwave-induced in situ amorphization process can be described as a dissolution process of the drug into the polymer, at temperatures above the T_g, is further strengthened.     

Synthesis of Branched‐Chain Sugars with a DHAP‐Dependent Aldolase: Ketones are Electrophile Substrates of Rhamnulose‐1‐phosphate Aldolases

Dihydroxyacetone phosphate (DHAP)‐dependent rhamnulose aldolases display an unprecedented versatility for ketones as electrophile substrates. We selected and characterized a rhamnulose aldolase from Bacteroides thetaiotaomicron (RhuABthet) to provide a proof of concept. DHAP was added as a nucleophile to several α‐hydroxylated ketones used as electrophiles. This aldol addition was stereoselective and produced branched‐chain monosaccharide adducts with a tertiary alcohol moiety. Several aldols were readily obtained in good to excellent yields (from 76 to 95 %). These results contradict the general view that aldehydes are the only electrophile substrates for DHAP‐dependent aldolases and provide a new C?C bond‐forming enzyme for stereoselective synthesis of tertiary alcohols.     

S100A9 in adult asthmatic patients: a biomarker for neutrophilic asthma

The biomarkers and therapeutic targets of neutrophilic asthma (NA) are poorly understood. Although S100 calcium-binding protein A9 (S100A9) has been shown to correlate with neutrophil activation, its role in asthma pathogenesis has not been clarified. This study investigated the mechanism by which S100A9 is involved in neutrophil activation, neutrophil extracellular trap (NET)-induced airway inflammation, and macrophage polarization in NA. The S100A9 levels (by ELISA) in sera/culture supernatant of peripheral blood neutrophils (PBNs) and M0 macrophages from asthmatic patients were measured and compared to those of healthy controls (HCs). The function of S100A9 was evaluated using airway epithelial cells (AECs) and PBNs/M0 macrophages from asthmatic patients, as well as a mouse asthma model. The serum levels of S100A9 were higher in NA patients than in non-NA patients, and there was a positive correlation between serum S100A9 levels and sputum neutrophil counts (r = 0.340, P = 0.005). Asthmatic patients with higher S100A9 levels had lower PC₂₀ methacholine values and a higher prevalence of severe asthma (SA) (P < .050). PBNs/M0 macrophages from SA released more S100A9 than those from non-SA patients. PBNs from asthmatic patients induced S100A9 production by AECs, which further activated AECs via the extracellular signal-regulated kinase (ERK) pathway, stimulated NET formation, and induced M1 macrophage polarization. Higher S100A9 levels in sera, bronchoalveolar lavage fluid, and lung tissues were observed in the mouse model of NA but not in the other mouse models. These results suggest that S100A9 is a potential serum biomarker and therapeutic target for NA.Subject terms: Prognostic markers, Adaptive immunity, Immunological disorders, Diagnostic markers     

Proton magic-angle spinning-NMR investigation of surfactant aqueous suspensions

In this Note we present the advantages of 1H magic-angle spinning nuclear magnetic resonance (MAS-NMR) for the investigation of surfactant suspensions via transverse relaxation rate (R2) measurements. 1H-relaxation rates can be determined by the classical CPMG method from high-resolution spectra obtained either under conditions of liquid-state NMR for monomers and small spherical micelles or by using MAS-NMR for larger aggregates. For a mixture of alkyl dioxyethylene sulfate and alkylbetaine (80:20, w/w), up to a percentage of surfactant in water of 20%, we found that R2 increased, in accordance with an increased micellar size and very likely the formation of an HI phase. However, above 25%, R2 decreased. This result suggests a change from a hexagonal to a lamellar phase that would be difficult to observe by proton NMR without magic-angle spinning because the lines would be very broad, or by light scattering because of sample opacity. This NMR approach seems to have been overlooked by the community of surfactant physical chemists. It can be complementary to other analytical techniques and presents the advantage of not requiring isotopic labeling.     

Volumes of mixing and theP * effect: Part I. Hexane isomers with normal and branched hexadecane

The Prigogine-Flory theory of solution thermodynamics has been used to interpret molar excess volume data, V ^E , for two series of alkane mixtures: the five isomers of hexane mixed with normal hexadecane (Data from Reeder, et al.) and the five hexane isomers mixed with a highly branched hexadecane isomer, 2,2,4,4,6,8,8-heptamethylnonane (this work). Values of V ^E are negative and similar for both series, but vary considerably with the hexane within a series. According to the theory, V ^E contains a P^* contribution not found in the excess enthalpy and entropy, which depends strongly on the internal pressures and the derived P^* parameters of the components. Values of V ^E are well predicted for both series, the variation of V ^E corresponding to the different internal pressures or P^* parameters of the hexanes.