A cost-effective form-stable PCM composite with modified paraffin and expanded perlite for thermal energy storage in concrete

Journal of Thermal Analysis and Calorimetry - High thermal conductivity in phase change materials (PCM) is preferred in thermal energy storage (TES) systems. Carbon additives are considered as...     

A facile and efficient addition reaction of nitrogen‐containing heterocyclic compounds with DMAD under neat conditions

A simple and efficient method was developed for the reaction of dimethyl acetylenedicarboxylate with benzothiazole, isoquinoline, quinoline, 3‐bromopyridine, pyridine, benzoxazole, benzimidazole, and 5,6‐dimethyl benzimidazole for the high‐yield synthesis of the related heterocyclic products ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ) in very short reaction time under neat procedure. The reaction of isoquinoline, 3‐bromopyridine, and pyridine afforded to diastereomeric mixtures of products 2 , 4 , and 5 , respectively. However, only one isomer of products 1 , 3 , 6 , 7 , and 8 were identified from the reaction of benzothiazole, quinoline, benzoxazole, benzimidazole, and 5,6‐dimethyl benzimidazole, respectively. Benzotriazole afforded to product 9 under these conditions. For comparison, the reactions were examined in different reaction mediums and/or under microwave irradiation. J. Heterocyclic Chem., (2011).     

Synthesis,Characterization, and an ab initio Study of a Manganese(II) Macrocyclic Schiff-Base Complex with Two 2-Aminoethyl Pendant Arms

The cyclocondensation of 2,6-diformylpyridine with N,N,N,N-tetrakis(2-aminoethyl)ethane-1,2-diamine (pentene) in the presence of Mn^II forms the [1 + 1] pendant arm Schiff-base macrocyclic complex, [MnL³]²⁺. The ligand is a 15-membered pentaaza macrocycle having two 2-aminoethyl pendant arms {L³= 6,9-bis(aminoethyl)-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentene}. The complex, investigated by analytical, spectroscopic and magnetic techniques, supports the formation of a highly symmetrical pentagonal bipyramid complex with the Mn^II ion located within a pentaaza macrocycle and two pendant amines coordinating on opposite sides of a plane defined by the macrocycle and the metal ion. The structure of the complex was also verified by ab initio HF-MO calculations using a standard 3-21G basis set.     

Synthesis of new enantiomerically pure spirooxindolopyrrolizidines via a three-component asymmetric 1,3-dipolar cycloaddition reaction of azomethine ylides derived from isatin

An efficient, one-pot, three-component procedure for the synthesis of a small library of new chiral spirooxindolopyrrolizidines with high regio-, diastereo-, and enantioselectivity, from the 1,3-dipolar cycloaddition of azomethine ylides and optically active cinnamoyl oxazolidinone is described. The process occurs at room temperature in aqueous ethanol as a green solvent and in the absence of any Lewis acids. The oxazolidinone chiral auxiliary is removed in a non-destructive manner. The reaction mechanism is discussed on the basis of the assignment of the absolute configuration of the cycloadducts, and on theoretical calculations.     

Cellulosic nanoparticles from alfa fibers (<Emphasis Type=Italic>Stipa tenacissima)</Emphasis>: extraction procedures and reinforcement potential in polymer nanocomposites

The microstructure and chemical composition of alfa (Stipa tenacissima) were investigated. The polysaccharide and lignin contents were around 70 and 20 wt%, respectively. From the bleached and delignified fibers, two types of nanosized cellulosic particles were extracted, namely cellulose nanocrystals and microfibrillated cellulose (MFC). The former correspond typically to the elementary crystallite units of the cellulose fibers, with a rod-like morphology and an aspect ratio of about 20. The latter, mechanically disintegrated from oxidized bleached fibres, presents an entangled fibrillar structure with widths in the range 5-20 nm. The reinforcing potential of the ensuing nanoparticles was investigated by casting a mixture of acrylic latex and aqueous dispersion of cellulose nanoparticles. Thermo-mechanical analysis revealed a huge enhancement of the stiffness above the glass transition of the matrix. Significant differences in the mechanical reinforcing capability of the nanoparticles were reported.     

Optimization strategies for radiation induced grafting of 4-vinylpyridine onto poly(ethylene-co-tetraflouroethene) film using Box-Behnken design

The radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(ethylene-co-tetrafluoroethene) (ETFE) was optimized using the Box-Behnken factorial design available in the response surface method (RSM). The optimized grafting parameters; absorbed dose, monomer concentration, grafting time and reaction temperature were varied in four levels to quantify their effect on the grafting yield (GY). The validity of the statistical model was supported by the small deviation between the predicted (GY=61%) and experimental (GY=57%) values. The optimum conditions for enhancing GY were determined at the following values: monomer concentration of 48 vol%, absorbed dose of 64 kGy, reaction time of 4 h and temperature of 68 °C. A comparison was made between the optimization model developed for the present grafting system and that for grafting of 1-vinylimidazole (1-VIm) onto ETFE to confirm the validly and reliability of the Box-Behnken for the optimization of various radiation induced grafting reactions. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to investigate the properties of the obtained films and provide evidence for grafting.     

Conversion of Isoeugenol to Vanillin by <Emphasis Type="Italic">Psychrobacter</Emphasis> sp. Strain CSW4

To screen strains of halotolerant or halophile bacteria which are able to convert isoeugenol to vanillin, 36 different strains of bacteria isolated from the salty environments in Iran were investigated. During growth on isoeugenol, a moderately halotolerant Gram-negative coccobacil showed capability of converting isoeugenol to vanillin. Based on morphological, physiological, and phylogenetic studies, strain CSW4 was classified as a bacterium belonging to the genus Psychrobacter. The bioconversion products were confirmed by thin-layer chromatography, high-performance liquid chromatography, and spectral data obtained from UV/Vis spectroscopy, FTIR, and mass-spectroscopy. Using growing cells, vanillin reached its maximum level of 88.18 mg L⁻¹ after 24 h of reaction time in the presence of 1 g L⁻¹ isoeugenol, resulting in a molar yield of 10.2%. The use of resting cells led to the optimal yield of vanillin (16.4%) which was obtained after 18-h reaction using 1 g L⁻¹ isoeugenol and 3.1 g of dry weight of cells per liter harvested at the end of the exponential growth phase. To improve vanillin yield, the effect of substrate concentration on vanillin production under resting cells conditions was also investigated. Using 10 g L⁻¹ isoeugenol, the maximal vanillin concentration (1.28 g L⁻¹) was achieved after a 48-h reaction, without further optimization. The present study brings the first evidence for biotransformation of isoeugenol to vanillin in the genus Psychrobacter.     

Fast quality assessment of German chamomile (Matricaria chamomilla L.) by headspace solid-phase microextraction: influence of flower development stage

For an adequate quality evaluation of aromatic plants grown under different conditions, a rapid, simple and sensitive method for the analysis of volatile constituents is indispensable. The main objective of the present study was to compare fast screening of German chamomile (Matricaria chamomilla L.) by means of headspace solid-phase microextraction (HS-SPME) with conventional isolation of the essential oil (steam distillation-solvent extraction (SDSE)) for the differentiation of chamomile essential oil constituents. Flowers were harvested at two distinct development stages: stage I, when ligulate flowers start to develop and tubular flowers are still closed, and stage II, when tubular flowers are partially to completely opened. Dried chamomile flowers at two development stages were extracted by means of both SDSE and HS-SPME, followed by GC-MS analysis. Among 30 compounds detected, (E)-beta-farnesene (49%), artemisia ketone (10%) and germacrene D (9%) were the predominant volatile components in the HS-SPME-extract, while alpha-bisabolol oxide A (42%), chamazulene (21%) and (Z)-spiroether (8%) were the main essential oil constituents among the 13 compounds obtained by SDSE. After statistical analysis of the data, both techniques enabled the same conclusion: (E)-beta-farnesene was the only compound which showed significant differences between the two flower development stages. These results suggest that HS-SPME-GC-MS can be used as a sensitive technique for the rapid screening and quality assessment of M. chamomilla.     

Calculation of Density for Mixtures of Carbon Dioxide with Nitrogen and Methane from the ISM Equation of State

In this paper the analytical equation of state (EoS) proposed by Ihm‐Song‐Mason was applied to calculate molar volume of mixtures of carbon dioxide with nitrogen and methane. The pair interaction potential has been used to evaluate the second virial coefficients and the ISM EoS parameters (i.e. α and b). The calculated values of the aforesaid quantities were applied to predict the molar volumes for mixtures of carbon dioxide with nitrogen and methane. Agreement with experiment was excellent for both mixtures.