Novel hybrid process for the conversion of microcrystalline cellulose to value-added chemicals: part 1: process optimization

In this paper, a novel hybrid process for the treatment of microcrystalline cellulose (MCC) under hot-compressed water was investigated by applying constant direct current on the reaction medium. Constant current range from 1A to 2A was applied through a cylindrical anode made of titanium to the reactor wall. Reactions were conducted using a specially designed batch reactor (450 mL) made of SUS 316 stainless steel for 30–120 min of reaction time at temperature range of 170–230 °C. As a proton donor H₂SO₄ was used at concentrations of 1–50 mM. Main hydrolysis products of MCC degradation in HCW were detected as glucose, fructose, levulinic acid, 5-HMF, and furfural. For the quantification of these products, High Performance Liquid Chromatography (HPLC) and Gas Chromatography with Mass Spectroscopy (GC–MS) were used. A ½ fractional factorial design with 2-level of four factors; reaction time, temperature, H₂SO₄ concentration and applied current with 3 center points were built and responses were statistically analyzed. Response surface methodology was used for process optimization and it was found that introduction of 1A current at 200 °C to the reaction medium increased Total Organic Carbon (TOC) and cellulose conversions to 62 and 81 %, respectively. Moreover, application of current diminished the necessary reaction temperature and time to obtain high TOC and cellulose conversion values and hence decreased the energy required for cellulose hydrolysis to value added chemicals. Applied current had diverse effect on levulinic acid concentration (29.9 %) in the liquid product (230 °C, 120 min., 2 A, 50 mM H₂SO₄).     

Preparation of novel pyrrol-2-one derivatives via an effective synthesis of new oxazole scaffold

A convenient procedure for the preparation of oxazole and pyrrole derivatives is described. 2-Amino-1,3-oxazol-2-ones 3a,b were first synthesized from the cyclocondensation reactions of cyanamide (2) with 4-ethoxycarbonyl-5-aryl-2,3-furandione 1a,b, and then new pyrrol-2-ones 5 were synthesized from the reaction of the compounds 3 with various aromatic amines 4.     

Stacking effects on local structure in RNA: changes in the structure of tandem GA pairs when flanking GC pairs are replaced by isoG-isoC pairs

The Watson-Crick-like isoG-isoC (iGiC) pair, with the amino and carbonyl groups transposed relative to the Watson-Crick GC pair, provides an expanded alphabet for understanding interactions that shape nucleic acid structure. Here, thermodynamic stabilities of tandem GA pairs flanked by iGiC pairs are reported along with the NMR structures of the RNA self-complementary duplexes (GCiGGAiCGCA)2 and (GGiCGAiGCCA)2. A sheared GA pairing forms in (GCiGGAiCGCA)2, and an imino GA pairing forms in (GGiCGAiGCCA)2. The structures contrast with the formation of tandem imino and sheared GA pairs flanked by GC pairs in the RNA self-complementary duplexes (GCGGACGC)2 and (GGCGAGCC)2, respectively. In both iGiC duplexes, Watson-Crick-like hydrogen bonds are formed between iG and iC, and iGiC substitutions result in less favorable loop stability. The results provide benchmarks for testing computations of molecular interactions that shape RNA three-dimensional structure.     

Higher order approximate periodic solutions for nonlinear oscillators with the Hamiltonian approach

In this work, the Hamiltonian approach is applied to obtain the natural frequency of the Duffing oscillator, the nonlinear oscillator with discontinuity and the quintic nonlinear oscillator. The Hamiltonian approach is then extended to the second and third orders to find more precise results. The accuracy of the results obtained is examined through time histories and error analyses for different values for the initial conditions. Excellent agreement of the approximate frequencies and the exact solution is demonstrated. It is shown that this method is powerful and accurate for solving nonlinear conservative oscillatory systems.     

Density functional theory study on the identification of 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol

This study deals with the identification of a title compound, 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol by means of quantum chemical calculations. The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments, thermodynamic properties, charge analyses, nuclear magnetic resonance (NMR) chemical shifts and ultraviolet-visible (UV-vis) spectra of the title molecule in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311++G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra of the title compound were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the obtained optimized geometric parameters (bond lengths, bond angles and bond dihedrals) and vibrational frequencies were observed to be in good agreement with the available experimental results. Moreover, the calculations of the electronic spectra, (13)C and (1)H chemical shifts were compared with the experimental ones. Furthermore, we not only simulated the frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition states and energy band gaps, as well. It was found that charge analyses supported the evidences of MEP. Infrared intensities and Raman activities were also reported.     

A new green technology: hydrothermal electrolysis for the treatment of biodiesel wastewater

Recently, biodiesel has become more attractive as an alternative diesel fuel because it is renewable, biodegradable, non-toxic, and environmentally friendly. In this study, we have developed a new green process called ??hydrothermal electrolysis??, by which industrial wastewater can be converted to more value-added chemicals under high-temperature and high-pressure aqueous conditions. We prepared model biodiesel wastewater and carried out hydrothermal electrolysis experiments by using both a continuous flow reactor and a batch autoclave. Current efficiencies and the effects of reaction time and reaction temperature on the decomposition of biodiesel wastewater and removal of total organic carbon (TOC) were investigated under various operating conditions. It was found that conversions of both TOC and glycerol inside the model biodiesel wastewater increased with increasing applied current. With the autoclave, the maximum glycerol conversion was recorded as 83% by applying 1 A current at 250 °C, whereas with the flow reactor, 75% of glycerol was converted into gas and liquid products under the effect of 1 A current for 60 min at a reaction temperature of 280 °C. In the case of TOC removal from the liquid product solution, under identical conditions, it was found that 23 and 15.9% TOC conversions were achieved by the batch and continuous flow reactors, respectively.     

WEFTA interlaboratory comparison on total lipid determination in fishery products using the Smedes method

Lipid determination by the Smedes method was tested in an interlaboratory trial performed by nine laboratories from seven countries belonging to the West European Fish Technologists Association Analytical Methods Working Group. Five samples of fish and fishery products with different lipid contents, including two blind duplicates, were distributed among the participants. All laboratories applied a slightly modified Smedes method, which included extraction of lipids by cyclohexane and isopropanol, transfer of lipids to the cyclohexane phase by addition of water, phase separation by centrifugation, and gravimetric lipid determination. The results indicate that the RSD for reproducibility (RSD(R)) was between 4.11 and 6.31% for samples with moderate (7%) and high (14%) lipid content, depending on the sample. Larger SDs among the laboratories were obtained for a cod sample with low lipid content of 0.5%. The method is judged to be suitable as a routine method for lipid determination in fish and fishery products.     

Effect of finishing methods on surface roughness and color stability in all-ceramic systems

The objectives of the study were to evaluate the effect of the finishing methods on the surface roughness, and to investigate changes in CIE L*a*b* color coordinates of all-ceramic systems after different finishing methods and accelerated aging. Sixty specimens were prepared, 20 specimens each for Vitadur-N, IPS Empress II, and Cerec Vita Block Mark II. The surface roughness (Ra) following treatment with the different finishing methods was measured using a profilometer. Surface examinations in all groups were made by using a scanning electronic microscope. CIE L*a*b* values of the specimens were determined. After all specimens were subjected to accelerated aging, color measurements were repeated, and the total color differences (ΔE) were calculated. Data were analyzed statistically. Significant differences in surface roughness among all-ceramics were found (P < 0.05). No significant differences were found between the surface roughness of the glazed and polished all-ceramics (P > 0.05). After accelerated aging, all groups had acceptable color changes (ΔE < 2).