Application of fentonś reaction to steam explosion prehydrolysates from poplar biomass

The application of Fenton’s reaction to enhance the fermentability of prehydrolysates obtained from steam explosion pretreatment of poplar biomass was studied. Reaction conditions of temperature and H₂O₂ and Fe(II) concentrations were studied. The fermentability of prehydrolysate treated by Fenton’s reaction was tested by using different inoculum sizes of thermotolerant strain Kluyveromyces marxianus CECT 10875. The highest percentages of toxic compound degradation (ranging from 71 to 93% removal) were obtained at the highest H₂O₂ concentration tested (50 mM). However, a negative effect on fermentability was observed at this H₂O₂ concentration at the lower inoculum loading. An increase in inoculum size to 0.6 g/L resulted in an enhanced ethanol fermentation yield of 95% relative to control.     

Total synthesis and biological evaluation of tamandarin B analogues

Tamandarins A and B are a class of marine natural cyclodepsipeptides with structures and biological activities closely related to those of the didemnins. The easier synthetic access to tamandarins accelerates the preparation of new macrocyclic derivatives of this family of antitumor, antiviral, and immunosuppressive compounds. The optimization of the previously reported synthetic route to tamandarins by changing the macrolactamization site from Nst1 and Thr6 to Pro4 and N,O-Me2Tyr5 residues led to a significant improvement in the reaction yield. Using this new synthetic approach, four new macrocyclic analogues of tamandarin B were prepared and evaluated for anticancer activity. These results provide further insight into the structure-activity relationship of the tamandarins and didemnins.     

Relación entre el parámetro flecha-luz y la carga crítica de pandeo lateral para arcos parabólicos biempotrados bajo diferentes hipótesis de cálculo

Curved graphs that relate the f/L ratio and the λ = qL³/EI_y parameter for clamped arches with the different calculation hypothesis are going to be proposed in this article.It has been necessary to determine the real critical lateral strength of a series of clamped arches considering different calculation hypothesis respect to geometrical linearity and a steel material characteristic.The elastic-plastic material hypothesis with non geometrical linearity considers the existence of residual stresses and initial lateral deflection.     

Reactions of methyl 3-hydroxythiophene-2-carboxylate. Part 4. Synthesis of methyl 5-azolyl-3-hydroxythiophene-2-carboxylates

The indirect introduction of an azolyl group in position 5 of compound 1 by an easy two-step procedure taking place at room temperature is described. A similar procedure yields the 4-chloro derivatives of these 5-azolyl compounds. The same method is applied for the introduction of a 5-azido group and from the 5-azido compounds, 5-v-triazolyl derivatives are obtained by a known method.     

Interfacial interaction between dextran sulfate and lipid monolayers: an electrochemical study

The interaction between dextran sulfate (DS) with zwitterionic dipalmitoylphosphatidylcholine (DPPC) and negatively charged dipalmitoylphosphatidic acid monolayers at different surface pressures at air-liquid and liquid-liquid interfaces was studied using Langmuir-Blodgett (LB) and electrochemical techniques. The negatively charged DS can bind to phospholipids via calcium ions. To investigate the mechanism of the adsorption of DS on lipid monolayers, compression isotherms (pi-A) and capacitance-potential curves were measured, and a theoretical model was developed to interpret the capacitance data. The compression of lipid monolayers in the presence of DS led to a more condensed hybrid layer, removing the LE-LC phase transition of DPPC. Lower surface pressures improved the binding of DS on the lipid monolayers via calcium bridges due to the electrostatic attraction. Alternating current voltammetry and cyclic voltammetry were used to monitor the transfer of a cationic beta-blocker (metoprolol) across lipid monolayers in the absence and presence of the polyelectrolyte and to compare with the transfer of the standard probe, tetraethylammonium cation. Results showed a strong dependence on (i) the surface pressure, (ii) the applied potential, and, (iii) in the case of the hybrid layer, the charge of the phospholipid headgroup. Finally, results were also confirmed by attenuated total reflection Fourier transform infrared spectroscopy, performed after transferring lipid multilayers onto a solid substrate by the LB method.     

Optoelectronic multiplexer for digital data processing based on lipid crystal pixels and optical fiber elements

In this work, we present an optoelectronic digital multiplexer 4:1 based on a multipixel nematic liquid crystal cell. This device uses two optical control signals to select one among four possible optical data inputs. These data signals are generated by four red LEDs, which are guided through plastic optical fiber towards liquid crystal pixels. For our purpose, only four pixels of the cell will be used to modulate the optical signal across them. Each pixel will be addressed by a square waveform coming from the conditioning circuit managed by a microcontroller system. The electronic control allows the multiplexer to work as as simple two input logical gates such as AND, NAND, OR, NOR, XOR and XNOR. The operation time of the device is limited by the response time of LC cell that is in the millisecond range.     

Matrix isolation FT-IR, FT-Raman spectroscopy, conformational ab initio calculations, and vibrational frequencies of meso and racemic-2,4-pentanediol

The infrared spectra of meso-2,4-pentanediol and racemic-2,4-pentanediol were measured in an argon matrix at 20 K. The Raman spectra of the pure liquids (meso and racemic) were measured at room temperature. The spectra were obtained using a Fourier transform spectrophotometer and a cryostat for the low temperature matrix. The meso and racemic forms of the diol were separated by means of a spinning band distillation column. The energies of nine possible conformers of the meso form and nine conformers of the racemic form were calculated. Extensive ab initio calculations using B3LYP, MP2 and HF methods with several basis sets consistently gave the lowest energy for the TT conformer of the meso form and the G⁻T (=TG⁻) conformer of the racemic form. Ab initio calculations at the B3LYP/6-31G** level were performed for the lowest energy conformer of meso and racemic pentanediol to obtain the equilibrium geometry, vibrational frequencies, and infrared and Raman intensities. Calculated and experimental frequencies were compared to make vibrational assignments.