Production of Ethyl Esters by Direct Transesterification of Microalga Biomass Using Propane as Pressurized Fluid

Applied Biochemistry and Biotechnology - This work aimed to produce ethyl esters from Chlorella vulgaris microalgae biomass, using an immobilized enzymatic catalyst associated with pressurized...     

Microwave magneto-absorption in Bi and the NENP model

A new type of quantum oscillations of the microwave magneto-absorption in bismuth is presented. As an application a support of the non-ellipsoidal non-parabolic (NENP) Cohen model is given.     

Statistical comparison of reverberation times measured by the integrated impulse response and interrupted noise methods, computationally simulated with ODEON software, and calculated by Sabine, Eyring and Arau-Puchades’ formulas

This paper evaluates several procedures to determine the reverberation time, RT, in a classroom. These procedures are: (1) measurement by the integrated impulse response method, (2) measurement by the interrupted noise method, (3) computer simulation using ODEON Version 9.0 software, and (4) calculations using the Sabine, Eyring, and Arau-Puchades formulas. The resulting data are analyzed statistically to verify their similarity. No statistical difference was found between the values obtained by the two measuring methods. The computer simulation produced accurate data. The best formula for calculating RT in the classroom in question is Eyring’s formula.     

Modeling of molecular packing and conformation in oligofluorenes

We describe the application of molecular modeling to study problems related to the packing and conformation of oligofluorene molecules in the solid state. First of all, we describe an improved force field for oligofluorenes. The model is based on the MM3 force field for the intramolecular degrees of freedom, but it relies on ab initio calculations for the torsion potential between two monomers and the electrostatic interactions. We also report ab initio calculations of the interaction potentials between fluorene and fluorenone units. The force field has been tested on the crystal structures of a fluorene monomer, a dimer, and a pentamer containing a fluorenone at the center. It has then been employed to study conformational defects of the chains, both in vacuo and in the bulk. We find that certain modes of inversion from right-handed to left-handed helices are also possible within the constraining environment of the crystals. The effect of the presence of two different types of side chains has been also addressed. Finally, the possibility of having two fluorene units parallel and close to each other has been investigated as a model of a ground-state precursor of an excimer. Our simulations show that this configuration is sterically and energetically unfavorable so that formation of an excimer following optical excitation appears to be unlikely.     

Effect of two-step functionalization of Ti by chemical processes on protein adsorption

Titanium and its alloys are widely used for orthopedic and dental implants because of their superior mechanical properties, low modulus, excellent corrosion resistance and good biocompatibility. However, it takes several months for titanium implants and bone tissue to reach integration. Hence, there is growing interest in shortening the process of osseointegration and thereby reducing surgical restrictions. Various surface modifications have been applied to form a bioactive titanium oxide layer on the metal surface, which is known to accelerate osseointegration.The present work shows that titanium dioxide (TiO₂) layers formed on titanium substrates by etching in a solution of sodium hydroxide (NaOH) or hydrogen peroxide/phosphoric acid (H₃PO₄/H₂O₂, with a volume ratio of 1:1) are highly suitable pre-treatments for apatite-like coating deposition. Using a two-step procedure (etching in an alkaline or acidic solution followed by soaking in Hanks’ medium), biomimetic calcium phosphate coatings were deposited on porous TiO₂ layers. The combined effects of surface topography and chemistry on the formation of the calcium phosphate layer are presented. The topography of the TiO₂ layers was characterized using HR-SEM and AFM techniques. The nucleation and growth of calcium phosphate (Ca-P) coatings deposited on TiO₂ porous layers from Hanks’ solution was investigated using HR-SEM microscopy. AES, XPS and FTIR surface analytical techniques were used to characterize the titanium dioxide layers before and after deposition of the calcium phosphate coatings, as well as after the process of protein adsorption. To evaluate the potential use of such materials for biomedical applications, the adsorption of serum albumin, the most abundant protein in the blood, was studied on such surfaces.     

Microwave magneto-absorption resonances in metals

Microwave magneto-absorption resonances are predicted in metals when, in the frame of a semiclassical theory, scatterers are considered. Experimental evidence is found in bismuth at the frequency $\text{? = 22.5}\text{GHz}$ and the temperature T = 1.3 K.