Kinetic modeling of benzoic acid esterification using functionalized silica gel

In our study, we synthesized two types of solid acid catalysts. Silica gel with a particle size of 0.063–0.2?mm was silanized first at reflux (S1) and second at room temperature (S3) using (3-mecaptopropyl)trimethoxysilane in toluene, and further oxidized with H₂O₂, and methanesulfonic acid. Characterization of the synthesized catalysts was performed using adsorption/desorption of nitrogen (BET), Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. Both catalysts were used in esterification reactions of benzoic acid with methanol. All reactions were performed in a batch reactor at temperatures, ??=?55, 60, and 64.5°C, stirrer speed, f_s?=?400?min^?1, and catalyst loading, m?=?5, 10, and 15?g. The concentration of produced methylbenzoate was determined by HPLC. The study was supplemented with a kinetic study of the reaction. First-order kinetics was confirmed for this esterification reaction. Using catalyst S1, higher conversion was reached, while catalyst S3 is much more suitable for reuse.     

Answer to the remarks on superconductivity in PdH

In this paper, the effect of heating rate on the microwave sintered 90W–7Ni–3Fe heavy alloys was investigated, with the heating rate in the range from 10 to 112 °C/min. When the alloys were sintered at the heating rate from 20 to 105 °C/min, they exhibit excellent properties with the relative density over 99%, tensile strength between 850 and 922 MPa and elongation around 20%. It has been shown that a faster heating rate results in smaller W grain size and larger W–W contiguity. The heating rate of 80 °C/min has the best combination of the microstructure and mechanical performance. Sintering under an optimized condition leads to the enhanced mechanical properties of 1020 MPa in tensile strength and 21% in elongation.     

Influence of Ag on the Composition and Electromagnetic Properties of Low-Temperature Cofired Hexaferrites

We have studied the compatibility of Ag and (Co,Cu)Z-hexaferrite with the composition Ba₃Co_1.4Cu_0.6Fe₂₄O₄₁ (Z). In order to do this, the (Co,Cu)Z-hexaferrite was cofired with various amounts of Ag at 900°C. The degradation of the (Co,Cu)Z-hexaferrite to Y- and U-hexaferrite occurred during the cofiring and was confirmed by X-ray diffraction as well as by thermomagnetic measurements. The permeability and permittivity of the cofired ceramics were measured in the range 1 MHz to 10 GHz. For the (Co,Cu)Z-hexaferrite, both these properties were significantly influenced by the Ag when the amount of Ag exceeded a minimum of 4.5 wt%. The influence of the Ag and the degradation of the (Co,Cu)Z-hexaferrite on the permeability were evaluated using the Bruggeman effective media theory.     

The mechanism of the low-temperature formation of barium hexaferrite

We have investigated the formation of barium hexaferrite via the coprecipitation method. Fine precursor powders were obtained with coprecipitation from water and ethanol solutions of various reagent salts. The coprecipitates were calcined at 300–800 °C for 0–50 h. The samples were characterized with X-ray powder diffraction, thermal analysis, electron microscopy and magnetometry. The formation of barium hexaferrite was a combination of two competing mechanisms and was not influenced by the reagent salts or the solvent. The formation temperature of the barium hexaferrite was reduced to 500 °C by optimizing the coprecipitation conditions.     

Interaction between Microalgae P. tricornutum and Bacteria Thalassospira sp. for Removal of Bisphenols from Conditioned Media

We studied the efficiency of three culture series of the microalgae Phaeodactylum tricornutum (P. tricornutum) and bacteria Thalassospira sp. (axenic microalgae, bacterial culture and co-culture of the two) in removing bisphenols (BPs) from their growth medium. Bacteria were identified by 16S ribosomal RNA polymerase chain reaction (16S rRNA PCR). The microorganism growth rate was determined by flow cytometry. Cultures and isolates of their small cellular particles (SCPs) were imaged by scanning electron microscopy (SEM) and cryogenic transmission electron microscopy (Cryo-TEM). BPs were analyzed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). Our results indicate that some organisms may have the ability to remove a specific pollutant with high efficiency. P. tricornutum in axenic culture and in mixed culture removed almost all (more than 99%) of BPC2. Notable differences in the removal of 8 out of 18 BPs between the axenic, mixed and bacterial cultures were found. The overall removals of BPs in axenic P. tricornutum, mixed and bacterial cultures were 11%, 18% and 10%, respectively. Finding the respective organisms and creating microbe societies seems to be key for the improvement of wastewater treatment. As a possible mediating factor, numerous small cellular particles from all three cultures were detected by electron microscopy. Further research on the mechanisms of interspecies communication is needed to advance the understanding of microbial communities at the nano-level.     

Interferon Beta-1a versus Combined Interferon Beta-1a and Oligodendrocyte-Specific FGFR1 Deletion in Experimental Autoimmune Encephalomyelitis

Recombinant beta interferons-1 (IFNβ-1) are used as first line therapies in patients with relapsing multiple sclerosis (MS), a chronic inflammatory and neurodegenerative disease of the CNS. IFNβ-1a/b has moderate effects on the prevention of relapses and slowing of disease progression. Fibroblast growth factors (FGFs) and FGF receptors (FGFRs) are known to play a key role in the pathology of MS and its model EAE. To investigate the effects of short-term treatment with s.c. IFNβ-1a versus the combined application of s.c. IFNβ-1a and oligodendrocyte-specific deletion of FGFR1 (Fgfr1^ind−/− mice) in MOG_35-55-induced EAE. IFNβ-1a (30 mg/kg) was applied s.c. from days 0–7 p.i. of EAE in controls and Fgfr1^ind−/− mice. FGFR signaling proteins associated with inflammation/degeneration in MS/EAE were analyzed by western blot in the spinal cord. Further, FGFR1 in Oli-neu oligodendrocytes were inhibited by PD166866 and treated with IFNβ-1a (400 ng/mL). Application of IFNβ-1a over 8 days resulted in less symptoms only at the peak of disease (days 9–11) compared to controls. Application of IFNβ-1a in Fgfr1^ind−/− mice resulted in less symptoms primarily in the chronic phase of EAE. Fgfr1^ind−/− mice treated with IFNβ-1a showed increased expression of pERK and BDNF. In Oli-neu oligodendrocytes, treatment with PD166866 and IFNβ-1a also showed an increased expression of pERK and BDNF/TrkB. These data suggest that the beneficial effects in the chronic phase of EAE and on signaling molecules associated with ERK and BDNF expression are caused by the modulation of FGFR1 and not by interferon beta-1a. FGFR may be a potential target for therapy in MS.     

Lipid class and fatty acid composition of the boreal soft coral Gersemia rubiformis

Total lipid, phospholipid, and FA composition and distribution of FA between polar lipids (PL) and neutral lipids (NL) were investigated in the boreal soft coral Gersemia rubiformis from the Bering Sea. The total lipids were mostly hydrocarbons and waxes (33.7%) and PL (33.1%). The content of monoalkyldiacylglycerols (9.7%) exceeded the content of TAG (6.7%). PC and PE constituted 31.4% and 25.6% of total phospholipids, respectively. Principal FA were 16∶0, 16∶1n−7, 18∶0, 18∶1n−9, 18∶1n−7, 20∶1n−7, 20∶4n−6, 20∶4n−3, 20∶5n−3 22∶5n−3, 22∶6n−3, 24∶5n−6, and 24∶6n−3. Most n−6 PUFA (52% of total FA) were associated with the PL fraction; this was especially true for arachidonic and tetracosapentaenoic acids. The NL were enriched with mono-, di-, trienoic, and n−3 PUFA. The variation in EPA levels in both NL and PL suggests an origin of this acid from lipids of diatoms consumed by the corals.     

Cubic Spline Collocation for Volterra Integral Equations

In the standard step-by-step cubic spline collocation method for Volterra integral equations an initial condition is replaced by a not-a-knot boundary condition at the other end of the interval. Such a method is stable in the same region of collocation parameter as in the step-by-step implementation with linear splines. The results about stability and convergence are based on the uniform boundedness of corresponding cubic spline interpolation projections. The numerical tests given at the end completely support the theoretical analysis. Received: January 15, 2002; revised July 27, 2002 Published online: December 19, 2002