Optimization of the n-hexane isomerization process using response surface methodology

Isomerization reactions on commercial zirconium sulfate catalyst are investigated in order to determine influence of hydrogen/feed ratio, space velocity and temperature on n-hexane conversion. Investigated range of inlet parameters includes values that are applied in the industrial practice of the isomerization process. Box–Behnken experimental design was carried out in order to optimize n-hexane isomerization process. Statistical analysis of experimental data was performed to obtain second order polynomial model and the optimum conditions were determined: hydrogen/feed ratio of 6, space velocity of 2 h⁻¹ and temperature of 170 °C. At optimum conditions conversion of n-hexane was 70 wt.%. In addition, temperature dependency of product composition was investigated at optimum values of hydrogen/feed ratio and space velocity. Obtained results show that methylpentanes greatly depend on temperature, unlike dimethylbutanes, in the studied range from 130 to 170 °C. Isomer that was produced in highest quantities was 2-methylpentane, while 3-methylpentane forms in somewhat smaller amounts. 2,2- and 2,3-dimethylbutanes, which contribute the most to the octane number value, are formed in relatively small quantities, amounting to less than 10 wt.% of the total amount of isomers formed.     

EFFECT OF NUCLEOTIDE SEQUENCE ON THE BINDING OF (–)–ANTI–DIBENZO– [a,l]PYRENE–11,12–DIOL 13,14–EPOXIDE TO SHORT OLIGODEOXYRIBONUCLEOTIDES

Abstract

Seven selfcomplementary decamer oligodeoxyribonucleotides were reacted with (–)–anti–(11R,12S)–dihydrodiol (13S,14R)–epoxide of dibenzo[a,l]pyrene (DB[a,l]PDE). The oligodeoxyribonucleotides were postlabeled with ³³P–ATP, digested to mononucleotides and the amount of adducts formed was determined by HPLC. We found that the nucleotide sequence affects the binding of DB[a,l]PDE to DNA. DB[a,l]PDE binds better to GC rich oligodeoxyribonucleotides than to AT rich oligodeoxyribonucleotides. The CGC sequence binds more DB[a,l]PDE than GGC, TGC, GAT or AGC sequences. The reactions were carried out on ice or at 37°C. There was no evidence of temperature effects on the amount of DB[a,l]PDE binding.     

Magnetic Nanosystem for Cancer Therapy Using Oncocalyxone A,an Antitomour Secondary Metabolite Isolated from a Brazilian Plant

This paper describes the investigation and development of a novel magnetic drug delivery nanosystem (labeled as MO-20) for cancer therapy. The drug employed was oncocalyxone A (onco A), which was isolated from Auxemma oncocalyx, an endemic Brazilian plant. It has a series of pharmacological properties: antioxidant, cytotoxic, analgesic, anti-inflammatory, antitumor and antiplatelet. Onco A was associated with magnetite nanoparticles in order to obtain magnetic properties. The components of MO-20 were characterized by XRD, FTIR, TGA, TEM and Magnetization curves. The MO-20 presented a size of about 30 nm and globular morphology. In addition, drug releasing experiments were performed, where it was observed the presence of the anomalous transport. The results found in this work showed the potential of onco A for future applications of the MO-20 as a new magnetic drug release nanosystem for cancer treatment.     

Stability of high internal phase emulsions with sole cationic surfactant and its tailoring morphology of porous polymers based on the emulsions

Stable w/o high internal phase emulsion (HIPE) using cetyltrimethylammonium bromide (CTAB) as the sole surfactant was prepared with long time further mixing of the emulsion after the addition of aqueous phase was completed, although it was generally considered the emulsion would be unstable according to Bancroft rule. The delta backscattering data of these emulsions showed that the further mixing enhanced the stability of the HIPE significantly, because a dram partial of monomers was initiated in the period of preparing the emulsion, which reduced the diffusion of CTAB from the oil phase to aqueous phase and increased the viscosity of the continuous phase. In addition, the morphology of polyHIPEs based on this type HIPEs was tailored. Increasing aqueous phase fraction resulted in the increase of pore volume which could be up to 24.0 ml/g. Increasing the polymerization temperature led to an increase in average void and interconnect diameter in the resulting porous materials. Additionally, the presence of additives, PEG and ethanol, in the aqueous phase was found to increase the average void diameter remarkably. The interconnect diameter of the materials could be controlled at constant pore volume by tuning PEG and ethanol concentration in the aqueous phase. It was suggested that coalescence was the dominant effect in determining the morphology of the polyHIPEs prepared in the presence of PEG, and Ostwald ripening was the major role in tailoring the morphology of the porous materials with ethanol.     

Long-Term Effects of Repetitive Mild Traumatic Injury on the Visual System in Wild-Type and TDP-43 Transgenic Mice

Little is known about the impairments and pathological changes in the visual system in mild brain trauma, especially repetitive mild traumatic brain injury (mTBI). The goal of this study was to examine and compare the effects of repeated head impacts on the neurodegeneration, axonal integrity, and glial activity in the optic tract (OT), as well as on neuronal preservation, glial responses, and synaptic organization in the lateral geniculate nucleus (LGN) and superior colliculus (SC), in wild-type mice and transgenic animals with overexpression of human TDP-43 mutant protein (TDP-43^G348C) at 6 months after repeated closed head traumas. Animals were also assessed in the Barnes maze (BM) task. Neurodegeneration, axonal injury, and gliosis were detected in the OT of the injured animals of both genotypes. In the traumatized mice, myelination of surviving axons was mostly preserved, and the expression of neurofilament light chain was unaffected. Repetitive mTBI did not induce changes in the LGN and the SC, nor did it affect the performance of the BM task in the traumatized wild-type and TDP-43 transgenic mice. Differences in neuropathological and behavioral assessments between the injured wild-type and TDP-43^G348C mice were not revealed. Results of the current study suggest that repetitive mTBI was associated with chronic damage and inflammation in the OT in wild-type and TDP-43^G348C mice, which were not accompanied with behavioral problems and were not affected by the TDP-43 genotype, while the LGN and the SC remained preserved in the used experimental conditions.     

Diabetes Mellitus and Its Implications in Aortic Stenosis Patients

Aortic stenosis (AS) and diabetes mellitus (DM) are both progressive diseases that if left untreated, result in significant morbidity and mortality. Several studies revealed that the prevalence of DM is substantially higher in patients with AS and, thus, the progression from mild to severe AS is greater in those patients with DM. DM and common comorbidities associated with both diseases, DM and AS, increase patient management complexity and make aortic valve replacement the only effective treatment. For that reason, a better understanding of the pathogenesis underlying both these diseases and the relationships between them is necessary to design more appropriate preventive and therapeutic approaches. In this review, we provided an overview of the main aspects of the relationship between AS and DM, including common comorbidities and risk factors. We also discuss the established treatments/therapies in patients with AS and DM.