936 resultados para Thermochemical pretreatment


Relevância:

10.00% 10.00%

Publicador:

Resumo:

AgSIE was used for the direct analysis of folic acid (FA), with a detection limit and lower level of quantitation of 6.8 x10-10 mol L-1 and 2.3 x 10 8 mol L-1. The analysis in fresh and processed fruits was done without any sample pretreatment. In strawberry and acerola juices, FA concentration level values were below the method detection limit. FA was detectable in peach (77.7 0.4 mg L-1 and 64.4 0.5 mgL-1), Persian lime (45.4 0.7 mg L-1), pineapple Hawaii (66.2 0.4 mgL-1), pear pineapple (35.3 0.6 mgL-1), cashew (54.4 0.5 mgL-1) , passion fruit (73.2 0.3 mgL-1), and apple (84.4 0.5 mg L-1 ).

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The oxidation of ethanol (EtOH) at Pt(111) electrodes is dominated by the 4e path leading to acetic acid. The inclusion of surface defects such as those present on stepped surfaces leads to an increase of the reactivity towards the most desirable 12e path leading to CO2 as final product. This path is also favored when the methyl group is more oxidized, as in the case of ethylene glycol (EG) that spontaneously decomposes to CO on Pt(111) electrodes, thus showing a more effective breaking of the C-C bond. Some trends in reactivity can be envisaged when other derivative molecules are compared at well-ordered electrodes. This strategy was used in the past, but the improvement in the electrode pretreatment and the overall information available on the subject suggest that relevant information is still missing.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Hydrogen is known as a clean energy resource. The biological production of hydrogen has been attracting attention as an environmentally friendly processs that does not consume fossil fuels. Cellulosic plant and waste materials are potential resources for fermentative hydrogen production. Cellulose is a linear biopolymer of glucose molecules, connected by β-1,4-glycosidic bonds. Enzymatic hydrolysis of cellulose requires the presence of cellulase. The present study aimed to investigate the efficiency of acid pretreatment on ruminal fluid in order to enrich H2 producing bacteria consortia to enhance biohydrogen rate and substrate removal efficiency. In this study, fermentative hydrogen producers were enriched on cellulose (2g/L) in a modificated Del Nery medium (DNM) at 37ºC and initial pH 7.0 using rumen fluid (10% v/v) as inoculum. To increase the hydrogen production it was added cellulose (10mL) to the medium. The gas products (mainly H2 and CO2) was analyzed by gas chromatography (Shimadzu GC 2010) using a thermal conductivity detector. The volatile fatty acids and ethanol were also detected by GC using a flame ionization detector. Cellulose degradation was quantified by using the phenolsulfuric acid method. Analysis showed that the biogas produced from the anaerobic fermentation contained only hydrogen and carbon dioxide, without detectable methane after acid pretreatment test. On DNM the hydrogen production started with 4 h (5,3 x 105 mmol H2/L) of incubation, and the maximum H2 concentration was observed with 34 h (7,1 x 106 mmol H2/L) of incubation. During the process, it was observed a predominance of acetic acid and butyric acid as well as a low production of acetone, ethanol and nbutanol in all experimental phases. Butyrate accounted for more than 77% of total. As a result of the accumulation of volatile fatty acids (VFAs), the pH value in anaerobic digestion system was reduced to 4,0. On microscopy analyses there were observed rods with endospores. The batch anaerobic fermentation assays performed on anaerobic mixed inoculum from rumen fluid demonstrated the feasibility of H2 generation utilizing cellulose as substrate. Based on the results, it can be concluded that the acid treatment was efficient to inhibit the methanogenic archaea cells present in rumen fluid. The rumen fluid cells present a potential route in converting renewable biomass such as cellulose into hydrogen energy.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Orthodontic therapy is known to be associated with the development of gingival recession. Several factors may be involved in the causal chain of this outcome, including anatomical and behavioral aspects. Among the anatomical aspects, the dimensions of the mandibular symphysis could play a predisposing role. This study evaluated the relationship between the mandibular symphysis dimensions prior to orthodontic therapy and the development of gingival recessions on the lower incisors and cuspids. Records from 189 orthodontically treated adolescents were evaluated, including radiographs, casts and intra-oral photographs. Symphysis dimensions were assessed by cephalograms. Gingival margin alterations were determined in photographs and cast models. Association between gingival margin alterations and symphysis dimensions was tested by chi-square (α=0.05). Occurrence of gingival recession increased after orthodontic therapy. No association was observed on average of symphysis dimensions and the occurrence of gingival recessions. It may be concluded that pretreatment symphysis dimensions may not be used as predictors of gingival recession after orthodontic therapy.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Patients with Class II division 2 malocclusion and mandibular retrusion have limited treatment options after the growth peak, such as surgical-orthodontic treatment or mandibular advancement devices. Among bite-jumping devices, the Herbst appliance allows greater increase of mandibular growth since it does not require patient compliance and allows continuous use. This case report presents the treatment of a Class II division 2 malocclusion in a patient after growth peak, performed in two stages. The first stage included the upper incisors proclination and overjet increase with multibracket appliance to benefit next stage. The second stage involved mandibular advancement using Herbst appliance aiming to correct the Class II molar relationship. The treatment resulted in a stable occlusion with periodontal health, normal functions and facial aesthetics improvement. Dental and skeletal changes arising from treatment could be assessed by cephalometric analysis and superimposition of pretreatment and post-treatment cephalometric tracings. Antero-posterior discrepancy was corrected by means of dental movement as well as by mandibular growth increment stimulated by the Herbst appliance.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)