RESUMO: Dois tratamentos químicos, cinco enzimáticos (pectinase, lipase, hemicelulase, hemicelulose-celulase ou lipase-pectinase) e um microbiológico (Bacillus subtilis) foram avaliados para obter o cloridrato de glucosamina (Gluc-HCl) da quitina obtida a partir de exoesqueletos de caranguejo (Callinectes. Bellicosus). Os dois tratamentos químicos foram nomeados como método A (hidrólise de HCl para 75 min a 90 °C) e método B (hidrólise de HCl para 20 min e 14 h de repouso). A Glucosamina e, em alguns casos, N-acetil-D-glucosamina foram identificados e quantificados por HPLC. Os tratamentos em que as melhores concentrações de Glucosamina-HCl foram obtidas, em ordem decrescente: lipase (94,4 mg/g), microbiológica (45,7 mg/g), lipase-pectinase (22,9 mg/g), hemicelulase-celulase (20,9 mg/g), hemicelulase (15,3 mg/g), pectinase (10,7mg/g), Quïmica A (7,3 mg/g) e Quïmica B (7,3 mg/g). Em termos de produtividade, os melhores tratamentos em ordem decrescente foram: pectinase (94%), microbiológica (94%), hemicelulase (92%), lipase (91%), química B (88%), lipase-pectinase (88%), hemicelulase- celulase (86%) e produto químico A (28,5%). Os dois melhores tratamentos foram lipase e microbiológicos, propostos como método viável para obtenção de Gluc-HCl a partir de exoesqueletos de caranguejo; cumprem procedimentos ecologicamente corretos e podem agregar valor à cadeia produtiva do caranguejo.

ABSTRACT: Two chemical treatments, five enzymatic (pectinase, lipase, hemicellulase, hemicellulose-cellulase or lipase-pectinase) and one microbiological (Bacillus subtilis) treatment were evaluated to obtain glucosamine hydrochloride (Gluc-HCl) from the chitin obtained from crab (Callinectes bellicosus) exoskeletons. Chemical treatments were referred as Method A (HCl hydrolysis during 75 min at 90°C) and Method B (HCl hydrolysis during 20 min and 14 h of rest). Glucosamine and, in some cases, N-acetyl-D-glucosamine were identified and quantified by HPLC. Treatments with the greater concentrations of Gluc-HCl in descending order were: lipase (94.4 mg/g), microbiological (45.7 mg/g), lipase-pectinase (22.9 mg/g), hemicellulase-cellulase (20.9 mg/g), hemicellulase (15.3 mg/g), pectinase (10.7 mg/g), Chemical A (7.3mg/g) and Chemical B (7.3mg/g). In terms of yield, the best treatments in descending order were: pectinase (94%), microbiological (94%), hemicellulase (92%), lipase (91%), Chemical B (88%), lipase-pectinase (88%), hemicellulase-cellulase (86%) and Chemical A (28.5%). The two most profound treatments were lipase and microbiological, so they are proposed as part of a viable method to produce Gluc-HCl from crab exoskeletons; they are ecofriendly procedures and could add value to the crab´s productive chain.

Abstract In education, decades have been spent investigating what kind of beliefs and attitudes students may have in relation to learning. The relevance of these lies on the implications that it brings concerning students' alternative conceptions. This research focuses on the inclusion of Peer Instruction (PI) as a methodology to address the alternative conceptions in Einstein's special relativity. PI was selected since there is evidence that it has an impact on the academic performance of the students, however, concerning the topic of relativity, it has not been previously proposed. Alternative Conception Einstein's Special Relativity Test (ACESRT) is proposed to determine students' alternative conceptions. The sample for this study consisted of 25 high school students from Ecuador. In none of this level, students study Einstein's special relativity, nevertheless, in the current year a special course with senior students (picked randomly) was open in which the topic was considered in their academic curriculum. In the first lecture, the students filled a survey to get a notion of their beliefs and attitudes. Then a pre-test (ACESRT) take place, with a view getting information of alternative conceptions that students may have. Later, lectures following PI were given. At the end, to measure PI impact on students' attitudes, beliefs and alternative conceptions the students filled again a survey, followed by post-test (ACESRT). The results were statistically analyzed, and they reveal that PI has a strong impact on students' beliefs and attitudes. Furthermore, the methodology has the potential to address the alternative conception in concepts related to the topic Einstein's special relativity.

El objetivo de este estudio consistió en medir la intensidad de las vibraciones (en términos de aceleración) originados por máquinas en una empresa del sector agroindustrial, con la finalidad de ser comparados con los límites de exposición permisibles sugeridos en la norma ISO 2631-1 para establecer el riesgo al que están expuestos los colaboradores. El equipo utilizado fue un monitor de vibraciones VI- 400 Pro Quest Technologies, compuesto por un acelerómetro triaxial de pies - asiento o PCB 356B40. La investigación se efectuó en el pasillo donde están ubicadas dos centrífugas por medio de las cuales se recibe la masa cocida proveniente del tacho y se separa el cristal de la miel y en tres (3) grúas de hilo a través de las cuales se realiza el descargue de los trenes cañeros. Los hallazgos demostraron que existen diferencias en las vibraciones generadas por las grúas y en el pasillo donde están ubicadas las centrífugas, las intensidades de las vibraciones mostraron el siguiente comportamiento: 45,5% de las aceleraciones obtenidas por medio de mediciones en campo oscilan en un rango entre 8,0 m/s² y 1,15 m/s², representando un riesgo elevado para la salud de los trabajadores, el 54,5% de las mediciones superaron la intensidad de aceleración de 1,15 m/ s². Se recomienda realizar estudios posteriores que permitan la reducción del riesgo por exposición y el adecuado mantenimiento de las máquinas.

The objective of this study was to measure the intensity of vibration (in terms of acceleration) caused by different machines in an agrobusiness company and compare them to the permissible exposure limits listed in the ISO 2631 Standard, and define any risks to which employees may be exposed. The equipment used was a 400 Pro Quest VI Technologies vibration monitor, which consists of a triaxial foot to seat accelerometer or PCB 356B40, which meets international standards ISO 2631-1, ISO 5349-2001, ANSI S3.34, ACGIH WBV 2004. The measurements were conducted in a hall where two centrifuges are located, through which the cooked mass sugarcane is run in order to separate honey from glass, and in three thread (3) cranes used to unload sugarcane trains. Results showed differences in vibration levels generated by the cranes and the halls where the centrifuges are located. Vibration intensity was as follows: 45.5% of the accelerations obtained through measurements varied from 8.0 m/s² to 1.15 m/s², representing a high health risk for workers; 54.5% of the measurements exceeded an acceleration intensity of 1.15 m/s². Recommendations include reduction of exposure levels and better machine maintenance.