Optimization of enzymatic hydrolysis of cassava to obtain fermentable sugars     

Renata M. Collares  Luiza V. S. Miklasevicius  Mariana M. Bassaco  Nina P. G. Salau  Marcio A. Mazutti  Dilson A. Bisognin  Lisiane M. Terra 《Journal of Zhejiang University. Science. B》2012,13(7):579-586

This work evaluates the enzymatic hydrolysis of starch from cassava using pectinase, α-amylase, and amyloglucosidase. A central composite rotational design (CCRD) was carried out to evaluate the effects of amyloglucosidase, pectinase, reaction time, and solid to liquid ratio. All the experiments were carried out in a bioreactor with working volume of 2 L. Approximately 98% efficiency hydrolysis was obtained, resulting in a concentration of total reducing sugar released of 160 g/L. It was concluded that pectinase improved the hydrolysis of starch from cassava. Reaction time was found to be significant until 7 h of reaction. A solid to liquid ratio of 1.0 was considered suitable for hydrolysis of starch from cassava. Amyloglucosidase was a significant variable in the process: after its addition to the reaction media, a 30%–50% increase in the amount of total reducing sugar released was observed. At optimal conditions the maximum productivity obtained was 22.9 g/(L·h).  相似文献   

Absence of postzygotic isolating mechanisms: evidence from experimental hybridization between two species of tropical sea urchins     

M. Aminur Rahman  Tsuyoshi Uehara  Aziz Arshad  Fatimah Md. Yusoff  Mariana Nor Shamsudin 《Journal of Zhejiang University. Science. B》2012,13(10):797-810

Two reef margin species of tropical sea urchins, Echinometra sp. C (Ec) and Echinometra oblonga (Eo), occur sympatrically on Okinawa intertidal reefs in southern Japan. Hybridization between these species was examined through a series of cross-fertilization experiments. At limited sperm concentrations, where conspecific crosses reached near 100% fertilization, both heterospecific crosses showed high fertilization rates (81%–85%). The compatibility of the gametes demonstrated that if gamete recognition molecules are involved in fertilization of these species, they are not strongly species-specific. We found that conspecific crosses reached peak fertilization levels much faster than did heterospecific crosses, indicating the presence of a prezygotic barrier to hybridization in the gametes. Larval survival, metamorphosis, and juvenile and adult survival of hybrid groups were nearly identical to those of their parent species. Hybrids from crosses in both directions developed normally through larval stages to sexually mature adults, indicating that neither gametic incompatibility nor hybrid inviability appeared to maintain reproductive isolation between these species. In adults, Ec×Ec crosses gave the highest live weight, followed by Eo (ova)×Ec (sperm), Ec (ova)×Eo (sperm), and Eo×Eo. Other growth performance measures (viz., test size, Aristotle’s lantern length, and gonad index) of hybrid groups and their parental siblings showed the same trends. The phenotypic color patterns of the hybrids were closer to the maternal coloration, whereas spine length, tube-foot and gonad spicule characteristics, pedicellaria valve length, and gamete sizes showed intermediate features. Adult F₁ hybrids were completely fertile and displayed high fertilization success in F₁ backcrosses, eliminating the likelihood that hybrid sterility is a postzygotic mechanism of reproductive isolation. Conversely, intensive surveys failed to find hybrid individuals in the field, suggesting the lack or rarity of natural hybridization. This strongly suggests that reproductive isolation is achieved by prezygotic isolating mechanism(s). Of these mechanisms, habitat segregation, gamete competition, differences in spawning times, gametic incompatibility or other genetic and non-genetic factors appear to be important in maintaining the integrity of these species.  相似文献   

Virtual Reference: Chat with Us!     

Mariana Lapidus  Irena Bond 《Medical reference services quarterly》2013,32(2):133-142

Virtual chat services represent an exciting way to provide patrons of medical libraries with instant reference help in an academic environment. The purpose of this article is to examine the implementation, marketing process, use, and development of a virtual reference service initiated at the Massachusetts College of Pharmacy and Health Sciences and its three-campus libraries. In addition, this paper will discuss practical recommendations for the future improvement of the service.  相似文献   

Another Year     

Mariana B. Davenport 《The Educational forum》2013,77(3)

  相似文献   

Conceptual Incoherence as a Result of the use of Multiple Historical Models in School Textbooks     

Niklas M. Gericke  Mariana Hagberg 《Research in Science Education》2010,40(4):605-623

This paper explores the occurrence of conceptual incoherence in upper secondary school textbooks resulting from the use of multiple historical models. Swedish biology and chemistry textbooks, as well as a selection of books from English speaking countries, were examined. The purpose of the study was to identify which models are used to represent the phenomenon of gene function in textbooks and to investigate how these models relate to historical scientific models and subject matter contexts. Models constructed for specific use in textbooks were identified using concept mapping. The data were further analyzed by content analysis. The study shows that several different historical models are used in parallel in textbooks to describe gene function. Certain historical models were used more often then others and the most recent scientific views were rarely referred to in the textbooks. Hybrid models were used frequently, i.e. most of the models in the textbooks consisted of a number of components of several historical models. Since the various historical models were developed as part of different scientific frameworks, hybrid models exhibit conceptual incoherence, which may be a source of confusion for students. Furthermore, the use of different historical models was linked to particular subject contexts in the textbooks studied. The results from Swedish and international textbooks were similar, indicating the general applicability of our conclusions.  相似文献   

Quantification of Helicobacter pylori levels in soil samples from public playgrounds in Spain     

Leonardo Martín Pérez  Francesc Codony  Daniela López Leyton  Mariana Fittipaldi  Bárbara Adrados  Jordi Morató 《Journal of Zhejiang University. Science. B》2010,11(1):27-29

Helicobacter pylori are ubiquitous Gram-negative bacteria with a high estimated level of infection in the world populations, but a majority of the infected persons are asymptomatic. This pathogen has been classified by the World Health Organization as a class I carcinogen and recognized as the causal agent of most peptic ulcers and chronic gastritis that might lead to stomach cancer. Although not all the transmission pathways of these bacteria into humans have been properly identified, enough data have suggested that the oral-oral or fecal-oral ones are the main infection routes. Helicobacter pylori have been detected in non-treated water and in drinking water, which suggested that water might be an important infection source. As childhood is the critical period of infection, the aim of the present work was to examine the presence of Helicobacter pylori in soil samples from public playing areas of Spanish parks.  相似文献   

Argumentation-teaching as a method to introduce indigenous knowledge into science classrooms: opportunities and challenges     

Mariana G. Hewson  Meshach B. Ogunniyi 《Cultural Studies of Science Education》2011,6(3):679-692

An innovative school science curriculum in South Africa requires the inclusion of African societal/cultural knowledge, such as indigenous knowledge (IK). The main project involves introducing argumentation to accomplish this requirement. We used a focus group plus critical incident technique to ascertain nine teachers’ understandings of argumentation and IK, their perceptions of how argumentation helps in teaching IK, examples of how argumentation-teaching had (or had not) worked in their classrooms, and their suggestions. Our results show that the teachers accepted argumentation as a viable approach to teach science and introduce IK into their classrooms.  相似文献   

Laboratory professionals’ attitudes towards ISO 15189:2012 accreditation: an anonymous survey of three Croatian accredited medical laboratories     

Ivana Lapi&#x;  Dunja Rogi&#x;  Matea Ivi&#x;  Marina Tomi evi&#x;  Mirjana Mariana Kardum Paro  Lovorka &#x;erek  Ines Alpeza Viman 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2021,31(2)

IntroductionEffective implementation and continual compliance with ISO 15189:2012 require ongoing commitment and active involvement of laboratory staff. Our aim was to assess attitudes regarding accreditation implementation by conducting a survey in three Croatian accredited medical laboratories.Materials and methodsAn anonymous survey consisting of 34 questions was distributed either electronically or in a paper form a week prior to scheduled annual audits. Distributions of answers regarding age, work experience, laboratory workplace, and education level and according to the respective laboratory were compared.ResultsThe overall response rate was 76% (225/297). Preference towards working in an accredited laboratory and a positive attitude were revealed by 70% and 56% participants, respectively, with better process documentation as the main advantage. Only 14% of responders considered themselves completely familiar with ISO 15189:2012. Total of 68% of responders felt that accreditation increases the usual workload, with excessive paperwork as the main contributor. Half of the responders declared partial agreement that accreditation requirements and expectations were clearly explained and claimed that their suggestions were taken into account only occasionally, which was especially emphasized by technical staff. The vast majority (89%) completely follow the prescribed protocols. Only 27% consider turnaround time monitoring useful. Competence assessment is considered efficient by 41% of responders. The majority (73%) prefer an online audit in times of COVID-19.ConclusionsDespite an overall positive attitude towards accreditation, further efforts are needed in providing better education about ISO 15189:2012 for technical staff and modifying formats of competence assessment, in order to achieve better adherence to ISO 15189:2012 requirements.  相似文献   

Plasticity of altruistic behavior in children     

Mariana Lozada  Paola D’Adamo  Natalia Carro 《Journal of moral education》2014,43(1):75-88

The present study investigates the plasticity of altruistic behavior in children, analyzing the effect of a short intervention on 6- to 7-year-olds. After a 10-session intervention performed in a school context, altruism significantly increased. The intervention, which included relaxation practices, cooperative activities and emotional security priming, positively modulated altruistic behavior in children, beyond reciprocation and reputation. The experiences of collaborating, feeling emotional security and attaining moments of relaxation increased participants’ awareness of themselves and of others, favoring the emergence of intrinsic altruism. These results are in line with our hypothesis that altruism is an embodied human resource, highly susceptible to experience within social contexts.  相似文献   

When inclusion excludes: a counter narrative of open online education     

Mariana Funes 《Learning, Media and Technology》2018,43(2):119-138

Open education aspires to democratize education, promote inclusion and effect change through social justice. These aspirations are difficult to realize in open, online environments, which enable multiple, and often conflicting, perspectives. This paper proposes a counter-narrative that surfaces certain operational norms of the internet and foregrounds their exclusionary nature. We offer an illustrative inventory of some social media interactional patterns to examine communication used in open online education communities. This examination leads us to conclude that language online is subject to a dialectical tension that both includes and excludes. We conclude that a different language is needed in open online educational environments; one that embraces exclusionary structures and strategic ambiguity, as well as the aspirations to further democratize education via digital means.  相似文献