Oregon State University

About: Oregon State University is a education organization based out in Corvallis, Oregon, United States. It is known for research contribution in the topics: Population & Climate change. The organization has 28192 authors who have published 64044 publications receiving 2634108 citations. The organization is also known as: Oregon Agricultural College & OSU.

The influence of history of science courses on students' views of nature of science

Abstract: This study (a) assessed the influence of three history of science (HOS) courses on college students' and preservice science teachers' conceptions of nature of science (NOS), (b) examined whether participants who entered the investigated courses with a conceptual framework consistent with contemporary NOS views achieved more elaborate NOS understandings, and (c) explored the aspects of the participant HOS courses that rendered them more ''effective'' in influencing students' views. Participants were 166 undergraduate and graduate students and 15 preservice secondary science teachers. An open-ended questionnaire in conjunction with individual interviews, was used to assess participants' pre- and postinstruction NOS views. Almost all participants held inadequate views of several NOS aspects at the outset of the study. Very few and limited changes in participants' views were evident at the conclusion of the courses. Change was evident in the views of relatively more participants, especially preservice science teachers, who entered the HOS courses with frameworks that were somewhat consistent with current NOS views. Moreover, explicitly addressing certain NOS aspects rendered the HOS courses relatively more effective in enhancing participants' NOS views. The results of this study do not lend empirical support to the intuitively appealing assumption held by many science educators that coursework in HOS will necessarily enhance students' and preservice science teachers' NOS views. However, explicitly addressing specific NOS aspects might enhance the effectiveness of HOS courses in this regard. Moreover, the study suggests that exposing preservice science teachers to explicit NOS instruction in science methods courses prior to their enrollment in HOS courses might increase the likelihood that their NOS views will be changed or enriched as a result of their experiences with HOS. fl 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 1057 - 1095, 2000

RNA silencing genes control de novo DNA methylation

Abstract: Cytosine DNA methylation silences harmful DNAs such as transposons and retroviruses ([ 1 ][1]). Maintenance DNA methyltransferases propagate pre-existing DNA methylation in the CG sequence context by methylating hemi-methylated sites after DNA replication. Much less is understood about how invasive

Recent Advances in Our Knowledge of the Myxozoa

Abstract: In the last few years two factors have helped to significantly advance our understanding of the Myxozoa. First, the phenomenal increase in fin fish aquaculture in the 1990s has lead to the increased importance of these parasites; in turn this has lead to intensified research efforts, which have increased knowledge of the development, diagnosis. and pathogenesis of myxozoans. The hallmark discovery in the 1980s that the life cycle of Myxobolus cerebralis requires development of an actinosporean stage in the oligochaete. Tubifex tubifex, led to the elucidation of the life cycles of several other myxozoans. Also, the life cycle and taxonomy of the enigmatic PKX myxozoan has been resolved: it is the alternate stage of the unusual myxozoan, Tetracapsula bryosalmonae, from bryozoans. The 18S rDNA gene of many species has been sequenced, and here we add 22 new sequences to the data set. Phylogenetic analyses using all these sequences indicate that: 1) the Myxozoa are closely related to Cnidaria (also supported by morphological data); 2) marine taxa at the genus level branch separately from genera that usually infect freshwater fishes; 3) taxa cluster more by development and tissue location than by spore morphology; 4) the tetracapsulids branched off early in myxozoan evolution, perhaps reflected by their having bryozoan, rather than annelid hosts; 5) the morphology of actinosporeans offers little information for determining their myxosporean counterparts (assuming that they exist); and 6) the marine actinosporeans from Australia appear to form a clade within the platysporinid myxosporeans. Ribosomal DNA sequences have also enabled development of diagnostic tests for myxozoans. PCR and in situ hybridisation tests based on rDNA sequences have been developed for Myxobolus cerebralis, Ceratomyxa shasta, Kudoa spp., and Tetracapsula bryosalmonae (PKX). Lectin-based and antibody tests have also been developed for certain myxozoans, such as PKX and C. shasta. We also review important diseases caused by myxozoans, which are emerging or re-emerging. Epizootics of whirling disease in wild rainbow trout (Oncorhynchus mykiss) have recently been reported throughout the Rocky Mountain states of the USA. With a dramatic increase in aquaculture of fishes using marine netpens, several marine myxozoans have been recognized or elevated in status as pathological agents. Kudoa thyrsites infections have caused severe post-harvest myoliquefaction in pen-reared Atlantic salmon (Salmo salar), and Ceratomyxa spp., Sphaerospora spp., and Myxidium leei cause disease in pen-reared sea bass (Dicentrarchus labrax) and sea bream species (family Sparidae) in Mediterranean countries.

Wideband low-distortion delta-sigma ADC topology

Abstract: A /spl Delta//spl Sigma/ topology with reduced sensitivity to opamp nonlinearities is described. The technique is effective even for very low oversampling ratios, and can be used for any modulation order. Techniques for reducing other nonideal effects are also proposed.

Protein Hydrolysates from Pacific Whiting Solid Wastes

Abstract: Alcalase and Neutrase showed optimum activity against Pacific whiting solid wastes (PWSW) at pH 95, 60 °C and pH 70, 55 °C, respectively Alcalase had a higher proteolytic activity than Neutrase Enzyme concentration, reaction time, and waste/buffer ratio significantly affected the hydrolysis and nitrogen recovery (NR) (p < 005) Optimum conditions for PWSW hydrolysis were 20 AU Alcalase/kg, 1 h reaction time, waste/buffer ratio of 1:1 (w/v) Correlation between the degree of hydrolysis (DH) and NR (R2 = 0970−0978) was high Freeze-dried hydrolysate was brownish yellow in color (L* = 5459, a* = 670, b* = 2789) and contained 277% moisture, 7997% protein, 1344% ash, and 383% lipid Amino acid composition of freeze-dried hydrolysate was similar to that of PWSW and Pacific whiting muscle but tryptophan was reduced to 2150% and 1474%, respectively Keywords: Waste; Pacific whiting; hydrolysate; Alcalase; Neutrase