Search results

Title: Studies of genera cytophaga-flavobacterium in context of the soil carbon cycle
Creator: Mayrberger, Jenifer M.
Date: 2011
Collection: Electronic Theses & Dissertations
Description: There is a great need to understand the global carbon cycle; with specific interest in the cycling of soil carbon. This need is two-fold and interconnected. The global climate change is in-part due to the loss of soil organic carbon and the reduced ability of soils to sequester carbon. Also, to maintain sustainable, high yielding agriculture, carbon loss from soil must be mitigated and in turn this can restore the ability of soils to sequester carbon. A specific group of bacteria, the...
Show moreThere is a great need to understand the global carbon cycle; with specific interest in the cycling of soil carbon. This need is two-fold and interconnected. The global climate change is in-part due to the loss of soil organic carbon and the reduced ability of soils to sequester carbon. Also, to maintain sustainable, high yielding agriculture, carbon loss from soil must be mitigated and in turn this can restore the ability of soils to sequester carbon. A specific group of bacteria, the Cytophaga-Flavobacterium (CF), are of interest in these contexts because evidence suggests that they have the potential to exacerbate the loss of organic carbon from soil. The CF are globally distributed, often detected as organisms responsible for degradation or organic compounds. Other research has demonstrated their active presence in soil, especially the zone around plant roots. Most importantly, these bacteria produce a large assortment of hydrolytic enzymes that can degrade complex carbohydrates. The first studies in this dissertation were intended to investigate the phylogenic diversity and distribution of CF in soil. CF specific clone libraries were generated to investigate a possible link between the CF and soils under different land management and use history, and thus different carbon contents. Also in this dissertation, we tested the hypothesis that Flavobacterium soil isolates would weaken, or degrade, remolded aggregates generated with xylan, a complex carbohydrate, in an effort to describe how Flavobacterium can be responsible for the loss of organic carbon from soil. While the initial studies were exploratory in design, some specific comparisons were made. The CF community from the agricultural soil was determined to be a subset of the communities found in the non-agricultural soils. When the CF communities from deciduous forest soil and fertilized deciduous forest soil were compared, no differences in phylogenetic diversity or distribution were identified. A significant difference in the phylogenetic distribution was detected when the CF community from conventionally tilled agricultural soils was compared to the community from a no-till agricultural management. The diversity of the community from the tilled soil was greater than the community from the no-till soil. Remolded aggregates composed with xylan were challenged with nine Flavobacterium spp. isolated from soil to test the hypothesis that they would degrade the xylan causing a reduction in the erosive strength of the remolded aggregates. In natural soils, increased breakage can lead to a loss of carbon from the soil. The erosive strength is a measure of how readily aggregates will break apart. These values are determined by eroding the aggregates in precision-machined soil aggregate erosion chambers and recording the length of time and amount of force required to remove layers of the aggregate. Using two measures of erosive strength, the highest recorded value, or peak erosive strength, and the total erosive strength for all layers of the aggregate, the aggregates treated with Flavobacterium spp. were compared to uninoculated controls. It was determined that six of the nine species significantly reduced the peak erosive strength and four species also reduced the total erosive strength. These data support the hypothesis that Flavobacterium spp. contribute to a loss of organic carbon from soil. These works can now be extended, using the same techniques, by investigating the role of Flavobacterium as part of the whole bacterial community, as well as investigating the influence of temperature on their degradation activity.
Show less

Title: Between word and meaning : wit, modernism, and perverse narrative
Creator: Holcomb, Brian D.
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Differentiation of bullet type based on analysis of gunshot residue using inductively coupled plasma mass spectrometry
Creator: Udey, Ruth Norma
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Alternative pedagogy : empowering teachers through real talk
Creator: Hernandez, Pablo I.
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Exploring couple relationships in challenging coparenting contexts
Creator: Hock, Robert Matthew
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Social influence in online health discussions : an evaluation of online graduate student support groups
Creator: Maloney, Erin Kay
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Germany after the fall : migration, gender and East-West identities
Creator: Hicks, Bethany E.
Date: 2010
Collection: Electronic Theses & Dissertations

Title: L2 gender facilitation and inhibition in spoken word recognition
Creator: Behney, Jennifer N.
Date: 2011
Collection: Electronic Theses & Dissertations
Description: This dissertation investigates the role of grammatical gender facilitation and inhibition in second language (L2) learners' spoken word recognition. Native speakers of languages that have grammatical gender are sensitive to gender marking when hearing and recognizing a word. Gender facilitation refers to when a given noun that is preceded by an adjective with the same gender marking (e.g., in Italian, bella casa "beautiful _{Feminine Adjective} house _{Feminine Noun}") is...
Show moreThis dissertation investigates the role of grammatical gender facilitation and inhibition in second language (L2) learners' spoken word recognition. Native speakers of languages that have grammatical gender are sensitive to gender marking when hearing and recognizing a word. Gender facilitation refers to when a given noun that is preceded by an adjective with the same gender marking (e.g., in Italian, bella casa "beautiful _{Feminine Adjective} house _{Feminine Noun}") is recognized more quickly than if the noun is preceded by an adjective that does not have a gender marking (e.g., grande casa "big _{Neutral Adjective} houseFeminine Noun"). Gender inhibition refers to when a noun that is preceded by an adjective that has the wrong gender marking (e.g., *bello casa "beautiful _{Masculine Adjective} house _{Feminine Noun}") is recognized more slowly than if the noun is preceded by an adjective that does not have a gender marking (e.g., Bates, Devescovi, Hernandez, & Pizzamiglio, 1996; Dahan, Swingley, Tanenhaus, & Magnuson, 2001; Davidson, de la Fuente, Montrul, & Foote, 2011; Guillelmon & Grosjean, 2001). Effects of gender facilitation and gender inhibition among late second language (L2) learners are less strong than those found among native speakers (Davidson, et al., 2011; Foote, 2011) or nonexistent (Guillelmon & Grosjean, 2001). These earlier L2 studies, however, examined only learners whose first language (L1) was English, which does not have grammatical gender. In this study I compare the spoken word recognition of L2 learners with gender in the L1 to those without gender in the L1 in three different tasks (which differed in terms of automatic versus controlled processing) in order to investigate gender facilitation and inhibition in the L2 and how it is affected by the type of task and the transparency of the gender marking on the noun. A control group of 24 native speakers and 72 advanced learners of Italian divided in 3 experimental groups completed the three spoken word recognition tasks. The learners were placed into one of the 3 groups on the basis of gender in the L1: (a) Romance L1s that have gender systems similar to that of Italian (e.g., Spanish); (b) L1s that have gender systems different from that of Italian (e.g., Russian); and (c) L1s that do not have gender (e.g., English). The participants listened to adjective-noun combinations and responded by (a) repeating the noun, (b) by identifying the gender of the noun, or by (c) indicating the grammaticality of the adjective and the noun together. The response times and the accuracy of the participants' responses were recorded and analyzed with mixed measures ANOVAs and t tests. I predicted that the native speakers and all of the learners would show effects of inhibition in the more controlled explicit tasks and that the transparency of the gender of the noun would affect the speed with which they identified the nouns. I predicted that only the native speakers and the L1 Romance learners would show effects of facilitation and/or inhibition in the implicit, less controlled task. The results showed that learners of Italian who have Romance gender in the L1 are similar to native speakers in their processing of gender in the L2. Learners who have another (non-Romance) gender system in the L1 pattern more similarly to learners who do not have any gender in the L1, at least in controlled processing tasks. All participants were influenced by the transparency of the gender on the noun, but native speakers and L1 Romance learners were less affected than the other two learner groups. The findings are discussed in terms of the role that gender plays in the lexical access of L2 learners and how it differs from that of native speakers. The findings are also discussed in terms of implications for L2 acquisition of grammatical gender.
Show less