A factor analysis of the preferred learning styles of Industrial Technology and Engineering undergraduate students at North Carolina Agriculture and Technical State University and at Iowa State University

Fazarro, Dominick E Iowa State University 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This study examined the learning style preferences of African American and European American undergraduate students in the Industrial Technology and Engineering programs at North Carolina A&T State University and Iowa State University. In this study, the independent variables employed were ethnicity, discipline, and the named institutions. The dependent variables were the 20 learning style preferences in the Productivity Environmental Survey (PEPS). Convenience sampling was used to collect 540 students. A factor analysis was used to determine the preferred learning styles for African American and European American students at each institution. In addition, the hypotheses were tested by the Box's M test in the discriminant analysis. The hypotheses were tested at an <italic>a priori</italic> level of .05 to ascertain significant differences in the factor structures or groups. The findings of the study concluded that: (1) there were differences in the factor loading profiles of African American and European American students at each institution, regardless of discipline, and (2) there were no differences between the factor loading profiles of Industrial Technology and Engineering students at either institution. Further analyses were generated to determine additional findings on African American and European American learning styles within their respective disciplines. The analyses consisted of examining if there were differences between factor loading profiles by combining both ethnic groups from each program, regardless of institution. The findings concluded that there were no differences between the factor loading profiles of the students enrolled in the two programs.

Roles and influences of the Governor's office in state policy-making for higher education: A two-state case study (Michigan, Kentucky)

Nichols, Gregory Scott Iowa State University 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This study focused on participant perceptions of roles and perceived influence of state Governors and their staffs in higher education policy-making. Reported increased activity by Governors and their staffs in education policy-making, coupled with increasing public demands and limited or reduced state resources for higher education lend relevance to this topic. Literature also suggests that higher education leaders and state officials may have differing views of their roles in state policy-making processes. The study was designed to capture participant perceptions as to processes, and roles and influence therein, not specific policy outcomes. Given the interpersonal and dynamic nature of the policy-making process, these perceptions were the focus of the study. Qualitative case study methodology was used in this study. Initially, a preliminary survey was administered to Governor's education policy advisors from ten states. Thereafter, a field study was conducted to examine policy-making in the states of Michigan and Kentucky. The study presents relevant background information on each state and commentary from approximately 50 in-depth personal interviews with governmental and education leaders in these states. The researcher has worked as a staff member of his state legislature, Governor's office, and as Executive Director of his state Board of Regents prior to assuming his current position as a Special Assistant to the President of Iowa State University. The commentary and emergent themes of the study are informed by those experiences as well as study data and existing literature. Study findings included a confirmation of the state-to-state variation in: public sector system design, social/economic/political culture, expectations for Executive branch involvement in higher education policy-making, and the roles and influence of the Governor and staff. While some similarities in states' approaches were noted as well, participants believed the circumstances in their state were unique from any other. The perceptions by and of some very experienced Governor's aides and state government and higher education officials in the study states may be of value in assessing similar situations. The study design, however, does not provide for quantifiable, transferable results that can necessarily be applied to differing points in time or differing locations.

Field evaluation of winterkill in annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis stolonifera L.)

Valverde, Federico J Iowa State University 2007 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Winterkill, in putting greens and fairways of annual bluegrass ( Poa annua L.) and creeping bentgrass (Agrostis stolonifera L.), is a common phenomenon in North-Central Region of United States and in other temperate areas. Extensive research in controlled environments has evaluated injury mechanisms in creeping bentgrass and annual bluegrass. A large number of studies have evaluated winter injury in other turfgrass species and in cereal grasses. Most agree that damages can be explained by factors such as intracellular and extracellular ice formation, cellular dehydration and hydration, plant desiccation, macro scale tissue and organ rupture, diseases, anoxia, cellular acidosis, oxidative stress and retarded growth. Despite the vast amount of information generated during several decades of research, winterkill in creeping bentgrass and annual bluegrass is a problem that still leaves golf course superintendent with many unanswered questions. It is proposed that, to minimize winterkill, it is necessary to understand the high complexity of the system at field level and not only in controlled environments. The purpose of this research was to quantify the relative injury on putting greens as it relates to snow cover, ice formation, desiccation, crown hydration, and freeze/thaw cycles. Our approach was to evaluate the relative amount of injury that is associated with various scenarios of winter, instead of focusing solely on the mechanisms that cause the injury. Also, it is of interest to determine not only what condition causes the most winter injury, but when during the season does damage occur and if it is worth the expense or effort to try and minimize the injury by taking action. This study was conducted at the Iowa State University (ISU) Horticulture Research Center and at ISU Veenker Memorial golf course, both in Ames Iowa. The species evaluated were creeping bentgrass (Agrostis stolonifera L) and annual bluegrass (Poa annua L). Ten possible winter scenarios; dry/open, wet, ice continuous, snow continuous, impermeable artificial cover and ice continuous, ice removal, ice/melt freeze, snow removal/melt freeze, an artificial permeable turf cover, and artificial permeable turf cover with snow, were created on two Iowa putting greens in January, February and March of 2003, 2004, and 2005. Dry weight yield produced by samples collected in the field and grown on controlled chambers was used to indicate the amount of winter injury. Hourly temperatures were registered through the length of the study. Growing degree days (GDD) and stress degree days (SDD) were calculated with temperature data. Creeping bentgrass was not killed under any treatment. Continuous ice cover of 66 days caused creeping bentgrass bleaching but never resulted in any turf kill or decline in creeping bentgrass cover. Annual bluegrass was susceptible to winter injury when exposed to ice encasement. Damages by ice formation occurred during the first 15 days after encasement. The formation and type of ice is more important than the duration of ice cover in predicting annual bluegrass winter injury when ice is present. In both species, the treatments that offered a better visual quality at the end of the winter period were those that had a better protection such as impermeable-ice, permeable-snow, and snow treatments. However, the visual results did not necessarily mirror on those results of biomass production. In regard to temperatures and insulation characteristics of winter practices, greens without any protective layer suffer almost twice the amount of stress degrees that snow covered plots. As accumulative units, SDD 0°C had larger mean separation than any of the temperature variables; as such it was a better descriptor of intensity or risk of damage than temperatures alone. In the north central region of the United States, the use of artificial covers combined with snow blankets provided the best insulation and therefore the best condition for turf survival and early spring turf quality. Keywords. winterkill, annual bluegrass, creeping bentgrass, ice, temperature, stress degree days.

Photochemistry and internal eliminations of organosulfur and organoselenium compounds

McCulla, Ryan David Iowa State University 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation focuses on two specific aspects of the chemistry of organosulfur and organoselnium compounds. The first is the internal elimination of the sulfinate esters, sulfonic esters, and the effects of silyl-substitution on the internal elimination of sulfoxides. The internal elimination of sulfinate esters proceeds through a 5-membered transition state whereas sulfonate esters proceed through a 6-membered transition state. Using computations, it was determined in the 6-membered transition state that substantial charge separation occurs, but less charge separation is observed in the 5-membered transition state. The ability of the sulfonate leaving group to incorporate charge favors the 6-member transition state. In the 5-centered elimination, a nucleophilic-electrophilic mismatch in the transition state is made worse when the sulfur atom is more positively charged, as in the sulfonate. Silyl groups attached at either the Calpha or Cbeta position of an alkyl sulfoxide lower the activation enthalpy of the sulfoxide syn elimination reaction by a few kcal mol-1. A Silyl substituent at Cbeta can stabilize the transition state by either stabilizing the developing positive charge at Calpha or negative charge at Cbeta. Silyl substitution at Calpha is not positioned to interact favorably with either developing charge in the transition state, and the lower activation barrier is more likely a response to the overall less endothermic reaction than any silyl interaction in the transition state. The second topic is the photochemistry of organosulfur and organoselenium ylides. The photodeoxygenation of dibenzoselenophene oxide (DBSeO) was found to have a greater quantum efficiency in producing O(3P) than dibenzothiophene oxide (DBTO). However, the photo sensitization and direct irradiation of DBTO (or DBSeO) were found to undergo photodeoxygenation by, in most cases, different mechanisms. Both of these conclusions were supported by monitoring the relative oxidized product ratios. Using calculations, the bond strengths of a variety of sulfur and selenium ylides were determined. This information is used in the elucidation of the photodeoxygenation mechanism of diaryl sulfoxides and selenoxides.

The Iowa Chemistry Education Alliance, ICEA: Process and product

Burke, Kathleen Annette Iowa State University 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The Iowa Chemistry Education Alliance, ICEA, supported by Department of Education Star Schools funding (R203F5000198), was both a Process and a Product. The Process included: (a) Design and support of high school teacher training sessions that incorporated distance learning techniques, cooperative learning and guided inquiry strategies, and a constructivist, student-centered classroom focus; (b) Design and incorporation of eight supplemental learning modules, corresponding assessment rubrics, and supporting videotapes into the existing Iowa high school chemistry curriculum; (c) Adaptation of the learning modules throughout the course of the academic year while the units were being integrated into the existing curriculum; (d) Modification and final editing of the curriculum modules and videotapes. The Product consisted of eight supplemental ICEA learning modules with corresponding assessment rubrics, and three supporting videotapes. To integrate ICEA materials into the existing curriculum, students at high schools around the state of Iowa conducted cooperative, guided-inquiry laboratory exercises. Via electronic mail and Iowa's two-way interactive audio-video system, the Iowa Communications Network (ICN), they discussed strategies for experimentation and shared results obtained. Invited guest experts also visited student groups via the ICN. Teachers conducted regular biannual on-site face-to-face planning meetings. These were augmented and supported by weekly or biweekly "staff" meetings conducted via the ICN. From the original three hundred students in four central Iowa high schools (rural, urban, and suburban), by its third and fourth year, the Project evolved to include over 1500 students in twenty-five high schools statewide.

The identification and characterization of electronic defect bands in organic photovoltaic devices

Carr, John Anthony Iowa State University 2014 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In any microelectronic device, fundamental physical parameters must be well understood if electronic properties are to be successfully optimized. One such prominent parameter is energetic trap states, which are well-known to plague amorphous or otherwise impure semiconducting materials. Organic semiconductors are no strangers to such states and their electronic properties are evidently tied to these defects. This dissertation aims to elucidate these states in organic photovoltaic (OPV) devices. The literature to date is first reviewed and the author's contributions are subsequently detailed. Within the community, several techniques have been leveraged to study these mid-gap states. Atop the list are optical, capacitance and current based measurements and each has provided important pieces to the overall defect profile. Piecing together the works to date, organic photovoltaic materials are depicted as disordered semiconductors with a seemingly continuous distribution of both energetically shallow and deep trap bands. Upon blending the pure materials to create the modern day bulk heterojunction -- the currently preferred photovoltaic architecture -- energetic disorder increases and new trap bands appear. These states have been shown to stem from both intrinsic (e.g. structural disorder) and extrinsic (e.g. oxygen and synthesis contaminates) sources and it is quite clear that such states can have profound effects on, if not completely control, the electronic properties and long term stability of OPV devices. Most prominently, these states are known to enhance trap-assisted recombination, induce Fermi-level pinning and generate space-charge effects. Though these mid-gap traps have a large negative impact, they also can give an advantageous inherent doping, improving conductivity and interfacial electric fields. Evidently, continued progress in understanding the nature, sources, affects and possible mitigation of these defects in both current and future materials will be crucial to the optimization of this promising technology. The primary work of this study is to build upon these reports and to further the current body of knowledge on the identification and characterization of defect states in OPV devices. Capacitance techniques are heavily employed herein. As such, the accurate capacitance characterization of OPV devices was first visited. It was found that, owing to thinner films and larger series resistance, the series based parasitics could not be neglected in the typical frequency range of interest or significant errors and misinterpretations were introduced. Armed with this more accurate model, deeper, previously unknown trap states were then identified using low frequency capacitance measurements coupled with a point by point differential of high frequency capacitance-voltage measurements. The discovered defects remain important as it is those states closer to the midgap which more efficiently contribute to recombination and can be detrimental to device performance. More generally, the presented technique gives a generic overview of the capacitance response of OPV devices -- resolving anomalies and enabling others to better study the defect profile in their devices. Lastly, the pre-exponential factor of trap emission, also known as the attempt-to-escape frequency, was characterized. This parameter is essential if trap occupancy kinetics are to be accurately described -- important for any measurement or model dependent on the detrapping dynamics. It was found that the polymer based devices studied herein have a prefactor within a similar range, yielding similar trap capture cross sections. Not only does this give guidance as to the proper value to be used in the detrapping measurements/models, but also indicates that the trapping mechanisms in these devices are likely similar.

Studies of solute transport through fractured till in Iowa

Helmke, Martin Frederick Iowa State University 2003 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Fractures may provide pathways for agricultural chemicals to reach aquifers through till units that have traditionally been considered effective barriers to contaminant transport. Till units were studied at three sites in Iowa that represented three landform regions, till ages from 12.5 to >730 ka, and depths from 1 to 27.5 m. Fractures were present at all study locations and at all depths, including one site where fractures intersected an aquifer at 30 m depth. Laboratory experiments using eight large (0.40 to 0.45 m in length and 0.43 m in diameter), undisturbed columns of till showed bulk hydraulic conductivity (<italic>K_b</italic>) ranging from 7.7 × 10<super>−10</super> to 3.8 × 10<super>−5</super> m/s, which is generally greater than the matrix hydraulic conductivity reported in the literature. Laboratory experiments with KBr, PFBA, PIPES, KNO₃, and atrazine as tracers were used to produce breakthrough curves (BTCs). First arrival velocities of Br ranged from 0.004 to 64.8 m/d—10 to 100 times faster than predicted using the equivalent porous medium (EPM) assumption. Similar velocities of NO₃ and atrazine were observed for columns collected from depths of less than 3 m. In deeper columns, sorption (atrazine) and degradation (NO₃ and atrazine) retarded transport. Tracers were not affected significantly by fracture origin or orientation. Separation of conservative tracers with different aqueous diffusion coefficients was observed during the rising and tailing limbs of BTCs, which indicates that matrix diffusion was a controlling process. Laboratory BTCs were compared against model-simulated BTCs using three approaches: the Mobile-Immobile Model (MIM), the Parallel-plate Discrete Fracture Model (PDFM), and a 3-Dimensional Discrete Fracture Model (3-D DFM). All three model approaches were reasonable predictors of the BTCs (goodness-of-fit statistic <italic>d₁</italic> ranged from 0.751 to 0.959). The results of this study demonstrate that fractures may have a controlling influence on solute transport through till units in Iowa. Contaminants may be transported rapidly through thin aquitards of fractured till, but non-conservative compounds are likely to be retarded or degraded in thicker till units. Fractures should be considered in groundwater studies in glaciated regions and in assessments of aquifer vulnerability to non-point source pollution.

Spin models for the single molecular magnet Mn12-AC

Al-Saqer, Mohamad A Iowa State University 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The single molecular magnet (SMM) Mn12-AC attracted the attention of scientists since the discovery of its magnetic hystereses which are accompanied by sudden jumps in magnetic moments at low temperature. Unlike conventional bulk magnets, hysteresis in SMMs is of molecular origin. This qualifies them as candidates for next generation of high density storage media where a molecule which is at most few nanometers in size can be used to store a bit of information. However, the jumps in these hystereses, due to spin tunneling, can lead to undesired loss of information. Mn12-AC molecule contains twelve magnetic ions antiferromagnetically coupled by exchanges leading to S = 10 ground state manifold. The magnetic ions are surrounded by ligands which isolate them magnetically from neighboring molecules. The lowest state of S = 9 manifold is believed to lie at about 40 K above the ground state. Therefore, at low temperatures, the molecule is considered as a single uncoupled moment of spin S = 10. Such model has been used widely to understand phenomena exhibited by the molecule at low temperatures including the tunneling of its spin, while a little attention has been paid for the multi-spin nature of the molecule. Using the 8-spin model, we demonstrate that in order to understand the phenomena of tunneling, a full spin description of the molecule is required. We utilized a calculation scheme where a fraction of energy levels are used in the calculations and the influence of levels having higher energy is neglected. From the dependence of tunnel splittings on the number of states include, we conclude that models based on restricting the number of energy levels (single-spin and 8-spin models) lead to unreliable results of tunnel splitting calculations. To attack the full 12-spin model, we employed the Davidson algorithm to calculated lowest energy levels produced by exchange interactions and single ion anisotropies. The model reproduces the anisotropy properties at low temperature very well. At higher energy levels, however, the agreement is qualitative. Toward better quantitative agreement, further terms must be included in the Hamiltonian and further developments of computation algorithms are needed to overcome the size of the problem.

Investigating In-Field Practices to Mitigate Nitrate Loss from Subsurface Drainage in Iowa in a Corn/Soybean Rotation

Waring, Emily Rose Iowa State University ProQuest Dissertations & The 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation evaluates various in-field management practices intending to quantify their impact on nitrate-N loss via subsurface drainage in corn and soybean systems. The focus is nitrogen retention in two ways: fertilizer timing and cover crops. The first chapter is a general introduction to nutrient management in agriculture. The second chapter investigates fertilizer timing and concludes that there is not a benefit to applying anhydrous ammonia in the fall vs. spring, so long as the fall-applied N is applied with a nitrification inhibitor, when the soil is 10 degrees C and cooling, and at the maximum return to nitrogen. The third chapter presents data from a cover crop mixture study with lysimeters, exploring cover crop options beyond winter cereal rye. Oats before corn had no negative impacts on corn yield while improving spring water quality. There was no water or soil quality benefit to adding more species with winter cereal rye which grew successfully even in the northern half of the state. The fourth chapter reports on a cover crop management study including both no-tillage and conventional tillage. At this particular site in north-central Iowa, winter cereal rye was more successful at improving water quality with tillage compared to no tillage. However, after 11 (in the conventional system) or 15 (in the no-tillage system) years, there were increases in soil organic carbon content in all conservation practices. Switching to broadcast seeding improved cover crop growth in both tillage treatments. The fifth chapter includes general conclusions and recommendations for future research. The general conclusions of this dissertation are that the management of nitrogen in Iowa is complex due to its mobility in water and weather-dependent transformations. The most consistent way to improve water quality is to increase the months that living crops are growing. General recommendations include more research on the potential of hairy vetch in Iowa, more long-term studies to better understand soil health and its influences on water quality, and research on the benefits of combining both edge-of-field and in-field practices.

Poverty and food insecurity in rural Iowa: An examination of four food desert counties

Bitto, Ella Annette Iowa State University 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Pockets of poverty are found throughout rural Iowa. Rural America is comprised of people with varying backgrounds who much make their livelihoods in a society that is increasingly a part of a global village. Living in Iowa, called by many the breadbasket of the world, does not necessarily mean that everyone will have equal access to food. In fact, over 46,600 Iowans between 2001--2003 experienced some form of poverty and 9.4 percent were defined as food insecure. This dissertation examines the economic structure of Iowa's counties to determine how agriculture and local business influence per capita income, inequality, and poverty. One examination of how poverty impacts people is food insecurity. The study focuses on four Iowa counties defined as food deserts---places with four or fewer grocery stores. In these counties I find many individuals participating in the countermovement---the alternative market---across all income levels as people grow their own gardened food and share with family, neighbors and friends. Participating in the countermovement provides access to goods and services that individuals might otherwise not be able to economically afford. Data suggests that individuals who are food secure are more likely to participate in community organizations, be more socially connected, and more likely to participate in the countermovement. For communities, when the basic needs are completely met, people are more likely to become involved in community organizations and create a larger social capital base. Some research suggests that improvement in health care, nutrition, and housing will create a spill-over effect onto communities that can establish higher forms of social and financial capital as well as having a healthier community.