164 research outputs found
What Works in Honors: Discovering “London as a Detective Story”
An honors program director and university archivist/librarian team up to offer a two-week study abroad course that blends itinerant offerings of City as Text™ with fixed support for first-time student encounters with archival collections at the British Library and the National Archives
Using virtual spatial audio to aide visually impaired atheletes
Many people with visual impairments actively play soccer, however the task of making the game accessible is met with significant challenges. These challenges include: the need to constantly talk to signify location and detecting the positions of silent objects on the field. Our work aims to discover methods to help persons with visual impairments play soccer more efficiently and safely
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Frost resistance of pea genotypes (Pisum sativum L.) grown in the field on ground level and raised beds, and under controlled laboratory conditions
The effect of raised bed culture on winter survival of ten pea
genotypes (Pisum sativum L.), differing in inherent cold hardiness
and growth habit, was studied under two climatic conditions: a moist
semi-maritime winter (Corvallis, Oregon) and a cold continental
winter (Weston, Oregon). An assessment of winter injury was based
on three indices: percent survival, plant weight, and a visually
assigned damage rating. Varying percentages of seven genotypes
survived at Corvallis and of six at Weston.
Planting on raised beds at Corvallis significantly increased the
mean percent survival and plant weight and decreased the mean damage
rating. Of two Corvallis planting dates, September 18 and
October 10, 1975, the latter had a significantly higher mean percent
survival and a lower mean damage rating.
At Weston, the mean percent survival was higher on ground
level plantings. Plant weight was not affected by planting method.
At this location there was a significant interaction between planting
method and genotype. Of the six surviving genotypes only the two
least hardy had significantly higher percent survival on ground level
plantings.
Controlled freezing tests between -2 and -10° C were conducted
on four genotypes, AW, WH2, INTl, and S4, to determine their relative
levels of inherent cold hardiness and cold acclimating ability.
An electrolyte leaching method of determining the extent of freezing
injury ranked the genotypes as follows, from most hardy to least:
AW = WH2 > INTl > S4. A visual estimation of damage ranked the
genotypes as follows: WH2 > AW > INTl > S4. In comparison, percent
survival in the field studies ranked the four genotypes: AW >
WH2 > INT1 > S4. Genotypes with a compact growth habit, AW
and WH2, acclimated [less than or equal to] 4° C, whereas those with an upright growth
habit, INTl and S4, acclimated 1-2° C
Factors regulating loblolly pine (pinus taeda L.) somatic embryo development
"June, 1989.""This manuscript is based on results obtained in IPC research and is to be presented at the Southern Forest Tree Improvement Conference in June, 1989.
Electrochemical Oxidative Fluorination of an Oxide Perovskite
We report on the electrochemical fluorination of the A-site vacant perovskite ReO3 using high-temperature solid-state cells as well as room-temperature liquid electrolytes. Using galvanostatic oxidation and electrochemical impedance spectroscopy, we find that ReO3 can be oxidized by approximately 0.5 equiv of electrons when in contact with fluoride-rich electrolytes. Results from our density functional theory calculations clearly rule out the most intuitive mechanism for charge compensation, whereby F-ions would simply insert onto the A-site of the perovskite structure. Operando X-ray diffraction, neutron total scattering measurements, X-ray spectroscopy, and solid-state 19F NMR with magic-angle spinning were, therefore, used to explore the mechanism by which fluoride ions react with the ReO3 electrode during oxidation. Taken together, our results indicate that a complex structural transformation occurs following fluorination to stabilize the resulting material. While we find that this process of fluorinating ReO3 appears to be only partially reversible, this work demonstrates a practical electrolyte and cell design that can be used to evaluate the mobility of small anions like fluoride that is robust at room temperature and opens new opportunities for exploring the electrochemical fluorination of many new materials
Characterization of a Bacterial Contaminant in Loblolly Pine Tissue Culture
Bacterial contamination of immature seed explants can decrease the efficiency in initiating and establishing pine embryogenic cultures. A type of contaminant commonly observed surrounding the megagametophyte explant of immature loblolly pine (Pinus taeda L.) appears as a white to creamy halo on the surface or within the culture medium. This contaminant appears within 24-48 hours after culturing the immature seed. The severity of the contamination varies by year and family. The pattern of contamination among seeds pooled from several cones did not suggest operator technique as the source of contamination. Tests with seeds separated by cone during sterilization and culture suggest that the source of the contamination was from seeds of specific cones. To better understand the causal bacterium and provide insight to help prevent or decrease the occurrence of contamination, several isolates taken from different contaminated explants were identified. This identification was done by PCR amplification of a 500bp sequence of a 16S ribosomal RNA gene. The closest match in terms of sequence similarity was Erwinia amylovora. Erwinia species are the causal agents of several economically important diseases. For example, fire blight (E. amylovora) in the Roseaceae family that affects apple and pear trees, and soft rot (E. carotovora) in several crops including potato. Our results suggest that Erwinia may also infect immature loblolly pine seeds and is a probable causal agent of this type of bacterial contamination in pine tissue culture. We have been able to significantly reduce the negative impact of this contamination and increase culture establishment efficiency by separating seeds by cone for sterilization and culture.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003
Tobacco seeds simultaneously over-expressing Cu/Zn-superoxide dismutase and ascorbate peroxidase display enhanced seed longevity and germination rates under stress conditions
Reactive oxygen species (ROS) are produced during seed desiccation, germination, and ageing, leading to cellular damage and seed deterioration and, therefore, decreased seed longevity. The effects of simultaneous over-expression of two antioxidant enzymes on seed longevity and seed germination under stressful conditions were investigated. Transgenic tobacco simultaneously over-expressing the Cu/Zn-superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) genes in plastids showed normal growth and seed development. Furthermore, the transgenic seeds displayed increased CuZnSOD and APX enzymatic activities during seed development and maintained antioxidant enzymatic activity after two years of dried storage at room temperature. The two-year stored non-transgenic seeds (aged NT seeds) had higher levels of ion leakage than the two-year stored transgenic seeds (aged CA seeds), indicating membrane damage caused by ROS was more severe in the aged NT seeds than the aged CA seeds. The aged CA seeds decreased germination rates as compared to newly harvested transgenic and non-transgenic seeds. The aged CA seeds, however, significantly increased germination rates under various abiotic stress conditions as compared to aged NT seeds. These data strongly suggest that simultaneous over-expression of the CuZnSOD and APX genes in plastids improves seed longevity and germination under various environmental stress conditions by attenuating the effects of oxidative stress produced by elongated storage conditions and harsh environmental stresses
Transgenic Loblolly Pine Trees from Diverse Elite Families
Loblolly pine (Pinus taeda L.) has been the focus of genetic improvement for nearly 100 years because of the value of this species to the forestry industry. The application of gene transfer technology to loblolly pine improvement has been limited by the regeneration of transgenic tissue into plants. We have developed gene transfer systems that allow the regeneration of trees after the transformation of embryogenic cultures from a large number of genetically diverse families. Genetic transformation was achieved by biolistic and Agrobacterium-mediated techniques. Biolistic transformation efficiency was increased by identifying the optimal target using secondary somatic embryogenesis and by determining the long-term effects of tissue culture manipulations. Improvements to selection and the tissue culture system facilitated the production of stable transformants from 72% of the cell lines attempted from 15 elite families, with an escape rate of less than 1%. Molecular analysis of transgenic trees produced from biolistic transformation found that 36% of the trees had three inserts or less. Transgenic trees produced by biolistics have exhibited normal morphology for up to five growing seasons, to date. An Agrobacterium-mediated transformation system was developed for loblolly pine using tissue culture and selection procedures of the biolistic system. Agrobacterium tumefaciens has been used to produce transgenic trees of clones from elite loblolly families, as well as clones of P. radiata and P. taeda x rigida. Genomic blot analysis of Agrobacterium-transformed somatic embryos is ongoing. Field tests with Agrobacterium-transformed loblolly and the hybrid loblolly have been established each year since 2001. The efficiency of the Agrobacterium transformation system has made it possible for ArborGen to scale-up for high-throughput gene testing in a conifer. Transgenic trees have been produced with genes for lignin modification, accelerated growth, and flowering control.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003
One tissue, two fates: different roles of megagametophyte cells during Scots pine embryogenesis
In the Scots pine (Pinus sylvestris L.) seed, embryos grow and develop within the corrosion cavity of the megagametophyte, a maternally derived haploid tissue, which houses the majority of the storage reserves of the seed. In the present study, histochemical methods and quantification of the expression levels of the programmed cell death (PCD) and DNA repair processes related genes (MCA, TAT-D, RAD51, KU80, and LIG) were used to investigate the physiological events occurring in the megagametophyte tissue during embryo development. It was found that the megagametophyte was viable from the early phases of embryo development until the early germination of mature seeds. However, the megagametophyte cells in the narrow embryo surrounding region (ESR) were destroyed by cell death with morphologically necrotic features. Their cell wall, plasma membrane, and nuclear envelope broke down with the release of cell debris and nucleic acids into the corrosion cavity. The occurrence of necrotic-like cell death in gymnosperm embryogenesis provides a favourable model for the study of developmental cell death with necrotic-like morphology and suggests that the mechanism underlying necrotic cell death is evolutionary conserved
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