197,860 research outputs found
The nonisentropic perturbation of a centered magnetohydrodynamic simple wave
No full textAbstractAfter linearization of the governing equations of the one-dimensional nonsteady motion of an ideal, inviscid, perfectly conducting monatomic compressible fluid, subjected to a transverse magnetic field, in the neighborhood of a centered simple wave flow, weakly nonisentropic perturbations are considered, and the solution for the first order terms given by quadratures. The results are a generalization of the work of Germain and Gundersen [2]
Factors controlling bacterial abundance, biomass and growth at the Bermuda Atlantic time-series site
No full textThe Bermuda Atlantic Time-series Study (BATS) site represents a unique hydrographical oceanic environment to study the factors controlling bacterial growth dynamics. The region was sampled at monthly intervals from 1991 to 1996. A typical annual cycle was defined by a deep winter mixing, followed by an increasing stratification of the mixed layer through summer and fall. There were striking seasonal patterns in phytoplankton productivity with a strong maximum immediately following the deep winter mixing and the intrusion of inorganic nutrients. Bacterial growth rates showed a similar pattern but had a secondary peak in late summer/fall of the same magnitude as the spring bloom. Bacterial abundance showed only slightly elevated concentrations in spring. A number of time course storage experiments showed that bacterial abundance decreased by 24-50 % within 7-29 days in samples preserved with 2.5 % glutaraldehyde. By adding a protease inhibitor prior to the addition of glutaraldehyde, the loss of bacterial cells was reduced to 17-18 % over a 30 day period. These findings lead to the recommendation that samples for bacterial abundance should be processed immediately for epifluorescence enumeration. An average of 47 % of all bacterial cells passed the pore size of a Whatman GF/F filter and these viable cells should be included in biomass estimates. An annual average of 26 % of estimated C settled below the spigot of a Niskin water sampler. Consequently, C measurements made on GF/F filters must account for the particles settling below the spigot of a water sampler as well as the number of bacteria lost during the process of filtration. This study is the first to present single cell elemental C, N and P measurements from natural bacteria in the Sargasso Sea. A wide range in elemental content was found between single cells and this could be expressed as a function of the cell size. By applying an average cell volume, an annual average of 10 fg C, 1.9 fg N and 0.28 fg P was calculated per bacterial cell.The average percentage integrated stocks of C in the upper 250 m of the water column, was 20 (phytoplankton), 18 (microheterotrophs) and 62 (other non-living detrital matter). Bacterial biomass was higher than phytoplankton outside the spring bloom period, but non-living carbon showed an overall dominance through out the year. Phytoplankton generation time was relatively constant over the season. Bacterial generation time was ten times longer and showed a greater seasonal variation, but largely followed the changes in primary production. Assuming that 50-70 % of the bacterial cells were non-living, the mean bacterial generation time was estimated to be 7 times (0-60 m) and 1.4 times (80-140m) longer than phytoplankton generation time. During the spring bloom event, an average of 85 % of the bacterial growth rate was removed by grazing and viral lysis. This was the only noted decoupling between growth and removal of bacteria at BATS. During the remainder of the year bacterial growth was balanced by the loss rate, due to grazing and viral lysis. A linear relationship was found between net DOC accumulation and primary production in natural surface waters at BATS. Phytoplankton net DOC excretion constituted 42 % of the primary production rate, while Trichodesmium colonies only excreted 12 % (puffs) and 23 % (tufts). By using a conservative estimate of the bacterial growth efficiency (14 %) and the net DOC accumulation rate from this study, gross DOC excretion was equivalent to the rate of primary particulate C production. Results from this study suggests that bacteria at the BATS siteare using the majority of the DOC generated by primary production. Prior to the spring bloom and the associated increase in DOC excretion, bacteria appeared to be C limited in the surface waters at BATS. Following the peak in primary production and coinciding with the depletion of inorganic nutrients in the euphotic zone, the bacterial cells became less C starved, but never reached a true N or P limitation. Regenerated nutrients from grazing and viral lysis of bacteria and new production by diazotrophic Trichodesmium colonies and trichomes, may support the bacteria with N and P in the euphotic zone in summer and fall. The substrate dependent growth and increase in biomass of bacteria exhibited at BATS in spring, is indicative of a bottom-up controlled system, whereas the bacteria appeared to be top down controlled by grazing and viral lysis for the remainder of the year
Early construction of Engineering (Gundersen Hall), circa 1911-1912
No full textEast facing facade of Engineering (Gundersen Hall) Building under construction on OAMC Campus, circa 1911-1912.Robert E. Cunningham (1906-1991) graduated from Oklahoma A&M College in 1932. Besides being a writer, Cunningham was a local photographer of Stillwater and a collector of glass plates. This collection of glass plate negatives and acetate base photographs held at the Oklahoma State University (OSU) Library Archives represents a portion of his collection amassed over the years. This memorabilia collection is historically significant in that it depicts the early history of OSU (A&M College), local history, and portraits of early residents of Stillwater. The digitization and documentation of this collection was made possible by an 2018-2019 Improving Access to Collections Grant sponsored by the Oklahoma Historical Records Advisory Board, administered by the Oklahoma Department of Libraries, and funded by the National Archives--National Historical Publications and Records Commission
Late construction of Engineering (Gundersen Hall), circa 1912
No full textEast facing facade of Engineering (Gundersen Hall) Building under construction, circa 1912 on OAMC campus.Robert E. Cunningham (1906-1991) graduated from Oklahoma A&M College in 1932. Besides being a writer, Cunningham was a local photographer of Stillwater and a collector of glass plates. This collection of glass plate negatives and acetate base photographs held at the Oklahoma State University (OSU) Library Archives represents a portion of his collection amassed over the years. This memorabilia collection is historically significant in that it depicts the early history of OSU (A&M College), local history, and portraits of early residents of Stillwater. The digitization and documentation of this collection was made possible by an 2018-2019 Improving Access to Collections Grant sponsored by the Oklahoma Historical Records Advisory Board, administered by the Oklahoma Department of Libraries, and funded by the National Archives--National Historical Publications and Records Commission
Personal Reflections on the Life of Hans Jørgen Gottlieb Gundersen
No full textProfessor Hans Jørgen G. Gundersen MD, DMSc (1943–2021) was a pioneering stereologist whose work has inspired and influenced researchers across the world for almost half a century. He was a charismatic character and one of the founding fathers of modern stereology, whose achievements and contributions are fondly remembered below by colleagues and co-workers. It was an enormous pleasure to be in his company and although future generation will miss this opportunity, his work will live on, to inspire and influence future generations of researchers
Detection of multiple phytoplasmas in perennial fruit trees with decline symptoms in Italy
No full textNested polymerase chain reaction assays with two universal and four phytoplasma (formerly called mycoplasmalike organism) 16S rRNA group-specific primer pairs were employed to investigate etiologies of diseases associated with pear (decline), plum (leptonecrosis), nectarine (chlorotic leaf roll), and apricot (chlorotic leaf roll and decline) fruit crops grown in northern Italy. Restriction fragment length polymorphism analyses of phytoplasma 16S rDNA sequences amplified with various combinations of these primer pairs revealed that two to four distinct types of phytoplasmas affiliated with phytoplasma 16S rRNA group I taster yellows phytoplasma and related strains), group III (peach X-disease and related phytoplasmas), group V (elm yellows phytoplasma and related strains), and group X (apple proliferation and related phytoplasmas) were associated with most diseases. Predominant phytoplasma strains associated with pear decline, apricot chlorotic leaf roll, and plum leptonecrosis were identified as members of group X (subgroups A and B). Phytoplasma strains associated with nectarine chlorotic leaf roll were members of group I. Minor phytoplasma strains (one or more distinct types) were also detected in each infected plant, except for those affected by apricot decline
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Phytoplasma: Ecology and genomic diversity
No full textThe recent development of molecular-based probes such as mono- and polyclonal antibodies, cloned phytoplasma DNA fragments, and phytoplasma-specific primers for polymerase chain reaction (PCR) has allowed for advances in detection and identification of uncultured phytoplasmas (formerly called mycoplasma-like organisms). Comprehensive phylogenetic studies based on analysis of 16S ribosomal RNA (rRNA) or both 16S rRNA and ribosomal protein gene operon sequences established the phylogenetic position of phytoplasmas as members of the class Mollicutes, and the revealed phylogenetic interrelationships among phytoplasmas formed a basis for their classification. Based on restriction fragment length polymorphism (RFLP) analysis of PCR-amplified 16S rRNA gene sequences, phytoplasmas are currently classified into 14 groups and 38 subgroups that are consistent with groups delineated based on phylogenetic analysis using parsimony of 16S rRNA gene sequences. In the past decades, numerous phytoplasma strains associated with plants and insect vectors have been identified using molecular-based tools. Genomic diversity of phytoplasma groups appears to be correlated with their sharing common insect vectors, host plants, or both in nature. The level of exchange of genetic information among phytoplasma strains in a given group is determined by three-way, vector-phytoplasma-plant interactions. A putative mechanism for the creation of new ecological niches and the evolution of new ecospecies is proposed
Fordeling av gjess og jaktorganisering i Nord-Trøndelag om høsten
No full textTombre, I. M., Gundersen. O. M. & T. Reinsborg. 2016. Fordeling av gjess og jaktorganisering i Nord-Trøndelag om høsten. – NINA Rapport 1272. 33 s.
Arealbruk hos kortnebbgås (Anser brachyrhynchus) og grågås (Anser anser) ble høsten 2014 og 2015 registrert i kommunene Levanger, Verdal, Steinkjer og Inderøy i Nord-Trøndelag fylke. Noen registreringer er også gjennomført i Overhalla kommune. Flest gjess, både av kortnebbgås og grågås, er det i Levanger kommune, etterfulgt av Steinkjer og Verdal. Inderøy og Overhalla har sporadisk mindre flokker med gjess. Det er flest gjess i større områder som er tilrettelagt for gåsejakt av flere samarbeidende grunneiere. Gåsejakten er her organisert på en måte som samlet sett gir mindre forstyrrelser for gjessene, da det til enhver tid er områder det ikke jaktes i og som følgelig fungerer som friområder for gjessene. I Nord-Trøndelag finnes slike grunneierorganiserte jaktområder i Egge i Steinkjer kommune, og på Nesset og i Skogn /Ronglan området i Levanger. Det er vanskelig å skille om mange gjess er i jaktorganiserte områder fordi jakten lettere kan administreres i områder med mye gjess eller om det er mye gjess i slike områder fordi her til enhver tid er friarealer som gir gjessene ro. Mest sannsynlig er det en kombinasjon av de to mulige forklaringene.
Større jaktorganiserte områder letter en løpende fellingsrapportering da slike tilrettelegginger har kontroll på fellingstallene forløpende. Det er en fordel med tanke på forvaltningen av kortnebbgås at kunnskap om fortløpende fellingstall er nødvendig for å følge de kvoter som Norge til enhver tid har til rådighet under den internasjonale forvaltnings-planen. I denne planen er det satt et bestandsmål som Norge må forholde seg til, og selv om bestanden i dag er over dette nivået er jaktuttaket økende og det forventes at bestanden etterhvert vil nå dette nivået.Tombre, I. M., Gundersen. O. M. & T. Reinsborg. 2016. Fordeling av gjess og jaktorganisering i Nord-Trøndelag om høsten. – NINA Rapport 1272. 33 s.
Autumn registrations of pink-footed geese (Anser brachyrhynchus) and greylag geese (Anser anser) were conducted in the county of Nord-Trøndelag, Norway, in 2014 and 2015. The municipalities covered were Levanger, Verdal, Steinkjer and Inderøy. There were also some registrations in the municipality of Overhalla. Levanger had the largest numbers of geese, regardless of species, followed by Steinkjer and Verdal. In Inderøy and Overhalla, smaller flocks were registered sporadically. Larger areas where several landowners have organised a common goose hunting arrangement were shown to have the highest numbers of geese. The hunting in such areas are organised in a way that always leave some fields protected from hunting, hence being a refuge area for the geese. In Nord-Trøndelag, such arrangements can be found in Egge in the municipality of Steinkjer, and at Nesset and in Skogn/Rongland in Levanger municipality. It is difficult to assess whether there are many geese in these areas because the threshold for organising the goose hunting is lower in areas with more geese, or due the possibility that more geese are attracted to these areas since there will always be a safe harbour under such arrangements. Probably, it is a combination of the two. In larger areas of organised hunting, there is usually a reporting system providing an up-to-date overview of the bag. Hence, such arrangements are advantageous when it comes to international obligations. In the international management plan for pink-footed geese, running harvest data will be necessary when the number of geese in the population reaches the target set for the population. At this target, Norway will have a quota system reflecting the total bag shared with Denmark. Although the current population level of pink-footed goose is above this target, an increasing harvest rate in both countries are currently causing a decline in the population.© Norsk institutt for naturforskning. Publikasjonen kan siteres fritt med kildeangivelse
Bosetningsspor. Bergsalleen 8A, Berg, 48/331, Oslo kommune.
No full textHøsten 2014 ble det foretatt utgravninger på Bergsalleen 8a i Oslo, hvor Byantikvaren i 2013 hadde påvist en mulig fotgrøft og sentralgrav. De påfølgende utgravningene viste at grøfta snarere var en dreneringsgrøft, som hadde omkranset et langhus. Huset har hatt en buet gavl i nordøst og to rette langsider mot sørvest, men har en uklar avslutning mot sørvest. Huset har en dokumentert bredde på 5,7 meter og en lengde på minst 7,5 meter. Funn av tre stolpehull indikerer at huset var stolpebygd. Det har ikke vært mulig å avklare hvorvidt huset har vært to- eller treskipet. En rekke funn av brent leire med avtrykk av kvist og/eller strå indikerer at huset har flettverks- og leirkliningsvegger. En rekke keramikkskår av en rødbrent, enkel og grovmagret type indikerer at huset er fra elder jernalder. Dette bekreftes av de radiologiske dateringene, som plasserer husets brukstid innenfor de midtre og yngre delene av førromersk jernalder (ca. 300 f.Kr.-Kr.f.). Det ble tatt ut ni kullprøver og sju makrofossilprøver i forbindelse med undersøkelsen. Seks kullprøver er vedartsbestemt av Karen Salvig, Moesgård museum, og fem datert ved Ångströmlaboratoriet, Uppsala universitet. Seks makrofossilprøver ble sendt til paleobotaniske analyser på Miljöarkeologiska laboratoriet, Umeå universitet. Analysen er utført av Sofi Östman.
Prosjektleder: Ingar M. Gundersen
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