57 research outputs found
Drought drove forest decline and dune building in eastern upper Michigan, USA, as the upper Great Lakes became closed basins
Current models of landscape response to Holocene climate change in midcontinent North America largely reconcile Earth orbital and atmospheric climate forcing with pollen-based forest histories on the east and eolian chronologies in Great Plains grasslands on the west. However, thousands of sand dunes spread across 12,000 km2 in eastern upper Michigan (EUM), more than 500 km east of the present forest-prairie ecotone, present a challenge to such models. We use 65 optically stimulated luminescence (OSL) ages on quartz sand deposited in silt caps (n = 8) and dunes (n = 57) to document eolian activity in EUM. Dune building was widespread ca. 10–8 ka, indicating a sharp, sustained decline in forest cover during that period. This decline was roughly coincident with hydrologic closure of the upper Great Lakes, but temporally inconsistent with most pollen-based models that imply canopy closure throughout the Holocene. Early Holocene forest openings are rarely recognized in pollen sums from EUM because faint signatures of non-arboreal pollen are largely obscured by abundant and highly mobile pine pollen. Early Holocene spikes in nonarboreal pollen are recorded in cores from small ponds, but suggest only a modest extent of forest openings. OSL dating of dune emplacement provides a direct, spatially explicit archive of greatly diminished forest cover during a very dry climate in eastern midcontinent North America ca. 10–8 ka
Thermally activated resonant tunnelling in GaAs/AlGaAs triple barrier tunnelling structures
A thermally activated resonant tunnelling feature has been observed in the current-voltage characteristics (I(V)) of triple barrier resonant tunnelling structures (TBRTS) due to alignment of the n=1 confined states in the two quantum wells (QWs) within the active region. With rising sample temperature, the tunnelling current of the resonant feature increases in magnitude, showing a small negative differential resistance region which is discernable even at 293K. This behaviour is unique to multiple barrier devices and cannot be observed in conventional double barrier resonant tunnelling structures. Symmetric TBRTS, of nominal well widths 67Å and asymmetric QW, with decreasing second well widths, nominally 64Å to 46Å, have been studied with temperature dependent resonant tunnelling behaviour observed in both symmetric and asymmetric designs. Activation energies have been extracted from Arrhenius plots of the magnitude of the thermally activated peak current for each device design. This activation energy decreases as the second well width is decreased due to alignment occurring at increasingly greater bias and as such at energies closer to the Fermi level in the emitter region of the devices. Experimentally determined activation energies are in good agreement with theoretical values obtained by modelling the device I(V) characteristic
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A method for generating virus-free cassava plants to combat viral disease epidemics in Africa
Here, we report a method to clean cassava plants from viral infections that cause cassava mosaic and brown streak diseases in Africa. Infected plants of resistant or tolerant varieties from Malawi, Mozambique, Kenya, Tanzania and Uganda were cleaned in the UK using a combination of tissue culture, chemotherapy and thermotherapy. In the first cycle of our virus-indexing procedure, we successfully cleaned 27 of the 31 varieties (87%), and after an additional three cleaning cycles, all plants were virus-free. Virus-free tissue-cultured plants were shipped back to Africa for distribution to farmers. This first cross-boundary effort provides important lessons for mitigating the two-major cassava viral diseases
The Vehicle, 1964, Vol. 6
Vol. 6
Table of Contents
Milepostspage 2
John Fitzgerald Kennedy Memorial Pagepage 4
Sadness No. 4 (Sorgen)Sherry S. Frypage 5
Christian BurialRoger J. Barrypage 7
The World of BeautyDavid Helmpage 9
The Song of the LarksDon Kapraunpage 10
ContrastKeith Haierpage 13
PanoramaDaun Alan Leggpage 13
A Child\u27s View of DeathCherie Brondellpage 14
RegretLiz Puckettpage 16
Brutal WarMary H. Soukuppage 17
aloneLiz Puckettpage 18
MadgeLinda Galeypage 19
Moon WatchingJoel E. Hendrickspage 20
AnalysisLiz Puckettpage 21
UniverseRick Talleypage 21
Anyone Can Be A LuniticRick Towsonpage 22
I, Too, Have A Rendezvous with DeathElaine Lancepage 23
The ReturnRobert D. Thomaspage 24
NamesLarry Gatespage 25
Eternal MomentsDavid Helmpage 25
The Last DaysPauline B. Smithpage 26
BeliefRichard J. Wiesepage 27
StormPauline B. Smithpage 28
ExplosionLiz Puckettpage 29
Autumn EveJoel E. Hendrickspage 29
The Girl On the White PonyLarry Gatespage 31
HoffnungTerry Michael Salempage 33
Stone WallsDaun Alan Leggpage 34
AdorationGail M. Barenfangerpage 37
MirageRoy L. Carlsonpage 38
Nature and NonsenseRick Talleypage 39
A Step Through A Looking GlassMarilyn Henrypage 40
Thoughts of a Summer PastPauline B Smithpage 42
Indiana GrassLarry Gatespage 43
RedondillaRoberta Matthewspage 44
Summer LoveDaun Alan Leggpage 45
To Youth Reaching For MaturityDavid Helmpage 45
Thanksgiving DayJoel E. Hendrickspage 46
Sadness No. 6 (Schatten)Sherry S. Frypage 48https://thekeep.eiu.edu/vehicle/1012/thumbnail.jp
The process and lessons of exchanging and managing in-vitro elite germplasm to combat CBSD and CMD in Eastern and Southern Africa
Varieties with resistance to both cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) can reverse food and income security threats affecting the rural poor in Eastern and Southern Africa. The International Institute of Tropical Agriculture is leading a partnership of five national (Malawi, Mozambique, Kenya, Tanzania and Uganda) cassava breeding programs to exchange the most elite germplasm resistant to both CMD and CBSD. This poster documents the process and the key learning lessons. Twenty to 25 stem cuttings of 31 clones comprising of 25 elite clones (5 per country), two standard checks (Kibandameno from Kenya and Albert from Tanzania), and four national checks (Kiroba and Mkombozi from Tanzania, Mbundumali from Malawi, and Tomo from Mozambique) were cleaned and indexed for cassava viruses at both the Natural Resources Institute in the United Kingdom and Kenya Plant Health Inspectorate Services, in Kenya. About 75 in-vitro plantlets per clone were sent to Genetic Technologies International Limited, a private tissue culture lab in Kenya, and micro-propagated to ≥1500 plantlets. Formal procedures of material transfer between countries including agreements, import permission and phytosanitary certification were all ensured for germplasm exchange. At least 300 plantlets of each elite and standard check clones were sent to all partner countries, while the national checks were only sent to their respective countries of origin. In each country, the in-vitro plantlets were acclimatized under screen house conditions and transplanted for field multiplication as a basis for multi-site testing. Except for Tomo, a susceptible clone, all the clones were cleaned of the viruses. However, there was varied response to the cleaning process between clones, e.g. FN-19NL, NASE1 and Kibandameno responded slowly. Also, clones responded differently to micro-propagation protocols at GTIL, e.g. Pwani, Tajirika, NASE1, TME204 and Okhumelela responded slowly. Materials are currently being bulked at low disease pressure field sites in preparation for planting at 5-8 evaluation sites per country. The process of cleaning, tissue culture mass propagation, exchange and local hardening off/bulking has been successful for the majority of target varieties. Two key lessons derived from the process are that adequate preparations of infrastructure and trained personnel are required to manage the task, and that a small proportion of varieties are recalcitrant to tissue culture propagation
Autocrine Regulation of Pulmonary Inflammation by Effector T-Cell Derived IL-10 during Infection with Respiratory Syncytial Virus
Respiratory syncytial virus (RSV) infection is the leading viral cause of severe lower respiratory tract illness in young infants. Clinical studies have documented that certain polymorphisms in the gene encoding the regulatory cytokine IL-10 are associated with the development of severe bronchiolitis in RSV infected infants. Here, we examined the role of IL-10 in a murine model of primary RSV infection and found that high levels of IL-10 are produced in the respiratory tract by anti-viral effector T cells at the onset of the adaptive immune response. We demonstrated that the function of the effector T cell -derived IL-10 in vivo is to limit the excess pulmonary inflammation and thereby to maintain critical lung function. We further identify a novel mechanism by which effector T cell-derived IL-10 controls excess inflammation by feedback inhibition through engagement of the IL-10 receptor on the antiviral effector T cells. Our findings suggest a potentially critical role of effector T cell-derived IL-10 in controlling disease severity in clinical RSV infection
Chronic Diseases in North-West Tanzania and Southern Uganda. Public Perceptions of Terminologies, Aetiologies, Symptoms and Preferred Management
Research outputs produced to support a quantitative population survey, quantitative health facility survey, focus groups and in-depth interviews performed by the projec
Aqueous Dissolution of Alzheimer's Disease Ab Amyloid Deposits by Biometal Depletion
Zn(II) and Cu(II) precipitate Abeta in vitro into insoluble aggregates that are dissolved by metal chelators. We now report evidence that these biometals also mediate the deposition of Abeta amyloid in Alzheimer's disease, since the solubilization of Abeta from post-mortem brain tissue was significantly increased by the presence of chelators, EGTA, N,N,N',N'-tetrakis(2-pyridyl-methyl) ethylene diamine, and bathocuproine. Efficient extraction of Abeta also required Mg(II) and Ca(II). The chelators were more effective in extracting Abeta from Alzheimer's disease brain tissue than age-matched controls, suggesting that metal ions differentiate the chemical architecture of amyloid in Alzheimer's disease. Agents that specifically chelate copper and zinc ions but preserve Mg(II) and Ca(II) may be of therapeutic value in Alzheimer's disease
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