243,447 research outputs found
Measurement of the mass difference m(D-s(+))-m(D+) at CDF II
No full textWe present a measurement of the mass difference m(D-s(+))-m(D+), where both the D-s(+) and D+ are reconstructed in the phipi(+) decay channel. This measurement uses 11.6 pb(-1) of data collected by CDF II using the new displaced-track trigger. The mass difference is found to be m(D-s(+))-m(D+)=99.41+/-0.38(stat)+/-0.21(syst) MeV/c(2)
The Greek islands and Turkey after the war.
No full textPreface: Field, H.MDedication: Roswell D. HitchcockContent description: TitleIllustration: (Maps ,portraits ,)Pagination: 228PVolumes: 1Text Genre:ProseIllustration: (χάρτες ,πορτραίτα ,
Delta Marsh Field Station Archive Annual Report, Volume 4, 1969
No full textThe University Field Station had another successful
season and fifteen research projects were undertaken during the summer.
They included:--popu1ation and productivity studies in algae and
emergent marsh species; nitrification processes in marsh soils; the
relationship between evapotranspiration in Phragmites and water table
fluctuations; ecological studies on benthic fauna; factors determining
mollusc distribution; population dynamics of Brook Sticklebacks;
comparative ecology of two species of Shiner; internal helminths of
two amphibian species; reproductive biology of Forster's Tern; territory
in the Yellow Warbler, seasonal energy balance in the muskrat; geomorphic,
sedimentological and stratigraphic investigations of the area between
Portage la Prairie and Lake Manitoba and groundwater studies in the
Delta area.
We had the pleasure of visits from a number of distinguished
scientists from various parts of the world. The Department of Anthropology
held a field course for one month and groups from Botany and Zoology stayed
at the Station for shorter periods of time.
The following staff, students and technicians spent all
or part of the summer at the Field Station:
FACULTY
J. M. Walker
G. G. C. Robinson
J. Wright
C. T. Shay
R. M. Green
GRADUATE STUDENTS
T.O. Acere (Zoology)
H. Bauer (Psychology)
D. Bernard (Zoology)
D. Brown (Botany)
L. H1ynka (Zoology)
M. Fenton (Earth Science)
D. Lutchman (Earth Sdence)
M. McNicholl (Zoology)
F. Phillips (Botany)
SUMMER ASSISTANTS
W. Dentry
L. Hendzel
T. Hochbaum
J. Leberdensky
P. Lemon
K. Machniak
R. Moyshenko
T. Sulymko
G. Vascatto
J. Yarysz
C.K. Yeung
The first project started in early April, and from then
until mid-September the accommodation was used for 265 resident-weeks
with 4,269 meals being served! There are two projects continuing
throughout the winter. Seminars
A weekly programme of seminars and films was held in June
July and August , and we were privileged to hear lectures from
Dr . L. Rudescu (Roumania), Dr . R. Nero (Manitoba Museum of Man and Nature),
Dr . R. Miller (Yale University) , Mr . L. Gray (Water Control and
Conservation , Department of Mines and Natural Resources), Dr . J. M. Walker
(Botany, University of Manitoba), Dr . E. S. Burch (Anthropology,
University of Manitoba), Dr. G. G. C. Robinson (Botany, University of
Manitoba), Dr . D. Schindler (Fisheries Research Board, Winnipeg), and
Dr . G. Brunskill (Fisheries Research Board, Winnipeg). We welcomed
the participation of members of the Delta Waterfowl Research Station at
these seminars and appreciated their invitation to attend the two-day
Seminar on "Spacing Mechanisms in Waterfowl" and their July and August
seminar series.
At the 3rd November Seminar fifteen research summaries
were presented, including reports from Mr . F. Austin and Mr. P. Ould,
graduate students in the Department of Zoology who carried out their work
at the Delta Waterfowl Research Station. The seminar attracted about
80 people, promoted discussion and is now well established as an important
part of the Field Station programme . Brief summaries of most of these
projects form the major part of this Annual Report.
Courses
Anthropology 76.662
A small Archaeological Field School led by Prof. C. T. Shay
of the Department of Anthropology was held during the month of July.
The class surveyed for archaeological sites in the area and spent two
weeks excavating a small campsite on the Bell Estate. The campsite,
located on a small beachridge, yielded stone artifacts and pottery dating
between 1300-1600 A. D. We would like to extend to Mr. P. Ward our
appreciation for permission to excavate this site and for helpful
assistance throughout the course.
Comparative Chordate Zoology 22.220 and Plant Kingdom 1.220
Dr . G. Ross and Dr. B. Young respectively spent useful
days at the Field Station with their students.
Introductory Ecology (Botany 1.336 and Zoology 22 . 334)
Three sections each of 3 1/2 days duration were organized
by Drs. J. Gee, J. M. Stewart. J. M. Walker and J. F. Wright, assisted
by Mr. D. Bernard. Two sections were held in Registration Week and one
the following weekend. During the course, the students were introduced to
a variety of habitats, sampling techniques and methods of assessing
environmental parameters, which give an insight into the structure and
functioning of ecosystems .
2 Plant Ecology 1.452
Drs. J. M. Stewart and J. M. Walker organized a weekend
course in Plant Ecology with emphasis upon ordination and sampling
techniques as an aid to plant community description.
Advanced Taxonomy 1.442
Dr. R. Longton conducted a weekend course during which
intensive collecting of critical groups from a range of habitats
was undertaken. The collections were for analysis later in the term.
Marsh Ecology 1.721
The Marsh Ecology course spent a weekend at the Station
with Drs. J. M. Stewart and J. M. Walker, and examined the plant
communities =rom the lakeshore to the forested ridge and from the
wet meadow to the marsh. Materials were collected for plant and soil
analysis, calorific determinations, etc.
Visitors
We had the pleasure of visits from members of a number
of other Universities and institutions: Dr. T. Pritchard (Nature
Conservancy, U.K.), Dr. D. Bellamy (Durham), Dr. L. Rudescu (Bucharest,
Rumania), Dr. K. Patalas (Freshwater Institute), Dr. Bilden (Macdonald
College), Dr. D. Pimlott (Toronto), Dr. G. Ross (Southern), the members
of the Board of Trustees of the North American Wildlife Foundation,
Dr. B. Kendrick (Waterloo), Miss V. Humphreys (National Museum, Ottawa)
Miss M. Dwyer (National Parks, Ottawa), Mr. E. Carp (International Wildlife
Research Bureau), Dr. A. Johnson (Hendrix College), the members of the
11th Delta Waterfowl Research Station Seminar, Dr. G. MacLachlan (McGill),
Dr. J. Burnett (Glasgow), Dr. H. Dale (Guelph).
Special Events
There were three events worthy of special mention. On
August 14th, Dr. H. H. Saunderson officially opened the new laboratories
at the Station, when we were happy to be joined by friends from the
University, Provincial Government and others. A tour of the facilities
and displays by graduate students helped to make the day a memorable
one.
The Biology Division Picnic in July was the occasion for
a gathering of more than eighty for a beach celebration which became
the merrier when driven indoors by rain.
Perhaps the marathon social event was a barbeque supper
for the 128 participants at the International Coregonid Conference on
August 27th, accompanied by suitable musical revelry.
3 Buildings
During the winter and spring two cottages were built
east of Mallard Lodge and Murrays Cottage was renovated . The transformation
of the latter was completed with the assistance of graduate students
armed with paint brushes and permitted the building to be used for the
Archaeology Field Course. The Bell House was converted into a laboratory
by Dr. Robinson and Dennis Brown. However, despite this increase in
facilities, the basement of the lodge was in constant use as a laboratory.
A site plan and survey was prepared during September to enable future
expansion to take place on an orderly basis.
I would like to express appreciation for the efforts the
Provincial Government made to acquire for the Field Station two housing
units from the Macdonald Airfield. These will be brought to Delta during
the winter and will provide the laboratory and living accommodation which
is essential if an expanding programme of research and teaching is to
be carried out at the Field Station.
General
We are grateful for the opportunities afforded to us to use
the Bell Estate for various projects and for the friendly co-operation
extended to us by the members of the Delta Waterfowl Research Station.
Thanks are also due to the Portage Country Club for allowing us to use
their property for study' purposes.
To all departments of the Provincial Government upon whose
jurisdiction we impinge, warm thanks are extended for their many
kindnesses.
I would like to thank all the staff for their help during
the season and look forward to an even more successful year in 1970
New techniques in astronomical spectroscopy for 8-m telescopes
No full textThe purpose of this thesis is to investigate new instrument technology to enhance the capabilities of 8-m telescopes. This thesis first describes the theory, design, construction, and testing of an immersed grating. Immersed gratings can be used to provide R≥ 10(^4) with a multi-object and/or integral field spectrograph on an 8-m telescope. Immersed gratings allow high resolution to be achieved whilst maintaining the required pupil size at a level similar to that on 4-m telescopes. This thesis describes laboratory tests which verify that immersed gratings provide high resolution. The throughput penalty in using an immersed grating is shown to be small with losses due to air-glass reflections, which can be eliminated with antireflection coatings, and metal-dielectric losses. This work demonstrates that immersed gratings provide a good method to reach R=10(^4) (and above) with a multi-aperture spectrograph on an 8-m telescope. The second part of this thesis describes the construction of a microlens-fibre based integral field unit (IFU): the SMIRFS-IFU. This instrument provides a unique J and H-band integral field capability for use with the CGS4 spectrograph at UKIRT. The optical design, assembly, laboratory testing, and telescope commissioning of the SMIRFS-IFU are described. The microlens arrays for use with SMIRFS-IFU were tested in detail and found to provide excellent image quality but with some scattered light. The assembly of the SMIRFS-IFU was achieved with high precision. The overall performance of the SMIRFS-IFU was found to be high and close to theoretical expectations. This instrument demonstrates that the technology of microlenses linked to fibres does provide a means of constructing high performance (i.e. high throughput, high spatial and spectral resolution) IFUs. Integral field spectroscopy is even more important for 8-m telescopes to take advantage of their enormous fight gathering power. The SMIRFS-IFU is an important upgrade to CGS4 to perform high spatial resolution integral field spectroscopy
EXPLAINING PATTERNS OF DOMINANCE IN OLD-FIELD COMMUNITIES: TRADE-OFFS, FEEDBACKS, MUTUALISMS AND ENEMIES
No full textAlthough one of the oldest observations within ecology is that within communities there are few common species with many uncommon and rare species, the mechanisms that shape this relationship remain elusive. The primary explanations for repeated dominance in plant communities lie in competition theory, which predicts specific allocation to resource acquisition, low resource tolerance, colonization, and herbivore tolerance and resistance. Alternatively, soil
community feedback theory predicts positive plant-soil feedbacks to alter competitive dynamics and lead to dominance. Finally, specific mutualistic clades of the soil community, such as mycorrhizal fungi, may increase resource acquisition or herbivore tolerance, thus promoting positive feedback. To address these mechanisms that contribute to relative abundance and dominance, I used a light limited, old-field model system. Although these systems are relatively diverse, there is a striking pattern of repeated dominance by Solidago canadensis. By using a series of greenhouse and manipulative, long-term in situ experiments, I found no “smoking gun” mechanism to explain the dominance of So. canadensis, but rather an entire suite of processes
that likely contribute to relative abundance and the maintenance of diversity. I found no evidence of life history trade-offs across old-field species, with S. canadensis consistently violating long-standing theory by being the best light competitor, most shade tolerant, most
herbivore resistant, most herbivore tolerant, and among the fastest growing species. Looking belowground, I found that old-field plant species, even coexisting congeneric species, culture significantly different soil microbial communities, which altered plant performance, changed the
intensity of interspecific competition and reversed whether plant species were limited by conspecifics or heterospecifics. Although this mosaic of shifting competitive abilities due to soil feedbacks is predicted to maintain diversity, the ability of S. canadensis to grow well in its own and competitor soil communities may foster S. canadensis invasion and subsequent defense of territory. Finally, mycorrhizal fungi increased herbivore tolerance across old-field species, while having little or negative effects on plants in the absence of herbivory. This process may promote diversity within old-fields, but offers insight into how So. canadensis maintain dominance in the face of dozens of specialist herbivores
The field of entrepreneurship research: Some significant developments
No full textThis chapter discusses significant developments in the field of entrepreneurship research. These include, but are not limited to: \ud
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- (a) considerable growth in volume, quality, and theory-drivenness; \ud
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- (b) a drift of the main emphasis from small scale and independent ownership towards newness and novelty realized through a multitude of organizational solutions; \ud
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- (c) interest in multiple aspects of the entrepreneurial individual beyond personality; \ud
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- (d) moving beyond the individuals towards teams, networks and social capital; \ud
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- (e) viewing entrepreneurship as a multi-level phenomenon, with increased emphasis on outcomes beyond the individual- and firm-level financial result; \ud
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- (f) realizing the heterogeneous, context-dependent and process nature of entrepreneurial practice, along with the challenges to generalizability and research design that follow from this. \ud
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These developments, including the increased focus on theory and theoretical contributions, have served the field well. This said, the author argues that we are now at a juncture where recognizing a broader set of types of scholarly contributions would be even more beneficial
Assessing late-time singular behaviour in symmetry-plane models of 3D Euler flow
No full textMotivated by work on stagnation-point type exact solutions of the 3D Euler fluid equations by Gibbon [Gibbon et. al. Phys. D, 132, 497, (1999)] and the subsequent demonstration of finite-time blowup by Constantin [Constantin, Math. Res. Notices, 9, 455, (2000)] we introduce a one-parameter family of models of the 3D Euler equations on a 2D symmetry plane. These models provide a collection of blow-up scenarios which admit analytical solutions and are computationally inexpensive in comparison to the full 3D Euler equations. We take advantage of these features to examine the efficacy of novel methods which aid the assessment of finite-time blow-up in numerical simulations. The principal of these is the mapping to regular systems [Bustamante, Phys. D, 240, 1092, (2011)]; a bijective nonlinear mapping of time and the prognostic variables based on a Beale-Kato-Majda (BKM) type supremum norm regularity condition [Beale et. al. Commun. Math. Phys. 94, 61, (1984)]. We show a 3 order of magnitude increase of accuracy of the singularity time when employing the mapping with negligible additional computational expense. An investigation of the spectra of the primary field (vortex stretching rate) allows us to confirm a power law decrement of the analyticity-strip width with time in agreement with rigorous bounds bridging between the global spatial behaviour and BKM theorems [Bustamante & Brachet, Phys. Rev. E. 86, (2012)]
Cowpox virus infection in natural field vole Microtus agrestispopulations: significant negative impacts on survival
No full text1. Cowpox virus is an endemic virus circulating in populations of wild rodents. It has been implicated as a potential cause of population cycles in field voles Microtus agrestis L., in Britain, owing to a delayed density-dependent pattern in prevalence, but its impact on field vole demographic parameters is unknown. This study tests the hypothesis that wild field voles infected with cowpox virus have a lower probability of survival than uninfected individuals. 2. The effect of cowpox virus infection on the probability of an individual surviving to the next month was investigated using longitudinal data collected over 2 years from four grassland sites in Kielder Forest, UK. This effect was also investigated at the population level, by examining whether infection prevalence explained temporal variation in survival rates, once other factors influencing survival had been controlled for. 3. Individuals with a probability of infection, P(I), of 1 at a time when base survival rate was at median levels had a 22.4% lower estimated probability of survival than uninfected individuals, whereas those with a P(I) of 0.5 had a 10.4% lower survival. 4. At the population level, survival rates also decreased with increasing cowpox prevalence, with lower survival rates in months of higher cowpox prevalence. 5. Simple matrix projection models with 28 day time steps and two stages, with 71% of voles experiencing cowpox infection in their second month of life (the average observed seroprevalence at the end of the breeding season) predict a reduction in 28-day population growth rate during the breeding season from λ = 1.62 to 1.53 for populations with no cowpox infection compared with infected populations. 6. This negative correlation between cowpox virus infection and field vole survival, with its potentially significant effect on population growth rate, is the first for an endemic pathogen in a cyclic population of wild rodents
Transmit field pattern control for high field magnetic resonance imaging with integrated RF current sources
No full textThe primary design criterion for RF transmit coils for MRI is uniform transverse magnetic (B1) field. Currently, most high frequency transmit coils are designed as periodic, symmetric structures that are resonant at the imaging frequency, as determined by the static magnetic (B0) field strength. These coils are excited by one or more voltage sources. The distribution of currents on the coil elements or rungs is determined by the symmetry of the coil structure. At field strengths of 3T and above, electric properties such as the dielectric constant and conductivity of the load lead to B1 field inhomogeneity due to wavelength effects and perturbation of the coil current distribution from the ideal. The B1 field homogeneity under such conditions may be optimized by adjusting the amplitudes and phases of the currents on the rungs. However, such adjustments require independent control of current amplitudes and phases on each rung of the resonant coil. Due to both the strong coupling among the rungs of a resonant coil and the sensitivity to loading, such independent control would not be possible and B1 homogeneity optimization would involve a time consuming and impractical iterative procedure in the absence of exact knowledge of interactions among coil elements and between the coil and load.
This dissertation is based on the work done towards the design and development of a RF current source that drives high amplitude RF current through an integrated array element. The arrangement is referred to as a current element. Independent control of current amplitude and phase on the current elements is demonstrated. A non-resonant coil structure consisting of current elements is implemented and B1 field pattern control is demonstrated. It is therefore demonstrated that this technology would enable effective B1 field optimization in the presence of lossy dielectric loads at high field strengths
Toward the first D-band Point to multipoint wireless system field test
No full textThe European Commission Horizon 2020 ULTRAWAVE "Ultra capacity wireless layer beyond 100 GHz based on millimeter waves" is in the final stage of development. The first ever field test of a D-band point to multipoint wireless system will be performed in a real environment. The ULTRAWAVE wireless system comprises a D-band Transmission Hub to produce a 30 degree sector with 600 m radius with multi gigabit per second data rate and a number of compact D-band terminals. The terminals will be distributed at different distances from the transmission hub to recreate real deployment condition. The paper describes the latest update on the development of the ULTRAWAVE systems and the field test set up
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