18,480 research outputs found
Evaluation of remote sensing in control of pink bollworm in cotton
The author has identified the following significant results. This project is to identify and map cotton fields in the southern deserts of California. Cotton in the Imperial, Coachella, and Palo Verde Valleys is heavily infested by the pink bollworm which affects both the quantity and quality of cotton produced. In California the growing season of cotton is regulated by establishing planting and plowdown dates. These procedures ensure that the larvae, whose diapause or resting period occurs during the winter months, will have no plant material on which to feed, thus inhibiting spring moth emergence. the underflight data from the U-2 aircraft has shound that it is possible to detect the differences between a growing, a defoliated, and plowed down field providing the locations of the fields are known. The ERTS-1 MSS data are being analyzed using an I2S optical color combiner to determine which combinations of dates and colors will identify cotton fields and thus provide the data needed to produce maps of the fields for the forthcoming season
Evaluation of remote sensing in control of pink bollworm in cotton
The author has identified the following significant results. This investigation is to evaluate the use of a satellite in monitoring the cotton production regulation program of the State of California as an aid in controlling pink bollworm infestation in the southern deserts of California. Color combined images of ERTS-1 multispectral images simulating color infrared are being used for crop identification. The status of each field (crop, bare, harvested, wet, plowed) is mapped from the imagery and is then compared to ground survey information taken at the time of ERTS-1 overflights. A computer analysis has been performed to compare field and satellite data to a crop calendar. Correlation to date has been 97% for field condition. Actual crop identification varies; cotton identification is only 63% due to lack of full season coverage
Polio survivors’ perceptions of the meaning of quality of life and strategies used to promote participation in everyday activities
This article is made available through the Brunel Open Access Publishing Fund.Introduction: The term ‘post-polio syndrome’ (PPS) is used to describe new and late manifestations of poliomyelitis that occur later in life. Research in this area has focused upon health status rather than its effect on quality of life. Aim: To gain an in-depth understanding of the meaning of quality of life for polio survivors and to determine the type of strategies that are used by people with PPS and the support that they consider as important to facilitate participation in everyday life activities that have an impact on their quality of life. Method: Six focus groups were conducted with 51 participants from two regions in England. Data were audio-taped and analysed using thematic analysis. Results: Our research found that polio survivors used terms used to describe quality of life which could be associated with that of happiness. Our research has identified resolvable factors that influence quality of life namely inaccessible environments, attitudes of health-care professionals and societal attitudes. Polio survivors have tried alternative therapies, chiefly acupuncture and massage, and found them to be effective in enhancing their quality of life. Conclusion: It is suggested that health-care professionals should consider factors which influence happiness and implement a person-centred approach with the views of the polio survivor being listened to. The three factors that influenced quality of life could be resolved by health-care professionals and by society. With regard to strategies used, we suggest that polio survivors should have access to the treatments that they perceive as important, although further research is required to design optimal interventions for this client group
Atomic Model of Susy Hubbard Operators
We apply the recently proposed susy Hubbard operators to an atomic model. In
the limiting case of free spins, we derive exact results for the entropy which
are compared with a mean field + gaussian corrections description. We show how
these results can be extended to the case of charge fluctuations and calculate
exact results for the partition function, free energy and heat capacity of an
atomic model for some simple examples. Wavefunctions of possible states are
listed. We compare the accuracy of large N expansions of the susy spin
operators with those obtained using `Schwinger bosons' and `Abrikosov
pseudo-fermions'. For the atomic model, we compare results of slave boson,
slave fermion, and susy Hubbard operator approximations in the physically
interesting but uncontrolled limiting case of N->2. For a mixed representation
of spins we estimate the accuracy of large N expansions of the atomic model. In
the single box limit, we find that the lowest energy saddle-point solution
reduces to simply either slave bosons or slave fermions, while for higher boxes
this is not the case. The highest energy saddle-point solution has the
interesting feature that it admits a small region of a mixed representation,
which bears a superficial resemblance to that seen experimentally close to an
antiferromagnetic quantum critical point.Comment: 17 pages + 7 pages Appendices, 14 figures. Substantial revision
Nucleation at the DNA supercoiling transition
Twisting DNA under a constant applied force reveals a thermally activated
transition into a state with a supercoiled structure known as a plectoneme.
Using transition state theory, we predict the rate of this plectoneme
nucleation to be of order 10^4 Hz. We reconcile this with experiments that have
measured hopping rates of order 10 Hz by noting that the viscosity of the bead
used to manipulate the DNA limits the measured rate. We find that the intrinsic
bending caused by disorder in the base-pair sequence is important for
understanding the free energy barrier that governs the transition. Both
analytic and numerical methods are used in the calculations. We provide
extensive details on the numerical methods for simulating the elastic rod model
with and without disorder.Comment: 18 pages, 15 figure
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Continued evaluation of potential for geologic storage of carbon dioxide in the southeastern United States
Southern States Energy Board
Duke Energy
Santee Cooper Power
Southern CompanyBureau of Economic Geolog
Upper bound for the conductivity of nanotube networks
Films composed of nanotube networks have their conductivities regulated by
the junction resistances formed between tubes. Conductivity values are enhanced
by lower junction resistances but should reach a maximum that is limited by the
network morphology. By considering ideal ballistic-like contacts between
nanotubes we use the Kubo formalism to calculate the upper bound for the
conductivity of such films and show how it depends on the nanotube
concentration as well as on their aspect ratio. Highest measured conductivities
reported so far are approaching this limiting value, suggesting that further
progress lies with nanowires other than nanotubes.Comment: 3 pages, 1 figure. Minor changes. Accepted for publication in Applied
Physics Letter
Low-temperature thermopower study of YbRh2Si2
The heavy-fermion compound YbRh2Si2 exhibits an antiferromagnetic (AFM) phase
transition at an extremely low temperature of TN = 70 mK. Upon applying a tiny
magnetic field of Bc = 60 mT the AFM ordering is suppressed and the system is
driven toward a field-induced quantum critical point (QCP). Here, we present
low-temperature thermopower S(T) measurements of high-quality YbRh2Si2 single
crystals down to 30 mK. S(T) is found negative with comparably large values in
the paramagnetic state. In zero field no Landau-Fermi-liquid (LFL) like
behavior is observed within the magnetically ordered phase. However, a sign
change from negative to positive appears at lowest temperatures on the magnetic
side of the QCP. For higher fields B > Bc a linear extrapolation of S to zero
clearly evidences the recovery of LFL regime. The crossover temperature is
sharply determined and coincides perfectly with the one derived from
resistivity and specific heat investigations.Comment: LT25 conference proceedings in Journal of Physics: Conference Serie
Local Moments in an Interacting Environment
We discuss how local moment physics is modified by the presence of
interactions in the conduction sea. Interactions in the conduction sea are
shown to open up new symmetry channels for the exchange of spin with the
localized moment. We illustrate this conclusion in the strong-coupling limit by
carrying out a Schrieffer Wolff transformation for a local moment in an
interacting electron sea, and show that these corrections become very severe in
the approach to a Mott transition. As an example, we show how the Zhang Rice
reduction of a two-band model is modified by these new effects.Comment: Latex file with two postscript figures. Revised version, with more
fully detailed calculation
Vacuum Decay in Theories with Symmetry Breaking by Radiative Corrections
The standard bounce formalism for calculating the decay rate of a metastable
vacuum cannot be applied to theories in which the symmetry breaking is due to
radiative corrections, because in such theories the tree-level action has no
bounce solutions. In this paper I derive a modified formalism to deal with such
cases. As in the usual case, the bubble nucleation rate may be written in the
form . To leading approximation, is the bounce action obtained by
replacing the tree-level potential by the leading one-loop approximation to the
effective potential, in agreement with the generally adopted {\it ad hoc}
remedy. The next correction to (which is proportional to an inverse power
of a small coupling) is given in terms of the next-to-leading term in the
effective potential and the leading correction to the two-derivative term in
the effective action. The corrections beyond these (which may be included in
the prefactor) do not have simple expressions in terms of the effective
potential and the other functions in the effective action. In particular, the
scalar-loop terms which give an imaginary part to the effective potential do
not explicitly appear; the corresponding effects are included in a functional
determinant which gives a manifestly real result for the nucleation rate.Comment: 39 pages, CU-TP-57
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