59 research outputs found
Impact of Grazing Management on the Productivity of Cold Temperate Grasslands of Southern Patagonia - A Critical Assessment
The contention that productivity of cold temperate grasslands of southern Patagonia have been greatly affected by domestic herbivore grazing in the past is fairly widespread. The consequences of spatiotemporal interactions between grazing and abiotic factors on the overall productivity of such systems, however, are still poorly understood. Predictions of both short- and long-term impacts of grazing management strategies on grassland productivity require a better understanding of these interactions. In this paper we make a critical assessment of the impact of grazing management on long-term sustainability of the grass steppes of southern Patagonia (Argentina). We discuss this issue in the context of current understanding of structure and function of these grass steppes, and of present-day global change concerns. We explore the capabilities of present-day tools to integrate biotic and abiotic factors at the landscape level to improve grazing management decisions
A generalization of Gabriel's Galois covering functors II: 2-categorical Cohen-Montgomery duality
Given a group , we define suitable 2-categorical structures on the class
of all small categories with -actions and on the class of all small
-graded categories, and prove that 2-categorical extensions of the orbit
category construction and of the smash product construction turn out to be
2-equivalences (2-quasi-inverses to each other), which extends the
Cohen-Montgomery duality.Comment: 31 pages. I moved the Sec of G-GrCat into Sec 3, and added Lem 5.6. I
added more explanations in the proof of Cor 7.6 with (7.5). I added Def 7.7
and Lem 7.8 with the necessary additional assumptions in Props 7.9 and 7.11.
I added Lem 8.8 with a short proof, Rmk 8.9 and the proof of Lem 8.10. The
final publication is available at Springer via
http://dx.doi.org/10.1007/s10485-015-9416-
Spin-Boson Hamiltonian and Optical Absorption of Molecular Dimers
An analysis of the eigenstates of a symmetry-broken spin-boson Hamiltonian is
performed by computing Bloch and Husimi projections. The eigenstate analysis is
combined with the calculation of absorption bands of asymmetric dimer
configurations constituted by monomers with nonidentical excitation energies
and optical transition matrix elements. Absorption bands with regular and
irregular fine structures are obtained and related to the transition from the
coexistence to a mixing of adiabatic branches in the spectrum. It is shown that
correlations between spin states allow for an interpolation between absorption
bands for different optical asymmetries.Comment: 15 pages, revTeX, 8 figures, accepted for publication in Phys. Rev.
Integrability and action operators in quantum Hamiltonian systems
For a (classically) integrable quantum mechanical system with two degrees of
freedom, the functional dependence of the
Hamiltonian operator on the action operators is analyzed and compared with the
corresponding functional relationship in
the classical limit of that system. The former is shown to converge toward the
latter in some asymptotic regime associated with the classical limit, but the
convergence is, in general, non-uniform. The existence of the function
in the integrable regime of a parametric
quantum system explains empirical results for the dimensionality of manifolds
in parameter space on which at least two levels are degenerate. The comparative
analysis is carried out for an integrable one-parameter two-spin model.
Additional results presented for the (integrable) circular billiard model
illuminate the same conclusions from a different angle.Comment: 9 page
Flow equations for Hamiltonians: Contrasting different approaches by using a numerically solvable model
To contrast different generators for flow equations for Hamiltonians and to
discuss the dependence of physical quantities on unitarily equivalent, but
effectively different initial Hamiltonians, a numerically solvable model is
considered which is structurally similar to impurity models. By this we discuss
the question of optimization for the first time. A general truncation scheme is
established that produces good results for the Hamiltonian flow as well as for
the operator flow. Nevertheless, it is also pointed out that a systematic and
feasible scheme for the operator flow on the operator level is missing. For
this, an explicit analysis of the operator flow is given for the first time. We
observe that truncation of the series of the observable flow after the linear
or bilinear terms does not yield satisfactory results for the entire parameter
regime as - especially close to resonances - even high orders of the exact
series expansion carry considerable weight.Comment: 25 pages, 10 figure
Small denominators, frequency operators, and Lie transforms for nearly integrable quantum spin systems
Based on the previously proposed notions of action operators and of quantum integrability, frequency operators are introduced in a fully quantum-mechanical setting. They are conceptually useful because another formulation can be given to unitary perturbation theory. When worked out for quantum spin systems, this variant is found to be formally equivalent to canonical perturbation theory applied to nearly integrable systems consisting of classical spins. In particular, it becomes possible to locate the quantum-mechanical operator-valued equivalent of the frequency denominators that may cause divergence of the classical perturbation series. The results that are established here link the concept of quantum-mechanical integrability to a technical question, namely, the behavior of specific perturbation series
Performance of LoRa-WAN Sensors for Precision Livestock Tracking and Biosensing Applications
This study investigated the integration of Long Range Wide Area Network (LoRa WAN) communication technology and sensors for use as Internet of Things (IoT) platform for Precision Livestock-Farming (PLF) applications. The research was conducted at New Mexico State University’s Clayton Livestock Research Centre. The functionality of LoRA WAN communication technology and performance of LoRa WAN motion and GPS sensors were tested using static sensors that were placed either, a) outdoors and at incremental distances from the LoRa WAN gateway antenna (Field, n=6), or b) housed indoors and close to the same LoRa WAN gateway antenna (Indoor, n=5). Accelerometer data, reported as motion intensity index, and GPS location were acquired, transmitted and logged at 1 and 15 minute intervals, respectively. We evaluated the tracker\u27s GPS accuracy (GPSBias as the euclidean distance between the actual and projected tracker location) and variables associated with the tracker’s data transmission capabilities. The results indicate that field trackers had a greater accuracy for remote sensing of GPS locations compared to indoor trackers facing increasing communication interference to acquire satellite signals (GPSBias; 5.20 vs. 17.76 m; P\u3c 0.01). Overall, the trackers and deployments appeared to have a comparable GPS accuracy to other tracking devices and systems available in the market. The total data packets that were successfully transmitted were similar between the indoor and field trackers, but the number of data packets that were processed varied between the two deployments (P=0.02). Due to the static deployment of indoor and field trackers, activity data was almost non-existent for most devices. However, same trackers embedded on collars that were mounted on mature cattle showed clear diurnal patterns consistent with time budgets exerted by grazing cattle. The pilot testing of GPS and accelerometer sensors using LoRa WAN technology revealed reasonable sensor sensitivity and reliability for integration in PLF platforms
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Linked hydrologic and social systems that support resilience of traditional irrigation communities
Southwestern US irrigated landscapes are facing
upheaval due to water scarcity and land use conversion associated
with climate change, population growth, and changing
economics. In the traditionally irrigated valleys of northern
New Mexico, these stresses, as well as instances of community
longevity in the face of these stresses, are apparent.
Human systems have interacted with hydrologic processes
over the last 400 years in river-fed irrigated valleys to create
linked systems. In this study, we ask if concurrent data from
multiple disciplines could show that human-adapted hydrologic
and socioeconomic systems have created conditions
for resilience. Various types of resiliencies are evident in
the communities. Traditional local knowledge about the hydrosocial
cycle of community water management and ability
to adopt new water management practices is a key response
to disturbances such as low water supply from drought. Livestock
producers have retained their irrigated land by adapting:
changing from sheep to cattle and securing income from
outside their livestock operations. Labor-intensive crops decreased
as off-farm employment opportunities became available.
Hydrologic resilience of the system can be affected by
both human and natural elements. We find, for example, that
there are multiple hydrologic benefits of traditional irrigation
system water seepage: it recharges the groundwater that
recharges rivers, supports threatened biodiversity by maintaining
riparian vegetation, and ameliorates impacts of climate
change by prolonging streamflow hydrographs. Human
decisions to transfer water out of agriculture or change irrigation
management, as well as natural changes such as long-term
drought or climate change, can result in reduced seepage
and the benefits it provides. We have worked with the
communities to translate the multidisciplinary dimensions of
these systems into a common language of causal loop diagrams,
which form the basis for modeling future scenarios to
identify thresholds and tipping points of sustainability. Early
indications are that these systems, though not immune to upheaval,
have astonishing resilience.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Copernicus Publications on behalf of the European Geosciences Union. The published article can be found at: http://www.hydrology-and-earth-system-sciences.net/home.html
Graded D-branes and skew-categories
I describe extended gradings of open topological field theories in two
dimensions in terms of skew categories, proving a result which alows one to
translate between the formalism of graded open 2d TFTs and equivariant cyclic
categories. As an application of this formalism, I describe the open 2d TFT of
graded D-branes in Landau-Ginzburg models in terms of an equivariant cyclic
structure on the triangulated category of `graded matrix factorizations'
introduced by Orlov. This leads to a specific conjecture for the Serre functor
on the latter, which generalizes results known from the minimal and Calabi-Yau
cases. I also give a description of the open 2d TFT of such models which
manifestly displays the full grading induced by the vector-axial R-symmetry
group.Comment: 37 page
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