2,258 research outputs found
Phenomenology of The Left-Right Twin Higgs Model
The twin Higgs mechanism has recently been proposed to solve the little
hierarchy problem. We study the implementation of the twin Higgs mechanism in
left-right models. At TeV scale, heavy quark and gauge bosons appear, with rich
collider phenomenology. In addition, there are extra Higgses, some of which
couple to both the Standard Model fermion sector and the gauge sector, while
others couple to the gauge bosons only. We present the particle spectrum, and
study the general features of the collider phenomenology of this class of model
at the Large Hadron Collider.Comment: 41 pages, version appears in PR
A Taxon-Free, Multi-Proxy Model for Making Paleoecological Interpretations of Neogene North American Faunas
Proxies used for interpreting the paleoecology of extinct vertebrate communities are usually based on modern ecosystems, with many developed from Old World ecosystems. However, because no model is completely taxon-free and phylogenetic influences cannot be entirely discounted, these proxies may not be appropriate for paleoecological interpretations of North American ecosystems. Additionally, many proxies based on modern vertebrate communities exclude small-bodied mammals. Here I explore several new paleoecological models based on the frequency of mammalian traits within three ecological categories: locomotion, diet, and body mass. Since these models are intended for interpreting paleoenvironments occupied by Neogene North American mammals, the data used to develop the models are from historical North American faunas. Pre-existing datasets were augmented with locomotion, diet, and body mass information from a variety of sources. Mammalian geographic occurrences were assigned to digital maps of Bailey’s Ecoregions of North America in ESRI ArcMap and ecoregions were combined into broader biomes in an iterative process using preliminary Principle Component Analysis (PCA). Taxa were sorted by biome and two datasets were created, one where the number of individual occurrences were used to weight traits, and one where only a single taxonomic occurrence was used for each biome. Taxonomic analyses were conducted on unweighted taxa both with and without rodents and lagomorphs. PCA was conducted using frequencies of trait classifications per biome for all datasets. Stacked area charts were created to visualize changing trait frequencies among biomes.
PCA analyses using unweighted data without the smallest mammals (\u3c500 \u3eg) provides the strongest separation of biomes. High frequencies of grazer, cursorial, and size class G traits (\u3c10500 \u3eg) are correlated traits in the grassland biome. Size classes C (500-1000 g) and D (1000 – 1500 g) are the second group of correlated traits, plotting in the opposite direction in grassland. High frequencies of arboreal/scansorial, omnivore, and granivore traits make up key indicators for the forest biome. Weighted datasets without small-bodied mammals (\u3c500 \u3eg) work well to distinguish among biomes. I conclude that unweighted analyses excluding small-bodied mammals should provide the best separation of biomes and be most appropriate for certain paleoecological applications in North America.
Advisor: Ross Secor
Design and Modeling of an Advance CMOS Process
An advanced ten level five micron CMOS process was designed. The process was modeled using SUPREM II software to calculate doping profiles, junction depths, and threshold voltages
A Large International River: The Danube. Summary of Hydrological Conditions and Water Management Problems in the Danube Basin
The demand of policy makers and managers to find environmentally sound and sustainable economic development is obvious. At the same time, various branches of sciences dealing with environmental issues have become more and more specialized. The solution to problems -- often of a global character -- requires the interdisciplinary analysis of versatile systems consisting of natural, economic and social elements of the environment.
Within the long series of water related topics of IIASA's Environment Program, a new project "Decision Support Systems for Managing Large International Rivers" (LIR) was recently launched. The formulation of environmentally sound management policy for land-use and water resources development requires the reliable prediction of the impacts of different human interventions in order to eliminate conflicts between different interest groups, and to preserve the quality of life in both the biosphere and society. Several models for the assessment of various environmental impacts already exist, but the large scale of river basins and the amount of data -- the availability of which is even limited in some cases -- require the development of aggregated systems of models that can provide decision makers with easily understandable information at various hierarchical levels. Considering this requirement, the objective of the project is to construct a computer-based interactive data and information system to facilitate the effective participation of policy making authorities in determining current conditions and expected changes in hydrological systems.
The outline of LIR emphasizes the importance of the preparation of case studies. Their role is not only to check the applicability on the system for solving actually occurring problems, but the analysis of the basins as cases will assist in selecting the crucial questions that should be answered by the Decision Support System. The Danube basin was chosen as the first case study to be investigated in the framework of LIR. The reason for this choice is partly that IIASA is located in the basin, and, thus all information easily accessible. The international character of the river (there are 8 riparian countries and 3 others sharing a small part of the catchment), the rapidly developing problems of the utilization of water (canalization, increasing transboundary pollution, seasonal water shortage), and the efforts of the riparian countries to improve the conditions of water resources development within the basin (which is clearly indicated by the fact that a joint declaration was signed) are also reasons supporting the selection of the Danube as the first case study.
Naturally, the hydrological conditions of the river system and the water management problems occurring within the catchment are well known for the experts in water sciences working in the riparian countries. For experts participating in the project and coming from other countries, or, representing other scientific disciplines, it is necessary, however, to summarize the most important information describing the water regime of the river system and the obstacles hindering the development of water resources in the basin. This working paper and the detailed list of references provide more information on water management in the Danube basin
New model of calculating the energy transfer efficiency for the spherical theta-pinch device
Ion-beam-plasma-interaction plays an important role in the field of Warm
Dense Matter (WDM) and Inertial Confinement Fusion (ICF). A spherical theta
pinch is proposed to act as a plasma target in various applications including a
plasma stripper cell. One key parameter for such applications is the free
electron density. A linear dependency of this density to the amount of energy
transferred into the plasma from an energy storage was found by C. Teske. Since
the amount of stored energy is known, the energy transfer efficiency is a
reliable parameter for the design of a spherical theta pinch device. The
traditional two models of energy transfer efficiency are based on assumptions
which comprise the risk of systematical errors. To obtain precise results, this
paper proposes a new model without the necessity of any assumption to calculate
the energy transfer efficiency for an inductively coupled plasma device.
Further, a comparison of these three different models is given at a fixed
operation voltage for the full range of working gas pressures. Due to the
inappropriate assumptions included in the traditional models, one owns a
tendency to overestimate the energy transfer efficiency whereas the other leads
to an underestimation. Applying our new model to a wide spread set of operation
voltages and gas pressures, an overall picture of the energy transfer
efficiency results
Hot Spine Loops and the Nature of a Late-Phase Solar Flare
The fan-spine magnetic topology is believed to be responsible for many
curious features in solar explosive events. A spine field line links distinct
flux domains, but direct observation of such feature has been rare. Here we
report a unique event observed by the Solar Dynamic Observatory where a set of
hot coronal loops (over 10 MK) connected to a quasi-circular chromospheric
ribbon at one end and a remote brightening at the other. Magnetic field
extrapolation suggests these loops are partly tracer of the evolving spine
field line. Continuous slipping- and null-point-type reconnections were likely
at work, energizing the loop plasma and transferring magnetic flux within and
across the fan quasi-separatrix layer. We argue that the initial reconnection
is of the "breakout" type, which then transitioned to a more violent flare
reconnection with an eruption from the fan dome. Significant magnetic field
changes are expected and indeed ensued. This event also features an
extreme-ultraviolet (EUV) late phase, i.e. a delayed secondary emission peak in
warm EUV lines (about 2-7 MK). We show that this peak comes from the cooling of
large post-reconnection loops beside and above the compact fan, a direct
product of eruption in such topological settings. The long cooling time of the
large arcades contributes to the long delay; additional heating may also be
required. Our result demonstrates the critical nature of cross-scale magnetic
coupling - topological change in a sub-system may lead to explosions on a much
larger scale.Comment: Accepted for publication in ApJ. Animations linked from pd
- …