The action of a casual set

A causal set is a model for a discrete spacetime in which the “atoms of spacetime” carry a relation of ancestry. This order relation is mathematically given by a partial order, and is is taken to underly the macroscopic causal notions of before and after. The work presented in this thesis proposes a definition for the action of a causal set analogous to the continuum Einstein-Hilbert action. The path taken towards the definition of this action is somewhat indirect. We first construct a retarded wave operator on causal sets well-approximated by 4-dimensional spacetimes and prove, under certain assumptions, that this operator gives the usual continuum d’Alembertian and the scalar curvature of the approximating spacetime in the continuum limit. We use this result to define both the scalar curvature and the action of a causal set. This definition can be shown to work in any dimension, so that an explicit form of the action exists in all dimensions. We conjecture that, under certain conditions, the continuum limit of the action is given by the Einstein-Hilbert action up to boundary terms, whose explicit form we also conjecture. We provide evidence for this conjecture through analytic and numerical calculations of the expected action of various spacetime regions. The 2-dimensional action is shown to possess topological properties by calculating its expectation value for various regions of 2-dimensional spacetimes with different topologies. We find that the topological character of the 2d action breaks down for causally convex regions of the trousers spacetime that contain the singularity, and for non-causally convex rectangles. Finally, we propose a microscopic account of the entropy of causal horizons based on the action. It is a form of “spacetime mutual information” arising from the partition of spacetime by the horizon. Evidence for the proposal is provided by analytic results and numerical simulations in 2- dimensional examples. Further evidence is provided by numerical results for the Rindler and cosmic deSitter horizons in both 3 and 4-dimensions, and for a non-equilibrium horizon in a collapsing shell spacetime in 4-dimensions.Open Acces

Phytoremediation potential of alimurgic plants in metal-contaminated environments

As soil metal contamination is rapidly increasing worldwide, mainly because of human activities, phytomanagement of polluted land is becoming an environmentally sustainable and cost-effective option that can also produce biomass and energy as secondary utilities. Some Asteraceae and Polygonaceae species growing spontaneously as invasive weeds on natural and farmed land, which are considered medical or edible alimurgic species, have been identified to accumulate high above-ground levels of toxic elements, thanks to efficient root-to-shoot translocation. Most of them combine high adaptability to marginal soils with good shoot biomass, and many are metal indicator or hyperaccumulator species. In this study were investigated the shoot and root growth potential, metal uptake and translocation at the flowering stage of wild chicory (Cichorium intybus L.), common sowthistle (Sonchus oleraceus L.), salsify (Tragopogon porrifolius L.), common dandelion (Taraxacum officinale Web.) and garden sorrel (Rumex acetosa L.) in artificially highly Cd-Co-Cu-Pb-Zn-contaminated soil

THE VALUE OF THE GULF OF MEXICO RECREATIONAL RED SNAPPER FISHERY

This study estimates the value of recreational red snapper fishing in the Gulf of Mexico. Additionally, the study shows how to decompose the estimated red snapper recreation demand function into changes: (i) due to recreationists who were not taking recreational red snapper fishing trips but were induced to take a trip in response to changes in catch rates and (ii) due to recreationists already taking trips and responding to changes in catch rates. The decomposition allows us to also decompose the estimated elasticities and consumer surplus. The results indicate that an improvement in expected fishing quality will increase consumer surplus and that most of the increase is contributed by recreationists who initially do not take recreational red snapper fishing trips, but later take a positive number of trips. This finding has important policy implications for managing the red snapper fishery in the Gulf of Mexico.Resource /Energy Economics and Policy,

Evaluating the Aryl Hydrocarbon Receptor as a Target for Pharmacologic Activity of Repurposed Drugs

The discovery of new pharmacologic targets is important for the advancement of pharmacotherapy and identification of new indications for current drugs. The aryl hydrocarbon receptor (AHR) is a physiologic sensor of both chemical environmental pollutants and ligands of natural origin. Given the broad spectrum of ligands that activate the AHR and its relationship with toxicology, the AHR is not thought to be a traditional target for pharmacotherapy. However, multiple studies have shown potential for the AHR as a novel pharmacologic target Therefore, identifying less toxic agents that modulate the AHR may elucidate mechanisms for pharmacological targeting of the AHR. The hypothesis addressed for this thesis project is that chemical libraries of established drugs can be used to map the pharmacological space of the aryl hydrocarbon receptor. Three specific aims are proposed to address this hypothesis. Specific aim 1: Develop a high throughput screening assay to identify established drugs that activate the AHR. Specific aim 2: Use a chemical library of known pharmacologically active agents to map pharmacological space of the AHR and identify a lead compound for further evaluation. Specific aim 3: Determine chemical structure activity relationship of the lead compound’s pharmacophores and AHR activation potency. The AHR assay developed for Aim 1 incorporated an AHR-responsive green fluorescence protein (GFP) reporter that could be transduced into any cell type of interest. For normalization of transduction efficiency, a dtTomato expressing vector was optimized for expression without interference of the GFP reporter. Both the human colon cancer cell line Caco2 and the liver cancer cell line HepG2 were used in these studies. Drug screening for AHR activation using the AHR assay resulted in the identification multiple ligands including a lead compound. The lead compound in this study used for further evaluation was alpha-tocopherylquinone (TQ). The quinone structure is a critical component of TQ, interestingly other AHR ligands have been found to have a quinone structure as a molecular component. (eg dioxin) However, quinone structure ability to activate the AHR is less defined compared to other compounds like polycyclic carbons. In this study, differences were observed in the toxicity and AHR activation profile of fully substituted and unsubstituted para-quinones. The findings from these experiments suggest that there is a direct relationship between the number of carbon substitutions and the potency of the para-quinone to elicit an effect on the AHR. For example, we found that benzoquinone (BQ), an unsubstituted para-quinone was a relatively potent ligand of the AHR. Furthermore, adding a single methyl group to the benzoquinone increased its potency to activate the AHR. However, further methyl substitutions to the para-quinone ring diminished the para-quinone potency to activate the AHR. A compound that supported this observation was duroquinone, a fully substituted para-quinone which showed no AHR activity in the AHR assay. This study identifies critical characteristics necessary for para-quinones to activate the AHR and gives rise to a new class of compounds with potential of becoming novel treatments for disease through AHR activation

Phytoremediation opportunities with alimurgic species in metal-contaminated environments

Alimurgic species are edible wild plants growing spontaneously as invasive weeds in natural grassland and farmed fields. Growing interest in biodiversity conservation projects suggests deeper study of the multifunctional roles they can play in metal uptake for phytoremediation and their food safety when cultivated in polluted land. In this study, the responses of the tap-rooted perennial species Cichorium intybus L., Sonchus oleracerus L., Taraxacum officinaleWeb., Tragopogon porrifolius L. and Rumex acetosa L. were studied in artificially-highly Cd-Co-Cu-Pb-Zn-contaminated soil in a pot-scale trial, and those of T. officinale and R. acetosa in critical open environments (i.e., landfill, ditch sediments, and sides of highly-trafficked roads). Germination was not inhibited, and all species showed appreciable growth, despite considerable increases in tissue metal rates. Substantial growth impairments were observed in C. intybus, T. officinale and T. porrifolius; R. acetosa and S. oleracerus were only marginally affected. Zn was generally well translocated and reached a high leaf concentration, especially in T. officinale (~600 mg/kg dry weight, DW), a result which can be exploited for phytoremediation purposes. The elevated Cd translocation also suggested applications to phytoextraction, particularly with C. intybus, in which leaf Cd reached ~16 mg/kg DW. The generally high root retention of Pb and Cu may allow their phytostabilisation in the medium-term in no-tillage systems, together with significant reductions in metal leaching compared with bare soil. In open systems, critical soil Pb and Zn were associated with heavily trafficked roadsides, although this was only seldom reflected in shoot metal accumulation. It is concluded that a community of alimurgic species can serve to establish an efficient, long-lasting vegetation cover applied for phytoremediation and reduction of soil metal movements in degraded environments. However, their food use is not recommended, since leaf Cd and Pb may exceed EU safety thresholds

Clustering to minimize the maximum intercluster distance

AbstractThe problem of clustering a set of points so as to minimize the maximum intercluster distance is studied. An O(kn) approximation algorithm, where n is the number of points and k is the number of clusters, that guarantees solutions with an objective function value within two times the optimal solution value is presented. This approximation algorithm succeeds as long as the set of points satisfies the triangular inequality. We also show that our approximation algorithm is best possible, with respect to the approximation bound, if P ≠ NP

Combined endophytic inoculants enhance nickel phytoextraction from serpentine soil in the hyperaccumulator Noccaea caerulescens

This study assesses the effects of specific bacterial endophytes on the phytoextraction capacity of the Ni-hyperaccumulator Noccaea caerulescens, spontaneously growing in a serpentine soil environment. Five metal-tolerant endophytes had already been selected for their high Ni tolerance (6 mM) and plant growth promoting ability. Here we demonstrate that individual bacterial inoculation is ineffective in enhancing Ni translocation and growth of N. caerulescens in serpentine soil, except for specific strains Ncr-1 and Ncr-8, belonging to the Arthrobacter and Microbacterium genera, which showed the highest indole acetic acid production and 1-aminocyclopropane-1-carboxylic acid-deaminase activity. Ncr-1 and Ncr-8 co-inoculation was even more efficient in promoting plant growth, soil Ni removal, and translocation of Ni, together with that of Fe, Co, and Cu. Bacteria of both strains densely colonized the root surfaces and intercellular spaces of leaf epidermal tissue. These two bacterial strains also turned out to stimulate root length, shoot biomass, and Ni uptake in Arabidopsis thaliana grown in MS agar medium supplemented with Ni. It is concluded that adaptation of N. caerulescens in highly Ni-contaminated serpentine soil can be enhanced by an integrated community of bacterial endophytes rather than by single strains; of the former, Arthrobacter and Microbacterium may be useful candidates for future phytoremediation trials in multiple metal-contaminated sites, with possible extension to non-hyperaccumulator plants

THE INFLUENCE OF HIGH DENSITY POLYETHYLENE TO CHARACTERISTIC OF HOT ROLLED SHEET

Hot Rolled Sheet (HRS) is a kind ofpavement mix design that consist of aggregate, asphalt, and filler. The materials were hotmixed and compacted in specific temperature. The use of additive material was expected to improve the characteristic of asphalt mix design that is shown by Marshall Test. High density polyethylene (HDPE) was polymer that has thermoplastic characteristic which is similar with the characteristic of asphalt. The purpose of this research is to know whenever HDPE can be added into, also it is expected that HDPE may improve the mixture. In this research the use of HDPE waste in the mixtures was 0%, 3%, 5%, 7% and 9%. Asphalt content was 5%, 5.5%, 6%, 6.5%, and 7%. Analysis is based on the references, especially regulation that published by BinaMarga (2010). The result of research, show HDPE content 3% and 5 two samples for each proportion of HDPE, therefore, there are 50 samples in total. The result of this research is that HDPE can be use as additive in HRS WC with content 3% and 5%. The optimum asphalt content is 6.8%. The additions of HDPE also increase several Marshall Parameters such as stability value, VITM value and MQ value. However, HDPE decrease flow, VFWA, and density value of the mixtur