11,604 research outputs found
Internalizing the social costs of smoke emissions into strategic fuels planning models
2016 Summer.Includes bibliographical references.Emissions of fine particulate matter from prescribed burns are a growing concern for wildland fire managers. Stringent air quality regulations and community discern over the emissions from prescribed fire smoke often severely restrict the ability to implement restorative and precautionary fuels treatments. While some extent of emissions are unavoidable, strategic planning can help reduce their impacts. Estimating the cost of smoke and incorporating it into landscape level fire planning may reduce the burden on wildland fire officials confronted with a complex set of choices and constraints. Currently, no decision-support systems are available for strategically incorporating the cost of smoke in fire planning at the landscape level. A decision model is developed to address this void by estimating the value of fire and fuels management at the landscape level by including the cost of smoke in cellular level estimates social returns. By working with locally defined emission standards and translating them into a cost per unit of smoke impact, I was able to internalize the external impact of smoke emissions into a strategic fuels planning model by reprioritizing the optimal selection of landscape grid cells to target for prescribed fire investments. This has the potential to aid the fire planner in analyzing trade-offs for prescribed fire management. In a case study at King's Canyon National Park, emissions standards are used to estimate a relative unit cost of impact (per unit of emissions). The unit cost is subtracted from cellular estimates of marginal social returns to re-prioritize the spatial design of landscape scale fuel treatments
Heterogeneous chemistry related to Antarctic ozone depletion: Reaction of ClONO2 and N2O5 on ice surfaces
Laboratory studies of heterogeneous reactions of possible importance for Antarctic ozone depletion were performed. In particular, the reactions of chlorine nitrate (ClONO2) and dinitrogen pentoxide (N2O5) were investigated on ice and HCl/ice surfaces. These reactions occur on the surfaces of polar stratospheric clouds (PSCs) over Antarctica. One reaction transforms the stable chlorine reservoir species (ClONO2 and HCl) into photochemically active chlorine in the form of HOCl and Cl2. Condensation of HNO3 in the reactions removes odd nitrogen from the stratosphere, a requirement in nearly all models of Antarctic ozone depletion. Other reactions may also be important for Antarctic ozone depletion. Like the reactions of chlorine nitrate, these reactions deplete odd nitrogen through HNO3 condensation. In addition, one reaction converts a stable chlorine reservior species (HCl) into photochemically active chlorine (ClNO2). These reactions were studied with a modified version of a Knudsen cell flow reactor
Attitudes toward immigrants: a cross-country perspective
This paper examines the foundations of attitudes towards immigrants by focusing on individual characteristics and country-specific effects. We use a micro-level data set from 31 countries. In particular, we utilize the module on National Identity of the 2003 International Social Survey Program (ISSP). Results indicate that gender, education, age, labor-market status, and political and religious affiliation are important indicators of the attitude toward immigrants. The largest effect appears to be that of education, with more education being positively correlated with a positive view of immigrants. Additionally, we find that country of residence matters.immigration, microeconomic behavior, comparative research.
Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene
The interaction of CO with an attapulgite-supported Cu(II)Cl2 catalyst has been examined in a micro-reactor arrangement. CO exposure to the dried, as-received catalyst at elevated temperatures leads to the formation of CO2 as the only identifiable product. However, phosgene production can be induced by a catalyst pre-treatment where the supported Cu(II)Cl2 sample is exposed to a diluted stream of chlorine. Subsequent CO exposure at ~ 370°C then leads to phosgene production. In order to investigate the origins of this atypical set of reaction characteristics, a series of x-ray absorption experiments were performed that were supplemented by DFT calculations. XANES measurements establish that at the elevated temperatures connected with phosgene formation, the catalyst is comprised of Cu+ and a small amount of Cu2+. Moreover, the data show that unique to the chlorine pre-treated sample, CO exposure at elevated temperature results in a short-lived oxidation of the copper. On the basis of calculated CO adsorption energies, DFT calculations indicate that a mixed Cu+/Cu2+ catalyst is required to support CO chemisorption
Gene Expression Commons: an open platform for absolute gene expression profiling.
Gene expression profiling using microarrays has been limited to comparisons of gene expression between small numbers of samples within individual experiments. However, the unknown and variable sensitivities of each probeset have rendered the absolute expression of any given gene nearly impossible to estimate. We have overcome this limitation by using a very large number (>10,000) of varied microarray data as a common reference, so that statistical attributes of each probeset, such as the dynamic range and threshold between low and high expression, can be reliably discovered through meta-analysis. This strategy is implemented in a web-based platform named "Gene Expression Commons" (https://gexc.stanford.edu/) which contains data of 39 distinct highly purified mouse hematopoietic stem/progenitor/differentiated cell populations covering almost the entire hematopoietic system. Since the Gene Expression Commons is designed as an open platform, investigators can explore the expression level of any gene, search by expression patterns of interest, submit their own microarray data, and design their own working models representing biological relationship among samples
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A Microeconomic Analysis of Wildfire Suppression Programs in the Western United States
This dissertation studies the microeconomics of forest fire suppression programs. It starts with an inquiry into the causes of increasing shares of public land management budgets devoted to wildland fire suppression in lieu of hazardous fuel reduction or other pre-fire risk mitigation programs. The first two chapters consider competing economic theories for why annual appropriations are predominantly devoted to suppression. The first chapter proposes that this unbalanced allocation can arise from a cost externality generated by the availability of reserve or supplemental funds for suppression. The second chapter proposes an alternative explanation: this type of skewed allocation can result from an incident managerâs aversion to risk. Both chapters rely on a subgame perfect Nash equilibrium result to characterize the resulting budget allocation.
The third chapter also solves a subgame perfect Nash equilibrium to investigate the properties of the fire budgeting problem at the state government level where fire protection programs are funded in part through forest-based taxation. In this chapter, a state tax planner is restricted to two forms of taxation currently used to raise revenue for public forest fire protection programs: 1) a per-acre fee on forestland, and 2) a tax levied per-unit volume of timber harvested. The model shows that when revenues for carbon storage can be captured by private forestland owners, then per-acre fees are the preferred instrument for raising tax revenues and result in a first-best equilibrium outcome. If instead carbon sequestration revenues are not captured by forestland owners, tax planners are constrained to a second-best equilibrium and the use of harvest taxes instead of the per-acre fee on land.
The fourth chapter applies a discrete choice econometric model to administrative data obtained from state and federal fire management agencies overseeing wildfires in the western United States from 2005 to 2014. The model investigates if changes in the availability of reserve funding earmarked for suppression had a significant impact on an incident managerâs likelihood of adopting a full suppression response to unplanned wildfire. This chapter focuses on a change in federal budgeting and policy guidance occurring in fiscal year 2010 to determine if socioeconomic and climatic factors had a different effect on manager choices than they did prior to this policy change. A key factor measured to influence choices via the cost of risk is the distance that a fire burns from residential areas. The model estimates that this factor raised the probability of adopting full suppression following the policy change on fires managed in Washington but lowered the probability on fires managed in Oregon. The model finds evidence that the change in the availability of suppression reserve funds beginning in fiscal year 2010 negatively influenced the probability of adopting full suppression by a small margin, but the effects of this change are indistinguishable from the effects of an update to policy guidance released in 2009
Models predicting survival to guide treatment decision-making in newly diagnosed primary non-metastatic prostate cancer: a systematic review.
OBJECTIVES: Men diagnosed with non-metastatic prostate cancer require standardised and robust long-term prognostic information to help them decide on management. Most currently-used tools use short-term and surrogate outcomes. We explored the evidence base in the literature on available pre-treatment, prognostic models built around long-term survival and assess the accuracy, generalisability and clinical availability of these models. DESIGN: Systematic literature review, pre-specified and registered on PROSPERO (CRD42018086394). DATA SOURCES: MEDLINE, Embase and The Cochrane Library were searched from January 2000 through February 2018, using previously-tested search terms. ELIGIBILITY CRITERIA: Inclusion required a multivariable model prognostic model for non-metastatic prostate cancer, using long-term survival data (defined as â„5 years), which was not treatment-specific and usable at the point of diagnosis. DATA EXTRACTION AND SYNTHESIS: Title, abstract and full-text screening were sequentially performed by three reviewers. Data extraction was performed for items in the CHecklist for critical Appraisal and data extraction for systematic Reviews of prediction Modelling Studies checklist. Individual studies were assessed using the new Prediction model Risk Of Bias ASsessment Tool. RESULTS: Database searches yielded 6581 studies after deduplication. Twelve studies were included in the final review. Nine were model development studies using data from over 231 888 men. However, only six of the nine studies included any conservatively managed cases and only three of the nine included treatment as a predictor variable. Every included study had at least one parameter for which there was high risk of bias, with failure to report accuracy, and inadequate reporting of missing data common failings. Three external validation studies were included, reporting two available models: The University of California San Francisco (UCSF) Cancer of the Prostate Risk Assessment score and the Cambridge Prognostic Groups. Neither included treatment effect, and both had potential flaws in design, but represent the most robust and usable prognostic models currently available. CONCLUSION: Few long-term prognostic models exist to inform decision-making at diagnosis of non-metastatic prostate cancer. Improved models are required to inform management and avoid undertreatment and overtreatment of non-metastatic prostate cancer.The Urology Foundation - Research Scholarship
Cyclic GMP protects human macrophages against peroxynitrite-induced apoptosis
<p>Abstract</p> <p>Background</p> <p>Nitric oxide (NO) can be both pro- and anti-apoptotic in various cell types, including macrophages. This apparent paradox may result from the actions of NO-related species generated in the microenvironment of the cell, for example the formation of peroxynitrite (ONOO<sup>-</sup>). In this study we have examined the ability of NO and ONOO<sup>- </sup>to evoke apoptosis in human monocyte-derived macrophages (MDMÏ), and investigated whether preconditioning by cyclic guanosine monophosphate (cGMP) is able to limit apoptosis in this cell type.</p> <p>Methods</p> <p>Characterisation of the NO-related species generated by (Z)-1- [2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO) and 1,2,3,4-oxatriazolium, 5-amino-3-(3,4-dichlorophenyl)-, chloride (GEA-3162) was performed by electrochemistry using an isolated NO electrode and electron paramagnetic resonance (EPR) spectrometry. Mononuclear cells were isolated from peripheral blood of healthy volunteers and cultured to allow differentiation into MDMÏ. Resultant MDMÏ were treated for 24 h with DETA/NO (100 â 1000 ÎŒM) or GEA-3162 (10 â 300 ÎŒM) in the presence or absence of BAY 41â2272 (1 ÎŒM), isobutylmethylxanthine (IBMX; 1 ÎŒM), 1H- [1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one (ODQ; 20 ÎŒM) or 8-bromo-cGMP (1 mM). Apoptosis in MDMÏ was assessed by flow cytometric analysis of annexin V binding in combination with propidium iodide staining.</p> <p>Results</p> <p>Electrochemistry and EPR revealed that DETA/NO liberated free NO radical, whilst GEA-3162 concomitantly released NO and O<sub>2</sub><sup>-</sup>, and is therefore a ONOO<sup>- </sup>generator. NO (DETA/NO) had no effect on cell viability, but ONOO<sup>- </sup>(GEA-3162) caused a concentration-dependent induction of apoptosis in MDMÏ. Preconditioning of MDMÏ with NO in combination with the phosphodiesterase inhibitor, 3-Isobutyl-1-methylxanthine (IBMX), or the NO-independent stimulator of soluble guanylate cyclase, BAY 41â2272, significantly attenuated ONOO<sup>-</sup>-induced apoptosis in a cGMP-dependent manner.</p> <p>Conclusion</p> <p>These results demonstrate disparities between the ability of NO and ONOO<sup>- </sup>to induce apoptosis in human MDMÏ. Furthermore, this study provides evidence for a novel cGMP-dependent pre-conditioning mechanism to limit ONOO<sup>-</sup>-induced apoptosis in human MDMÏ.</p
A data-based mathematical modelling study to quantify the effects of ciprofloxacin and ampicillin on the within-host dynamics of Salmonella enterica during treatment and relapse.
Antibiotic therapy has drastically reduced the mortality and sequelae of bacterial infections. From naturally occurring to chemically synthesized, different classes of antibiotics have been successfully used without detailed knowledge of how they affect bacterial dynamics in vivo. However, a proportion of patients receiving antimicrobial therapy develop recrudescent infections post-treatment. Relapsing infections are attributable to incomplete clearance of bacterial populations following antibiotic administration; the metabolic profile of this antibiotic-recalcitrant bacterial subpopulation, the spatio-temporal context of its emergence and the variance of antibiotic-bacterial interactions in vivo remain unclear. Here, we develop and apply a mechanistic mathematical model to data from a study comparing the effects of ciprofloxacin and ampicillin on the within-host dynamics of Salmonella enterica serovar Typhimurium in murine infections. Using the inferential capacity of our model, we show that the antibiotic-recalcitrant bacteria following ampicillin, but not ciprofloxacin, treatment belong to a non-replicating phenotype. Aligning with previous studies, we independently estimate that the lymphoid tissues and spleen are important reservoirs of non-replicating bacteria. Finally, we predict that post-treatment, the progenitors of the non-growing and growing bacterial populations replicate and die at different rates. Ultimately, the liver, spleen and mesenteric lymph nodes are all repopulated by progenitors of the previously non-growing phenotype in ampicillin-treated mice.Bursary from Cambridge Mathematical Placement
Mastering the Master Field
The basic concepts of non-commutative probability theory are reviewed and
applied to the large limit of matrix models. We argue that this is the
appropriate framework for constructing the master field in terms of which large
theories can be written. We explicitly construct the master field in a
number of cases including QCD. There we both give an explicit construction
of the master gauge field and construct master loop operators as well. Most
important we extend these techniques to deal with the general matrix model, in
which the matrices do not have independent distributions and are coupled. We
can thus construct the master field for any matrix model, in a well defined
Hilbert space, generated by a collection of creation and annihilation
operators---one for each matrix variable---satisfying the Cuntz algebra. We
also discuss the equations of motion obeyed by the master field.Comment: 46 pages plus 11 uuencoded eps figure
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