From Laser Induced Line Narrowing To Electromagnetically Induced Transparency: Closed System Analysis

Laser induced line narrowing effect, discovered more than thirty years ago, can also be applied to recent studies in high resolution spectroscopy based on electromagnetically induced transparency. In this paper we first present a general form of the transmission width of electromagnetically induced transparency in a homogeneously broadened medium. We then analyze a Doppler broadened medium by using a Lorentzian function as the atomic velocity distribution. The dependence of the transmission linewidth on the driving field intensity is discussed and compared to the laser induced line narrowing effect. This dependence can be characterized by a parameter which can be regarded as ``the degree of optical pumping''.Comment: 8 pages, 5 figure

Geography, News Media Discourse, and Water Management: A Case Study of the Devils Lake Outlet

This thesis explores the print news media discourse surrounding the dispute between Manitoba and North Dakota over a flood mitigation plan in Devils Lake North Dakota. In order to do so, critical discourse analysis was applied to news media from a seventeen year period during the dispute. Findings were compared between media sources as well as to pertinent policy documents. The thesis finds that the political arena provided by local newspapers as well as the discourses of scale, confrontation, history, and economics had the largest effect on the dispute’s public face. A total of nine findings within these areas are discussed for their relationship to the dispute. Existing concepts from within geography are acknowledged to place these insights into the broader set of geographical and water management discussions. It is concluded that research on environmental conflicts needs to pay special attention to news media and other forms of discourse creation, or promotion, in the public sphere in order to better understand these conflicts, broaden the scope of values involved and promote the potential for efficient conflict resolution and water management

The Governance of Climate Change Adaptation in Canada: Two Multilevel Case Studies

Anthropogenic climate change is affecting, and will continue to affect, communities across Canada. From increased average temperatures and alterations of seasonal precipitation patterns, to extreme rainfall and heat events, Canadians face a 21st century environment significantly different from that of the past. With risks to people and services identified via the global scientific and social science literature, the need to adapt to climate change is pressing. Climate change adaptation includes the identification of climate impacts in order to develop interventions into systems and services so to avoid negative effects and recognize opportunities. The emerging consensus is that climate change adaptation is challenged by the complexity of the cross-sector and cross-scale nature of climate impacts and the systems and services which are vulnerable to them. Due to jurisdictional divisions and public-private divides in many climate-impacted systems, adaptation scholarship has increasingly turned to the study of governance to conceptualize and overcome challenges. To contribute to this field, this study engages in an in-depth characterization of the current governance of climate change adaptation in Canada. Using an established theoretical framework of competing governance modes, the study characterizes adaptation governance in two Canadian sites as well as identifies the preferred visions of governing processes according to expert practitioners. Through analysis of key documents, eighty-one in-depth interviews, and two expert workshops, the thesis provides a number of novel insights for Canadian and international scholarship. In the thesis it is argued that the study of adaptation governance benefits from the application of a typology of competing governance modes. Further, the study identifies that current adaptation efforts in the Canadian sites are dominated by network processes and that the concept of network failure is consistent with the observed adaptation implementation deficit. Finally, it is revealed that practitioners at different scales of government in Canada’s federal structure idealize the governance of adaptation in drastically different ways, with local respondents providing critiques of network processes and increased interest in hierarchical governance. As climate impacts are projected to worsen in the coming decades, the findings of the study offer crucial insights for intervention into the governance of climate change adaptation

The two-angle model and the phase diagram for Chromatin

We have studied the phase diagram for chromatin within the framework of the two-angle model. Rather than improving existing models with finer details our main focus of the work is getting mathematically rigorous results on the structure, especially on the excluded volume effects and the effects on the energy due to the long-range forces and their screening. Thus we present a phase diagram for the allowed conformations and the Coulomb energies

How does the chromatin fiber deal with topological constraints?

In the nuclei of eukaryotic cells, DNA is packaged through several levels of compaction in an orderly retrievable way that enables the correct regulation of gene expression. The functional dynamics of this assembly involves the unwinding of the so-called 30 nm chromatin fiber and accordingly imposes strong topological constraints. We present a general method for computing both the twist and the writhe of any winding pattern. An explicit derivation is implemented for the chromatin fiber which provides the linking number of DNA in eukaryotic chromosomes. We show that there exists one and only one unwinding path which satisfies both topological and mechanical constraints that DNA has to deal with during condensation/decondensation processes.Comment: Presented in Nature "News and views in brief" Vol. 429 (13 May 2004). Movies available at http://www.lptl.jussieu.fr/recherche/operationE_fichiers/Page_figurePRL.htm

Information security management:ANP based approach for risk analysis and decision making

In information systems security, the objectives of risk analysis process are to help to identify new threats and vulnerabilities, to estimate their business impact and to provide a dynamic set of tools to control the security level of the information system. The identification of risk factors as well as the estimation of their business impact require tools for assessment of risk with multi-value scales according to different stakeholders' point of view. Therefore, the purpose of this paper is to model risk analysis decision making problem using semantic network to develop the decision network and the Analytical Network Process (ANP) that allows solving complex problems taking into consideration quantitative and qualitative data. As a decision support technique ANP also measures the dependency among risk factors related to the elicitation of individual judgement. An empirical study involving the Forestry Company is used to illustrate the relevance of ANP

Torsional Directed Walks, Entropic Elasticity, and DNA Twist Stiffness

DNA and other biopolymers differ from classical polymers due to their torsional stiffness. This property changes the statistical character of their conformations under tension from a classical random walk to a problem we call the `torsional directed walk'. Motivated by a recent experiment on single lambda-DNA molecules [Strick et al., Science 271 (1996) 1835], we formulate the torsional directed walk problem and solve it analytically in the appropriate force regime. Our technique affords a direct physical determination of the microscopic twist stiffness C and twist-stretch coupling D relevant for DNA functionality. The theory quantitatively fits existing experimental data for relative extension as a function of overtwist over a wide range of applied force; fitting to the experimental data yields the numerical values C=120nm and D=50nm. Future experiments will refine these values. We also predict that the phenomenon of reduction of effective twist stiffness by bend fluctuations should be testable in future single-molecule experiments, and we give its analytic form.Comment: Plain TeX, harvmac, epsf; postscript available at http://dept.physics.upenn.edu/~nelson/index.shtm