Canonical density matrix perturbation theory

Density matrix perturbation theory [Niklasson and Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] is generalized to canonical (NVT) free energy ensembles in tight-binding, Hartree-Fock or Kohn-Sham density functional theory. The canonical density matrix perturbation theory can be used to calculate temperature dependent response properties from the coupled perturbed self-consistent field equations as in density functional perturbation theory. The method is well suited to take advantage of sparse matrix algebra to achieve linear scaling complexity in the computational cost as a function of system size for sufficiently large non-metallic materials and metals at high temperatures.Comment: 21 pages, 3 figure

Can we solve it in the workshop? : Learning in river restoration and climate policy implementation

The last three decades of environmental policymaking have generated some very ambitious and comprehensively formulated policies, ranging from the local to the global level. These policies often have the explicit aim of addressing and reversing some of the most significant trends of environmental degradation, including biodiversity loss and climate change. However, despite evidence of successful progress in the formulation of environmental policies, their implementation and goal fulfillment are generally low. The inadequate fulfillment of environmental policy goals has partially been linked to the perceived limitations of using coercive-based implementation to solve complex environmental problems. Meanwhile, participation and learning are gaining prominence, since they are expected to cope better with complex and unpredictable environmental systems and thereby contribute to the implementation of environmental policy. However, complexity is only one of several decisive contextual factors, which affect environmental policy implementation and governance. For this reason, this thesis questioned and explored the extent to which learning constitutes the most appropriate mode for environmental policy implementation, and under what circumstances. The introductory chapter frames learning as an implementation mode and conceptualizes it as one of three ideal-type implementation modes; the others being coercion and market. It introduces conflict as a crucial context for environmental policy implementation and hypothesizes that there are three facets of conflict, which are particularly relevant: conflicts of interest between stakeholders, conflicts in environmental policy goals, and legislation. Furthermore, it combines identified variables and concepts into a conceptual model that treats change in target group behavior as the outcome of policy and a dependent variable in environmental policy implementation. Policy outcomes are assessed in terms of their effectiveness and coherence. The thesis was guided by the following research questions: 1. How do stakeholder conflicts of interest and legislation influence the effectiveness of learning as an implementation mode? 2. How are conflicts in environmental policy goals manifested, and what role can a learning-based implementation mode play in increasing policy coherence? A multi-case study approach was chosen for this thesis since it allows for a detailed examination of the relevant contextual factors and an exploration of the possible causal mechanisms. As the thesis hypothesizes that conflict is a crucial context for environmental policy implementation, the case studies were selected in two environmental policy domains with different levels of conflict. Chapters 2-4 comprise several cases of environmental policy implementation that involve high conflict, concerning river restoration that affects hydropower production. These cases span different governance scales in Sweden, the United States and the European Union. Chapter 5 details another case, containing low conflict, concerning learning as an implementation mode in adaptations of urban water services related to climate change in the Stockholm Region, Sweden. The thesis uses a variety of data collection strategies; including document analysis, semi-structured interviews, and participant observation. This allows for a strong contextual understanding and for triangulations of the insights gathered from the various data sources. The main paths for establishing the claims of causation, between policy initiatives, implementation modes and policy outcomes in the examined cases, are the counterfactual as well as the mechanism and capacities approaches. A number of key findings emerge from the preceding chapters, related to the two thesis research questions. As concerns the first question; the thesis finds that legislation is a key determining element that influences the effectiveness of learning in situations that exhibit high levels of stakeholder conflicts of interest. Chapter 4, a case study of a failed learning-based intervention in the Ljusnan River basin, Sweden, demonstrates how the effectiveness of learning was limited by existing legislation since it gave the target group of policy the option to reach its objectives unilaterally. In contrast to Chapter 4, Chapter 5 shows how learning can produce effective policy outcomes, despite limited legislation, in situations of low stakeholder conflicts of interest. In this case, despite the absence of rules and regulations requiring climate change adaptation, the urban water service organizations in the Stockholm Region have enacted significant behavioral changes geared towards climate change adaptation through organizational learning. As concerns the second research question; the results illustrate how environmental policy goal conflict is mainly materialized and manifested during the implementation of environmental policy. Chapter 2 concludes that, despite limited evidence of conflictual interactions at the level of policy goals and instruments, potentially strong conflicts emerge when it comes to policy implementation at both EU and member state level. The results also point towards the potential pitfalls and possibilities of the role that learning can play in policy coherence, largely depending upon legislation. Chapter 3 illustrates the differences, between Sweden and the United States, in the legislative settings of hydropower production as it concerns river restoration. Whereas hydropower production in Sweden is regulated by perpetual, property-like permits; in the United States, non-federal facilities are regulated by temporal licenses granting a time-bound privilege to use public lands and waters. Chapter 4 concludes that the perpetual hydropower permits in Sweden were an important reason behind the failed learning-based intervention in the Ljusnan River basin. The same chapter, however, also introduces the example of the Penobscot Basin, in the United States, where a learning-based intervention has produced significant river restoration outcomes while preserving hydropower generation at previous levels. Chapter 4 identifies the legal arrangements surrounding non-federal hydropower facilities in the United States, notably time-bound permits, as an important reason as to why the learning-based intervention in the Penobscot Basin produced results that increased policy coherence between different environmental policy goals. Based on these answers to the two research questions, an overarching insight from the thesis is that the shape and formulation of legislation constitutes a significant variable, in determining the appropriateness of learning in environmental policy implementation that contains high conflict. The thesis’ analysis suggests that learning, together with favorable legislation, could be a viable way of dealing with complexity, while preventing the inaction that may arise from stakeholder conflicts of interest. Through its empirical cases, this thesis provides evidence and arguments that relate observed behavioral changes to the policy of interest, in varying degrees. Moreover, the examples, in the discussion of environmental policy implementation affecting fisheries and agriculture, show that the findings are also relevant to situations of environmental policy implementation that affect the industrial use and extraction of natural resources more broadly. The thesis ends by offering a suggestion to policymakers who are faced with ineffective implementations of environmental policy: that they recognize the requirements and limits of learning, particularly in high conflict situations.</p

Electrostatic considerations affecting the calculated HOMO-LUMO gap in protein molecules.

A detailed study of energy differences between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO gaps) in protein systems and water clusters is presented. Recent work questioning the applicability of Kohn-Sham density-functional theory to proteins and large water clusters (E. Rudberg, J. Phys.: Condens. Mat. 2012, 24, 072202) has demonstrated vanishing HOMO-LUMO gaps for these systems, which is generally attributed to the treatment of exchange in the functional used. The present work shows that the vanishing gap is, in fact, an electrostatic artefact of the method used to prepare the system. Practical solutions for ensuring the gap is maintained when the system size is increased are demonstrated. This work has important implications for the use of large-scale density-functional theory in biomolecular systems, particularly in the simulation of photoemission, optical absorption and electronic transport, all of which depend critically on differences between energies of molecular orbitals.Comment: 13 pages, 4 figure

Relativistic diffusion processes and random walk models

The nonrelativistic standard model for a continuous, one-parameter diffusion process in position space is the Wiener process. As well-known, the Gaussian transition probability density function (PDF) of this process is in conflict with special relativity, as it permits particles to propagate faster than the speed of light. A frequently considered alternative is provided by the telegraph equation, whose solutions avoid superluminal propagation speeds but suffer from singular (non-continuous) diffusion fronts on the light cone, which are unlikely to exist for massive particles. It is therefore advisable to explore other alternatives as well. In this paper, a generalized Wiener process is proposed that is continuous, avoids superluminal propagation, and reduces to the standard Wiener process in the non-relativistic limit. The corresponding relativistic diffusion propagator is obtained directly from the nonrelativistic Wiener propagator, by rewriting the latter in terms of an integral over actions. The resulting relativistic process is non-Markovian, in accordance with the known fact that nontrivial continuous, relativistic Markov processes in position space cannot exist. Hence, the proposed process defines a consistent relativistic diffusion model for massive particles and provides a viable alternative to the solutions of the telegraph equation.Comment: v3: final, shortened version to appear in Phys. Rev.

High Rate of Regression From Micro-Macroalbuminuria to Normoalbuminuria in Children and Adolescents With Type 1 Diabetes Treated or Not With Enalapril: The influence of HDL cholesterol

OBJECTIVE: To evaluate the frequency of normalization, the persistence of remission, and the impact on normalization of glycemic control and lipid profile, we analyzed data from a retrospective observational cohort study of type 1 diabetic children and adolescents with abnormal urinary albumin excretion (UAE). RESEARCH DESIGN AND METHODS: All diabetic children and adolescents (n = 41) who had persistent abnormal UAE in the period of 1984 to 2008 and followed up until 2009 (follow-up duration = 13.1 \ub1 6.2 years) were included in the study. Nine patients progressed to macroalbuminuria; 24 patients were administered ACE inhibitor treatment. RESULTS: The cumulative prevalence of abnormal UAE was 9%. During follow-up, 14 of 17 untreated and 19 of 24 treated patients reverted to normoalbuminuria. In the remission group compared with the nonremission group, A1C levels during follow-up decreased (7.5 \ub1 1.0 vs. 9.4 \ub1 1.2%, P < 0.0001) and serum HDL cholesterol increased (52.7 \ub1 11.3 vs. 42.7 \ub1 8.6 mg/dL, P < 0.05). The micro-macroalbuminuric patients had lower HDL cholesterol (51.0 \ub1 11.4 vs. 62.4 \ub1 13.6 mg/dL, P < 0.0001) than 134 normoalbuminuric diabetic patients. CONCLUSIONS: Microalbuminuria and macroalbuminuria were not permanent in most of our diabetic children and adolescents. If abnormal UAE values are high and persist for >1 year, only long-lasting treatment with ACE inhibitors seems able to induce persistent remission, especially when associated with good metabolic control and high HDL cholesterol level

Diffusion in the special theory of relativity

The Markovian diffusion theory is generalized within the framework of the special theory of relativity using a modification of the mathematical calculus of diffusion on Riemannian manifolds (with definite metric) to describe diffusion on Lorentzian manifolds with an indefinite metric. A generalized Langevin equation in the fiber space of position, velocity and orthonormal velocity frames is defined from which the generalized relativistic Kramers equation in the phase space in external force fields is derived. The obtained diffusion equation is invariant under Lorentz transformations and its stationary solution is given by the J\"{u}ttner distribution. Besides a non-stationary analytical solution is derived for the example of force-free relativistic diffusion.Comment: 10 pages, 1 figur

O(N) methods in electronic structure calculations

Linear scaling methods, or O(N) methods, have computational and memory requirements which scale linearly with the number of atoms in the system, N, in contrast to standard approaches which scale with the cube of the number of atoms. These methods, which rely on the short-ranged nature of electronic structure, will allow accurate, ab initio simulations of systems of unprecedented size. The theory behind the locality of electronic structure is described and related to physical properties of systems to be modelled, along with a survey of recent developments in real-space methods which are important for efficient use of high performance computers. The linear scaling methods proposed to date can be divided into seven different areas, and the applicability, efficiency and advantages of the methods proposed in these areas is then discussed. The applications of linear scaling methods, as well as the implementations available as computer programs, are considered. Finally, the prospects for and the challenges facing linear scaling methods are discussed.Comment: 85 pages, 15 figures, 488 references. Resubmitted to Rep. Prog. Phys (small changes

Idiopathic osteonecrosis of the medial tibial plateau

Osteonecrosis of the medial tibial plateau is characterized by acute pain on the medial aspect of the knee. Progression can lead to articular collapse and requires early diagnosis and treatment. We studied seven patients affected of idiopathic osteonecrosis of the tibial plateau. The mean age was 62 years and the mean follow-up 42 months. We performed roentgenograms in all patients, bone scans in three patients and magnetic resonance image (MRI) in five. MRI shows T1-weighted low-intensity signal and T2-weighted high-intensity signal with a surrounding area of intermediate low-intensity signal. An increased focal uptake was seen at bone scan. Histological findings showed necrotic bone with empty lacunae. Surgical treatment consisted of tibial subchondral drilling in four patients-two of them by failure of conservative treatment, and a total knee arthroplasty in other two. One patient had a satisfactory evolution with conservative treatment. Idiopathic osteonecrosis of the tibial plateau must be considered in elderly patients with knee pain over the medial tibial plateau. At early stages, decompression with tibial drilling must be considered. This procedure allows a prompt and effective relief of symptom

Purification and functional characterisation of rhiminopeptidase A, a novel aminopeptidase from the venom of Bitis gabonica rhinoceros

This study describes the discovery and characterisation of a novel aminopeptidase A from the venom of B. g. rhinoceros and highlights its potential biological importance. Similar to mammalian aminopeptidases, rhiminopeptidase A might be capable of playing roles in altering the blood pressure and brain function of victims. Furthermore, it could have additional effects on the biological functions of other host proteins by cleaving their N-terminal amino acids. This study points towards the importance of complete analysis of individual components of snake venom in order to develop effective therapies for snake bites