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Fluorescence of Single Conjugated Chains of MEH-PPV Dispersed in Polymer Matrix: What Do We See in the Microscope?

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Chinese Journal of Chemistry 2023年第19期41卷 2536-2544页

作者： Mingyi Xie Marina V.Kuzimenkova Per-olof Larsson Yuxi Tian Ivan G.Scheblykin Key Laboratory of Mesoscopic Chemistry of MOE School of Chemistry and Chemical EngineeringNanjing UniversityNanjingJiangsu210023 China Chemical Physics and NanoLund Lund UniversityPO Box 124SE-22100 LundSweden Pure and Applied Biochemistry Lund UniversityPO Box 124SE-22100 LundSweden

It has been a mystery that the detected fluorescence intensity of single MEH-PPV molecules is much lower than expected based on their chain length.In this review,after re-evaluating of the literature data in the light of new specially designed experiments,we present a comprehensive explanation of this issue:The actual size of MEH-PPV molecules at single molecule level is much smaller than expected due to de-aggregation and chain scission,while static quenching("dark matter")also exists for large molecules,further reducing their brightness.

关键词： MEH-PPV Single molecule spectroscopy Brightness Fluorescence Molecular weight anrohonci

Mathematical Models and Numerical Methods for High Frequency Waves

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Communications in Computational Physics 2007年第5期2卷 827-880页

作者： olof Runborg Department of Numerical Analysis School of Computer Science and CommunicationKTH10044 StockholmSweden.

The numerical approximation of high frequency wave propagation is important in many applications.Examples include the simulation of seismic,acoustic,optical waves and microwaves.When the frequency of the waves is high,this is a difficult multiscale problem.The wavelength is short compared to the overall size of the computational domain and direct simulation using the standard wave equations is very expensive.Fortunately,there are computationally much less costly models,that are good approximations of many wave equations precisely for very high frequencies.Even for linear wave equations these models are often nonlinear.The goal of this paper is to review such mathematical models for high frequency waves,and to survey numerical methods used in simulations.We focus on the geometrical optics approximation which describes the infinite frequency limit of wave equations.We will also discuss finite frequency corrections and some other models.

关键词： Geometrical optics wave equation Helmholtz equation high frequency waves eikonal equation ray tracing multiscale problems.

Why People Live in Flood-Prone Areas in Akuressa, Sri Lanka

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International Journal of Disaster Risk Science 2018年第2期9卷 143-156页

作者： Johan Askman olof Nilsson Per Becker Division of Risk Management and Societal Safety Lund University

To investigate why people live in areas at high risk of floods, a qualitative case study was carried out in the areas around Akuressa, in southwest Sri Lanka. Data collection consisted mainly of semistructured interviews with local residents and government officials. The purpose was to study why people live in areas at high risk of floods, by looking beyond the purely physical aspects of living with hazards and exploring the underlying social factors. Four main factors were identified: an overall good living situation; a sense of place; difficulties relocating; and being well-adapted to the situation. The analysis also examined whether government officials shared the views of local residents. The findings highlighted both areas of consensus and discrepancies related to risk awareness, and the efficiency of risk reduction measures that had been implemented by the government. The case study identified and explored underlying social factors, such as risk normalization, risk trade-offs, and push-and-pull processes, which seem to influence the decision to live in a high-risk area.

关键词： Flood risk Risk awareness Risk perception Sri Lanka

Influence of confining prestress on the transition from interface defeat topenetration in ceramic targets

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Defence Technology（防务技术） 2016年第3期12卷 263-271页

作者： Patrik LUNDBERG RenéRENSTROM olof ANDERSSON FOI Swedish Defence Research AgencySE-164 90 StockholmSweden

Replica scaled impact experiments with unconfined ceramic targets have shown that the transition velocity,i.e.,the impact velocity at which interface defeat ceases and ceramic penetration occurs,decreased as the length scale increased.A possible explanation of how this scale effect is related to the formation of a cone crack in the ceramic has been presented by the authors in an earlier paper.Here,the influence of confinement and prestress on cone cracking and transition velocity is investigated.The hypothesis is that prestress will suppress the formation and growth of the cone crack by lowering the driving stress.A set of impact experiments has been performed in which the transition velocity for four different levels of prestress has been determined.The transition velocities as a function of the level of confining prestress is compared to an analytical model for the influence of prestress on the formation and extension of the cone crack in the ceramic material.Both experiments and model indicate that prestress has a strong influence on the transition from interface defeat to penetration,although the model underestimates the influence of prestress.

关键词： Impact Ceramic Armour Interface defeat Dwell Confinement Prestress

Deformation,fragmentation and acceleration of a controlled fragmentation charge casing

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Defence Technology（防务技术） 2019年第5期15卷 786-795页

作者： Andreas Helte olof Andersson Patrik Lundberg FOI Defence and SecuritySystems and Technology

Two different finite element software,LS-DYNA and Impetus,have been evaluated to test their ability to predict the deformation,fragmentation and acceleration of a controlled fragmentation charge casing.The general-purpose program LS-DYNA was used with a multi-material ALE formulation and a masspreserving erosion criterion coupled to a Johnson-Cook fracture criterion.In the Impetus simulations,a third order Lagrangian element formulation was used for the casing and a node-splitting element erosion treatment coupled to a Cockcroft-Latham failure criterion was used to describe casing fracture.The high-explosive gases were described by a discrete particle formalism.In order to acquire data to validate our computational tools and constitutive models,a series of experiments have been performed using a laboratory charge with an internal grooved casing.In the test series,the charge geometry was fixed except that the groove depth were varied from very shallow to very deep resulting in different deformation patterns,fracture modes and terminal velocities.Various diagnostic tools captured the different stages of the expansion and fragmentation of the casing.A high-speed framing camera depicted the deformation pattern before fragmentation and was used to determine the moment when the casing failed.Three different complementary techniques were used to follow the acceleration of the fragments;a Photon Doppler velocimetry to determine the initial acceleration of the casing,double exposed radiographs to estimate the fragment velocity after break-up and a high-speed video to determine the terminal velocity of the fragment after leaving the fireball.In addition,the fragments were soft recovered in a set of sawdust pit tests and their final shape and weight were measured.A SEM was used to characterise the fracture surfaces and to determine the modus of fracture(tensile or shear failure).Comparisons to experiments show that both software can predict the change in deformation behaviour when the groove depth increases,from tangential

关键词： Controlled fragmentation Fracture mechanics LS-DYNA Impetus

Plato on Necessity and Disorder

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Frontiers of Philosophy in China 2013年第4期8卷 546-565页

作者： olof Pettersson Department of Philosophy Uppsala University 75126 Uppsala Sweden

In the Timaeus, Plato makes a distinction between reason and necessity. This distinction is often accounted for as a distinction between two types of causation： purpose oriented causation and mechanistic causation. While reason is associated with the soul and taken to bring about its effects with the good and the beautiful as the end, necessity is understood in terms of a set of natural laws pertaining to material things. In this paper I shall suggest that there are reasons to reconsider the latter part of this account and argue for a non-mechanistic understanding of necessity. I will first outline how the notion of necessity is introduced in the dialogue. Next I will show how a mechanistic account of necessity fails to capture Plato＇s purpose of treating it as a causal factor; and, finally, I will argue that this purpose is better understood as an attempt, on Plato＇s part, to account for the causal origin of disorder and irrationality, an origin articulated in terms of a pre-cosmic situation and the notoriously difficult notion of the third kind.

关键词： Plato Timaeus causation reason necessity disorder

Inflammatory bowel disease registries for collection of patient iron parameters in Europe

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World Journal of Gastroenterology 2018年第10期24卷 1063-1071页

作者： Jonas Halfvarson Fraser Cummings olof Grip Guillaume Savoye Department of Gastroenterology Faculty of Medicine and HealthOebro UniversityObro SE 70182Sweden Department of Gastroenterology Southampton University Hospital NHS Foundation TrustSouthamptonHampshire SO16 6YDUnited Kingdom Department of Gastroenterology Skae University HospitalMalmo-20502Sweden Service d'heato-gastroenteologie CHU de Rouen-Hoital Charles NicolleRouen 76031France

Iron deficiency without anemia and iron deficiency anemia are common and frequently overlooked complications of inflammatory bowel disease. Despite the frequency and impact of iron deficiency in inflammatory bowel disease, there are gaps in our understanding about its incidence, prevalence and natural history and, consequently, patients may be undertreated. Medical registries have a key role in collecting data on the disease's natural history, the safety and effectiveness of drugs in routine clinical practice, and the quality of care delivered by healthcare services. Even though iron deficiency impacts inflammatory bowel disease patients and healthcare systems substantially, none of the established European inflammatory bowel disease registries systematically collects information on iron parameters and related outcomes. Collection of robust iron parameter data from patient registries is one way to heighten awareness about the importance of iron deficiency in this disease and to generate data to improve the quality of patient care, patient outcomes, and thus quality of life. This objective could be achieved through collection of specific laboratory, clinical, and patientreported measurements that could be incorporated into existing registries. This review describes the status of current European inflammatory bowel disease registries and the data they generate, in order to highlight their potential role in collecting iron data, to discuss how such information gathering could contribute to our understanding of iron deficiency anemia, and to provide practical information in regard to the incorporation of accumulated iron parameter data into registries.

关键词： Anemia Iron deficiency Registries Inflammatory bowel disease Patient care

AN ADAPTIVE FAST INTERFACE TRACKING METHOD

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Journal of Computational Mathematics 2015年第6期33卷 576-586页

作者： Yana Di Jelena Popovic olof Runborg LSEC NCMIS Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China Department of Numerical Analysis CSC KTH 100 44 Stockholm Sweden Department of Mathematics and Swedish e-Science Research Center (SeRC) KTH 100 44 Stockholm Sweden

An adaptive numerical scheme is developed for the propagation of an interface in a velocity field based on the fast interface tracking method proposed in [2]. A multiresolution stategy to represent the interface instead of point values, allows local grid refinement while controlling the approximation error on the interface. For time integration, we use an explicit Runge-Kutta scheme of second-order with a multiseale time step, which takes longer time steps for finer spatial scales. The implementation of the algorithm uses a dynamic tree data structure to represent data in the computer memory. We briefly review first the main algorithm, describe the essential data structures, highlight the adaptive scheme, and illustrate the computational efficiency by some numerical examples.

关键词： Interface tracking Multiresolution adaptivity Fast algorithms.

Coupling of Gaussian Beam and Finite Difference Solvers for Semiclassical Schrodinger Equations

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Advances in Applied Mathematics and Mechanics 2015年第6期7卷 687-714页

作者： Emil Kieri Gunilla Kreiss olof Runborg Division of Scientific Computing Department of Information TechnologyUppsala UniversitySweden Department of Mathematics and Swedish e-Science Research Center(SeRC) KTHSweden

In the semiclassical regime,solutions to the time-dependent Schrodinger equation for molecular dynamics are highly oscillatory.The number of grid points required for resolving the oscillations may become very large even for simple model problems,making solution on a grid intractable.Asymptotic methods like Gaussian beams can resolve the oscillations with little effort and yield good approximations when the atomic nuclei are heavy and the potential is smooth.However,when the potential has variations on a small length-scale,quantum phenomena become important.Then asymptotic methods are less accurate.The two classes of methods perform well in different parameter regimes.This opens for hybrid methods,using Gaussian beams where we can and finite differences where we have to.We propose a new method for treating the coupling between the finite difference method and Gaussian beams.The new method reduces the needed amount of overlap regions considerably compared to previous methods,which improves the efficiency.

关键词： Gaussian beams semiclassical Schrodinger equation hybrid methods