The barrier for heme-protein separation estimated by non-equilibrium molecular dynamics simulations

In heme-containing proteins the heme group is usually non-covalently bound in a pocket. Molecular dynamics (MD) simulations have been performed to estimate the barrier height for heme-protein separation. In simulations of myoglobin dissolved in water, a force has been applied to pull the heme out of the binding pocket. With forces above 0.5 nN, the heme group is easily pulled out of the pocket in times of the order of tens of picoseconds. With weaker forces, heme release becomes too slow to be monitored in an MD simulation covering a couple of hundred picoseconds. These results are consistent with a free energy barrier to heme release of about 100 kJ/mol. The results show that the main energetic change that occurs during the release is a conversion of heme/protein Lennard-Jones energy into heme/water Lennard-Jones energy. The release is essentially barrierless in energy indicating that the main part of the barrier is entropic

Black holes, gravitational waves and fundamental physics: a roadmap

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'

Linograms

The several successful solutions to the problem of image reconstruction from projections have caused a rapid growth of a number of new techniques for the reconstruction of distributions and images in several scientific fields. The importance of these techniques, especially in medicine, can hardly be overestimated. In a new algorithm for image reconstruction from projections [l, 2], a special form of the projection data is employed providing some certain advantages. This new form or map of the projection data are called linograms. This is intended as an overview of linograms and the algorithm based on them. Thorough discussions of conventional techniques are to be found in [3, 4 and 5]. In conventional techniques for image reconstruction, a two dimensional distribution of some property is reconstructed. The property might be the x-ray attenuation in a cross-section of the body, the distribution of a radioactive substance or something else. The distribution is not directly accessible but it is possible to measure line integrals (rays) through i t. The problem now is to reconstruct the distribution (the image) from i ts line integrals (its projections). Let the property we are interested in be described by the function f(x, y). projection data are estimates of line integrals of f of known location. Incon~entional techniques each line is specified by two parameters s and e, where s is the (signed) distance from the origin and e its angle with the y-axis

Praktisk tomografi

De basala principerna och geometrin för tomografi genomgås kortfattat, samt hur tomogrammet uppkommer. Avbildning av föremål i skiktet demonstreras och varför de avbildas med sämre skärpa och kontrast än vanliga bilder, men också hur tomogrammet kan visa mer av föremålen än vanliga bilder. Sedan redogörs för hur föremål utanför skiktet i olika. grad kan suddas ut genom den tomografiska rörelsoskärpan. För- och nackdelar med olika tomorörelser diskuteras liksom indikationer för när och hur man skall tomografera, samt hur man skall välja vinkel, rörelseform, rörelseriktning, bilder och snittval

Praktisk tomografi

De basala principerna och geometrin för tomografi genomgås kortfattat, samt hur tomogrammet uppkommer. Avbildning av föremål i skiktet demonstreras och varför de avbildas med sämre skärpa och kontrast än vanliga bilder, men också hur tomogrammet kan visa mer av föremålen än vanliga bilder. Sedan redogörs för hur föremål utanför skiktet i olika. grad kan suddas ut genom den tomografiska rörelsoskärpan. För- och nackdelar med olika tomorörelser diskuteras liksom indikationer för när och hur man skall tomografera, samt hur man skall välja vinkel, rörelseform, rörelseriktning, bilder och snittval

The Linogram Algorithm and Direct Fourier Method with Linograms

The conventionai map of projection data will here be called the sinogram map. Among the algorithms used with this map of data there are two of main interest for this paper: the Filtered Back Projection (FBP) and the Direct Fourier Method (DFM). FBP is the most popular algorithm used in commercial eT machines although it is computationally expensive compared to the DFM. The reason for its popularity is that FBP gives better pictures than the DFM uniess the lat ter is used with very careful interpolations. In this paper another map of projection data will be presented, here called the linogram map. The FBP may be implemented with this map in a particularly simple way, here called the Linogram Algorithm (LA). In this the back projection, which is so computationally expensive with the sinogram map, can be reduced to a computationally inexpensive series of FFT's.In the printed version the ISSN 0348-7679 is incorrect. The correct ISSN is 1102-1799

Rekonstruktion av saknade projektioneri datortomografi

Vid datortomografi besväras de rekonstruerade bilderna ofta av störande artefakter, dvs strukturer i bilden som inte motsvarar strukturer i patienten. Det finns många olika orsaker till artefakter och en viktig orsak är att vissa projektioner saknas helt eller delvis eller är av otillräcklig kvalitet. Delar av projektioner kan exempelvis saknas när implantat av metallproteser eller plomber i tänderna skymmer anatomin för de projicerande strålarna. Saknade projektioner av ena eller andra slaget ger upphov till artefakter i form av raka linjer som störande breder ut sig över hela bilden, ofta på ett sådant sätt att bilden blir otjänlig för sitt ändamål. I detta projekt har vi valt att studera en möjlighet att rekonstruera så mycket av de projektioner som saknas i ett visst vinkelavsnitt, att de inte längre ger upphov till störande artefakter. Arbetet har utförts med simulerade modellförsök. Vi har antagit en skiva i anatomin som avbildats med datortomografi med användande av parallellprojektioner. Försök har gjorts där enstaka projektioner saknas, och där projektioner saknas inom ett större vinkelavsnitt. Vid beskrivningen av vår metod skall vi först ge en verbal beskrivning och därpå en matematisk

Reconhecimento entre estados. Sobre a base moral das relações internacionais

Contrariamente à percepção cotidiana de que os atores estatais têm como objetivo de suas ações o respeito e o reconhecimento da comunidade por eles representada, prevalece na moderna teoria predominante das relações internacionais a noção de que os governos nacionais orientam seu agir essencialmente a fins e não com base em princípios morais. O texto destaca as razões que falam a favor de uma maior consideração da dimensão do reconhecimento na explicação das relações internacionais e explora as implicações normativas que surgem a partir de tal mudança de paradigma para a compreensão e o tratamento das relações internacionais. Narrativas justificadoras da ação política recebem aqui um papel destacado