Blockkedjeteknik

Blockkedjan, tekniken bakom Bitcoin och populariserad i dess introduktion, fungerar som en distribuerad databas och en publik huvudbok för transaktioner. Blockkedjetek-niken har även andra implementeringar och användningsområden än endast Bitcoin. Syftet med arbetet är att beskriva blockkedjetekniken och några typiska blockkedjetilllämpningar. I detta arbete presenteras blockkedjans struktur och säkerhet, publika, privata och tillståndsbelagda blockkedjor samt bevis på arbete, bevis på andel och andra konsensusmekanismer. Vidare beskrivs olika blockkedjor för kryptovalutor och andra implementeringar såsom smarta kontrakt, verifiering och medieadministration. Som källmaterial har använts artiklar och vitböcker publicerade på Internet. Programmering har utförts med Multichain för implementering av en privat blockkedja och samt med Blockcerts för digitala betyg. Blockkedjetekniken har redan många användningsområden samt nya förslag och idéer duggar tätt. Bitcoin riskerar dock att hamna i bakgrunden på grund av dess användares motvillighet att ta i bruk nyare, snabbare och mer funktionsrika blockkedjeimplementeringar.The blockchain, the technology behind Bitcoin and popularized in its introduction, functions as a distributed database and a public ledger for transactions. Blockchain technology has also other implementations and applications than Bitcoin. The purpose of this thesis work is to describe blockchain technology and some typical blockchain applications. In this thesis work is presented the structure and security of a blockchain, public, private, and permissioned blockchains as well as proof of work, proof of stake, and other consensus mechanisms. Different blockchains for crypto currency and other implementations such as smart contracts, verification, and media administration are also described. Literature sources are articles and white papers published on the Internet. Programming has been carried out with Multichain to implement a private blockchain and with Blockcerts for digital certificates. Blockchain technology has already many application areas and new suggestions and ideas are streaming in. Bitcoin itself risks falling behind due to its users’ reluctance to deploy newer, faster and more feature rich block-chain implementations

Structure and function of negative feedback loops at the interface of genetic and metabolic networks

The molecular network in an organism consists of transcription/translation regulation, protein-protein interactions/modifications and a metabolic network, together forming a system that allows the cell to respond sensibly to the multiple signal molecules that exist in its environment. A key part of this overall system of molecular regulation is therefore the interface between the genetic and the metabolic network. A motif that occurs very often at this interface is a negative feedback loop used to regulate the level of the signal molecules. In this work we use mathematical models to investigate the steady state and dynamical behaviour of different negative feedback loops. We show, in particular, that feedback loops where the signal molecule does not cause the dissociation of the transcription factor from the DNA respond faster than loops where the molecule acts by sequestering transcription factors off the DNA. We use three examples, the bet, mer and lac systems in E. coli, to illustrate the behaviour of such feedback loops.Comment: 8 pages, 4 figure

Genome editing in potato via CRISPR-Cas9 ribonucleoprotein delivery

Clustered regularly interspaced short palindromic repeats and CRISPR-associated protein-9 (CRISPR-Cas9) can be used as an efficient tool for genome editing in potato (Solanum tuberosum). From both a scientific and a regulatory perspective, it is beneficial if integration of DNA in the potato genome is avoided. We have implemented a DNA-free genome editing method, using delivery of CRISPR-Cas9 ribonucleoproteins (RNPs) to potato protoplasts, by targeting the gene encoding a granule bound starch synthase (GBSS, EC 2.4.1.242). The RNP method was directly implemented using previously developed protoplast isolation, transfection and regeneration protocols without further adjustments. Cas9 protein was preassembled with RNA produced either synthetically or by in vitro transcription. RNP with synthetically produced RNA (cr-RNP) induced mutations, i.e. indels, at a frequency of up to 9%, with all mutated lines being transgene-free. A mutagenesis frequency of 25% of all regenerated shoots was found when using RNP with in vitro transcriptionally produced RNA (IVT–RNP). However, more than 80% of the shoots with confirmed mutations had unintended inserts in the cut site, which was in the same range as when using DNA delivery. The inserts originated both from DNA template remnants from the in vitro transcription, and from chromosomal potato DNA. In 2–3% of the regenerated shoots from the RNP-experiments, mutations were induced in all four alleles resulting in a complete knockout of the GBSS enzyme function.Fil: Andersson, Mariette. Swedish University Of Agricultural Sciences; SueciaFil: Turesson, Helle. Swedish University Of Agricultural Sciences; SueciaFil: Olsson, Niklas. Swedish University Of Agricultural Sciences; SueciaFil: Fält, Ann Sofie. Swedish University Of Agricultural Sciences; SueciaFil: Ohlsson, Pia. Swedish University Of Agricultural Sciences; SueciaFil: Gonzalez, Matías Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Samuelsson, Mathias. Lyckeby Starch AB; SueciaFil: Hofvander, Per. Swedish University Of Agricultural Sciences; Sueci

Novel Technique for Ultra-sensitive Determination of Trace Elements in Organic Scintillators

A technique based on neutron activation has been developed for an extremely high sensitivity analysis of trace elements in organic materials. Organic materials are sealed in plastic or high purity quartz and irradiated at the HFIR and MITR. The most volatile materials such as liquid scintillator (LS) are first preconcentrated by clean vacuum evaporation. Activities of interest are separated from side activities by acid digestion and ion exchange. The technique has been applied to study the liquid scintillator used in the KamLAND neutrino experiment. Detection limits of <2.4X10**-15 g 40K/g LS, <5.5X10**-15 g Th/g LS, and <8X10**-15 g U/g LS have been achieved.Comment: 16 pages, 3 figures, accepted for publication in Nuclear Instruments and Methods

Interstellar polarization and grain alignment: the role of iron and silicon

We compiled the polarimetric data for a sample of lines of sight with known abundances of Mg, Si, and Fe. We correlated the degree of interstellar polarization $P$ and polarization efficiency (the ratio of $P$ to the colour excess $E(B-V)$ or extinction $A_V$) with dust phase abundances. We detect an anticorrelation between $P$ and the dust phase abundance of iron in non silicate - containing grains ]_\rm d, a correlation between $P$ and the abundance of Si, and no correlation between $P/E(B-V)$ or $P/A_V$ and dust phase abundances. These findings can be explained if mainly the silicate grains aligned by the radiative mechanism are responsible for the observed interstellar linear polarization.Comment: Accepted for publication in Astronomy and Astrophysic

Roles of Cognitive Characteristics in Tinnitus Patients

To investigate the cognitive characteristics that affect the emotional and functional distress caused by tinnitus and to decide and test the model to explain their relations, 167 patients with tinnitus, who visited Samsung Medical Center, Seoul, Korea between March 2001 and May 2002 were recruited. To examine their features related to tinnitus, the following scales were administered; Tinnitus-related basic questionnaire including dysfunctional beliefs, Tinnitus Handicap Inventory, State-Trait Anxiety Inventory, Anxious Thought and Tendencies, Self-Consciousness Scale, and modified 'catastrophic thought' from Coping Strategies Questionnaire. The results showed that the duration of experiencing tinnitus was 4.7±7.1 yr, those who com-plained of hearing one sound were the most common (45.5%), and hearing sounds similarly described to whistling were the most common (22.5%). Also, there were significant correlations among tinnitus features, cognitive characteristics, and distresses from tinnitus. As a result of testing the model, Normed fit index, Incremental fit index, Tucker-Lewis index, and Comparative fit index were over .90, indicating that it is a good model, and Root mean square error of approximation showed a reasonable fit. Also, the direct effects of the trait or severity of tinnitus on distress did not appear to be significant, thus it appeared to be affecting indirectly through the cognitive characteristics. This result shows that cognitive interventions can be important for the psychological adaptations of tinnitus patients

Joint measurements and Bell inequalities

Joint quantum measurements of non-commuting observables are possible, if one accepts an increase in the measured variances. A necessary condition for a joint measurement to be possible is that a joint probability distribution exists for the measurement. This fact suggests that there may be a link with Bell inequalities, as these will be satisfied if and only if a joint probability distribution for all involved observables exists. We investigate the connections between Bell inequalities and conditions for joint quantum measurements to be possible. Mermin's inequality for the three-particle Greenberger-Horne-Zeilinger state turns out to be equivalent to the condition for a joint measurement on two out of the three quantum systems to exist. Gisin's Bell inequality for three co-planar measurement directions, meanwhile, is shown to be less strict than the condition for the corresponding joint measurement