Kui ohtlik on sinine valgus silmadele?

Sinise valguse ohtlikkuse kohta on viimastel aastatel avaldatud palju teavet ja selle valguse toksilisus silma võrkkesta suhtes on teaduslikult tõestatud. Kahjustuse tekkemehhanismidest peetakse olulisemateks võrkkesta pigmentepiteeli ja fotoretseptorite kahjustust ning oksüdatiivset stressi. Sinise valguse kumulatiivset toksilisust pole veel näidatud, kuid potentsiaalselt on see ohtlik ning võib viia maakuli ealise degeneratsiooni tekkeni. Aktuaalseks teeb teema see, et tavainimese ekspositsioon lühikesele lainepikkusele on seoses nutitelefonide ja tahvelarvutite ning säästlike sisevalgustusvahendite kasutuselevõtuga suurenenud. Samas ei ole sellise valguse tervisemõjud ja -riskid laias laastus teada. Artiklis on käsitletud eelkõige loomkatsetest saadud infot ning kirjeldatud sinise valguse võimalikku mõju silmadele ja silmahaiguste tekkele.Eesti Arst 2018; 97(1):21–2

A two-agent model of sequential search and choice

This paper extends the standard sequential search model by allowing the agent who compiles the choice set via search (the “searcher”) to differ from the agent who chooses from the set (the “chooser”). I show for a general joint distribution of the agents’ preferences that the searcher's optimal policy is a threshold rule. In contrast to the standard model, the threshold is weakly decreasing in time (i.e., exhibits the “discouragement effect”), although the search horizon is infinite and the search environment stationary. I characterise the threshold and discuss the testable implications of the discouragement effect. The characteristics of my model differ from two single-agent search models that feature a time-varying threshold (convex search costs or deadline). In particular, my model features a threshold that decreases endogenously over time and never generates return to an item rejected earlier, in contrast to the other models

Evolutionary stable matching and pricing : comparisons of a symmetric and asymmetric markets

Only abstract. Paper copies of master’s theses are listed in the Helka database (http://www.helsinki.fi/helka). Electronic copies of master’s theses are either available as open access or only on thesis terminals in the Helsinki University Library.Vain tiivistelmä. Sidottujen gradujen saatavuuden voit tarkistaa Helka-tietokannasta (http://www.helsinki.fi/helka). Digitaaliset gradut voivat olla luettavissa avoimesti verkossa tai rajoitetusti kirjaston opinnäytekioskeilla.Endast sammandrag. Inbundna avhandlingar kan sökas i Helka-databasen (http://www.helsinki.fi/helka). Elektroniska kopior av avhandlingar finns antingen öppet på nätet eller endast tillgängliga i bibliotekets avhandlingsterminaler.This thesis analyses the evolutionary stability of different matching and pricing mechanisms. The aim of the thesis is to determine the evolutionary stable structure of an economy where buyers and sellers have a choice between a symmetric random matching and an asymmetric efficient matching market that differ in pricing mechanisms. Additionally, a stability property of an asymmetric market, where buyers differ in their possibility of meeting a seller, is studied. Two efficient markets with different pricing mechanisms are compared to a random matching market where prices are set by auctions. All the possible matches are made in the efficient markets. In the first comparison, prices are set by bargaining in the efficient market. In the other efficient market, prices are set via altered auctions. In neither of the comparisons can the random matching and an efficient matching market function simultaneously in an evolutionary stable equilibrium configuration. In the first comparison, the asymmetric efficient bargaining market structure is evolutionary stable if the ratio of buyers to sellers in the economy is small. The random matching market with auctions is evolutionary stable if the ratio is large. For intermediate values of the ratio, the starting state of the economy determines the stable equilibrium that the economy reaches. In the second comparison, the efficient market with altered auctions is always evolutionary stable over the random matching market with standard auctions. An asymmetric market is analysed further, by treating efficiently matched and consumers without the advantage of a determinate match separately, to determine the share of sellers that choose to serve consumers restricted from certain matching. The results show that the determinate matching market breaks down at a quite low ratio of restricted buyers to matched buyers. The evolutionary stability of different equilibrium pricing mechanisms in a random matching setting has been studied earlier. Lu and McAfee (1996) and Halko et al. (2007) respectively show that auctions are the evolutionary stable pricing mechanism when compared to bargaining or altered auctions. Kultti and Takalo (1999) demonstrate that auctions retain their superiority over bargaining if agents can choose to search or wait. The thesis uses a mathematical model to depict the economy, that is markedly similar to models of the abovementioned authors. The specifications of the matching and the pricing procedures are from search-theoretic models. The equilibrium selection criterion is the evolutionary stability of an equilibrium, which comes from evolutionary game theory. Replicator dynamics are applied to depict dynamic adjustment processes and to determine evolutionary stable equilibria in the comparisons

Isiklik müük

http://www.ester.ee/record=b1053328*es

Essays in search theory

This thesis consists of three papers on search theory. Chapter 2 studies stationary cutoff-strategy equilibria of a dynamic market model where buyers sample sellers sequentially from an unknown distribution. Buyers learn about the distribution from the sampled sellers and a private "trade signal". The trade signal reveals whether a randomly chosen seller traded yesterday. The signal's precision and the market distribution of options are determined in equilibrium. Observing a trade (as opposed to no trade) is good news about the distribution. Buyers who observe a trade use a higher cutoff than buyers who observe no trade, despite buyers' learning from sampled sellers that puts a countervailing pressure on the cutoffs. The trade signal may reduce market effciency, while an appropriate exogenous signal increases effciency. Chapter 3 extends the standard sequential search model by allowing the agent who inspects items sequentially (the "searcher") to differ from the agent who chooses from the set of inspected items (the "chooser"). I show for a general joint distribution of the agents' preferences that the searcher's optimal policy is a cutoff rule. The cutoff is weakly decreasing in time, i.e., exhibits the "discouragement effect". I characterise the cutoff and discuss some testable implications of the discouragement effect. Chapter 4 relaxes the standard sequential search model's assumption that the searching agent makes no choice mistakes. In my model, once the agent stops the search process, she chooses the best inspected item with probability 1-ε and uniformly among the remaining inspected items with probability ε. I show that her optimal policy is a stochastic cutoff rule and that she may both experience regret and search longer than an agent who makes no mistakes

Keratiidi-ihtüoosi-kurtuse sündroomi (KID) keratiidi uus ravivõimalus – haigusjuhu kirjeldus

Keratiidi-ihtüoosi-kurtuse sündroom ehk KID-sündoom (ingl keratitis-ichtyosisdeafness syndrome) on haruldane kaasasündinud ektodermaalne häire, mida iseloomustab nägemist ohustav sarvkesta epiteeli defektidest põhjustatud haavandumine ning vaskularisatsioon, kurtus ning erineva raskusastmega ihtüoos. Haigus võib juba varases lapseeas ohustada nägemist ning koos kuulmislangusega põhjustada olulise arengumahajäämuse. Spetsiifilist ravi KID-sündroomile ei ole, seetõttu on patsiendi multidistsiplinaarne käsitlus sümptomaatilise ravi määramise eesmärgil möödapääsmatu. Artiklis on esitatud KID-sündroomi keratiidi seni kirjeldamata ravivõimalus maatriksi regeneratsiooniteraapia ühenditega (ingl ReGeneraTing Agent, RGTA) ühe haigusjuhu näitel. Maatriksi regeneratsiooniteraapia ühendid on suhteliselt uus rühm ravimeid, mida kasutatakse eeskätt krooniliste sarvkestahaavandite raviks ning mis ideaalsel juhul viib kudede täieliku taastumiseni. Eesti Arst 2018; 97(8):433–43

Physicochemical properties of blue fluorescent protein determined via molecular dynamics simulation

Blue fluorescent protein (BFP) is a mutant of green fluorescent protein (GFP), where the chromophore has been modified to shift the emitted fluorescence into the blue spectral region. In this study, MD calculations were performed with the GROMACS simulation package and AMBER force field to investigate the dependence of BFPs physicochemical properties on temperature and applied pressure. The MD approach enabled us to calculate the compressibility of protein itself, separately from the nontrivial contribution of the hydration shell, which is difficult to achieve experimentally. The computed compressibility of BFP (3.94 ×10 −5 MPa −1 ) is in agreement with experimental values of globular proteins. The center-of-mass diffusion coefficient of BFP and its dependence on temperature and pressure, which plays an important role in its application as a probe for intracellular liquid viscosity measurement, was calculated and found to be in good agreement with photobleaching recovery experimental data. We have shown that decreased temperature as well as applied pressure increases the water viscosity, but the concomitant decrease of the BFP diffusion coefficient behaves differently from Stokes-Einstein formula. It is shown that the number of hydrogen bonds around the protein grows with pressure, which explains the aforementioned deviation. Pressure also reduces root mean square (RMS) fluctuations, especially those of the most flexible residues situated in the loops. The analysis of the RMS fluctuations of the backbone C Α atoms also reveals that the most rigid part of BFP is the center of the Β-barrel, in accord with temperature B factors obtained from the Protein Data Bank. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 1136–1143, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at [email protected] Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61210/1/21065_ftp.pd

Lehrtexte für Biologen : Mit Übungen

https://www.ester.ee/record=b1325422*es

Performance of Heat Recovery Ventilation System with Ground Source Brine Heat Exchanger Pre-Heating System in the Context of nZEB

The paper analyzes effectiveness of the ventilation unit pre-heating system with a ground source brine heat exchanger in a nearly zero energy building in Estonia. Focus is on the analysis of measured energy usage and possible effects on the energy usage of alternative solutions of the ventilation pre-heating system in terms of nearly zero energy building. The studied building was planned and realized according to the international passive house concept. To further lower the energy demand, the building was equipped with a solar thermal system and a photovoltaic solar system to cover the total final energy demand of the building, making it nearly zero energy building. The ventilation system is equipped with temperature and relative humidity sensors to measure supply, extract, exhaust air parameters and air parameters before and after the pre-heating system. Energy usage to pre-heat the ventilation airflow with a ground source brine heat exchanger was also measured. Our results show that annual energy used for pre-heating the ventilation airflow is around 420 kWh, which makes about 3% of the building’s total energy usage. The efficiency of the ventilation unit heat exchanger was over 80 % in the winter season due to the pre-heating system