Polyelectrolyte Assemblies: Fundamentals And Applications

Charged assemblies bearing opposite or complementary charges span natural (proteins, enzymes, DNA) to synthetic materials (surfactants, synthetic polyelectrolytes). Assembly is facilitated by electrostatic attraction and entropic release of counterions, and most often occurs in aqueous media. Notably decades ago, Michaels described synthetic polyelectrolyte complexes as brittle when dry but “leathery or rubberlike” when wet, which points to the strong effect of water on the mobility of a charged assembly. Here, the molecular origin of the glass transition is quantified for several charged macromolecular systems is investigated using calorimetry and molecular modeling as a function of water content. A general relationship is revealed as it holds for two completely different types of charged systems (pH- and salt-sensitive) and for both polyelectrolyte complexes and polyelectrolyte multilayers, which are made by different paths. This suggests that water facilitates the relaxation of charged assemblies by reducing attractions between oppositely charged intrinsic ion pairs. We further demonstrate the dual role of water and temperature in the dynamics of polyelectrolyte complexes by showing time-temperature and time-water superpositioning in a single polyelectrolyte complex system for the first time. With regard to applications, charged polymers can assemble with functional nanomaterials such as reduced graphene oxide or MXene sheets. These 2D nanomaterials are conductive, facilitating their application as sensors or electrodes for energy storage. Here, the nature of polyelectrolyte-2D nanomaterial assemblies is investigated as thin films. A reversibly stretchable MXene/polyelectrolyte strain sensor and humidity sensor is demonstrated, and the origin of this response is discussed. Also, mechanically robust graphene-based electrodes are presented as assemblies with nanoscale Kevlar

Rehevöityneen järven kunnostus ja hoito

Suomalainen järviluonto on monimuotoisuudessaan ainutlaatuista. Järvet ovat keskeinen osa suomalaista maisemaa ja identiteettiä. Vaikka järviin kohdistuva jätevesikuormitus on viime vuosikymmeninä tuntuvasti vähentynyt, on maassamme edelleen noin 1500 kunnostuksen tarpeessa olevaa järveä. Rehevöityminen heikentää järven vedenlaatua ja ekologista tilaa, sekä haittaa järven virkistyskäyttöä.Monien rehevien järvien kunnostustarve on tunnistettu vuonna 2009 hyväksytyissä alueellisissa vesienhoidon toimenpideohjelmissa. Suuri osa kunnostuksen tarpeessa olevista kohteista on kuitenkin pieniä ja niiden merkitys on luonteeltaan paikallinen. Järvien kunnostus edellyttääkin ensisijaisesti alueen asukkaiden, yritysten ja yhteisöjen aktiivista osallistumista ja yhteistyötä.Rehevöityneen järven tilaa voidaan parantaa kunnostus- ja hoitotoimenpiteiden avulla. Kunnostuksessa käytettävät menetelmät valitaan järven ongelmien ja kunnostukselle asetettujen tavoitteiden perusteella. Jos valuma-alueelta tuleva kuormitus on liian suurta, sen vähentäminen on kunnostuksen kannalta keskeistä. Eniten käytettyjä järvessä tehtäviä toimenpiteitä ovat ravintoketjukunnostus (hoitokalastus) ja hapetus sekä vesikasvien poisto, rantojen ruoppaus ja vedenpinnan nosto. Kunnostus on usein vesilain ja ympäristönsuojelulain perusteella luvanvaraista toimintaa. Myös luonnonsuojelulainsäädännön velvoitteet lajien ja elinympäristöjen turvaamisesta tulee ottaa huomioon, jotta kunnostuksella ei aiheuteta haittaa järviluonnon monimuotoisuudelle.Opas tarjoaa monipuolisen tietopaketin rehevöityneen järven kunnostuksesta ja hoidosta järvien tilasta kiinnostuneille kansalaisille, kansalaisjärjestöille ja päättäjille

Configuration of influenza hemagglutinin fusion peptide monomers and oligomers in membranes

AbstractThe 20 N-terminal residues of the HA2 subunit of influenza hemagglutinin (HA), known as the fusion peptide, play a crucial role in membrane fusion. Molecular dynamics simulations with implicit solvation are employed here to study the structure and orientation of the fusion peptide in membranes. As a monomer the α-helical peptide adopts a shallow, slightly tilted orientation along the lipid tail–head group interface. The average angle of the peptide with respect to membrane plane is 12.4 °. We find that the kinked structure proposed on the basis of NMR data is not stable in our model because of the high energy cost related to the membrane insertion of polar groups. Because hemagglutinin-mediated membrane fusion is promoted by low pH, we examined the effect of protonation of the Glu and Asp residues. The configurations of the protonated peptides were slightly deeper in the membrane but at similar angles. Finally, because HA is a trimer, we modeled helical fusion peptide trimers. We find that oligomerization affects the insertion depth of the peptide and its orientation with respect to the membrane: a trimer exhibits equally favorable configurations in which some or all of the helices in the bundle insert obliquely deep into the membrane

Sukupuolen vaikutus aivovaltimoaneurysman seinämän rappeutumiseen : vertaileva kliinispatologinen tutkimus naisten ja miesten aneurysmien seinämänrakenteesta

Aivovaltimoaneurysma (AA) on pullistuma aivovaltimon haarautumassa kallonpohjassa. AA:n puhkeaminen aiheuttaa lukinkalvonalaisen vuodon (SAV), joka on Suomessa yleisempi kuin muualla maailmassa. Naissukupuolen tiedetään olevan yksi SAV:n riskitekijöistä. Tässä tutkimuksessa etsitään yhteyttä AA:n seinämään kertyvän rasvan ja tämän hapettumisen sekä seinämän rappeutumisen välillä, kartoitetaan rasvan kertymiseen liittyvän seinämän rappeutumisen yhteyttä sukupuoleen sekä tutkitaan sukupuolen vaikutusta seinämän tulehdusreaktioon. Näytteisiin kertyneet rasvat värjättiin Oil-O-red värjäyksellä, oksidoituja LDL partikkeleita värjättiin anti-Ox-LDL vasta-aineella ja tulehdussolut tunnistettiin CD45 vasta-aineella. Aineistossamme seinämään kertyvällä rasvalla on yhteys seinämän rappeutumiseen. Vuotaneet ja vuotamattomat AA:t reagoivat eri tavalla hapettuneen LDL:n (Ox-LDL) kertymiseen. Naisten ja miesten ryhmät eroavat Ox-LDL:n kertymisen ja solutiheyden korrelaatioiden suhteen. Sukupuolten välillä on myös eroa Ox-LDL:n aiheuttamassa solutuhossa vuotaneissa aneurysmissa Myös naisten vuotaneiden ja vuotamattomien aneurysmien välillä on ero Ox-LDL:n seinämää rappeuttavassa vaikutuksessa. Näyttäisi siis, että vuotoherkillä naisten aneurysmilla on jokin Ox-LDL:n aiheuttamalle seinämätuholle altistava tekijä ja miehillä puhkeamiselle olisi muu syy

Molecular dynamics simulations of strained and defective carbon nanotubes

Carbon nanotubes are tubular molecules of pure carbon with typical diameters of 1 nm – 100 nm and lengths from 100 nm up to several cm. The nanotubes have outstanding electronical and mechanical properties which has resulted in remarkable scientific interest and in proporsals of various applications. For example, their ability to be either metals or semiconductors enables the usage of nanotubes as components of electronic devices, while excellent mechanical characteristics motivate the use of nanotubes as reinforcement agents in composite structures and in nanoelectromechanical devices. This thesis aims to contribute to the understanding of the mechanical properties of carbon nanotubes and it contains two parts. The first part concentrates on initially defect-free but strained nanotubes and on the deformations and defects induced by the strain. The employed methods are empirical and tight binding molecular dynamics simulations. As results the criteria for uniform and discontinuous buckling deformations are reported. In addition, defect formation and strain relaxation are discussed and the stability of various strained and deformed structures is assessed. The second part of the thesis evaluates defects as a means to improve the bulk mechanical properties of a nanotube sample. Defects, and irradiation as a method of inducing them, are proposed to improve mechanical load transfer between a nanotube and its surroundings. These proposals are verified by analytics and molecular dynamics simulations based on classical empirical potential. The load transfer between nanotubes is found to improve significantly in the presence of defects. This concept is extended to bundles of nanotubes where the improved tube-tube load transfer is predicted to increase shear and stiffen the bundle at moderate irradiation doses. The load transfer has great significance for reinforcement of polymer composites in which the nanotube bundles may act as reinforcement fibers. Furthermore, the mechanical degradation of individual tubes as a result of the defects is also assessed. Point defects have little effect on the axial stiffness of an individual tube but the tensile strength may decrease to a fraction of the strength for a perfect tube. Although individual tubes deteriorate in strength because of the defects, the results indicate that the overall mechanical properties of a nanotube sample can be significantly improved by imperfections in the structure of the tubes.reviewe

Akuutin umpilisäketulehduksen diagnostiikka : diagnostinen pisteytys ja leikkausta edeltävän viiveen merkitys

Background and aims: Diagnostic scoring is a method for stratifying patients according to the probability of appendicitis, and therefore works as an excellent basis for a diagnostic algorithm. This study aimed at developing a new diagnostic score, the Adult Appendicitis Score (AAS), and validating its routine use as an integral part of a new diagnostic algorithm. Diagnostic accuracy of the imaging studies depends on the pre-test probability of the disease. This study aimed to assess how accurate the imaging was in various AAS-stratified pre-test probability groups. The effect of in-hospital delay on the risk of perforation is controversial. The research in this thesis aimed to further clarify the matter. Patients and methods: The study enrolled 1737 patients with acute right lower quadrant abdominal pain. The first data collection of 829 patients was used to develop the AAS and compare it with two previously published scores as well as with the clinical assessment. The validation study of AAS enrolled 908 patients in two university hospitals. The negative appendectomy rate was compared between the first and second patient cohort. Patients that had diagnostic imaging were stratified into three probability-of-appendicitis groups according to the AAS, and the diagnostic accuracy of ultrasound (US) and computed tomography (CT) were compared between the score groups. To find the best marker to detect pre-hospital perforations, laboratory results and two previously published diagnostic scores were analyzed. The effects of total duration of symptoms, pre-hospital delay, and in-hospital delay on the risk of perforation were analyzed. Results: After the AAS was developed and incorporated into a new diagnostic algorithm the negative appendectomy rate decreased from 18.2% to 8.2%. With a specificity of 93%, the AAS stratified half of all patients with appendicitis into the high-probability group. The probability of appendicitis was only 7% for the low-probability group. The AAS outperformed both the clinical assessment and two previously published scores. The diagnostic accuracy of imaging depended on the pre-test probability of appendicitis. When compared to the two other groups allocated by the AAS, in the low-probability group a positive CT and US findings yielded lower post-test probability for appendicitis. More false than true positive US results were found in the low-probability group. C-reactive protein (CRP) was the best marker for pre-hospital perforation. For patients with CRP values less than 99 mg/l longer in-hospital delay increased the perforation risk whereas the duration of pre-hospital delay showed no difference between patients with uncomplicated and complicated appendicitis. For patients with CRP values 99 mg/l or more, the in-hospital delay did not increase the perforation risk. Conclusions: The AAS provides an accurate method to stratify patients according to their probability of appendicitis. After the score was implemented into clinical routine, it led to a dramatic reduction in the negative appendectomy rates. When the AAS stratifies the patient to have a low probability of appendicitis, the benefits of imaging are questionable. False positive imaging results can even induce negative appendectomies. Most perforations in acute appendicitis occur as pre-hospital events. However, some of the perforations can be avoided by minimizing the in-hospital delay.Akuutti umpilisäketulehdus on tavallinen äkillisen vatsakivun syy. Vaikka umpilisäketulehduksen oireet ovat hyvin tunnettuja, tehdään edelleen myös turhia leikkauspäätöksiä. Uuden, väitöstutkimuksen yhteydessä kehitetyn, diagnostisen pisteytyksen käyttöönoton havaittiin vähentävän merkittävästi turhien umpilisäkepoistojen osuutta. LL Henna Sammalkorven tuoreessa väitöstutkimuksessa kehitettiin uusi aikuisten potilaiden tutkimisessa hyödynnettävä diagnostinen pisteytys, Adult Appendicitis Score. Pisteytyksellä potilaat, joilla epäillään umpilisäketulehdusta, jaotellaan kolmeen ryhmään umpilisäketulehduksen todennäköisyyden mukaan. Uuden pisteytyksen kehittämistä varten prospektiivisesti kerätty aineisto sisälsi 829 Meilahden sairaalassa umpilisäkkeen tulehduksen epäilyn vuoksi tutkittua potilasta. Aiempaa tarkempi pisteytys luotiin analysoimalla potilaiden oireita, tutkimuslöydöksiä ja laboratoriokoevastauksia. Uusi pisteytys oli tarkempi kuin päivystävien kirurgien arvio tai kumpikaan vertailussa mukana olleista aiemmin julkaistusta pisteytyksistä. Pisteytys on otettu rutiinikäyttöön osana uutta umpilisäkkeen tulehduksen diagnostista ohjeistusta Meilahden sairaalassa. Pisteytyksen käytän vaikutusta diagnostiikan tarkkuuteen tutkittiin 908 potilaan aineistossa Meilahdessa ja Kuopion Yliopistollisessa Sairalassa. Ennen uuden pisteytyksen käyttöönottoa 18,2 prosentissa Meilahden sairaalassa umpilisäkkeen tulehduksen epäilyn vuoksi tehdyissä leikkauksissa umpilisäke ei ollut tulehtunut. Uuden pisteytyksen käyttöönoton jälkeen luku laski 8,2 prosenttiin , Henna Sammalkorpi kuvaa tilannetta. Uuden pisteytyksen ohella tutkimuksessa selvitettiin sairaalaan saapumisen ja umpilisäkkeen poiston välisen aikavälin vaikutusta puhkeamariskiin. Tutkimuksessaan LL Henna Sammalkorpi havaitsi, että umpilisäkkeen puhkeaman todennäköisyyttä parhaiten kuvaava muuttuja on C-reaktiivinen proteiini, CRP. Potilailla, joiden CRP oli yli 99 jo sairaalaan tullessa, ei sairaalassa aiheutunut viive lisännyt puhkeaman todennäköisyyttä, sillä umpilisäke oli todennäköisimmin jo puhjennut ennen sairaalaan tuloa. Niillä potilaista, joiden CRP oli alle 99 sairaalassa aiheutunut viive lisäsi puhkeamariskiä. Mikäli sairaalassaoloaika ennen leikkausta kasvoi alle 6 tunnista yli 12 tuntiin, puhkeamariski kaksinkertaistui. Näin ollen osalla potilaista puhkeama voidaan välttää tarjoamalla potilaille viivytyksetöntä diagnostiikkaa ja hoitoa

Interactions between polyelectrolytes mediated by ordering and orientation of multivalent non-spherical ions in salt solutions

Multivalent ions in solutions with polyelectrolytes (PE) induce electrostatic correlations that can drastically change ion distributions around the PEs and their mutual interactions. Using coarse-grained molecular dynamics simulations, we show how in addition to valency, ion shape and concentration can be harnessed as tools to control like-charged PE-PE interactions. We demonstrate a correlation between the orientational ordering of aspherical ions and how they mediate the effective PE-PE attraction induced by multivalency. The interaction type, strength, and range can thus be externally controlled in ionic solutions. Our results can be used as generic guidelines to tune the self-assembly of like-charged polyelectrolytes by variation of the characteristics of the ions

Performance of imaging studies in patients with suspected appendicitis after stratification with adult appendicitis score

Background: Diagnostic scoring is used to stratify patients with suspected appendicitis into three groups: high, intermediate, and low probability of appendicitis. The stratification can be used for selective imaging to avoid the harms of radiation without compromising diagnostic accuracy. The aim was to study how stratification by Adult Appendicitis Score affects diagnostic performance of imaging studies. Methods: Analysis of 822 patients who underwent diagnostic imaging for suspected appendicitis was made. Adult Appendicitis Score was used to stratify patients into groups of high, intermediate, and low probability of appendicitis. Diagnostic performance of computed tomography (CT) and ultrasound (US) was compared between these patient groups. Results: After scoring, pre-test probability of appendicitis ranged from 9-16% in low probability group to 75-79% in high probability group in patients who underwent US or CT. Post-test probability of appendicitis after positive CT was 99, 91, and 75% in high probability, intermediate probability and low probability groups, respectively, p <0.001. After positive US the respective probabilities were 95, 91 and 42%, p <0.001. Conclusion: Diagnostic imaging has limited value in patients with low probability of appendicitis according to Adult Appendicitis Score.Peer reviewe

Improving administrative effectiveness of lake management in the frames of River Basin Management Plans : Implementation Plan

Fresh waters make only 3% of the global water resources. Freshwater lakes, including reservoirs and ponds, are important elements for communities and their relevance is increasing. Lake ecosystems and their catchments have provided several societally valuable benefits and ecosystem services like shelter, drinking water, bathing water, food, a means of travel and wealth in a number of ways and allowed whole cultures to develop. Lakes have values associated with well-being and relaxation, their proximity has catalyzed rural development and been important in the regional socio-economic development. Lake districts are often very popular destinations for domestic and foreign tourism and visitors. Eutrophication and its ecological consequences, pollution, over abstraction and invasive species are serious threats and increase the need for restoration and management to prevent the potential adverse economic and social impacts. There is increasing evidence that lakes are affected by climate change. Lake management is for these reasons an important part of sustainable regional development as set by Lisbon and Gothenburg agreements. However, the most significant piece of legislation in response to the increasing threat of pollution and the increasing demand from the public for cleaner lakes, rivers and beaches and freshwater biodiversity, is the EU Water Framework Directive (WFD). This Directive is unique in that it sets out an established framework for the protection of all water bodies (including lakes) and for all EU member states to achieve good water ecological status by December 2015. This objective is likely to be achieved in slightly over half (53 %) of EU waters (A blueprint…, 2013) and, therefore, more effort need to be scheduled for the following 6-year periods of WFD. The economic values of attractive, clean lakes are well established. There is a rising appreciation of good quality lakes across Europe. More intensive lake protection through sharing good practices with European lake managers and the regional influencing bodies is critical if we want to improve the current quality of lakes in Europe and to build long term capacity for sustainable use of lakes

Microscopic structure of oxygen defects in gallium arsenide

Accurate total-energy pseudopotential methods are used to study the structures, binding energies, and local vibrational modes of various models for the Ga-O-Ga defect in GaAs. We find that the previously proposed models, OAs (an off-centered substitutional oxygen in arsenic vacancy) and OI (an oxygen atom occupying a tetrahedral interstitial site), are inconsistent with experimental data. We introduce a model, (AsGa)2−OAs (two arsenic antisites and one off-centered substitutional oxygen in arsenic vacancy), the properties of which are in excellent agreement with experimental characterizations.Peer reviewe