Gas-liquid phase separation in oppositely charged colloids: stability and interfacial tension

We study the phase behavior and the interfacial tension of the screened Coulomb (Yukawa) restricted primitive model (YRPM) of oppositely charged hard spheres with diameter s using Monte Carlo simulations. We determine the gas-liquid and gas-solid phase transition using free energy calculations and grand-canonical Monte Carlo simulations for varying inverse Debye screening length k. We find that the gas-liquid phase separation is stable for k s <= 4, and that the critical temperature decreases upon increasing the screening of the interaction (decreasing the range of the interaction). In addition, we determine the gas-liquid interfacial tension using grand-canonical Monte Carlo simulations. The interfacial tension decreases upon increasing the range of the interaction. In particular, we find that simple scaling can be used to relate the interfacial tension of the YRPM to that of the restricted primitive model, where particles interact with bare Coulomb interactions.Comment: 17 pages, 6 Figures, accepted for publication in J. Chem. Phy

Re-entrant melting and freezing in a model system of charged colloids

We studied the phase behavior of charged and sterically stabilized colloids using confocal microscopy in a less polar solvent (dielectric constant 5.4). Upon increasing the colloid volume fraction we found a transition from a fluid to a body centered cubic crystal at 0.0415+/-0.0005, followed by re-entrant melting at 0.1165+/-0.0015. A second crystal of different symmetry, random hexagonal close-packed, was formed at a volume fraction around 0.5, similar to that of hard spheres. We attribute the intriguing phase behavior to particle interactions that depend strongly on volume fraction, mainly due to changes in the colloid charge. In this low polarity system the colloids acquire charge through ion adsorption. The low ionic strength leads to fewer ions per colloid at elevated volume fractions and consequently a density-dependent colloid charge.Comment: 25 pages, 5 figures 1 tabl

Geografiska data i nationell informationsled

Kansallisen Palveluarkkitehtuurin (KaPA) puitteissa on määritelty palvelujen harmonisointiin ja yhteentoimivuuteen tähtääviä periaatteita mm. tiedonsiirtoon, käyttäjätunnistukseen, käyttöliittymiin ja palvelujen metatietoihin liittyen. Osana valtionhallinnon tietoarkkitehtuurin kehittämistä on tehty päätös ottaa käyttöön hallinnon sähköisten palvelujen hyödyntämistä tukeva palveluväylä (Suomi.fi-palveluväylä). Paikkatietoaineistot muodostavat yhden keskeisen tietovarannon, joka olisi tärkeää kytkeä palveluväylän kautta sovellusten saavutettavaksi. Paikkatietoihin liittyen on kehitetty yhteisiä standardeja tukevia palvelutoteutuksia viime vuosien aikana monissa eri organisaatioissa osana INSPIRE-prosessia tukevaa kansallisen paikkatietoinfrastruktuurin rakentamista. Haasteena nykytilanteessa on erityisesti se, miten voitaisiin sovittaa yhteen paikkatietoalan jo vakiintuneet yhteentoimivuuskäytännöt ja KaPA:n mukaiset sähköisten palvelujen toimintaperiaatteet. Olemassa olevien INSPIRE/OGC-yhteensopivien palvelujen näkökulmasta katsoen Suomi.fi -palveluväylä tulee nähdä mahdollisuutena paikkatietojen hyödyntämiseen uuden tyyppisissä sovelluksissa ja uusilla sovellusalueilla. Hankkeessa kehitetyn sovitinpalvelun avulla operatiivinen INSPIRE/ OGC-yhteensopiva rajapintapalvelu voidaan liittää palveluväylään ilman, että ao. palveluun tarvitsee tehdä mitään muutoksia. Luontevimmin Suomi.fi-palveluväylään kytkettäviksi soveltuvat INSPIRE kyselypalvelut ja OGC Web Feature Service (WFS) -palvelut. Avoimien tietoaineistojen ja palvelujen osalta on tärkeää, että niiden tuottama tietosisältö olisi KaPA-palvelujen hyödynnettävissä myös ilman kytkeytymistä Suomi.fi-palveluväylään. Palveluväylään liittymisen kustannusvaikutukset voivat olla tiedontuottajaorganisaatioille merkittäviä – erityisesti kiristyneiden palvelutasovaatimusten takia. On tärkeää, että KaPA:n tarjoamien tukipalveluiden hinnoittelu ei muodostu esteeksi niiden laajamittaiselle käyttöönotoll

Systemic Dosing of Thymosin Beta 4 before and after Ischemia Does Not Attenuate Global Myocardial Ischemia-Reperfusion Injury in Pigs

The use of cardiopulmonary bypass (CPB) and aortic cross-clamping causes myocardial ischemia-reperfusion injury (I-RI) and can lead to reduced postoperative cardiac function. We investigated whether this injury could be attenuated by thymosin beta 4 (TB4), a peptide which has showed cardioprotective effects. Pigs received either TB4 or vehicle and underwent CPB and aortic cross-clamping for 60 min with cold intermittent blood-cardioplegia and were then followed for 30 h. Myocardial function and blood flow was studied by cardiac magnetic resonance and PET imaging. Tissue and plasma samples were analyzed to determine the amount of cardiomyocyte necrosis and apoptosis as well as pharmacokinetics of the peptide. In vitro studies were performed to assess its influence on blood coagulation and vasomotor tone. Serum levels of the peptide were increased after administration compared to control samples. TB4 did not decrease the amount of cell death. Cardiac function and global myocardial blood flow was similar between the study groups. At high doses a vasoconstrictor effect on mesentery arteries and a vasodilator effect on coronary arteries was observed and blood clot firmness was reduced when tested in the presence of an antiplatelet agent. Despite promising results in previous trials the cardioprotective effect of TB4 was not demonstrated in this model for global myocardial I-RI.Peer reviewe

S-ketamine in patient-controlled analgesia reduces opioid consumption in a dose-dependent manner after major lumbar fusion surgery: A randomized, double-blind, placebo-controlled clinical trial

Background Spinal fusion surgery causes severe pain. Strong opioids, commonly used as postoperative analgesics, may have unwanted side effects. S-ketamine may be an effective analgesic adjuvant in opioid patient-controlled analgesia (PCA). However, the optimal adjunct S-ketamine dose to reduce postoperative opioid consumption is still unknown.Methods We randomized 107 patients at two tertiary hospitals in a double-blinded, placebo-controlled clinical trial of adults undergoing major lumbar spinal fusion surgery. Patients were randomly allocated to four groups in order to compare the effects of three different doses of adjunct S-ketamine (0.25, 0.5, and 0.75 mg ml-1) or placebo on postoperative analgesia in oxycodone PCA. Study drugs were administered for 24 hours postoperative after which oxycodone-PCA was continued for further 48 hours. Our primary outcome was cumulative oxycodone consumption at 24 hours after surgery.Results Of the 100 patients analyzed, patients receiving 0.75 mg ml(-1) S-ketamine in oxycodone PCA needed 25% less oxycodone at 24 h postoperatively (61.2 mg) compared with patients receiving 0.5 mg ml(-1) (74.7 mg) or 0.25 mg ml(-1) (74.1 mg) S-ketamine in oxycodone or oxycodone alone (81.9 mg) (mean difference: -20.6 mg; 95% confidence interval [CI]: -41 to -0.20; P = 0.048). A beneficial effect in mean change of pain intensity at rest was seen in the group receiving 0.75 mg ml(-1) S-ketamine in oxycodone PCA compared with patients receiving lower ketamine doses or oxycodone alone (standardized effect size: 0.17, 95% CI: 0.013-0.32, P = 0.033). The occurrence of adverse events was similar among the groups.Conclusions Oxycodone PCA containing S-ketamine as an adjunct at a ratio of 1: 0.75 decreased cumulative oxycodone consumption at 24 h after major lumbar spinal fusion surgery without additional adverse effects

Effect of Inhaled Xenon on Cardiac Function in Comatose Survivors of Out-of-Hospital Cardiac Arrest—A Substudy of the Xenon in Combination With Hypothermia After Cardiac Arrest Trial

OBJECTIVES: This explorative substudy aimed at determining the effect ofinhaled xenon on left ventricular function by echocardiography in comatose survivorsof out-of-hospital cardiac arrest.DESIGN: A randomized two-group single-blinded phase 2 clinical drug trial.SETTING: A multipurpose ICU in two university hospitals.PATIENTS: Of the 110 randomized comatose survivors after out-of-hospital cardiacarrest with a shockable rhythm in the xenon in combination with hypothermiaafter cardiac arrest trial, 38 patients (24–76 yr old) with complete echocardiographywere included in this study.INTERVENTIONS: Patients were randomized to receive either inhaled xenoncombined with hypothermia (33 C) for 24 hours or hypothermia treatment alone.Echocardiography was performed at hospital admission and 24 4 hours afterhypothermia.MEASUREMENTS AND MAIN RESULTS: Left ventricular ejection fraction,myocardial longitudinal systolic strain, and diastolic function were analyzedblinded to treatment. There were 17 xenon and 21 control patients in whom echocardiographywas completed. Clinical characteristics did not differ significantlybetween the groups. At admission, ejection fraction was similar in xenon and controlpatients (39% 10% vs 38% 11%; p = 0.711) but higher in xenon thancontrol patients after hypothermia (50% 10% vs 42% 10%; p = 0.014).Global longitudinal systolic strain was similar in xenon and control patients atadmission (–9.0% 3.8% vs –8.1% 3.6%; p = 0.555) but better in xenonthan control patients after hypothermia (–14.4.0% 4.0% vs –10.5% 4.0%;p = 0.006). In patients with coronary artery disease, longitudinal strain improved inthe nonischemic myocardial segments in xenon patients. There were no changesin diastolic function between the groups.</p

Implicit-solvent Models for Micellization of Ionic Surfactants

We propose a method for parameterization of implicit-solvent models for the simulation of self-assembly of ionic surfactants into micelles. The parameterization is carried out in two steps. The first step involves atomistic Molecular Dynamics simulations of headgroups and counterions with explicit solvent to determine structural properties. An implicit-solvent model of the headgroup/counterion system is ob- tained by matching structural quantities between explicit-solvent and implicit-solvent systems. In the second step we identify the solvophobic attractions between the tail beads. We determine the solvophobic parameters using Grand Canonical Monte Carlo simulations with histogram reweighting techniques. The matching objective for the identification of solvophobic attractions is the critical micelle concentration (cmc). We chose sodium dodecyl sulfate as the reference system. Based on hydrophobic parameters obtained from this particular model we study specific ion effects (lithium and potassium instead of sodium), as well as the effect of cationic headgroups (dodecyltrimethylammonium bromide/chloride). Furthermore, the chain length dependence of micellization properties is investigated for sodium alkyl sulfate, with alkyl lengths between 6 and 14. All cases considered give results in broad agreement to experimental data, confirming transferability of parameters and the generality of the approach