Atomistic and coarse-grained simulations reveal increased ice nucleation activity on silver iodide surfaces in slit and wedge geometries

Ice clouds can form at low and moderate supercooling through heterogeneous ice nucleation on atmospheric particles. Typically, the nucleation requires active sites with special chemical and physical properties, including surface topology and roughness. This paper investigates microscopic mechanisms of how combinations of confinement by the surface topology and lattice match induced by the surface properties can lead to enhanced ice nucleation. We perform molecular dynamics simulations using both atomistic and coarse-grained water models, at very low supercooling, to extensively study heterogeneous ice nucleation in slit-like and concave wedge structures of silver-terminated silver iodide (0001) surfaces. We find that ice nucleation is greatly enhanced by slit-like structures when the gap width is a near-integer multiple of the thickness of an ice bilayer. For wedge systems we also do not find a simple linear dependence between ice nucleation activity and the opening angle. Instead we observe strong enhancement in concave wedge systems with angles that match the orientations of ice lattice planes, highlighting the importance of structural matching for ice nucleation in confined geometries. While in the slit systems ice cannot grow out of the slit, some wedge systems show that ice readily grows out of the wedge. In addition, some wedge systems stabilize ice structures when heating the system above the thermodynamics melting point. In the context of atmospheric ice nucleating particles, our results strongly support the experimental evidence for the importance of surface features such as cracks or pits functioning as active sites for ice nucleation at low supercooling.Peer reviewe

Liquid Water and Interfacial, Cubic, and Hexagonal Ice Classification through Eclipsed and Staggered Conformation Template Matching

We propose a novel method based on template matching for the recognition of liquid water, cubic ice (ice Ic), hexagonal ice (ice Ih), clathrate hydrates, and different interfacial structures in atomistic and coarse-grained simulations of water and ice. The two template matrices represent staggered and eclipsed conformations, which are the building blocks of hexagonal and cubic ice and clathrate crystals. The algorithm is rotationally invariant and highly robust against imperfections in the ice structure, and its sensitivity for recognizing ice-like structures can be tuned for different applications. Unlike most other algorithms, it can discriminate between cubic, hexagonal, clathrate, mixed, and other interfacial ice types and is therefore well suited to study complex systems and heterogeneous ice nucleation.Peer reviewe

Atomistic Simulation of Ice Nucleation on Silver Iodide (0001) Surfaces with Defects

Small particles of silver iodide (AgI) are known to have excellent ice nucleating capabilities and have been used in rain seeding applications. It is widely believed that the silver-terminated (0001) surface of beta-AgI acts as a template for the basal plane of hexagonal ice. However, the (0001) surface of ionic crystals with the wurtzite structure is polar and will therefore exhibit reconstructions and defects. Here, we use atomistic molecular dynamics simulations to study how the presence of defects on AgI(0001) affects the rates and mechanism of heterogeneous ice nucleation at moderate supercooling at -10 degrees C. We consider AgI(0001) surfaces exhibiting vacancies, step edges, terraces, and pits and compare them to simulations of the corresponding ideal surface. We find that, while point defects have no significant effect on ice nucleation rates, step edges, terraces, and pits reduce both the nucleation and growth rates by up to an order of magnitude. The reduction of the ice nucleation rate correlates well with the fraction of the surface area around the defects where perturbations of the hydration layer hinder the formation of a critical ice nucleus.Peer reviewe

Imaging the real shape of nanoclusters in scanning force microscopy

A quantitative comparison between experiment and theory is given for the constant height mode imaging of metal nanoclusters in dynamic scanning force microscopy. We explain the fundamental mechanisms in the contrast formation with the help of the system Pd/MgO(001). The comparison shows that the shape and size of nanoclusters are precisely imaged due to the sharpness of the tip’s last nanometer. This quantitative comparison proves our previously proposed model for the contrast formation.Peer reviewe

Kymijoen länsihaaran kalankulun järjestäminen : Esiselvitys

Kymijoen vesistö on maamme suurimpia vesistöalueita ja se laskee kahden päähaaran kautta Suomenlahteen. Sen rakentamattomat jokiosuudet, suojeluhankkeet ja veden laadun parantuminen ovat mahdollistaneet joen alaosan (jokisuu-Anjalankoski) palautumisen merkittäväksi vaelluskalojen tuotantoalueeksi. Kymijoki on myös priorisoitu kansallisen kalatiestrategian kärkohteisiin. Kymijokeen kotiutetun Nevajoen lohikannan ja muiden vaelluskalojen kannalta merkityksellisimpiä suuhaaroja ovat vesivoimatuotantoon valjastetut itähaaraan kuuluvat Langinkoskenhaara ja Korkeakoskenhaara sekä länsihaaran kuuluva Ahvenkoskenhaara. Itähaaran voimalaitosten yhteydessä on kalojen nousun mahdollistavat kalatiet, mutta länsihaaran voimalaitoksista (Ahvenkoski ja Klåsarö) vaellusyhteyden puuttuvat. Kymijoen länsihaaran padot estävät vaelluskalakantojen parhaan mahdollisen tuotannon, sillä länsihaarassa sijaitsee merkittäviä vaelluskalojen poikastuotantoalueita ja toisaalta Kymijoen yläosan (yhtenäinen jokiuoma Anjalankoskelta joen haarautumiskohtaan asti) kaloja pyrkii vaeltamaan sekä alas- että nousuvaelluksellaan länsihaaran kautta. Kymijoen vaelluskalakantojen kestävä elvyttäminen on siten kytköksissä länsihaaran vaellusyhteyksien avautumiseen. Länsihaaran voimalaitoksia operoivan Helen Oy:n vetämässä hankkeessa selvitetään parhaat ja kustannustehokkaimmat vaihtoehdot kalan kulun järjestämiseksi Ahvenkosken ja Klåsarön voimalaitosten ohi vuosina 2017–2018. Tämän selvitystyön taustaksi Luonnonvarakeskus koosti tähän raporttiin yhteenvedon Kymijoen vaelluskalojen potentiaalisista tuotantoalueista, vaellusyhteyksistä, vaelluskalakantojen tilasta sekä niihin liittyvistä tutkimuksista ja seurannoista. Lisäksi Luonnonvarakeskus arvioi Kymijoen länsihaaran vaellusyhteyksien sekä laajemminkin Kymijoen vaelluskalatuotannon potentiaalisia kehittämismahdollisuuksia. Keskeisiksi toimenpidevaihtoehdoiksi Kymijoen länsihaaran kalan kulun järjestämiseksi ja vesistön vaelluskalatuotannon kehittämiseksi muodostuivat kutukalojen ylisiirrot (VE1), Kalatiet (VE2) sekä kalatiet ja alasvaellusreitit (VE3). Näiden päävaihtoehtojen ohella esitettiin myös useita lisätoimenpiteita, joilla toimenpidenvaihtoehtojen elvytysvaikutusta voidaan vahvistaa. Vaellusyhteyksien avaamisen ohella Kymijoella tarvitaan todennäköisesti muitakin tukitoimenpiteitä, joihin voivat ylisiirtojen ohella lukeutua mm. kalastuksen säätely, mädin ja/tai poikasten tuki-istutukset sekä elinympäristökunnostukset.201

Surgery versus non-operative treatment for ER-stress unstable Weber-B unimalleolar fractures : A study protocol for a prospective randomized non-inferiority (Super-Fin) trial

Publisher Copyright: ©Roughly two-thirds of ankle fractures are unimalleolar injuries, the Weber B-type fibula fracture being by far the most common type. Depending on the trauma and the accompanying soft-tissue injury, these fractures are either stable or unstable. Current clinical practice guidelines recommend surgical treatment for unstable Weber B-type fibula fractures. An ongoing randomized, parallel group, non-inferiority trial comparing surgery and non-operative treatment for unstable Weber B-type ankle fractures with allocation ratio 1:1. The rationale for non-inferiority design is as follows: By being able to prove non-inferiority of non-operative treatment, we would be able to avoid complications related to surgery. However, the primary concern related to non-operative treatment is increased risks of ankle mortise incongruency, leading to secondary surgery, early post-traumatic osteoarthritis and poor function. After providing informed consent, 126 patients aged 16 years or older with an unimalleolar Weber B-type unstable fibula fracture were randomly assigned to surgery (open reduction and internal fixation) or non-operative treatment (6-week cast immobilization). We have completed the patient enrolment and are currently in the final stages of the 2-year follow-up. The primary, non-inferiority outcome is the Olerud-Molander Ankle Score (OMAS) at 2 years (primary time point). The predefined non-inferiority margin is set at 8 OMAS points. Secondary outcomes include the Foot and Ankle Score, a 100 mm Visual Analogue Scale for function and pain, the RAND-36-Item Health Survey for health-related quality-of-life, the range-of-motion of the injured ankle, malunion (ankle joint incongruity) and fracture union. Treatment-related complications and harms; symptomatic non-unions, loss of congruity of the ankle joint, reoperations and wound infections will also be recorded. We hypothesize that non-operative treatment yields non-inferior functional outcome to surgery, the current standard treatment, with no increased risk of harms.Peer reviewe

Genetic polymorphism of sterol transporters in children with future gallstones

Background & aims: Gallstone disease is related to hypersecretion of cholesterol in bile, and low serum phytosterol levels. We examined how genetic polymorphisms of sterol transporters affect childhood cholesterol metabolism trait predicting adult gallstone disease. Patients and methods: In retrospective controlled study, we determined D19H polymorphism of ABCG8 gene, genetic variation at Niemann-Pick C1-like 1 (NPC1L1) gene locus (rs41279633, rs17655652, rs2072183, rs217434 and rs2073548), and serum cholesterol, noncholesterol sterols and lipids in children affected by gallstones decades later (n = 66) and controls (n = 126). Results: In childhood, phytosterols were lower (9.7%-23.4%) in carriers of risk allele 19H compared to 19D homozygotes. Lowest campesterol/cholesterol tertile consisted of 1.9-times more future gallstone subjects, and 3.7-times more 19H carriers than highest one. Campesterol/cholesterol-ratio was highest in 19D homozygote controls, but similar to 11% lower in gallstone 19D homozygotes and similar to 25% lower among gallstone and control carriers of 19H. Gallstone subjects with alleles CC of rs41279633 and TT of rs217434 of NPC1L1 had similar to 18% lower campesterol/cholesterol-ratio compared to mutation carriers. Conclusions: Risk trait of cholesterol metabolism (low phytosterols) in childhood favouring cholesterol gallstone disease later in adulthood is influenced by risk variant 19H of ABCG8 and obviously also other factors. NPC1L1 variants have minor influence on noncholesterol sterols. (c) 2018 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Prediction model for an early revision for dislocation after primary total hip arthroplasty

Dislocation is one of the most common complications after primary total hip arthroplasty (THA). Several patient-related risk factors for dislocation have been reported in the previous literature, but only few prediction models for dislocation have been made. Our aim was to build a prediction model for an early (within the first 2 years) revision for dislocation after primary THA using two different statistical methods. The study data constituted of 37 pre- or perioperative variables and postoperative follow-up data of 16 454 primary THAs performed at our institution in 2008–2021. Model I was a traditional logistic regression model and Model II was based on the elastic net method that utilizes machine learning. The models’ overall performance was measured using the pseudo R2 values. The discrimination of the models was measured using C-index in Model I and Area Under the Curve (AUC) in Model II. Calibration curves were made for both models. At 2 years postoperatively, 95 hips (0.6% prevalence) had been revised for dislocation. The pseudo R2 values were 0.04 in Model I and 0.02 in Model II indicating low predictive capability in both models. The C-index in Model I was 0.67 and the AUC in Model II was 0.73 indicating modest discrimination. The prediction of an early revision for dislocation after primary THA is difficult even in a large cohort of patients with detailed data available because of the reasonably low prevalence and multifactorial nature of dislocation. Therefore, the risk of dislocation should be kept in mind in every primary THA, whether the patient has predisposing factors for dislocation or not. Further, when conducting a prediction model, sophisticated methods that utilize machine learning may not necessarily offer significant advantage over traditional statistical methods in clinical setup.publishedVersionPeer reviewe