Phytoplankton in Deep Lakes of the Dinaric Karst: Functional Biodiversity and Main Ecological Features.

Phytoplankton is a polyphyletic group of organisms that responds rapidly to environmental conditions and provides a reliable response to changes, making it a good ecological indicator for water quality monitoring. However, a gradient is almost essential for a reliable relationship between pressure and impact. In a low-gradient environment, ingenuity is required to outsmart the limitations of the commonly used linear relationship. Here, we examine changes in biomass and functional biodiversity by analysing larger data sets (2013-2022) in six ecologically diverse, natural, deep Croatian karst lakes with low nutrient gradients using nonlinear correlation coefficients and multivariate analyses in 209 samples. We found that phytoplankton biomass was most strongly influenced by nutrients, salinity and alkalinity, while light availability and total nitrogen strongly influenced phytoplankton functional biodiversity. An additional analysis of the TN:TP ratio revealed that the oligotrophic Lake Vransko is nitrogen-limited, and lakes Kozjak and Prosce are phosphorus-limited. This further clarified the relationship of phytoplankton to nutrients despite the low gradient. The complex analysis in this study provides a new perspective for predicting changes in the structure and succession of phytoplankton in deep karst lakes for successful management under apparent anthropogenic pressure and climate change.

Role of Trapped Molecules at Sliding Contacts in Lattice-Resolved Friction.

Understanding atomic friction within a liquid environment is crucial for engineering friction mechanisms and characterizing surfaces. It has been suggested that the lattice resolution of friction force microscope in liquid environments stems from a dry contact state, with all liquid molecules expelled from the area of closest approach between the tip and substrate. Here, we revisit this assertion by performing in-depth friction force microscopy experiments and molecular dynamics simulations of the influence of surrounding water molecules on the dynamic behavior of the nanotribological contact between an amorphous SiO2 probe and a monolayer MoS2 substrate. An analysis of simulation and experimental stick-slip patterns demonstrates the entrapment of water molecules at the contact interface. These trapped water molecules behave as an integral component of the probe and participate in its interaction with the substrate, affecting the dynamics of the probe and preventing long slips. Significantly, surrounding water from the capillary or layer exhibits a replenishing effect, acting as a water reservoir during sliding. This phenomenon facilitates the preservation of lattice-scale resolution across a range of applied normal loads.

Effects of Water Content on the Transport and Thermodynamic Properties of Phosphonium Ionic Liquids.

We present a numerical investigation of the influence of water content on the dynamic properties of a family of phosphonium-based room-temperature ionic liquids. The study presents a compelling correlation between structural changes in water-ionic liquid solutions and thermodynamic and transport properties across diverse systems. The results for phosphonium ionic liquids are compared with 1-butyl-3-methylimidazolium hexaphosphate ([bmim]PF6) as a reference. Through this approach, phosphonium cation structure-related characteristics can be identified and placed within the broader context of ionic liquids. These insights are underpinned by observed changes in interaction energy, boiling point, diffusion rate, and viscosity, highlighting the crucial role of water molecules in weakening the strength of interactions between ions within the ionic liquid. The investigation also explains temperature-dependent trends in phosphonium cations, showing that alkyl group length and molecular symmetry are important tuning parameters for the strength of Coulomb interactions. These results contribute to a refined understanding of phosphonium ionic liquid behavior in the presence of water, offering valuable insights for optimizing their use in diverse fields.

Delayed Antibody Response in the Acute Phase of Infection Is Associated with a Lower Mental Component of Quality of Life in Survivors of Severe and Critical COVID-19.

Background: The long-term sequelae of coronavirus disease 2019 (COVID-19) significantly affects quality of life (QoL) in disease survivors. Delayed development of the adaptive immune response is associated with more severe disease and a worse prognosis in COVID-19. The effects of delayed immune response on COVID-19 sequelae and QoL are unknown. Methods: We conducted a prospective study to assess the relationship between the delayed antibody response in the acute phase of infection in naïve unvaccinated patients suffering from severe or critical COVID-19 and their QoL 12 months after hospital discharge. The 12-item Short Form Survey (SF-12) questionnaire was used for assessment of QoL. The SF-12 evaluates both mental and physical components of QoL, incorporating a mental component score (MCS-12) and a physical component score (PCS-12). A delayed antibody response was defined as testing negative for anti-spike SARS-CoV-2 antibodies at the time of hospital admission. Results: The study included 274 patients (154 men and 120 women). Of the enrolled patients, 144 had a delayed immune response. These patients had a significantly lower MCS-12 (p = 0.002), but PCS-12 (p = 0.397) was not significantly different at the 12-month follow-up compared to patients with positive anti-spike SARS-CoV-2 antibodies. The MCS-12 at the time of follow-up was negatively associated with delayed antibody response irrespective of possible confounders (p = 0.006; B = 3.609; ηp2 = 0.035; 95% CI = 1.069-6.150). An MSC-12 below 50 points at the time of follow-up was positively associated with delayed antibody response (p = 0.001; B = 1.092; OR = 2.979; 95% CI = 1.554-5.711). Conclusions: This study confirmed that, in patients with severe and critical COVID-19, a negative result for anti-spike SARS-CoV-2 antibodies at the time of hospital admission is associated with a lower mental component of QoL in unvaccinated patients naïve to COVID-19 one year after hospital discharge.

European river typologies fail to capture diatom, fish, and macrophyte community composition.

Typology systems are frequently used in applied and fundamental ecology and are relevant for environmental monitoring and conservation. They aggregate ecosystems into discrete types based on biotic and abiotic variables, assuming that ecosystems of the same type are more alike than ecosystems of different types with regard to a specific property of interest. We evaluated whether this assumption is met by the Broad River Types (BRT), a recently proposed European river typology system, that classifies river segments based on abiotic variables, when it is used to group biological communities. We compiled data on the community composition of diatoms, fishes, and aquatic macrophytes throughout Europe and evaluated whether the composition is more similar in site groups with the same river type than in site groups of different river types using analysis of similarities, classification strength, typical species analysis, and the area under zeta diversity decline curves. We compared the performance of the BRT with those of four region-based typology systems, namely, Illies Freshwater Ecoregions, the Biogeographic Regions, the Freshwater Ecoregions of the World, and the Environmental Zones, as well as spatial autocorrelation (SA) classifications. All typology systems received low scores from most evaluation methods, relative to predefined thresholds and the SA classifications. The BRT often scored lowest of all typology systems. Within each typology system, community composition overlapped considerably between site groups defined by the types of the systems. The overlap tended to be the lowest for fishes and between Illies Freshwater Ecoregions. In conclusion, we found that existing broad-scale river typology systems fail to delineate site groups with distinct and compositionally homogeneous communities of diatoms, fishes, and macrophytes. A way to improve the fit between typology systems and biological communities might be to combine segment-based and region-based typology systems to simultaneously account for local environmental variation and historical distribution patterns, thus potentially improving the utility of broad-scale typology systems for freshwater biota.

Anti-SARS-CoV-2 Antibody Status at the Time of Hospital Admission and the Prognosis of Patients with COVID-19: A Prospective Observational Study.

The association between COVID-19 severity and antibody response has not been clearly determined. We aimed to assess the effects of antibody response to SARS-CoV-2 S protein at the time of hospital admission on in-hospital and longitudinal survival. Methods: A prospective observational study in naive hospitalised COVID-19 patients. The presence of anti-S SARS-CoV-2 IgM and IgG was evaluated using a lateral flow assay at the time of admission. The patients were followed up for 8-30 months to assess survival. We recruited 554 patients (330 men and 224 women). Overall, 63.0% of the patients had positive IgG or IgM anti-S SARS-CoV-2 antibodies at the time of hospital admission. In the univariate analysis, the patients with negative anti-S SARS-CoV-2 IgM and IgG antibodies were referred to the hospital sooner, had lower CRP and D-dimer concentrations, and were hospitalised longer. They were also more likely to be admitted to an intensive care unit and more often received baricitinib treatment. During their hospital stay, 8.5% of the antibody-positive and 22.3% of the antibody-negative patients died (p = 0.0001). The median duration of the follow-up was 21 months. During the follow-up after hospital discharge, 3.6% of antibody-positive and 9.1% of antibody-negative patients died (p = 0.027). In the multivariate analysis, the negative anti-S SARS-CoV-2 antibodies were associated with a higher risk of in-hospital death (OR 3.800; 95% CI 1.844-7.829; p = 0.0001) and with a higher risk of death during follow-up (OR 2.863; 95% CI 1.110-7.386; p = 0.030). These associations were independent of age, the time from symptom onset to hospital admission, CRP, D-Dimer, the number of comorbidities, disease severity at the time of hospital admission, and baricitinib therapy. Our study concludes that negative anti-S SARS-CoV-2 IgM and IgG at the time of admission are associated with higher in-hospital mortality and cause a higher risk of all-cause death during follow-up after discharge.

Nature of Dynamic Friction in a Humid Hydrophobic Nanocontact.

The physics of dynamic friction on water molecule contaminated surfaces is still poorly understood. In line with the growing interest in hydrophobic contact for industrial applications, this paper focuses on friction mechanisms in such interfaces. As a commonly used material, contact with graphite is considered in a twin-fold approach based on experimental investigations using the circular mode atomic force microscopy technique combined with molecular dynamic simulations. We demonstrate that an intuitive paradigm, which asserts that water molecules are squeezed out of a hydrophobic contact, should be refined. As a consequence, we introduce a mechanism considering a droplet produced within the sliding nanocontact by the accumulation of water adsorbed on the substrate. Then we show that a full slip regime of the droplet sliding on the hydrophobic substrate explains the experimental tribological behavior.

Adaptations of microbial communities and dissolved organics to seasonal pressures in a mesotrophic coastal Mediterranean lake.

In lake ecosystems, changes in eukaryotic and prokaryotic microbes and the concentration and availability of dissolved organic matter (DOM) produced within or supplied to the system by allochthonous sources are components that characterize complex processes in the microbial loop. We address seasonal changes of microbial communities and DOM in the largest Croatian lake, Vrana. This shallow lake is connected to the Adriatic Sea and is impacted by agricultural activity. Microbial community and DOM structure were driven by several environmental stressors, including drought, seawater intrusion and heavy precipitation events. Bacterial composition of different lifestyles (free-living and particle-associated) differed and only a part of the particle-associated bacteria correlated with microbial eukaryotes. Oscillations of cyanobacterial relative abundance along with chlorophyll a revealed a high primary production season characterized by increased levels of autochthonous DOM that promoted bacterial processes of organic matter degradation. From our results, we infer that in coastal freshwater lakes dependent on precipitation-evaporation balance, prolonged dry season coupled with heavy irrigation impact microbial communities at different trophic levels even if salinity increases only slightly and allochthonous DOM inputs decrease. These pressures, if applied more frequently or at higher concentrations, could have the potential to overturn the trophic state of the lake.

Biovolume and surface area calculations for microalgae, using realistic 3D models.

Morphology and spatial dimensions of microalgal units (cells or colonies) are among the most relevant traits of planktic algae, which have a pronounced impact on their basic functional properties, like access to nutrients or light, the velocity of sinking or tolerance to grazing. Although the shape of algae can be approximated by geometric forms and thus, their volume and surface area can be calculated, this approach cannot be validated and might have uncertainties especially in the case of complicated forms. In this study, we report on a novel approach that uses real-like 3D mesh objects to visualize microalgae and calculates their volume and surface area. Knowing these dimensions and their intraspecific variabilities, we calculated specific shape and surface area constants for more than 300 forms, covering more than two thousand taxa. Using these constants, the accurate volume and surface area can be quickly computed for each taxon and having these values, morphology-related metrics like surface area/volume ratio, the diameter of spherical equivalent can also be given quickly and accurately. Besides their practical importance, the volume and surface area constants can be considered as size-independent morphological traits that are characteristic for the microalgal shapes, and provide new possibilities of data analyses in the field of phytoplankton ecology.

The first cancer patient with COVID-19 in Slovakia.

BACKGROUND: In December 2019 a new strain of coronavirus SARS-CoV-2 has emerged and affected health care worldwide. Patients with cancer and other comorbidities are at increased risk for adverse outcomes in this infection. CASE: In this case report we present a 75-year-old patient with a localized gastric adenocarcinoma, currently treated by perioperative chemotherapy regimen, who had an rT-PCR proven novel coronavirus SARS-CoV-2 infection. Laboratory and radiologic assessments were performed in order to assess disease severity; however, the findings were not altered in accordance with the findings associated with COVID-19 disease. RESULTS: On the first hospital day the patient had a low grade fever with chills. Subsequently a pharmacological therapy with hydroxychloroquine and azithromycin was started. After pharmacologic and symptomatic treatment, the patient was reassessed for SARS-CoV-2, with negative results. At discharge, the patient was ordered a 14-day mandatory quarantine. After 57 days of follow-up, the patient underwent a new rapid antibody test by Acro Biotech inc., which gave negative results for IgM and IgG. CONCLUSION: An infection with SARS-CoV-2 is associated with a more severe disease in patients with comorbidities and cancer; however, this case patient had a mild course of COVID-19 disease. The aim of this case report is to share the information on the clinical course and outcomes of a patient with malignancy. Rapid spreading of information is crucial in the management of COVID-19.

Assembly of nanocube super-structures directed by surface and magnetic interactions.

We study the stabilisation of clusters and lattices of cuboidal particles with long-ranged magnetic dipolar and short-ranged surface interactions. Two realistic systems were considered: one with magnetisation oriented in the [001] crystallographic direction and the other with magnetisation along the [111] direction. We have studied magnetic nanocube clusters first in the limit of T = 0 K intending to elucidate the structural genesis of low energy configurations and then analysed finite-temperature behaviour of the same systems in simulations. Our results demonstrate that dipolar coupling can stabilise nanoparticle assemblies with cubic, planar, and linear arrangements seen previously in experiments. While attractive surface energy supports the formation of super-cubes, repulsion results in the elongated structures in the form of rods and chains. We observe the stabilisation of the ferromagnetic planar arrangements of the cubes standing on their corners and in contact over edges. We illustrate that minimal energy structures depend only on the size of the assembly and balance of surface repulsion and magnetic dipolar coupling. The presented results are scalable to different particle sizes and material parameters.

Mycotic aneurysm as a hidden cause of treatment failure of pyelonephritis caused by Salmonella enterica, serovar Enteritidis.

Invasive non-typhoidal Salmonella (NTS) infections are rare in developed countries but their incidence is increasing. One of the most severe complications of extraintestinal NTS infection is mycotic aneurysm. Its natural course is usually fatal and its treatment demands complex interdisciplinary management. We present a case of severe NTS sepsis complicated by mycotic aneurysm of the abdominal aorta and left internal iliac artery and obstructive pyelonephritis. Obstruction of the left ureter was caused by pressure from the left internal iliac artery aneurysm and surrounding edema. The patient presented with clinical symptoms of sepsis and pyelonephritis. Despite abdominal ultrasound and native computed tomography, the mycotic aneurysm eluded initial examination. It remained undiagnosed until the patient presented with recurrent symptoms after stopping 17 days of antimicrobial treatment and was finally revealed by magnetic resonance imaging and contrast computed tomography. The patient was successfully treated by ligation of the left internal iliac artery, partial extirpation of the aneurysm and prolonged parenteral antimicrobial treatment. This case raises concerns that mycotic aneurysm might be present in cases of obstructive pyelonephritis caused by NTS and its early recognition is vital for appropriate management.

Spontaneous in-flight assembly of magnetic nanoparticles into macroscopic chains.

Knowing the interactions controlling aggregation processes in magnetic nanoparticles is of strong interest in preventing or promoting nanoparticles' aggregation at wish for different applications. Dipolar magnetic interactions, proportional to the particle volume, are identified as the key driving force behind the formation of macroscopic aggregates for particle sizes above about 20 nm. However, aggregates' shape and size are also strongly influenced by topological ordering. 1-D macroscopic chains of several micrometer lengths are obtained with cube-shaped magnetic nanoparticles prepared by the gas-aggregation technique. Using an analytical model and molecular dynamics simulations, the energy landscape of interacting cube-shaped magnetic nanoparticles is analysed revealing unintuitive dependence of the force acting on particles with the displacement and explaining pathways leading to their assembly into long linear chains. The mechanical behaviour and magnetic structure of the chains are studied by a combination of atomic and magnetic force measurements, and computer simulation. The results demonstrate that [111] magnetic anisotropy of the cube-shaped nanoparticles strongly influences chain assembly features.

Molecular dynamics investigation of the influence of the shape of the cation on the structure and lubrication properties of ionic liquids.

We present a theoretical study of the influence of the molecular geometry of the cation on the response of ionic liquids (ILs) to confinement and mechanical strain. The so-called tailed model includes a large spherical anion and asymmetric cation consisting of a charged head and a neutral tail. Despite its simplicity, this model recovers a wide range of structures seen in ILs: a simple cubic lattice for small tails, a liquid-like state for symmetric cation-tail dimers, and a molecular layer structure for dimers with large tails. A common feature of all investigated model ILs is the formation of a fixed (stable) layer of cations along solid plates. We observe a single anionic layer for small gap widths, a double anionic layer for intermediate ones, and tail-to-tail layer formation for wide gaps. The normal force evolution with gap size can be related to the layer formed inside the gap. The low hysteretic losses during the linear cyclic motion suggest the presence of strong slip inside the gap. In our model the specific friction is low and the friction force decreases with tail size.

Correction: A platform for nanomagnetism - assembled ferromagnetic and antiferromagnetic dipolar tubes.

Correction for 'A platform for nanomagnetism - assembled ferromagnetic and antiferromagnetic dipolar tubes' by Igor Stankovic et al., Nanoscale, 2019, DOI: 10.1039/c8nr06936k.

A platform for nanomagnetism - assembled ferromagnetic and antiferromagnetic dipolar tubes.

We report an interesting case where magnetic phenomena can transcend mesoscopic scales. Our system consists of tubes created by the assembly of dipolar spheres. The cylindrical topology results in the breakup of degeneracy observed in planar square and triangular packings. As far as the ground state is concerned, the tubes switch from circular to axial magnetization with increasing tube length. All magnetostatic properties found in magnetic nanotubes, in which the dipolar interaction is comparable to or dominant over the exchange interaction, are reproduced by the dipolar tubes including an intermediary helically magnetized state. Besides, we discuss the antiferromagnetic phase resulting from the square arrangement of the dipolar spheres and its interesting vortex state.

Influence of confinement on flow and lubrication properties of a salt model ionic liquid investigated with molecular dynamics.

We present a molecular dynamics study of the effects of confinement on the lubrication and flow properties of ionic liquids. We use a coarse-grained salt model description of ionic liquid as a lubricant confined between finite solid plates and subjected to two dynamic regimes: shear and cyclic loading. The impact of confinement on the ion arrangement and mechanical response of the system has been studied in detail and compared to static and bulk properties. The results have revealed that the wall slip has a profound influence on the force built-up as a response to mechanical deformation and that at the same time in the dynamic regime interaction with the walls represents a principal driving force governing the behaviour of ionic liquid in the gap. We also observe a transition from a dense liquid to an ordered and potentially solidified state of the ionic liquid taking place under variable normal loads and under shear.

Molecules on rails: friction anisotropy and preferential sliding directions of organic nanocrystallites on two-dimensional materials.

Two-dimensional (2D) materials are envisaged as ultra-thin solid lubricants for nanomechanical systems. So far, their frictional properties at the nanoscale have been studied by standard friction force microscopy. However, lateral manipulation of nanoparticles is a more suitable method to study the dependence of friction on the crystallography of two contacting surfaces. Still, such experiments are lacking. In this study, we combine atomic force microscopy (AFM) based lateral manipulation and molecular dynamics simulations in order to investigate the movements of organic needle-like nanocrystallites grown by van der Waals epitaxy on graphene and hexagonal boron nitride. We observe that nanoneedle fragments - when pushed by an AFM tip - do not move along the original pushing directions. Instead, they slide on the 2D materials preferentially along the needles' growth directions, which act as invisible rails along commensurate directions. Further, when the nanocrystallites were rotated by applying a torque with the AFM tip across the preferential sliding directions, we find an increase of the torsional signal of the AFM cantilever. We demonstrate in conjunction with simulations that both, the significant friction anisotropy and preferential sliding directions are determined by the complex epitaxial relation and arise from the commensurate and incommensurate states between the organic nanocrystallites and the 2D materials.

Structure and cohesive energy of dipolar helices.

This paper deals with the investigation of cohesive energy in dipolar helices made up of hard spheres. Such tubular helical structures are ubiquitous objects in biological systems. We observe a complex dependence of cohesive energy on surface packing fraction and dipole moment distribution. As far as single helices are concerned, the lowest cohesive energy is achieved at the highest surface packing fraction. Besides, a striking non-monotonic behavior is reported for the cohesive energy as a function of the surface packing fraction. For multiple helices, we discover a new phase, exhibiting markedly higher cohesive energy. This phase is referred to as ZZ tube consisting of stacked crown rings (reminiscent of a pile of zig-zag rings), resulting in a local triangular arrangement with densely packed filaments parallel to the tube axis.

Reply to "Comment on 'Self-assembly of magnetic balls: From chains to tubes' ".

The authors of the Comment [Phys. Rev. E 91, 057201 (2015)] propose compact round clusters as, energetically, better candidates than stacked rings found in Messina et al. [Phys. Rev. E 89, 011202 (2014)] (forming open tubes) at a pretty large number of constitutive magnets, typically for N≳1300. Our new findings show that elongated rodlike structures can even outmatch the reported structures in Friedrich et al. [Phys. Rev. E 91, 057201 (2015)] and in Messina et al. [Phys. Rev. E 89, 011202 (2014)] from typically N≳460.