Characterisation of Moisture in Scots Pine (Pinus sylvestris L.) Sapwood Modified with Maleic Anhydride and Sodium Hypophosphite

In this study, the wood–water interactions in Scots pine sapwood modified with maleic anhydride (MA) and sodium hypophosphite (SHP) was studied in the water-saturated state. The water in wood was studied with low field nuclear magnetic resonance (LFNMR) and the hydrophilicity of cell walls was studied by infrared spectroscopy after deuteration using liquid D2O. The results of LFNMR showed that the spin–spin relaxation (T2) time of cell wall water decreased by modification, while T2 of capillary water increased. Furthermore, the moisture content and the amount of water in cell walls of modified wood were lower than for unmodified samples at the water-saturated state. Although the amount of accessible hydroxyl groups in modified wood did not show any significant difference compared with unmodified wood, the increase in T2 of capillary water indicates a decreased affinity of the wood cell wall to water. However, for the cell wall water, the physical confinement within the cell walls seemed to overrule the weaker wood–water interactions.

On the Issue of Standardizing Concrete Frost Resistance to Ensure the Reinforced Concrete Structures Durability

When erecting monolithic reinforced concrete structures, the structure of concrete can differ significantly from the laboratory standard due to the complexity of providing favorable conditions for hardening, and therefore the compressive strength and especially the frost resistance of concrete may not meet the design requirements, which can negatively affect the reinforced concrete structure durability and require amplification, especially in earthquake-prone areas [1, 2]. Increasing the durability of reinforced concrete structures is possible by creating a rational stress field, for example, by prestressing, incl. variable along the length of the structure [3,4], but this technique is difficult to implement for monolithic reinforced concrete structures. It is possible to use effective materials or methods of manufacturing structures [5, 6]. But this is also mainly problematic for use in the construction of monolithic reinforced concrete structures. Generally accepted methods of calculating the reinforced concrete structures durability subjected to cyclic freezing-thawing during operation, incl. in a water-saturated state, do not exist. At the design stage, ensuring the durability of such reinforced concrete structures is mainly reduced to the reasonable assignment of requirements for concrete quality indicators, depending on the operating conditions, which is the focus of BC 28.13330.2017 (EN 206) and GOST 31384-2017 from the premise of ensuring durability of at least 50 years. In the above-mentioned norms of the Russian Federation, in fact, two approaches are presented to ensure the durability of reinforced concrete structures during cyclic freezing-thawing, incl. in a water-saturated state, namely: designing a concrete structure capable of working under such conditions by standardizing the values of cement consumption, W/C ratio, class of concrete in terms of compressive strength, amount of entrained air, or rationing of concrete grades in terms of frost resistance F1 (first base method GOST 10060-2012 provides for freezing in air, saturation and thawing in water) or F2 (second base method GOST 10060-2012 provides for freezing in air, saturation and thawing in 5% sodium chloride solution). The purpose of this work is to compare various approaches to ensuring the durability of reinforced concrete structures operated during cyclic freezing-thawing and to analyze the provision of durability with standardized indicators when designing the structure of concrete.

Effect of SGLT-1/2 inhibition on mitochondrial dysfunction in left atrial remodeling during HFpEF

Background In the DAPA-HF trial, SGLT inhibition reduces cardiovascular mortality in heart failure. However, the mechanism and a potential positive effect in HfpEF remain elusive. Introduction LA remodeling is a hallmark feature of HFpEF and commonly associated with LA enlargement and dysfunction. Previous studies of SGLT-2 inhibitor Empagliflozin suggest a utilization of alternative metabolites for energy consumption (i.e. ketone bodies). Additionally, alterations of sodium and calcium ion hemostasis have been reported. We investigated the effect of SGLT inhibition on mitochondrial (dys)function during atrial remodeling in HFpEF. Methods Rats (WT: Wistar Kyoto, HFpEF: ZFS-1 Obese (metabolic syndrome)) were obtained at ∼10w and fed Purina 5008 diet. At 17w, animals were randomized to treatment with either vehicle or Sota (30mg/kg/d) for 5w until primary adult cardiomyocytes were isolated for final experiments. Structural information of mitochondria was obtained with Mitotracker Red in either a glucose starved (1h incubation with mannitol) or saturated state. ROS production was assessed with H2-DCF in a starved and saturated condition. Mitochondrial calcium buffer capacity was imaged with Rhod-2 following perforation of the cellular membrane with saponin. Glycolytic dependency of calcium cycling was assessed upon glycolytic inhibition with 2-deoxyglucose during imaging of cytosolic calcium transients with Fura-2. Results In a glucose saturated state, LA cardiomyocytes in HFpEF showed increased mitochondrial density, which was ameliorated with Sota. Sota increased mitochondrial calcium buffer capacity in HFpEF, indicating a decrease in mitochondrial resting calcium. Differences in mitochondrial fission could not be detected. However, during glucose starvation cardiomyocytes showed a decrease in mitochondrial fission and ROS production with Sota. A difference in ROS production was not visible when cells were abruptly challenged with high glucose concentrations, but Sota decreased mitochondrial fission, indicating long term protective properties towards ROS. Glycolytic inhibition led to an increase of cytosolic diastolic calcium and calcium transient peak height in HFpEF vs. WT, indicating an increased glucose dependency of cytosolic calcium cycling, which was mitigated with Sota. Additionally, Sota negated an increase in diastolic calcium, when cardiomyocytes where challenged with high concentrations of glucose after starvation. Conclusion SGLT1/2 inhibition alters mitochondrial calcium uptake in HFpEF and positively affects mitochondrial structure with subsequent decreases of ROS production and enhanced calcium homeostasis. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Else-Kröner-Fresenius-Stiftung, Deutsches Zentrum für Herz-Kreislaufforschung

Shear damage stress and frequency spectral characteristics of dry and saturated red sandstone determined by acoustic emission

Dry and saturated red sandstone direct shear tests under different normal stresses were carried out in the rock shear test system to clarify the shear strength and damage characteristics. The cumulative ring count, cumulative energy, dominant frequency, secondary dominant frequency, and the effects of water saturation and normal stress on them were analyzed in detail. Results show that the cumulative ring count and cumulative energy curves of acoustic emission (AE) can be divided into linear increasing and step jump stages. The cumulative curves in the dry state have significant steps, thereby indicating that the repetitive process of “crack rapid development — energy accumulation” is significant. The cumulative ring count and cumulative energy are great when the normal stress is high. Under the same normal stress, the cumulative ring count and cumulative energy in the dry state are greater than those in the saturated state. The shear damage stresses were determined according to the cumulative curves. The failure process of red sandstone is divided into crack initiation and crack rapid development zones. The variation law of shear damage stress and shear strength of red sandstone is basically consistent. The growth rate of shear damage stress and strength of dry red sandstone is greater than that of saturated red sandstone with the increase in normal stress. The dominant and secondary dominant frequencies of dry and saturated red sandstone decrease with the increase in normal stress. The dominant frequency is less than the secondary frequency. Under the same normal stress, the dominant and secondary dominant frequencies of red sandstone shear failure in the dry state are less than those in the saturated state, thereby indicating that the shear microcrack scale of red sandstone in the saturated state is smaller than that in the dry state. The results have a certain theoretical significance to determine the shear damage degree of red sandstone by AE monitoring.

Zonally dominated dynamics and Dimits threshold in curvature-driven ITG turbulence

The saturated state of turbulence driven by the ion-temperature-gradient instability is investigated using a two-dimensional long-wavelength fluid model that describes the perturbed electrostatic potential and perturbed ion temperature in a magnetic field with constant curvature (a $Z$ -pinch) and an equilibrium temperature gradient. Numerical simulations reveal a well-defined transition between a finite-amplitude saturated state dominated by strong zonal-flow and zonal temperature perturbations, and a blow-up state that fails to saturate on a box-independent scale. We argue that this transition is equivalent to the Dimits transition from a low-transport to a high-transport state seen in gyrokinetic numerical simulations (Dimits et al., Phys. Plasmas, vol. 7, 2000, 969). A quasi-static staircase-like structure of the temperature gradient intertwined with zonal flows, which have patch-wise constant shear, emerges near the Dimits threshold. The turbulent heat flux in the low-collisionality near-marginal state is dominated by turbulent bursts, triggered by coherent long-lived structures closely resembling those found in gyrokinetic simulations with imposed equilibrium flow shear (van Wyk et al., J. Plasma Phys., vol. 82, 2016, 905820609). The breakup of the low-transport Dimits regime is linked to a competition between the two different sources of poloidal momentum in the system – the Reynolds stress and the advection of the diamagnetic flow by the $\boldsymbol {E}\times \boldsymbol {B}$ flow. By analysing the linear ion-temperature-gradient modes, we obtain a semi-analytic model for the Dimits threshold at large collisionality.

Fluctuation dynamo in a weakly collisional plasma

The turbulent amplification of cosmic magnetic fields depends upon the material properties of the host plasma. In many hot, dilute astrophysical systems, such as the intracluster medium (ICM) of galaxy clusters, the rarity of particle–particle collisions allows departures from local thermodynamic equilibrium. These departures – pressure anisotropies – exert anisotropic viscous stresses on the plasma motions that inhibit their ability to stretch magnetic-field lines. We present an extensive numerical study of the fluctuation dynamo in a weakly collisional plasma using magnetohydrodynamic (MHD) equations endowed with a field-parallel viscous (Braginskii) stress. When the stress is limited to values consistent with a pressure anisotropy regulated by firehose and mirror instabilities, the Braginskii-MHD dynamo largely resembles its MHD counterpart, particularly when the magnetic field is dynamically weak. If instead the parallel viscous stress is left unabated – a situation relevant to recent kinetic simulations of the fluctuation dynamo and, we argue, to the early stages of the dynamo in a magnetized ICM – the dynamo changes its character, amplifying the magnetic field while exhibiting many characteristics reminiscent of the saturated state of the large-Prandtl-number ( ${Pm}\gtrsim {1}$ ) MHD dynamo. We construct an analytic model for the Braginskii-MHD dynamo in this regime, which successfully matches simulated dynamo growth rates and magnetic-energy spectra. A prediction of this model, confirmed by our numerical simulations, is that a Braginskii-MHD plasma without pressure-anisotropy limiters will not support a dynamo if the ratio of perpendicular and parallel viscosities is too small. This ratio reflects the relative allowed rates of field-line stretching and mixing, the latter of which promotes resistive dissipation of the magnetic field. In all cases that do exhibit a viable dynamo, the generated magnetic field is organized into folds that persist into the saturated state and bias the chaotic flow to acquire a scale-dependent spectral anisotropy.

A Mathematical Model for the Electrical Resistivity of Cement Paste at Early Ages Considering the Partially Saturated State

For cementitious materials, electrical resistivity is often used in the study of the cement hydration process at early age, as one of the few indicators that can be continuously and non-destructively monitored. Variation characteristics of resistivity are widely reported to interact with the early-age performance of cement paste, such as hydration kinetics parameters and setting time. However, there is no reasonable mathematical model to predict the resistivity at early ages, especially within the first 24 h, due to significant changes in the porosity and degree of saturation. In this work, a mathematical model was developed by considering the partially saturated state and density change of C-S-H (calcium silicate hydrate). To verify the model, two experimental methods were chosen, including the non-contact electrical resistivity test and isothermal calorimetry test. The hydration heat and resistivity of cement paste with a water–cement ratio of 0.35 and 0.45 were continuously monitored for 3 days. In the resistivity test, embedded temperature sensors were used to monitor the internal temperature and temperature correction was treated carefully in order to obtain accurate data. The test results prove that the mathematical model can accurately predict electrical resistivity and describe the saturation state of early-age cement pastes under sealed curing.

Corrosion Behaviors of Reinforcing Steel in Concrete with Various Moisture Contents

Moisture contents of concrete can affect the corrosion of reinforcing steel. In this paper, moisture contents of concrete were increased by filling the small holes with water or fully submerging in water. The effect of moisture contents on the corrosion behaviors of cathodic and anodic steel was investigated by comparing the half-cell potential, micro-cell and macro-cell current density. The results indicated that when only the concrete around cathodic steel was in water-saturated state, it could greatly weakened the kinetics of cathodic reaction and resulted in a considerable decrease in macro-cell current. When only the concrete around anodic steel was in water-saturated state, it could not effectively inhibit the macro-cell corrosion. When both the concrete around the cathodic steel and the anodic steel were in water-saturated state, the macro-cell current flowing between cathode and anode could be inhibited effectively, and the corrosion was little affected by chloride contents.