Determination of the Kinetics and Thermodynamic Parameters of Lignocellulosic Biomass Subjected to the Torrefaction Process

The torrefaction process upgrades biomass characteristics and produces solid biofuels that are coal-like in their properties. Kinetics analysis is important for the determination of the appropriate torrefaction condition to obtain the best utilization possible. In this study, the kinetics (Friedman (FR) and Kissinger–Akahira–Sunose (KAS) isoconversional methods) of two final products of lignocellulosic feedstocks, miscanthus (Miscanthus x giganteus) and hops waste (Humulus Lupulus), were studied under different heating rates (10, 15, and 20 °C/min) using thermogravimetry (TGA) under air atmosphere as the main method to investigate. The results of proximate and ultimate analysis showed an increase in HHV values, carbon content, and fixed carbon content, followed by a decrease in the VM and O/C ratios for both torrefied biomasses, respectively. FTIR spectra confirmed the chemical changes during the torrefaction process, and they corresponded to the TGA results. The average E_α for torrefied miscanthus increased with the conversion degree for both models (25–254 kJ/mol for FR and 47–239 kJ/mol for the KAS model). The same trend was noticed for the torrefied hops waste samples; the values were within the range of 14–224 kJ/mol and 60–221 kJ/mol for the FR and KAS models, respectively. Overall, the E_a values for the torrefied biomass were much higher than for raw biomass, which was due to the different compositions of the torrefied material. Therefore, it can be concluded that both torrefied products can be used as a potential biofuel source.     

Endocytic proteins with prion-like domains form viscoelastic condensates that enable membrane remodeling

Membrane invagination and vesicle formation are key steps in endocytosis and cellular trafficking. Here, we show that endocytic coat proteins with prion-like domains (PLDs) form hemispherical puncta in the budding yeast, Saccharomyces cerevisiae. These puncta have the hallmarks of biomolecular condensates and organize proteins at the membrane for actin-dependent endocytosis. They also enable membrane remodeling to drive actin-independent endocytosis. The puncta, which we refer to as endocytic condensates, form and dissolve reversibly in response to changes in temperature and solution conditions. We find that endocytic condensates are organized around dynamic protein–protein interaction networks, which involve interactions among PLDs with high glutamine contents. The endocytic coat protein Sla1 is at the hub of the protein–protein interaction network. Using active rheology, we inferred the material properties of endocytic condensates. These experiments show that endocytic condensates are akin to viscoelastic materials. We use these characterizations to estimate the interfacial tension between endocytic condensates and their surroundings. We then adapt the physics of contact mechanics, specifically modifications of Hertz theory, to develop a quantitative framework for describing how interfacial tensions among condensates, the membrane, and the cytosol can deform the plasma membrane to enable actin-independent endocytosis.

Endocytosis in eukaryotic cells can occur via two separate mechanisms: actin-dependent and actin-independent pathways. In this study, we used the budding yeast Saccharomyces cerevisiae as a tractable model system to uncover the mechanistic basis for actin-independent endocytosis. This is directly relevant to the early stages of endocytic membrane invagination that occurs in mammalian cells through homologs of the proteins that we identify and study here in yeast (1, 2). In S. cerevisiae, membrane invagination that enables endocytosis is normally driven by growth of membrane-bound branched actin (3). A second actin-independent route to endocytosis is realized when intracellular turgor pressure is reduced. This reduction of turgor pressure alleviates the tension on plasma membranes that would normally oppose membrane invagination (1, 4). Although this actin-independent mechanism is not evident under laboratory conditions, it does occur at the hyperosmotic, high-sucrose concentrations that can be found in the wild when yeast grow on rotting fruit and under industrial fermentation conditions, particularly in the context of bioethanol production (1).In both mechanisms, endocytosis is initiated by the coordinated recruitment of a number of proteins associated with distinct stages of endocytic maturation (5). Clathrin heavy and light chains first interact with initiator proteins (Ede1 and Syp1) to form a lattice on the membrane. Subsequently, early coat proteins such as Sla1, Sla2, Ent1, Ent2, and Yap1801 (6) bind directly to the adaptor–clathrin lattice and form the cortical body (5). Electron microscopy data highlight the existence of hemispherical membraneless bodies around endocytic sites. These bodies are identifiable by following the localization of labeled endocytic coat proteins such as Sla1. The observed Sla1-labeled bodies are known to exclude ribosomes from regions that are near the cortical sites in the cytosol. Importantly, these endocytic bodies form even when actin is not polymerized, and the membrane is flat (7).Many of the coat proteins in bodies that form around endocytic sites include prion-like domains (PLDs). These are low-complexity intrinsically disordered domains that are enriched in polar amino acids such as glutamine, asparagine, glycine, and serine and are interspersed by aromatic residues (6, 8). Proteins with PLDs have the ability to drive the formation of membraneless biomolecular condensates through phase separation in cells (9) and in vitro (10). Condensates are mesoscale, nonstoichiometric macromolecular assemblies that concentrate biomolecules (11–13). Here, we show that endocytosis in S. cerevisiae involves the concentration of PLD-containing proteins, including the essential protein Sla1, within biomolecular condensates that form at cortical sites (14). Inferences from indirect measurements suggest that these condensates have viscoelastic properties and that they are scaffolded by a dense network of PLD-containing proteins. We show that condensate formation requires an intact PLD and the coat protein Sla1 is at the hub of the condensate-driving protein–protein interaction network. The distinctive compositional biases within PLDs of coat proteins contribute to condensate formation and function. We present a model, motivated by Hertz contact theory (15–17), to provide a plausible explanation for how interfacial tensions among condensates, the membrane, and the cytosol can enable membrane invagination and drive actin-independent endocytosis. This model shows that the formation of condensates and cohesiveness of molecular interactions within them are likely to be essential for mechanoactive processes associated with actin-independent endocytosis.     

Thermodynamic Formation Properties of Point Defects in Germanium Crystal

Point defects are crucial in determining the quality of germanium crystals. A quantitative understanding of the thermodynamic formation properties of the point defects is necessary for the subsequent control of the defect formation during crystal growth. Here, molecular dynamics simulations were employed to investigate the formation energies, total formation free energies and formation entropies of the point defects in a germanium crystal. As far as we know, this is the first time that the total formation free energies of point defects in a germanium crystal have been reported in the literature. We found that the formation energies increased slightly with temperature. The formation free energies decreased significantly with an increase in temperature due to the increase in entropy. The estimated total formation free energies at the melting temperature are ~1.3 eV for self-interstitial and ~0.75 eV for vacancy, corresponding to a formation entropy of ~15 k_B for both types of point defects.     

Phase-transforming metamaterial with magnetic interactions

Solid–solid phase transformations can affect energy transduction and change material properties (e.g., superelasticity in shape memory alloys and soft elasticity in liquid crystal elastomers). Traditionally, phase-transforming materials are based on atomic- or molecular-level thermodynamic and kinetic mechanisms. Here, we develop elasto-magnetic metamaterials that display phase transformation behaviors due to nonlinear interactions between internal elastic structures and embedded, macroscale magnetic domains. These phase transitions, similar to those in shape memory alloys and liquid crystal elastomers, have beneficial changes in strain state and mechanical properties that can drive actuations and manage overall energy transduction. The constitutive response of the elasto-magnetic metamaterial changes as the phase transitions occur, resulting in a nonmonotonic stress–strain relation that can be harnessed to enhance or mitigate energy storage and release under high–strain-rate events, such as impulsive recoil and impact. Using a Landau free energy–based predictive model, we develop a quantitative phase map that relates the geometry and magnetic interactions to the phase transformation. Our work demonstrates how controllable phase transitions in metamaterials offer performance capabilities in energy management and programmable material properties for high-rate applications.

Soli d–solid phase transitions can enhance energy transduction to drive actuation. For example, in shape memory alloys, phase transitions from martensite to austenite lead to changes in the lattice displacement, which have been harnessed to cause movement (1, 2). Similarly, phase transitions in liquid crystal elastomers, from well-aligned nematic states to randomly aligned isotropic states, have been used to drive motion (3–8). Such phase transitions can also change the mechanical properties of the material system. For example, liquid crystal elastomers can enter in a state of “semisoft elasticity,” where strain is accommodated at near-constant stress as the material transitions from one phase to another (4, 9). Transformations such as these offer desirable control of energy conversion (10, 11), which can be beneficial in dissipating energy and protecting the system from damage. While solid–solid phase transitions provide promise for energy-management devices, predictably engineering these transitions and their impact on material properties is challenging.Mechanical metamaterials offer an opportunity to overcome this challenge (12, 13). Mechanical metamaterials use periodically arranged blocks, or “meta-atoms” (13), to mediate mechanical deformation, stress, and energy. They have been used to program stress–strain responses (14–16), modulate elastic wave propagation (17–21), and control energy dissipation (22, 23). Mechanical metamaterials typically rely upon internal geometric changes to introduce functionality, taking advantage of known nonlinear geometric mechanics for elastic materials (24, 25). This approach is widely adopted since analytical or numerical models can be readily derived to understand and predict the observed behaviors, thus providing pathways for systematic programming of the material''s response.Further advantages may be realized by combining additional fields beyond elasticity (26). Recently, the addition of field-responsive materials to metamaterials has been demonstrated to offer advantageous functionality (27–31). These demonstrations are impactful on their own, but more importantly, they introduce a broader paradigm with far-reaching implications. In particular, the combination of nonlinear fields, such as magnetic and electric, with orientationally dependent regimes of attraction and repulsion opens up the creation of “meta-atoms” that more closely reflect characteristics of atomic or molecular arrangements in materials phase structures (31). Accordingly, this counter play of nonlinear fields can be used to quantitatively define phase transitions in mechanical metamaterials composed of elastic and magnetic elements.Here, we demonstrate the power of this paradigm by developing elasto-magnetic metamaterials that undergo phase transitions. These phase transitions, similar to enabling ones in shape memory alloys and liquid crystal elastomers, have beneficial changes in strain state and mechanical properties that can drive actuations and manage overall energy transduction. The metamaterial changes its constitutive response concurrently as the phase transitions happen, resulting in a nonmonotonic stress–strain relation. The reversible shift between the two phases significantly enhances the metamaterials'' dynamic performance, improving the energy release in dynamic recoil and mitigating the impact loading. Importantly, we introduce a Landau free energy framework to model the phase transitions for the elasto-magnetic metamaterials, which can be extended to metamaterials with other field-responsive materials or ones that are purely mechanical (20, 21). This framework creates opportunities based on fundamental principles for using phase transitions to control engineering performance at high rates.     

Structural and energetic analysis of metastable intermediate states in the E1P–E2P transition of Ca2+-ATPase

Sarcoplasmic reticulum (SR) Ca²⁺-ATPase transports two Ca²⁺ ions from the cytoplasm to the SR lumen against a large concentration gradient. X-ray crystallography has revealed the atomic structures of the protein before and after the dissociation of Ca²⁺, while biochemical studies have suggested the existence of intermediate states in the transition between E1P⋅ADP⋅2Ca²⁺ and E2P. Here, we explore the pathway and free energy profile of the transition using atomistic molecular dynamics simulations with the mean-force string method and umbrella sampling. The simulations suggest that a series of structural changes accompany the ordered dissociation of ADP, the A-domain rotation, and the rearrangement of the transmembrane (TM) helices. The luminal gate then opens to release Ca²⁺ ions toward the SR lumen. Intermediate structures on the pathway are stabilized by transient sidechain interactions between the A- and P-domains. Lipid molecules between TM helices play a key role in the stabilization. Free energy profiles of the transition assuming different protonation states suggest rapid exchanges between Ca²⁺ ions and protons when the Ca²⁺ ions are released toward the SR lumen.

Sarcoplasmic reticulum Ca²⁺-ATPase (SR Ca²⁺-ATPase or SERCA1a) is a representative P-type ATPase that transports Ca²⁺ ions against a 10⁴ times concentration gradient across the SR membrane. The transport mechanism was originally described by E1/E2 theory, whereby the protein alternates between Ca²⁺ high-affinity E1 and low-affinity E2 states. A more-detailed reaction cycle requires multiple steps, including the binding/dissociation of Ca²⁺, H⁺-counter transport, ATP-binding and hydrolysis, phosphorylation/dephosphorylation of Asp351, and the dissociation of ADP and Pi (1–3) (SI Appendix, Fig. S1). Structurally, the Ca²⁺-ATPase consists of three cytoplasmic domains (actuator; A, nucleotide-binding; N, and phosphorylation; P) and 10 transmembrane (TM) helices (M1-M10) (4, 5). Two Ca²⁺-binding sites are located in M4-M6 and M8 (6), while a nucleotide, ATP or ADP, is bound at the N–P domain interface (7). Functional interconnections between the cytoplasmic domains and TM helices are necessary in the reaction cycle (8, 9).Molecular mechanisms underlying Ca²⁺ uptake by the ATPase have been investigated in biochemical experiments as well as structural studies. In particular, crystal structures of the Ca²⁺-ATPase, which represent different physiological states in the cycle (SI Appendix, Fig. S1), have provided essential information for understanding structure–function relationships (8, 9). Each crystal structure well explains the results of mutagenesis (3, 10), limited proteolysis studies (11, 12), and other biochemical experiments. Comparisons between multiple crystal structures provide direct evidence on how conformational changes of the Ca²⁺-ATPase take place from one step to another in the cycle. For instance, crystal structures that represent E1P⋅ADP⋅2Ca²⁺ and E2P (Fig. 1 A and B) reveal important conformational changes to release Ca²⁺ toward the SR lumen: 1) the A-domain rotates ∼90°; 2) the threonine–glycine–glutamate–serine (TGES) loop in the A-domain reaches the phosphorylated Asp351 in the P-domain (13–15); 3) M1-M6 are rearranged to open the luminal gate for the dissociation of Ca²⁺. Despite the increasing structural information, there are still unresolved questions. A series of biochemical studies suggested the existence of two intermediate states, E1P⋅2Ca²⁺ and E2P⋅2Ca²⁺. However, atomistic structures and their energetics in these intermediate states would be required to understand their functional roles.Open in a separate windowFig. 1.Structures of SR Ca²⁺-ATPase embedded in a DOPC membrane in E1P⋅ADP⋅2Ca²⁺ (PDB ID: 2ZBD) (A) and E2P (PDB ID: 2ZBE) (B). The three cytoplasmic domains (A, N, and P) are colored in red, purple, and green, respectively. (C) A structural transition pathway predicted using the mean-force string method is projected onto a two-dimensional map along with the two distance RMSDs (dRMS) from the representative structures in MD simulations of E1P and E2P_dp. In the simulation, Glu908 at the Ca²⁺-binding sites is protonated to mimic the same protonation states of E1P. Only the atomic coordinates that are involved in the collective variables (CVs) are used for dRMS calculations. The five substates (SSs) are defined along the pathway via the fixed radius clustering method (1 to 17: red; 18 to 27: yellow; 28 to 35: green; 36 to 51: cyan; and 52 to 64: blue). Among the 64 images, 5 images (10, 23, 31, 44, and 57) are selected as five representative SSs.There are several computational tools to predict conformational transition pathways of proteins, such as morphing (16), normal mode analysis (17), or molecular dynamics (MD) simulation based on coarse-grained or atomistic models (18–21). However, large conformational changes of the Ca²⁺-ATPase happen on the milliseconds or slower time scales, which are not accessible in brute-force MD simulations (18–21) even when using MD-specialized supercomputers, such as Anton/Anton 2 (22, 23) or MDGRAPE-4A (24). In this study, we perform atomistic MD simulations with an enhanced conformational sampling method to investigate the conformational pathway and free energy profile in the transition between E1P⋅ADP⋅2Ca²⁺ and E2P. We utilize the mean-force string method (25) for obtaining one of the most probable transition pathways. The free energy profile along the pathway is then calculated with umbrella sampling (26). The same approach has been previously applied to adenylate kinase in solution (27) and multidrug transporter AcrB (28) and the ABC heme transporter (29) in biological membranes. A similar method, the string method with swarm trajectories (30), has been applied to several membrane proteins (31, 32). Das et al. applied the method to four conformational transitions of the Ca²⁺-ATPase, including the same step examined in the current study (33).In the current simulation study, we intend to compare the simulation results with those of existing structural and biochemical studies. In particular, the two intermediate states (E1P⋅2Ca²⁺ and E2P⋅2Ca²⁺) and the Ca²⁺-ATPase–lipid interactions in the E1P–E2P transition are examined using the simulation trajectories. The predicted interactions between phospholipids and basic sidechains of Ca²⁺-ATPase are compared with recent X-ray crystallography studies (34). We also investigate the effect of protonation states in the E1P–E2P transitions from atomistic MD simulations, which is difficult via experimental studies. By integrating structural, biochemical, and computational results, we shed light on the structural and energetic features of the E1P–E2P transition of the Ca²⁺-ATPase in unprecedented detail.     

Energy-Dependent Particle Size Distribution Models for Multi-Disc Mill

Comminution is important in the processing of biological materials, such as cereal grains, wood biomass, and food waste. The most popular biomaterial grinders are hammer and roller mills. However, the grinders with great potential in the processing of biomass are mills that use cutting, e.g., disc mills. When it comes to single-disc and multi-disc grinders, there are not many studies describing the relationships between energy, motion, material, and processing or describing the effect of grinding, meaning the size distribution of a product. The relationship between the energy and size reduction ratio of disc-type grinder designs has also not been sufficiently explored. The purpose of this paper was to develop models for the particle size distribution of the ground product in multi-disc mills depending on the variable process parameters, i.e., disc rotational velocity and, consequently, power consumption, and the relationship between the grinding energy and the shape of graining curves, which would help predict the product size reduction ratio for these machines. The experiment was performed using a five-disc mill, assuming the angular velocity of the grinder discs was variable. Power consumption, product particle size, and specific comminution energy were recorded during the tests. The Rosin–Rammler–Sperling–Bennet (RRSB) distribution curves were established for the ground samples, and the relationships between distribution coefficients and the average angular velocity of grinder discs, power consumption, and specific comminution energy were determined. The tests showed that the specific comminution energy increases as the size reduction ratio increases. It was also demonstrated that the RRSB distribution coefficients could be represented by the functions of angular velocities, power consumption, and specific comminution energy. The developed models will be a source of information for numerical modelling of comminution processes.     

Fatigue Behavior of Linear Friction Welded Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.1Si Dissimilar Welds

The use of joints fabricated from dissimilar titanium alloys allows the design of structures with local properties tailored to different service requirements. To develop welded structures for aerospace applications, particularly under critical loading, an understanding of the fatigue behavior is crucial, but remains limited, especially for solid-state technologies such as linear friction welding (LFW). This paper presents the fatigue behavior of dissimilar titanium alloys, Ti–6Al–4V (Ti64) and Ti–6Al–2Sn–4Zr–2Mo–0.1Si (Ti6242), joined by LFW with the aim of characterizing the stress versus number of cycles to failure (S-N) curves in both the low- and high-cycle fatigue regimes. Prior to fatigue testing, metallurgical characterization of the dissimilar alloy welds indicated softening in the heat-affected zone due to the retention of metastable β, and the typical practice of stress relief annealing (SRA) for alleviating the residual stresses was effective also in transforming the metastable β to equilibrated levels of α + β phases and recovering the hardness. Thus, the dissimilar alloy joints were fatigue-tested in the SRA (750 °C for 2 h) condition and their low- and high-cycle fatigue behaviors were compared to those of the Ti64 and Ti6242 base metals (BMs). The low-cycle fatigue (LCF) behavior of the dissimilar Ti6242–Ti64 linear friction welds was characterized by relatively high maximum stress values (~ 900 to 1100 MPa) and, in the high-cycle fatigue (HCF) regime, the fatigue limit of 450 MPa at 10⁷ cycles was just slightly higher than that of the Ti6242 BM (434 MPa) and the Ti64 BM (445 MPa). Fatigue failure of the dissimilar titanium alloy welds in the low-cycle and high-cycle regimes occurred, respectively, on the Ti64 and Ti6242 sides, roughly 3 ± 1 mm away from the weld center, and the transitioning was reasoned based on the microstructural characteristics of the BMs.     

Atomic Interactions and Order–Disorder Transition in FCC-Type FeCoNiAl1−xTix High-Entropy Alloys

Single-phase high-entropy alloys with compositionally disordered elemental arrangements have excellent strength, but show a serious embrittlement effect with increasing strength. Precipitation-hardened high-entropy alloys, such as those strengthened by L1₂-type ordered intermetallics, possess a superior synergy of strength and ductility. In this work, we employ first-principles calculations and thermodynamic simulations to explore the atomic interactions and order–disorder transitions in FeCoNiAl_1−xTi_x high-entropy alloys. Our calculated results indicate that the atomic interactions depend on the atomic size of the alloy components. The thermodynamic stability behaviors of L1₂ binary intermetallics are quite diverse, while their atomic arrangements are short-range in FeCoNiAl_1−xTi_x high-entropy alloys. Moreover, the order–disorder transition temperatures decrease with increasing Ti content in FeCoNiAl_1−xTi_x high-entropy alloys, the characteristics of order–disorder transition from first-principles calculations are in line with experimental observations and CALPHAD simulations. The results of this work provide a technique strategy for proper control of the order–disorder transitions that can be used for further optimizing the microstructure characteristics as well as the mechanical properties of FeCoNiAl_1−xTi_xhigh-entropy alloys.     

Lactate promotes plasticity gene expression by potentiating NMDA signaling in neurons

l-lactate is a product of aerobic glycolysis that can be used by neurons as an energy substrate. Here we report that in neurons l-lactate stimulates the expression of synaptic plasticity-related genes such as Arc, c-Fos, and Zif268 through a mechanism involving NMDA receptor activity and its downstream signaling cascade Erk1/2. l-lactate potentiates NMDA receptor-mediated currents and the ensuing increase in intracellular calcium. In parallel to this, l-lactate increases intracellular levels of NADH, thereby modulating the redox state of neurons. NADH mimics all of the effects of l-lactate on NMDA signaling, pointing to NADH increase as a primary mediator of l-lactate effects. The induction of plasticity genes is observed both in mouse primary neurons in culture and in vivo in the mouse sensory-motor cortex. These results provide insights for the understanding of the molecular mechanisms underlying the critical role of astrocyte-derived l-lactate in long-term memory and long-term potentiation in vivo. This set of data reveals a previously unidentified action of l-lactate as a signaling molecule for neuronal plasticity.The transfer of l-lactate from astrocytes to neurons was recently shown to be necessary for the establishment of long-term memory (LTM) in an inhibitory avoidance (IA) paradigm and for the maintenance of in vivo long-term potentiation (LTP) in the rodent hippocampus (1). This key role of l-lactate in neuronal plasticity mechanisms was demonstrated in experiments in which specific pharmacological and gene expression down-regulation interventions were implemented to prevent the production of l-lactate from glycogen—which is exclusively localized in astrocytes—and its release from these cells in the hippocampus during behavioral training (1). Such interventions completely prevented the establishment of LTM and their effect was fully reversed by the intrahippocampal administration of l-lactate during the training session. The fact that glucose at equicaloric concentrations only marginally mimicked the rescuing effect of l-lactate was taken as an unexpected indication that the primary mechanism of action of l-lactate on plasticity mechanisms was independent of its ability to act as an energy substrate. A role of l-lactate in memory processes was also recently shown in other behavioral paradigms (2, 3). We therefore set out to investigate the molecular mechanisms at the basis of the function of l-lactate on neuronal plasticity.Molecular mechanisms underlying both LTM and long-term plasticity include the induction of expression of a group of immediate early genes (IEGs) such as early growth response 1 (Zif268 or Egr1), CCAAT/enhancer binding protein (C/EBP), and proto-oncogene c-Fos (c-Fos) as well as activity-regulated cytoskeletal-associated protein (Arc or Arg3.1) as a direct effector protein at the synapse, which all participate to different physiological processes associated with neuronal plasticity (4–6). Although stimulation of expression of these IEGs is not restricted to plasticity processes, they are considered as key plasticity-related genes in sustaining such phenomena. In addition, late response genes such as brain-derived neurotrophic factor (BDNF) have also been demonstrated to be major intermediates of plasticity-related processes (7). A role of NMDA receptors (NMDARs) in such plasticity mechanisms is well-established (5, 8).In this article we describe a cascade of molecular events demonstrating that l-lactate stimulates plasticity-related gene expression in neurons through modulation of NMDAR activity associated with changes in redox cellular state. The induction of plasticity gene expression by l-lactate was observed in primary cultures of neurons as well as in vivo in the sensory-motor cortex of mice.     

Left Ventricular Longitudinal Myocardial Function in Overt Hypothyroidism: A Tissue Doppler Echocardiographic Study

Background: The aim of this study was to assess left ventricular (LV) myocardial regional function in overt hypothyroidism by use of tissue Doppler imaging and to compare the results to the hormonal profile and standard Doppler echocardiographic examination. Methods: Hypothyroidic (Group 1, n = 25) and euthyroidic patients (Group 2, n = 25) underwent transthorasic echocardiography, strain and strain rate imaging. Results: Standard echocardiography showed that patients with overt hypothyroidism had significantly longer isovolumic contraction time (IVCT) (P < 0.05), deceleration time (DT) (P = 0.014) and isovolumic relaxation time (IVRT) (P = 0.022). Tissue Doppler imaging showed that the mean peak systolic strain (SI) (16.47 ± 1.45 vs. 20.63 ± 1.51, P < 0.001), the mean peak systolic strain rate (SSR) (1.05 ± 0.13 vs. 1.47 ± 0.11, P < 0.001), the mean peak early diastolic strain rate (ESr) (1.72 ± 0.38 vs. 2.03 ± 0.25, P < 0.05) and the mean peak late diastolic strain rate (ASr) (1.22 ± 0.31 vs. 1.46 ± 0.32, P < 0.05) were significantly lower in Group 1 compared to Group 2. For all patients, the systolic strain and systolic strain rate parameters negatively correlated with thyroid stimulating hormone levels and positively correlated with the levels of free triiodothyronine (fT₃) and free tetraiodothyronine (fT₄). Conclusion: These results indicate that overt hypothyroidism is associated with early impairment in LV longitudinal myocardial function, and that tissue Doppler echocardiography is useful for the grading of disease and detection of early impairment. (ECHOCARDIOGRAPHY 2010;27:505‐511)     

Precipitation Behavior during Aging Operations in an Ultrafine-Grained Al–Cu–Mg Alloy Produced by High-Strain-Rate Processing

An ultrafine-grained (UFG) Al–Cu–Mg alloy (AA2024) was produced by surface mechanical grinding treatment (SMGT) with a high strain rate, and the precipitation behavior inside the grain and at the grain boundary was investigated. During SMGT, element segregation at the boundary was rarely observed, since the solute atoms were impeded by dislocations produced during SMGT. During early aging, the atomic fraction of Cu at the grain boundary with SMGT alloys was approximately 2.4-fold larger than that without SMGT alloys, the diffusion rate of Cu atoms from the grain toward the grain boundaries was accelerated with SMGT alloys, because a higher local elastic stress and diffusion path were provided by high-density dislocations. The combined action, in terms of the composition of the alloy, the atomic radius, the diffusion path, and the diffusion driving force provided by high-density dislocations with SMGT alloys, led to a Cu/Mg atomic ratio of approximately 6.8 at the grain boundary. The average size of the precipitates inside the grain was approximately 2- and 10-fold larger than that formed after later aging with and without SMGT alloys, due to more nucleation sites at dislocation located inside the grain with SMGT alloys having attracted and captured numerous solute atoms during the aging process.     

Computational Analysis of Mutations in the Receptor-Binding Domain of SARS-CoV-2 Spike and Their Effects on Antibody Binding

Currently, SARS-CoV-2 causing coronavirus disease 2019 (COVID-19) is responsible for one of the most deleterious pandemics of our time. The interaction between the ACE2 receptors at the surface of human cells and the viral Spike (S) protein triggers the infection, making the receptor-binding domain (RBD) of the SARS-CoV-2 S-protein a focal target for the neutralizing antibodies (Abs). Despite the recent progress in the development and deployment of vaccines, the emergence of novel variants of SARS-CoV-2 insensitive to Abs produced in response to the vaccine administration and/or monoclonal ones represent a potential danger. Here, we analyzed the diversity of neutralizing Ab epitopes and assessed the possible effects of single and multiple mutations in the RBD of SARS-CoV-2 S-protein on its binding affinity to various antibodies and the human ACE2 receptor using bioinformatics approaches. The RBD-Ab complexes with experimentally resolved structures were grouped into four clusters with distinct features at sequence and structure level. The performed computational analysis indicates that while single amino acid replacements in RBD may only cause partial impairment of the Abs binding, moreover, limited to specific epitopes, the variants of SARS-CoV-2 with multiple mutations, including some which were already detected in the population, may potentially result in a much broader antigenic escape. Further analysis of the existing RBD variants pointed to the trade-off between ACE2 binding and antigenic escape as a key limiting factor for the emergence of novel SAR-CoV-2 strains, as the naturally occurring mutations in RBD tend to reduce its binding affinity to Abs but not to ACE2. The results provide guidelines for further experimental studies aiming to identify high-risk RBD mutations that allow for an antigenic escape.     

Precipitation during Quenching in 2A97 Aluminum Alloy and the Influences from Grain Structure

The quench-induced precipitation and subsequent aging response in 2A97 aluminum alloy was investigated based on the systematic microstructure characterization. Specifically, the influence on precipitation from grain structure was examined. The results indicated the evident influence from the cooling rate of the quenching process. Precipitation of T₁ and δ′ phase can hardly occur in the specimen exposed to water quenching while become noticeable in the case of air cooling. The yield strength of 2A97-T6 alloy de-graded by 234 MPa along with a comparable elongation when water quenching was replaced by air cooling. Sub-grains exhibited a much higher sensitivity to the precipitation during quenching. The presence of dislocations in sub-grains promoted the quench-induced precipitation by acting as nucleation sites and enhancing the diffusion of the solute. A quenching rate of 3 °C/s is tolerable for recrystallized grains in 2A97 Al alloy but is inadequate for sub-grains to inhibit precipitation. The study fosters the feasibility of alleviating quench-induced precipitation through cultivating the recrystallization structure in highly alloyed Al–Cu–Li alloys.     

Plasmid-based human norovirus reverse genetics system produces reporter-tagged progeny virus containing infectious genomic RNA

Human norovirus (HuNoV) is the leading cause of gastroenteritis worldwide. HuNoV replication studies have been hampered by the inability to grow the virus in cultured cells. The HuNoV genome is a positive-sense single-stranded RNA (ssRNA) molecule with three open reading frames (ORFs). We established a reverse genetics system driven by a mammalian promoter that functions without helper virus. The complete genome of the HuNoV genogroup II.3 U201 strain was cloned downstream of an elongation factor-1α (EF-1α) mammalian promoter. Cells transfected with plasmid containing the full-length genome (pHuNoV_U201F) expressed the ORF1 polyprotein, which was cleaved by the viral protease to produce the mature nonstructural viral proteins, and the capsid proteins. Progeny virus produced from the transfected cells contained the complete NoV genomic RNA (VP1, VP2, and VPg) and exhibited the same density in isopycnic cesium chloride gradients as native infectious NoV particles from a patient’s stool. This system also was applied to drive murine NoV RNA replication and produced infectious progeny virions. A GFP reporter construct containing the GFP gene in ORF1 produced complete virions that contain VPg-linked RNA. RNA from virions containing the encapsidated GFP-genomic RNA was successfully transfected back into cells producing fluorescent puncta, indicating that the encapsidated RNA is replication-competent. The EF-1α mammalian promoter expression system provides the first reverse genetics system, to our knowledge, generalizable for human and animal NoVs that does not require a helper virus. Establishing a complete reverse genetics system expressed from cDNA for HuNoVs now allows the manipulation of the viral genome and production of reporter virions.Human noroviruses (HuNoVs) belong to the genus Norovirus of the family Caliciviridae and are the predominant cause of epidemic and sporadic cases of acute gastroenteritis worldwide (1, 2). HuNoVs are spread through contaminated water or food, such as oysters, shellfish, or ice, and by person-to-person transmission (3, 4). Although HuNoVs were identified more than 40 y ago, our understanding of the replication cycle and mechanisms of pathogenicity is limited, because these viruses remain noncultivatable in vitro, a robust small animal model to study viral infection is not available, and reports of successful passage of HuNoVs in a 3D cell culture system have not been reproduced (5–7). Recently, a murine model for HuNoV infection was described that involves intraperitoneal inoculation of immunocompromised mice (8); its generalizability and robustness for studying individual HuNoVs and many aspects of HuNoV biology remain to be established. Gnotobiotic pigs can support replication of a HuNoV genogroup II (GII) strain with the occurrence of mild diarrhea, fecal virus shedding, and immunofluorescent (IF) detection of both structural and nonstructural proteins in enterocytes (9). Previous systems to express the HuNoV genome from cloned DNA using T7/vaccinia systems showed that mammalian cells can produce progeny virus (10, 11), but these systems are not sufficiently efficient to be widely used to propagate HuNoVs in vitro. The factors responsible for the block(s) of viral replication using standard cell culture systems remain unknown.The HuNoV genome is a positive-sense ssRNA of ∼7.6 kb that is organized in three ORFs: ORF1 encodes a nonstructural polyprotein, and ORF2 and ORF3 encode the major and minor capsid proteins VP1 and VP2, respectively. Because of the lack of an in vitro system to propagate HuNoV, features of their life cycle have been inferred from studies using other animal caliciviruses and murine NoV (MNV) that can be cultivated in mammalian cell cultures (12). A 3′ coterminal polyadenylated subgenomic RNA is produced within infected cells. Both genomic and subgenomic RNAs have the same nucleotide sequence motif at their 5′ ends, and they are believed for HuNoVs and shown for MNV to be covalently linked to the nonstructural protein VPg at the 5′ ends (10, 13). During MNV infection of cells, nonstructural proteins are expressed from genomic RNA and form an RNA replication complex that generates new genomic RNA molecules as well as subgenomic RNAs encoding VP1, VP2, and the unique protein called VF1 (14). After expression of the structural proteins from subgenomic RNA molecules, the capsid is assembled, and viral RNA is encapsidated before progeny release. Previous reverse genetics systems for HuNoV used helper vaccinia MVA/T7 virus-based systems. Although helper virus-free systems have been developed for MNV (15, 16), no such system is available for HuNoVs. To overcome these problems, we established a reverse genetics system driven by a mammalian elongation factor-1α (EF-1α) promoter without helper virus and then modified this system to package a reporter gene (GFP) into ORF1.     

Energy Relaxation and Electron–Phonon Coupling in Laser-Excited Metals

The rate of energy transfer between electrons and phonons is investigated by a first-principles framework for electron temperatures up to Te = 50,000 K while considering the lattice at ground state. Two typical but differently complex metals are investigated: aluminum and copper. In order to reasonably take the electronic excitation effect into account, we adopt finite temperature density functional theory and linear response to determine the electron temperature-dependent Eliashberg function and electron density of states. Of the three branch-dependent electron–phonon coupling strengths, the longitudinal acoustic mode plays a dominant role in the electron–phonon coupling for aluminum for all temperatures considered here, but for copper it only dominates above an electron temperature of Te = 40,000 K. The second moment of the Eliashberg function and the electron phonon coupling constant at room temperature Te=315 K show good agreement with other results. For increasing electron temperatures, we show the limits of the T=0 approximation for the Eliashberg function. Our present work provides a rich perspective on the phonon dynamics and this will help to improve insight into the underlying mechanism of energy flow in ultra-fast laser–metal interaction.     

Tensile Properties and Microstructure Evolutions of Low-Density Duplex Fe–12Mn–7Al–0.2C–0.6Si Steel

An austenite-ferrite duplex low-density steel (Fe–12Mn–7Al–0.2C–0.6Si, wt%) was designed and fabricated by cold rolling and annealing at different temperatures. The tensile properties, microstructure evolution, deformation mechanism and stacking fault energy (SFE) of the steel were systemically investigated at ambient temperature. Results show two phases of fine equiaxed austenite and coarse band-like δ-ferrite in the microstructure of the steel. With increasing annealing temperature, the yield and tensile strengths decrease while the total elongation increases. At initial strains, the deformation is mainly concentrated in the fine austenite and grain boundaries of the coarse δ-ferrite, and the interior of the coarse δ-ferrite gradually deforms with further increase in the strain to 0.3. No twinning-induced plasticity (TWIP) or transformation-induced plasticity (TRIP) occurred during the tensile deformation. Considering element segregation and two-phase proportion, the chemical composition of austenite was measured more precisely. The SFE of the austenite is 39.7 mJ/m², and the critical stress required to produce deformation twins is significantly higher than the maximum flow stress of the steel.     

Use of Hydrogen–Rich Gas in Blast Furnace Ironmaking of V–bearing Titanomagnetite: Mass and Energy Balance Calculations

The iron and steel industry is a major CO₂ emitter and an important subject for the implementation of carbon emission reduction goals and tasks. Due to the complex ore composition and low iron grade, vanadium–bearing titanomagnetite smelting in a blast furnace consumes more coke and emits more carbon than in an ordinary blast furnace. Injecting hydrogen–rich gas into blast furnace can not only partially replace coke, but also reduce the carbon emission. Based on the whole furnace and zonal energy and mass balance of blast furnace, the operation window of the blast furnace smelting vanadium–bearing titanomagnetite is established in this study on the premise that the thermal state of the blast furnace is basically unchanged (raceway adiabatic flame temperature and top gas temperature). The effects of different injection amounts of hydrogen–rich gases (shale gas, coke oven gas, and hydrogen) on raceway adiabatic flame temperature and top gas temperature, and the influence of blast temperature and preheating temperature of hydrogen–rich gases on operation window are calculated and analyzed. This study provides a certain theoretical reference for the follow–up practice of hydrogen–rich smelting of vanadium–bearing titanomagnetite in blast furnace.