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Due to their high computational efficiency, the coarse-grained water models are of particular importance for practical molecular simulations of gas hydrates. In these models, the mW model is successfully used to study many thermodynamics and dynamics of methane hydrate. Yet, despite several decades of intense research, the mW model is still found to overestimate the melting temperature of methane hydrate. We here employ the minimum mean squared error estimation to revisit the key parameter of the mW model, which determines the strength of the tetrahedral angle of the water system. Relying on the free energy calculations, we first estimate the chemical potentials of water in the liquid phase for temperatures at which methane hydrate forms. We then turn to the mean squared error to describe the chemical potential deviation between the mW model and the TIP4P/ice model (the latter could reproduce the experimental phase diagram of methane hydrate). By minimizing the mean squared error, we finally have an optimized parameter for the mW model. In this part, we also discuss the pressure effect on such reparameterization procedure. Moreover, relying on the direct coexistence method, the melting temperature determined using the reparameterized mW model is found to be consistent with the experimental data. This strategy provides a means to improve the coarse-grained model to match the experimental observations for temperatures in the range of interest. [ABSTRACT FROM AUTHOR]

With the help of the one-dimensional random Potts-like model, we study the origins of fine structures observed on differential melting profiles of double-stranded DNA. We theoretically assess the effects of sequence arrangement on DNA melting curves through the comparison of results for random, correlated, and block sequences. Our results re-confirm the smearing out of the fine structure with the increase in chain length for all types of sequence arrangements and suggest that the fine structure is a finite-size effect. We have found that the fine structures on melting curves of chains comprised of blocks with correlations in sequence are more persistent, probably because of increased sequence disorder the blocks introduce. Many natural DNAs show a well-expressed fine structure of melting profiles. Our results for block sequences may suggest the existence of such sequence motifs in natural DNA sequences. [ABSTRACT FROM AUTHOR]

Homogenous melting at superheating temperature is commonly described by classical nucleation theory (CNT), but the atomic mechanism of the formation and development of critical liquid nuclei is still unclear. Molecular dynamics simulations were conducted to analyze the melting process of Ta. It is found that the process of subcritical liquid clusters evolving into critical liquid nucleus occupies most of the melting time, and merging between neighboring liquid clusters is the main path for subcritical liquid clusters to grow in size. Total melting time is strongly affected by the distribution of formation sites of subcritical liquid clusters, which has been considered random in homogenous melting. This work depicts a clear picture of the formation and development of liquid phase during the homogeneous melting process at superheating temperature and suggests an internal factor of melting mechanism. [ABSTRACT FROM AUTHOR]

Glaciologist Rob DeConto's research on polar climate change, specifically focusing on glaciers and ice sheets, is discussed in this article. DeConto explains the differences between Antarctica and Greenland and the challenges of understanding how the Antarctic ice sheet will behave in a warmer world. He also discusses the potential dangers of marine ice sheet instability and the impact of melting ice shelves on sea-level rise. The article emphasizes the uncertainties surrounding the rate of sea-level rise and the need for further research in this area. It highlights the term "deep uncertainty" used by the Intergovernmental Panel on Climate Change (IPCC) to describe the situation and the conservative nature of current projections. The author emphasizes the need for action to address the melting of ice sheets, as it poses a threat to infrastructure worldwide. [Extracted from the article]

Body-centered cubic bismuth (bcc-Bi) has long been considered an ideal pressure standard/calibrant; thus, the accurate knowledge of both its equation of state (EOS) and melting curve is of primary importance for future high pressure and high temperature experiments. However, its melting curve has never been measured experimentally beyond 5 GPa, and several theoretical calculations do not agree with each other and, in fact, differ by as much as a factor of 2 with regard to the bcc-Bi melting point at 50 GPa. Here, we present the calculation of the melting curve of bcc-Bi to 400 GPa via quantum molecular dynamics simulations using the Z method implemented with VASP. We also present the ab initio EOS of bcc-Bi as well as its principal Hugoniot, which both appear to be in excellent agreement with the available experimental data. At 100 GPa, the temperature extent (from zero to melt) of bcc-Bi is comparable to that of gold. At pressures of $\stackrel {\gt }{ \sim }500$ GPa, the melting curve of bcc-Bi is (quasi-)parallel to, being ${\sim } 1000$ K below that of rhenium, the highest melter above ${\sim } 30$ GPa among the elements of the third row of the periodic table, which makes bcc-Bi the second highest melter behind Re. [ABSTRACT FROM AUTHOR]

The elasticity of polymer networks, formed by cross-linking high molecular mass polymers in the melt state and then swollen by a solvent, involves contributions from both the presence of cross-link network junctions and the interchain interactions associated with the combined effect of excluded volume interactions and topological constraints that become modified when the network is swollen. We test the capacity of the previously developed localization model of rubber elasticity, a mean field "tube model," to describe changes in elasticity observed in classical experimental studies of the mechanical properties of this type of network. In order to obtain a satisfactory comparison to the experiments, it was found to be necessary to account for the independently observed tendency of the network junctions to become localized in the network with appreciable swelling, as well as the interchain interactions emphasized in previous discussions of the localization model. [ABSTRACT FROM AUTHOR]

The melting temperature is important for materials design because of its relationship with thermal stability, synthesis, and processing conditions. Current empirical and computational melting point estimation techniques are limited in scope, computational feasibility, or interpretability. We report the development of a machine learning methodology for predicting melting temperatures of binary ionic solid materials. We evaluated different machine-learning models trained on a dataset of the melting points of 476 non-metallic crystalline binary compounds using materials embeddings constructed from elemental properties and density-functional theory calculations as model inputs. A direct supervised-learning approach yields a mean absolute error of around 180 K but suffers from low interpretability. We find that the fidelity of predictions can further be improved by introducing an additional unsupervised-learning step that first classifies the materials before the melting-point regression. Not only does this two-step model exhibit improved accuracy, but the approach also provides a level of interpretability with insights into feature importance and different types of melting that depend on the specific atomic bonding inside a material. Motivated by this finding, we used a symbolic learning approach to find interpretable physical models for the melting temperature, which recovered the best-performing features from both prior models and provided additional interpretability. [ABSTRACT FROM AUTHOR]

Water can be vitrified if it is cooled at high rates, which makes it possible to outrun crystallization in so-called no man's land, a range of deeply supercooled temperatures where water crystallizes rapidly. Here, we study the reverse process in pure water samples by flash melting amorphous ice with microsecond laser pulses. Time-resolved electron diffraction reveals that the sample transiently crystallizes despite a heating rate of more than 5 × 106 K/s, even though under the same conditions, vitrification can be achieved with a similar cooling rate of 107 K/s. Moreover, we observe different crystallization kinetics for amorphous solid water and hyperquenched glassy water. These experiments open up new avenues for elucidating the crystallization mechanism of water and studying its dynamics in no man's land. They also add important insights into the laser melting and revitrification processes that are integral to the emerging field of microsecond time-resolved cryo-electron microscopy. [ABSTRACT FROM AUTHOR]

By employing brute-force molecular dynamics, umbrella sampling, and seeding simulations, we investigate homogeneous nucleation during melting and freezing of hard spheres. We provide insights into these opposing phase transitions from the standpoint of classical nucleation theory. We observe that melting has both a lower driving force and a lower interfacial tension than freezing. The lower driving force arises from the vicinity of a spinodal instability in the solid and from a strain energy. The lower interfacial tension implies that the Tolman lengths associated with melting and freezing have opposite signs, a phenomenon that we interpret with Turnbull's rule. Despite these asymmetries, the nucleation rates for freezing and melting are found to be comparable. [ABSTRACT FROM AUTHOR]

Titanium (Ti) is one of the most important metals used in several industrial applications, and the presence of spherical defect reduces its strength and stability. We simulate the melting of Ti crystals with a spherical void of radii 0.6, 0.8, 1.0, and 1.5 nm and also of the crystal without it. Ti is modeled using embedded atom method ,and all crystals are heated at 1 atm from 300 to 2200 K till it melts completely. All molecular dynamics trajectories are analyzed using radial distribution functions, bond-orientational order parameters, Voronoi tessellation, and velocity auto-correlation functions. The results show that 0.6, 0.8, 1.0, and 1.5 nm voids fill before the crystals melt and they fill immediately within few picoseconds; thereafter, atoms rearrange/order to crystal like arrangements, wherein overall crystallinity remains hcp for crystals with 0.6 and 0.8 nm void and changes to bcc for the crystals with 1.0 and 1.5 nm voids. For all crystals with and without void, melting takes place with the loss of both long- and short-range orders and not from liquid like nuclei as proposed by classical nucleation theory. [ABSTRACT FROM AUTHOR]

With the aim of producing realistic coarse-grained models of homopolymers, we introduce a tabulated backbone-oriented anisotropic potential. The parameters of the model are optimized using statistical trajectory matching. The impact of grain anisotropy is evaluated at different coarse-graining levels using cis-polybutadiene as a test case. We show that, at the same time, tuning the aspect ratio of the grains can lead to a better density and structure and may reduce the unphysical bond crossings by up to 90%, without increasing the computation time too much and thereby jeopardizing the main advantage of coarse-grained models. [ABSTRACT FROM AUTHOR]

Polyrotaxanes, which consist of mechanically interlocked bonds with rings threaded onto soft polymer chains, exhibit unique mechanical properties and find applications in diverse fields. In this study, we investigate the anomalous segmental dynamics of supercooled polyrotaxane melts using coarse-grained molecular dynamics simulations. Our simulations reveal that the presence of rings effectively reduces the packing efficiency, resulting in well-contained local motion even below the glass transition temperature. We also observe variations in dynamical free volume, characterized by the Debye–Waller factor, which shows a minimum at a ring coverage of 0.1 on threading chains. Such a non-monotonic dependence on coverage shows great consistency in structural relaxation time and dynamic heterogeneity. Specifically, the high segmental mobility of threading linear chains at large coverage can be attributed to the increased dynamical free volume due to supported rigid rings. However, such anomalous segmental dynamics is limited to length scales smaller than one ring size. Beyond this characteristic length scale, the diffusion is dominated by topological constraints, which significantly reduce the mobility of polyrotaxanes and enhance the dynamic heterogeneity. These findings offer microscopic insights into the unique packing structures and anomalous segmental dynamics of supercooled polyrotaxane melts, facilitating the design of advanced materials based on mechanical interlocking polymers for various applications. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs) feature complex phase transitions, including polymorphism, melting, vitrification, and polyamorphism. Experimentally probing their structural evolution during transitions involving amorphous phases is a significant challenge, especially at the medium-range length scale. To overcome this challenge, here we first train a deep learning-based force field to identify the structural characteristics of both crystalline and non-crystalline ZIF phases. This allows us to reproduce the structural evolution trend during the melting of crystals and formation of ZIF glasses at various length scales with an accuracy comparable to that of ab initio molecular dynamics, yet at a much lower computational cost. Based on this approach, we propose a new structural descriptor, namely, the ring orientation index, to capture the propensity for crystallization of ZIF-4 (Zn(Im)2, Im = C3H3N2-) glasses, as well as for the formation of ZIF-zni (Zn(Im)2) out of the high-density amorphous phase. This crystal formation process is a result of the reorientation of imidazole rings by sacrificing the order of the structure around the zinc-centered tetrahedra. The outcomes of this work are useful for studying phase transitions in other metal-organic frameworks (MOFs) and may thus guide the development of MOF glasses.

From the perspective of a bond-order-length-strength correlation, we put forward an analytical solution to describe the size, shape, and wall thickness dependency of melting temperature, entropy, and enthalpy for metallic nanostructures. Theoretical reproduction of measurements clarified that (i) when the crystal size reduces, the atomic coordination number lowers, the atomic cohesive energy decreases, and the surface-to-volume ratio increases; (ii) at the same equivalent radius, with the decrease in the number of sides for polyhedral nanoparticles and polygonal nanowires or nanotubes, the melting temperature, entropy, and enthalpy depress; and (iii) the melting temperature, entropy, and enthalpy of nanotubes are always lower than those of nanowires with the same cross-sectional radius. The present formulation is accurate and convenient, which not only shows deeper insight into the physical origins of a melting thermodynamic property response to perturbations but also provides guidance for the design and optimization of electronic nanodevices. [ABSTRACT FROM AUTHOR]

Solar radiative heating and melting of lake and sea ice is a geophysical problem that has attracted the attention of researchers for many years. This problem is important in connection with the current global change of the climate. Physical and computational models of the process are suggested in the paper. Analytical solutions for the transfer of solar radiation in light-scattering snow cover and ice are combined with numerical calculations of heat transfer in a multilayer system. The thermal boundary conditions take into account convective heat losses to the ambient air and radiative cooling in the mid-infrared window of transparency of the cloudless atmosphere. The study begins with an anomalous spring melting of ice on the large high-mountain lakes of Tibet. It was found that a thick ice layer not covered with snow starts to melt at the ice-water interface due to volumetric solar heating of ice. The results of the calculations are in good agreement with the field observations. The computational analysis showed a dramatic change in the process when the ice is covered with snow. A qualitative change in the physical picture of the process occurs when the snow cover thickness increases to 20–30 cm. In this case, the snow melting precedes ice melting and water ponds are formed on the ice surface. This is typical for the Arctic Sea in polar summer. Known experimental data are used to estimate the melting of sea ice under the melt pond. Positive or negative feedback related to the specific optical and thermal properties of snow, ice, and water are discussed. [ABSTRACT FROM AUTHOR]

The deposition and accumulation of inclusions is the dominant mechanism in nozzle clogging of the submerged entry nozzle. Previous modeling attempts of inclusion deposition have assumed that any contact between the inclusion and nozzle wall results in adhesion. Herein, an Eulerian–Lagrangian simulation with a stochastic adhesion model is used to study the effects of different inclusion‐wall sticking probability (Swall) on inclusion deposition. The results indicate that inclusion deposition is affected by both melt height and Swall. Lower melt heights result in increased deposition deeper into the nozzle and greater maximum particle area number density. The effect of Swall on the global deposition ratio can be divided into two regimes. When Swall increases from 0–0.05, there is a rapid rise in the global deposition ratio. When Swall > 0.05, the global deposition ratio increases only modestly with Swall. Changes to Swall also affect the location of deposition. When Swall decreases, the high and mid cases show greater relative deposition in the cone and taper sections of the nozzle, while the low melt height case shows greater relative deposition in the straight section of the nozzle. [ABSTRACT FROM AUTHOR]

Zn/FeT (FeT=Fe2+ + Fe3+) ratios in primitive melts have been proposed as a redox proxy to assess the redox states of the upper mantle. However, to effectively use the melt Zn/FeT ratio as a redox proxy, it is necessary to compare variations of melt Zn/FeT ratios induced by changes in oxygen fugacity (f O 2) with variations due to changes in Zn-Fe contents and mineralogy of the sources. Here we show that the melt Zn/FeT ratio variation caused by f O 2 change can be expressed as Δ(Zn m / Fe m T) = (Zn per / Fe per T)* Δ (F e m 2 + / F e m T) /(D Zn per/m / D Fe 2+ per/m). Zn/FeT ratios in most arc and MORB peridotites (Zn per / Fe per T) are 9.0 ± 1.0*10−4, and melt Fe2+/FeT ratio variation resulted from f O 2 change [ Δ (F e m 2 + / F e m T) ] can be easily obtained by the existing model. Hence, if the Zn and Fe2+ partition coefficients (D Zn per/m and D Fe 2+ per/m) between melt and peridotite are known, the melt Zn/FeT ratio variation resulting from f O 2 change can be estimated. In this study, we determined D Zn between olivine, orthopyroxene, clinopyroxene and basaltic melts at 0.75–2.5 GPa and 1250–1450 ℃. Our data show that melt composition (expressed as MgO content) dominantly controls the mineral-melt Zn partitioning under peridotite melting conditions. These data, along with published mineral-melt D Fe 2+ data, enable us to calculate appropriate D Zn per/m / D Fe 2+ per/m , which is 0.78 ± 0.02 under arc and MORB spinel peridotite melting conditions. Based on these parameters, the calculated average melt Zn/FeT ratio variation caused by per log unity f O 2 change in typical f O 2 span of arc and MORB mantles is only ∼ 0.69 ± 0.20*10−4. Alternatively, melt Zn/FeT ratio variations caused by changes in Zn-Fe contents and mineralogy of peridotites are ±1.10*10−4. These findings indicate that melt Zn/FeT ratio variation induced by one log units f O 2 change is on the same order of magnitude as those caused by changes in Zn-Fe contents and mineralogy of peridotites. Therefore, unless the precise chemical and mineralogical compositions of the mantle sources can be determined independently, the melt Zn/FeT redox proxy is unsuitable for tracing the mantle f O 2. Our study, combined with recent works on melt Cu and V/Sc redox proxies, suggests that these redox proxies, previously considered as the strongest evidence for a reduced arc mantle, might not support the idea of a reduced arc mantle. [ABSTRACT FROM AUTHOR]

The melting of scrap and hot briquetted iron (HBI) in an AC electric arc furnace (EAF) is simulated by an advanced 3D computational fluid dynamics (CFD) model that captures the arc heating, the scrap/HBI melting process, and the solid collapse mechanisms. The CFD model is used to simulate a scenario where charge layering and EAF power profiles are provided by a real EAF operation. CFD simulation of the EAF operation shows proper prediction of the charge melting when compared with standard industry practice. Namely, the CFD model predicts a 32.5%/67.5% ratio of solid/liquid steel at the beginning of refining, which approaches the 30%/70% ratio used in standard practice. Based on this prediction, the melting rate in the CFD results differs by 8.3% from actual EAF operation. The impact of charge layering on melting is also investigated. CFD results show that distributing charge material into a greater number of layers in the first bucket (10 layers as compared to 4) enhances the melting rate by 12%. However, including dense material at the bottom of the furnace deteriorates melting performance, reducing the impact of the number of layers of the charge. The CFD platform can be used to optimize the use of HBI/scrap in real EAF operations and to determine best recipe practices. [ABSTRACT FROM AUTHOR]

In this work, the corrosion behavior of rare‐earth Lu4Hf3O12 ceramic when exposed to a CaO‐FeO1.5‐AlO1.5‐SiO2 (CFAS) environment at a temperature of 1400°C was investigated, with a focus on exploring the associated phase transformation, microstructure evolution, and corrosion reaction mechanism. Results reveal that during the corrosion process, the CFAS melt infiltrates Lu4Hf3O12 particles through cracks, resulting in the formation of a continuous reaction layer. This reaction leads to the generation of several high‐melting‐point garnets, including HfO2, Lu3Al5O12, Ca3Fe2(SiO4)3 (Ca‐Fe garnet), and Ca3Al2Si3O12 (Grossular). These garnets effectively fill the voids within the Lu4Hf3O12 ceramics, preventing further infiltration of the CFAS melts. As time progresses, the rate of the reaction gradually increases, while the rate of infiltration consistently decreases. Consequently, a relatively stable corrosion layer is achieved, effectively impeding further corrosion. [ABSTRACT FROM AUTHOR]

The upper mantle low velocity zone is often attributed to partial melting at the lithosphere-asthenosphere boundary. This implies that basaltic melts may be stable along plausible geotherms due to the freezing point depression in the presence of water and other incompatible impurities. However, the freezing point depression (ΔT) as a function of water content in the near-solidus basaltic melt (cH2O) cannot be precisely determined from peridotite melting experiments because of difficulties in recovering homogeneous basaltic glasses at high pressures. We therefore used an alternative approach to reinvestigate and accurately constrain the ΔT–cH2O relationship for basaltic melts at the low water fugacities that are expected in the upper mantle. Internally heated pressure vessel (IHPV) experiments were performed at water-saturated conditions in the anorthite-diopside-H2O system at confining pressures of 0.02 to 0.2 GPa and temperatures between 940 and 1450 ℃. We determined the water-saturated solidus, and obtained ΔT by combining our data with reports of dry melting temperatures in the anorthite-diopside system. In another series of experiments, we measured water solubility in haplobasaltic melts and extrapolated cH2O to pressures and temperatures of the water-saturated solidus. By combining the results from these two series of experiments, we showed that the effect of water on ΔT was previously underestimated by at least 50 ℃. The new ΔT–cH2O relationship was then used to revise predictions of melt distribution in the upper mantle. Hydrous melt is almost certainly stable beneath extensive regions of the oceanic lithosphere, and may be present in younger and water-enriched zones of the subcontinental mantle. [ABSTRACT FROM AUTHOR]

In order to explore the frost heave and thaw settlement characteristics of soil layers in the Sanya Estuary Channel Project, the frost heave rate and thaw settlement coefficient of gravel sand, fine sand, silty clay, and clay are obtained. The most unfavorable soil layers are then compared and analyzed. The variation law of frost heave and thaw settlement performance of the most unfavorable soil layer under different water content is studied. The results are as follows: (1) The freezing stage of the passage through the typical soil layer is divided into four stages: frost shrinkage, rapid frost heave, slow frost heave, and frost heave stability. The melting stage is divided into three stages: slow thaw settlement, rapid thaw settlement, and thaw settlement stability. (2) The most unfavorable soil layer in the typical soil layer of the Sanya Estuary Channel Project is silty clay, with a frost heave rate and thaw settlement coefficient of 4.51% and 5.88% at −28 °C. (3) The frost heave and thaw settlement performance of the most unfavorable soil layer is linearly related to water content. The larger the water content, the greater the frost heave rate and thaw settlement coefficient, and the more prone to damage. [ABSTRACT FROM AUTHOR]

Spiral tube heat exchangers have been widely used in phase change energy storage due to the compact structure and large heat transfer area. Therefore, this study numerically analyzes the effects of spiral tube diameter, number of rotations, and unsteady heat source on the melting process in conical spiral tube energy storage tanks using Fluent software. The results indicate that when the tube diameter is increased from 8 to 11 mm and the number of rotations is increased from 5 to 8, the melting time is extended by 15.74% and 17.83%, respectively. The energy storage capacity increases by 0.64% and 1.83%, respectively. The average energy storage rate decreases by 13.05% and 13.58%, respectively. Furthermore, the sinusoidal wave heat source with small heat source periods has little effect on the melting process, while large heat source periods can significantly accelerate the melting. And the influence of amplitudes on the thermal storage performance under large heat source periods is more obvious. When the heat source period is increased from 2 to 160 min and the amplitude is increased from 5 to 20 K, the melting time is reduced by 24.50% and 17.20%, respectively. The total energy storage capacity decreases by 6.36% and increases by 1.62%, respectively. The average energy storage rate increases by 24.03% and 22.74%, respectively. The study provides guidance for the performance optimization of spiral tube phase change systems. [ABSTRACT FROM AUTHOR]

Purpose: The study aims to ascertain the influence of solder conductive particle types and substrate widths on the current carrying capability of flex-on-board (FOB) assemblies. By comparing Sn58Bi and SAC305 particles and varying substrate widths, the research sought to provide insights into the stability and performance of solder joints under different scenarios, particularly in high-power applications. Design/methodology/approach: The study used a comprehensive design/methodology, encompassing the investigation of solder conductive particle types (Sn58Bi and SAC305) and substrate widths on the current carrying capability of FOB assembly. Stable solder joints were obtained by manipulating the curing speed of anisotropic conductive films for both particle types. Various tests were conducted, including current carrying capability assessments under differing conditions. Findings: The study revealed that larger substrate widths yielded higher current carrying capability due to increased contact area and reduced contact resistance. Notably, solder joints remained stable beyond the solder melting temperature due to encapsulation by cured epoxy resin. SAC305 solder joints exhibited superior current carrying capability over Sn58Bi in continuous high-voltage conditions. The results emphasized the stability of SAC305 solder joints and their suitability for robust interconnections in high-power FOB assemblies. Originality/value: This study contributes by offering a comprehensive assessment of the impact of solder particle types and substrate widths on solder joint performance in FOB assemblies. The finding that SAC305 joints outperform Sn58Bi under continuous high-voltage conditions adds significant value. Moreover, the observation of stable solder joints beyond solder melting temperature due to resin encapsulation introduces a novel aspect to solder joint reliability. These insights provide valuable guidance for designing robust and high-performance interconnections in demanding applications. [ABSTRACT FROM AUTHOR]

The thick crust of the southern Tibetan and central Andean plateaus includes high-conductivity, low-velocity zones ascribed to partial melt. The melt origin and effect on plateau uplift remain speculative, in particular if plateau uplift happens before continental collision. The East Anatolian Plateau (EAP) has experienced similar, more recent uplift but its structure is largely unknown. Here we present an 80 km deep geophysical model across EAP, constrained by seismic receiver functions integrated with interpretation of gravity data and seismic tomographic, magnetotelluric, geothermal, and geochemical models. The results indicate a 20 km thick lower crustal layer and a 10 km thick mid-crustal layer, which both contain pockets of partial melt. We explain plateau uplift by isostatic equilibration following magmatism associated with roll-back and break-off of the Neo-Tethys slab. Our results suggest that crustal thickening by felsic melt and mafic underplate are important for plateau uplift in the EAP, Andes and Tibet. Partially molten middle and underplated lower crust may control isostatic plateau uplift, with uplift duration corelated to middle crustal thickness, which determines the height and crustal thickness of the Anatolian, Tibetan and Andean plateaux [ABSTRACT FROM AUTHOR]

To accurately characterize the geometric features in the repair of Ti-6Al-4 V alloy, a laser cladding mathematical model was developed and experimentally validated. The model employed a quartic polynomial function to analyze the geometric features of the clad layer, investigating correlations among deposition angle, clad layer width, melt pool depth, and clad layer area. Additionally, it utilized a quadratic polynomial function to characterize the geometric profile of the melt pool, establishing relationships involving clad layer width, melt pool depth, and melt pool area simultaneously. By means of the areas of the cladding layer and the melt pool, the value of the dilution rate can be obtained. Subsequently, the measured and predicted values of the clad layer, melt pool, and dilution rate were compared. The results demonstrated the mathematical model's capability to accurately forecast geometric features in laser cladding. Furthermore, an orthogonal experiment was conducted to investigate how process parameters—laser power, scanning speed, and powder feeding rate—affect the geometric dimensions (height, width, and melt pool depth) of single-pass, single-layer cladding, and to elucidate the underlying reasons. These investigations offered theoretical insights and practical guidelines for controlling the clad layer, melt pool, and dilution rate. [ABSTRACT FROM AUTHOR]

The ability to initiate DNA replication is a critical step in the proliferation of all organisms. In bacteria, this process is mediated by an ATP‐dependent replication initiator protein, DnaA, which recognizes and melts replication origin (oriC) elements. Despite decades of biochemical and structural work, a mechanistic understanding of how DnaA recognizes and unwinds oriC has remained enigmatic. A recent study by Pelliciari et al. provides important new structural insights into how DnaA from Bacillus subtilis recognizes and processes its cognate oriC, showing how DnaA uses sequence features encoded in the origin to engage melted DNA. Comparison of the DnaA‐oriC structure with archaeal/eukaryl replication origin complexes based on Orc‐family proteins reveals a high degree of similarity in origin engagement by initiators from di domains of life, despite fundamental differences in origin melting mechanisms. These findings provide valuable insights into bacterial replication initiation and highlight the intriguing evolutionary history of this fundamental biological process. [ABSTRACT FROM AUTHOR]

Exploding bridgewire detonators (EBWs) containing pentaerythritol tetranitrate (PETN) exposed to high temperatures may not function following discharge of the design electrical firing signal from a charged capacitor. Knowing functionality of these arbitrarily facing EBWs is crucial when making safety assessments of detonators in accidental fires. Orientation effects are only significant when the PETN is partially melted. The melting temperature can be measured with a differential scanning calorimeter. Nonmelting EBWs will be fully functional provided the detonator never exceeds 406 K (133 °C) for at least 1 h. Conversely, EBWs will not be functional once the average input pellet temperature exceeds 414 K (141 °C) for a least 1 min which is long enough to cause the PETN input pellet to completely melt. Functionality of the EBWs at temperatures between 406 and 414 K will depend on orientation and can be predicted using a stratification model for downward facing detonators but is more complex for arbitrary orientations. A conservative rule of thumb would be to assume that the EBWs are fully functional unless the PETN input pellet has completely melted. [ABSTRACT FROM AUTHOR]

In recent decades, glaciers in the Amundsen Sea Embayment in West Antarctica have made the largest contribution to mass loss from the entire Antarctic Ice Sheet. Glacier retreat and acceleration have led to concerns about the stability of the region and the effects of future climate change. Coastal thinning and near-synchronous increases in ice flux across neighbouring glaciers suggest that ocean-driven melting is one of the main drivers of mass imbalance. However, the response of individual glaciers to changes in ocean conditions varies according to their local geometry. One of the largest and fastest-flowing of these glaciers, Pine Island Glacier (PIG), underwent a retreat from a subglacial ridge in the 1940s following a period of unusually warm conditions. Despite subsequent cooler periods, the glacier failed to recover back to the ridge and continued retreating to its present-day position. Here, we use the ice-flow model Úa to investigate the sensitivity of this retreat to changes in basal melting. We show that a short period of increased basal melt was sufficient to force the glacier from its stable position on the ridge and undergo an irreversible retreat to the next topographic high. Once high melting begins upstream of the ridge, only near-zero melt rates can stop the retreat, indicating a possible hysteresis in the system. Our results suggest that unstable and irreversible responses to warm anomalies are possible and can lead to substantial changes in ice flux over relatively short periods of only a few decades. [ABSTRACT FROM AUTHOR]

The Kerguelen Plateau is the second biggest submarine large igneous province (LIP) on Earth, however, the nature of the lithospheric mantle source underlying it remains poorly constrained. In this contribution, we provide novel insights into the oceanic lithospheric mantle underlying Heard Island (southern Indian Ocean), which represents the most recent and active phase of volcanic activity (<1 Ma) in the Kerguelen Plateau. We present petrographic and geochemical data for a suite of spinel-bearing harzburgite xenoliths hosted in basanite lavas and provide detailed constraints for distinguishing in situ mantle metasomatism from post-entrapment modification of the xenoliths following interaction with the host magma. We demonstrate that the xenolith mineral compositions and textures preserve a complex multistage history of different modal and cryptic transformations that occurred in the mantle due to: i) high degrees of partial melting that produced highly refractory whole-rock Mg# (Mg# = (Mg + Fe)/Mg × 100; 88–92), major element (FeO/MgO = 0.17) and mineral compositions (e.g. highly forsteritic olivine; Fo = (Mg + Fe)/Mg × 100; 91–92 mol %); ii) solid-state re-equilibration reactions during decompression that caused exsolution of clinopyroxene and Cr-spinel from xenolith orthopyroxene to form symplectite intergrowths; iii) cryptic metasomatism affecting the composition of xenolith clinopyroxene (i.e. enrichment in Na, Th, U and light rare earth elements, and depletion in Rb, Nb, Zr, Hf and Ti) due to interaction with carbonatitic melts in the mantle. Mantle fragments, entrapped by ascending basanite magmas as xenoliths were further modified by reactions with the host magma. This resulted in the partial dissolution of mantle orthopyroxene and replacement by newly formed and compositionally distinct assemblages of clinopyroxene (Mg# 87–91), olivine (Fo: 81–88 mol %) and Cr-spinel (i.e. 'wehrlitisation' of the xenoliths). This study highlights the utility of combining petrography and mineral chemistry to decipher the complex and sometimes overprinting and masking effects that different processes (e.g. melting events, metasomatism) exert on the lithospheric mantle, as well as constrain the processes that modify the xenoliths during transport towards the surface. [ABSTRACT FROM AUTHOR]

The melting process of two-dimensional binary mixtures is studied using the Langevin simulation method. The melting point of each component in a binary mixture is determined by the local relative interparticle distance fluctuation method. The results show that, compared with the monodisperse system, the components of the binary mixture exhibit a multi-step melting characteristic. Further, the melting process of binary mixtures is found to depend on the mixing ratio and charge ratio. It is shown that particle hopping motion plays a key role in understanding melting in binary mixtures. [ABSTRACT FROM AUTHOR]

Accurate constitutive data, such as equations of state and plasma transport coefficients, are necessary for reliable hydrodynamic simulations of plasma systems such as fusion targets, planets, and stars. Here, we develop a framework for automatically generating transport-coefficient tables using a parameterized model that incorporates data from both high-fidelity sources (e.g., density functional theory calculations and reference experiments) and lower-fidelity sources (e.g., average-atom and analytic models). The framework incorporates uncertainties from these multi-fidelity sources, generating ensembles of optimally diverse tables that are suitable for uncertainty quantification of hydrodynamic simulations. We illustrate the utility of the framework with magnetohydrodynamic simulations of magnetically launched flyer plates, which are used to measure material properties in pulsed-power experiments. We explore how changes in the uncertainties assigned to the multi-fidelity data sources propagate to changes in simulation outputs and find that our simulations are most sensitive to uncertainties near the melting transition. The presented framework enables computationally efficient uncertainty quantification that readily incorporates new high-fidelity measurements or calculations and identifies plasma regimes where additional data will have high impact. [ABSTRACT FROM AUTHOR]

Phase change material (PCM)‐based heat storage systems utilize the absorption or release of latent heat during a phase change of the storage material to store thermal energy. Nevertheless, the effectiveness of these systems is restricted by the shape and structure of their confinement, as well as the heat conductivity of the storage material. This work investigates a novel method to enhance the effectiveness of PCM systems by concurrently utilizing two techniques: the inclusion of nanoparticles and the alteration of the system's geometry. Introducing nanoparticles enhances the thermal conductivity of the storage medium while altering the shape, which improves heat transfer efficiency by adjusting the surface area available for heat exchange. RT‐35 was tested for use in latent heat thermal energy storage systems for space heating and cooling. With a melting point of 35°C, RT‐35 was chosen to moderate building temperatures by storing and releasing thermal energy for space heating and cooling. The results indicate that using nanoparticles and adjusting shape can greatly enhance the effectiveness of PCM systems. By incorporating Al2O3 nanoparticles, the melting time of the PCM was reduced by 20% compared to the pure PCM, and it is more efficient than the best case of shape modification. These findings indicate that including nanoparticles and modifying the shape are effective methods to improve the performance of heat storage devices. This technology's potential surpasses this study's limits and can be utilized in diverse applications, including solar thermal energy storage, district heating and cooling, and industrial process heat. [ABSTRACT FROM AUTHOR]

This paper investigates how stationary gravity waves generated by flow over orography enhance rainfall, with particular attention to the role of induced waves in the melting level. The findings reveal a new mechanism by which gravity wave flow focuses precipitation, amplifying rainfall intensity downwind of hills. This mechanism, which depends on the differential velocities of rain and snow, offers fresh insights into how orographic effects can intensify rainfall. A two-dimensional diagnostic model based on linear gravity wave theory is used to investigate the record-breaking rainfall of December 2015 in the Lake District of northwest England. The pattern of ascent is shown to have a qualitatively good fit to that of the Met Office's operational high-resolution UKV model averaged over 24 h, suggesting that orographically excited stationary waves were the principal cause of the rain. Precipitation trajectories imply that a persistent downstream elevated wave caused by the Isle of Man supported a spray of seeding ice particles directed towards the Lake District, and that these grew whilst suspended in strong upslope flow before being focused by the undulating melting-level into intense shafts of rain. [ABSTRACT FROM AUTHOR]

Context: We explore the influence of strongly hydrophilic confinement on various properties of water, such as density, enthalpy, potential energy, radial distribution function, entropy, specific heat capacity, structural dynamics, and transition temperatures (freezing and melting temperatures), using monatomic water (mW) model. The properties of water are found to be dependent on confinement and the wall-fluid surface interaction. Hysteresis loops are observed for density, enthalpy, potential energy, and entropy around the transition temperatures, while the size of hysteresis loops varies with confinement and surface interaction. In smaller pore sizes (H ≤ 20), the solid phase displays a higher density compared to the liquid phase, which is unconventional behavior compared to bulk water systems due to the pronounced hydrophilic properties of the confinement surface. Specific heat capacity exhibits more oscillations in the confined system compared to bulk water, stemming from uneven enthalpy differences across equal temperature intervals. During phase transformation in both heating and quenching processes, there is an abrupt change observed in specific heat capacity. Confinement exerts a notable impact on entropy in the solid phase, but its influence is negligible in the liquid phase. At lower pore sizes (H < 25 Å), there is more fluctuation in freezing temperature for all wall-fluid interactions, which diminishes beyond pore sizes of H > 25 Å. Similarly, more oscillatory behavior is observed in melting temperatures at lower pore sizes (H < 40 Å), which diminishes at higher pore sizes (H > 40 Å). During the quenching process, a sudden jump in the in-plane orientational and tetrahedral order parameters indicates the formation of an ordered phase, specifically a diamond crystalline structure. The percentages of different crystalline structures (cubic diamond, hexagonal diamond, and 2D hexagonal) vary with both the confinement size and the wall-fluid interaction strength. Methods: Cooling and heating simulations are conducted with the mW water model using LAMMPS for different nanoscale confinement separation sizes ranging from 8.5 to 70 Å within the temperature range of 100–350 K. The water is modeled using two-body and three-body interaction potential (Stillinger–Weber potential) and the confinement is introduced using LJ 9–3 water-wall interaction potential. Entropy is calculated using RDF data obtained from the simulation experiments for each temperature point with increments or decrements of 2.5 K. The transition temperatures are estimated using the specific heat capacity analysis. [ABSTRACT FROM AUTHOR]

Microlayer coextrusion is capable of producing multilayer composites with anywhere from 30 to 1000 layers, each layer having a thickness of 20 − 5000 nm. Microlayer coextrusion assembles such layers into monolithic products by repeated splitting and stacking a small number of input melt streams. Owing to the superlattice multilayer configuration, microlayer composites usually show outstanding mechanical, barrier, and optical properties and thus have broad application prospects in the industry. Therefore, microlayer coextrusion has been attracting both academic and industrial interest. This review focuses on the progress of microlayer coextrusion and its derivative technologies, including (i) the development and optimization of microlayer coextrusion; (ii) excellent properties conferred by the microlayer structure; (iii) derivative technologies to build microlayer structures in more types polymer products like films, pipes, pellets, and fibers; (iv) viscoelastic behavior during microlayer coextrusion to achieve more fine layer structure; (v) future research endeavors and possible directions for further progress in this filed are outlined. [ABSTRACT FROM AUTHOR]

The femtosecond laser direct writing of metals has gained significant attention for micro/nanostructuring. Copper (I) oxide nanospheres (NSs), a promising material for multi-photon metallization, can be reduced to copper (Cu) and sintered through near-infrared femtosecond laser pulse irradiation. In this study, we investigated the size effect of copper (I) oxide nanospheres on their morphology when coated on Cu thin films and irradiated by near-infrared femtosecond laser pulses. Three Cu2O NS inks were prepared, consisting of small (φ100 nm), large (φ200 nm), and a mixture of φ100 nm and φ200 nm NSs. A unique phenomenon was observed at low laser pulse energy: both sizes of NSs bonded as single layers when the mixed NSs were used. At higher pulse energies, the small NSs melted readily compared to the large NSs. In comparisons between the large and mixed NSs, some large NSs remained intact, suggesting that the morphology of the NSs can be controlled by varying the concentration of different-sized NSs. Considering the simulation results indicating that the electromagnetic fields between large and small NSs are nearly identical, this differential morphology is likely attributed to the differences in the heat capacity of the NSs. [ABSTRACT FROM AUTHOR]

Oxide and dross formation during aluminum melt processing results in a considerable amount of loss of metallic aluminum. The total melt loss generated during melt processing can be greatly reduced by efficient use of flux, particularly for melting aluminum scrap or secondary alloys. Effective use of cover fluxes can significantly reduce dross generation by creating a barrier between the metallic aluminum and the atmosphere. The amount of metallic aluminum trapped within the dross layer can also be reduced by up to 50% using drossing fluxes. However, reducing the industrial average melt loss has remained difficult. To evaluate flux ingredients used in the casting industry, computational thermodynamic software ThermoCalc was used to calculate the driving force for reactions between twenty-one flux ingredients and eighteen common alloying and impurity elements in foundry alloys. The thermodynamic calculations, combined with other properties, were used to provide a desirable list of cover and drossing ingredients, which are being experimentally validated. [ABSTRACT FROM AUTHOR]

Magmatic iron meteorites are thought to sample the metallic cores of differentiated planetesimals and are subdivided into several chemical groups, each representing a distinct parent body. The only exceptions are the groups IIAB and IIG, which have been proposed to sample two immiscible melts from the same core. To test this model, we report the first Fe, Ni, O, and Cr isotope data for IIG iron meteorites and the first high-precision O isotope data for IIAB iron meteorites. The new data demonstrate that IIG iron meteorites belong to the non-carbonaceous (NC) meteorites. This is evident from the isotope anomaly of each of the four elements investigated, where the IIG irons always overlap with the compositions of NC meteorites but are distinct from those of carbonaceous (CC) meteorites. Moreover, among the NC meteorites and in particular, the NC irons, the isotopic composition of the IIG irons overlaps only with that of the IIAB irons. The combined Fe-Ni-O-Cr isotope data for IIAB and IIG iron meteorites, therefore, reveal formation from a single isotopic reservoir, indicating a strong genetic link between the two groups. The indistinguishable isotopic composition of the IIAB and IIG irons, combined with chemical evidence for the formation of IIG irons as late-stage liquids of the IIAB core, strongly suggests that both groups originate from the same core. The results underscore the strength of utilizing multiple elements and their isotopic compositions to establish genetic links among meteorites, rather than using a single element. They also highlight the significance of integrating multiple geochemical tracers and petrologic observations to accurately determine genetic relationships and the formation of meteorites within the same parent body. [ABSTRACT FROM AUTHOR]

Low thermal diffusivity of NiTi-based smart alloy results in concentrated heat accumulation during laser beam machining which rises to adverse thermal effects like heat-affected zones, residual stresses, and alterations in microstructure of shape memory alloy (SMA) system. The addition of Cu and Zr can reduce the thermal hysteresis in the phase transformation of NiTi SMAs. Minimizing thermal hysteresis is desirable in SMA applications where precise control of the phase transformation temperatures is required, such as in actuators, sensors, and medical devices. Therefore, aqua jet integrated laser (AJ-FLBM) machining is a suitable choice for smart materials that need to be machined with high precision and low heat affected zone. In this current research, the NiTiCuZr SMA is machined using AJ-FLBM to investigate the effects of process variables on surface characteristics measured using RSM-BBD approach. The surface quality was enhanced by 68.93% with a gradual decrease in laser power (P), cutting speed (CS), and an increase in frequency (F). Aqua jet integrated FLBM technique may reduce heat affected zone due to the removal of heat in areas near the cutting location. This was confirmed by the DSC test which reveals that optimal machining inputs do not alter shape memory properties. [ABSTRACT FROM AUTHOR]

Wood–plastic composites (WPCs) utilize wood particles as the reinforcing phase. These particles are susceptible to thermal degradation, which can happen while processing the WPCs in usual thermoplastic processes. In this work, we investigated the influence of different processing parameters in injection molding and their influence on WPC properties. To achieve that, WPCs with wood contents ranging from 10 to 50 wt% were processed using different process settings, and then characterized using mechanical testing and appearance changes. We found that the melt temperature showed a major influence, due to degrading the interface between the wood and the polymer matrix, while other parameters, like mold temperature and dwell pressure, showed only minor influence. Overall, the WPCs exhibited good process stability and, with proper process settings, their performance can be improved. [ABSTRACT FROM AUTHOR]

This research investigates the effect of silicon (Si) addition on the phase transformation behaviour of the Ni–Ti alloy. The Ni–Ti–Si alloys were fabricated with varying proportions of Si through a modified vacuum induction melting technique with argon backfilling. Scanning electron microscopy, X-ray diffraction and differential scanning calorimetry were done to analyse the microstructure, elemental composition, and phase transformation temperatures, respectively, to validate the effectiveness of this modified melting technique. The results indicate an increase in the phase transformation temperature with an increase in the Si content in the alloy mixture and the alloys were prepared with a very minimal amount of detrimental impurities. This technique helps to produce high-temperature shape memory alloys with utmost purity which helps in retaining their functional properties. The transformation temperatures observed from differential scanning calorimetry revealed that the Af temperature varies from 342.68 K to 379.95 K for 3 to 12% variation in Si content. This group of shape memory alloys have potential use as actuators in aircrafts and various other applications. [ABSTRACT FROM AUTHOR]

The development of Al-Ni alloys with a controlled microstructure has had a great impact on the field of study of aluminum-based alloys. In the present research, the influence of thermal parameters on the grain structures resulting from the directional solidification process of Al-Ni alloys with different alloy content has been studied. It has also been evaluated how different structures and the distribution of second phases influence the corrosion behavior and microhardness of alloys. The columnar-to-equiaxed transition (CET) was observed to occur when the temperature gradient in the melt decreased to values between 1.3 and 2.9 °C/cm. In addition, a small increase in the microhardness values was observed as a function of the Ni content. When the Ni content increases, the resistance to polarization decreases for samples with equiaxed grain structure throughout the range of compositions studied. Furthermore, the equiaxed grain structure presents higher resistance to polarization values than the columnar grain zone for alloys with a composition equal to or lower than the eutectic composition. [ABSTRACT FROM AUTHOR]

Sweet buttermilk, a by-product of butter production, remains highly underutilized despite containing some relevant components (i.e., phospholipids) that may have a high biological value and may exert some positive technological functions. The aim of this study was to investigate the possibility of using ultrafiltered (UF) sweet buttermilk at different volume reduction ratios (3 and 5) to replace emulsifiers and/or stabilizers in the production of a novel clean-label ice cream formulation made with sweet buttermilk-based mixtures. The functional, thermo-rheological, and sensory profile of four types of ice creams was investigated. Increasing the degree of sweet buttermilk concentration positively influenced the overrun values and at the same time improved the ice cream's resistance to melting. Also, the thermo-rheological profile during melting was influenced by the presence of UF buttermilk. These differences in techno-functional properties were probably partly caused by the different total phospholipids content caused by UF buttermilk. Some sensory properties (i.e., structure, consistency) were positively related to the utilization of UF buttermilk, while aroma and taste were negatively influenced. This study demonstrated that UF buttermilk can be used as an additive replacer in ice cream production because it enhances the structural and rheological properties of the final product. [ABSTRACT FROM AUTHOR]

Asymmetric kinetic resolution polymerization (AKRP) provides an ideal way to obtain highly isotactic polylactide (PLA) with superior thermal‐mechanical properties from racemic lactide (rac‐LA). However, the development of a new catalytic system with concurrent high activity and selectivity at ambient temperature remains a great callenge. Here, a series of simple and effective binary organocatalytic pairs containing axial‐chiral thioureas and commercially available phosphazene bases were designed. These chiral binary organocatalytic pairs allow for both high polymerization activity and moderate enantioselectivity for AKRP of rac‐LA at room temperature, yielding semi‐crystalline and metal‐free stereoblock PLA with a melting temperature as high as 186 °C. The highest kinetic resolution coefficient (krel) of 8.5 at 47 % conversion was obtained, and D‐LA was preferentially polymerized via kinetic resolution with a maximum selectivity factor (kD/kL) of 18.1, indicating that an enantiomorphic site control mechanism (ESC) was involved. [ABSTRACT FROM AUTHOR]

We investigated the melting behavior of four CPs with one-dimensional structures from a thermodynamic point-of-view. The difference in melting points depending on the crystal structures is observed. The interactions within the crystals were analyzed using DFT calculations. These analyses suggest that entropic terms dominate the melting points. [ABSTRACT FROM AUTHOR]

The stability of the injection molding process is critical to efficient production. However, environment and production disturbances pose challenges to maintaining a stable molding process. A two-stage dynamic adjustment strategy is proposed in this paper to increase weight consistency, considering fluctuation of density and fluidity based on products' types and structure. This study investigates the factors influencing the weight stability of injection molding products during the injection and holding stages. Experiments show that the injection stage is affected by density fluctuations, while melt fluidity fluctuations influence the holding stage. Simulation experiments prove the efficacy of dynamic adjustment strategies for injection-sensitive products (ISP) and holding-sensitive products (HSP). Thinner products as ISPs benefit from adjustments of the injection stage parameters, while thicker products as HSPs require optimization of holding stage parameters. To prove its validity, this strategy was tested on two molds and improved weight stability by 60.0% and 34.8%, respectively. [ABSTRACT FROM AUTHOR]

The integration of LPBF printing technologies in various innovative applications relies on the resilience and reliability of parts and their quality. Reducing or eliminating the factors leading to defects in final parts is crucial to producing satisfactory high-quality parts. Extensive efforts have been made to understand the material properties and printing process parameters of LPBF-printed geometries that trigger defects. Studies of interest include the use of various sensing technologies, numerical modeling, and artificial intelligence (AI) to enable a better understanding of the phenomena under investigation. The primary objectives of this article are to introduce the reader to the most widely read published data on (1) the roles of numerical and analytical models in LPBF defect detection; (2) AI algorithms and models applicable to predict LPBF metal defects and causes; and (3) the integration of modeling, AI, and sensing technology, which is commonly used in material characterization and has been proven efficient and applicable to LPBF metal part defect detection over extended periods. [ABSTRACT FROM AUTHOR]

Citric acid is widely used in the Food and Pharmaceutical Industry. Various issues regarding its thermal behavior and infrared spectrum require clarification. Here, we studied citric acid monohydrate (raw, heated, freeze-dried and recrystallized from D2O) via Differential Scanning Calorimetry, Thermogravimetric Analysis, Infrared Spectroscopy, and antioxidant capacity assay. Also, we used ab initio Density Functional Theory calculations for further supporting the interpretations of the experimental results. Citric acid monohydrate exhibits desolvation inability and upon heating does not dehydrate but esterifies. Nor by freeze drying can it be dehydrated. The heated sample is not anhydrous, it exhibits melting inability, and any fluidization occurs simultaneously with decomposition. In other words, the interpretations regarding the two endothermic peaks in the DSC curve of citric acid that have been attributed to water evaporation and melting are not correct. The increase in the molecular weight due to esterification is most likely responsible for the increased antioxidant/chelation capacity of the heated sample. We concluded that what we call citric acid monohydrate and anhydrous do not exist in a pure form (in the solid state) and actually are mixtures of different compositions of citric acid, water and a citric acid oligomer that is produced through esterification. The esterification reaction seems to be able to proceed easily under mild heating or even at room temperature. The presence of the ester oligomer and water affect the infrared spectrum of citric acid monohydrate and anhydrous and is responsible for the existence of multiple peaks in the C=O stretching region, which partially overlaps with the water H-O-H bending vibration. The insights presented in this work could be useful for optimizing the design, performance and quality of food and drug products in which citric acid is used. [ABSTRACT FROM AUTHOR]

Staphylococcus (S.) aureus is a pathogenic bacterium able to cause several diseases in humans and animals as well as foodborne intoxications. S. argenteus, being phenotypically and genotypically related to S. aureus, is part of the so-called S. aureus complex and recently recognized as an emerging pathogen able to cause, like S. aureus, several diseases both in humans and animals, and foodborne poisoning outbreaks. However, it has been reported that the widely used conventional PCR of Brakstad et al. [Journal of Clinical Microbiology, 30(7), 1654–1660, (1992)] targeting the thermostable nuclease gene may provide false-positive S. aureus, as it is able to amplify also S. argenteus. Here, we developed a novel two-step approach that, following the PCR of Brakstad et al. (1992), discriminates S. aureus from S. argenteus by a real-time PCR with high-resolution melting analysis (rt-PCR-HRM). In particular, targeting a polymorphic 137 bp region of the sodA gene, our developed rt-PCR-HRM method clearly discriminated S. aureus from S. argenteus, showing a remarkable difference in their amplification product melting temperatures (approximately 1.3 °C) as well as distinct melting curve shapes. The good sensitivity, reproducibility, user friendliness, and cost effectiveness of the developed method are advantageous attributes that will allow not only its easy employment to correctly identify misidentified isolates present in various collections of S. aureus, but also expand the still lacking knowledge on the prevalence and distribution of S. argenteus. [ABSTRACT FROM AUTHOR]