Supersaturated State Research Articles

Effects of different physicochemical characteristics and supersaturation principle of solidified SNEDDS and surface-modified microspheres on the bioavailability of carvedilol

In this study, a solidified self-nanoemulsifying drug delivery system (solidified SNEDDS) and surface-modified microspheres were developed for enhancing the oral bioavailability of carvedilol. Based on the aqueous solubility test, liquid SNEDDS was composed of Peceol™ (oil), Tween® 80 (surfactant), and Labrasol® (co-surfactant) at a weight ratio of 25/50/25, generating the smallest nanoemulsion droplet size. Then, carvedilol was added to liquid SNEDDS and spray-dried with Aerosil® to fabricate the solidified SNEDDS. Surface-modified microspheres were manufactured using copovidone (polymer) and Tween® 80 (surfactant) according to aqueous solubility test results. The proper ratio of copovidone and Tween® 80 was determined based on the solubility and dissolution test. Both prepared formulations and carvedilol powder were compared using four different criteria: physicochemical characteristics, solubility, dissolution, and oral bioavailability. For solidified SNEDDS, carvedilol was encapsulated in liquid SNEDDS and absorbed to the Aerosil® surface, leading to the conversion from a crystalline to an amorphous state. However, the drug maintained its crystal form in the surface-modified microspheres. Round and even-sized particles were attached to the rough surfaces of drug, suggesting that hydrophilic carriers adhered to the hydrophobic drug. All formulations significantly improved drug solubility, dissolution, plasma concentrations, Cmax, and AUC compared to carvedilol powder. The parameters were ranked in the following order: solidified SNEDDS > surface-modified microspheres > carvedilol powder. As a result, different solubility-increasing mechanisms provided differences in performance. For carvedilol, the formation of a nano-emulsion in solidified SNEDDS resulted in an efficient supersaturated state, leading to improved solubility (~6.1 fold), dissolution (~1.8 fold), and oral bioavailability (~1.4 fold) that was superior to the hydrophilic microenvironment in surface-modified microspheres.

Groundwater quality and hydrological stress induced by Lower Gondwana open cast coal mine

Open cast coal mine (OCCM) may impose adverse effects on groundwater quality and on its flow regime. Evaluation of water quality often becomes difficult and confusing due to presence of multiple criteria and index based on different parameters. A novel approach has been introduced which speaks about a single index revealing the effect of all important parameters to determine the quality for a particular use of groundwater. Physico-chemical parameters of groundwater are grouped according to their toxicity and the weightage is permitted to each group using analytic hierarchy process (AHP). Overall groundwater quality is found suitable for drinking (DWQI = 1.5–2) and irrigation (IWQI = 2 to 3) purposes in Barjora area. Effect of acid mine drainage (AMD) is not significant in controlling the quality of groundwater in the study area. Carbonate and silicate weathering are the dominant hydro-geochemical processes occurring in the study area. Saturation index derived through Phreeqc Interactive software shows that calcite and aragonite are at supersaturated condition in close proximities of OCCMs. Buffer reactions of carbonate minerals may attenuate the effect of AMD in the study area. The hydrological stress induced by OCCM has been evaluated in OCCM 2 through numerical modelling using MODFLOW software. Evaluation has been performed in three stages of mine development – pre-mining condition, present mining condition and future extension of mine. It is estimated that groundwater of almost 24,163 m3/d will ingress into the excavation of 2.03 km2 area with maximum depth around 200 m from ground level. Model predicted 4–5 m lowering of water table, as an impact, around 2.86 km2 area of the mine cavity. The irrigation canal passing through this region, will lose 1473 m3/d water during future extension of mine.

Randall's plaque and calcium oxalate stone formation: role for immunity and inflammation.

Idiopathic calcium oxalate (CaOx) stones often develop attached to Randall's plaque present on kidney papillary surfaces. Similar to the plaques formed during vascular calcification, Randall's plaques consist of calcium phosphate crystals mixed with an organic matrix that is rich in proteins, such as inter-α-trypsin inhibitor, as well as lipids, and includes membrane-bound vesicles or exosomes, collagen fibres and other components of the extracellular matrix. Kidney tissue surrounding Randall's plaques is associated with the presence of classically activated, pro-inflammatory macrophages (also termed M1) and downregulation of alternatively activated, anti-inflammatory macrophages (also termed M2). In animal models, crystal deposition in the kidneys has been associated with the production of reactive oxygen species, inflammasome activation and increased expression of molecules implicated in the inflammatory cascade, including osteopontin, matrix Gla protein and fetuin A (also known as α2-HS-glycoprotein). Many of these molecules, including osteopontin and matrix Gla protein, are well known inhibitors of vascular calcification. We propose that conditions of urine supersaturation promote kidney damage by inducing the production of reactive oxygen species and oxidative stress, and that the ensuing inflammatory immune response promotes Randall's plaque initiation and calcium stone formation.

A new CCN activation parameterization and its potential influences on aerosol indirect effects

Unactivated particles mixed in cloud condensation nuclei (CCN) measurements lead to inaccurate activation parameterization, thereby overestimating aerosol indirect effects in current models. Data from five CCN field campaigns in Eastern China are analyzed to identify unactivated particles. The lower temperature, lower aerosol hygroscopicity (κ), and the aerosol particle size distribution closer to that in the coast (compared to that in the continent) lead to a higher proportion of unactivated particles in CCN measurements; the underlying physical mechanisms are discussed. A correction for the CCN activation parameterization is essential for regions with the above characteristics. After removing the unactivated particles, it is found that the widely used Twomey power-law activation parameterization does not adequately fit the relationship between the corrected CCN concentration and the supersaturation; therefore, a new, better-fitting, two-parameter activation parameterization is proposed. A method is presented for estimating the parameters in the new parameterization according to the κ-Köhler theory, that is, the two parameters can be estimated as 59% and 66% of aerosol number concentration for continental regions (represented by Nanjing, 32.21°N, 118.70°E) and 69% and 79% of that for coastal regions (represented by Shenzhen, 22.48°N, 114.56°E), respectively. The new CCN activation parameterization significantly reduces the overestimation of CCN concentration at low supersaturation (SS) conditions, e.g., at SS = 0.1% in the five CCN campaigns, the overestimation is 77% to 102% for the classical power-law parameterization and only 6% to 13% for the new parameterization. As a result, the new parameterization may reduce the overestimation of aerosol indirect effects in models, especially at low supersaturation conditions.

Atmospheric ice nucleating particle measurements and parameterization representative for Indian region

Atmospheric ice nucleating particle (INP) concentration measurements over the Indian region are very sparse; hence more observations are required to represent heterogeneous ice nucleation processes in the regional cloud models for better accuracy. In this work, the INP ability and size of ambient aerosol particles at a tropical high altitude station were studied. Ice nucleation experiments were conducted at temperatures between −25 and −34 °C and water supersaturation conditions up to 102%. The mean INP concentrations varied from 1.1 to 9.5 L−1 and correlated well with coarse mode aerosol particle concentration (> 1 μm). Higher INP concentrations were observed when the aerosol loading was influenced by the regions such as Mumbai metro city, Gujarat, Thar desert region, and the Arabian sea region close to the Oman coast. An empirical equation was formulated to represent the INP concentrations using supercooled temperature and coarse mode aerosol particle concentration. The sensitivity of new heterogeneous ice nucleation parameterization was tested against literature INP parameterizations using Weather Research and Forecasting (WRF) model. The model results show that the new parameterization helped to simulate the rainfall amount better as compared to the old formulations. Better reproduction of convection and possible reduction of biases in the formation of cloud ice in the cloud-resolving model improved the model accuracy. These results show the importance of implementing new INP parameterization in a real-time forecast model to improve the regional climate model forecasting.

Temperature- and Solvent-Induced Crystal-Form Transformations of the Pyridine@p-tert-butylcalix[6]arene Host–Guest System

Crystallization conditions for producing crystal structures of p-tert-butylcalix[6]arene (TBC6) with different conformations were screened. Molecular recognition and self-assembly between the TBC6 host and the guest pyridine led to kinetic trapping and crystallization of intermediate exclusion complexes. These complexes were characterized by single-crystal X-ray diffraction, which revealed that the first-formed crystals are 11:2 polymorphic association complexes with winged-cone host conformations. The crystalline kinetic complex undergoes slow spontaneous dissolution and subsequently recrystallizes as thermodynamic inclusion complexes, namely a 1:3 pseudopolymorphic and three 1:1 polymorphic pyridine@TBC6 complexes. The crystal structure of the host–guest system can be tuned by changing the temperature and supersaturation conditions. Interaction energies were used to generate intermolecular interaction topologies during energy framework analysis, which were used to study the hierarchies of various interactional motifs and their topologies in this series of TBC6 complexes.

Simultaneously enhanced hardness and electrical conductivity in a Cu–Ni–Si alloy by addition of Cobalt

The effects of Co on the physical properties and precipitation evolution of a Cu–Ni–Si alloy are investigated via hardness and electrical conductivity testing, transmission electron microscopy and a quantitative three-dimensional atom probe. The precipitation sequence of Cu–Ni–Si alloy aging at 500 °C can be expressed as supersaturated solid solution → solute clusters → GP zones → Ni2Si phases. In the early aging stage, the formation of atomic clusters is accompanied by the occurrence of spinodal decomposition. The addition of Co accelerates the redistribution and agglomeration of solute atoms, resulting in the nucleation of (Ni, Co)2Si phases directly from the supersaturated state, which further hinders atomic cluster formation and spinodal decomposition. The Ni2Si and (Ni, Co)2Si phases, which are divided into a region II containing pure Ni2Si and the (Ni, Co)2Si phase and an unstable region I containing a small amount of Cu atoms, show the same crystal structure and orientation relationship with the matrix. During the aging process, the range of region I is gradually replaced by the core stable region II and accompanied by the growth of the total thickness of the precipitated phase. This remarkable age effect with Co addition can be attributed to the enhanced number of (Ni, Co)2Si precipitates, which simultaneously increases the strength and electrical conductivity.

Strong spring winds accelerated the recruitment and reinvasion of cyanobacteria.

The reinvasion and recruitment of overwintering cyanobacteria in sediments in spring have an important impact on cyanobacterial blooms in summer and autumn, but until now, this process has not been observed in natural water bodies. In this study, wireless sensors and automatic water sample collection systems were used to carry out continuous high-frequency monitoring of cyanobacteria and related environmental indicators in Meiliang Bay, Lake Taihu, during a northwest wind event in spring. The results showed that there were many dormant cyanobacteria seeds in the sediments of Lake Taihu. These cyanobacterial seeds were easily resuspended from sediments, allowing them to reinvade and remain in the overlying water. Simultaneously, the water temperature exceeded the recovery temperature after the northwest wind event and the available light was sufficient to allow the reinvading cyanobacteria to recruit. The circadian photosynthetic rhythm of these recruited cyanobacteria eventually led to a rapid increase in dissolved oxygen in the water body during the south wind phase to a supersaturated state, and periodic diurnal fluctuations of the water body dissolved oxygen saturation curve. This study provided direct evidence for fully understanding the annual cycle of cyanobacterial blooms.

Probing Homotopy Continuation Method for Solving Nonlinear Magnetic Network Equations

Nonlinear magnetic network is an effective model to solve the magnetic field of the motor. For the strong nonlinearity of magnetic network parameters, it is difficult to solve the nonlinear magnetic network equations. To overcome the divergent issue for solving the nonlinear magnetic network equations, a new method, the homotopy continuation method, is proposed. Based on the benchmark model of Testing Electromagnetic Analysis Methods Problem 20 (TEAM P20), the two-dimensional nonlinear magnetic network model is established. Next, homotopy equations of nonlinear magnetic network equations are derived, and they are solved by the homotopy continuation method. So that solving the nonlinear magnetic network equations is transformed into solving a set of homotopy equations. Then, the magnetic flux density of iron core with different saturation levels is calculated using the simple iteration method, the relaxation iteration method, Newton-Raphson method, and the homotopy continuation method, respectively. The results and convergence performance of the four methods are compared. It is proved that the proposed method can effectively expand the convergence domain and simplify the calculation process. The magnetic flux density calculated by the homotopy continuation method is compared with the finite element method in the supersaturated state, and the results are in good agreement. The relative error of the magnetic flux density of the core is less than 5%, which verifies the correctness of the proposed algorithm.

Aging and FGF23-klotho system.

During the evolution of skeletons, vertebrates acquired the bone made of calcium phosphate. By keeping the extracellular fluid in a supersaturated condition regarding calcium and phosphate, vertebrates create the bone when and where they want simply by providing a cue for precipitation. To secure this strategy, a new endocrine system has evolved that strictly controls the extracellular phosphate concentration. In response to phosphate intake, fibroblast growth factor-23 (FGF23) is secreted from the bone and acts on the kidney through binding to its receptor Klotho to increase urinary phosphate excretion and maintain phosphate homeostasis. The FGF23-Klotho endocrine system, when disrupted, results in hyperphosphatemia and ectopic precipitation of calcium phosphate in mice and humans. In addition to disturbed phosphate homeostasis, mice lacking Klotho suffer from premature aging. They exhibit multiple organ atrophy, arteriosclerosis characterized by vascular calcification, cardiac hypertrophy, sarcopenia, cognition impairment, frailty, and a shortened life span associated with chronic non-infectious inflammation. Restoration of the phosphate balance by placing Klotho- or FGF23-deficient mice on low phosphate diet rescued them from the aging-like phenotypes, indicating that phosphate was responsible for the accelerated aging. The similar pathophysiology is universally observed in patients with chronic kidney disease (CKD), rendering advanced CKD a clinical model of accelerated aging. CKD patients bear colloidal nanoparticles containing calcium phosphate in the blood, which are termed calciprotein particles (CPPs). CPPs have the ability to induce cell damage and inflammation, potentially contributing to accelerated aging. Terrestrial vertebrates with the bone made of calcium phosphate may be destined to age due to ectopic calcium phosphate.

Direct Observation of Initial Stages of Precipitation Hardening Process in Commercial Al 6061 Alloy

Evolution of precipitates in aluminum 6061 alloy, quenched after 2 h hold at 550oC (super-saturated solid solution state – SSSS) and aged at 145oC (for up to 960 min), was studied by routine, ex-situ, transmission electron microscopy (TEM). In parallel, initial stages of the precipitation hardening process (after few-minute ageing) were studied by in-situ TEM. It was An appearance of short-living (~8 min) loose, disordered, spherical ~6 nm in diameter precipitates was captured. These precipitates rearranged after relatively long interval of time (~100 min, corresponding to 240 min ageing in the ex-situ tests) into long-range ordered rod-like Guinier–Preston (GP) zones (presuming GPI). The dimensions of the latter, 20 nm×2.1 nm, was determined based on the ex-situ TEM images.-Longer, 960 min, ageing results in GPI → GPII transformation accompanied by an increase of dimensions and strength of the rod-like precipitates. Determined geometrical parameters are in a reasonable agreement with corresponding parameters assessed previously using shock-wave technique. This fact implies that shock-wave technique can be considered as a useful tool for studying dislocation/defect interactions in a wide variety of strengthened alloys.

The origin of trapiche-like inclusion patterns in quartz from Inner Mongolia, China

Abstract Fibrous amphibole and clay mineral inclusions that form striking trapiche-like star patterns within quartz crystals from Inner Mongolia, China, present a challenge to uncover how these crystals grow and incorporate inclusions in a geological context. We propose that the patterns formed as a result of protogenic clay (ferrosaponite or nontronite) inclusions that were preferentially trapped on rough surfaces during quartz crystal growth. The rough surface texture of these crystals is the result of multiple growth centers during 2D nucleation and spread and split crystal formation. Observations via optical microscopy, cathodoluminescence, and three-dimensional micro-CT scanning highlight how the exterior surface textures on the termination of a complete quartz crystal mimic its interior inclusion patterns. Cathodoluminescence images, as well as varying aluminum concentrations along a core-to-exterior transect in a quartz crystal slice, suggest that the formation fluid underwent a heterogeneous chemical history. Measurements of Ti and observations of fluid inclusions suggest the quartz formed at a temperature of under 348 °C. This study presents the details surrounding split crystal growth in quartz in a natural geological setting, which has implications for inspiring new materials and may serve as an indicator for turbid and highly supersaturated formation fluid conditions in geological formations.

Reconciling Nano- and Micro-Scale VLS Growth by Including Multi-Scale Supersaturation: A Growth Model Applied to Lateral Ge Films on Si

Extensive work on metal-catalyst-assisted vapor-liquid-solid (VLS) growth has been focused on nanometer-scale wires (nanowires) and there have been several studies modelling the effect of diameter, growth time, surface diffusion, etc. on these nanowires. In this context of nanowires, since the catalyst is so small, one could and researchers have ignored the effect of the requirement to supersaturate the catalyst. In this work, an analytical growth model is presented to explain the effect of supersaturation on the size of micrometer-scale catalysts and resulting films grown via the VLS mechanism by chemical vapor deposition by introducing the idea of “multi-scale” supersaturation (supersaturation as a function of catalyst size). The proposed model is derived from a materials balance relation which reduces to the nanowire equation (without the need for considering catalyst supersaturation) for sufficiently small radii. By including the supersaturation term, the model predicts the existence of the maximum size range of film at certain growth conditions which is not present in the pre-existing models. The model could also explain the “induction time” required for the catalyst to reach a supersaturation state to begin VLS growth. More importantly, it agrees with the available experimental data of VLS lateral heteroepitaxy of micrometer-scale Ge films on Si substrate which suggests that 0.0379 mol/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> of Ge atoms are required to supersaturate the Au catalyst at the growth conditions studied (375 °C). This new perspective on the multi-scale supersaturation effect unravels the role of the supersaturation term that had been hidden for more than half a century.

A comprehensive study of the basic formulation of supersaturated self-nanoemulsifying drug delivery systems (SNEDDS) of albendazolum

Albendazolum (ABZ) is a BCS class II drug. It has challenging biopharmaceutical properties, which include poor solubility and dissolution rate. These properties have laid the ground for developing a supersaturated self-nanoemulsifying drug delivery system (S-SNEDDS) to form oil-in-water nanoemulsion in situ to improve the oral bioavailability of ABZ. Based on the ABZ solubility, emulsifying ability, and stability after dispersion in an aqueous phase, an optimal self-nanoemulsifying drug delivery system (SNEDDS) consisting of oleic acid, Tween® 20, and PEG 600 (X:Y:Z, w/w) was identified, having 10% (w/w) hydroxypropyl methylcellulose (HPMC) E15 lv as its precipitation inhibitor. The optimized system possessed a small mean globule size value (89.2 nm), good dispersion properties (polydispersity index (PDI): 0.278), and preserved the supersaturated state of ABZ. S-SNEDDS was transformed into solid supersaturated self-nanoemulsifying drug delivery systems (SS-SNEDDS) using microcrystalline cellulose as a solid material. The developed S-SNEDDS were characterized for globule size, pH, turbidity, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and flow properties. The data obtained from the results suggest that this S-SNEDDS formulation can enhance the solubility and oral bioavailability of ABZ for appropriate clinical application.

Hydration breaking and chemical ordering in a levitated NaCl solution droplet beyond the metastable zone width limit: evidence for the early stage of two-step nucleation.

For over two decades, NaCl nucleation from a supersaturated aqueous solution has been predicted to occur via a two-step nucleation (TSN) mechanism, i.e., two sequential events, the formation of locally dense liquid regions followed by structural ordering. However, the formation of dense liquid regions in the very early stage of TSN has never been experimentally observed. By using a state-of-the-art technique, a combination of electrostatic levitation (ESL) and in situ synchrotron X-ray and Raman scatterings, we find experimental evidence that indicates the formation of dense liquid regions in NaCl bulk solution at an unprecedentedly high level of supersaturation (S = 2.31). As supersaturation increases, evolution of ion clusters leads to chemical ordering, but no topological ordering, which is a precursor for forming the dense disordered regions of ion clusters at the early stage of TSN. Moreover, as the ion clusters proceed to evolve under highly supersaturated conditions, we observe the breakage of the water hydration structure indicating the stability limit of the dense liquid regions, and thus leading to nucleation. The evolution of solute clusters and breakage of hydration in highly supersaturated NaCl bulk solution will provide new insights into the detailed mechanism of TSN for many other aqueous solutions.

Crystal growth inhibition of gypsum under normal conditions and high supersaturations by a copolymer of phosphino-polycarboxylic acid

Scale formation is a bottleneck of most industrial and domestic water equipment, in particular, of oilfield water systems. Therefore, high-performance and environmentally-benign chemical scale inhibitors are highly needed. Phosphino-polycarboxylic acid (PPCA) is a low-in-phosphorous scale inhibitor with high inhibition efficiency, but its synthesis and performance analyses have been rarely disclosed. In this work for the first time, a PPCA copolymer is synthesized by a simple method based on free radical polymerization of acrylic acid and phosphinic acid monomers and directly employed for gypsum scale inhibition. The formation of PPCA was verified by FTIR and 31PNMR spectroscopies, and then its inhibition performance was evaluated by the complexometric determination of the Ca2+ concentration. The PPCA (2.5 ppm) showed 100% inhibition efficiency at a saturation index of 0.31 at the room temperature and without pH regulation after 24 h with practically no detectable gypsum crystallites even after two months, while the commercial ATMP showed a low inhibition efficiency of 30%. The Field Emission Scanning Microscopy (FESEM) images of the PPCA-inhibited and uninhibited samples revealed that the typical gypsum microfibers are distorted and reduced in size significantly in the inhibited sample. At a still higher saturation index of 1.47 (saturation ratio of 10), the inhibition efficiency of PPCA reduced to 16% and 24% for two dosages of 2.5 and 10 ppm which was attributed to the higher ion activity coefficients at the extremely high ionic strength, and hence, a much higher thermodynamic driving force. The rate constants for these two high supersaturation conditions and low PPCA dosages were also calculated and discussed.

Potentially harmful metals, and health risk evaluation in groundwater of Mardan, Pakistan: Application of geostatistical approach and geographic information system

This study investigates the values of pH, total dissolved solids (TDS), elevation, oxidative reduction potential (ORP), temperature, and depth, while the concentrations of Br, and potentially harmful metals (PHMs) such as Cr, Ni, Cd, Mn, Cu, Pb, Co, Zn, and Fe in the groundwater samples. Moreover, geographic information system (GIS), XLSTAT, and IBM SPSS Statistics 20 software were used for spatial distribution modeling, principal component analysis (PCA), cluster analysis (CA), and Quantile-Quantile (Q-Q) plotting to determine groundwater pollution sources, similarity index, and normal distribution reference line for the selected parameters. The mean values of pH, TDS, elevation, ORP, temperature, depth, and Br were 7.2, 322 mg/L, 364 m, 188 mV, 29.6 °C, 70 m, 0.20 mg/L, and PHMs like Cr, Ni, Cd, Mn, Cu, Pb, Co, Zn, and Fe were 0.38, 0.26, 0.08, 0.27, 0.36, 0.22, 0.04, 0.43 and 0.86 mg/L, respectively. PHMs including Cr (89%), Cd (43%), Mn (23%), Pb (79%), Co (20%), and Fe (91%) exceeded the guideline values set by the world health organization (WHO). The significant R2 values of PCA for selected parameters were also determined (0.62, 0.67, 0.78, 0.73, 0.60, 0.87, −0.50, 0.69, 0.70, 0.74, −0.50, 0.70, 0.67, 0.79, 0.59, and −0.55, respectively). PCA revealed three geochemical processes such as geogenic, anthropogenic, and reducing conditions. The mineral phases of Cd(OH)2, Fe(OH)3, FeOOH, Mn3O4, Fe2O3, MnOOH, Pb(OH)2, Mn(OH)2, MnO2, and Zn(OH)2 (−3.7, 3.75, 9.7, −5.8, 8.9, −3.6, 2.2, −4.6, −7.7, −0.9, and 0.003, respectively) showed super-saturation and under-saturation conditions. Health risk assessment (HRA) values for PHMs were also calculated and the values of hazard quotient (HQ), and hazard indices (HI) for the entire study area were increased in the following order: Cd>Ni>Cu>Pb>Mn>Zn>Cr. Relatively higher HQ and HI values of Ni, Cd, Pb, and Cu were greater than one showing unsuitability of groundwater for domestic, agriculture, and drinking purposes. The long-term ingestion of groundwater could also cause severe health concerns such as kidney, brain dysfunction, liver, stomach problems, and even cancer.

The Effect of Direct Electric Current on the Plastic Behavior of AA7075 Aluminum Alloy in Different States of Hardening.

Electrically-Assisted Forming (EAF) techniques are interesting and promising for the automotive industry. Electrically-assisted tensile tests were carried out on specimens of AA7075 aluminum alloy in different states of hardening, namely T6 (the as-received state) and the supersaturated solid solution state. All the tests were carried out in quasi-static conditions under the application of direct electric current (DC) in the range of 90 to 540 A. The experimental results showed that with a DC density of 10 A/mm2 the uniform strain and strain at fracture increased when the AA7075 was in the supersaturated solid solution state. A correlation between the mechanical results and microstructural features analysed through transmission electron microscopy was assessed. An explanation of the investigated phenomena based on the electron wind theory, heterogeneous microscale Joule heating and the Portevin–Le Chatelier (PLC) effect was finally proposed.

Suppressing Condensation Frosting Using an Out-of-Plane Dry Zone.

The vapor pressure above ice is lower than that above supercooled water at the same temperature. This inherent hygroscopic quality of ice has recently been exploited to suppress frost growth by patterning microscopic ice stripes along a surface. These vapor-attracting ice stripes prevented condensation frosting from occurring in the intermediate regions; however, the required presence of the sacrificial ice stripes made it impossible to achieve the ideal case of a completely dry surface. Here, we decouple the sacrificial ice from the antifrosting surface by holding an uncoated aluminum surface in parallel with a prefrosted surface. By replacing the overlapping in-plane dry zones with a uniform out-of-plane dry zone, we show that even an uncoated aluminum surface can stay almost completely dry in chilled and supersaturated conditions. Using a blend of experiments and numerical simulations, we show that the critical separation required to keep the surface dry is a function of the ambient supersaturation.

An examination of microstructural evolution in a Pb–Sn eutectic alloy processed by high-pressure torsion and subsequent self-annealing

Abstract The Pb–Sn alloy has a wide use in the electronic, energy storage and nuclear industries and a fine-grained Pb–Sn alloy may open up new possibilities for applications in these industries. In order to understand the behavior of grain refinement, a Pb-62% Sn eutectic alloy was processed by high-pressure torsion (HPT), stored at room temperature (RT) and then the microstructures of the alloy after HPT were repeatedly investigated during the course of self-annealing using electron backscatter diffraction, scanning electron microscopy and transmission electron microscopy. It is demonstrated that there is a large fraction of twin boundaries with a twin relationship of 62.8° in the microstructure of the initial as-cast condition. Due to the presence of the high imposed pressure, the mobility of Ʃ21 boundaries at 71° is greatly favoured during processing by HPT. After the high pressure is removed, the mobility of dislocation-twin boundaries near 62.8° is then favoured. Processing by HPT significantly increases the solubility of Sn in the Pb phase. The supersaturated state of Sn in Pb is not stable during self-annealing at RT and instead a decomposition of Sn from the Pb-rich phase is observed after storage for 16 days. The main mechanism for this decomposition is lattice diffusion.