Supersaturated State Research Articles

Improved Modeling of Mars' HDO Cycle Using a Mars' Global Climate Model

AbstractHDO and the D/H ratio are essential to understand Mars past and present climate, in particular with regard to the evolution through ages of the Martian water cycle. We present here new modeling developments of the HDO cycle with the Laboratoire de Météorologie Dynamique Mars Global Climate Model (GCM). The present study aims at exploring the behavior of the D/H ratio cycle and its sensitivity to the modeling of water ice clouds and the formulation of the fractionation by condensation. Our GCM simulations are compared with observations provided by the Atmospheric Chemistry Suite (ACS) on board the ESA/Roscosmos Trace Gas Orbiter (TGO), and reveal that the model quite well reproduces the temperature and water vapor fields, which offers a good basis for representing the D/H ratio cycle. The comparison also emphasizes the importance of modeling the state of supersaturation, resulting from the microphysical processes of water ice clouds, to correctly account for the water vapor and the D/H ratio of the middle‐to‐upper atmosphere. This work comes jointly with a detailed comparison of the measured D/H profiles by TGO/ACS and the model outputs, conducted in the companion paper of Rossi et al. (2022, https://doi.org/10.1029/2022JE007201) (this issue).

Physical-chemical factors influencing the vertical distribution of phototrophic pico-nanoplankton in the Oxygen Minimum Zone (OMZ) off Northern Chile: The relative influence of low pH/low O2 conditions

The vertical distribution of phytoplankton is of fundamental importance in the structure, dynamic, and biogeochemical pathways in marine ecosystems. Nevertheless, what are the main factors determining this distribution remains as an open question. Here, we evaluated the relative influence of environmental factors that might control the coexistence and vertical distribution of pico-nanoplankton associated with the OMZ off northern Chile. Our results showed that in the upper layer Synechococcus-like cells were numerically important at all sampling stations. Pico-nano eukaryotes and phototrophic nanoflagellates (PNF) also showed high abundances in the upper layer decreasing in abundance down to the upper oxycline, while only Prochlorococcus showed high abundances under oxycline and within the oxygen-depleted layer. Statistical analyses evidenced that temperature, oxygen, and carbonate chemistry parameters (pH and dissolved inorganic carbon, DIC) influenced significantly the vertical distribution of phototrophic pico-nanoplankton. Additionally, we experimentally-evaluated the combined effect of low pH/low O2 conditions on a nanophytoplankton species, the haptophyte Imantonia sp. Under control conditions (pH = 8.1; O2 = 287.5 μM, light = 169.6 μEm−2s−1), Imantonia sp. in vivo fluorescence increased over fifty times, inducing supersaturated O2 conditions (900 μM) and an increasing pH (8.5), whereas upon an experimental treatment mimicking OMZ conditions (pH = 7.5; O2 = 55.6 μM; light = 169.6 μEm−2s−1), in vivo fluorescence declined dramatically, suggesting that Imantonia sp. did not survive. Although preliminary, our study provides evidence about the role of low pH/low O2 conditions on the vertical distribution of nanophytoplankton, which deserve future attention through both fieldwork and more extended experimental experiences.

Nanomodification of the system СаО−SO3−H2O

Problem statement. The process of structure formation generally depends on the initial composition of binders and additives affecting the hydration process. Analysis of the technical literature shows that in the manufacture of mineral binders, preference is given to the creation of composite binders and the use of various additives and factors influencing the hydration process. Particular interest are nanoadditives. Purpose of research. Determination of surfactants and nanoadditives influence on the process of hydration and structure formation for gypsum binders. Conclusions. Investigations on the directional regulation of the gypsum binders’ properties have shown that the specific surface area of various anisotropic surfaces regulates the shape of the crystals as well as their formation and growth kinetics. It was found that the process of gypsum binders hydration and formation can be regulated using the specific surface dimensions, the nanoadditives parameters, as well as by changing the concentration in the solution. The influence of micro- and nanoadditives on the change of the system surface energy, as well as on introduction of plasticizer and change of time solution is in the supersaturated state (which increases the number of nuclear centers of crystallization) was experimentally and theoretically determined and proved.

Preparation of Dual‐Scale TiC‐Precipitated Bainitic Wear‐Resistant Steel by Solid Solution and Forging Deformation

Preparation of Dual‐Scale TiC‐Precipitated Bainitic Wear‐Resistant Steel by Solid Solution and Forging Deformation

Another Move towards Bicalutamide Dissolution and Permeability Improvement with Acetylated β-Cyclodextrin Solid Dispersion.

The complex formation of antiandrogen bicalutamide (BCL) with methylated (Me-β-CD) and acetylated (Ac-β-CD) β-cyclodextrins was investigated in buffer solution pH 6.8. A two-fold strongly binding of BCL to Ac-β-CD as compared to Me-β-CD was revealed. The solid dispersion of BCL with Ac-β-CD was prepared by the mechanical grinding procedure to obtain the complex in the solid state. The BCL/Ac-β-CD complex was characterized by DSC, XPRD, FTIR, and SEM techniques. The effect of Ac-β-CD in the BCL solid dispersions on the non-sink dissolution/permeation simultaneous processes was disclosed using the side-by-side diffusion cell with the help of the cellulose membrane. The elevated dissolution of the ground complex, as compared to the raw drug as well as the simple physical mixture, accompanied by the supersaturation was revealed. Two biopolymers—polyvinylpyrrolidone (PVP, Mn = 58,000) and hydroxypropylmethylcellulose (HPMC, Mn ~ 10,000)—were examined as the precipitation inhibitors and were shown to be useful in prolonging the supersaturation state. The BCL/Ac-β-CD complex has the fastest dissolution rate in the presence of HPMC. The maximal concentration of the complex was achieved at a time of 20, 30, and 90 min in the pure buffer, with PVP and with HPMC, respectively. The effectiveness of the BCL dissolution (release) processes (illustrated by the parameter) was estimated to be 7.8-, 5.8-, 3.0-, and 1.8-fold higher for BCL/Ac-β-CD (HPMC), BCL/Ac-β-CD (PVP), BCL/Ac-β-CD (buffer), and the BCL/Ac-β-CD physical mixture, respectively, as compared to the BCL_raw sample. The excipient gain factor (EGF), calculated for the dissolution of the BCL complex, was shown to be 2.6 in the presence of HPMC, which is 1.3-fold greater as compared to PVP. From the experimental dissolution results, it can be concluded that the formation of BCL ground complex with Ac-β-CD enhances the dissolution rate of the compound. The permeation was also shown to be advantageous in the presence of the polymers, which was demonstrated by the elevated fluxes of BCL through the membrane. The comparison of the dissolution/permeation processes was illustrated and discussed. The conclusion was made that the presence of HPMC as a stabilizer of the supersaturation state is promising and seems to be a useful tool for the optimization of BCL pharmaceutical formulations manufacturing.

Shedding Synchrotron Light on Catalyst Strain Dynamics in Electrochemical Environment

In the case of heterogeneous catalysis (where the reactions occur onto the catalyst surface), the most promising approach in material design follows the Sabatier principle: the ability of the surface to bind adsorbates and the strength of the bonds define the reaction thermodynamics and kinetics. In this respect, the catalyst surface chemistry and structure (crystallographic orientation of the facets and/or strain) are used as levers to optimize its performance. However, it is largely accepted that the structure of PEMWE anode and PEMFC cathode catalysts does not remain unaltered over the long term operation due to harsh (electro)chemical conditions and it is of a high interest to understand the structural changes during the electrocatalysis. In this contribution we use X-ray diffraction techniques to qualitatively and quantitatively describe those changes and shed light on the strain evolution in nanostructured catalysts during operation in the electrochemical environment.Using the newly upgraded 4th generation EBS source at European Synchrotron Radiation Facility, we study Pt and Pd catalysts in liquid half cells at various potentials. In the Pd case we focus on the phase and structural dynamics during H insertion, allowing to unveil the electrochemically-driven Pd hydrides phase transition, which was until now mostly investigated in the gas phase. The fine XRD patterns measured operando provided the first detection of theoretically predicted supersaturated and undersaturated metastable states, involved in a core-shell mechanism of the phase transition (Figure 1) [1].In the case of Pt nanocatalyst, monitoring the structural features of the catalyst during cyclic voltammetry permits studying adsorption and oxidation processes. Deconvoluting both effects (adsorption and oxidation) is possible by following different parameters of the analyzed XRD patterns with high temporal resolution. Such experiments reveal important dynamic trends linked to the surface oxidation and degradation, directly impacting the output of accelerated stress tests (AST) [2]. Carefully determining the charge passed through the circuit during the CV also allows to establish a near-linear correlation between the expansion of the bulk lattice parameter of Pt nanoparticles and their oxide surface coverage. Since the latter is known to be a descriptor of catalysts activity toward numerous reactions (oxygen reduction and fuel oxidation), the measurement of the lattice parameter according to this simple diffraction approach allows experimental access to this descriptor during operando measurements in device-relevant sample environments [2]. This constitutes a main advantage compared to spectroscopic techniques and is foreseen to find a wide range of applications, as demonstrated by measuring the structural behavior of the state-of-the-art PtNiIr octahedra catalyst in operating PEMFC. In this case, the results allow correlating the degradation of the catalysts cycled to different lower potentials with the oxidation and strain dynamics. Based on this data, the operating conditions for this catalyst can be determined, further defining the application of this material.[1] Chattot, R. et al., J. Am. Chem. Soc. 143(41), 17068–17078 (2021).[2] Martens, I. et al., ACS Appl. Energy Mater. 2 (11), 7772-7780 (2019). Figure 1

Ultrascalable Surface Structuring Strategy of Metal Additively Manufactured Materials for Enhanced Condensation.

Metal additive manufacturing (AM) enables unparalleled design freedom for the development of optimized devices in a plethora of applications. The requirement for the use of nonconventional aluminum alloys such as AlSi10Mg has made the rational micro/nanostructuring of metal AM challenging. Here, the techniques are developed and the fundamental mechanisms governing the micro/nanostructuring of AlSi10Mg, the most common metal AM material, are investigated. A surface structuring technique is rationally devised to form previously unexplored two‐tier nanoscale architectures that enable remarkably low adhesion, excellent resilience to condensation flooding, and enhanced liquid–vapor phase transition. Using condensation as a demonstration framework, it is shown that the two‐tier nanostructures achieve 6× higher heat transfer coefficient when compared to the best filmwise condensation. The study demonstrates that AM‐enabled nanostructuring is optimal for confining droplets while reducing adhesion to facilitate droplet detachment. Extensive benchmarking with past reported data shows that the demonstrated heat transfer enhancement has not been achieved previously under high supersaturation conditions using conventional aluminum, further motivating the need for AM nanostructures. Finally, it has been demonstrated that the synergistic combination of wide AM design freedom and optimal AM nanostructuring method can provide an ultracompact condenser having excellent thermal performance and power density.

Molecular dynamics simulation of bulk nanobubbles

The long-term stability of nanobubbles with high internal gas pressure is a puzzling question for nanobubble researchers. The classical Molecular Dynamics simulation based on LAMMPS software was used to evaluate the performance of an oxygen nanobubble with high gas density. This research consists of two main cases. In the first case, bubble behavior was examined with 3247 O2 molecules embedded in a 4.5 nm radius spherical volume to represent the bubble and was surrounded by 438,490 H2O molecules with 1 g/cm3 density. In the second case, the parametric study was conducted while maintaining the same parameters where the amount of O2 molecules changed at the initial configuration. Hence six different O2 bubble configurations were simulated under two different temperature settings, 20 ℃ and 30 ℃. The Lennard Jones potentials are used for molecular interactions. The simulations were run first under the NVT and then changed to the NPT ensemble. Simulation results were analyzed for bubble size, pressure, surface tension, gas diffusion, the influence of internal initial gas densities, gas concentration, and temperature conditions. The high initial gas concentration with high initial internal gas density causes a more stable bubble condition under both NVT and NPT ensembles. This stability can be attributed to the gas supersaturation conditions. The systems with low initial internal gas densities transferred to a smaller radius gas cluster with a high internal density as they shifted to the NPT ensemble. The system with a higher temperature causes elevated system pressures at NVT and volume expansion during NPT. Under NVT simulation, bubble size was higher at lower temperatures. Under NPT conditions, bubble size increases for larger initial density cases and decreases for lower density cases. Further increased temperature causes faster gas diffusion, and higher internal bubble pressure leads to unstable conditions.

Physical Simulation of Laser Surface Treatment to Study Softening Effect on Age-Hardened Aluminium Alloys

The automotive industry is interested in manufacturing components with tailored mechanical properties. To this end, advanced heating treatments can be exploited to obtain the so-called Tailored Heat-Treated Blanks (THTB). However, mechanical properties are strongly affected by the process parameters of heating treatments, which require a preliminary design. Physical simulation can be a decisive tool in this phase to obtain useful information at the laboratory scale, even when heat treatments such as those carried out with laser technologies impose high heating and cooling rates on the material. This work uses physical simulation to investigate the changes in strength and ductility caused by laser heat treatment (LHT) on aluminum alloys hardened by aging; the methodology was implemented on the EN AW 6082 T6 alloy. First, a finite-element (FE) transient thermal model was developed to simulate LHT by varying the process parameters (laser power/peak temperature and treatment speed). Second, the resulting thermal cycles were physically simulated by means of the Gleeble 3180 system. Third, the strength and the ductility of physically simulated specimens were evaluated through micro-hardness and tensile tests; to study aging effects, investigations were performed both (i) right after Gleeble tests (samples in the supersaturated solid state, i.e., as-physically simulated (APS) state) and (ii) after one week from Gleeble tests (aged specimens—T4 state). The obtained results show that there are peak temperatures that guarantee maximum softening levels for each investigated state (T4 and APS). The optimal peak temperature ranges are in agreement with the data in the literature, demonstrating that the proposed methodology is suitable for the study of softening phenomena on aging-hardened aluminum alloys.

Beeswax crystals form a network structure in highly unsaturated oils and O/W emulsions under supersaturation and cool temperature conditions

Beeswax (BW) is widely used in structured oil to mimic fat crystals, due to its needle-like crystal structure and effective gelling ability. In this study, the crystallization behavior of BW in liquid oil was analyzed at different cooling temperatures and BW concentrations. Results showed that temperature and BW concentrations played a role in reaching the supersaturation state for the system of BW in linseed oil, with 40%BW at 20 °C and 20%BW at 5 °C, respectively. Short nuclear induction time and higher crystallinity of BW were found at lower cooling temperatures, promoting formation of supersaturation state. In addition, the apparent activation energy of the crystallization process indicates that crystallization is inhibited at high BW concentrations. Furthermore, higher supersaturation levels and lower cooling temperatures affected the droplet size and crystal structure of the O/W emulsions; these conditions accelerated the penetration of crystals through the interfacial membrane and led to droplet aggregation and coalescence. High supersaturation level and low cooling temperature promoted emulsion instability and had a remarkable impact on food quality.

Polymer selection to increase in vitro supersaturation generated by lamotrigine nicotinamide monohydrate cocrystal: An evaluation with predissolved and solid polymers

Cocrystals can improve drug dissolution by generating supersaturated drug delivery systems. However, supersaturation is a high-energetic state with a tendency to precipitate. Polymers are used as precipitation inhibitors to inhibit nucleation or crystal growth. Our aim was to evaluate the influence of different polymers, predissolved or in powder form, on the supersaturation dissolution of lamotrigine-nicotinamide monohydrate (LAM.NIC.H2O) cocrystals. First, the polymers were dissolved in water. Hydroxypropyl methylcellulose polymers (HPMC E6 and HPMC K100LV) presented the greatest dissolution advantage, while polyvinylpyrrolidone presented the most stable dissolution profile. Then, the cocrystal and polymer powder mixture, in different proportions, were simultaneously added to water for dissolution and evaluated to identify the ideal cocrystal/polymer ratio for the development of a solid pharmaceutical dosage form. The cocrystal and polymer powder mixture of HPMC E6 and HPMC K100 LV (1:0.1 and 1:0.25, w/w) presented the best supersaturation enhancement with high area under the curve values. The study of FaSSIF for cocrystal and HPMC E6 powder mixture (1:0.1 and 1:0.25, w/w) presented promising results, as the supersaturated state was maintained for a relevant period. Thus, this study suggests a polymer selection design for supersaturation studies and supports the future development of LAM.NIC.H2O cocrystal solid formulations.

The Effects of Surface Curvature and Temperature on Charge Transfer During Ice‐Ice Collisions

Repetitive collisions of sublimating ice surfaces, created by freezing liquid water, produced charge separation Q of a magnitude (pC) comparable to earlier results of vapour-grown ice crystals repetitively collided in a saturated environment. Those results had been explained by a theory of charge distribution in a quasi-liquid surface layer QLL mediated at the moment of impact by collisional melting. The present results are from long duration contacts (15ms) with transfer of kinetic energy estimated to be a factor of 104 greater, and charging-rate 98% slower. They do not support an assumption in that proposed mechanism of collisional melting, and are contrary to the basic assumptions of that theory: that significant Q occurs only in growing surfaces (that is, in a supersaturated condition which implies the presence of liquid water), that were originally grown from vapour, and for which contact is less than 1ms. The results are opposite to a rule that in the case of differing surfaces (vapour-grown, and rimed) that which is greater sublimating charges negatively. Here, for surfaces of frozen water, the surface further from equilibrium becomes positively charged. The results are not inconsistent with recent reports of simulations that suggest that the thickness of a quasi-liquid layer QLL in sublimating surfaces may not be less than the equilibrium value. Apparently, for differing ice surfaces, Q is of the order of 1fC whereas for collisions of similar ices on metal substrates (whether both vapour-deposited, or both frozen liquid water) Q is of the order of 1pC.

Supersaturation-Based Drug Delivery Systems: Strategy for Bioavailability Enhancement of Poorly Water-Soluble Drugs.

At present, the majority of APIs synthesized today remain challenging tasks for formulation development. Many technologies are being utilized or explored for enhancing solubility, such as chemical modification, novel drug delivery systems (microemulsions, nanoparticles, liposomes, etc.), salt formation, and many more. One promising avenue attaining attention presently is supersaturated drug delivery systems. When exposed to gastrointestinal fluids, drug concentration exceeds equilibrium solubility and a supersaturation state is maintained long enough to be absorbed, enhancing bioavailability. In this review, the latest developments in supersaturated drug delivery systems are addressed in depth.

Comprehension of the Route for the Synthesis of Co/Fe LDHs via the Method of Coprecipitation with Varying pH.

Co/Fe-based layered double hydroxides (LDHs) are among the most promising materials for electrochemical applications, particularly in the development of energy storage devices, such as electrochemical capacitors. They have also been demonstrated to function as energy conversion catalysts in photoelectrochemical applications for CO2 conversion into valuable chemicals. Understanding the formation mechanisms of such compounds is therefore of prime interest for further controlling the chemical composition, structure, morphology, and/or reactivity of synthesized materials. In this study, a combination of X-ray diffraction, vibrational and absorption spectroscopies, as well as physical and chemical analyses were used to provide deep insight into the coprecipitation formation mechanisms of Co/Fe-based LDHs under high supersaturation conditions. This procedure consists of adding an alkaline aqueous solution (2.80 M NaOH and 0.78 M Na2CO3) into a cationic solution (0.15 M CoII and 0.05 M FeIII) and varying the pH until the desired pH value is reached. Beginning at pH 2, pH increases induce precipitation of FeIII as ferrihydrite, which is the pristine reactional intermediate. From pH > 2, CoII sorption on ferrihydrite promotes a redox reaction between FeIII of ferrihydrite and the sorbed CoII. The crystallinity of the poorly crystalized ferrihydrite progressively decreases with increasing pH. The combination of such a phenomenon with the hydrolysis of both the sorbed CoIII and free CoII generates pristine hydroxylated FeII/CoIII LDHs at pH 7. Above pH 7, free CoII hydrolysis proceeds, which is responsible for the local dissolution of pristine LDHs and their reprecipitation and then 3D organization into CoII4FeII2CoIII2 LDHs. The progressive incorporation of CoII into the LDH structure is accountable for two phenomena: decreased coulombic attraction between the positive surface-charge sites and the interlayer anions and, concomitantly, the relative redox potential evolution of the redox species, such as when FeII is re-oxidized to FeIII, while CoIII is re-reduced to CoII, returning to a CoII6FeIII2 LDH. The nature of the interlamellar species (OH−, HCO3−, CO32− and NO3−) depends on their mobility and the speciation of anions in response to changing pH.

Formation of lower bainite in a high carbon steel – an in-situ synchrotron XRD study

The microstructural evolution of and simultaneous dimensional changes in high-carbon SAE 52100 bearing steel were monitored continuously during austempering for 120 min at selected temperatures in the range of 210 °C-270 °C, and also during its subsequent tempering to 340 °C for an additional 120 min, via high-energy X-ray diffraction in real time and in-situ dilatometry. The austenite-to-bainitic ferrite transformation induces lattice defects and internal lattice stresses that increase with austempering time and at lower austempering temperatures. These changes are evidenced by the increase in the full-width half-maximum of the relevant reflections in X-ray diffraction. The lattice parameter of bainitic ferrite takes its highest value during the early stages of austempering, and then gradually decreases as the transformation progresses. This observation points to an initial state of carbon supersaturation in the ferritic lattice that is likely reducing due to carbon segregation close to dislocations, fine carbide precipitation within the bainitic ferrite, and carbon partitioning into the surrounding austenite. The carbon partitioning into austenite is evidenced in particular at the higher austempering temperatures of 240 °C and 270 °C, at which there is a noticeable increase in the lattice parameter of the remaining austenite at longer times. The dimensions of the bearing steel specimens are governed by the volume change due to the formation of bainitic ferrite during austempering and by the relaxation of its lattice distortion during tempering at 340 °C in the absence of further phase transformation.

Quantification of Nucleation Site Density as a Function of Surface Wettability on Smooth Surfaces

AbstractDew water is recognized as a valuable source of clean water for human consumption. Given the developing concerns over global water scarcity, great focus has been turned toward increasing the efficiency of existing dew harvesting methodologies. Droplet nucleation is a critical first stage in the condensation process – and therefore key to dew water harvesting. In this paper, the droplet nucleation site density (Ns) as a function of surface wettability on smooth thin polymer films is quantified. A custom‐built environment chamber, operated in low supersaturation conditions relevant to atmospheric water harvesting, allows strict experimental control over temperature and humidity. Droplet growth through coalescence is quantified, and an exponential increase in the rate of coalescence is seen as the test surface wettability increased. Ns declines exponentially as wettability decreases according to the fitted equation Ns = 1.1 × 1011e−0.043θ , where theta is the contact angle of the smooth surface, which can be used to predict Ns from a known contact angle, currently not available. The average distance between droplet centers is found to increase at a linear rate. This nucleation behavior is in line with those of droplets in a Rayleigh distribution.

Glass phase microstructure and mechanical behaviors of laser-remelted Ni30Cr25Al15Co15Mo5Ti5Y5 coating reinforced by α/γ-Al2O3 phase

A novel Ni30Cr25Al15Co15Mo5Ti5Y5 reinforced coating by α/γ-Al2O3 was prepared using supersonic particle deposition (SPD), the coating was remelted to optimize internal structure via laser. Much ultrafine grains (UFGs) (86.5%) and nano-crystal grains (NGs) (13.4%) in the laser-remelted coating reinforced by α/γ-Al2O3 was found because the high melting point of the ultrafine α/γ-Al2O3 hindered the nucleation and crystal growth, the diffusion and redistribution of HEA element atoms could not occur, indicated the formation of a homogeneous metastable supersaturated compound. The dispersed diffraction peak was accompanied by α-Al2O3 dispersion phase in the remelted coating that was macroscopically isotropic. Due to the strengthening effect of the phase particles for α/γ-Al2O3 dispersion phase, most internal stress was released in the HEA coating. Under deep undercooling, the friction and wear resistance was ensured by the remelted coating reinforced by α/γ-Al2O3 strengthening phase due to the glass transition effect of the HEA coating in the supersaturated state.

Packaging contests between viral RNA molecules and kinetic selectivity.

The paper presents a statistical-mechanics model for the kinetic selection of viral RNA molecules by packaging signals during the nucleation stage of the assembly of small RNA viruses. The effects of the RNA secondary structure and folding geometry of the packaging signals on the assembly activation energy barrier are encoded by a pair of characteristics: the wrapping number and the maximum ladder distance. Kinetic selection is found to be optimal when assembly takes place under conditions of supersaturation and also when the concentration ratio of capsid protein and viral RNA concentrations equals the stoichiometric ratio of assembled viral particles. As a function of the height of the activation energy barrier, there is a form of order-disorder transition such that for sufficiently low activation energy barriers, kinetic selectivity is erased by entropic effects associated with the number of assembly pathways.

Proteins Do Not Replicate, They Precipitate: Phase Transition and Loss of Function Toxicity in Amyloid Pathologies.

Simple SummaryAmyloid aggregation of proteins in disease has been known for over a hundred years; however, effective therapeutics for amyloid pathologies such as Alzheimer’s disease and Parkinson’s disease are still lacking. This review divides the amyloid phenomenon into four major questions: What are amyloids? How do amyloids form? Can proteins replicate? How do amyloids cause toxicity? The aim is to answer these questions within a unified physicochemical framework that links the structural biology of amyloids to the thermodynamics of amyloid formation and the pathophysiology of amyloid aggregates in different diseases. We illustrate that the thermodynamics of protein aggregation does not support the prion protein-only replication hypothesis, and how the structural biology of amyloids makes them largely domainless, generic, and inert. The implications of this understanding for the etiology, pathogenesis and potential therapeutics of amyloid diseases are briefly discussed.Protein aggregation into amyloid fibrils affects many proteins in a variety of diseases, including neurodegenerative disorders, diabetes, and cancer. Physicochemically, amyloid formation is a phase transition process, where soluble proteins are transformed into solid fibrils with the characteristic cross-β conformation responsible for their fibrillar morphology. This phase transition proceeds via an initial, rate-limiting nucleation step followed by rapid growth. Several well-defined nucleation pathways exist, including homogenous nucleation (HON), which proceeds spontaneously; heterogeneous nucleation (HEN), which is catalyzed by surfaces; and seeding via preformed nuclei. It has been hypothesized that amyloid aggregation represents a protein-only (nucleic-acid free) replication mechanism that involves transmission of structural information via conformational templating (the prion hypothesis). While the prion hypothesis still lacks mechanistic support, it is also incompatible with the fact that proteins can be induced to form amyloids in the absence of a proteinaceous species acting as a conformational template as in the case of HEN, which can be induced by lipid membranes (including viral envelopes) or polysaccharides. Additionally, while amyloids can be formed from any protein sequence and via different nucleation pathways, they invariably adopt the universal cross-β conformation; suggesting that such conformational change is a spontaneous folding event that is thermodynamically favorable under the conditions of supersaturation and phase transition and not a templated replication process. Finally, as the high stability of amyloids renders them relatively inert, toxicity in some amyloid pathologies might be more dependent on the loss of function from protein sequestration in the amyloid state rather than direct toxicity from the amyloid plaques themselves.

Research and Application of Supersaturated Dissolved Oxygen Technology Combined with Magnetization Technology in the Improvement of Water Quality: Taking the South-to-North Water Diversion Project of China as a Pilot Project

Supersaturated dissolved oxygen and magnetization (SDOXM) technology is a composite technology that combines supersaturated dissolved oxygen with water magnetization technologies. Compared with conventional water purification technology, the advantages introduced by such technology include obvious and efficient improvement in purified water quality without adding any chemicals, removing sludge and changing the original function of the river. In this study, taking the Middle-Route (MR) of the South-to-North Water Diversion Project of China (SNWDPC) as a pilot project, the effects of the SDOXM composite process on microbial activity, phytoplankton community structure, and removal efficiency of the main nutritional indexes in the canal of the MR were evaluated. Aiming at static and flowing water bodies, this study was divided into two parts: static and dynamic experiments (two groups: a group with artificial aquatic plants and another group without artificial aquatic plants). The performance of the SDOXM system was assessed by monitoring the organic matter removal as well as the relative light unit (RLU) of ATP, changes in the community structure of phytoplankton, and the effects of artificial aquatic plants as a biofilm carrier on organic matter removal and microbial activity. During the study period, SDOXM technology was able to increase the concentration of dissolved oxygen (DO) in water and maintained the state of supersaturation for more than three days. The removal effect of organic matter from water was obvious. The community structure of phytoplankton changed from the Bacillariophyta-Cyanophyta type to the Bacillariophyta-Cyanobacteria type. Finally, the introduction of artificial aquatic plants has contributed to the improvement in water quality. Therefore, SDOXM technology can be used as a new water quality improvement technology to enhance the self-restoration ability of a river natural ecology.