Early Stages Of Synthesis Research Articles

One-shot Federated Learning on Medical Data using Knowledge Distillation with Image Synthesis and Client Model Adaptation.

One-shot federated learning (FL) has emerged as a promising solution in scenarios where multiple communication rounds are not practical. Notably, as feature distributions in medical data are less discriminative than those of natural images, robust global model training with FL is non-trivial and can lead to overfitting. To address this issue, we propose a novel one-shot FL framework leveraging Image Synthesis and Client model Adaptation (FedISCA) with knowledge distillation (KD). To prevent overfitting, we generate diverse synthetic images ranging from random noise to realistic images. This approach (i) alleviates data privacy concerns and (ii) facilitates robust global model training using KD with decentralized client models. To mitigate domain disparity in the early stages of synthesis, we design noise-adapted client models where batch normalization statistics on random noise (synthetic images) are updated to enhance KD. Lastly, the global model is trained with both the original and noise-adapted client models via KD and synthetic images. This process is repeated till global model convergence. Extensive evaluation of this design on five small- and three large-scale medical image classification datasets reveals superior accuracy over prior methods. Code is available at https://github.com/myeongkyunkang/FedISCA.

Aldehyde-catalysed carboxylate exchange in α-amino acids with isotopically labelled CO2.

The isotopic labelling of small molecules is integral to drug development and for understanding biochemical processes. The preparation of carbon-labelled α-amino acids remains difficult and time consuming, with established methods involving label incorporation at an early stage of synthesis. This explains the high cost and scarcity of C-labelled products and presents a major challenge in 11C applications (11C t1/2 = 20 min). Here we report that aldehydes catalyse the isotopic carboxylate exchange of native α-amino acids with *CO2 (* = 14, 13, 11). Proteinogenic α-amino acids and many non-natural variants containing diverse functional groups undergo labelling. The reaction probably proceeds via the trapping of *CO2 by imine-carboxylate intermediates to generate iminomalonates that are prone to monodecarboxylation. Tempering catalyst electrophilicity was key to preventing irreversible aldehyde consumption. The pre-generation of the imine carboxylate intermediate allows for the rapid and late-stage 11C-radiolabelling of α-amino acids in the presence of [11C]CO2.

Nanoarchitecturing bimetallic manganese cobaltite spinels for sonocatalytic degradation of oxytetracycline

Degradation of contaminants of emerging concern in aqueous media using bimetallic oxides is a promising novel strategy that requires engineering new catalytic routes in bimetallic oxides to perform advanced oxidation; however, several challenges to synthesizing and developing such materials with enhanced, sustainable catalytic features are still being investigated. This study presents the effective use of a manganese cobaltite bimetallic spinel compound for sonocatalysis. We prepared three morphologies of manganese cobaltite for using in the sonocatalytic degradation of oxytetracycline (OTC). The morphology of manganese cobaltite was tuned by changing the amounts of the Mn and Co precursors in the early stage of synthesis. Several manganese cobaltite spinels with different structures—porous layered-like cubes (MCO-PLC), layered-like ellipsoids (MCO-LE), and rough spheroids (MCO-RS) were obtained and characterized using various techniques. A promising catalytic degradation capability of MCO-PLC for OTC (10.0 mg L−1) was obtained at a natural pH within 120 min. We also investigated the reusability of MCO-PLC sonocatalyst and metal (Mn and Co) leaching in water media. The sonocatalytic mechanisms and fragments produced from OTC during degradation were determined via electron paramagnetic resonance and gas chromatography-mass spectroscopy analyses.

Prediction of Residual Curing Capacity of Melamine-Formaldehyde Resins at an Early Stage of Synthesis by In-Line FTIR Spectroscopy.

Melamine-formaldehyde (MF) resins are widely used as surface finishes for engineered wood-based panels in decorative laminates. Since no additional glue is applied in lamination, the overall residual curing capacity of MF resins is of great technological importance. Residual curing capacity is measured by differential scanning calorimetry (DSC) as the exothermic curing enthalpy integral of the liquid resin. After resin synthesis is completed, the resulting pre-polymer has a defined chemical structure with a corresponding residual curing capacity. Predicting the residual curing capacity of a resin batch already at an early stage during synthesis would enable corrective measures to be taken by making adjustments while synthesis is still in progress. Thereby, discarding faulty batches could be avoided. Here, by using a batch modelling approach, it is demonstrated how quantitative predictions of MF residual curing capacity can be derived from inline Fourier Transform infrared (FTIR) spectra recorded during resin synthesis using partial least squares regression. Not only is there a strong correlation (R2 = 0.89) between the infrared spectra measured at the end of MF resin synthesis and the residual curing capacity. The inline reaction spectra obtained already at the point of complete dissolution of melamine upon methylolation during the initial stage of resin synthesis are also well suited for predicting final curing performance of the resin. Based on these IR spectra, a valid regression model (R2 = 0.85) can be established using information obtained at a very early stage of MF resin synthesis.

Nanoparticles Size Distribution Assessment During Early Synthesis Stages

Nanotechnology, an innovative field of material science, designs and produces nanostructures materials with unique properties that make them suited for various bioengineering applications. The shape and the dimension are the main variables depending on the method of synthesis or chemical precursors. Silver nanoparticles obtained through chemical synthesis exhibit as strong antibacterial effect if their size lays in a well-defined range. However, a small size of such particles, in the range of nanometers to several tens of nanometers, requires specific techniques as Dynamic Light Scattering or Transmission Electron Microscopy, both being affected by certain assumptions or by the high cost and long time required for a measurement. A nonconventional method based on Direct Particle Tracking can be used to produce the particle size distribution in the early nanoparticle synthesis stages. The work presents a realistic computer simulation of nanoparticle diffusion performed with the CHODIN code and a size distribution assessment using a code for Direct Particle Tracking written for this purpose. The results are consistent with the particle size used for simulation and states as a proof of concept for using the Direct Particle Tracking method for particle size distribution in the early stages of nanoparticle synthesis.

Kinetic studies of biocatalyzed copolyesters of poly(butylene succinate) (PBS) containing fully bio-based dilinoleic diol

A series of segmented bio-copolyesters based on crystallizable hard segments of poly(butylene succinate) (PBS) and fully bio-based dilinoleic diol (DLAOH), creating dilinoleic succinate (DLS) soft segments, were prepared by enzymatically catalyzed polycondensation. The kinetic studies performed with 1H NMR and SEC have proved incorporation of highly hydrophobic DLAOH into the polymer backbone. We found that the efficacy of DLAOH incorporation was limited by the catalytic pocket size of the enzyme and its hydrophobic nature favouring the formation of long PBS sequences, especially at the early synthesis stages and having an effect on final content of soft segments compared to feed ratio. Based on quantitative 13C NMR analysis we found that copolymers had R-values lower than 1, that is low degree of randomness. Differential scanning calorimetry (DSC) revealed changes in degree of crystallinity and the presence of a phase mixed system.

Identification of Early Represented Gluten Proteins during Durum Wheat Grain Development

The time course of biosynthesis and accumulation of storage proteins in developing grains of durum wheat (Triticum turgidum ssp. durum (Desf.) Husn.) pasta-quality reference cv. Svevo was investigated at the protein level for the first time. Seeds were harvested at key kernel developmental stages, namely, 3 (seed increase 3-fold in size), 5 (kernel development, water-ripe stage), 11 (kernel development, water-ripe stage), 16 (kernel full development, water-ripe stage), 21 (milk-ripe stage), and 30 (dough stage) days postanthesis (dpa). Gliadins and glutenins were fractionated according to their different solubility and individually analyzed after fractionation by reversed-phase high performance liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Proteins were identified by liquid chromatography-tandem mass spectrometry of proteolytic peptides. The α- and γ-gliadin were already detected at 3 dpa. The biosynthesis of high molecular mass glutenin Bx7 was slightly delayed (11 dpa). Most of the gluten proteins accumulated rapidly between 11 and 21 dpa, with a minor further increase up to 30 dpa. The expression pattern of gluten proteins in Triticum durum at the early stages of synthesis provides reference data sets for future applications in crop breeding and growth monitoring.

A widespread three-component mechanism for the periplasmic modification of bacterial glycoconjugates

The diverse structures of bacterial glycoconjugates are generally established during the early stages of synthesis by the activities of nucleotide sugar-dependent glycosyltransferases active in the cytoplasm. However, in some cases, further modifications of varying complexity occur after the glycoconjugate is exported to the periplasm. These processes are distinguished by the involvement of polyprenyl monosphosphoryl donors and require glycosyltransferases possessing GT-C folds. Established prototypes are found in modifications of some bacterial lipopolysaccharides, where 4-amino-4-deoxy-l-arabinose is added to lipid A and glucose side branches are used to modify O-antigens. Here we review the current understanding of these systems and describe similarities to other periplasmic glycan modifications in bacteria and the N-glycosylation pathway for assembly of eukaryotic glycoproteins.

An optimization model for evaluating the economic impact of availability and maintenance notions during the synthesis and design of a power plant

In this paper, we introduce an optimization strategy in order to comprehensively quantify the impact of availability and maintenance notions during the early stages of synthesis and design of a new natural gas combined cycle power plant. A detailed state-space approach is thoroughly discussed, where influence of maintenance funds on each component's repair rate is directly assessed.In this context, analysis of the reliability characteristics of the system is centered at two designer-adopted parameters, which largely influence the obtained results: the number of components which may fail independently at the same time, and the number of simultaneous failure/repair events.Then, optimal solutions are evaluated as the availability-related parameters and the amount of resources assigned for maintenance actions are varied across a wide range of feasible values, which enable obtaining more accurate and detailed estimations of the expected economic performance for the project when compared with traditional economic evaluation approaches.

The superiority of silver nanoellipsoids synthesized via a new approach in suppressing the coffee-ring effect during drying and film formation processes

Silver nanoellipsoids (Ag NEs) with about 40 nm diameter minor axis and 100 nm major axis were prepared by a typical polyol process in the presence of poly(vinyl pyrrolidone), using Cl− as etching agent at the early stage of synthesis and poly(ethylene glycol) at the later stage to control the size. A suspension of these kinds of Ag NEs can resist the coffee-ring effect and deposit uniform films after drying. By contrast, suspensions of spherical silver nanoparticles suffer the coffee-ring effect badly, always leaving a ring on the edge of patterns after evaporation is complete. The reasons behind these phenomena can be mainly attributed to the long-ranged interparticle attraction between Ag NEs that preserves them from being transported by Marangoni flows during the drying process. These Ag NEs will be very useful in the preparation of conductive inks. They can perform well in the solidification process of printed patterns, forming uniform and smooth films, greatly enhancing the printing efficiency.

Transformation of Ag Nanocubes into Ag–Au Hollow Nanostructures with Enriched Ag Contents to Improve SERS Activity and Chemical Stability

We report a strategy to complement the galvanic replacement reaction between Ag nanocubes and HAuCl4 with co-reduction by ascorbic acid (AA) for the formation of Ag-Au hollow nanostructures with greatly enhanced SERS activity. Specifically, in the early stage of synthesis, the Ag nanocubes are sharpened at corners and edges because of the selective deposition of Au and Ag atoms at these sites. In the following steps, the pure Ag in the nanocubes is constantly converted into Ag(+) ions to generate voids owing to the galvanic reaction with HAuCl4, but these released Ag(+) ions are immediately reduced back to Ag atoms and are co-deposited with Au atoms onto the nanocube templates. We observe distinctive SERS properties for the Ag-Au hollow nanostructures at visible and near-infrared excitation wavelengths. When plasmon damping is eliminated by using an excitation wavelength of 785 nm, the SERS activity of the Ag-Au hollow nanostructures is 15- and 33-fold stronger than those of the original Ag nanocubes and the Ag-Au nanocages prepared by galvanic replacement without co-reduction, respectively. Additionally, Ag-Au hollow nanostructures embrace considerably improved stability in an oxidizing environment such as aqueous H2O2 solution. Collectively, our work suggests that the Ag-Au hollow nanostructures will find applications in SERS detection and imaging.

Spontaneous Movement of Transmembrane Segments from SecY into the Membrane

At an early stage of synthesis, nearly all membrane proteins are targeted to a protein-conducting channel in the membrane, the SecY/Sec61 complex. Access of the nascent protein to the membrane occurs via a lateral gate, located at the interface of the two halves of the channel. Recently, we structurally resolved a membrane-protein insertion intermediate state of SecY bound to a translating ribosome with a transmembrane (TM) segment at the lateral gate, between channel and membrane. Beginning from that state, we have now carried out multi-microsecond simulations of different putative TM segments at SecY's lateral gate using Anton, a special-purpose molecular dynamics computer from DE Shaw Research. The simulations reveal spontaneous motion of the TM segment, either toward membrane or toward the channel interior, depending on its sequence. Diffusion of the TM segment into the membrane is generated through interactions with individual lipid molecules, which rapidly envelop a hydrophobic TM segment but reject a hydrophilic one. Subsequent free-energy calculations quantify and support the generality of the spontaneous motions observed in individual simulations. Thus, we suggest that the discrimination step between membrane-inserted and secreted states of a nascent protein occurs primarily in the SecY channel.

Ultrasonic pretreatment for hydrothermal synthesis of SAPO-34 nanocrystals

Synthesis of SAPO-34 nanocrystals which has been recently considered as a challenging task was successfully performed by sonochemical method using TEAOH as structure directing agent (SDA). The products were characterized by XRD, SEM, EDX, BET and TGA. The average crystal size of the final product prepared sonochemically is 50 nm that is much smaller than that of synthesized under hydrothermal condition and the morphology of the crystals changes from uniform spherical nanoparticles to spherical aggregates of cube type SAPO-34 crystals respectively. In the case of sample synthesized sonochemically with aid of hydrothermal condition, the surface area is significantly upper than that of obtained by the conventional static hydrothermal technology with almost the same crystallinity. SAPO-34 framework synthesized by just ultrasonic treatment is unstable and a significant part of SAPO-34 nanocrystals is transformed to the dense phase of AlPO 4 structure, i.e., Cristobalite. Contrary to hydrothermal method that at least 24 h of the synthesis time is required to obtain fully crystalline SAPO-34, sonochemical-assisted hydrothermal synthesis of samples leads to form fully crystalline SAPO-34 crystals taking only 1.5 h. In a sonochemical process, a huge density of energy for crystallization is provided by the collapse of bubbles which formed by ultrasonic waves. The fact that small SONO-SAPO-34 crystals could be prepared by the sonochemical method suggests a high nucleation density in the early stages of synthesis and slow crystal growth after nucleation.

Geldanamycin selectively targets the nascent form of ERBB3 for degradation

Heat shock protein 90 (HSP90) targets a broad spectrum of client proteins with divergent modes of interaction and consequences. The homologous epidermal growth factor receptor (EGFR) and ERBB2 receptors as well as kinase-deficient mutants thereof differ in their requirement for HSP90 in the nascent versus mature state of the receptor. Specific features of the kinase domain have been implicated for the selective association of HSP90 with mature ERBB2. We evaluated the role of HSP90 for the homologous ERBB3 receptor. ERBB3 is naturally kinase deficient, a central mediator in cell survival and stress response and the primary dimerization partner for ERBB2 in signaling. Cellular studies indicate that, similar to EGFR, the geldanamycin (GA) sensitivity of ERBB3 and HSP90 binding resides in the nascent state and is dependent on the presence of the kinase domain of ERBB3. Furthermore, despite its intrinsic lack of kinase activity and in contrast to the reported GA sensitivity of mature and kinase-deficient EGFR, the GA sensitivity of the nascent state of ERBB3 appears to be exclusive. Geldanamycin disrupts the interaction of ERBB3 and HSP90 and inhibits ERBB3 maturation at an early stage of synthesis, prior to export from the ER. Studies with a photo-convertible fusion protein of ERBB3 suggest geldanamycin sensitivity at a later stage in maturation, possibly through the putative role of HSP90 in structural proofreading.

Multiple roles of TorD-like chaperones in the biogenesis of molybdoenzymes

Biogenesis of prokaryote molybdoenzymes is a complex process leading to the insertion of the molybdenum cofactor in the cytoplasm into a folded apoenzyme before transport through the cell membrane. Usually, specific chaperones belonging to the TorD family are required for the maturation of the molybdoenzymes of the dimethyl sulfoxide reductase family. These chaperones play a crucial role during the biogenesis and the incorporation of the molybdenum cofactor by interacting with the core of the apoprotein. Moreover, they are also involved in the protection of the apoproteins by binding to their N-terminal extremity in an early stage of synthesis. Finally, the TorD-like proteins may possess a proofreading activity and they could target their partners to the twin arginine translocation machinery system for cross-membrane transport of prefolded proteins. The roles of these chaperones during the different steps of molybdoenzyme biogenesis are described.

Disorder in LixFePO4: From glasses to nanocrystallites

LixFePO4 glasses have been prepared by fast-quenching method in the whole range of composition 0⩽ x ⩽1. The amorphous state of glassy materials is confirmed by X-ray diffraction. Information concerning the local environment of Li and Fe cations and the configuration of (PO4)3− oxo-anions is obtained by Fourier transform infrared (FTIR) spectroscopy. While the LiFePO4 crystalline materials undergo a transition from the paramagnetic to the antiferromagnetic ordering at 52K, no magnetic ordering is observed in the vitreous samples that realize random field systems, so that a spin glass-like freezing is observed at low temperature. The paramagnetic Curie temperature of LixFePO4 is independent of x and shifted to θ=−60K in the glassy state, due to a significant distortion of the FeO6 octahedra that alters the superexchange path inside the atomic FeO4 layers of the crystallized structure. On another hand, the PO4 tetrahedra are not significantly distorted in the glassy phase. The results are compared with highly disordered, but nanocrystallized LiFePO4 recently obtained at the early stage of synthesis by solid state reaction at 300°C. In this latter case, the lack of long-range antiferromagnetic ordering is due to substitutional disorder among the cationic sublattice.

Phase formations during mechanochemical synthesis of PbTiO3

Lead titanate nanopowders were fabricated by mechanochemical synthesis from lead oxide and titanium dioxide. The milling process has been carefully investigated by X-ray diffraction and X-ray excited photoelectron spectroscopy. The first traces of perovskite phase were detected after 5 h synthesis. It was found that intermediated phases (Ti10O18 and Pb3O4) have been formed at the early stage of synthesis. The 50 h milling results in single perovskite phase with average crystallite size of 20 nm.

Mechanism and Modeling of Nanorod Formation from Nanodots

A population balance model based on Smoluchowski aggregation kinetics is developed to explain the formation of nanorods from a colloidal suspension of spherical nanoparticles (nanodots). Our model shows that linear pearl-chain aggregates form by the oriented attachment (OA) of nanodots during the early stages of synthesis, since it occurs with a time scale smaller than the coalescence time scale of nanodots present within an aggregate. The slower coalescence step leads to the transformation of the linear pearl-chain aggregate into a smooth nanorod over a longer time scale of many hours, as observed in experiments. The attachment kinetics is modeled by a modified Brownian collision frequency, with the latter decreasing with nanorod length, leading to the experimentally observed slower growth in nanorod length at longer times. The collision frequency also includes the effects of attractive dipole-dipole and van der Waals interactions between nanodots, which are primarily responsible for OA. Our model predictions are general, and they compare favorably with available experimental data in the literature on the distribution of the aspect ratio (length to diameter) of ZnO and ZnS nanorods over different time scales.

Microporous structure and enhanced hydrophobicity in methylated SiO2 for molecular separation

Methylated microporous silica with high thermal stability and tuneable hydrophobicity was obtained by acid-catalysed sol–gel hydrolysis and condensation of mixtures of tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES). The gels exhibited a trend towards smaller ultramicropores with increasing methyl content, while in addition some supermicropores were formed with sizes of around 2 nm. For low MTES concentration, dilution prior to gelation and ageing resulted in materials with clearly smaller ultramicropores, whereas only a minor effect of dilution on structure was found at high MTES concentration. The small ultramicropore size in ‘diluted’ materials can be associated with a higher extent of condensation of mainly TEOS monomers. Stable structures formed from MTES in an early stage of synthesis may explain the particular micropore structure of MTES-rich gels. With increasing methyl content and with dilution of the sol, the affinity of the surface to water was strongly decreased. The applicability of microporous silica in wet atmospheres may thus be improved by methylation, and their pore structure modified by adaptation of the recipe, which would be highly relevant for industrial gas and liquid separation by inorganic membranes.

Solvothermal Synthesis of Nanostructured Ternary Skutterudite Fe0.5Ni0.5Sb3.

AbstractFor Abstract see ChemInform Abstract in Full Text.