Small Changes In Chemical Composition Research Articles

Correlating the Structure and Gene Silencing Activity of Oligonucleotide-Loaded Lipid Nanoparticles Using Small-Angle X-ray Scattering.

With three FDA-approved products, lipid nanoparticles (LNPs) are under intensive development for delivering wide-ranging nucleic acid therapeutics. A significant challenge for LNP development is insufficient understanding of structure-activity relationship (SAR). Small changes in chemical composition and process parameters can affect LNP structure, significantly impacting performance in vitro and in vivo. The choice of polyethylene glycol lipid (PEG-lipid), one of the essential lipids for LNP, has been proven to govern particle size. Here we find that PEG-lipids can further modify the core organization of antisense oligonucleotide (ASO)-loaded LNPs to govern its gene silencing activity. Furthermore, we also have found that the extent of compartmentalization, measured by the ratio of disordered vs ordered inverted hexagonal phases within an ASO-lipid core, is predictive of in vitro gene silencing. In this work, we propose that a lower ratio of disordered/ordered core phases correlates with stronger gene knockdown efficacy. To establish these findings, we developed a seamless high-throughput screening approach that integrated an automated LNP formulation system with structural analysis by small-angle X-ray scattering (SAXS) and in vitro TMEM106b mRNA knockdown assessment. We applied this approach to screen 54 ASO-LNP formulations while varying the type and concentration of PEG-lipids. Representative formulations with diverse SAXS profiles were further visualized using cryogenic electron microscopy (cryo-EM) to help structural elucidation. The proposed SAR was built by combining this structural analysis with in vitro data. Our integrated methods, analysis, and resulting findings on PEG-lipid can be applied to rapidly optimize other LNP formulations in a complex design space.

Review of Open Cavity Random Lasers as Laser-Based Sensors.

In this review, the concept of open cavity lasing for ultrasensitive sensing is explored, specifically in driving important innovations as laser-based biosensors─a field mostly dominated by fluorescence-based sensing. Laser-based sensing exhibits higher signal amplification and lower signal-to-noise ratio due to narrow emission lines as well as high sensitivity due to nonlinear components. The versatility of open cavity random lasers for probing analytes directly which is ultrasensitive to small changes in chemical composition and temperature fluctuations paves the path of utilizing narrow emission lines for advanced sensing. The concept of random lasing is first explained followed by a comparison of the different lasing threshold that has been reported. This is followed by a survey of reports on laser-based sensing and more specifically as biosensors. Finally, a perspective on the way forward for open cavity laser-based sensing is put forth.

Effect of Controlled Microbial Fermentation on Nutritional and Functional Characteristics of Cowpea Bean Flours.

This study aimed to optimize bean flours fermentation through the use of appropriate technological procedure and, thereby, to obtain a high quality and safe product. In this line, cowpea bean flours with different moisture conditions (10, 20 and 30%) were incubated with (1) a single culture of Lactobacillus plantarum, or (2) a consortium of lactic acid and acetic acid bacteria, together with one strain of Saccharomyces cerevisiae. Effects of inoculation of cowpea beans flours on stability (i.e., evaluated by the decrease in pH), and variations in nutritional characteristics (i.e., protein, starch, water soluble carbohydrates, total dietary fibre) were investigated. In both fermented flours, the effect of fermentation was more noticeable in total water-soluble carbohydrate (WSC) concentration during the fermentation process (P < 0.001), accounted for by metabolic activity of the microorganisms. The pH values progressively decreased (P < 0.001) through the fermentation process, particularly in flours fermented with a single culture of L. plantarum. By contrast, titratable acidity increased (P < 0.001) throughout the fermentation process in F2 and F3, although more noticeable in F3. Total dietary fibre (TDF) was not variable over the time. In relation to the protein content, the fermentations behaved very similarly; F2 had a variation over the time, but the effect was not significant (P = 0.0690). Results revealed small changes in chemical composition except in the case of pH and sugar contents with the values lower in the fermented products (i.e., single- or mixed-culture fermentation), leading to a more stable and safety product. These results indicate that fermented dry beans flours have the potential as functional ingredients for new food formulations.

Superconducting Characteristics of REBCO Coated Conductors With Different Zr Content

In this paper, REBa 2 Cu 3 O 7-δ (RE = rare earth elements, REBCO) coated conductors with different content of self-assembled BaZrO 3 nanorods were grown by metal organic chemical vapor deposition using a roll-to-roll process. Small changes in chemical composition affecting Ba to Cu stoichiometry induce variation in REBCO c-axis lattice parameter and highly affect the self-field J c at 77 K, superconducting transition width (ΔT c ), and in-field performance of coated conductors. While the self-field J c at 77 K in 15 mol.% Zr-added REBCO film (5 MA cm -2 ) was about 28% higher than that in 25 mol.% Zr-added REBCO (3.9 MA cm -2 ), the in-field J c at 30 K, 3 T (B∥c) of the latter was found to be 36% higher than that of the former. The high J c values of 14.9 and 20.3 MA cm -2 at 30 K, 3 T (B∥c) were obtained in coated conductors with the c-axis lattice parameter of 11.74 and 11.76 A in 15 and 25 mol.% Zr-added REBCO films, respectively.

Mechanical and Corrosion Properties of Two Precipitation-Hardened Mg-Y-Nd-Gd-Dy Alloys with Small Changes in Chemical Composition

Precipitation hardening in Mg-Y-Nd alloys (WE-type) is based on finely dispersed particles offering an effective strengthening mechanism to achieve high strength at moderate ductility. However, these particles often affect corrosion by being more noble than the matrix. Biodegradable implant materials should show a corrosion rate fit to its application but should be free of pitting corrosion. Especially deep and narrow pits act as notches and cause increased mechanical stress leading into early failure. WE43 has already shown to have an acceptable biological response. In this study, two Mg-Y-Nd-Gd-Dy alloys, WE32 and WE33, in extruded, solution and precipitation heat-treated conditions have been investigated. The difference in alloy composition is not very high. Solution heat treatment (T4) causes grain growth and strength loss. The ageing response to peak hardness depends on the temperature. A rather short ageing response was observed for 250°C, and highest hardness has been found for 200°C at longer ageing time but higher hardness compared to 250°C. Grain growth during ageing is not significant. The higher alloyed alloy WE33 shows better mechanical strength, but less ductility. Corrosion was evaluated with immersion and potentiodynamic polarization in Ringer Acetate solution. The corrosion rate strongly depends on the alloy and heat-treatment condition as well as on the test method. The highest corrosion rate is observed in the solution-treated condition. The peak aged alloy shows the lowest corrosion rate, but non-uniform corrosion and has been evaluated by the pitting factor.

Probing the electronic structure of Ni–Mn–In–Si based Heusler alloys thin films using magneto-optical spectra in martensitic and austenitic phases

Thin films of Ni52Mn35−xIn11+xSi2 were fabricated by magnetron sputtering on MgO (001) single crystal substrates. Magnetization as function of temperature for Ni52Mn35In11Si2 exhibits features consistent with a magnetostructural transition (MST) from an austenitic phase to a martensitic phase, similar to the bulk material. We observed that the martensitic transformation is externally sensitive to small changes in chemical composition and stoichiometry. It has been found that thin films of Ni52Mn34−xIn11+xSi2 with x=0 and 1 undergo a temperature-induced MST or remain in a stable austenitic phase, respectively. Comparison of magneto-optical transverse Kerr effect spectra obtained at 0.5–4.0eV in the 35–300K temperature interval reveal insignificant differences between the martensitic and austenite phases. We found that the field and temperature dependencies of the transverse Kerr effect are quite different from the magnetization behavior, which is attributed to magnetic inhomogeneity across the films. To elucidate the effects of magnetostructural phase transitions on the electronic properties, we performed density functional calculations of the magneto-optical Kerr effect.

In-depth study of 16CygB using inversion techniques

The 16Cyg binary system hosts the solar-like Kepler targets with the most stringent observational constraints. Moreover, this system is particularly interesting since both stars are very similar in mass but the A component is orbited by a red dwarf, whereas the B component is orbited by a Jovian planet and thus could have formed a more complex planetary system. In our previous study, we showed that seismic inversions of integrated quantities could be used to constrain microscopic diffusion in the A component. In this study, we analyse the B component in the light of a more regularised inversion. We wish to analyse independently the B component of the 16Cyg binary system using the inversion of an indicator dedicated to analyse core conditions, denoted tu. Using this independent determination, we wish to analyse any differences between both stars due to the potential influence of planetary formation on stellar structure and/or their respective evolution. First, we recall the observational constraints for 16CygB and the method we used to generate reference stellar models. The inversion results were then used to analyse the differences between the A and B components. The tu indicator for 16CygB shows a disagreement with models including microscopic diffusion and sharing the chemical composition previously derived for 16CygA. Small changes in chemical composition are insufficient to solve the problem but that extra mixing can account for the differences seen between both stars. We use a parametric approach to analyse the impact of extra mixing in the form of turbulent diffusion on the behaviour of the tu values. We conclude on the necessity of further investigations using models with a physically motivated implementation of extra mixing including additional constraints to further improve the accuracy with which the fundamental parameters of this system are determined.

Corrosion Behaviour of Low-Alloyed Cast Steel in Diverse State

Abstract In the paper the results and analysis of corrosion tests were presented for low-alloyed cast steel in as-cast state and after heat treatment operations. Such alloys are applied for heavy loaded parts manufacturing, especially for mining industry. The corrosion test were performed in conditions of high salinity, similar to those occurring during the coal mining. The results have shown, that small changes in chemical composition and the heat treatment influence significantly the corrosion behaviour of studied low-alloyed cast steels.

The chemistry of TIG weld bead formation

TIG welding has high levels of stability and permits more refined control than the majority of other arc welding processes. However, it is well known that small changes in the chemical composition of the base metal and arc operating region can have a pronounced effect on the resulting weld bead shape, which reduces the ability to control and predict the process. Obviously, this reduces the reliability and controllability of TIG welding. This study reviews the variability of weld beads obtained in the TIG process, with small changes in chemical composition of the base metal, and A-TIG and TIG weldings with active gas. Aspects that are similar and unique to each case are highlighted and discussed. The mechanisms of weld bead shape presented in the literature are also presented and compared.

Photocrosslinked Co‐Networks from Glycidylmethacrylated Gelatin and Poly(ethylene glycol) Methacrylates

Biopolymer-based systems with adjustable macroscopic properties that can be varied in a wide range using only small changes in chemical composition are promising candidates for biomaterial-induced autoregeneration. Glycidylmethacrylated gelatin is photopolymerized with the addition of PEG mono- or dimethacrylate to form co-networks in pH = 7.4 PBS. The degree of swelling (Q) and water uptake (H) in PBS at 37 °C are tailorable for PEGDMA co-networks (Q ≈ 250-650 vol%), while the storage modulus of swollen networks at 3 °C can be adjusted by the PEG(D)MA content (G' = 0.7-145 kPa). Indirect cytotoxicity tests on ethylene oxide sterilized films show non-toxic responses for the homonetwork and all but one PEGDMA-containing co-networks materials.

Influence of Initial Water Content on the Wettability of Autoclaved Soils

Autoclaving is a commonly used practice to destroy microbial activity in soils but is thought to have a limited effect on other soil properties. Small changes in chemical composition have been reported, but there have been no previous reports of any alteration of physical properties. This study, however, showed that autoclaving can cause a major change in soil hydraulic properties. For samples with intermediate water contents (10–35% v/v), it caused severe or extreme water repellency in three of four soil types tested, although no effect for initially low or high water contents was found. These findings have important implications for any experimental work involving soil autoclaving as a pretreatment procedure but could also be used for generating otherwise similar samples differing only in terms of wettability.

Recycling of chemical pulp from wheat straw and corn stover

Handsheets produced from corn stalks and wheat straw soda AQ pulps were recycled in the lab. Pulping of corn stalks resulted in a low pulp yield, low bonding strength, and low recyclability. Conversely, wheat straw fiber had a better yield, very good tensile properties, and showed a considerably better response to recycling. The tensile index of wheat straw fibers retained 67% of its original value after four cycles. It could be shown that recycling caused only small changes in chemical compo-sition, but that the crystallinity index increased considerably. To be able to understand the behavior of wheat straw fiber as part of a commercial papermaking furnish, a paper containing 20% wheat straw fiber was produced on a 24 inch pilot paper machine and was recycled using a handsheet mold with white water return. Chemical analysis of the control (no wheat fiber) and the wheat-containing paper demonstrated slightly higher xylan content for the wheat-containing material. Recyclability increased slightly with addition of wheat fibers to a commercial furnish.

Small changes in the polymer structure influence the adsorption behavior of fibrinogen on polymer surfaces: validation of a new rapid screening technique.

Numerous studies conclude that the selective adsorption of plasma proteins on materials contacting blood or tissue affects all subsequent interactions related to the biocompatibility of artificial surfaces. However, there are only a few studies available, which clearly demonstrate that there is a correlation between surface chemistry and selective protein adsorption. Detailed knowledge of such correlations would facilitate the design of biocompatible materials. In this study, a rapid, fluorescence-based, screening technique using a 384-well format for polymer-protein interactions was developed. The screening assay was used to measure the adsorption of human fibrinogen on 46 test polymers (44 polyarylates selected from a combinatorial library of tyrosine-derived polyarylates, and two lactide-based polymers). In this library of polyarylates, structural changes are generated by variations in either the polymer backbone or the polymer pendent chain. Although no overall trend between polymer hydrophobicity and fibrinogen adsorption could be identified using the entire set of test polymers (R(2) = 0.43), fibrinogen adsorption was clearly correlated with variations in the pendent chain structure. Thus, when the test polymers were grouped by backbone composition, increased hydrophobicity of the pendent chain was significantly correlated with reduced fibrinogen adsorption. The following R(2) coefficients within the polymer backbone groups were determined: 0.87 (diglycolates); 0.98 (glutarates); 0.73 (adipates); 0.87 (suberates); 0.67 (3-methyl-adipates). Our results demonstrate that it is possible to screen for protein-material interactions in a cost-effective fashion using a miniaturized immunofluorescence technique. Further, we demonstrate that small changes in chemical composition can significantly influence the adsorption of human fibrinogen on polymer surfaces. The lactide-based polymers were among those polymers exhibiting the highest tendency to adsorb fibrinogen. This information may be useful when polymers have to be selected for specific biomaterial applications.

Surface analysis of contamination layers in cold-cathode gauges

The influence of gas atmosphere on the long-term operation characteristics of a commercial cold-cathode gauge was studied. The changes of the electrode surfaces due to contamination effects of the so-called double-plasma gauge CF 2P by ALCATEL (double Penning system) were investigated by Auger-electron spectroscopy, X-ray photoelectron spectroscopy and scanning electron spectroscopy. Contrary to the widespread opinion that particular contamination is mainly caused by the polymerization of hydrocarbons in the discharge chamber of cold-cathode gauges, we found a contamination layer on the electrodes which consists only of sputtered cathode material. The distribution and thickness of the layer can give information about the preferred ion trajectories and convenient design features for a long life and stable operation of this type of gauge. Layer thickness seems to be a direct function of the pressure dose, independent of small changes in chemical composition of the layers and independent of the pressure itself.

Study of innovative coatings for hot working tools

Thermal spraying processes have many advantages that help improve the performance and extend the life of materials and components. In the present paper the properties and wear behaviour of plain carbon specimenscoated with Ni or Co based alloy powders have been studied for the coating of tools employed in hot working applications, e.g. rolls in a rod mill plant. The morphologies of the different coating layers were very similar, showing the presence of porosity and inclusions, especially at the interface with the coated material, however their influence on the wear behaviour of the specimens was negligible. All the Ni based alloysshowed similar behaviour and satisfactory wear resistance, although small changes in chemical composition induced different hardnesses in the coating layers. The best wear resistance was observed with harder specimens. The Co based powder did not allow the formation of layers with hardnesses high enough to provide good wear resistance. When the Co based powder was mixed with a Ni based powder, the wear behaviour proved disappointing in applications involving rolling and sliding.

Effect of electron irradiation on the 3C-4H transformation in a Co-Fe alloy

In general, irradiation of materials by high energy electrons, protons or neutrons has been shown to stabilize the existing microstructure against subsequent martensitic transformation. Alloys which have been studied include the binary intermediate phases NiTi and Ni63Al37 and ternary phases between Cu37,5Al62.5 and CU63.6Al36.4 as well as the intermetallic Cu69.01Al17.92 Zn12.17. In these materials, the martensitic transformations are known to be sensitive to small changes in chemical composition and to the degree of long range order. In addition, one should expect the kinetics of martensitic transformations to be sensitive to other forms of structural damage introduced during irradiation also. This spectrum of irradiation-induced phenomena renders the interpretation of results in studies of such concentrated binary and ternary phases rather complicated, therefore.We present here the preliminary results of a study of the effect of electron irradiation on the character of the martensitic transformation in a relatively dilute terminal solid solution of Co+5.75 wt pet Fe, similar in composition to that employed for studies of the transformation mechanism itself.

Structure of calcium-aluminosilicate glasses: wide-angle X-ray scattering and principal component analysis

Two series of calcium aluminosilicate glasses and vitreous SiO2 have been studied by means of wide-angle X-ray scattering (WAXS). The alteration of the (CaO + Al2O3):SiO2 and (CaO + SiO2):Al2O3 ratios caused significant changes in the scattering function dependent intensity distributions (I(s)). Thus, it is shown that the WAXS method is sensitive to small changes in chemical composition of the samples which cause detectable changes of the structure of the glassy networks. Principal component analysis (PCA) was applied to the data set formed by 150 intensity values of each of the twelve scattering functions. As a result, (i) groups of ‘relative similar’ glasses and an ‘outlier’ could be detected; and (ii) relations between chemical composition and principal components were established. Thus, it was shown that the application of PCA may serve as a basis for the detailed interpretation to WAXS data of series of glassy samples.

Géochimie des éléments hygromagmatophiles, coefficients de partage minéraux /liquides et propriétés structurales de ces éléments dans les liquides magmatiques

The term hygromagmatophile element may be applied to those elements who maintain high stability in silicate liquid. They may be identified by (1) low crystal /liquid partition coefficient ; (2) high enrichment factors in a given differenciation series ; (3) linear correlations between the concentrations of pairs of such elements. We propose that the behaviour of hygromagmatophile elements is governed more by the formation of stabilizing complexes in the silicate liquids than by their rejection by the crystallizing solids. When expressed in terms of possible complexes, the activity of the trace element in the liquid becomes a function that may be sensitive to small changes in chemical composition and structural state. This would explain the range of behaviour of a given trace elements in different magmatic series (basaltic, calco-alkaline, alkaline, etc.). Moreover, recent structural studies of the liquid state give factual ground to our hypothesis.

Interrelations of compositions, transformation kinetics, morphology, and mechanical properties of alloy steels

The strong influence of the fine-scale microstructural features on mechanical properties has become increasingly evident during the past decade. This is particularly true for fracture toughness of quenched and tempered alloy steels. Large differences in microstructure can be produced by isothermal, rather than athermal, treatments in the bainite and upper martensite temperature ranges. The kinetics of transformation, as well as the kinds and volume fractions of transformation products can be varied o ver wide ranges by relatively small changes in chemical composition. The effects of the common alloying elements on transformation kinetics, both separately and in various combinations were determined experimentally. The synergistic effects of individual elements added as pairs of elements were not predictable from a knowledge of the effects of the individual elements. Isothermal treatments, coupled with variations in the kinds and amounts of alloying elements, produced different morphologies, compositions, and volume fractions of the transformation products. The effects of such microstructural differences on tensile properties, fracture toughness, and fatigue characteristics were evaluated. Beneficial effects were found, such as substantial increases in fracture toughness, with small changes in alloy content or with heat treatments that differed from those conventionally used.

A Statistical Method for the Analysis of Peppermint Oils and Other Complex Mixtures

SUMMARY— A statistical method, preferably operated by a a computer, is proposed for the analysis of data on complex mixtures where the information sought involves a number of small changes in chemical composition, each of which is individually within the normal range of variation of the mixtures. When the method is applied to the identification of geographical origins of peppermint oils and mixtures of peppermint oils, the results are a substantial improvement on those from previous methods, though still leaving some uncertainty. It is expected that more complete chemical analysis will greatly improve the confidence level.