Changes In Physical Structure Research Articles

Anomalous mechanosensitive ion transport in nanoparticle-blocked nanopores.

Living organisms can sense extracellular forces via mechanosensitive ion channels, which change their channel conformations in response to external pressure and regulate ion transport through the cell membrane. Such pressure-regulated ion transport is critical for various biological processes, such as cellular turgor control and hearing in mammals, but has yet to be achieved in artificial systems using similar mechanisms. In this work, we construct a nanoconfinement by reversibly blocking a single nanopore with a nanoparticle and report anomalous and ultra-mechanosensitive ionic transport across the resulting nanoconfinement upon assorted mechanical and electrical stimuli. Our observation reveals a suppressed ion conduction through the system as the applied pressure increases, which imitates certain behaviors of stretch-inactivated ion channels in biological systems. Moreover, pressure-induced ionic current rectification is also observed despite the high ionic concentration of the solution. Using a combined experimental and simulation study, we correlate both phenomena to pressure-induced nanoparticle rotation and the resulting physical structure change in the blocked nanopore. This work presents a mechanosensitive nano-confinement requiring minimal fabrication techniques and provides new opportunities for bio-inspired nanofluidic applications.

Pretreatment of sweet sorghum stalk with aqueous hydrogen peroxide for enhancing methanolysis and property of the bio-oil

Alcoholysis is a promising approach for converting biomass into fuels and/or chemicals under mild conditions. However, the effect of pretreatment on biomass alcoholysis was rarely reported. Herein, the effect of pretreatment with H2O2 on sweet sorghum stalk (SSS) methanolysis was examined. The results show that the pretreatment could markedly improve the bio-oil (BO) yield and decrease the appropriate temperature for obtaining maximum BO yield. The appropriate temperature for pretreated SSS methanolysis was determined to be 280 °C and the maximum BO yield is 44 wt%. In addition, higher heating values of the BOs were also enhanced based on elemental analysis. According to analysis with gas chromatograph/mass spectrometer, phenolic compounds, esters, and sugars are predominant in the BOs, and the yield of phenolic compounds significantly increased from 91.75 to 111.68 mg . g−1 by the pretreatment. Moreover, polar species in the BOs decreased and deoxygenation occurred during pretreated SSS methanolysis. Analyses with scanning electron microscope and N2 physisorption reveal that pretreated SSS has more grooves and higher specific surface area and anomalous porosity than SSS. According to analyses with Fourier transform infrared spectrometer and X-ray photoelectron spectrometer, oxygen functional groups mainly in the forms of CO and COO were introduced into SSS by the pretreatment. The changes of physical and chemical structures should be responsible for enhancing SSS methanolysis and property of the BO.

Exploring Strategies toward Synthetic Precision Control within Core-Shell Nanowires.

ConspectusAchieving precision and reproducibility in terms of physical structure and chemical composition within arbitrary nanoscale systems remains a "holy grail" challenge for nanochemistry. Because nanomaterials possess fundamentally distinctive size-dependent electronic, optical, and magnetic properties with wide-ranging applicability, the ability to produce homogeneous and monodisperse nanostructures with precise size and shape control, while maintaining a high degree of sample quality, purity, and crystallinity, remains a key synthetic objective. Moreover, it is anticipated that the methodologies developed to address this challenge ought to be reasonably simple, scalable, mild, nontoxic, high-yield, and cost-effective, while minimizing reagent use, reaction steps, byproduct generation, and energy consumption.The focus of this Account revolves around the study of various types of nanoscale one-dimensional core-shell motifs, prepared by our group. These offer a compact structural design, characterized by atom economy, to bring together two chemically distinctive (and potentially sharply contrasting) material systems into contact within the structural context of an extended, anisotropic configuration. Herein, we describe complementary strategies aimed at resolving the aforementioned concerns about precise structure and compositional control through the infusion of careful "quantification" and systematicity into customized, reasonably sustainable nanoscale synthetic protocols, developed by our group. Our multipronged approach involved the application of (a) electrodeposition, (b) electrospinning, (c) a combination of underpotential deposition and galvanic displacement reactions, and (d) microwave-assisted chemistry to diverse core-shell model systems, such as (i) carbon nanotube-SiO2 composites, (ii) SnO2/TiO2 motifs, (iii) ultrathin Pt-monolayer shell-coated alloyed metal core nanowires, and (iv) Cu@TiO2 nanowires, for applications spanning optoelectronics, photocatalysis, electrocatalysis, and thermal CO2 hydrogenation, respectively.In so doing, over the years, we have reported on a number of different characterization tools involving spectroscopy (e.g., extended X-ray absorption fine structure (EXAFS) spectroscopy) and microscopy (e.g., high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM)) for gaining valuable insights into the qualitative and quantitative nature of not only the inner core and outer shell themselves but also their intervening interface. While probing the functional catalytic behavior of a few of these core-shell structures under realistic operando conditions, using dynamic, in situ characterization techniques, we found that local and subtle changes in chemical composition and physical structure often occur during the reaction process itself. As such, nuanced differences in atomic packing, facet exposure, degree of derivatization, defect content, and/or extent of crystallinity can impact upon observed properties with tangible consequences for performance, mechanism, and durability.

Indirect Effects of Microplastic-Contaminated Soils on Adjacent Soil Layers: Vertical Changes in Soil Physical Structure and Water Flow

Previous microplastic research under laboratory conditions has focused on microplastics that are homogeneously mixed into test media, in order to maximize test reproducibility and uniform bio-accessibility. Here we specifically focused on testing the idea that microplastics in soil could affect adjacent soil layers not containing microplastic themselves. We included two different microplastics (low-density polyethylene films and polyacrylonitrile fibers) and carried out a soil column test consisting of three different vertical layers (0–3 cm, top, control soil; 3–6 cm, middle, microplastic-containing soil; 6–9 cm, bottom, control soil). Our study shows that microplastic-containing soil layers can act as an anthropogenic barrier in the soil column, interrupting the vertical water flow. These changes directly affected the water content of adjacent layers, and changes in the proportion of soil aggregate sizes occurred for each depth of the soil columns. We also observed that these physical changes trigger changes in soil respiration, but do not translate to effects on enzyme activities. These results imply that the soil environment in non-contaminated parts of the soil can be altered by microplastic contamination in adjacent layers, as might occur for example during ploughing on agricultural fields. More generally, our results highlight the need to further examine effects of microplastic in experiments that do not treat this kind of pollution as uniformly distributed.

Chromism of chemical compounds

Chromism, generally a reversible color change of substances, finds vital applications in the fields of switching, catalysis, molecule binding, drug delivery and energy storage applications. Chromism is caused by the change of electronic, conformational, crystal or physical structure of materials due to heat, light, solvent/vapour, applied electric potential, etc. There have been observed different types of chromism such as thermochromism, photochromism, solvetochromism, electrochromism and many others from different compounds. Here in we have discussed different types of chromisms but in brief as inherited by various types of materials. Reversible multicolor chromism by metal halide formamidinium perovskite attests solvetochromism and thermochromism due to the hydrogen bonding. Tetrathiazolylthiophene compound shows mechanochromism because of the structural deformation. Chain length of ligand influences the chromism in copper complex. Gold cluster complex, boron complex, Bi2WO6 also display specific chromic performance. Phosphomolybdate – malachite green dye moiety (PMMG) displays hydrochromism because of bridged water molecules. N2 (or O2) binding to PMMG has recently been shown as an extension of hydrochromism phenomonon. Thus, this account on chromism from various materials is expected to attract the attention of researchers.

Effect of Radiation with Wavelength of 313 nm on Changes in Physical Properties and Structure of Polymers

Effect of Radiation with Wavelength of 313 nm on Changes in Physical Properties and Structure of Polymers

Study on the pyrolysis characteristics and kinetic mechanism of cow manure under different leaching solvents pretreatment

Cow manure (CM) is a kind of biowaste with potential for heat recovery and energy. The effects of different leaching solvents on the physicochemical structure of CM and the catalysis role of AAEMs on the thermal behavior were studied. TGA experiments showed that the maximum weight loss rate and the peak temperature of hemicellulose and cellulose increased after leaching, while the TG/DTG curve moved to a high temperature direction. The devolatilization index (Di) value of the raw and leaching samples increased with the increase of the heating rate, indicating that the higher heating rate promoted the release of volatile. The treatment with leaching not only removed AAEMs in CM effectively, but also led to a larger specific surface area and pore volume, and reduced the crystallinity of cellulose and crystal size in CM. Na salt and K salt were mainly in water soluble state, while Ca salt and Mg salt were mainly in acid soluble salt. Compared with the change of physical and chemical structure caused by leaching, the removal of AAEMs played a dominant role in the pyrolysis characteristics of the samples. The removal efficiency of AAEMs increased with the strength of acid. Based on Kissinger model, the Eα of Raw-CM, H2O-CM, CH3COOH-CM, HCl-CM, HNO3-CM and H2SO4-CM is 171.30 kJ/mol, 187.58 kJ/mol, 190.86 kJ/mol, 292.10 kJ/mol, 287.79 kJ/mol and 280.69 kJ/mol respectively. Both the raw and leaching samples followed the reaction order mechanism and tended to react according to a higher-order reaction model between n = 1.5 and n = 4. In contrast, CH3COOH is an ideal solvent for leaching pretreatment.

Linking physical activity with knee osteoarthritis outcomes: an evidence map using the osteoarthritis initiative

Linking physical activity with knee osteoarthritis outcomes: an evidence map using the osteoarthritis initiative

From solid electrolyte to zinc cathode: vanadium substitution in ZnPS3

Development of next generation batteries is predicated on the design and discovery of new, functional materials. Divalent cations are promising options that go beyond the canonical Li-based systems, but the development of new materials for divalent ion batteries is hindered due to difficulties in promoting divalent ion conduction. We have developed a family of cathode materials based on the divalent cation conductor ZnPS3. Substitution of V for Zn in the lattice concomitant with vacancy introduction yields isostructural but redox-active materials that can reversibly store Zn2 + in the vacancies. A range of voltammetry and galvanostatic cycling experiments along with x-ray photoelectron spectroscopy support that redox is indeed centered on V and that capacity is dependent on the V content. The voltage of the materials is limited by the irreversible decomposition of the polyanion above 1.4 V vs. Zn/Zn2 + . The reversible capacity before anion decomposition is limited to half the vacancies and is due to the relative ratios of oxidized and reduced V centers. Such observations provide useful design rules for cathode materials for divalent cation based battery technologies, and highlight the necessity for a holistic interpretation of physical and electronic structural changes upon cycling.

Low density polyethylene degradation by filamentous fungi.

Polyethylene (PE) is the most abundant non-degradable plastic waste, posing a constant and serious threat to the whole ecosystem. In the present study, the fungal community of plastic wastes contaminating a landfill soil has been studied. After 6 months of enrichment, 95 fungi were isolated, mostly belonging to the Ascomycota phylum. They were screened under invitro condition: most of fungi (97%) were capable of growing in the presence of PE powder (5-10gL-1) as sole carbon source. Fusarium strains better tolerated high concentration of PE. Up to 13 strains were chosen for further degradation trails, where the process was monitored by respirometry tests and by observing changes in PE chemical and physical structure by FTIR analysis and SEM images. Major results were observed for Fusarium oxysporum, Fusarium falciforme and Purpureocillum lilacinum, as they caused strong oxidation phenomena and changes in the PE film morphology. Results suggested that the initial oxidation mechanisms targeted first the methyl terminal groups. Changes in the infrared spectra were strongly strain-dependent, denoting the activation of different degradation pathways. Through the SEM analysis, the actual damages provoked by fungi were observed, including swellings, pits and furrows, bumps and partial exfoliations. Considering the rising concern about plastic disposal worldwide, the ability of these fungi to colonize PE and utilize it as carbon source is of great interest, as no pretreatments and pro-oxidant stimulants were needed.

The effects of long-term supercritical CO2 exposure on Zululand Basin core samples

Carbon dioxide (CO2) sequestration in geological formations is a viable solution for ensuring coal-based energy supply whilst reducing CO2 emissions. The variation in the microstructure and composition of geological formations before and after CO2 storage plays a significant role in CO2 sequestration. Three core samples obtained from the Zululand Basin in South Africa were exposed to supercritical CO2 (ScCO2) in the presence of water under typical hydrothermal conditions (175 bar, 70 °C) for up to 2 months. The samples were characterized pre- and post-treatment using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), low pressure nitrogen (N2) adsorption and low pressure CO2 adsorption. Physical and chemical structural changes were observed in all three samples after treatment, to varying degrees. Mineral alterations were observed in the three samples, including plagioclase and calcite dissolution/precipitation and quartz composition changes. Dissolution of organic components and surface chemistry alterations were found in two of the core samples. Increases in pore volume, surface area and CO2 adsorption capacity were observed in all studied samples after CO2 treatment.

Au-decorated ZnO nanorod arrays for SERS-active substrates towards trace detection and classification of pentaerythritol tetranitrate

This work proposed a systematic fabrication process towards high-performance SERS-active substrates as the chemical sensors, based on a combination of the hydrothermal-synthesized ZnO nanorods (ZnO NRs) and the decorated Au nano-surface. The fabrication process was first focused on the preparation of the Au/ZnO NRs hybrids. The ZnO NR templates were grown on silicon (100) wafer substrates by the hydrothermal method. Then, the Au films were deposited on the ZnO NR templates by the DC pulse magnetron sputtering technique. The obtained SERS substrates were utilized towards trace detection and classifications of pentaerythritol tetranitrate (PETN), which is commonly used in industrial explosives and improvised explosive devices. The results from field-emission electron microscopy (FE-SEM) and transmission electron microscopy (TEM) indicated the changes in physical morphologies and crystal structure, respectively, based on the variation of the fabrication parameters. The FE-SEM results showed that well-vertical ZnO NRs demonstrated the length of the nanorods before and after the Au decorations. In addition, the hexagonal structures, before and after the Au decorations, were observed with the average diameter of 50 and 181 nm, the nanorod distances of 178 and 81 nm, respectively. The TEM results also confirmed the average size and d-spacing of the ZnO NRs and Au/ZnO NR hybrids, with validated elements/compounds from the EDX mapping technique. Furthermore, the sample surfaces were observed with Raman mapping spectroscopy towards uniformly distributed examination. Finally, the fabricated samples were investigated with trace concentration of PETN towards the limit of detection. The results that our SERS substrates could detect PETN of less than 1 µg/ml, which indicated excellent performance of the trace detection of the explosive substance. The SERS substrates were further used to successfully classify different sources of the PETN substances, with 10 mg/ml, based on the machine learning approach with the principal component analysis.

Effect of Physical Structures of Food Matrices on Heat Resistance of Enterococcus faecium NRRL-2356 in Wheat Kernels, Flour and Dough.

Nonpathogenic surrogate microorganisms, with a similar or slightly higher thermal resistance of the target pathogens, are usually recommended for validating practical pasteurization processes. The aim of this study was to explore a surrogate microorganism in wheat products by comparing the thermal resistance of three common bacteria in wheat kernels and flour. The most heat-resistant Enterococcus faecium NRRL-2356 rather than Salmonella cocktail and Escherichia coli ATCC 25922 was determined when heating at different temperature–time combinations at a fixed heating rate of 5 °C/min in a heating block system. The most heat-resistant pathogen was selected to investigate the influences of physical structures of food matrices. The results indicated that the heat resistance of E. faecium was influenced by physical structures of food matrices and reduced at wheat kernel structural conditions. The inactivation of E. faecium was better fitted in the Weibull distribution model for wheat dough structural conditions while in first-order kinetics for wheat kernel and flour structural conditions due to the changes of physical structures during heating. A better pasteurization effect could be achieved in wheat kernel structure in this study, which may provide technical support for thermal inactivation of pathogens in wheat-based food processing.

Physicochemical Comparison of Chitin Extracted from Horseshoe Crab (Limulus polyphemus) Exoskeleton and Exuviae

AbstractIn this paper, horseshoe crab exoskeleton and exuviae were collected on the coasts of Yucatan and physicochemical studies were carried out. Samples from different sections of the exoskeleton were taken to evaluate chitin content and properties in order to be compared with exuviae. The isolation of chitin was realized by chemical processes involving deproteinization, demineralization and discoloration. Physicochemical properties of chitin extracted from both sources were compared in terms of characterization analysis in particular achieved under EDX, FTIR and calorimetric techniques (DSC and TGA). In such comparative analysis lies the importance to establish differences or similitudes in chitin contents, structure, etc. Scanning Electron Microcopy was conducted on exuviae and exoskeleton selected parts in order to identify horseshoe crab structure and surface morphology. Differential scanning calorimetry was focused on changes in physical and chemical structures at different samples showing two endothermic peaks related to the complete elimination of hydroxyl groups attached to polysaccharide rings. TGA thermograms were characterized by endo and exotherms corresponding to water evaporation and decomposition of polymer respectively. Exoskeleton SEM images shown a tubular network and porous surface while exuviae exhibited irregular surface and diatom unicellular microalgae embedded. Calorimetric measurements confirmed that exuviae is richer in chitin than exoskeleton and that the main allotropic crystal structure corresponds to α‐chitin. FTIR analysis supported these results by exhibiting different absorption bands corresponding to α‐chitin.

Influence of Gamma Radiation Treatment on the Mechanical Properties of Sisal Fibers to Use into Composite Materials

The use of treatments in natural fibers is largely used, because it can improve the interfacial adhesion of polymer composites. However, the choice of the most appropriate treatment should take into account environmental factors, due to the need of new materials to meet requirements related to the concept of sustainability. This article investigated the influence of the mercerization, acetylation and gamma radiation treatments on the mechanical properties of sisal fibers, to use in composite materials. Experimental conditions were defined with different concentrations of reagents and radiation doses in order to understand the impact of these reactions on the tensile properties of sisal fibers. Thermal gravimetric analysis (TGA) and Fourier Transform Infrared (FTIR) spectroscopy were used to investigate the fiber degradation process and the chemical modifications after the treatments. The use of mercerization (0.1 M and 1.0 M NaOH concentrations) combined with acetylation increased the hydrophobic character of the sisal fiber, which may improve its interaction with polymeric matrices. In addition, mercerized sisal fiber at 0.5 M NaOH concentration, exposed to 25 kGy gamma radiation dose, showed physical and chemical structural changes that positively influence the fiber-matrix adhesion in polymer composite materials. All treatments made can reduce the natural tensile properties of the sisal fibers, because they can remove fundamental components to the structure and the stiffening of these fibers. Considering changes in the mechanical behavior, the use of gamma radiation presented similar results of the traditional chemical treatments, being less aggressive to the fibers and not causing the same negative impact on the environment.

Rheological Study of Phenol Formaldehyde Resole Resin Synthesized for Laminate Application.

Heat explosions are sometimes observed during the synthesis of phenol formaldehyde (PF) resin. This scenario can be attributed to the high latent heat that was released and not dissipated leading to the occurrence of a runaway reaction. The synthesis temperature and time played important roles in controlling the heat release, hence preventing the resin from hardening during the synthesis process. This study aims to assess the rheological and viscoelasticity behaviors of the PF resin prepared using paraformaldehyde. The prepared PF resin was designed for laminate applications. The rheological behavior of the PF resin was assessed based on the different molar ratios of phenol to paraformaldehyde (P:F) mixed in the formulation. The molar ratios were set at 1.00:1.25, 1.00:1.50 and 1.00:1.75 of P to F, respectively. The rheological study was focused at specific synthesis temperatures, namely 40, 60, 80 and 100 °C. The synthesis time was observed for 240 min; changes in physical structure and viscosity of the PF resins were noted. It was observed that the viscosity values of the PF resins prepared were directly proportional to the synthesis temperature and the formaldehyde content. The PF resin also exhibited shear thickening behavior for all samples synthesized at 60 °C and above. For all PF resin samples synthesized at 60 °C and above, their viscoelasticity results indicated that the storage modulus (G′), loss modulus(G″) and tan δ are proportionally dependent on both the synthesis temperature and the formaldehyde content. Heat explosions were observed during the synthesis of PF resin at the synthesis temperature of 100 °C. This scenario can lead to possible runaway reaction which can also compromise the safety of the operators.

Physical Properties and Structural Changes of Myofibrillar Protein Gels Prepared with Basil Seed Gum at Different Salt Levels and Application to Sausages.

The objective of this study was to evaluate physical properties and structural changes of myofibrillar protein gels with basil seed gum (BSG) at different salt levels and develop the low-salt sausages with BSG. Myofibrillar protein (MP) gels were prepared with or without BSG at different salt concentrations (0.15, 0.30, and 0.45 M). Cooking yield (CY, %), gel strength (GS, gf), viscosity, sulfhydryl contents, protein surface hydrophobicity, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) of MP were measured. Pork sausages were manufactured with 1% BSG at both low-salt (1.0%) and regular-salt (1.5%) levels. pH, color, expressible moisture (EM, %), CY, textural profile analyses, FTIR, sulfhydryl group, and protein surface hydrophobicity (μg) were measured for analyzing the properties of sausages. The addition of 1% BSG to MP gels increased CY and shear stress. Among treatments with different salt concentrations, MP at 0.30 M salt level with 1% BSG had higher GS than that at 0.15 M salt level with BSG. In microstructure, swollen structures were shown in MP gels with BSG. Although CY of sausage at the low-salt concentration (1.0%) decreased, regardless of the BSG addition, hardness values of sausages with regular-salt level increased with the addition of 1% BSG was added. Protein surface hydrophobicity and sulfhydryl contents of sausages increased with the addition of 1% BSG, resulting in higher hardness and lower springiness than those without BSG. These results suggest that BSG could be used as a water-binding and gelling agent in processed meats.

Using mechanical activation of quartz to enhance the compressive strength of metakaolin based geopolymers

The present work synthesized geopolymer with quartz mechanical activated at different time, and the strengthening mechanism of geopolymer by activated quartz was investigated. The changes of quartz before and after activation and the microstructure of geopolymer was explained by the determinations of particle size, specific surface area and the concentration of reactive Si, as well as XRD, XPS and NMR measurement. With the activation time of quartz increasing from 0 to 60 min, the compressive strength of geopolymer increased from 31.5 to 55.2 MPa. The results showed that increase of quartz reactivity is mainly due to the formation of the Si-centered radicals and non-bridging oxygen on the surface rather than the changes in physical property or crystal structure of quartz. The high activity tetrahedra Si with non-bridge oxygen on the surface of quartz replace the tetrahedra Al in geopolymer gel, which lead to a Si-rich gel formed around quartz and the improvement of compressive strength.

Effect of cellulose structure on reactivity of eucalyptus acid sulphite dissolving pulp

Three industrial Eucalyptus globulus acid sulphite dissolving pulps of different intrinsic viscosity (ca. 490–570 cm3/g) with similar xylan content (2.4–3.0%) were partially (ca. 60%) converted to cellulose II by treatment with 12% NaOH and hornified by drying for 8 h at 105 °C to induce changes in physical structure. All three initial and modified pulps were analysed on their Fock reactivity method and Chinese filterability. These dissolving pulps were also examined for the crystallinity degree and the crystallite dimensions assessed by wide-angle X-ray scattering and the fibril aggregation assessed by solid-state 13C nuclear magnetic resonance. The results showed that the reactivity of the dissolving pulp was negatively correlated with the degree of cellulose crystallinity and depended almost linearly on the lateral dimension of the fibril and the dimensions of the fibril aggregates. In hornified pulps, the effect of cellulose physical structure on reactivity was even more pronounced than the intrinsic viscosity of the dissolving pulp. In addition, no unambiguous dependence between the reactivity and the filterability of dissolving pulps was found. Filterability did not correlate clearly with lateral dimension of fibril or fibril aggregates, but depended only on pulp viscosity.

Platform for quantitative multiscale imaging of tissue composition.

Changes in the multi-level physical structure of biological features going from cellular to tissue level composition is a key factor in many major diseases. However, we are only beginning to understand the role of these structural changes because there are few dedicated multiscale imaging platforms with sensitivity at both the cellular and macrostructural spatial scale. A single platform reduces bias and complications from multiple sample preparation methods and can ease image registration. In order to address these needs, we have developed a multiscale imaging system using a range of imaging modalities sensitive to tissue composition: Ultrasound, Second Harmonic Generation Microscopy, Multiphoton Microscopy, Optical Coherence Tomography, and Enhanced Backscattering. This paper details the system design, the calibration for each modality, and a demonstration experiment imaging a rabbit eye.