Chloroform alters interleaflet coupling in lipid bilayers: an entropic mechanism

The interaction of the two leaflets of the plasmatic cell membrane is conjectured to play an important role in many cell processes. Experimental and computational studies have investigated the mechanisms that modulate the interaction between the two membrane leaflets. Here, by means of coarse-grained molecular dynamics simulations, we show that the addition of a small and polar compound such as chloroform alters interleaflet coupling by promoting domain registration. This is interpreted in terms of an entropic gain that would favour frequent chloroform commuting between the two leaflets. The implication of this effect is discussed in relation to the general anaesthetic action.     

New insights into sono-exfoliation mechanisms of graphite: In situ high-speed imaging studies and acoustic measurements

The application of ultrasound and acoustic cavitation in liquid exfoliation of bulk layered materials is a widely used method. However, despite extensive research, the fundamental mechanisms remain far from being fully understood. A number of theories have been proposed to interpret the interactions between cavitation and bulk layered materials and hence to explain the mechanisms of ultrasound assisted exfoliation. Unfortunately, most of the research reported to date is ambiguous or inconclusive due to lack of direct real-time experimental evidence. In this paper, we report systematic work characterising cavitation emissions and observing the exfoliation of graphite in situ, in deionised water under the dynamic interaction with laser and ultrasound induced cavitation bubbles. Using ultra-high-speed optical imaging, we were able to determine the dynamic sequence of graphite exfoliation events on a time scale never reported before. Real-time observations also revealed that shock waves with a pressure magnitude up to 5 MPa and liquid-jets in the range of 80 ms⁻¹, from transient cavitation bubble implosions, were essential for the initiation and propagation of the exfoliation process. On the other hand, bubble oscillations associated with stable cavitation were beneficial for promoting a gentler delamination of graphite layers.     

精加工零件尺寸视觉检测中的亚像素定位分析

使用CCD成像的机器视觉系统进行精加工零件尺寸检测时,图像轮廓边缘的亚像素定位分析是决定测量精度的一个重要因素．为了寻求精加工零件图像轮廓边缘的亚像素定位分析依据和计算方法,运用菲涅耳直边衍射理论研究了几何边缘在CCD检测图像中由衍射所形成的灰度分布,理论分析和实验测量都证实了衍射和摄像参数是产生和影响图像边缘灰度分布的主要因素．文中给出了基于衍射的精加工尺寸边缘图像检测时的亚像素定位分析依据和计算方法,对量块进行了对比检测实验,实验结果证实了所给方法的合理性和可行性．     

Treatment of misorientation data to determine the fraction of recrystallized grains in a partially recrystallized metal

A method has been developed to differentiate recrystallized from unrecrystallized grains in partially annealed samples based on the point-to-point misorientation within the grains. Recrystallized grains exhibit a low average point-to-point misorientation whereas the contrary is the case for deformed grains. The analysis for recrystallized fraction was calibrated based on this distinguishing feature, and it was found that the average point-to-point misorientation within a grain in a fully recrystallized sample was less than 0.7°. Based on this calibration, partially recrystallized samples were analysed for their degree of recrystallization, and the technique was validated using microhardness measurements. The analysis of the misorientation data was in excellent agreement with the hardness data. There are three factors which distinguish the current method in comparison to the earlier work: a fixed limit is maintained on the minimum number of pixels which may constitute a grain; pattern quality is not considered; and the recrystallization criterion is calibrated to the experimental data. Nevertheless, in the early stages of annealing, where recovery is likely to have the most influence on the drop in hardness, the analysis of electron backscattered diffraction (EBSD) data underpredicts the recrystallized fraction. The analysis was also conducted on a cold-rolled, nonannealed sample, and from this, the error of the technique is estimated to be a maximum of 0.06 recrystallized volume fraction.     

Systems toxicology used in nanotoxicology: mechanistic insights into the hepatotoxicity of nano-copper particles from toxicogenomics

In some studies, nano-copper particles have been found to be acutely toxic to exposed mice, with the liver and kidney being the target tissues. However, the characteristics of subacute toxicity from repeated nano-copper exposure in rats and the molecular mechanism of its hepatotoxicity at the genomic level remain unclear. We investigated the mechanisms of nano-copper-induced hepatotoxicity, which were identified from hepatic gene expression profiles that were phenotypically anchored to conventional toxicological outcomes, and identified biomarkers of nanotoxicity caused by nano-copper. Male Wistar rats were administered nano-copper or micro-copper at different doses for five days. Subsequently, we examined conventional toxicological parameters including body weight, clinical chemistry, and histopathology, and also used microarrays to identify gene expression changes in rat liver. High dose nano-copper induced increases in alanine aminotransferase, aspartate aminotransferase, triglyceride, total bilirubin, total bile acid levels, and a decrease in body weight. Histopathological studies of the liver indicated scattered, dotted hepatocytic necrosis in all rats in the high dose nano-copper group. Identified genes from the group receiving the high dose were functionally categorized, and results showed that genes related to oxidoreductase activity, metabolism, and signal transduction were involved in the development of the observed phenotypes. The results also suggest that altered gene expression patterns induced by exposure to a low, subtoxic dose of nano-copper may reveal signs of cell stress or subtle cell injury indicative of overt toxicity at higher doses. Results in this study provide new insights into the toxicology of nano-copper particles and illustrate how toxicogenomic approaches are providing an unprecedented amount of mechanistic information on molecular responses to nano-copper, as well as how they are likely to impact hazard and risk assessment. Gene expression changes are likely to be more sensitive indicators of potential adverse effects than traditional measurements of toxicity.     

Critical insights into the reinforcement potential of cellulose nanocrystals in polymer nanocomposites

Cellulose nanocrystals (CNCs) are highly polar, negatively-charged hydrophilic nanoparticles extracted from biomass through acid hydrolysis. They have high crystallinity and stiffness, as well as exceptional capability in reinforcing some polymer nanocomposites. While these remarkable improvements are limited to a certain class of polymers under strict conditions, CNCs can contribute to improving nanocomposite performance via other means, such as nucleating effect or cross-linking capacity. In this review, we offer critical insights into the reinforcing mechanism(s) of CNC-polymer nanocomposites and the factors that influence their performance. We aim to provide answers to the following questions: (1) how do CNCs contribute to nanocomposite reinforcement via percolation theory; (2) how to form a percolated CNC network in a CNC-polymer nanocomposite; (3) what are the factors affecting CNC performance and how do they work; and (4) how can we take advantage of CNC’s attributes to create high-performance nanocomposites?     

Multi-scale modelling of the dynamics of cell colonies: insights into cell-adhesion forces and cancer invasion from in silico simulations

Studying the biophysical interactions between cells is crucial to understanding how normal tissue develops, how it is structured and also when malfunctions occur. Traditional experiments try to infer events at the tissue level after observing the behaviour of and interactions between individual cells. This approach assumes that cells behave in the same biophysical manner in isolated experiments as they do within colonies and tissues. In this paper, we develop a multi-scale multi-compartment mathematical model that accounts for the principal biophysical interactions and adhesion pathways not only at a cell–cell level but also at the level of cell colonies (in contrast to the traditional approach). Our results suggest that adhesion/separation forces between cells may be lower in cell colonies than traditional isolated single-cell experiments infer. As a consequence, isolated single-cell experiments may be insufficient to deduce important biological processes such as single-cell invasion after detachment from a solid tumour. The simulations further show that kinetic rates and cell biophysical characteristics such as pressure-related cell-cycle arrest have a major influence on cell colony patterns and can allow for the development of protrusive cellular structures as seen in invasive cancer cell lines independent of expression levels of pro-invasion molecules.     

New insights into the in-process densification mechanism of cold spray Al coatings: Low deposition efficiency induced densification

This work details new insights into the in-process densification mechanism of cold spray Al coatings. The results show a trend counter to common observations: coating plastic deformation levels and coating density decreases with an increase in particle impact velocity. A lower particle impact velocity and the consequent lower deposition efficiency (DE) results in greater tamping energy per unit volume of deposit, which is the primary reason for the observed trend. This is the first time that DE has been shown to have a non-linear impact on the density of a cold spray coating, with particle in-process tamping being the primary mechanism for coating densification.     

Insights into the dissolution mechanisms of detergent agglomerates: An approach to assess dissolution heterogeneity

In this work, the dissolution mechanisms of detergent agglomerates with different binders were investigated in aqueous solution. The dissolution processes of detergent agglomerates were online monitored by using in situ UV–VIS spectrophotometer and electric conductivity probe. Dissolution profiles were correlated by Weibull model to evaluate the time-dependent dissolution rate coefficient and to classify the type of dissolution rate function k_t(t). The Kullback-Leibler information distance d_K-L was proposed to assess the degree of dissolution heterogeneity. The results indicate that the sodium linear alkylbenzene sulfonates (NaLAS) and sodium carbonates (Na₂CO₃) in detergent agglomerates have different dissolution behaviors, and their dissolution rates are influenced by the type and content of binders. Moreover, detergent agglomerates using semi-solid NaLAS paste or liquid linear alkylbenzene sulfonic acid (HLAS) as binders in granulation processes follow different dissolution mechanisms in water.     

Culturomics meets random fractal theory: insights into long-range correlations of social and natural phenomena over the past two centuries

Culturomics was recently introduced as the application of high-throughput data collection and analysis to the study of human culture. Here, we make use of these data by investigating fluctuations in yearly usage frequencies of specific words that describe social and natural phenomena, as derived from books that were published over the course of the past two centuries. We show that the determination of the Hurst parameter by means of fractal analysis provides fundamental insights into the nature of long-range correlations contained in the culturomic trajectories, and by doing so offers new interpretations as to what might be the main driving forces behind the examined phenomena. Quite remarkably, we find that social and natural phenomena are governed by fundamentally different processes. While natural phenomena have properties that are typical for processes with persistent long-range correlations, social phenomena are better described as non-stationary, on–off intermittent or Lévy walk processes.     

Practice issues for integrating strategic social assessment into the setting of environmental limits: insights from Canterbury,New Zealand

Abstract

There is mounting concern in New Zealand and worldwide about the impacts of current and projected land-use activities on freshwater quality. In 2011, the New Zealand government effected the National Policy Statement for Freshwater Management, requiring all regional councils to establish freshwater nutrient loads and water allocation measures in their land and water regional plans. These ‘limits’ must achieve locally defined social, economic and cultural outcomes while, as a minimum, halting any decline in water quality. The authors have participated in the Canterbury region’s strategic land and water planning activities. This has involved strategically assessing the social impacts of ‘limit options’ on aspects of catchment life and then integrating them into official reports and community deliberations, which ultimately inform the development of rules for catchment land use. This paper highlights practice issues which were confronted in the process and how they were managed.     

HS‐AFM and SERS Analysis of Murine Norovirus Infection: Involvement of the Lipid Rafts

Studies on human norovirus are severely hampered by the absence of a cell culture system until the discovery of murine norovirus (MNV). The cell membrane domains called lipid rafts have been defined as a port of entry for viruses. This study is conducted to investigate murine norovirus binding on the mouse leukemic monocyte macrophage cell line. Lipid raft related structures are extracted from cells by detergent treatment resulting detergent‐resistant membrane (DRMs) domains. The real‐time polymerase chain reaction technique is performed to detect the viral genome, thereby the MNV binding on the DRMs. The interactions between MNV and DRMs are investigated by high‐speed atomic force microscopy (HS‐AFM) combined with surface‐enhanced Raman spectroscopy (SERS). The inoculation of the virus onto cells results in the aggregations of detergent‐resistant membrane domains significantly. The characteristic Raman band of MNV is found in inoculated samples. To be sure that these results are originated from specific interactions between DRM and MNV, methyl‐β‐cyclo‐dextrin (MβCD) is applied to disrupt lipid rafts. The MNV binding on DRMs is precluded by the MβCD treatment. The cholesterols chains are defined as a key factor in the interactions between norovirus and DRMs. The authors conclude that the MNV binding involves the presence of DRMs and cholesterol dependent.     

New thoughts into the fabrication of ZnO nanoparticles: confined growth in the channels of AAO membrane and its formation mechanisms

Nanoparticles possess improved properties which are supported by the specific characteristics such as size, distribution and morphology. The synthesis of zinc oxide nanoparticles (ZnO-NPs) has attracted a great deal of attention for their wide and advanced applications. Confined growth of ZnO-NPs in the channels has been more superior for it offers finer tailoring of size and shape based on the pore size of anodic aluminum oxide (AAO) membrane. In our research, we have conducted a comparative study of the synthesis of ZnO-NPs through three different methods with the template synthesis of AAO membrane. The results indicate that the electrochemical deposition is preferable to the other two for it gives a narrow and dense distribution of ZnO-NPs. The growth processes and mechanisms of these various methods have also been summarized thoroughly. This work may provide us with some new thoughts into the fabrication of NPs and give us a blueprint to “design” materials.     

Photocatalytic properties of BiVO4 prepared by the co-precipitation method: Degradation of rhodamine B and possible reaction mechanisms under visible irradiation

Bismuth vanadate (BiVO₄) was synthesized by the co-precipitation method at 200 °C. The photocatalytic activity of the oxide was tested for the photodegradation of rhodamine B under visible light irradiation. The analysis of the total organic carbon showed that the mineralization of rhodamine B over a BiVO₄ photocatalyst (∼40% after 100 h of irradiation) is feasible. In the same way, a gas chromatography analysis coupled with mass spectroscopy revealed the existence of organic intermediates during the photodegradation process such as ethylbenzene, o-xylene, m-xylene, and phthalic anhydride. The modification of variables such as dispersion pH, amount of dissolved O₂, and irradiation source was studied in order to know the details about the photodegradation mechanism.     

A Facile Method to Coat Nanoparticles with Lipid Bilayer Membrane: Hybrid Silica Nanoparticles Disguised as Biomembrane Vesicles by Particle Penetration of Concentrated Lipid Layers

Natural membrane vesicles, including extracellular vesicles and enveloped viruses, participate in various events in vivo. To study and manipulate these events, biomembrane-coated nanoparticles inspired by natural membrane vesicles are developed. Herein, an efficient method is presented to prepare organic–inorganic hybrid materials in high yields that can accommodate various lipid compositions and particle sizes. To demonstrate this method, silica nanoparticles are passed through concentrated lipid layers prepared using density gradient centrifugation, followed by purification, to obtain lipid membrane-coated nanoparticles. Various lipids, including neutral, anionic, and cationic lipids, are used to prepare concentrated lipid layers. Single-particle analysis by imaging flow cytometry determines that silica nanoparticles are uniformly coated with a single lipid bilayer. Moreover, cellular uptake of silica nanoparticles is enhanced when covered with a lipid membrane containing cationic lipids. Finally, cell-free protein expression is applied to embed a membrane protein, namely the Spike protein of severe acute respiratory syndrome coronavirus 2, into the coating of the nanoparticles, with the correct orientation. Therefore, this method can be used to develop organic–inorganic hybrid nanomaterials with an inorganic core and a virus-like coating, serving as carriers for targeted delivery of cargos such as proteins, DNA, and drugs.     

Electrochemical lithium insertion behavior of FeNbO4: Structural relations and in situ conversion into FeNb2O6 during carbon coating

Electrochemical properties of FeNbO₄ as a lithium insertion anode material were studied with a view to understand structure–property relationships. Orthorhombic and monoclinic polymorphs of FeNbO₄ were synthesized and characterized by powder X-ray diffraction and laser Raman spectroscopy. Possible redox reactions, as deciphered from cyclic voltammograms, suggest the structural similarity between orthorhombic and monoclinic polymorphs upon lithium insertion. A coating of carbon led to a remarkable improvement in the electrochemical performance of monoclinic FeNbO₄. The coated material exhibited an average reversible capacity of 125.5 mAh g⁻¹. The material also sustained hundreds of charge/discharge cycles and exhibited good rate capability. Upon coating with carbon, the monoclinic FeNbO₄ transformed into FeNb₂O₆. The conversion and stability were confirmed by powder XRD and laser Raman studies of carbon-coated material before and after 450 cycles. The in situ conversion of FeNbO₄ into FeNb₂O₆ during carbon coating was further supported by EPR studies in which the absence of signal for the carbon-coated material indicated conversion of Fe³⁺ to Fe²⁺. Our study reveals the possibility of exploring potential materials in the Fe–Nb–O system and enhancing their performance as anode materials for lithium-ion batteries.     

Phase analysis and dielectric properties of ceramics in PbO-MgO-ZnO-Nb2O5 system: A comparative study of materials obtained by ceramic and molten salt synthesis routes

Compositions of the type 3PbO-MgO/ZnO-Nb₂O₅ were synthesized by the ceramic route at 1000°C and sintered at 1200°C. Powder X-ray diffraction studies of the 1000°C heated products show the presence of the cubic pyrochlore and the columbite (Mg/ZnNb₂O₆) type phase in the ratio of 3 : 1 for all possible combinations of MgO and ZnO. Further heating at 1200°C led to a decrease in the cubic pyrochlore phase and an increase in the columbite phase by around 10%. Compacted pellets sintered further showed the appearance of the perovskite phase. Similar compositions synthesized using the KCl-NaCl molten salt method at 900°C for 6 h gave a significant amount of the cubic perovskite related phase of the type Pb(Mg/Zn)_1/3Nb_2/3O₃ for all compositions containing MgO. The amount of the perovskite phase was nearly 55% for the Mg rich compositions and decreased with increase in Zn content, the pure Zn composition yielding mainly the cubic pyrochlore phase. On sintering these phases at 1000°C the perovskite phase content decreased. The dielectric constant of the composite materials formed by the ceramic route was in the region of 14 to 20 and varied little with frequency. The composites obtained by the molten salt method, however, showed much larger dielectric constants in the region 40–150 at 500 kHz for various compositions. The dielectric loss tangent of these composites were lower by an order (0.005–0.03 at 500 kHz) compared to the ceramic route.