Stability of clay particle-coated microbubbles in alkanes against dissolution induced by heating

We investigated the dissolution and morphological dynamics of air bubbles in alkanes stabilized by fluorinated colloidal clay particles when subjected to temperature changes. A quasi-steady model for bubble dissolution with time-dependent temperature reveals that increasing the temperature enhances the bubble dissolution rate in alkanes, opposite to the behavior in water, due to the differing trends in gas solubility. Experimental results for uncoated air bubbles in decane and hexadecane confirm this prediction. Clay-coated bubbles in decane and hexadecane are shown to be stable in air-saturated oil at constant temperature, where dissolution is driven mainly by the Laplace pressure. When the temperature increases from ambient, the particle-coated bubbles are prone to dissolution as the oil phase becomes under-saturated. The interfacial layer of particles is observed to undergo buckling and crumpling, without shedding of clay particles. Increasing the concentration of particles is shown to enhance the bubble stability by providing a higher resistance to dissolution and buckling. When subjected to complex temperature cycles, the clay-coated bubbles can remain stable in conditions for which uncoated bubbles dissolve completely. These results underpin the design of ultra-stable oil foams stabilized by solid particles with improved shelf life under changing environmental conditions

Frontier Agriculture, 1880-1910 : an Area Investigation of Human and Environmental Factors Involved in the Process of Agricultural Evolution in Davison County, South Dakota

Our curiosity about how an area has developed into what it is today invariably draws our attention to its initial situation. In the United States, the frontier serves as the logical locus upon which questions such as the latter can be laid. Frederick Jackson Turner has popularized the frontier concept by elevating its place in the history of the American national development. What Turner\u27s frontier thesis has for special offer to geography lies in the observation of the frontier as a discrete areal unit, set off, as it was, from the settled area due to the differential pace in the migration process. This observation, besides adding historical insights to our old concept of the region, lays a solid foundation for many viable area studies. Turner\u27s view that the frontier society evolves through a sequence of increasingly complex economic stages, such as from fishing through hunting and farming to urban society, unaccidentally came about at a time when the evolutionist theory was in vogue. This organic theory of social change draws essentially on phenomena found in the biological world and explains society in the same way a biologist does a living organism. Just as a biological organism evolves from a single cell to a complex structure with its specialized internal organs, societal change can be conceived of being a natural progress from a simple community of people to a complex society with its various institutions. Historically, many cultural patterns in place can be traced to the phenomenon of earlier spatial diffusion; only a few from natural evolution of cultural practice within their own home environment. From evolution to environment and spatial diffusion, theoretical argument becomes increasingly awkward to many. Such confusion, as analyzed by Berkhofer, stems from the failure of the critic to consider society\u27s different sectors, on which environmental influences play differently. Farming in the frontier represents a special facet of man-land relationship, a theme that will underly this study. By virtue of its natural resources, the northern interior was destined to become the agricultural heartland of America. To the building of this vast agrarian society, diverse human elements have contributed, as both foreign and native people intermingled. Early cultural differences were later overcome by common political consciousness and economic constraint. Over space, further differences exist in regional settlement pattern for reasons that can be traced to the very process of settling. Turner urged an examination of such differences and similarities, suggesting that this study could be a worthwhile undertaking

Reference-based analysis of lung single-cell sequencing reveals a transitional profibrotic macrophage.

Tissue fibrosis is a major cause of mortality that results from the deposition of matrix proteins by an activated mesenchyme. Macrophages accumulate in fibrosis, but the role of specific subgroups in supporting fibrogenesis has not been investigated in vivo. Here, we used single-cell RNA sequencing (scRNA-seq) to characterize the heterogeneity of macrophages in bleomycin-induced lung fibrosis in mice. A novel computational framework for the annotation of scRNA-seq by reference to bulk transcriptomes (SingleR) enabled the subclustering of macrophages and revealed a disease-associated subgroup with a transitional gene expression profile intermediate between monocyte-derived and alveolar macrophages. These CX3CR1+SiglecF+ transitional macrophages localized to the fibrotic niche and had a profibrotic effect in vivo. Human orthologs of genes expressed by the transitional macrophages were upregulated in samples from patients with idiopathic pulmonary fibrosis. Thus, we have identified a pathological subgroup of transitional macrophages that are required for the fibrotic response to injury

Picosecond to Terahertz Perturbation of Interfacial Water and Electropermeabilization of Biological Membranes

Non-thermal probing and stimulation with subnanosecond electric pulses and terahertz electromagnetic radiation may lead to new, minimally invasive diagnostic and therapeutic procedures and to methods for remote monitoring and analysis of biological systems, including plants, animals, and humans. To effectively engineer these still-emerging tools, we need an understanding of the biophysical mechanisms underlying the responses that have been reported to these novel stimuli. We show here that subnanosecond (≤500 ps) electric pulses induce action potentials in neurons and cause calcium transients in neuroblastoma-glioma hybrid cells, and we report complementary molecular dynamics simulations of phospholipid bilayers in electric fields in which membrane permeabilization occurs in less than 1 ns. Water dipoles in the interior of these model membranes respond in less than 1 ps to permeabilizing electric potentials by aligning in the direction of the field, and they re-orient at terahertz frequencies to field reversals. The mechanism for subnanosecond lipid electropore formation is similar to that observed on longer time scales-energy-minimizing intrusions of interfacial water into the membrane interior and subsequent reorganization of the bilayer into hydrophilic, conductive structures

Electric Field-Driven Water Dipoles: Nanoscale Architecture of Electroporation

<div><p>Electroporation is the formation of permeabilizing structures in the cell membrane under the influence of an externally imposed electric field. The resulting increased permeability of the membrane enables a wide range of biological applications, including the delivery of normally excluded substances into cells. While electroporation is used extensively in biology, biotechnology, and medicine, its molecular mechanism is not well understood. This lack of knowledge limits the ability to control and fine-tune the process. In this article we propose a novel molecular mechanism for the electroporation of a lipid bilayer based on energetics analysis. Using molecular dynamics simulations we demonstrate that pore formation is driven by the reorganization of the interfacial water molecules. Our energetics analysis and comparisons of simulations with and without the lipid bilayer show that the process of poration is driven by field-induced reorganization of water dipoles at the water-lipid or water-vacuum interfaces into more energetically favorable configurations, with their molecular dipoles oriented in the external field. Although the contributing role of water in electroporation has been noted previously, here we propose that interfacial water molecules are the main players in the process, its initiators and drivers. The role of the lipid layer, to a first-order approximation, is then reduced to a relatively passive barrier. This new view of electroporation simplifies the study of the problem, and opens up new opportunities in both theoretical modeling of the process and experimental research to better control or to use it in new, innovative ways.</p></div

Seasonal variations in the functional performance of industrial low-moisture part-skim mozzarella over a 1.5-year period

Seventy-five blocks of low-moisture part-skim (LMPS) Mozzarella cheese were procured from an industrial cheese plant, and the relationships between the physicochemical and functional properties were evaluated during refrigerated storage. In total, cheeses were obtained from 1 cheese vat on 7 different production dates, at two- to four monthly intervals, over a 1.5 year period; all cheeses were made using a standard recipe. The cheeses were held at 4°C for 0, 1, 2, 4, 8, 16 or 32 d and assayed for composition, primary proteolysis, serum distribution, texture profile analysis, heat-induced changes in viscoelastic behavior, cheese extensibility and melt characteristics. The results demonstrated a substantial increase in serum uptake by the calcium-phosphate para-casein matrix between 1 and 16 d of storage with a concomitant improvement in the functional performance of the cheese. Extending the storage time to 32 d resulted in further changes in the functional quality, concurrent with ongoing increases in protein hydration and primary proteolysis. Differences in the measured characteristics between the cheeses obtained on different sampling occasions were evident. Principal component analysis separated the cheeses based on their variance in functional performance, which was found to be correlated mainly with the calcium content of the cheese. The results indicate that the manufacturing process should be tightly controlled to minimize variation in calcium content, and enhance the quality consistency of the cheese

Statistical Mechanics of Relativistic One-Dimensional Self-Gravitating Systems

We consider the statistical mechanics of a general relativistic one-dimensional self-gravitating system. The system consists of $N$-particles coupled to lineal gravity and can be considered as a model of $N$ relativistically interacting sheets of uniform mass. The partition function and one-particle distitrubion functions are computed to leading order in $1/c$ where $c$ is the speed of light; as $c\to\infty$ results for the non-relativistic one-dimensional self-gravitating system are recovered. We find that relativistic effects generally cause both position and momentum distribution functions to become more sharply peaked, and that the temperature of a relativistic gas is smaller than its non-relativistic counterpart at the same fixed energy. We consider the large-N limit of our results and compare this to the non-relativistic case.Comment: latex, 60 pages, 22 figure

Characteristics of Fine Particulate Matter (PM2.5) over urban, suburban and rural areas of Hong Kong

In urban areas, Fine Particulate Matter (PM2.5) associated with local vehicle emissions can cause respiratory and cardiorespiratory disease and increased mortality rates, but less in rural areas. However, Hong Kong may be a special case since the whole territory often suffers from regional haze from nearby mainland China, as well as local sources. Therefore, to understand which areas of Hong Kong may be affected by damaging levels of fine particulates, PM2.5 data were obtained from March 2005 to February 2009 for urban, suburban and rural air quality monitoring stations; namely Central (city area, commercial area, and urban populated area), Tsuen Wan (city area, commercial area, urban populated, and residential area), Tung Chung (suburban and residential area), Yuen Long (urban and residential area), and Tap Mun (remote rural area). To evaluate the relative contributions of regional and local pollution sources, the study aims to test the influence of weather conditions on PM2.5 concentrations. Thus meteorological parameters including temperature, relative humidity, wind speed, and wind directions were obtained from the Hong Kong Observatory.. The results showed that Hong Kong’s air quality is mainly affected by regional aerosol emissions, either transported from the land or ocean, as similar patterns of variations in PM2.5 concentrations were observed over urban, suburban, and rural areas of Hong Kong. Only slightly higher PM2.5 concentrations were observed over urban sites, such as Central, compared to suburban and rural sites, which could be attributed to local automobile emissions. Results showed that meteorological parameters have potential to explain 80% of the variability in daily mean PM2.5 concentrations at Yuen Long, 77% at Tung Chung, 72% at Central, 71% at Tsuen Wan, and 67% at Tap Mun during the spring to summer part of the year. The results provide not only a better understanding of the impact of regional long-distance transport of air pollutants on Hong Kong’s air quality but also a reference for future regional-scale collaboration on air quality management