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The application of phagotrophic algae in waste activate sludge (WAS) treatment can largely accelerate WAS organics reclamation rate, because the phagotrophic capability of phagotrophic algae on intact microbial cells provides an efficient and fast way to digest microbial cells, which eliminate the need of the time-consuming hydrolysis of WAS solid organics. In this research work, different pretreatment methods of anoxia, alkali, and ultrasound were compared in terms of efficiency in releasing microbial cells from WAS flocs and subsequent growth of phagotrophic algae. Results show that ultrasonic pretreatment was the most efficient method since it yielded the highest microbial cell release and subsequent algae growth, while requiring the shortest pretreatment time. Mathematical modelling shows that the release of microbial cells in anoxic and ultrasonic pretreatment was achieved mainly through breaking physical forces of attraction, while the release of microbial cells in alkali pretreatment was achieved through breaking ionic bonds. Re-floc of released microbial cells was observed during algae growth, and the microbial cells released through breaking ionic bonds were less liable to reform floc. The electricity consumption of ultrasonic pretreatment was the highest, which was 6.9 times and 17.9 times of that of alkali and anoxic pretreatment. The electricity consumption of ultrasonic pretreatment can be reduced by performing alkali pretreatment prior to ultrasonic pretreatment.

Physical forces, such as dielectric, magnetic, electric, optical, and acoustic force, provide useful principles for the manipulation of particles, which are impossible or difficult with other approaches. Microparticles, including polymer particles, liquid droplets, and biological cells, can be trapped at a particular position and are also transported to arbitrary locations in an appropriate external physical field. Since the force can be externally controlled by the field strength, we can evaluate physicochemical properties of particles from the shift of the particle location. Most of the manipulation studies are conducted for particles of sub-micrometer or larger dimensions, because the force exerted on nanomaterials or molecules is so weak that their direct manipulation is generally difficult. However, the behavior, interactions, and reactions of such small substances can be indirectly evaluated by observing microparticles, on which the targets are tethered, in a physical field. We review the recent advancements in the manipulation of particles using a physical force and discuss its potentials, advantages, and limitations from fundamental and practical perspectives.

Chalcogen‐bonding cascade switching was introduced recently to produce the chemistry tools needed to image physical forces in biological systems. In the original flipper probe, one methyl group appeared to possibly interfere with the cascade switch. In this report, this questionable methyl group is replaced by a hydrogen. The deletion of this methyl group in planarizable push‐pull probes was not trivial because it required the synthesis of dithienothiophenes with four different substituents on the four available carbons. The mechanosensitivity of the resulting demethylated flipper probe was nearly identical to that of the original. Thus methyl groups in the switching region are irrelevant for function, whereas those in the twisting region are essential. This result supports the chalcogen‐bonding cascade switching concept and, most importantly, removes significant synthetic demands from future probe development., Not every atom matters: Chemistry tools made for the fluorescent imaging of physical forces in biological systems subjected to single methyl group deletions: Whereas methyl groups in the twisting region are essential, the pink methyl in the switching region does not interfere with function, a result that required significant multistep organic synthesis to obtain and will therefore be thoroughly appreciated in future probe design.

In this publication, novel bio-based composites made of epoxidized natural rubber with 50 mol% of epoxidation (ENR-50) are presented. The obtained materials, partially cured with a totally environmentally friendly crosslinking system consisting of natural ingredients, including quercetin and silica, exhibit a self-healing ability resulting from the self-adhesion of ENR-50 and reversible physical forces between the curing agent and the matrix. The impact of natural components on the crosslinking effect in uncured ENR-50 matrix was analyzed based on rheometric measurements, mechanical tests and crosslinking density. The partially crosslinked samples were next cut into two separate pieces, which were instantly contacted together under a small manual press, left at room temperature for a few days for the healing process to occur and finally retested. The healing efficiency was estimated by measuring mechanical properties before and after the healing process and was also confirmed by photos taken using optical and scanning electron microscope (SEM). According to the results, a combination of silica and quercetin is a totally safe, natural and effective crosslinking system dedicated to epoxidized natural rubber. The novel composites containing ingredients safe for human beings exhibit promising self-healing properties with a healing efficiency of up to 45% without any external stimuli and stand a chance of becoming innovative biomedical materials.

Cell function was incessantly regulated by several microenvironments that were dependent on chemical and physical interactions. Physical forces, such as compressive stress, shear stress, an...

Cells and tissues are constantly exposed to mechanical stress. In order to respond to alterations in mechanical stimuli, specific cellular machinery must be in place to rapidly convert physical force into chemical signaling to achieve the desired physiological responses. Mechanosensitive ion channels respond to such physical stimuli in the order of microseconds and are therefore essential components to mechanotransduction. Our understanding of how these ion channels contribute to cellular and physiological responses to mechanical force has vastly expanded in the last few decades due to engineering ingenuities accompanying patch clamp electrophysiology, as well as sophisticated molecular and genetic approaches. Such investigations have unveiled major implications for mechanosensitive ion channels in cardiovascular health and disease. Therefore, in this chapter I focus on our present understanding of how biophysical activation of various mechanosensitive ion channels promotes distinct cell signaling events with tissue-specific physiological responses in the cardiovascular system. Specifically, I discuss the roles of mechanosensitive ion channels in mediating (i) endothelial and smooth muscle cell control of vascular tone, (ii) mechano-electric feedback and cell signaling pathways in cardiomyocytes and cardiac fibroblasts, and (iii) the baroreflex.

Loss of podocytes, possibly through the detachment of viable cells, is a hallmark of progressive glomerular disease. Podocytes are exposed to considerable physical forces due to pressure and flow resulting in circumferential wall stress and tangential shear stress exerted on the podocyte cell body, which have been proposed to contribute to podocyte depletion. However, estimations of in vivo alterations of physical forces in glomerular disease have been hampered by a lack of quantitative functional and morphological data. Here, we used ultra-resolution data and computational analyses in a mouse model of human disease, hereditary late-onset focal segmental glomerular sclerosis, to calculate increased mechanical stress upon podocyte injury. Transversal shear stress on the lateral walls of the foot processes was prominently increased during the initial stages of podocyte detachment. Thus, our study highlights the importance of targeting glomerular hemodynamics to treat glomerular disease.

Highlights • First report on the current information on the effects of ultrasonic treatment on rice grain and rice starch. • Ultrasound imparts morphological, textural, and physicochemical changes in rice rain and rice starch. • Ultrasonication enhances the formation of metabolites, uptake of fortificants, and softening of rice texture. • Ultrasonic treatment can be used for applications towards the improvement of rice functional properties., As a green, nonthermal, and innovative technology, ultrasonication generates acoustic cavitation in an aqueous medium, developing physical forces that affect the starch chemistry and rice grain characteristics. This review describes the current information on the effect of ultrasonication on the morphological, textural, and physicochemical properties of rice starch and grain. In a biphasic system, ultrasonication introduced fissures and cracks, which facilitated higher uptake of water and altered the rice starch characteristics impacting textural properties. In wholegrain rice, ultrasonic treatment stimulated the production of health-related metabolites, facilitated the higher uptake of micronutrient fortificants, and enhanced the palatability by softening the rice texture. This review provides insights into the future direction on the utilization of ultrasonication for the applications towards the improvement of rice functional properties.

Fluorescent flipper probes have been introduced recently to image physical forces in biology. Their design is inspired by the combination of planarization and polarization that makes the color of astaxanthin, a carotenoid, turn blue in living lobsters or shrimps. Flipper probes are constructed around twisted dithienothiophene dimers. Upon planarization, donors and acceptors placed on both sides are coupled to generate push-pull systems that shift excitation maxima to the red, while the emission wavelength is mechanoinsensitive. To assure chemical stability, these donors and acceptors have to turn on only upon planarization. In living lobster, this is achieved most beautifully with non-covalent hydrogen bonds to and from the surrounding, planarizing protein. With flipper probes, the unorthodox chalcogen bonds prove best to produce turn-on donors and acceptors. The specific objective of this study was to explore different turn-on donors for the resulting chalcogen-bonding cascade switches. The focus is on substitution of the original triazoles with ethylenedioxythiophene (EDOT) and ortho-hydroxyphenyl (HOP) donors. Design, synthesis and evaluation of the respective flipper probes are described.

Recent experiments have suggested that enzymes and other small molecules chemotax toward their substrates. However, the physical forces driving this chemotaxis are currently debated. In this work, we consider a simple thermodynamic theory for molecular chemotaxis that is based on the McMillan-Mayer theory of dilute solutions and Schellman's theory for macromolecular binding. Even in the absence of direct interactions, the chemical binding equilibrium introduces a coupling term into the relevant free energy, which then reduces the chemical potential of both enzymes and their substrates. Assuming a local thermodynamic equilibrium, this binding contribution to the chemical potential generates an effective thermodynamic force that promotes chemotaxis by driving each solute toward its binding partner. Our numerical simulations demonstrate that, although small, this thermodynamic force is qualitatively consistent with several experimental studies. Thus, our study may provide additional insight into the role of the thermodynamic binding free energy for molecular chemotaxis.

The wind and current are two physical forces that strongly influence the biogeochemistry in coastal waters. Both of these forces could enhance the Chlorophyll-a (Chl-a) concentration through the upwelling process. Here we examine the contribution of the wind and current to the Chl-a variability in the South Java upwelling system in terms of wind stress and bottom stress respectively using satellite-derived and reanalysis data from 2002 to 2017. Ten longitudinally cells were used for further analysis. A long-term Chl-a shows a strong longitudinal gradient of Chl-a with the highest value on the shelf. Seasonal and Inter-annual Chl-a analysis shows the evidence of the monsoonal winds and other forcing effects relevant to the previous studies. Wind stress (τwx ) has a strong seasonal variation which is upwelling- favorable during southeast monsoon coincide with higher Chl-a suggesting wind as the main forces during that time, while bottom stress (τbx ) has more complicated variations, but it’s seen that τwx mostly downwelling-favorable or eastward circulations. There were about 39.92- 52.94% of positive Chl anomalous events generated by the combination of upwelling- favourable τwx and downwelling-favorable τbx , higher than other combinations. In terms of Oceanographic drivers, the wind has a higher effect on enhancing Chl-a through a negative correlation. τwx leads the Chl-a anomalies by about 15 – 24 days with a correlation coefficient of more than 0.6.

Three Co(II) metal-organic frameworks (MOFs) were synthesized employing a rational design approach. On the basis of the different structures of three complexes, we tested their absorption properties toward two anionic dyes. The absorption results indicate that not only uncoordinated functional groups in the structure play an important role in adsorbing capacity but also physical forces can affect absorbing ability. Water stability testing shows that three crystals display high stability in aqueous solutions with different pH values. To our delight, the framework integrity of three complexes can be well-retained even after absorbing dyes.

Wastes from different sources can be utilized as effective materials in wastewater bioremediation. From this point of view, this study was aimed to investigate the possibility of using pistachio shell, a non-conventional cheap biosorbent, obtained as agricultural solid waste for removal of a reactive-azo dye from water. The batch biosorption studies were carried out as a function of dye concentration and contact time. The experimental results showed that the biosorption process was very rapid (nearly 10 min) and the percent yield of biosorption decreased with an increase in dye quantity. Two- and three-parameter biosorption models were employed to describe the experimental kinetic and isotherm data. The results revealed that the biosorption data were best fitted by the pseudo-second-order and Sips models. The maximum biosorption capacity was found to be 109.535 mg g − 1 . The magnitude of standard Gibbs free energy change was calculated as − 5.184 kJ mol − 1 showing that physical forces were involved in the spontaneous biosorption of dye onto the biosorbent. This research suggests that the pistachio by-product can be an effective and low-cost material for the removal of such hazardous dyes from water.

Molecular recognition, the specific interaction between molecules by a combination of physical forces, has been a subject of scientific investigation for decades [...]

IntroductionMechanotransduction, the conversion of mechanical cues into biochemical signals, is crucial for many biological processes in plants and animals1,2. In mammals, some mechanosensory processes such as touch sensation and vascular development are mediated by the PIEZO family of mechanically activated (MA) ion channels3-5. In plants, the impact of gravity or soil properties on root development, wind on stem growth, and turgor pressure on plant-cell size and shape are proposed to involve activation of MA ion channels6,7. Homologues of the bacterial MA channel MscS (MSLs) exist in plants, and MSL8 is shown to be involved in pollen hydration8; however, the identity of the MA channels required for most mechanotransduction processes in plants have remained elusive9. Here, we identify various members of the 15 OSCA proteins from Arabidopsis thaliana (previously reported as hyperosmolarity sensors10,11) as MA ion channels. Purification and reconstitution of OSCA1.2 in liposomes induced stretch-activated currents, suggesting that OSCAs are inherently mechanosensitive, pore-forming ion channels. This conclusion is confirmed by a high-resolution electron microscopy structure of OSCA1.2 described in a companion paper12. Beyond plants, we present evidence that fruit fly, mouse, and human TMEM63 family of proteins, homologues of OSCAs, induce MA currents when expressed in naïve cells. Our results suggest that OSCA/TMEM63 proteins are the largest family of MA ion channels identified, and are conserved across eukaryotes. We anticipate that further characterization of OSCA isoforms which have diverse biophysical properties, will help gain substantial insight on the molecular mechanism of MA ion channel gating and permeation. OSCA1.1 mutant plants have impaired leaf and root growth under stress, potentially linking this ion channel to a mechanosensory role11. We expect future studies to uncover novel roles of OSCA/TMEM63 channels in mechanosensory processes across plants and animals.

Cholangiocytes are epithelial cells that line the network of interconnecting intrahepatic and extrahepatic bile ducts. The main physiologic function of cholangiocytes is the modification of the bile within the ductal lumen via coordinated bidirectional vectorial transport of ions, solutes, and water. These complex processes are regulated by extracellular signaling molecules, components of bile, and physical forces via various intracellular signaling pathways. The secretory and reabsorptive functions of cholangiocytes and the mechanisms by which these functions are regulated are reviewed in this chapter.

Hyaluronan (HA) possesses manifold mechanical and signaling properties in the body. Most of these activities are largely regulated by its molecular weight, which often triggers opposing functions. However the molecular basis for such function distinction between HA size categories remains unclear. Using a combination of biophysical techniques, we measured the physical forces between HA ligand and its specific receptor CD44 in both normal and lateral directions, at different HA molecular weights and bound states. It was found that the impact of HA multivalency is more than just the sum of separate monovalent bindings. The HA-CD44 specific interaction enhances with HA molecular weight and the maximum binding occurs at ∼1000 kD, possibly due to the balance between multivalent HA zipping effect and conformational entropy. High friction patches, probably from CD44 protein clustering, was observed in friction force microscopy (FFM) upon HA shearing, which is also dependent on HA molecular weight. These results could help to understand the biophysical mechanism of HA in regulating CD44-induced physiological activities and thus facilitate the new design of HA-based material in fine tuning the receptor responses.

Although it has been well demonstrated that specific nanotopographies alone can direct the fate decision of stem cells, there is still a huge gap, and at the same time, denotes a large challenge to translate this concept into clinical trials. Herein, we reported on using a kind of clinically relative biomaterial, hydroxyapatite, to prepare a kind of specific nanotopography constructed by the randomly oriented hydroxyapatite nanocrystal clusters, through high temperature water vapour treatment of the plasma-sprayed hydroxyapatite slices. Cell experiments demonstrated that bone-marrow mesenchymal stem cells could exert a strong adhesive tension on the nanocrystal clusters-oriented topography, and the formed strong intracytoskeletal stress in turn promoted cells to osteogenic differentiation rapidly; the differentiation process was associated with, but faster than, the model of osteoblastic differentiation. Therefore, our work reported here extremely shortened the gap from the concepts of mechanotransduction, i.e., extracellular physical forces sponsored from materials features can induce mechanochemical conversion to alter the fate decision of stem cells, to the clinical trials.

The thermodynamics of protein folding are dictated by a complex interplay of interatomic interactions and physical forces. A variety of unnatural protein-like oligomers have the capacity to manifest defined folding patterns. While the energetics of folding in natural proteins is well studied, little is known about the forces that govern folding in modified backbones. Here, we explore the thermodynamic consequences of backbone alteration on protein folding, focusing on two types of chemical changes made in different structural contexts of a compact tertiary fold. Our results reveal a surprising favorable impact on folding entropy that accompanies modifications that increase disorder in the ensemble of unfolded states, due to differences in the solvation of natural and unnatural backbones.

Many soil functions depend on the distribution of macro- (≥ 0.25 mm) and micro- (< 0.25 mm) aggregates and open space between aggregates (i.e. soil structure). Despite the importance of macroaggregates in soil, little is understood about how they form and become stable. We hypothesize that biological activities, chemical reactions, and physical forces which help to form macroaggregates differ from those involved in stabilization. Formation is a binding process where aggregate components are brought spatially closer together, ‘bagged’ or enmeshed by roots and fungal hyphae and ‘glued’ by labile SOM. Stabilization involves bonding processes between organic matter, clay minerals, cations, or plant or microbial biomolecules which increase internal cohesiveness. By separating aggregate formation from stabilization, the biological, chemical, and physical processes involved in maintaining long-term soil quality through stabilized soil structure will be more easily identified.

This paper discussed effects of organic matters/inorganic matters (OM/IM) ratios on the physical property, porosity and expansibility of ultra-light sewage sludge ceramsite (ULSC). The results indicated that ULSC with the high expansion and low water absorption were obtained when the OM/IM ratios were between 0.16 and 0.24. The OM/IM ratios had great effect on magnitude of physical forces of EF and ST; the relationship between EF and ST could determine pores formation and expansion of ULSC. Na-Ca feldspars of ceramsite grew as OM/IM ratios increased and the sintering process made some components of raw materials transform into other crystals having better thermostability.

The integrin family of adhesion receptors regulates basic functions of cells, and the signals they induce are altered in tumor cells. In this review we discuss how different integrin-dependent signals are generated during cell adhesion and by physical forces acting on cells. We also describe how reactive oxygen species are integral parts of integrin signaling and highlight a few important questions in the field. Answers to those may improve our understanding of integrins and their role in the development of cancer.

Cell migration is a highly integrated process and basic to many biological functions ranging from development to immune response and wound healing, to metastasis in cancer. For cells to migrate, they must generate and transduce traction forces to their environment, however, no technology to date has provided a high throughput solution for measuring these traction forces. Here we present a new assay for measuring cellular contractile forces employing robust multiwall culture plates: Using a 96-well plate format, we fabricate soft (∼1-10 kPa) elastic silicone rubbers with embedded fiduciary particles; by measuring the cell-induced deformation of these particles we calculate the cellular traction stresses and work using Fourier transform cytometry. We utilize this system to quantify the traction mechanics underlying cellular migration in several diseased settings including cancer metastasis, induced epithelial to mesenchymal transition (EMT), and aging; in all instances, we find significant changes in the contractile stresses and work, suggesting that contractile force screening may become a valuable biophysical diagnostic addition. This 96-well format and the use of a non-degrading soft silicone rubber create a simple and stable assay, and we anticipate that this technology will be of broad utility in diverse quantitative biological and health sciences.

espanolSe modificaron quimicamente cascaras de yuca y name con acido citrico y se evaluo su comportamiento para la adsorcion de Pb(II). Los experimentos de adsorcion se llevaron a cabo usando un tamano de particula en el rango de 0.5 a 1mm y un pH de 6. La determinacion del metal remanente en solucion fue medida mediante espectroscopia de absorcion atomica. Se obtuvo una capacidad de adsorcion de 52.34 y 98.36mg/g para las cascaras de yuca y name respectivamente. Ademas, se encontro que el modelo de Elovich y la isoterma de Langmuir y Freundlich ajustan adecuadamente los datos experimentales de adsorcion. Se establece tambien que el enlace se da principalmente por fuerzas fisicas, formandose solo una monocapa. Se concluye que los materiales en estudio modificados quimicamente con acido citrico pueden ser usados para el tratamiento de aguas residuales, especificamente en la remocion de metales pesados como el plomo (II). EnglishCassava and yam peels were chemically modified with citric acid and its performance for the adsorption of Pb(II) was evaluated. The adsorption tests were carried out using particle size between 0.5 and 1mm, and pH=6. The determination of the remaining metal in solution was measured by atomic absorption spectroscopy. These adsorption capacities were of 52.34 and 98.36 mg/g for cassava and yam peels, respectively. In addition, it was found that Elovich’s model and Langmuir's and Freundlich’s isotherms adequately fit the adsorption experimental data. It is also established that the bond occurs mainly due to physical forces, forming a single monolayer. It is concluded that the materials under study, which were chemically modified with citric acid, can be used for wastewater treatment, specifically for the removing of heavy metals such as lead (II).

Der Ophthalmologe, 109 (1), ISSN:0941-293X, ISSN:1433-0423

Patterns in nature have always fascinated human beings. They convey the idea of order, organization and optimization, and, to the enquiring mind, the alluring promise that understanding their building rules may uncover the forces that shaped them. In the retina, two patterns are outstanding: the stacking of cells in layers and, within the layers, the prevalent arrangement of neurons of the same type in orderly arrays, often referred to as mosaics for the crystalline-like order that some can display. Layers and mosaics have been essential keys to our present understanding of retinal circuital organization and function. Now, they may also be a precious guide in our exploration of how the retina is built. Here, we will review studies addressing the mechanisms controlling the formation of retinal mosaics and layers, illustrating common themes and unsolved problems. Among the intricacies of the building process, a world of physical forces is making its appearance. Cells are extremely complex to model as "physical entities", and many aspects of cell mechanotransduction are still obscure. Yet, recent experiments, focusing on the mechanical aspects of growth and differentiation, suggest that adopting this viewpoint will open new ways of understanding retinal formation and novel possibilities to approach retinal pathologies and repair.

Alkaloid molecules are very sensitive to changes and fluctuations in the physical forces around them and physical life parameters. They circulate inside and outside the organism in physiological or ecological ways, and they have important impact on the basic life strategies, such as herbivory, carnivory, and omnivory. Alkaloids can be of endogenic or exogenic origin. Endogenic peptide alkaloids are proteins having alkaloids that mimic bioactivity. How their amino acid element changes to an alkaloid element in activities with receptors is not still known. Exogenic alkaloids probably add their own microscopic mark to the molecules. Novelization of the alkaloids occurs in nature but is also planned by chemists using a large list of possible reactions and inductions. Alkaloids can produce problems in nature and human behavior. Morphinism, narcosis, and addiction are diseases based on alkaloid bioactivity or the lack of activity by endo- and exoreceptors. Molecular additions can develop new medicines and functional food and feed, and their activity is based on a molecular or residue basis.

Gap junctions form intercellular channels that mediate metabolic and electrical signaling between neighboring cells in a tissue. Lack of an atomic resolution structure of the gap junction has made it difficult to identify interactions that stabilize its transmembrane domain. Using a recently computed model of this domain, which specifies the locations of each amino acid, we postulated the existence of several interactions and tested them experimentally. We introduced mutations within the transmembrane domain of the gap junction-forming protein connexin that were previously implicated in genetic diseases and that apparently destabilized the gap junction, as evidenced here by the absence of the protein from the sites of cell-cell apposition. The model structure helped identify positions on adjacent helices where second-site mutations restored membrane localization, revealing possible interactions between residue pairs. We thus identified two putative salt bridges and one pair involved in packing interactions in which one disease-causing mutation suppressed the effects of another. These results seem to reveal some of the physical forces that underlie the structural stability of the gap junction transmembrane domain and suggest that abrogation of such interactions bring about some of the effects of disease-causing mutations.

Background Vacuum therapy is a routine and successful method for wound treatment and for the temporary covering of soft-tissue defects. It is an occlusive method that can be used for treating acute, chronic and infected wounds. To date, no data are available regarding secretion transit times and pressure conditions in lesions treated with vacuum therapy. The present study had as its objectives to examine the mechanisms of vacuum therapy and determine the effects of physical forces on the wound surface with the purpose of formulating recommendations for pressure settings using the various available vacuum pumps. Material and methods Using an appropriate model, we measured secretion transit times and pressures using two different vacuum therapy pads. We then conducted pressure measurements during dressing change in eight patients with wound surfaces greater than 20 cm(2). Results The secretion transit times remained unchanged with the polyvinyl alcohol (PVA) pad and a negative pressure of 40 kPa, but decreased by about 50 % when the black polyurethane (PU) pad was used. Pressure measurements showed that, at this negative pressure, there was only a slight positive external pressure of 31 mmHg on the wound surface. Conclusion When the PVA pad is used, negative pressures greater than 40 kPa should be applied in order to effect a maximum transit of wound secretion and prolongation of the use of the vacuum dressing. When the PU pad is used, the applied negative pressure can be lower due to the pad's larger pores, as recommended by Argenta and Morykwas. An excessive external pressure on the wound surface does not occur.

The integrin family of adhesion receptors regulates basic functions of cells, and the signals they induce are altered in tumor cells. In this review we discuss how different integrin-dependent signals are generated during cell adhesion and by physical forces acting on cells. We also describe how reactive oxygen species are integral parts of integrin signaling and highlight a few important questions in the field. Answers to those may improve our understanding of integrins and their role in the development of cancer.

Physical forces play an important role in modulating cell function and shaping tissue structure. Mechanotransduction, the process by which cells transduce physical force-induced signals into biochemical responses, is critical for mediating adaptations to mechanical loading in connective tissues. While much is known about mechanotransduction in cells involving forces delivered through extracellular matrix proteins and integrins, there is limited understanding of how mechanical signals are propagated through the interconnected cellular networks found in tissues and organs. We propose that intercellular mechanotransduction is a critical component for achieving coordinated remodeling responses to force application in connective tissues. We examine here recent evidence on different pathways of intercellular mechanotransduction and suggest a general model for how multicellular structures respond to mechanical loading as an integrated unit.

Obesity constitutes a serious health problem. Inflammation, which has recently been shown to follow adipocyte death, is at the basis of a series of pathogenic complications of obesity. Here we demonstrate, through modelling using the finite element method, that the bigger the adipocyte, the more fragile it becomes to rupture when submitted to common physical forces. This indicates that adipocyte size is an important determinant of cell death. Interventions to prevent adipocyte hypertrophy may, therefore, help to reduce the risk associated with obesity.

In recent years, the physical and chemical effects of ultrasound in liquid and solid media have been extensively used in food processing applications. Harnessing the physical forces generated by ultrasound, in the absence and presence of cavitation, for specific food processing applications such as emulsification, filtration, tenderisation and functionality modification have been highlighted. While some applications, such as filtration and emulsification are "mature" industrial processes, other applications, such as functionality modification, are still in their early stages of development. However, various investigations discussed suggest that ultrasonic processing of food and dairy ingredients is a potential and viable technology that will be used by many food industries in the near future.

The excitation-contraction coupling cycle (ECC) consists of a complex cascade of electrochemical and mechanical events; however, the relative contributions of these different processes in the regulation of cardiac myofibrillar structure are not well understood. There is extensive evidence to suggest that the mechanical aspects of the ECC play a crucial role in controlling the availability of contractile proteins for myofibrillar assembly. To examine if these physical forces might also serve to stabilize the structure of preexisting myofibrils, beating and nonbeating cultures of neonatal cardiac myocytes (NCM) were subjected to a 5% static stretch. Contractile arrest was achieved by treating NCM with 12 microM nifedipine, which resulted in immediate and sustained contractile arrest and initiated the evolution of marked myofibrillar abnormalities within 24 hours. As judged by scanning confocal and transmission electron microscopic examination, an external load appears to partially stabilize myofibrillar structure in nonbeating NCM. These results suggest that the maintenance of myofibrillar structure may be highly dependent upon the mechanical aspects of ECC.

Rheological properties of erythrocytes relate to the oxygen transfer to tissues in microcirculation. Erythrocytes deform by externally applied physical forces. The deformability modifies the pathway of oxygen diffusion inside the microvessel. The rate of oxygen release from flowing erythrocytes in a single microvessel is determined spectrophotometrically under the microscope.

The biomechanical properties of connective tissues play fundamental roles in the functioning of virtually every organ. These properties are critical determinants of how mechanical interactions of the body with its environment produce physical forces at the cellular level.

Capillary zone electrophoresis of peptide fragments from the tryptic digest of human recombinant insulin-like growth factor I (rhIGF-I) has been carried out and the observed mobilities used to compare the relative applicability of existing mobility models. In addition, the physical forces affecting electromigration have been systematically analyzed in order to more accurately describe the physical chemistry involved. Such an approach should further improve the ability to predict electrophoretic mobility in capillary zone electrophoresis.

A study involving the water sorption characteristics of cereal-bread type food fibers was conducted, using a gravimetrical adsorption apparatus. Water adsorption data for four dietary fibers, corn bran, wheat bran, oat fiber and rice fiber, were measured at 278, 288, 298 and 310 K. The results showed that the adsorption of water vapor on these fibers are primarily due to physical forces, and all fibers investigated exhibited energetically heterogeneous surfaces. It was found that the distribution of the major components of the dietary fiber has an impact on the fiber's water sorption capacity. The isotherm data were correlated by using the BET and GAB multilayer adsorption models. The BET equation gave accurate correlations for up to 35 to 40% of the saturation pressure, while the GAB equation provided much better correlation of the data for the higher relative pressures.

The role of the extracellular matrix (ECM) in the tumor microenvironment extends well beyond the formation of a barrier against tumor invasion. Through a combination of physical forces and chemical signals generated upon contact between cells and ECM proteins, the ECM exerts a control on the proliferation and survival of cancer cells, which were previously considered to be solely affected by genetic alterations. The interaction between tumor cells and the ECM is also a dynamic one that changes upon modification of the ECM by proteases produced by tumor cells and by normal cells in the tumor microenvironment. These proteases modify the ECM generating cryptic epitopes, producing proteolytic fragments that are biologically active and releasing growth factors and cytokines that are trapped in the ECM. Our knowledge of the mechanisms by which the ECM controls cancer cells has significantly improved over the last 10 years and is now leading toward clinical trials testing agents disrupting tumor cell–ECM interaction.

The field of drug–membrane interactions is one that spans a wide range of scientific disciplines, from synthetic chemistry, through biophysics to pharmacology. Cell membranes are complex dynamic systems whose structures can be affected by drug molecules and in turn can affect the pharmacological properties of the drugs being administered. In this tutorial review we aim to provide a guide for those new to the area of drug–membrane interactions and present an introduction to areas of this topic which need to be considered. We address the lipid composition and structure of the cell membrane and comment on the physical forces present in the membrane which may impact on drug interactions. We outline methods by which drugs may cross or bind to this membrane, including the well understood passive and active transport pathways. We present a range of techniques which may be used to study the interactions of drugs with membranes both in vitro and in vivo and discuss the advantages and disadvantages of these techniques and highlight new methods being developed to further this field.

The field of drug–membrane interactions is one that spans a wide range of scientific disciplines, from synthetic chemistry, through biophysics to pharmacology. Cell membranes are complex dynamic systems whose structures can be affected by drug molecules and in turn can affect the pharmacological properties of the drugs being administered. In this tutorial review we aim to provide a guide for those new to the area of drug–membrane interactions and present an introduction to areas of this topic which need to be considered. We address the lipid composition and structure of the cell membrane and comment on the physical forces present in the membrane which may impact on drug interactions. We outline methods by which drugs may cross or bind to this membrane, including the well understood passive and active transport pathways. We present a range of techniques which may be used to study the interactions of drugs with membranes both in vitro and in vivo and discuss the advantages and disadvantages of these techniques and highlight new methods being developed to further this field.

Adsorption isotherms of water vapor on molecular sieve 13X were obtained at 288, 298, and 308 K. The isotherms were of Type 1 and exhibited hysteresis upon desorption. The heat of adsorption data indicated that water was held on the surface by physical forces and the molecular sieve 13X provided a heterogeneous surface for the water vapor. The equilibrium data were correlated by the Polanyi potential theory and the theory of the pore volume filling proposed by Dubinin and co-workers.

This chapter discusses the requirements of good separation design and how various mechanical devices take advantage of the physical forces in the produced stream to achieve good separation Separators are sometimes called “gas scrubbers” when the ratio of gas rate to liquid rate is very high. A “slug catcher,” commonly used in gas gathering pipelines, is a special case of a two-phase gas–liquid separator that is designed to handle large gas capacities and liquid slugs. Some operators use the term “traps” to designate separators that handle flow directly from wells. In any case, they all have the same configuration and are sized in accordance with the same procedure. Separators are classified as “two-phase” if they separate gas from the total liquid stream and “three-phase” if they also separate the liquid stream into its crude oil and water components. Separators are designed and manufactured in horizontal, vertical, spherical, and a variety of other configurations. Each configuration has specific advantages and limitations. Selection is based on obtaining the desired results at the lowest “life-cycle” cost. Many types of separators, such as horizontal, vertical, centrifugal, and venturi, are discussed in this chapter.

Earlier we demonstrated significant differences in proximal tubular Na transport inhibition during saline volume expansion (VE) depending on whether artificial (AF) or native harvested tubular fluid (HTF) was used. In the present experiments the shrinking-drop technique was used to measure volume flux (Jv) in the early- and late-clip models of VE with AF alternating with HTF. In early-clip rats, with AF, Jv (x 10(4) mm3.mm-2.s-1) during the nonexpanded period was 2.92 +/- 0.105; during subsequent VE, it was 2.20 +/- 0.180 and 1.97 +/- 0.149 with HTF (for the latter two P greater than 0.3). In late-clip rats they were 2.83 +/- 0.135, 1.99 +/- 0.157, and 1.50 +/- 0.171 (for the latter two P less than 0.001), respectively. With AF, transport was inhibited equally in both models during VE. There were no significant differences in the electrolyte composition of AF and HTF during shrinkage as measured by microprobe analysis. The 47% inhibition of Jv with HTF but not AF during VE in the late-clip but not the early-clip rats strongly implies the presence of factors other than physical forces during VE, which inhibit proximal tubular Na transport. Studies of tubular transport during VE need to be performed using both AF and HTF.

Therapeutic proteins can be difficult to work with due to the fact that each protein has properties and functions that are unique. These exclusive properties are in part due to the proteins three-dimensional shape (secondary and tertiary structure). This shape is determined by bends in the amino acid sequence generated by electrostatic interactions, hydrogen bonds, and hydrophobic-hydrophilic interactions between neighboring amino acids. These bonding interactions are weak and can be severed by chemical or physical forces. Thus, therapeutic proteins can be denatured during manufacture and by methods used to deliver them to the body.Copyright © 2007 by ASME

DNA is a living molecule, writhing, twisting and bending in response to the physical forces applied to it by genetic processes. Twisting and untwisting of the double helix by powerful molecular motors generates, at least transiently, high levels of torques. Although under relaxed conditions the double helical B-form is the predominant conformation of DNA, in response to physical stress, B-DNA strains inhomogeneously, adopting a variety of alternative structures. These structures are the sites of genetic damage that increase the fragility of the genome, but they may also participate in physiological processes performing functions not achievable using conventional duplex. The dynamic response of DNA to supercoiling forces contributes to control of genes such as c-myc whose physiological levels must be precisely regulated.

Cortical cataracts usually begin with either sharp limited clear fluid clefts, resulting in opaque spokes, or clear lamellar separations, resulting in cuneiform opacities. They do not commence prior to 45 years of age. From this age on an increase in lens nuclei hardening can be detected. Therefore, during disaccommodation in older lenses, mechanical shear stresses must develop between the soft remaining cortices and the harder nuclei. These shear stresses are significant regarding the different cortical ruptures in predisposed lenses: in a privileged radial direction (according to zonular traction) of the sharp limited cortical spokes, or in parallel microridges at the commencement of lamellar separations, as observed when a rubber surface slides against a harder object. In pure cortical cataracts the ion pump (K+ > Na+) and investigated metabolic parameters remain largely intact. Therefore, it is not surprising that, in contrast to subcapsular cataracts, subcapsular opacities do not occur. Subcapsular cataracts are known to be caused by a variety of factors: aging, diabetes, corticosteroids, iridocyclitis, or X-ray, among many others. In contrast to cortical cataracts, subcapsular cataracts were found to be closely associated with ion pump damage (Na+ > K+) and a variety of metabolic activity alterations. In subcapsular cataracts passive fluids (from the vitreous and camera anterior) enter externally through the lens capsule. This initially forms numerous free clear, secondary grey, subcapsular fluid vacuoles. If the ion pump (metabolic barrier) is more severely damaged fluids may also enter the lens nucleus (secondary grey nuclear cataract), which rarely results in intumescent cataract. In cortical and subcapsular cataracts and lens perforations the main cause of grey opalescence appears to be the result of lens proteins (water-soluble crystalline) coming into direct contact with free fluids (water). In cortical cataracts this happens in the area of sharp limited mechanical cortical ruptures (fluid clefts), and in subcapsular cataracts during passive, external fluid entry, resulting in subcapsular fluid vacuoles and opacities, and also later grey-white nuclear opacities. The importance of water contact with water-soluble lens crystallines in behalf of light scattering and turbidness also has been investigated experimentally.