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The energies associated with surfaces — surface energy, interfacial energy, surface tension, and work of adhesion — drive many surface phenomena including tribological ones such as adhesion and friction. This chapter discusses the physical origins of surface energies for liquids and solids, and how the concepts of capillary pressure, capillary condensation, wetting, and work of adhesion are derived from surface energy. Further, this chapter covers the different methods for measuring surface energies, including a thorough discussion of the most common method to measure the surface energy of solids: contact angle measurements of liquid droplets on surfaces. The chapter also introduces how surface energies and surface tensions lead to adhesion and adhesion hysteresis between contacting surfaces, which is followed up in the subsequent chapters on surface forces.

This chapter summarises a selection of results on the inviscid limit of the stochastic Burgers equation emphasising geometric properties of the caustic, Maxwell set and Hamilton-Jacobi level surfaces and relating these results to a discussion of stochastic turbulence. It shows that for small viscosities there exists a vortex filament structure near to the Maxwell set. It is discussed how this vorticity is directly related to the adhesion model for the evolution of the early universe, and new explicit formulas for the distribution of mass within the shock are included.

As it is more practical to measure the forces acting between two contacting surfaces then the energies of surfaces, this chapter covers those surface forces that are derived from surface energies. The starting point is Derjaguin's approximation, which relates the energy between two flat surfaces to other geometries: sphere/flat, sphere/sphere, and crossed cylinders. Next is a discussion of the surface forces in dry contacts with no liquid menisci around the contact points. This discussion covers the cases where adhesion causes deformation (JKR theory) and where deformation is insignificant (DMT theory). The second half of this chapter deals with how liquid menisci around contacts contribute to adhesion forces, both for sphere on flat geometries and for contacting rough surfaces.

This chapter presents the theory of laser-induced deformation and patterning of irradiated surfaces. Topics discussed include laser irradiation and thin film deformation, laser-induced temperature distribution, vacancy dynamics in strained crystals, deformation equations for thin films, variational principle for the free energy, deformation instability and surface patterning, and the influence of crystal anisotropy and adhesion.

The incorporation of nanofillers into soy protein materials significantly enhances tensile strength and modulus, and in some cases, contributes to a simultaneous increase in strength and elongation. The decrease in tensile strength that results from plasticization, is therefore, to some extent recovered. Water absorption usually decreased with the incorporation of nanofillers. In addition, the unique properties of some nanofillers such as the electron conductivity of carbon nanotubes and the antiflammability of layered silicates, can be transplanted into soy protein based nanocomposites. The nanocomposite shows great potential for partly solving the two prevailing problems of low strength and water sensitivity, which greatly hamper the development and application of soy protein based plastics. It also contributes to the development of high performance/novel functionality soy protein based materials. Contrary to most cases with soy protein as matrix, one recent study focused on applying soy protein nanoparticle aggregates to modify styrene-butadiene elastomer. The results showed that compact soy protein nanoparticle aggregates interacted more strongly with the polymer matrix and dispersed more uniformly than crude soy protein, and hence produced better modulus retention for the nanocomposites. Without doubt, soy protein based fibres (such as textiles) and adhesives can be further improved in terms of mechanical or adhesion performance by incorporating the proper nanofiller. The single most important factor affecting the high performance of soy protein based nanocomposites is strengthening the interfacial adhesion between the soy protein matrix and nanofillers. Chemical modification on the nanofiller surface is expected to improve the miscibility between filler and soy protein matrix. Furthermore, grafted long polymer chains may penetrate the soy protein matrix to produce a “co-continuous phase” structure, where the interactions and entanglements between grafted polymer chains and soy protein chains contribute to stronger interfacial adhesion.

Biological tissue: The elastic properties of biological tissue show much greater contrast than their optical properties. Cells can be imaged in an aqueous medium, so that the variation with environment and time of their mechanical properties and adhesion to a substrate can be measured. For soft tissue, time‐resolved techniques are more relevant than Rayleigh wave interference. Mineralized tissues such as teeth can support Rayleigh waves, giving contrast from carious lesions and allowing line‐focus‐beam V(z) analysis to measure elastic anisotropy. Bone is an intermediate case, with contrast from its mechanical structure.

Some layered structures offer separate reflections from adjacent surfaces. In this way interior imaging of semiconductor devices allows failure analysis before opening up the packaging. This can be considered as a kind of high resolution non‐destructive testing, and may prove to be the widest industrial use of acoustic microscopy. Laminated polymer coatings can be imaged by separating the reflections. Layered structures can also be studied through the effect on V(z) of the layers on waves propagating parallel to the surface, either in a plate mode or perturbing the propagation of Rayleigh waves. Adhesion can be observed only through its effect on elastic properties. Some layers can be studied in section, revealing effects of anisotropy and scattering of Rayleigh waves.

This chapter first discusses experiments on the adhesion of ice to other materials, which presents very real practical problems in cold climates. It then considers the low coefficient of friction for objects like skates sliding on ice. This is due to a thin film of liquid, produced not by pressure melting but by local heating.

Previous chapters have revealed the importance of molecular diffusion in tissue engineering. Molecules—and gradients of molecules—may represent the underlying mechanism of tissue induction and pattern formation (Chapter 3); growth factors—and the rate of delivery of growth factors to a cell surface—can influence the rate of cell proliferation (Chapter 4); chemoattractants can influence the rate and pattern of cell migration within a tissue space (Chapter 7). To think quantitatively about these processes, it is often helpful to think about molecular concentrations and the spatial variations in concentration that produce diffusion fluxes. This idea has been illustrated earlier in the book for specific examples such as bicoid gradient formation in the insect embryo (Section 3.3.4) and ligand diffusion to the cell surface (Section 4.3.2). Some of the basic concepts of molecular transport are also reviewed in Appendix B. But tissues are often heterogeneous structures, formed by the assembly of cells and the accumulation of matrix materials in the extracellular space. The heterogeneous composition of tissues can have a dramatic influence on local rates of molecular movement through the tissue; capillary endothelial cells prevent the diffusion of intravascular proteins into the tissue interstitial space, for example. This chapter discusses this concept and provides quantitative methods for evaluating rates of molecular movement between tissue spaces that are separated by diffusive barriers. In addition, the last section of the chapter shows how this same analysis may be useful when thinking about rates of cellular movement between tissue compartments. In multicellular organisms, thin lipid membranes serve as semipermeable barriers between aqueous compartments. The plasma membrane of the cell separates the cytoplasm from the extracellular space; endothelial cell membranes separate the blood within the vascular space from the rest of the tissue. Properties of the lipid membrane are critically important in regulating the movement of molecules between aqueous spaces. While certain barrier properties of membranes can be attributed to the lipid components, accessory molecules within the cell membrane—particularly transport proteins and ion channels—control the rate of permeation of many solutes.

As it more practical to measure the forces acting between two contacting surfaces then the energies of surfaces, this chapter covers those surface forces that are derived from surface energies. The starting point is Derjaguin’s approximation, which relates the energy between two flat surfaces to the force in other geometries: sphere/flat, sphere/sphere, and crossed cylinders. Next is a discussion of the surface forces in dry contacts with no liquid menisci around the contact points. This discussion covers the cases where adhesion causes significant deformation (JKR theory), where deformation is insignificant (DMT theory), and the cases in between. How surface roughness impacts adhesion is also discussed. The second half of this chapter deals with how liquid menisci around contacts contribute to adhesion forces, both for the sphere-on-flat geometry and for contacting rough surfaces.

This task assesses the following clinical skills: … ● Patient safety ● Communication with patients and their relatives ● Information gathering ● Applied clinical knowledge … You are in the gynaecology clinic and your next patient is Rachel Sawyer a 38- year- old woman suffering from heavy and irregular periods. She has a BMI of 42 and has been diagnosed with PCOS in the past. Your task is … ● To take a focussed history ● Explain what examination and investigations need to be performed to Rachel ● Make a management plan … You have 10 minutes for this task (+ 2mins initial reading time). Please read instructions to candidate and actor. Allow the candidate to conduct the interview undisturbed unless they are straying off the track of the question (in which case you can show them their instructions again). This patient has heavy and irregular periods. The history of presenting complaint should cover: … ● The extent, duration, and inconvenience caused by the bleeding ● Establish the menstrual history from menarche ● Last menstrual period and present menstrual cycle ● Past gynaecological history, including PCOS ● No medical, surgical, family history ● No allergies ● Normal and regular smears ● Nulliparous ● Wants to preserve fertility … Once the candidate has taken a relevant history, they are expected to explain that they will need to perform a speculum examination and bimanual examination to Rachel. They should explain that this is to rule out any obvious abnormality in the vagina/ cervix and to assess the uterus and adnexa. Abdominal examination— unremarkable: … ● Speculum examination— cervix satisfactory ● Bimanual examination— uterus bulky, retroverted, mobile, no adnexal masses Investigations ● Endometrial sampling— either at this consultation or accept another appointment- This is to assess the endometrium as, although 38, Rachel has risk factors of High BMI, PCOS, and nulliparity ● TVS- as Rachel has a high BMI, the sensitivity of an internal examination is reduced, TVS, not TAS will be useful due to high BMI.

Embryonic morphogenesis refers to the stages during which embryos and their organs acquire their functional structure. It requires groups of cells with similar properties to organize themselves in space and adopt distinctive shapes. The physical mechanisms that control cell dynamics during that time are slowly beginning to emerge from the study of a few simple systems. This chapter presents some examples outlining the current understanding of cell mechanics from the physics point of view, emphasizing the balance between cortical tension and cell adhesion, the behaviour of motors, and the response to tension. It also outlines how modelling is gaining prominence.

This chapter provides the basics to deduce multiphase models for the essential constituents present in tumours (cells, extracellular matrix, extracellular liquid, and possibly blood and limphatic vasculature). All the steps of the modelling procedure are explained in detail, special attention being paid to the meaning of all the different terms involved in the model. The chapter focuses on several mechanical aspects related to tumour growth, e.g., the activation of mechanotransduction pathways inside the cell, contact inhibition phenomena, the formation of stiffer fibrotic tissues, the adhesion phenomena characterizing the mechanical interaction between cells and between cell and extracellular matrix, and cell re-organization within the tissue.

This chapter examines inflammatory events associated with focal cerebral ischaemia. It evaluates the hypothesis that polymorphonuclear (PMN) leukocytes participate in microvascular responses to ischaemia and that they contribute directly to brain tissue injury and neuronal death. The chapter describes how PMN leucocytes can contribute to parenchymal injury and the steps involved in leucocyte invasion into the ischaemic central nervous system (CNS). It also discusses the genetic manipulation of leucocyte adhesion/activation and the role of leucocytes in cerebrovascular vasomotor reactivity.

Perhaps the simplest realization of tissue engineering involves the direct administration of a suspension of engineered cells—cells that have been isolated, characterized, manipulated, and amplified outside of the body. One can imagine engineering diverse and useful properties into the injected cells: functional enzymes, secretion of drugs, resistance to immune recognition, and growth control. We are most familiar with methods for manipulating the cell internal chemistry by introduction or removal of genes; for example, the first gene therapy experiments involved cells that were engineered to produce a deficient enzyme, adenine deaminase (see Chapter 2). But genes also encode systems that enable cell movement, cell mechanics, and cell adhesion. Conceivably, these systems can be modified to direct the interactions of an administered cell with its new host. For example, cell adhesion signals could be introduced to provide tissue targeting, cytoskeleton-associated proteins could be added to alter viscosity and deformability (in order to prolong circulation time), and motor proteins could be added to facilitate cell migration. Ideally, cell fate would also be engineered, so that the cell would move to the appropriate location in the body, no matter how it was administered; for example, transfused liver cells would circulate in the blood and, eventually, crawl into the liver parenchyma. Cells find their place in developing organisms by a variety of chemotactic and adhesive signals, but can these same signaling mechanisms be engaged to target cells administered to an adult organism? We have already considered the critical role of cell movement in development in Chapter 3. In this chapter, the utility of cell trafficking in tissue engineering is approached by first considering the normal role of cell recirculation and trafficking within the adult organism. Most cells can be easily introduced into the body by intravenous injection or infusion. This procedure is particularly appropriate for cells that function within the circulation; for example, red blood cells (RBCs) and lymphocytes. The first blood transfusions into humans were performed by Jean-Baptiste Denis, a French physician, in 1667. This early appearance of transfusion is startling, since the circulatory system was described by William Harvey only a few decades earlier, in 1628.