Recent Macroscopic Studies

One of the most controversial issues in the field of diffusion in zeohtes is the so-called window effect . This term was coined by Gorring to interpret the anomalous transport results obtained for hnear alkanes in zeoHte T [46], but his experimental conditions have been criticized. More recent macroscopic studies could not reproduce the periodic variation in diffusivity, and a monotonic decline with carbon number was reported [47,48]. However, a microscopic technique, such as neutron scattering, is better suited to probe anomalous diffusion mechanisms on a molecular scale, since it is much less sensitive to the influence of defects or internal transport barriers within the zeolite crystals. 

According to the previous reports on the functional anatomy of the ACL, however, it could be divided into three bundles the anteromedial (AM), the intermediate (IM), and the posterolateral (PL) [6, 7]. Additionally, it is well-known that the natural ACL forms a crescent-shaped footprint on the femur and a triangular one on the tibia. Furthermore, a recent macroscopic study by Siebold et al. showed that the C -shaped tibial insertion runs from along the medial tibial spine to the anterior aspect of the lateral meniscus [8]. 

The results obtained to date are considerable and show that the chemistry of the TcN group may well be the most varied and interesting of the transition metal nitrido complexes [1,9,10]. The aim of this chapter is to provide a fairly comprehensive review of the literature up to the latter part of 1994. Additional data may be found in two conference volumes [11,12] and a recent review of Tc coordination chemistry [4]. For macroscopic studies with the long-lived "Tc (ti/2 = 2.11 x 10s years) the "Tc radionuclide is denoted simply as Tc. No carrier added studies and radiopharmaceutical applications utilizing the shortlived "mTc radionuclide (ti/2 = 6.01 hours) are denoted as "mTc. 

Recent theoretical studies indicate that thermal fluctuation of a liquid/ liquid interface plays important roles in chemical/physical properties of the surface [34-39], Thermal fluctuation of a liquid surface is characterized by the wavelength of a capillary wave (A). For a macroscopic flat liquid/liquid interface with the total length of the interface of /, capillary waves with various A < / are allowed, while in the case of a droplet, A should be smaller than 2nr (Figure 1) [40], Therefore, surface phenomena should depend on the droplet size. Besides, a pressure (AP) or chemical potential difference (An) between the droplet and surrounding solution phase increases with decreasing r as predicted by the Young-Laplace equation AP = 2y/r, where y is an interfacial tension [33], These discussions indicate clearly that characteristic behavior of chemical/physical processes in droplet/solution systems is elucidated only by direct measurements of individual droplets. 

Since the Navier s slip hypothesis of the last century, most experiments have failed to obtain positive evidence for a slip boundary condition on macroscopic scales in low molar mass liquids. However, Navier s notion of slip turns out to be extremely useful and convenient for the latest description of flow anomalies of highly entangled polymer melts including linear polyethylenes (LPE). The ability of a melt/solid interface to possess two profoundly different states as shown by Fig. 4a,b clearly reveals the potential role of interfacial slip in governing various melt flow phenomena in high pressure extrusion. Before reviewing recent experimental studies that have elucidated the molecular origins of different flow... 

In recent years, studies of solutions of polymer blends and of copolymers have aroused a substantial theoretical and experimental interest. This is motivated by both numerous applications and more fundamental issues concerning the usefulness of the scaling and universality concepts to describe the thermodynamic properties and the phase transitions in these systems. In this lecture, chain interactions in dilute and semidilute solutions are reviewed and it is discussed how and when the interactions between chemically different monomers lead to a macroscopic phase separation in the case of ternary polymer A-polymer B- solvent systems and to a mesophase formation in diblock-copolymer solutions. The important conclusion is that due to both the overall monomer concentration fluctuations (excluded volume effects) and the composition fluctuations, the classical Flory theory often fails. This requires the use of the renormalization method and of scaling concepts to give a correct description of the phase diagrams and the critical phenomena observed in these complex systems. We give only here a brief outline, a complete review has been published elsewhere, ... 

Solving the nucleation mechanism is important to understand structures and physical properties of any materials. To our best knowledge, no one has succeeded in observing directly the nucleation from the melt, because the number density of small nuclei on the order of nanometers (which we will henceforth call a nano-nucleus ) is too small to detect [4, 5]. Hence, only alternative experimental studies have been performed on macroscopic crystals (macro-crystals) by means of optical microscopy (OM) or bubble chamber [2]. Recent simulation studies performed on colloid systems [6, 7] also fail to provide a direct observation of nano-nucleation because the thermal fluctuation of nano-nuclei should be much more significant than that of macro-crystals or macro-colloids. This chapter introduces CNT, describes experimental approaches, and discusses the results of direct observation of nano-nucleation. 

This chapter and the two that follow are introduced at this time to illustrate some of the many extensive areas in which there are important applications of surface chemistry. Friction and lubrication as topics properly deserve mention in a textbook on surface chemistiy, partly because these subjects do involve surfaces directly and partly because many aspects of lubrication depend on the properties of surface films. The subject of adhesion is treated briefly in this chapter mainly because it, too, depends greatly on the behavior of surface films at a solid interface and also because friction and adhesion have some interrelations. Studies of the interaction between two solid surfaces, with or without an intervening liquid phase, have been stimulated in recent years by the development of equipment capable of the direct measurement of the forces between macroscopic bodies. 

---