Microscopic nature

Eigler D M and Schweizer E K 1990 Positioning single atoms with a scanning tunneling microscope Nature 344 524... 

Forster J S and Frommer J E 1988 Imaging of liquid crystals using a tunnelling microscope Nature 333 542... 

Ducker W A, Senden T J and Pashley R M 1991 Direct measurement of colloidal forces using an atomic force microscope Nature 353 239... 

Overney R M, Meyer E, Frommer J, Brodbeck D, Luthi R, Flowald L, Guntherodt Fl-J, Fu]ihara M, Takano FI and Gotoh Y 1992 Friction measurements of phase separated thin films with a modified atomic force microscope Nature... 

A point defect refers to a localized defect (such as a monovacancy) or impurity (such as interstitial O). This includes any relaxation and/or distortion of the crystal around it. Many point defects are now ratlier well understood, especially in Si, tlranks to a combination of experiments providing infonnation of microscopic nature... 

The hardness of clays is difficult to determine due to the microscopic nature of the crystals, but hardness is usually 2-3 in Mohs scale and many clays give a hardness of 1 in field tests. 

The topic of this review, reactions at metal surfaces, has been in general treated in a similar way to gas-phase reactivity. High level ab initio electronic structure methods are used to construct potential energy surfaces of catalytically important surface reactions in reduced dimensions. Once a chemically accurate potential surface is available, quantum or classical dynamics may be carried out in order to more deeply understand the microscopic nature of the reaction. 

Tite, M. S. and Y. Maniatis (1975), Examination of ancient pottery using the scanning electron microscope, Nature 257, 122-123. 

Dyson, J. A transmission-type interferometer microscope. Nature 164, 229... 

Eigler D, Lutz CP, Rudge WE (1991) An atomic switch realized with the scanning tunneling microscope. Nature 352 600... 

Ducker, W. A., T. J. Senden, and R. M. Pashley (1991), "Direct Measurement of Colloidal Forces Using an Atomic Force Microscope", Nature 353, 239-241. 

The origin of the distribution should be related to the inherent disorder in the glass. However, the microscopic nature of the j8-relaxation still remains unclear. 

Fluctuations of an isolated step are also suppressed by the microscopic energy cost to form kinks. On coarse-graining, this translates into an effective stiffness or line tension that tends to keep the step straight. Standard microscopic 2D models of step arrays incorporating both of these physical effects include the free-fermion model and the Terrace-Step-Kink (TSK) model. Both models have proved very useful, though their microscopic nature makes detailed calculations difficult. 

Lopinski, G. P., Moffatt, D. J., Wayner, D. D. and Wolkow, R. A. Determination of the absolute chirality of individual adsorbed molecules using the scanning tunnelling microscope. Nature 392, 909 (1998). 

T,he stoichiometric characterization of detergent-protein complexes has been the object of many studies over the past 30 years (6). Recent studies have placed more emphasis upon developing a molecular-kinetic description of the complex (2, 8). The importance of such descriptions lies in the fact that detergent-protein complexes can be considered as lipoprotein model systems. Indeed, virtually all conceptions of the microscopic nature of lipid-protein interactions are based on the properties of detergent-protein complexes (3). 

Although empirical solubility rules and A//SO[n values show some degree of correlation with polarity or other attributes of solute and solvent, the situation at the molecular level can be rather complex (Sidebar 3.11). Heat evolution or absorption is thus a deep clue to the microscopic nature of solution formation, indicating its possible relationship to chemical reaction phenomena... 

In order to verify which of the above nucleation mechanisms accurately represents hydrate nucleation, it is clear that experimental validation is required. This can then lead to such qualitative models being quantified. However, to date, there is very limited experimental verification of the above hypotheses (labile cluster or local structuring model, or some combination of both models), due to both their stochastic and microscopic nature, and the timescale resolution of most experimental techniques. Without experimental validation, these hypotheses should be considered as only conceptual aids. While the resolution of a nucleation theory is uncertain, the next step of hydrate growth has proved more tenable for experimental evidence, as discussed in Section 3.2. 

Eigler, D. M. Schweizer, E. K. Positioning single atoms with scanning tunnelling microscope. Nature (London) 344, 524-6 (1990). 

The origins of the YL have been widely debated. Ogino and Aoki [1] proposed a model in which the YL is a transition between a shallow donor and a deep acceptor level. We will see that a variety of experiments now confirm this model. Proposals for the microscopic nature of the deep level have included a complex between a Ga vacancy (VGa) and a carbon atom [1], an NGa antisite [2] and an isolated VGa [3,4] (or a complex between Vcja and oxygen [4]). 

It is evident, however, that this enormous gain in terms of computational time (and simplicity of the protocol) will involve some disadvantages. The main one is the loss of the microscopic nature of the solvent molecules. This issue becomes particularly delicate when solute-solvent specific interactions such as hydrogen bonds are present in the liquid solution in these cases, the picture obtained using a continuum-only description will be incomplete as it misses an important part of the solute-solvent interactions. 

Specific heat measurements40 indicate that the assumption of static frozen glass disorder at low temperatures may be too restrictive and that the intra-H-bond hydrogen motion may still persist in the form of quantum tunnelling. To check this hypothesis, 2D deuteron NMR and 87Rb and 2H SLR measurements were carried out at low temperatures. With site-specific NMR measurements, it was also hoped to identify the microscopic nature of the "two-level" states which determine the low T glassy properties of these systems. 

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