Force free environment

One of the problems faced by quantum chemistry is that it is based on a theory borrowed from physics. It therefore is important to note that a given variable or concept may be interpreted very differently in physical and chemical context, respectively. The physicist who is interested in the motion of a molecule in a force-free environment, treats it as a mass point, without any loss of generality. Such a molecule is of no interest to the chemist who studies the interaction of a molecule with its environment. In chemical context the size and shape of the molecule, left undefined in theoretical physics, must be taken into account. The interaction between mass points can simply not account for the observed behaviour of chemical substances. 

A comparison of the present theoretical model with the experimental observations of Okajima and Kumagai (8) is shown in Figure 7 for the combustion of a 1300-fi ethyl alcohol droplet under the influence of weak forced convection as a result of relative motion with respect to the gas phase in a gravity-free environment not disturbed by free convection. For these experiments Okajima and Kumagai (8) used a freely falling chamber within which a free droplet was combusted while the droplet moved at a relative velocity of 1.29 cm/sec in a standard air atmosphere with an initial temperature of 300 K. Since the droplet was spark-ignited... 

Airborne particles are one important source of sample contamination. Therefore, the laboratory must enable samples to be treated and measurements to be carried out in a satisfactorily dust-free environment. Improvements in existing laboratories can be obtained by installing a laminar flow hood, but optimal improvement involves the design of clean rooms in which air is pumped through a dust-stop prefilter and then forced by a blower through an absolute filter inside the working... 

Use your creativity effectively. Defer judgment be succinct list 50 ideas in 5 minutes create a risk-free environment encourage free and forced association of ideas piggy back on previous ideas use triggers, such as those listed below, to maintain the flow of ideas don t be discouraged, in the last two minutes of a ten minute brainstorming session, over 85 % of the ideas are not practical. But, spend time identi-... 

Several different kinds of noncovalent interactions are of vital importance in protein structure. Hydrogen bonds, hydrophobic interactions, electrostatic bonds, and van der Waals forces are all noncovalent in nature, yet are extremely important influences on protein conformations. The stabilization free energies afforded by each of these interactions may be highly dependent on the local environment within the protein, but certain generalizations can still be made. 

To effect a dispersion of a solid in a liquid, mechanical work must be performed, and the forces and stresses imposed on the aggregates, tlirough the liquid, cause them to break up into the smaller units. Once dispersed, the particles in their new environment are free to move about and form new associations, differing, however, in important respects from the original aggregations. 

With further understanding how molecular rotors interact with their environment and with application-specific chemical modifications, a more widespread use of molecular rotors in biological and chemical studies can be expected. Ratiometric dyes and lifetime imaging will enable accurate viscosity measurements in cells where concentration gradients exist. The examination of polymerization dynamics benefits from the use of molecular rotors because of their real-time response rates. Presently, the reaction may force the reporters into specific areas of the polymer matrix, for example, into water pockets, but targeted molecular rotors that integrate with the matrix could prevent this behavior. With their relationship to free volume, the field of fluid dynamics can benefit from molecular rotors, because the applicability of viscosity models (DSE, Gierer-Wirtz, free volume, and WLF models) can be elucidated. Lastly, an important field of development is the surface-immobilization of molecular rotors, which promises new solid-state sensors for microviscosity [145]. 

---