Physical dependence, difference from

The barbiturates also cause a physical dependence different from the opioid narcotics. In an individual addicted to barbiturates, the barbiturates should not be withdrawn abruptly but, rather, tapered slowly. Sudden withdrawal of the barbiturates can precipitate extreme agitation and grand mal seizures. This can lead to a spasm of the respiratory musculature, producing impaired respiration, cyanosis, and possibly, death (42). As a rule, drug dependence is followed by tolerance, in which increasing doses are required to obtain the same pharmacological effect. Because barbiturates cause tolerance and, often, dependence, their use as a hypnotic rarely is justified. 

In contrast, we did not find these concentration-dependent qualitative changes when activation occurred in intact cellular systems (16). We examined the adducts formed in mouse embryo cells in culture and in mouse skin ijri vivo over 40- and 100-fold DMBA concentration ranges, respectively, and found quantitative, but no qualitative, changes in binding (16). At all concentrations, activation appeared to be through the bay region dihydrodiol epoxide pathway. The cellular systems are physically very different from the homogenate systems and it is difficult to... 

Physical characterization differs from chemical assay in that frequently a unique value does not exist. The determined amount of copper in an ore sample should not depend upon the analytical procedure employed whereas the measured size distribution is method dependent. Only homogeneous, spherical particles have an unambiguous size. 

In this section, methods of separation and purification which depend on the partitioning of material between two phases will be considered. If one phase is a solid, the method is called adsorption, and if the process is carried out in such a way as to multiply the efficiency of a single adsorption, it is commonly called chroviatography. If the material is distributed between two liquid phases or a gas and a liquid phase, the process is called extraction. These methods are particularly valuable for separating mixtures, since they discriminate between compounds on the basis of physical properties different from those which were important for the methods previously described. Thus, two solid compounds which cannot be separated conveniently by recrystallization because of their very similar solubility characteristics may often be separated by chromatography. 

Therefore, the spontaneous formation of the equilibrium supramolecular system structure, which provides its kinetic curing stability, and does not depend on the prehistory of the sample, occurs after the completion of swelling, within the exposure period 0contact with the liquid phase. During this period, local molecule concentration redistribution and spontaneous supramolecular structure elements formation (cybotactic groupings and associates) occur in the macroscopic sample volume. The characteristics of these elements (lifetime, correlation radius, strength of physical bonds) differ from the similar indices or coefficients in the initial oligomer and in the polymer-oligomer film, which is in contact with liquid. 

DUactide (5) exists as three stereoisomers, depending on the configurations of the lactic acid monomer used. The enantiomeric forms whereia the methyl groups are cis are formed from two identical lactic acid molecules, D- or L-, whereas the dilactide formed from a racemic mixture of lactic acid is the opticaUy iaactive meso form, with methyl groups trans. The physical properties of the enantiomeric dilactide differ from those of the meso form (6), as do the properties of the polymers and copolymers produced from the respective dilactide (23,24). 

Purification. The method used to recover the desired alkylphenol product from the reactor output is highly dependent on the downstream use of the product and the physical properties of the alkylphenol. The downstream uses vary enormously some require no refining of the alkylphenol feedstock others require very high purity materials. Physical property differences affect both the basic type of process used for recovery and the operating conditions used within that process. 

In the United States, a number of physical tests are performed on siUcon carbide using standard AGA-approved methods, including particle size (sieve) analysis, bulk density, capillarity (wettabiUty), friabiUty, and sedimentation. Specifications for particle size depend on the use for example, coated abrasive requirements (134) are different from the requirements for general industrial abrasives. In Europe and Japan, requirements are again set by ISO and JSA, respectively. Standards for industrial grain are approximately the same as in the United States, but sizing standards are different for both coated abrasives and powders. 

Fig. 22. Nomialized pull-off energy measured for polyethylene-polyethylene contact measured using the SFA. (a) P versus rate of crack propagation for PE-PE contact. Change in the rate of separation does not seem to affect the measured pull-off force, (b) Normalized pull-off energy, Pn as a function of contact time for PE-PE contact. At shorter contact times, P does not significantly depend on contact time. However, as the surfaces remain in contact for long times, the pull-off energy increases with time. In seinicrystalline PE, the crystalline domains act as physical crosslinks for the relatively mobile amorphous domains. These amorphous domains can interdiffuse across the interface and thereby increase the adhesion of the interface. This time dependence of the adhesion strength is different from viscoelastic behavior in the sense that it is independent of rate of crack propagation.

Preparation research of SWCNT was also put forth by lijima and his co-worker [3]. The structure of SWCNT consists of an enrolled graphene to form a tube without seam. The length and diameter depend on the kinds of the metal catalyst used in the synthesis. The maximum length is several jim and the diameter varies from 1 to 3 nm. The thinnest diameter is about the same as that of Cgo (i.e., ca. 0.7 nm). The structure and characteristics of SWCNT are apparently different from those of MWCNT and rather near to fullerenes. Hence novel physical properties of SWCNT as the one-dimensional material between molecule and bulk are expected. On the other hand, the physical property of MWCNT is almost similar to that of graphite used as bulk [6c]. 

The specific requirement for a vibration to give rise to an absorption in the infrared spectrum is that there should be a change in the dipole moment as that vibration occurs. In practice, this means that vibrations which are not centrosymmetric are the ones of interest, and since the symmetry properties of a molecule in the solid state may be different from those of the same molecule in solution, the presence of bands may depend on the physical state of the specimen. This may be an important phenomenon in applying infrared spectroscopy to the study of AB cements. 

In order to study the attraction of masses of the earth which moves around the axis of rotation, it seems appropriate to use the field g, which depends on the distribution of masses and the angular velocity, as well as coordinates of the point. Besides, it has a physical meaning of the reaction force per unit mass. However, it has one very serious shortcoming, namely, unlike the attraction force it is directed outward. In other words, it differs strongly from the attraction field, in spite of the fact that the contribution of rotation is extremely small. To overcome this problem we introduce the gravitational field g which differs from the reaction field in direction only ... 

Although the net results obtained above for the particle in a box are physically the same, the mathematieal consequences are quite different. From Fig. 4b it can be seen that the wavefunction is either even or odd, depending on the parity of n. Specifically, ifrtt(x) = iM— ) where the plus sign is appropriate when n is odd and the minus sign when n is even. As Eq. (70) contains the sine of the sum of two terms, it can be rewritten in die form... 

---