CONTENTS 10 Physical Methods

To analy2e fatty amines, both wet and instmmental methods of analysis are used. Wet methods routinely used are total amine value (ASTM Method D2073) combining weight or neutralization equivalent primary, secondary, and tertiary amine content (ASTM Method D2083) moisture, Kad-Fischer (ASTM Method D2072) and iodine value, measure of unsaturation (ASTM Method D2075). These provide important information on physical and chemical characteristics of the amine products used in various appHcation areas (8,76,81). In addition to the ASTM methods available, the American Oil Chemists Society has developed methods of analysis for fatty amines (82). 

When the chemical-imbalance theory was introduced more than 40 years ago, the main evidence in favour of it was the contention that antidepressants, which were thought to increase the availability of serotonin and/or other neurotransmitters in the brain, seemed to be effective in the treatment of depression. As Alec Coppen wrote in 1967, one of the most cogent reasons for believing that there is a biochemical basis for depression or mania is the astonishing success of physical methods of treatment of these conditions. 26 The situation has not changed very much since then. People still cite the supposed effectiveness of antidepressants as fundamental support for the chemical-imbalance hypothesis. This theory, they say, is supported by the indisputable therapeutic efficacy of these drugs .27... 

A hindrance to the elucidation of membrane structure is, of course, the material itself. Membranes are rather intractable lipoprotein systems. Their lipid, protein, and carbohydrate contents are variable both quantitatively and qualitatively since they cannot be crystallized, a detailed analysis by x-ray diffraction is impossible, and since they do not form solutions, the use of hydrodynamic or light-scattering techniques is quite limited. Electron microscopy has been the major physical method, but it is becoming increasingly clear that the electron microscope, at least at present, is incapable by itself of clarifying membrane structure on the molecular level (47). Despite an extensive literature, there is no general... 

The fluorescence of ribonuclease solutions has been studied extensively by Cowgill. The absence of tryptophan permits the tyrosine fluorescence to be observed. The tyrosine fluorescence of RNase is very low in comparison with the maximum expected from its tyrosine content. All methods of denaturing RNase lead to an increase in fluorescence. Transitions, as indicated by the pattern of fluorescence change vs. denaturant concentration, are about the same as those indicated by other physical techniques [see, e.g., Gaily and Edelman (305) ]. 

Describe a physical method that can be used to estimate the base composition of DNA. Describe the data obtained with two DNA samples One with high G-C content and another with high A-T content (Assume that the concentration of the samples is equal.)... 

Physical Methods Physical methods include mechanical disruption by milling, homogenization, or ultrasonication. Typical high-speed bead mills are composed of a grinding chamber filled with glass or steel beads which are agitated with disks or impellers mounted on a motor-driven shaft. The efficiency of cell disruption in a bead mill depends on the concentration of the cells, the amount and size of beads, and the type and rotation speed of the agitator. The optimum wet solid content for the cell suspension for a bead mill is typically somewhere between 30 percent to 60 percent by volume. The amount of beads in the chamber is 70 percent to 90 percent by... 

Figure 19. Calibration curve for the determination of the average size of a graphene unit in nanocrystalline carbon from its content in heteroatoms. The size range seen by physical methods stems from direct electron microscopic observation, from scattering models of X-ray diffraction and from NMR.

Both physical and chemical methods or a combination of both have been used to estimate the phenolic hydroxyl content of lignin (Adler 1977). Common physical methods include potentiometric and conductometric titration (Chap. 7.5) ionization UV spectroscopy (Chap. 5.1), and NMR spectroscopy (Chap. 5.3). 

It is important to realize that there is a delay of about six months between the time a journal article appears and the time its abstract is printed in Chemical Abstracts or Physics Abstracts. This is not surprising when you consider that CA presents abstracts from 14,000 journals published in 150 countries. In addition, there is a delay after an abstract volume is complete before the subject and substance indexes become available. Thus it is wise to check the most recent literature by scanning the title pages of likely journals. A convenient method for doing this is to scan through Current Contents Physical, Chemical, and Earth Sciences, a weekly compilation of the latest tables of contents for many journals. A list of specific journals of greatest interest to physical chemists is given in Appendix E. 

The properties that negatively affect bio-oil fuel qualify are foremost low heating value, incompatibility with conventional fuels, solids content, high viscosity, and chemical instability. The heating value can be significantly increased, but it requires extensive changes to the chemical structure of bio-oils, which is technically feasible but not economic. The other undesired characteristics can be improved using simpler, physical methods. Both options are reviewed below. 

Determination of the lycopene content in tomatoes and some tomato products can be carried out by physical and chemical methods. Physical methods depend on the relation of color parameters to lycopene concentration in the samples. In chemical analysis, lycopene is extracted from the tomato fruits and products and quantified. 

Various technologies have been used to measure plasma lipids and lipoproteins and lipoprotein subfractions, including enzymatic, immunochemical, and chemical precipitation reagents, and physical methods, such as ultracentrifugation, electrophoresis, column chromatography, and others. Such methods have been reviewed extensively. As mentioned earlier, however, the cholesterol content of any particular lipoprotein class can vaiy somewhat from individual to individual. Moreover, although different methods of lipoprotein separation may produce similar lipoprotein fractions, they usually do not produce identical fractions, giving rise to systematic biases between methods that purport to measure the same component. The present discussion focuses primarily on methods and procedures commonly used in clinical practice for lipid and lipoprotein measurements. 

As mentioned in Sect. 2.2.1.3 [33], we proposed that a trace amount of /3-phase, induced by the use of an electron-deficient moiety (TAZ) as an end-capper for PFO, can improve device performance to give a better blue purity. Following the idea of /3-phase formation, we further proposed a novel simple physical method to generate /3-phase at a content of up to 1.32% in a PFO film spin-coated on a substrate (the remaining part is amorphous phase) by immersing it in a mixed solvent/non-solvent (tetrahydrofuran/methanol) for a few seconds [45]. The device based on PFO with 1.32% / -phase (ITO/PEDOT PSS/emitting polymer/CsF/Al) has a dramatically enhanced device efficiency and an improved blue-color purity of 3.85 cd A-1 (external quantum efficiency, 3.33%) and CIE of x+y = 0.283 (less than the limit of... 

In the physical methods the mixing of an additive, which differs in temperature, concentration or density (refraction index) from the vessel contents, is foUowed by measuring the temperature, the electrical conductivity, the pH-value or by Schlieren optics. Other methods worthy of mention are ... 

Neither of the two physical methods is significantly affected by relative changes in albumin and y-globulin contents (R20, R30), but the extent of lipoid interference has not been clearly defined (D16). Comparative figures for serum proteins in children, obtained by the copper sulfate method, the Hitachi microrefractometer, and a biuret method (J12), are shown in Table 6, from which it is apparent that neither of the physical methods is appreciably affected by neutral-fat turbidity or intense icterus. Sunderman (855) also considered the relationship between serum protein concentration and refractivity not to be influenced by the cholesterol content of the serum. Nevertheless refractometry frequently overestimates protein in serum from patients with primary nephrotic syndrome (Table 6). 

The object of NMR spectroscopy on proteins, nucleic acids and other complex polymers is to obtain information on their structure and dynamics. Assignment of individual spectral lines discussed in the preceding section is a prerequisite to one s ability to decipher this information. Actually to do so it is also necessary to understand the nature of the structural and dynamic information inherent in each feature of the spectrum. And one is rightfully asked is the nature of this information such that the result will be worth the labor required to obtain a significant set of assignments An important part of the answer to this question is that NMR is the ONLY physical method which can provide any information at essentially atomic resolution on the structure and dynamics of macromolecules in solution, as well as in the solid state. Whatever the limits of this information, it is better than none. Knowledge of these limits, as well as of the nature of spectroscopic information, is nevertheless necessary, both to realize expectations and to avoid conclusions that go beyond the capabilities of the method. The information content and its limits can be meaningfully discussed for each measured parameter separately, and the common features summarized at the end. 

Micrographic examination verifies that the addition of 10% sulfur to asphalt produces a monophasic product. The physical methods for determining these solubilities have been completed by chemical determinations of the sulfur content in each phase total sulfur dispersed and sulfur content of each part of the bituminous phase (maltenes, asphal-... 

With all of the preceding distressing sources of error and limitations, thermal analysis has several incomparable advantages (1). Being a physical method, it may be applied without any knowledge concerning the chemical properties of the main component or the contaminants of the sample. It is sensitive, although not equally sensitive, to all types of contaminants. When the sample may be considered as a binary system, it certainly permits quantitative determination of its content of contaminants. 

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