Identification causes

Plawat D, Shah P H and Plawat V, Objectionable faults in rotor spun cotton yarns their identification, causes of generation and remedies , 41st Joint Technological Conference, Resume of Papers, 2000, Mumbai, Bombay Textile Research Association, 19-25. 

It is well known that the electron-impact ionization mass spectrum contains both the parent and fragment ions. The observed fragmentation pattern can be usefiil in identifying the parent molecule. This ion fragmentation also occurs with mass spectrometric detection of reaction products and can cause problems with identification of the products. This problem can be exacerbated in the mass spectrometric detection of reaction products because diese internally excited molecules can have very different fragmentation patterns than themial molecules. The parent molecules associated with the various fragment ions can usually be sorted out by comparison of the angular distributions of the detected ions [8]. 

The first step in designing a new compound is to find compounds that have even a slight amount of usefulness for the intended purpose. These are called lead compounds. Once such compounds are identified, the problem becomes one of refinement. Computational techniques are a fairly minor part of finding lead compounds. The use of computer-based techniques for lead compound identification is usually limited to searching databases for compounds similar to known lead compounds or known to treat diseases with similar causes or symptoms. 

In earlier chapters we have been concerned with the identification of the effective electrophile in nitrations carried out under various conditions. We have seen that very commonly the nitronium ion is the electrophile, though dinitrogen pentoxide seems capable of assuming this role. We now consider how the electrophile, specifically the nitronium ion, reacts with the aromatic compound to cause nitration. 

The arrest of deterioration and the prevention of its recurrence has higher priority than restoration. Thus, identification of the causes of a problem and the design of measures to stabilize and consoHdate the object are primary considerations. Removal of the symptoms and restoration of the visual appearance comes only after the physical iategrity has beea safeguarded. 

Raman spectroscopy, long used for quaHtative analysis, has been revitalized by the availabiHty of laser sources. Raman spectroscopy is based on scattering of light with an accompanying shift in frequency. The amount by which the frequency is shifted is characteristic of the molecules that cause the scattering. Hence, measurement of the frequency shift can lead to identification of the material. 

Benzoates. The selective debenzoylation of sucrose octabenzoate [2425-84-5] using isopropylamine in the absence of solvents caused deacylation in the furanose ring to give 2,3,4,6,1/3/6 -hepta- and 2,3,4,6,1/6 -hexa-O-benzoyl-sucroses in 24.1 and 25.4% after 21 and 80 hours, respectively (54). The unambiguous assignment of partially benzoylated sucrose derivatives was accompHshed by specific isotopic labeling techniques (54). Identification of any benzoylated sucrose derivative can thus be achieved by comparison of its C-nmr carbonyl carbon resonances with those of the assigned octabenzoate derivative after benzoylation with 10 atom % benzoyl—carbonyl chloride in pyridine. 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

This is a brief summary of NFPA 704 which addresses hazards that maybe caused by shoii-term, acute exposure to a material during handling under conditions of fire, spill, or similar emergencies. This standard provides a simple, easily recognized, easily understood system of markings. The objective is to provide on-the-spot identification of hazardous materials. 

Identification and quantitative estimation of common-cause failures are general problems in fault tree analysis. Boolean approaches are generally better smted to mathematically handle common-cause failures. 

The activities under interpretation are divided into four categories. Troubleshooting is a procedure to identify and solve a problem in the unit. Hypothesized causes for the observed problems are developed and then tested with appropriate measurements or identification of changes in operating conditions. 

These procedures are not mutually exclusive and are divided here as a matter of convenience for discussion. The identification, measurement treatment, and interpretation are tvpicaUy embodied into a single effort with testing and retesting as analysts search for the cause of the observed symptoms. 

The current and past operation should be compared so that the timing of the observed problems is estabhshed. The possible causes (hypotheses) can be compared against the measurements found on the log sheets. The number of possible causes can then be reduced. When the quantity or quahty or measurements is insufficient to further reduce the set of causes, additional measurements are required. These may require special instruments (e.g., gamma-ray scanning) not routinely usedin the plant. Alternative operating conmtions may also be required to further reduce the number of causes. As part of the problem identification, it is alwavs important to look for measurements that are inconsistent with the proposed explanation. They will be more informative than the ones justifying the hypothesized cause. Ultimately, with appropriate additional measurements, the cause can be identified. This is not an exact science and, as stated above, relies heavily upon the communication, technical, and investigative skills of analysts. 

Intensive application of pesticides and polymers in agriculture and industry cause the increase of number of toxic organic substances, which circulate in an environment, and constantly complicates their disclosure, identification and quantitative detection. 

Identification. If accessible, defects from burnthrough may be visually identified as fused holes in the tube wall. Various nondestructive testing techniques, such as radiography and ultrasonics, may also detect this defect. The defect generally causes leakage soon after affected equipment is placed in service. 

Identification. Defects in welds due to laminations may be difficult to identify based solely on a visual examination. Typically, cracks from welding laminated metal cause jagged, stepwise tears in the base metal. The crack may propagate into the weld itself. 

Identification. Weld decay characteristically produces distinct, narrow zones of disintegration immediately adjacent and parallel to the weldment (Fig. 15.4). Attack will occur on either side of the weld. The weld itself and surrounding metal will be unattacked. The corroded area frequently has a granular or sugary appearance and feel. This is due to corrosion along the boundaries of individual grains that causes them to be released from the metal surface. Affected metal may have lost its metallic ring. 

The most useful application of ISS is in the detection and identification of sur-fece contamination, which is one of the major causes of product failures and problems in product development. The surface composition of a solid material is almost always different than its bulk. Therefore, surface chemistry is usually the study of unknown surfaces of solid materials. To better understand the concept of surface analysis, which is used very loosely among many scientists, we must first establish a definition for that term. This is particularly Important when considering ISS... 

Provision of operating instructions and procedures. These should eliminate confusion and provide continuity on, e.g., shift changeover. EiTors in identification of valves, pumps, pipes, storage tanks, and the sequence in which they are to be operated is a common cause of accidents, e.g. on staff changeovers. 

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