Reduced Sensitivity

The odor detection-threshold values of organic compounds, water, and mineral oil have been determined by different investigators (Table 2 and 3) and may vary by as much as 1000, depending on the test methods, because human senses are not invariable in their sensitivity. Human senses are subject to adaption, ie, reduced sensitivity after prolonged response to a stimulus, and habituation, ie, reduced attention to monotonous stimulation. The values give approximate magnitudes and are significant when the same techiriques for evaluation are used. Since 1952, the chemistry of odorous materials has been the subject of intense research (43). Many new compounds have been identified in natural products (37—40,42,44—50) and find use in flavors. 

The almost exclusive use of tria2oles foi ceieal powdery mildew control up to the mid-1980s has resulted in a shift in E.Tysiphe populations toward reduced sensitivity or resistance to this class of fungicides. However, use has continued because field performance of most tria2oles has remained adequate (43). Decreased a2ole sensitivity in the population to a2oles has also been noted. 

Pharmacogenetics the responses to dmgs may be significantiy different according to heritable factors that can modulate pharmacodynamic or pharmacogenetic factors (118). Atypical cholinesterase occurs in about 1 in 2000 Caucasians and is associated with a markedly reduced sensitivity to hydrolysis of the muscle-relaxant cholinesterase. Similarly, the reduced sensitivity to the anticoagulant warfarin is associated with a reduced receptor affinity. 

Resins filled with ground limestone to levels of 80% by weight are useful in soHd cast products. The fillers reduce sensitivity to brittle fracture and improve modulus, but have Httle effect on general strength properties (Table 8). 

Porous bron2e and iron, a variety of plastics, carbon—graphite, wood, and mbber are widely used in dry sliding or under conditions of sparse lubrication. These materials have commonly allowed design simplifications, freedom from regular maintenance, reduced sensitivity to contamination, and good performance at low speeds and with intermittent lubrication. Although these materials are often used dry or with sparse lubrication, performance normally improves the closer the approach to full-film lubrication. 

Let us now return to the question of solvolysis and how it relates to the stracture under stable-ion conditions. To relate the structural data to solvolysis conditions, the primary issues that must be considered are the extent of solvent participation in the transition state and the nature of solvation of the cationic intermediate. The extent of solvent participation has been probed by comparison of solvolysis characteristics in trifluoroacetic acid with the solvolysis in acetic acid. The exo endo reactivity ratio in trifluoroacetic acid is 1120 1, compared to 280 1 in acetic acid. Whereas the endo isomer shows solvent sensitivity typical of normal secondary tosylates, the exx> isomer reveals a reduced sensitivity. This indicates that the transition state for solvolysis of the exo isomer possesses a greater degree of charge dispersal, which would be consistent with a bridged structure. This fact, along with the rate enhancement of the exo isomer, indicates that the c participation commences prior to the transition state being attained, so that it can be concluded that bridging is a characteristic of the solvolysis intermediate, as well as of the stable-ion structure. ... 

Note Aldoses do not react or only react with greatly reduced sensitivity. The reagent can be employed with silica gel, kieselguhr and Si 50 000 layers. Paraffin-impregnated silica gel layers may also be employed [8]. 

Gready reduced sensitivity to molecular weight change. 

The standard modern instrument however is the electronic balance, which provides convenience in weighing coupled with much greater freedom from mechanical failure, and greatly reduced sensitivity to vibration. The operations of selecting and removing weights, smooth release of balance beam and pan... 

If the reaction time for the TBDMS derivatives is not long enough, a mixture of mono- and di-TBDMS derivatives is observed, resulting in more than one GC peak and thus reduced sensitivity. 

Double-base compns are primarily NC which is plasticized with NG. Additives are required to reduce sensitivity to expin, flash, and smoke production. Some typical compns are listed in Table 2 (Refs 27, 32a)... 

Respiratory-depressant effects on respiratory rate (caused by a reduced sensitivity of the respiratory center to carbon dioxide)... 

It has been reported that LAS/AOS combinations exhibit favorable synergy in detergency performance and a reduced sensitivity to water hardness [49]. 

A completely blocked probe is easy to diagnose but of more concern is partial blocking which is not always obvious. Not only will this give reduced sensitivity with less eluate reaching the mass spectrometer, but, if the build-up of material in the pinhole is not even, a non-axial spray is produced which leads to a reduction in sensitivity and changes in the appearance of the mass spectra being generated. 

Partaledis JA, Yamaguchi K, Tisdale M, Blair EE, Falcione C, Maschera B, Myers RE, Pazhanisamy S, Futer O, CuHinan AB et al (1995) In vitro selection and characterization of human immunodeficiency virus type 1 (HIV-1) isolates with reduced sensitivity to hydrox-yethylamino sulfonamide inhibitors of HIV-1 aspartyl protease. J Virol 69 5228-5235 Patick AK (2006) Rhinovirus chemotherapy. Antiviral Res 71 391-396... 

Hagiwara T, Kijima-Suda I, Ido T, Ohrui H, Tomita K (1994) Inhibition of bacterial and viral sialidases by 3-fluoro-V-acetyIneuraminic acid, Carbohydr Res 263 167-172 Haskell TH, Peterson FE, Watson D, Plessas NR, Culbertson T (1970) Neuraminidase inhibition and viral chemotherapy, J Med Chem 13 697-704 Hatakeyama S, Sugaya N, Ito M, Yamazaki M, Ichikawa M, Kimura K, Kiso M, Shimizu H, Kawakami C, Koike K, Mitamura K, Kawaoka Y (2007) Emergence of influenza B viruses with reduced sensitivity to neuraminidase inhibitors, JAMA 297 1435-1442 Hay AJ (1992) The action of adamantanamines against influenza A viruses inhibition of the M2 ion channel protein, Semin Virol 3 21-30... 

Accurate calibration of pulse lengths is essential for the success of most 2D NMR experiments. Wide variations (>20%) in the setting of pulse lengths may significantly reduce sensitivity and may lead to the appearance of artifact signals. In some experiments, such as inverse NMR experiments, accurately set pulse lengths are even more critical for successful outcomes. 

The original observation of long-term depletions of DA in the rhesus monkey was made during a study of the development of tolerance to the effects of daily injections of METH (Fischman and Schuster 1977). In this study, it was found that behavioral tolerance to METH on a differential-reinforcement-of-low-rate (DRL) task persisted long after the repeated METH regimen. In a similar study conducted later, monkeys treated with repeated METH showed reduced sensitivity to apomorphine and increased... 

Electrochemically active compounds can be evaluated using a potentiometer to generate a cyclic voltammogram for the analyte. Cyclic voltammetry will allow the analyst to determine whether the compound can be oxidized or reduced, to choose the appropriate potential to use in the electrochemical detector, and to establish whether oxidation or reduction is irreversible. Irreversible oxidation or reduction of the analyte could be predictive of problems with electrode poisoning and reduced sensitivity of the electrochemical detector over time. Turberg et al. used EC detection at an applied potential of -1-600 mV to analyze for ractopamine. 

Column/injector maintenance. The use of a guard column, in addition to scheduled injector maintenance, provides significantly improved GC performance. Loss of performance manifests itself in poor peak shape and reduced sensitivity. This is particularly noticeable with atrazine but also with the other analytes. Maintenance should include removal of a 30-60 cm section of the guard column and replacement of the... 

A triple-quadrupole mass spectrometer with an electrospray interface is recommended for achieving the best sensitivity and selectivity in the quantitative determination of sulfonylurea herbicides. Ion trap mass spectrometers may also be used, but reduced sensitivity may be observed, in addition to more severe matrix suppression due to the increased need for sample concentration or to the space charge effect. Also, we have observed that two parent to daughter transitions cannot be obtained for some of the sulfonylurea compounds when ion traps are used in the MS/MS mode. Most electrospray LC/MS and LC/MS/MS analyses of sulfonylureas have been done in the positive ion mode with acidic HPLC mobile phases. The formation of (M - - H)+ ions in solution and in the gas phase under these conditions is favorable, and fragmentation or formation of undesirable adducts can easily be minimized. Owing to the acid-base nature of these molecules, negative ionization can also be used, with the formation of (M - H) ions at mobile phase pH values of approximately 5-7, but the sensitivity is often reduced as compared with the positive ion mode. 

---