Repeated usage

The main reason MDMA has little abuse potential is that it exhibits tachyphylaxis —a rapid buildup of tolerance so that repeated usage within a short space of time leads to the loss of desired effects. In contrast to its "heart-opening" and stress-reducing qualities, this substance, if taken within a few days of a prior ingestion, tends paradoxically to produce an increase in stress and many of the least desirable characteristics of amphetamine overdosage. Very few people are attracted to such effects, and even those who are could achieve them more cheaply via other substances. 

Ascorbic acid (1) is most commonly used for testing the performance of electrodes in redox systems. Thus, a Ag-Ag ascorbate selective electrode was constructed with view to use it for vitamin C determination. Its reproducibility and stability was satisfactory and ascorbate ion concentration could be determined in neutral, alkaline and alcoholic media" . A voltametric study was carried out for the evaluation of graphite-epoxy composite (GEC) electrodes for use in the determination of ascorbic acid and hydroquinone. They were compared with mercury and CPE in similar operating conditions of pH and supporting electrolytes. Like all redox electrodes, also GEC electrodes deteriorate on exposure to air or after repeated usage, and the surface had to be renewed for activation. GEC electrodes were found to be adequate for redox system analyses"". The electrocatalytic oxidation of 1 is an amplification method for determination of specific miRNA strands using the An biosensor described in Table 1 . 

Polycarbophil polymers have a long history of safe and effective use in topical gels, creams, lotions, and ointments. They have been shown to have extremely low irritancy properties and are nonsensitizing with repeated usage. 

After 9 hr nearly equal amounts of butyric and isobutyric acid are formed (90-99% yield). The major by-product formed is propyl acetate, especially at higher temperatures. At 250°C, ethylene in an acetic acid solvent, gives an equimolar mixture of propionic anhydride and the mixed anhydride of acetic and propionic acid. The activity of the Pd on carbon catalyst drops slowly through repeated usage owing to slight but continuous solubilization of the palladium. The problem of long-term activity remains unsolved. 

R)-l-PhenylpropanoL In this preparative example, the repeated usage of a 6,6 -bis(tridecafluorooctyl)silylated BINOL in catalyzing the reaction of PhCHO with EtiZn has been demonstrated. 

Other material specimens, once carefully calibrated by one of the primary methods explained above, can be used as a secondary standard. The material for such a secondary standard should be easy to handle, give a moderately strong scattering intensity, and remain unaltered over a long period of time under repeated usage. Polyethylene and glassy carbon have been used for this purpose. 

In another study (114), three different immobilization methods were evaluated for the detection of E. coli using an antibody coated crystal. The best results were obtained with a protein A coated method, and a response for 10 - lO cells 1 ml of E. coli K12 and other antigens of the Enterobacteriaceae family was observed. Repeated usage of the coated crystal by removing the bound antigen with urea or glycine HCl buffer (pH 2.6) was not very successful. 

Fig. 1 depicts the results for the repeated usage of the immobilized catalysts I and II. The selectivity for 4-hydroxybenzoic acid remains constant at 100 %, and the yield is always larger than 80 mole%. Thus, the immobilized 3-CyD catalysts are intact during the reaction and also in the recovery procedure. 

The repeated usage of free 3-CyD catalyst, which is not immobilized, is also examined. After the reaction, the reaction mixture is acidified with hydrochloric acid and 3-CyD is separated by centrifugation. In the successive three repeated usage, the selectivity for 4-hydroxybenzoic acid is 100 %. In the fourth, the fifth, and the sixth runs, however,. the selectivity decreases to 85, 76, and 60 %, respectively. 

Easy separation of the catalysts from the products and successful repeated usage of them are certainly advantages for the immobilized 3-CyD catalysts over free 3 CyD catalyst from the viewpoint of practical... 

Figure 1. Selectivity and yield for the formation of 4-hydroxybenzoic acid on the repeated usage of the immobilized 3-CyD catalysts in the reaction of phenol and carbon tetrachloride in 20 wt,-% aqueous sodium hydroxide solution (O > ) the immobilized catalyst I ( IZI, H) the immobilized catalyst II. The separation of the catalyst was carried out by centrifugation, and the recovered catalyst was charged to aqueous sodium hydroxide solution together with phenol and carbon tetrachloride in the following run.

MOFs with even higher surface area and increased gas adsorption have been synthesized (as shown in Table 8.1), the weak coordination in MOFs makes them rather unstable under harsh conditions and makes them incomparable with PAFs for long time storage and repeated usage. 

The system should be easy to learn, intuitive, helpful, and encourage repeat usage. 

Darabi et al. introduced a different, facile, and economic approach to the preparation of quinoxalines and pyrido[2,3-l)]pyrazines with aryl substituents at the 2- and/or 3-positions by employing recyclable sihca-supported bismuth(III) chloride, providing the desired products in good-to-excellent yields (Scheme 59) (13JOMC170). A minor decrease in the activity of this new heterogeneous Lewis acid catalyst upon repeated usage was noted. A variety of substituents were tolerated under these reaction conditions. 

The suitability of poly(ethylene terephthalate) as an arterial prosthetic material has been reviewed and collected clinical experiences of its role in the correction of transposition of the great arteries have been reported together with cases of its failure in arterial prostheses. The suitability of polytetrafluoroethylene e.g. Goretex) has been similarly considered. Vascular access for chronic haemodialysis presents particular problems associated with the need for repeated usage. 

Regardless of the type of activity, a man and his intellect is the most significant element of every system. Thus, while discussing the availability of weapon system, we cannot ignore the problem of effective gathering, processing and repeated usage of the experiences of specialists in this field. 

Dependability is a measure of the degree to which an item is operable and capable of performing its required function at any (random) time during a specified mission profile, given that the item is available at mission start. Examples of dependability measures are availability, interoperability, compatibility, reliability, repeatability, usage rates, vulnerability, survivability, penetrability, durability, mobility, flexibility, and reparability. 

The abrasion resistance of rayon is fair, and abrasion of rayon fabrics becomes noticeable after repeated usage and launderings. The rayons are resistant to pill formation. Rayon fabrics wrinkle easily and without chemical treatment show poor crease recovery and crease retention. Durable press and wash-and-wear finishes tend to cause less degradation of rayon than found with cotton. Rayon possesses excellent moisture absorbency characteristics, but the weaker rayons swell and deform somewhat in the presence of moisture. 

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