Need for more

The situation is very much poorer for stmctured rather than random packings, in that hardly any data on Hq and have been pubHshed. Based on a mechanistic model for mass transfer, a way to estimate HETP values for stmctured packings in distillation columns has been proposed (91), yet there is a clear need for more experimental data in this area. 

The products have the characteristic lemon odor of citral and also have greater odor strength and chemical stabiUty than citral. As the need for more stable citms-like fragrances for use in bleach developed, other nitrile compounds have been made available commercially. CitroneUyl nitrile is made from citroneUal dimethyloctanenitrile is produced from dimethyloctanal by the oximation method. 

Even when a total system analysis is unnecessai y, the methodology of mathematical modeling is useful, because by considering each component of a system as a block of a flow sheet, the interrelationships become much clearer. Additional alternatives often become apparent, as does the need for more equipment-performance data. 

Control room sited closer to the batch process due to need for more operator interaction with batch processes. Infiltration of flammable/toxic release from outside. Possible overpressure from external explosion. 

As polymer scientists continue to investigate the atomic structure and physical properties of polymers, the need for more accurate models to describe various experi-... 

There is still need for more detailed investigation of atomie jump proeesses and of interaetion of ordering and deformation. Aside of this, three future aspects seem to be of main importanee ... 

Of course in solution such an intermediate, if formed at all, would be very shortlived and could be the species responsible for the side reaction which produces some oligomerization of the furan ring. However, any interpretation of the mechanism of oligomerization must be regarded at this point as highly speculative since there is an obvious need for more experimental evidence, particularly concerning the structure of the products. 

Finally, although the basic development and nature of boiler water plant problems may be similar to those arising in other types of water systems (such as cooling water systems), the extremely high steam-water temperatures and heat-flux densities generally encountered impart a much higher level of intensity. This in turn creates the need for more highly focused and effective solutions to boiler plant problems. 

Despite the relative simplicity of the kinetics of molecular chlorination, there has so far been only one measurement of the rate coefficient with a heterocyclic compound and the need for more work in this area is indicated. Marino265 found that chlorination of thiophene by chlorine in acetic acid at 25 °C gave the second-order rate coefficient of 10.0 1.5, so that thiophene is 1.7 x 109 times as reactive as benzene in this reaction and this large rate spread is clearly consistent with the neutral and hence relatively unreactive electrophile. 

Palladium(II) complexes provide convenient access into this class of catalysts. Some examples of complexes which have been found to be successful catalysts are shown in Scheme 11. They were able to get reasonable turnover numbers in the Heck reaction of aryl bromides and even aryl chlorides [22,190-195]. Mechanistic studies concentrated on the Heck reaction [195] or separated steps like the oxidative addition and reductive elimination [196-199]. Computational studies by DFT calculations indicated that the mechanism for NHC complexes is most likely the same as that for phosphine ligands [169], but also in this case there is a need for more data before a definitive answer can be given on the mechanism. 

Research should continue on traditional separation methods. For example, there is a continuing need for more selective extraction agents for liquid-liquid and ion-exchange extractions. High-temperature processes that use liquid metals or molten salts as extraction agents should have potential in nuclear fuel reprocessing and... 

In concluding this section we hope we have shown that there is a clear need for more elaborated studies to understand how lipophilic ions interact with biological membranes - an aspect that may look deceptively simple, but which is not yet completely understood. 

Currently available CRMs for Cr(lll)/(VI) species There exist a lyophilized water certified for Cr(III)/Cr(VI) and a binder-free glass fiber filter loaded with welding dust certified for Cr(VI) and total Cr (Vercoutere et al. 1998 Christensen et al. 1999) issued by the BCR. They consist of a set of specimens for single use. There is a need for more CRMs, such as a Cr(VI) in industrial effluents and in river water containing, e.g. humic substances. 

The need for more accurate and precise information about human use of MDMA and MDA was aptly stated by Dr. Gawin (this volume) and others. There is a general perception that these drugs are widely used, especially on college campuses, but there are relatively few hard data on the geographic distribution of use, on the pattem(s) and frequency of use, the doses used, and so on. For many reasons, such information is needed. 

Rats that have lost dopamine and/or serotonin terminals following treatment with amphetamine, methamphetamine, MDMA, MDA, / -chloroamphetamine, or fenfluramine show little in the way of overt ehanges in appearanee or behavior. Dr. Rieaurte (this volume) emphasized the need for more studies in primates, since MPTP-treated miee also show little in the way of observable functional changes, whereas MPTP-treated monkeys show marked neurologie deficits. It may be neeessary to do more detailed analysis of speeifie behaviors and other funetional outputs that are influeneed by dopamine and/or serotonin neurons, to detect functional deficits induced by some neurotoxic drugs. For instance, specific behaviors sueh as appetite-eontrolled behavior (Leibowitz and Shor-Posner 1986), murieidal behavior (Katz 1980), and sexual behavior (Tucker and File 1983) elieited by drugs... 

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