Negative results

The PY approximation for die binding leads to negative results for X the HNC approximation for this is satisfactory. Figure A2.3.18 shows the excess energy as a fiinction of the weak electrolyte concentration for the RPM and SEM for a 2-2 electrolyte. 

Owens Lake. Owens Lake is a relatively small alkaH deposit in Southern California where small amounts of cmde trona are recovered and sold (30,31). Several feasibiHty studies with regard to expanding production at this site have been conducted over the years with negative results. 

Precursor loading using choline (qv) or lecithin (qv) (13) failed to have a significant effect on AD symptoms (98,105—107). These negative results may, in part, be related to the observation that lecithin does not alter central cholinergic activity in AD (108). 

Although in vitro mutagenicity tests suggest that some nitrofurans in general provoke a positive response, use of in vivo mammalian systems has produced equivocal or negative results. 

P-D-Arabinofuranosylcytosine [147-94-4] (ara-C, 16), C H N O, reportedly has had significant therapeutic effects in patients with localized herpes zoster, herpes eye infections, and herpes encephaUtis (33), although several negative results have also been reported (34) (Fig. 2). Ara-C, also known as cytarabine, is quite toxic and is only recommended for very severe viral infections. It is rapidly deaminated in humans to the relatively inactive ara-U Ara-C is converted in the cell to the 5 -monophosphate by deoxycytidine kinase, followed by formation of the corresponding di- and triphosphate. The triphosphate has been shown to inhibit DNA polymerase. 

The pumped-discharge case is generally more difficult to solve because of the uncertainty in deahng with negative numerical results. As a final answer, a negative value could indicate that the pump has completely emptied the tank however, as an intermediate value, it could mean that it is not a true solution. A simple check is to try a different initial estimate and see if the intermediate negative results disappear. 

The ability to identify and quantify cyanobacterial toxins in animal and human clinical material following (suspected) intoxications or illnesses associated with contact with toxic cyanobacteria is an increasing requirement. The recoveries of anatoxin-a from animal stomach material and of microcystins from sheep rumen contents are relatively straightforward. However, the recovery of microcystin from liver and tissue samples cannot be expected to be complete without the application of proteolytic digestion and extraction procedures. This is likely because microcystins bind covalently to a cysteine residue in protein phosphatase. Unless an effective procedure is applied for the extraction of covalently bound microcystins (and nodiilarins), then a negative result in analysis cannot be taken to indicate the absence of toxins in clinical specimens. Furthermore, any positive result may be an underestimate of the true amount of microcystin in the material and would only represent free toxin, not bound to the protein phosphatases. Optimized procedures for the extraction of bound microcystins and nodiilarins from organ and tissue samples are needed. 

Sensitive to toxins, in this case means that the assay presents no false negative results. Primary hepatocytes can elucidate hepatotoxins, and mouse neuroblastoma cells can elucidate sodium channel-blocking neurotoxins therefore these assays can be used to screen for the appropriate toxins. 

This solution is extracted several times with 5% acetic acid, until the silico-tungstate test (an identification test for alkaloids) yields a negative result, and the acetic solutions are washed with 10 ml ether. 

To prove that a particular design of a perpetual motion machine will not work can be vei y time consuming, and the predictable negative result has never been worth the effort. Therefore, the U.S. Patent Office has a policy to not examine applications covering perpetual motion machines unless the applicant furnishes a working model. 

The nonexistence of perpetual motion machines, despite centuries of effort to design them, has been used to support the law of consciwation of energy. This law is based, however, not on this negative result, but on all the experiments performed to date in which energy is carefully accounted for. It has never been observed to fail. This law is, therefore, a good basis from which to analyze perpetual motion machines. It clearly states that the goal of getting... 

The first result, for At = 0.5, shows a negative result for a(t ax) due to the very large value for At. For smaller values of At, the calculated values for a tmax) are physically realistic and the errors decrease by roughly a factor of 4 as the time step decreases by a factor of 4. Thus, the error is proportional to At. Euler s method is said to converge order At, denoted 0(At). 

Methyl parathion has been tested in numerous genotoxicity assays using prokaryotic and eukaryotic systems with both positive and negative results. Results of these studies are summarized in Tables 3-5 and 3-6. 

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