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The question of what, if anything, limits the length of food chains has been problematic ever since Elton originally asked it decades ago. Here, we reexamine the major evidence for one of the chief hypotheses: dynamical constraints. Reportedly, food chain stability decreases as chain length increases. However, the separate roles of self‐damping (where a species shows density dependence independent of the densities of other species in the food chain model) and chain length have not been adequately determined. We examined food webs of varying chain length while controlling for self‐damping. In contrast to the prevailing hypothesis, we find a weak but significant increase in stability in longer chains when we hold constant the number of species and the number of self‐damping terms. Thus, the conclusion that longer food chains are more dynamically fragile, thereby setting an upper limit to food chain length, has at best very limited theoretical support. Our results indicate that community stability should tend to lengthen, not shorten, food chains. Mechanisms limiting the length of food chains remain to be convincingly demonstrated

The study was undertaken with a view to explore the use of carrot pomace powder as well as beetroot pomace powder with whole wheat flour in the preparation of high fiber biscuits, to study its effect on the physico-chemical and sensory characteristics of biscuits. The Carrot Pomace Powder (CPP) and Beetroot Pomace Powder (BPP) were prepared through the process of convective dehydration and vacuum drying. All the data obtained were analyzed statistically to determine the level of significance of variation in observations caused by the changes in the biscuits formulations. The carrot pomace and beetroot pomace fortified biscuits contained greater amount of ash, crude fiber and moisture content than control biscuits but lower carbohydrate, protein, calorific value and pH. After fortification of fiber, product was found to be more acceptable in terms of physico-chemical and sensory characteristics.

Dehydrohalogenatlon of N-(2-aroylmethyl)9-plcollnlum and -4-picollnlum bromlde, prepared by the quanternlzation of corresponding bromlde salt with triethylamine, afforded a hlghly reactive cyclolmmonlum yllde. Its 1,3-dipolar cycloaddition reactions with varlous dipolarophlles have been lnvestlgated. These reactions ultlmately result in the formation of novel heterocycllc compounds. The structural assignment of the products were made on the basis of elemental analyses and spectroscopic data. I ntroductlonThe chemistry of cycloimmonium ylide has engaged the attention of chemists because of their importance as useful intermediates in the synthesis of novel heterocyclics. Despite the wide applicability of cycloimmonium ylide ( 7 -7 7 ) in synthetic studies, no information is available concerning the 1,3-dipolar cycloaddition reactions of methyl-substituted pyridinium ylide.I n the course of our investigations on the preparative utility of cycloimmonium ylide, we wish to report the syntheses and physical and spectral properties of indolizines having biological activities. Results and DiscussionTreatment of w-bromo ketones with picolines in anhydrous benzene at reflux temperature lead to the quarternization of picolines giving N-(2-aroylmethyl)picolinium bromides (Scheme I), in excellent yield. The bromide salts when treated with triethylamine in dry benzene immediately generated a dark red coloration due to the formation of corresponding ylide, which on subsequent reaction with various dipolarophiles (acetylenic esters) gave five-membered heterocyclic derivatives (5a-d, 7a-d).( 4 a 4 , 6a-d 1The reaction of picolinium ylides with the acetylenic triple bond of acetylenic ester such as dimethyl acetylenedicarboxylate and diethyl acetylenedicarboxylate appears to proceed by the nucleophilic attack of the carbanion similar to the first step of Michael type of addition. The stabilization of this zwitterion presumably takes place by internal nucleophilic attack of the carbanion on the a-position of the picoline ring