Volatility speculation

Essential oils are known to have detrimental effects on plants. The inhibitory components have not been identified, but both alde-hydic (benzol-, citrol-, cinnamal-aldehyde) and phenolic (thymol, carvacol, apiol, safrol) constituents are suspected. Muller et al. (104) demonstrated that volatile toxic materials localized in the leaves of Salvia leucophylla, Salvia apiana, and Arthemisia californica inhibited the root growth of cucumber and oat seedlings. They speculated that in the field, toxic substances from the leaves of these plants might be deposited in dew droplets on adjacent annual plants. In a subsequent paper, Muller and Muller (105) reported that the leaves of S. leucophylla contained several volatile terpenes, and growth inhibition was attributed to camphor and cineole. 

The residual fraction of Zn, Se, Sb and Hg was changed with the rise of temperature. The residual fraction of Zn decreased over 1273 K drastically. And the residual fraction of Se, Sb and Hg was decreased in temperature range of 373-773 K. These results were mostly coincided with the speculated volatility from thermodynamic property of each element mentioned above. 

Empirical evidence supporting the role of soil micro-layer losses in zero-time issues is given by the often-seen rise in post zero-time residue recoveries. The improved recoveries likely result from the micro-layer residue redistribution that reduces losses of the highly concentrated surface residues. There has been some speculation that zerotime core recoveries may be due to volatilization losses not measured by standard laboratory studies. If this were the case, however, increases in residue concentrations would not occur over time since volatilized residues would be lost to the atmosphere. ... 

The prophecy on semiochemical systematics in the headline quotation at the start of this chapter remains just that — an intriguing speculation. Some single-component chemosignals do turn up as apparently the main active compound in a complex secretion. In male gerbils (Meriones) one volatile, phenylacetic acid, appears to represent the dominant male state (Thiesen, 1974). Individuality must be added by further components — dietary or variable sebum constituents in this case. Indeed, amongst mammals and some reptiles, complex mixtures seem to be the norm very few taxonomically relevant examples have emerged. 

Abstract This chapter reviews chemical structures of biologically active, volatile compounds in beetles. Techniques used for structure elucidation are briefly discussed as well as facts and speculations on the biosynthesis of target compounds. Syntheses of selected substances are cursorily presented. The order of sections follows taxonomic classifications. Depending on the biological significance of relevant compounds in certain taxa, the corresponding sections are again subdivided into attractive compounds (mostly intraspecifically active pheromones) and defensive compounds (mostly interspecifically active allomones). 

The neotropical staphylenid Leistrotrophus versicolor use volatile compounds secreted from their abdominal tips to attract their prey, drosophilid and phorid flies [ 116]. The structures of the active compounds are yet unknown, however, it has been speculated that actinidine or other iridoids, typically found in the defensive gland which are located at the abdominal tips of these beetles, may be key components [117]. 

Public investors purchase stock in IPOs or follow-on rounds after the technical risk has declined and the stock is liquid. Some of these investors expect to make their return when important commercial milestones are achieved, i.e., positive Phase 3 results, FDA approval, or financial breakeven, usually within a few years. Other investors are "momentum players" who hope to buy the stock on an upswing and get out before investor enthusiasm wanes, often within several months. Still other speculators enjoy playing the high volatility of biotech stocks, hoping to make returns within several days. 

In the case of the electron poor alkenes, results were more varied. Under all conditions examined, reactions with methyl vinyl ketone, acrylonitrile, methacrylonitrile and 4-vinyl pyridine afforded products with IR spectra equivalent to those obtained without the addition of the alkene (side reaction). In the cases of vinyl bromide and chloromethyl styrene, unreacted PCTFE was recovered unchanged. It is speculated that electron transfer to the alkene proceeded in each case. While the product of vinyl bromide reduction was not observed, perhaps because of volatility, one could isolate poly(chloromethylstyrene) in the latter case. 

Males of the collembolan, Sinella curviseta, deposit spermatophores in response to the emission of a putative, volatile sex pheromone produced by females (Waldorf, 1974). The emission of pheromone has been speculated to be related to the molting process (Waldorf, 1974), which suggests that sex pheromone in these species also may well be produced by epidermal cells associated with the integument. 

A pair of globular structures that protrude from the intersegmental membrane between tergites 5 and 6 are displayed during the evening hours by female mantid, Tarachodes afzelii (Mantodea). This behavior has been speculated to result in emission of a volatile sex pheromone (Edmunds, 1975). There has been no further work on this or other species of mantids to determine if indeed sex pheromones are involved in their sexual behavior, and on the chemical nature of the secretions and the ultrastructure of the source. 

The Siphonaptera is another group where a volatile sex pheromone is yet to be demonstrated, although a contact sex pheromone has been demonstrated in preliminary experiments (Ralph Charlton, personal communication). The source and nature of this contact pheromone is yet to be deciphered. Fleas have been speculated to use a certain wavelength of light, C02, and visual and thermal stimuli for host localization, as traps that present these kinds of stimuli seem to be effective in trapping fleas (Benton and Lee, 1965 Osbrink and Rust, 1985 Dryden and Broce, 1993). 

Little is known of the cellular processes that deliver volatile pheromones from secretory cells to the cuticular surface, even in the intensively researched Lepidoptera. Based on results from ultrastructural studies of the moth Heliothis virescens, Raina el al. (2000) recently speculated that secretory cells of the pheromone gland somehow deliver pheromone or its precursors to hollow cuticular hairs. During calling behavior the female exposes the gland and also the cuticular hairs that exude pheromone droplets. Raina et al. (2000) further posit that as the female retracts the ovipositor more pheromone is squeezed onto the exposed surface, thus recharging the cuticular hairs. 

Aldehyde Formation. Several investigators observed a marked dominance of hexanal in the volatile products of low-temperature oxidation. At the higher temperatures, however, 2,4-decadienal was the major aldehyde formed (19,20,21). Both aldehydes are typical scission products of linoleate hydroperoxides. Swoboda and Lea (20) explained this difference on the basis of a selective further oxidation of the dienal at the higher temperature, while Kimoto and Gaddis (19) speculated that the carbon-carbon bond between the carbonyl group and the double bond (Type B) is the most vulnerable to cleavage under moderate conditions of autoxidation, while scission at the carbon-carbon bond away from the olefinic linkage (Type A) is favored under stress such as heat or alkali. 

Another concept that warrants mention is desolvation When silver metal in bulk is heated, it tends to sublime as neutral species. When both neutral and cationic silver species volatilize from these silica gel matrices they are exclusively monatomic. This indicates that silver atoms in the zero oxidation state are not solvated by each other or by a component in the matrix. This concept is admittedly speculative but does offer a concept as to how this ion emitter matrix may operate. 

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