A Study Of The Formation Of Cyclic Allenes From 2,3-Dibromocycloalkenes

This investigation was undertaken in an attempt to form strained cyclic allenes and to study their chemistry. The method chosen for the attempted formation of strained cyclic allenes was the determination of the corresponding 2,3-dibromocycloalkene. 2,3-Dibromocyclononene was synthesized during the course of this investigation so that its debromination to the 1,2-cyclononadiene, which is the smallest stable, 1,2-cycloalkadiene, could be studies as model for the debromination of smaller 2,3-dibromocycloalkenes was initiated. The formation of 1,2-cyclohexadiene was attempted by the debromination of the 2,3-dibromocyclohexene. Evidence for the presence of this unstable intermediate was sought via the use of trapping agents

Studies in the higher coal tar bases

The work to be described in this thesis takes the form of an investigation of the nitrogenous bases which can be extracted by sulphuric acid from the Naphthalene Oil and the Benzol Absorbing Oil fractions of coal tar, after the tar oils have been freed from phenols by extraction with caustic soda. The chief objects of the investigation were :- (1) To obtain a weight / temperature of distillation balance for both fractions of bases, thus showing the relative abundances of the more common fractions, and possibly indicating where any previously unidentified bases were liable to occur. (2) To make a closer study of the fractions boiling between 180° and 235 °, and over 265 °C /760mm.Hg, as these two fractions have not been exhaustively studied in the past, and, where possible, to isolate and identify pure bases. The nitrogenous bases which can be extracted by sulphuric acid from coal tar or coal tar oils consist mainly of pyridine, quinoline, isoquinoline, and their homologues, together with small quantities of pyrrole, aniline, toluidines, xylidines, acridine and naphthylamines. According to present industrial practice the only bases which are extensively utilised are pyridine and its lower homologues, the commercially available products being :- Pure Pyridine - This is obtained by a close fractionation of the lower tar bases and is used as an intermediate in the production of "sulpha" drugs (sulphapyridine), dyestuffs, vulcanisation accelerators and waterproofing compounds, and as a solvent and catalyst. "90 -140° or 90 -160° Bases" - These are obtained by crude fractionation of the lower tar bases and are used as denaturants, solvents, level- lers in leather dyeing, insecticides, and also in the production of pattern effects on cotton and rayon, and in lubricating oil refining. "90 -180° Bases" - These are obtained by crude fractionation of tar bases and are used as solvents, in anthracene purification, and as restrainers in metal pickling baths. In addition to these main industrial products the following are produced in smaller quantities :- Picolines - These have been produced in small quantities from time to time, but recently, owing to the great demand for nicotinic acid as an accessory dietary factor, an interest has been aroused in ß- pieoline, and considerable quantities have been produced for oxidation to nicotinic acid. I,utidines & Collidines - These have only been produced in semi -commercial and experimental quantities. It is difficult to ascertain the sources of the above products owing to the differences in works practice throughout the country, especially with respect to the temperature ranges of the oil cuts taken, but it would appear that they are produced for the most part from the lower boiling tar oils, and according to present works practice the bases are seldom removed from the Naphthalene Oil and Benzol Absorbing Oil fractions. The total United Kingdom production of "pyridine bases" amounted to 166,000 gallons in 1948 and to 167,000 gallons in 1949 (Nin. of Fuel & Power), and there are indications that more could be used if it were available. If this is the case, it is possible that the Naphthalene Oil fraction rn1 ht provide a useful auxiliary source. Very little work has been carried out on the utilisation of the tar bases boiling above 180 °C, such as are obtained from the Benzol Absorbing Oil fraction, although quinoline and isoquinoline have been isolated in semi -commercial and experimental quantities, and during the recent war the xylidines were separated for use as aviation fuel additives. It was considered, therefore, that some quantitative estimate of the constitution of the Benzol Absorbing oil base fraction would be of considerable value

Population Demography and Herbivory of Trillium Grandiflorum

Numerous pedicellate and sessile Trillium species are endemic to eastern North America, where white-tailed deer (Odocoileus virginianus) populations have been growing in recent decades. Deer feed on Trillium plants, and because they often consume all leaves and flowers, the photosynthetic capacity of browsed plants is greatly diminished. To determine if deer can influence Trillium population dynamics, we review two recent studies that applied matrix population models to understand how deer browsing affects Trillium grandijlorum. Research conducted in the Great Lakes region indicated Trillium populations in which 6-12% plants were browsed declined 3.6% per year. Simulations show that with additional browsing, the rate of population decline accelerates. Similar research conducted in the Appalachian plateau region by a different researcher yielded nearly identical results. We apply insights from these matrix population models to two additional conservation problems in Trillium: unsustainable collecting of wild plants and forest fragmentation. Because other Trillium in the eastern United States are similar morphologically and ecologically, our results from Trillium grandiflorum might be generalized to apply to other members of the genus

The Use Of Deep Learning Strategies In Online Business Courses To Impact Student Retention

Interest, application and understanding—these are key elements in successful online classroom experiences and all part of what is commonly referred to as deep learning.  Deep learning occurs when students are able to connect with course topics, find value in them and see how to apply them to real-world situations.  Asynchronous discussion forums in business courses offer excellent opportunities for instructors to promote deep learning and, thereby, positively impact retention rates.  Instructional strategies that encourage deeper thought and further consideration of course topics not only lead to robust discussions but also to heightened student interest and motivation levels.  This paper presents a review of deep learning strategies, explains how they can be successfully incorporated into asynchronous course discussions and highlights several critical connections between deep learning and increased student retention

Strain and field modulation in bilayer graphene band structure

Using an external electric field, one can modulate the bandgap of Bernal stacked bilayer graphene by breaking A-~B symmetry. We analyze strain effects on the bilayer graphene using the extended Huckel theory and find that reduced interlayer distance results in higher bandgap modulation, as expected. Furthermore, above about 2.5 angstrom interlayer distance, the bandgap is direct, follows a convex relation to electric field and saturates to a value determined by the interlayer distance. However, below about 2.5 angstrom, the bandgap is indirect, the trend becomes concave and a threshold electric field is observed, which also depends on the stacking distance.Comment: 3 pages, 5 figures - v1 and v2 are the same, uploaded twice - v3, some typos fixed and a reference adde

Phylogeny, Adaptive Radiation, and Historical Biogeography of Bromeliaceae Inferred from ndhF Sequence Data

Cladistic analysis of ndhF sequences identifies eight major bromeliad clades arranged in ladderlike fashion. The traditional subfamilies Tillandsioideae and Bromelioideae are monophyletic, but Pitcairnioideae are paraphyletic, requiring the description of four new subfamilies, recircumscription of Pitcairnioideae and Navioideae, the sinking of Ayensua, and description of the new genus Sequencia. Brocchinioideae are basalmost, followed by Lindmanioideae, both restricted to the Guayana Shield. Next is an unresolved trichotomy involving Hechtioideae from Central America, Tillandsioideae, and the remaining bromeliads in subfamilies Navioideae, Pitcairnioideae, Puyoideae, and Bromelioideae. Bromeliads arose as C3 terrestrial plants on moist infertile sites in the Guayana Shield roughly 70 Mya, spread centripetally in the New World, and reached tropical West Africa (Pitcairnia feliciana) via long-distance dispersal about 10 Mya. Modern lineages began to diverge from each other 19 Mya and invaded drier areas in Central and South America beginning 15 Mya, coincident with a major adaptive radiation involving the repeated evolution of epiphytism, CAM photosynthesis, impounding leaves, several features of leaf/trichome anatomy, and accelerated diversification at the generic level. This ‘‘bromeliad revolution’’ occurred after the uplift of the northern Andes and shift of the Amazon to its present course. Epiphytism may have accelerated speciation by increasing ability to colonize along the length of the Andes, while favoring the occupation of a cloud-forest landscape frequently dissected by drier valleys. Avian pollination (mainly by hummingbirds) evolved at least twice ca. 13 Mya; entomophily was ancestral. Hechtia, Abromeitiella–Deuterocohnia–Dyckia–Encholirium, and Puya exhibit a remarkable pattern of concerted convergence in six anatomical and physiological leaf traits adapted to drought