The thermochemistry of calcium strontium and barium in liquid ammonia at -33°C.

Thesis (Ph.D.)--Boston UniversityThe solutions of the alkali and alkaline earth metals in liquid ammonia are characterized by certain anomalous properties which are generally similar for these groups of metals. The similarity of the properties of these metal-ammonia solutions has been found to be due to the presence of a common negative species, the electron associated with the solvent in some undetermined manner (the "solvated" electron). In this dissertation the investigations of the ammonia solutions of the alkaline earth metals have been reviewed. Early studies have indicated that calcium, strontium, and barium metals combine with ammonia to form their respective hexammoniates, M(NH3)6. The heats of formation of these compounds, as determined from vapor pressure data, are: - 10.3 kcal.,- 9.9 kcal., and - 9.6 kcal., respectively. Magnesium metal, which is only sparingly soluble in liquid ammonia, also forms a hexammoniate. The following general remarks can be applied to all the alkaline earth metal ammoniates: the compounds a re identical in appearance with the solutions from which they are precipitated; the optical and electrical properties are the same for both the solid and the solution, therefore being independent of the physical state of the system and probably being determined by the same factors

Calorimetric determination of the heat of solution of calcium in liquid ammonia and the heat of reaction of calcium with the ammonium ion in liquid ammonia

Thesis (M.A.)--Boston University, 1949. This item was digitized by the Internet Archive

Rates and controls of footpath erosion in Giant's Castle Game Reserve, KwaZulu / Natal Drakensberg.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.The Drakensberg is an important ecological and recreational resource area within southern Africa, yet little knowledge exists concerning the factors controlling soil erosion in the region. The two most important anthropogenic modifiers of natural erosion processes in the areas beyond the: Drakensberg Park main camps and access roads are vegetation burning and the erosion associated with footpaths. This dissertation investigates the rates and controls of footpath erosion in Giant's Castle Game Reserve in the KwaZulu/Natal Drakensberg. Two measurement techniques are employed. Sediment yield and runoff were monitored from six runoff plots installed on different gradients on a high user-intensity footpath. Runoff is found to increase linearly with increasing footpath gradient. Sediment yield increases gradually with increasing footpath gradient to a threshold path gradient of 13.36°, after which sediment yield increases rapidly. Soil eroded from the runoff plots has a finer particle size distribution than the footpath tread surfaces within the plots. Rates of sediment generated from the runoff plots is dependant on the rainfall intensity index (I60), as opposed to rainfall kinetic energy or total rainfall related indices, while runoff is dependant on the El60 index. A 100m point-based survey of footpath attributes, totalling a distance of21km along four paths in the Reserve was undertaken. Where footpath gradients are low and user-intensity is high, path morphometry is dependant on orientation to the slope. Morphology of footpaths with both higher gradients and user-intensities show a dependence on path gradient. The degree of compaction of the footpath tread decreases away from the main camp and is positively related to user-intensity. Multiple path development is. associated with the path width to maximum depth ratios and a threshold ratio range of 4. 0 I to 4. 50 is established for the initiation of secondary path routes. A comparison of the survey data with a survey conducted in 1989 indicate erosion rates between 3.24 and 13. 0 tons/km/a over a four year period. Erosion rates for the runoff plots and for the surveys indicate that the values obtained for the two techniques of measurement utilised in the study approximate each other. Path erosion rates, while still presenting a prnblem, are not uncharacteristically high in Giant's Castle. Game Reserve in comparison to the scarce data available on rates of path erosion within and beyond southern Africa

Unavoidable induced subgraphs in large graphs with no homogeneous sets

A homogeneous set of an $n$-vertex graph is a set $X$ of vertices ($2\le |X|\le n-1$) such that every vertex not in $X$ is either complete or anticomplete to $X$. A graph is called prime if it has no homogeneous set. A chain of length $t$ is a sequence of $t+1$ vertices such that for every vertex in the sequence except the first one, its immediate predecessor is its unique neighbor or its unique non-neighbor among all of its predecessors. We prove that for all $n$, there exists $N$ such that every prime graph with at least $N$ vertices contains one of the following graphs or their complements as an induced subgraph: (1) the graph obtained from $K_{1,n}$ by subdividing every edge once, (2) the line graph of $K_{2,n}$, (3) the line graph of the graph in (1), (4) the half-graph of height $n$, (5) a prime graph induced by a chain of length $n$, (6) two particular graphs obtained from the half-graph of height $n$ by making one side a clique and adding one vertex.Comment: 13 pages, 3 figure

Memory for biopsychology material presented in comic book format.

This study investigated the influence of format of presentation on memory for undergraduate level Biopsychology material. Ninety participants read either seven comic book pages from Aleixo and Baillon (2008) explaining the rudiments of sleep, the same material presented in text only format or seven pages where the original images were replaced with random incongruous images. Participants were tested on the material using ten multiple-choice questions. Results showed significantly higher memory scores in the comic book condition compared to both the text only and the incongruous comic condition. Furthermore, the text only version showed significantly higher memory scores than the incongruous comic condition. It was concluded that while there were some limitations with the study, the findings provided preliminary evidence to support the general idea of using comic books to create instructional materials. Results also provided some support for dual coding theory (Paivio, 1969, 1972, 1975) as a theoretical basis for the use of comics in educational contexts. Keywords: Comics, Comic Books, Graphic Novels, Memory, Education, Dual-Coding Theory

The use of APS thermal barrier coatings in corrosive environments

Thermal barrier coatings (TBC) can be used to reduce the metal temperature of gas turbine blades enabling higher Cr alloys (lower strength) to be used when gas turbines are to be used in corrosive environments (where hot corrosion resistance is required). However, the TBC must also be resistant to the corrosive environment and remain attached to the blade. A 1000 h test to evaluate air plasma-sprayed (APS) TBC adhesion to a low-pressure plasma-sprayed CoNiCrAlY bond coat (with and without through thickness cracking) under hot corrosion conditions at 850 °C has been carried out. The APS TBC significantly reduced the hot corrosion rate of the CoNiCrAlY; however, delamination cracking occurred with a thinner thermally grown oxide than would be expected from isothermal and cyclic oxidation testing

The determination of the factor loadings of a given test from the known factor loadings of other tests

A technique is indicated by which approximations to the factor loadings of a new test may be obtained if factor loadings of a given group of tests and the correlations of the new test with the other tests are known. The technique is applicable to any orthogonal system and is especially adapted to cases in which Σ a ji a jk = 0 when i ≠ k . Application is also made to the simultaneous determination of the factor weights of a group of tests in which no additional common factor is present. The technique is useful in adding tests to a completed factorial solution and in using factorial solutions involving errors to give results which are approximately correct.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45697/1/11336_2005_Article_BF02288394.pd

The regulation of ion transport in the midgut of the lepidopteran larva Manduca sexta

Rapid growth during the larval stage of Lepidopteran insects is facilitated by vigorous transepithelial K+ transport from blood to gut lumen across the midgut. Active transport of K+ into the midgut lumen is required to energise amino acid uptake and is believed to contribute to the generation of the extremely high pH found in insect midgut. K+ transport is facilitated by a V-ATPase and K+/nH+ antiporter on the apical plasma membrane of the midgut goblet cell. A transmembrane voltage is generated by V-ATPase driven proton transport, consequently potassium is secreted by exchange for protons via the antiporter. This thesis confirms that the K+ transport system is abolished during periods of non feeding prior to pupation and during larval/larval moults. The moult from fourth to fifth instar was studied in detail. Transepithelial voltage, indicating net active K+ transport, was found to be approximately 100 mV during feeding periods but was found to fall to 0 mV during the moult. The transepithelial voltage was regenerated upon exit from the moult during ecdysis, just prior to resumption of feeding behaviour. The short circuit current was found to mirror these results. The pH of the midgut lumen was found to decline over the period of K+ transport inactivation. Thus during a moult, when the midgut is void of food, the K+ transport system is apparently not required and is consequently switched off. A transmembrane voltage is regenerated prior to the next gorge of food. The identity of the regulatory component of the K+ transport system was sought. The K+ pump is composed of two main components: the V-ATPase and the antiporter. ATPase activity assays on partially purified goblet cell apical membranes (GCAM) demonstrated that the V-ATPase was inactivated during the moult. ATP dependent proton transport into GCAM derived vesicles was also inactivated during the moult. ATP independent (antiporter) activity was not inhibited in vesicles derived from GCAM during the moult. The V-ATPase component thus appears to be the target of a control mechanism. In an effort to elucidate the mechanism of inactivation of the V-ATPase the V-ATPase structure was investigated using SDS gel electrophoresis. GCAM membranes, extracted from moulting or feeding larvae, were run on SDS gels and the V-ATPase subunit components were compared. Loss of V-ATPase activity paralleled the disappearance of specific V-ATPase subunits. The subunits missing were those considered to compose the peripheral V1 catalytic 'head' of the V-ATPase molecule. The integral membrane Vo subunits remained in the GCAM of moulting larvae. A mechanism, believed to be the first demonstration of which in vivo, of inactivation of a V-ATPase by dissociation of V1 from Vo is discussed. An attempt was made to reproduce the hormonal and intra cellular signals required for regulation of V-ATPase activity in vitro. cGMP was found to modestly activate transepithelial K+ transport. NADPH diaphorase staining suggested that nitric oxide synthase was present in the midgut tissue. However, sodium nitroprusside (a spontaneous generator of nitric oxide) did not stimulate K+ transport. This thesis has identified that K+ transport is regulated and that regulation occurs at the level of the V-ATPase. The V-ATPase is inactivated by the loss of the V1 domain of the molecule. Transport may be manipulated in vitro by various secondary messengers

Comment on "Lightning as a geomorphic agent on mountain summits : evidence from southern Africa" by Knight and Grab (2014)

Insights into the possible effect of lightning strikes on rock breakdown are presented by Knight and Grab (2014) froma summit area in the Lesotho highlands. Based on their findings, the authors challenge the association of angular debris with frost shattering and use this as a platform for directing critique against palaeo-geomorphic studies.While the lightning strike data are not questioned directly here, the palaeo-environmental contextwithin which the paper is set, the portrayal of former findings and the assumptions regarding weathering mechanisms in Lesotho are commented on. Frost shattering is the centre of Knight and Grab's weathering critique but, contrary to that stated in their text, none of the cited authors invoke this process in Lesotho. Other weathering processes that are speculated upon are not specific to cold climates either and thus cannot be used in support of their argument. In terms of debris and block distribution, lightning will not account for the preferential location of relict blocks and debris below the summits on south-facing slopes, or for the extensive valley floor accumulations that are documented in Lesotho. Knight and Grab also falsely portray former studies by implying that palaeo-environmental inferences in the area are drawn fromblock origin or morphology alonewhen the climatic signatures were derived from integrated assessments. In a palaeo-context, the relative contribution of lightning to debris production under dryer and colder conditions, when convective thunderstorm activity in the highlands was likely reduced, is also questioned. The weathering context, as well as the critique that Knight and Grab direct at other studies on relict landforms, is thus shown as inappropriate.http://www.elsevier.com/locate/geomorphhb201