14 resultados para Layered and staggered structure
em Brock University, Canada
Resumo:
The crystal structure of Cu(PM)2(N03hoH20 (where PM is pyridoxamine, CSHI2N202) has been determined from three dimensional x-ray diffraction data. The crystals are triclinic, space group pI, a = 14.248 (2), b = 8.568 (1), c = 9.319 (1) 1, a = 94.08 (1), e = 89.73 (1), y~~ 99.18 (1)°, z = 2, jl(MoK) = 10.90 em-I, Po = 1.61 g/cm3 and Pc = 1.61 g/em3• The structure a was solved by Patterson techniques from data collected on a Picker 4-circle diffractometer to 26max = 45°. All atoms, including hydrogens, have been located. Anisotropic thermal parameters have been refined for all nonhydrogen atoms. For the 2390 independent reflections with F ? 3cr(F) , R = 0.0408. The results presented here provide the first detailed structural information of a metal complex with PM itself. The copper atoms are located on centres of symmetry and each is chela ted by two PM zwitterions through the amino groups and phenolate oxygen atoms. The zwitterionic form found in this structure involves the loss of a proton from the phenolate group and protonation of the pyridine ring nitrogen atoms. The two independent Cu(PM)2 moieties are symmetrically bridged by a single oxygen atom from one of the nitrate groups. The second nitrate group is not coordinated to the copper atoms but is central to an extensive hydrogen bonding network involving the water molecule and uncoordinated functional groups of PM.
Resumo:
The x-ray crystal structure of thiamine hydroiodide,C1ZH18N40S12' has been determined. The unit cell parameters are a = 13.84 ± 0.03, o b = 7.44 ± 0.01, c = 20.24 ± 0.02 A, 8 = 120.52 ± 0.07°, space group P2/c, z = 4. A total of 1445 reflections having ,2 > 2o(F2), 26 < 40° were collected on a Picker four-circle diffractometer with MoKa radiation by the 26 scan technique. The structure was solved by the heavy atom method. The iodine and sulphur atoms were refined anisotropically; only the positional parameters were refined for the hydrogen atoms. Successive least squares cycles yielded an unweighted R factor of 0.054. The site of protonation of the pyrimidine ring is the nitrogen opposite the amino group. The overall structure conforms very closely to the structures of other related thiamine compounds. The bonding surrounding the iodine atoms is distorted tetrahedral. The iodine atoms make several contacts with surrounding atoms most of them at or near the van der Waal's distances A thiaminium tetrachlorocobaltate salt was produced whose molecular and crystal structure was j~dged to be isomorphous to thiaminium tetrachlorocadmate.
Resumo:
Hg(18-Crown-6)C12 and Cd(18-Crown-6)C12 are isostructura1, space group Cl~ Z = 2. For the mercury compound, a = 10.444(2) A° , b = 11. 468(1) A° , c = 7.754(1) A° , a = 90.06(1)°, B = 82.20(1)°, Y = 90.07(1)°, Dobs = 1.87, Dca1c = 1.93, V = 920.05 13, R = 4.66%. For the cadmium compound, 000 a = 10.374(1) A, b = 11.419(2) A, c = 7.729(1) A, a = 89.95(1)°, B = 81.86(2)°, Y = 89.99(1)°, Dobs = 1.61, Dcalc = 1.64, V = 906.4613, R = 3.95%. The mercury and cadmium ions exhibit hexagonal bipyramidal coordination, with the metal ion located on a centre of symmetry in the plane of the oxygen atoms. The main differences between the two structures are an increase in the metal-oxygen distance and a reduction in the metalchloride distance when the central ion changes from Cd2+ to Hg2+. These differences may be explained in terms of the differences in hardness or softness of the metal ions and the donor atoms.
Resumo:
Changes in the configuration of a tree stern result insignificant differences in its total volume and in the proportion of that volume that is merchantable timber. Tree allometry, as represented by stem-fo~, is the result of the vertical force of gravity and the horizontal force of wind. The effect of wind force is demonstrated in the relationship between stem-form, standclosure and site-conditions. An increase in wind force on the individual tree due to a decrease in stand density should produce a more tapered tree. The density of the stand is determined by the conditions that the trees are growing under. The ability of the tree to respond to increased wind force may also be a function of these conditions . This stem-form/stand-closure/site-conditions relationship was examined using a pre-existing database from westcentral Alberta. This database consisted of environmental, vegetation, soils and timber data covering a wide range of sites. There were 653 sample trees with 82 variables that formed the basis of the analysis. There were eight tree species consisting of Pinus contorta, Picea mariana, Picea engelmannii x glauca, Abies lasiocarpa, Larix laricina, Populus tremuloides, Betula papyrifera and Populus balsamifera plus a comprehensive all-species data set. As the actual conformation of the stern is very individual, stem-fo~was represented by the diameter at breast height to total height r~tio. The four stand-closure variables, crown closure, total basal area, total volume and total number of stems were reduced to total basal area and total number of stems utilizing a bivariate correlation matrix by species. Site-conditions were subdivided into macro, meso and micro variables and reduced in number 3 using cross-tabulations, bivariate correlation and principal components analysis as screening tools. The stem-fo~/stand-closure relationship was examined using bivariate correlation coefficients for stem-fo~ with total number of stems and stem-fo~ with total basal area. The stem-fo~/site-conditions and the stand-closure/site- conditions relationships were examined using multiple correlation coefficients. The stem-form/stand-closure/site-conditions relationship was examined using multiple correlation coefficients in separate analyses for both total number of stems and total basal area. An increase in stand-closure produced a decrease in stem-form for both total number of stems and total basal area for most species. There was a significant relationship between stem-form and site-conditions and between stand-closure and site-conditions for both total number of stems and total basal area for most species. There was a significant relationship between the stemform and site-conditions, including the stand-closure, for most species; total number of stems was involved independently of the site-conditions in the prediction of stem-form and total basal area was not. Larix laricina and Betula papyrifera were the exceptions to the trends observed with most species. The influence of both stand-closure (total number of stems in particular) and site-conditions (elevation in particular) suggest that forest management practices should include these- ecological parameters in determining appropriate restocking levels.
Resumo:
Three dimensional model design is a well-known and studied field, with numerous real-world applications. However, the manual construction of these models can often be time-consuming to the average user, despite the advantages o ffered through computational advances. This thesis presents an approach to the design of 3D structures using evolutionary computation and L-systems, which involves the automated production of such designs using a strict set of fitness functions. These functions focus on the geometric properties of the models produced, as well as their quantifiable aesthetic value - a topic which has not been widely investigated with respect to 3D models. New extensions to existing aesthetic measures are discussed and implemented in the presented system in order to produce designs which are visually pleasing. The system itself facilitates the construction of models requiring minimal user initialization and no user-based feedback throughout the evolutionary cycle. The genetic programming evolved models are shown to satisfy multiple criteria, conveying a relationship between their assigned aesthetic value and their perceived aesthetic value. Exploration into the applicability and e ffectiveness of a multi-objective approach to the problem is also presented, with a focus on both performance and visual results. Although subjective, these results o er insight into future applications and study in the fi eld of computational aesthetics and automated structure design.
Resumo:
This thesis examines Death of a Ghost (1934), Flowers for the Judge (1935), Dancers in Mourning (1937), and The Fashion in Shrouds (1938), a group of detective novels by Margery Allingham that are differentiated from her other work by their generic hybridity. The thesis argues that the hybrid nature of this group of Campion novels enabled a highly skilled and insightful writer such as Allingham to negotiate the contradictory notions about the place of women that characterized the 1930s, and that in dOing so, she revealed the potential of one of the most popular and accessible genres, the detective novel of manners, to engage its readers in a serious cultural dialogue. The thesis also suggests that there is a connection between Allingham's exploration of modernity and femininity within these four novels and her personal circumstances. This argument is predicated upon the assumption that during the interwar period in England several social and cultural attitudes converged to challenge long-held beliefs about gender roles and class structure; that the real impact of this convergence was felt during the 1930s by the generation that had come of age in the previous decade-Margery Allingham's generation; and that that generation's ambivalence and confusion were reflected in the popular fiction of the decade. These attitudes were those of twentieth-century modernity--contradiction, discontinuity, fragmentation, contingency-and in the context of this study they are incorporated in a literary hybrid. Allingham uses this combination of the classical detective story and the novel of manners to examine the notion of femininity by juxtaposing the narrative of a longstanding patriarchal and hierarchical culture, embodied in the image of the Angel in the House, with that of the relatively recent rights and freedoms represented by the New Woman of the late nineteenth-century. Pierre Bourdieu's theory of social difference forms the theoretical foundation of the thesis's argument that through these conflicting narratives, as well as through the lives of her female characters, Allingham questioned the Hsocial myth" of the time, a prevailing view that, since the First World War, attitudes toward the appropriate role and sphere of women had changed.
Resumo:
In this thesis, I critically examine the discourses that inform how we conceptualise HIV/AIDS in Sub-Saharan Africa as they are produced in a sample of Canadian news articles, two nonfiction texts - Stephanie Nolen's 28 Stories of AIDS in Africa and Jonathan Morgan and the Bambanani Women's Group's Long Life ... Positive HIV Stories - as well as two literary texts - John Le Carre's popular fiction novel The Constant Gardener and an anthology of stories and poems from Southern Africa titled Nobody Ever Said AIDS, compiled and edited by Nobantu Rasebotsa, Meg Samuelson and Kylie Thomas. Paying particular attention to the role of metaphor in discursive formation, I have found that military metaphors, usually used in conjunction with biomedical discourses, continue to dominate what is said about HIV/AIDS. However, the use of military metaphors to conceptualise HIV/AIDS contributes to stigma and limits the effectiveness of responses to the pandemic. I argue that accessing alternative metaphors and discourses, such as biopsychosocial discourse, can lead to a more layered - and more beneficial - conceptualisation of HIV/AIDS, encouraging a more active response to the pandemic.
Resumo:
Using the Physical Vapor Transport method, single crystals of Cd2Re207 have been grown, and crystals of dimensions up to 8x6x2 mm have been achieved. X-ray diffraction from a single crystal of Cd2Re207 has showed the crystal growth in the (111) plane. Powder X-ray diffraction measurements were performed on ^^O and ^^O samples, however no difference was observed. Assigning the space group Fd3m to Cd2Re207 at room temperature and using structure factor analysis, the powder X-ray diffraction pattern of the sample was explained through systematic reflection absences. The temperatiure dependence of the resistivity measurement of ^^O has revealed two structural phase transitions at 120 and 200 K, and the superconducting transition at 1.0 K. Using Factor Group Analysis on three different structiures of Cd2Re207, the number of IR and Raman active phonon modes close to the Brillouin zone centre have been determined and the results have been compared to the temperature-dependence of the Raman shifts of ^^O and ^*0 samples. After scaling (via removing Bose-Einstein and Rayleigh scattering factors from the scattered light) all spectra, each spectrum was fitted with a number of Lorentzian peaks. The temperature-dependence of the FWHM and Raman shift of mode Eg, shows the effects of the two structurjil phase transitions above Tc. The absolute reflectance of Cd2Re207 - '^O single crystals in the far-infrared spectral region (7-700 cm~^) has been measured in the superconducting state (0.5 K), right above the superconducting state (1.5 K), and in the normal state (4.2 K). Thermal reflectance of the sample at 0.5 K and 1.5 K indicates a strong absorption feature close to 10 cm~^ in the superconducting state with a reference temperature of 4.2 K. By means of Kramers-Kronig analysis, the absolute reflectance was used to calculate the optical conductivity and dielectric function. The real part of optical conductivity shows five distinct active phonon modes at 44, 200, 300, 375, and 575 cm~' at all temperatures including a Drude-like behavior at low frequencies. The imaginary part of the calculated dielectric function indicates a mode softening of the mode 44 cm~' below Tc.
Resumo:
A mycoparasite, Piptocephalis virginiana ^ shows a resemblance to fungal parasites of higher plants in the fine structure of hyphae and haustoria. The morphology and fine structure of host and parasitic fungi have been described. The mode of penetration of the host cell, Choanephora cucurbitarum , probably involves mechanical forces. Although the presence of cell wall degrading enzyme was not detected by conventional techniques, its role in penetration can't be ruled out. A collar around the haustorial neck is formed as an extension of the host cell wall. No papilla was detected although appressorixim was seen during penetration. The young haustorium is enclosed in highly invaginating plasmalemma of the host cell and n\imerous cisternae of endoplasmic reticulum. Appearance of an electron—dense sheath around the mature haustorium seems to coincide with the disappearance of cisternae of endoplasmic reticulum from the host cystoplasm in the vicinity of the haustorium. The role of host cytoplasm particularly of endoplasmic reticulum in the development of the sheath is discussed. Extensive accumulation of spherosomes-like bodies, containing lipids, is found in haustorium, parasite and host hypha. Electron microscope revealed the parasiticculture spore has more lipid content than the axenic culture spore of P. virginiana . The biochemical and cytochemical tests also support these results. The mature spore of C. cucurbitarum possesses a thick three-layered cell wall, different from the hyphal wall. Its germination is accompanied by the formation of an elastic thin inner layer which surrounds the emerging germ tube and the growing hypha. High resolution autoradiography showed that H N-acetyl-glucosamine , a precursor of chitin, was incorporated preferentially in the thin inner layer of the spore wall and also in the cell wall of the growing hypha. When the label was fed to the infected cells, at different intervals after inoculation, grains were observed on the sheath which developed around the haustorium of P. virginiana , 30 hours after inoculation. The significance of these results in relation to the origin and composition of the sheath is discussed.
Resumo:
It is well accepted that structural studies with model membranes are of considerable value in understanding the structure of biological membranes. Many studies with models of pure phospholipids have been done; but the effects of divalent cations and protein on these models would make these studies more applicable to intact membrane. The present study, performed with above view, is a structural analysis of divalent io~cardio1ipin complexes using the technique of x-ray diffraction. Cardiolipin, precipitated from dilute solution by divalent ionscalcium, magnesium and barium, contains little water and the structure formed is similar to the structure of pure cardiolipin with low water content. The calcium-cardiolipin complex forms a pure hexagonal type II phase that exists from 40 to 400 C. The molar ratio of calcium and cardiolipin in the complex is 1 : 1. Cardiolipin, precipitated with magnesium and barium forms two co-existing phases, lamellar and hexagonal, the relative quantity of the two phases being dependent on temperature. The hexagonal phase type II consisting of water filled channels formed by adding calcium to cardiolipin may have a remarkable permeability property in intact membrane. Pure cardiolipin and insulin at pH 3.0 and 4.0 precipitate but form no organised structure. Lecithin/cardiolipin and insulin precipitated at pH 3.0 give a pure lamellar phase. As the lecithin/cardiolipin molar ratio changes from 93/7 to SO/50, (a) the repeat distance of the lamellar changes from 72.8 X to 68.2 A; (b) the amount of protein bound increases in such a way that cardiolipin/insulin molar ratio in the complex reaches a maximum constant value at lecithin/cardiolipin molar ratio 70/30. A structural model based on these data shows that the molecular arrangement of lipid and protein is a lipid bilayer coated with protein molecules. The lipid-protein interaction is chiefly electrostatic and little, if any, hydrophobic bonding occurs in this particular system. So, the proposed model is essentially the same as Davson-Daniellifs model of biological membrane.
Resumo:
The thesis assesses the impact of international factors on relations between Greek and Turkish Cypriots during and after the Cold War. Through an analysis of the Cyprus problem it explores both why external actors intervene in communal conflicts and how they influence relations between ethnic groups in plural societies. The analytical framework employed throughout the study draws on contributions of International Relations theorists and students of ethnic conflict. The thesis argues that, as in the global political system, relations between ethnic groups in unranked communal systems are anarchic; that is, actors within the system do not recognize a sovereign political authority. In bipolar communal systems dominated by two relatively equal groups, the struggle for security and power often leads to appeals for assistance from external actors. The framework notes that neighboring states and Great Powers may heed calls for assistance, or intervene without a prior request, if it is in their interest to do so. The convergence of regional and global interests in communal affairs exacerbates ethnic conflicts and precludes the development of effective political institutions. The impact of external intervention in ethnic conflicts has the potential to alter the basis of communal relations. The Cyprus problem is examined both during and after the Cold War in order to gauge how global and regional actors and the structure of their respective systems have affected relations between ethnic groups in Cyprus. The thesis argues that Cyprus's descent into civil war in 1963 was due in part to the entrenchment of external interests in the Republic's constitution. The study also notes that power politics involving the United States, Soviet Union, Greece and Turkey continued to affect the development of communal relations throughout the 1960s, 70s, and, 80s. External intervention culminated in July and August 1974, after a Greek sponsored coup was answered by Turkey's invasion and partition of Cyprus. The forced expulsion of Greek Cypriots from the island's northern territories led to the establishment of ethnically homogeneous zones, thus altering the context of communal relations dramatically. The study also examines the role of the United Nations in Cyprus, noting that its failure to settle the dispute was due in large part to a lack of cooperation from Turkey, and the United States' and Soviet Union's acceptance of the status quo following the 1974 invasion and partition of the island. The thesis argues that the deterioration of Greek-Turkish relations in the post-Cold War era has made a solution to the dispute unlikely for the time being. Barring any dramatic changes in relations between communal and regional antagonists, relations between Greek and Turkish Cypriots will continue to develop along the lines established in July/August 1974. The thesis concludes by affirming the validity of its core hypotheses through a brief survey of recent works touching on international politics and ethnic conflict. Questions requiring further research are noted as are elements of the study that require further refinement.
Resumo:
This thesis examined the role transition from an elementary teacher to an elementary principal. In particular, the training and socialization process of becoming an elementary principal was explored through the study of the hierarchical and political structure of a southern Ontario school board, and how this influenced the learning experiences of new elementary principals. A qualitative methodology, with a grounded theory design, was employed to investigate this process through interviews with 10 participants to examine their experiences and role learning occurs during their development. Specifically, participants perspective shifts, developmental experiences, understanding of group culture, and expansion of a board profile were highlighted in the data. One of the compelling results of the study was the degree to which principals of aspiring administrators influence the socialization of their subordinates. The beliefs and practices of the school principal determine the socialization orientation that teachers and vice-principals will experience during role learning. The results of this study also imply that role orientation needs to be understood as a continuum between custodial and innovative role assumption. Varying degrees of custodianship or innovation depended on the context of the administrative placement and the personal attributes of administrative candidates. Principals who are willing to share responsibilities, who are good communicators, and who wish to develop a collaborative relationship with their viceprincipals are the individuals the participants in this study described as making the best mentors.
Resumo:
In mice, exposure to isoflavones (ISO), abundant in soy infant formula, during the first 5 d of life alters structural and functional development of reproductive organs. Effects of longer exposures are unknown. The study objective was to evaluate whether exposure to a combination of daidzein and genistein in the first 10 compared to 5 d of life results in greater adverse effects on ovarian and uterine structure in adult mice. Thirteen litters of 8–12 pups were cross-fostered and randomized to corn oil or ISO (2 mg daidzein + 5 mg genistein/kg body weight/d) for the first 5 or 10 d of life. The 10-d protocol mimicked the period when infants are fed soy protein formula (SPF) but avoids the time when suckling pups can consume the mother’s diet. Body and organ weights and histology of ovaries and uteri were analyzed. There were no differences in the ovary or uterus weight, number of ovarian follicles, number of multiple oocyte follicles, or percent of ovarian cysts with 5 or 10 d of ISO intervention compared to respective controls. The 10-d ISO group had higher body weights from 6 d to 4 mo. of age and a higher percent of hyperplasia in the oviduct than the respective control. Lower numbers of ovarian corpus lutea and a higher incidence of abnormal changes were reported in the uteri of both ISO groups compared to their respective controls. Five- and 10-d exposure to ISO had similar long-lasting adverse effects on the structures of ovaries and uterus in adult mice. Only the 10-d ISO exposure resulted in greater body weight gain at adulthood.
Resumo:
The skill to identify and use best practices in literacy to promote achievement for students of all abilities cannot be underestimated by elementary educators. This qualitative case study investigates 1 year of a literacy initiative for primary and junior educators organized by a southern Ontario school board. The goals of the initiative were to design a literacy guide for teachers while building teacher capacity with literacy practices. Data were culled and analyzed from an examination of the guide, the meetings’ field notes and artifacts, as well as interviews with the educators at the end of the year. Several themes from the results emerged. The educators perceived the design process as unclear but the collaborative components were deemed valuable. The guide’s incompletion led to mixed reactions from the educators about the guide and its structure. Overall, the first year of the 3-year initiative acted as a catalyst for professional learning on literacy. The findings of this study accentuated the value of training educators to use empirical research to support their practices and professional knowledge. Also, the significance of promoting strong leadership with a comprehensive layout consisting of coherent tangible goals for professional development is highlighted.