Pseudoeffective Cones and Morphisms of Projective Varieties

The cycles on an algebraic variety contain a great deal of information about its geometry. This thesis is concerned with the pseudoeffective cone obtained by taking the closure of the cone of numerical classes of effective cycles on algebraic varieties. Our interest, motivated by different existing lines of research, is in showing when the pseudoeffective cone is not polyhedral in specific examples. We do this by first proving a sufficient criterion for non-polyhedral pseudoeffective cone (also known as Mori cone) for the case of surfaces. We apply this to the case of C x C where C is a smooth curve of genus at least 2. Using induction, we prove that all intermediate cones of cycles on C x ... x C are not polyhedral. Finally, we study the case of surfaces fibered over curve and give a sufficient criterion for when its pseudoeffective cone is not polyhedral.PHDMathematicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146074/1/ashwathr_1.pd

Vagino-cutaneous fistula: unreported, under-reported or unheralded?

Fistulas are communicating tracts between two surfaces, linking structures and planes that should, under normal circumstances, not be in dialogue. They may be congenital or acquired and are most commonly associated with the gastrointestinal and ano-rectal territories, where they link two different organ systems internally, or track outwards, creating a communicating channel between the internal viscera and the skin surface. Vaginal fistulas on occasion result from perineal tears due to traumatic delivery, or less commonly, infection or non-healing of the episiotomy wound, and are of the rectovaginal or vesicovaginal variety. Very rarely, the channel from the vagina tracks to an opening in the skin. This is the report of a patient who developed the rare vagino-cutaneous fistula following a normal vaginal delivery with episiotomy, and review of the limited literature available about the peculiar entity, so rare that no previous reports of vagino-cutaneous fistulas developing after vaginal delivery with episiotomy could be found

Preliminary Investigations of a Novel Dual Evaporator Dual Ejector Refrigeration Cycle

Increasing air conditioning and domestic refrigeration demands pose a massive burden on grid electricity calling for efficient cooling technologies. In this paper, a novel refrigeration architecture -the Dual Evaporator Dual Ejector Cycle (DEDEC) is proposed. The DEDEC utilizes separate high and low-temperature (HT and LT) evaporators and two ejectors, allowing cooling at two different temperatures levels. Compared to the conventional Dual Evaporator Ejector Cycle, the proposed architecture maintains a higher temperature difference between the two evaporators while reducing the throttling losses. This feature finds application for domestic refrigeration where the temperature difference between the fresh food and freezer section is to be maintained. Additionally, the thermal compression provided by the dual ejectors decreases the compressor work, leading to higher COPs than the dual evaporator vapour compression systems. In this study, a steady-state thermodynamic model for the proposed DEDEC is tested for a domestic refrigerator application. A sensitivity study on various cycle parameters is presented. Results based on R134a show that for fixed condensing temperature and LT evaporator temperatures of -15°C and -20°C, the system is able to maintain the HT evaporator at a temperature of -4.3°C and -7.8°C, respectively. Corresponding minimum load ratios (fresh food : freezer) are found to be 1.67 and 1.75, respectively. Compared to a standard vapour compression cycle (VCC) operating in the same conditions, the DEDEC delivers a COP improvement of 31% and 35% respectively. Lastly, the potential of integrating a low-grade heat source such as solar power with the system is analyzed. The ejector motive fluid is preheated, enabling the system to achieve a higher temperature difference between the HT and LT evaporators. The higher temperature difference reduces the dehumidification of air and build-up of frost typically associated with the conventional VCC refrigeration systems. Results indicate that for an LT evaporator temperature of -20°C, a 10°C preheating delivers an additional 4.6°C temperature rise in the HT evaporator, bringing it to -3.2 °C. Compared to the case without heat integration, a 13.6% decrease in COP is noted with heat integration. The additional heat requirement is 28% of the compressor power to be supplied at a temperature greater than 57°C, which is typical of residential solar heater systems. Therefore, DEDEC refrigerators can be readily deployed in residential buildings with solar heating

Co-Emergence of Specialized Endothelial Cells from Embryonic Stem Cells.

A well-formed and robust vasculature is critical to the health of most organ systems in the body. However, the endothelial cells (ECs) forming the vasculature can exhibit a number of distinct functional subphenotypes like arterial or venous ECs, as well as angiogenic tip and stalk ECs. In this study, we investigate the in vitro differentiation of EC subphenotypes from embryonic stem cells (ESCs). Using our staged induction methods and chemically defined mediums, highly angiogenic EC subpopulations, as well as less proliferative and less migratory EC subpopulations, are derived. Furthermore, the EC subphenotypes exhibit distinct surface markers, gene expression profiles, and positional affinities during sprouting. While both subpopulations contained greater than 80% VE-cad+/CD31+ cells, the tip/stalk-like EC contained predominantly Flt4+/Dll4+/CXCR4+/Flt-1- cells, while the phalanx-like EC was composed of higher numbers of Flt-1+ cells. These studies suggest that the tip-specific EC can be derived in vitro from stem cells as a distinct and relatively stable EC subphenotype without the benefit of its morphological positioning in the sprouting vessel

IN VITRO PROPAGATION OF ANGIOPTERIS EVECTA USING SPORES

Techniques of establishing Angiopleris evecta plants  in vitro were studied. Soaking of A. evecta spores in water for 24 hours markedly reduced spore contamination. Soaking of the spores in 1 -2 % of sodium hypochlorite for  less  than 5 minutes allowed satisfactory disinfestation without affecting spore viability. Lower concentration of minerals (1/4 MS), presence of charcoal in the medium and exposure of the spores to light were crucial for spore germination and gainetophytc development of A. evecta. Keywords:   Angiopleris evecta I King fern / spore / MS medium / bleach / light / tissue culture / sporophyte / gamctophyt

In Vitro Propagation of Angiopteris Evecta Using Spores

Techniques of establishing Angiopleris evecta plants in vitro were studied. Soaking of A. evecta spores in water for 24 hours markedly reduced spore contamination. Soaking of the spores in 1 -2 % of sodium hypochlorite for less than 5 minutes allowed satisfactory disinfestation without affecting spore viability. Lower concentration of minerals (1/4 MS), presence of charcoal in the medium and exposure of the spores to light were crucial for spore germination and gainetophytc development of A. evecta