In a grounded direct current system, motor faults may occur which will not be indicated by ordinary protective devices, but which will affect motor operation or create unsafe conditions. All such faults are manifested by the fact that the current in one lead supplying the motor will be greater than that in the other. This current differential can be made to operate a direct current differential relay. About the two supplying leads, when such a fault occurs, will exist a magnetomotive force. This mmf will set up a flux in the core and armature of a relay which forms a magnetic circuit about the supplying conductors. Since the armature of the relay is balanced on a knife edge, the force of attraction between core and armature which is caused by the flux passing from one to the other will move the armature, and in so doing close a pair of contacts. A model relay was built which operates on this principle. Testing demonstrated that it would operate on a differential of approximately one and one-half amperes and that the relay would release when the differential was reduced to approximately four-tenths amperes. The test also showed that these differentials did not vary when the total currents involved changed. These results indicate that a relay built with a slightly different design, (so as to overcome the shortcomings of test model, notably the insecure armature mounting, and so as to provide certain other features, such as control of the current differential for which the relay will operate), would be responsive to current differentials of less than one-half ampere. Such a relay would be a practical device and would be capable of performing, in conjunction with a second, conventional, relay and a circuit breaker, an important control function. / M.S.

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 98-100). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 98-100). Also available on the Internet.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Bernard C. Levy. / "July 1984." / Bibliography: p. 34-36. / NSF grant ECS-83-12921 Air Force Office Scientific Research Grant AFOSR-82-0135B

Primary cilia are cellular organelles that protrude into the extracellular space, acting as antennas. They detect a wide range of chemical cues, including SHH and PDGF, as well as fluid flow, and they modulate downstream signalling systems, such as WNT and ERK. Due to this cue-sensing ability and the close association of the primary cilium with the centrosome the organelle is able to influence both cell cycle progression and cell migration. This work investigated the effect of mutations on two genes associated with primary cilia: Arl13b and Ift172. The effects of the HNN genotype of Arl13b and the WIM genotype of Ift172 on cell migration were assessed uniquely within the context of direct current electric fields. Both cell lines showed a decreased migratory response when compared to WT cells, despite no clear involvement of cilia in sensing the direction of the electric field. This corroborated with previous data of in vivo Arl13b cellular migration. Through the use of in utero electroporation the migratory deficits of IFT172 knock down were then confirmed in vivo in the developing mouse neocortex. Further in vitro investigation revealed a slower proliferation rate of HNN and WIM cells, though this was not confirmed in vivo after IFT172 knock down using a standard BrDU protocol. Nevertheless, further in vitro investigations revealed a wide variety of cell cycle and intracellular changes within both cell lines. The commonalities included lower numbers of cells in the S-phase and lower MAPK3 phosphorylation compared to WT, and differences such as GSK3β phosphorylation on Ser9. This work showed for the first time that ciliopathies affect galvanotaxis, and revealed fundamental commonalities in cell migration and proliferation between various ciliary mutations, as well as differences in specific signalling pathways. This will hopefully aid in developing future therapeutic interventions for ciliary diseases.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Additional advisors: Susan Bellis, Vladimir Fast, Chi-Tsou Huang, Donald Muccio. Description based on contents viewed June 23, 2009; title from PDF t.p. Includes bibliographical references.

It was the purpose of this investigation to study the effect of varying the direct to reverse time ratio of periodically-reversed, direct current from 1.0 to 20.0 at an anode current density of 4.5 amperes per square centimeter, and to study the effect of alternating current of 60, 240, and 500 cycles per second, 0.2 to 4.5 amperes per square centimeter, superimposed on direct current on the electrolytic production of peroxydisulfuric acid. Electrolyses of 200 milliliters of sulfuric acid of specific gravity 1.4, at a temperature of 5 to 10 °C were performed with direct current. The anode current density was varied. The surface area of platinum anode and lead cathode was 2.0 and 221.8 square centimeters, respectively. For one hour of electrolysis, the yields were 7.9, 14.0, 20.2, and 22.9 grams of peroxydisulfuric acid at the anode current density of 1.5, 3.0, 4.5, and 6.0 amperes per square centimeter, respectively. The current efficiencies corresponding to these anode current densities were 85.0, 77.0, 61.5, and 53.4 per cent. The results showed that the yield was increased and the current efficiency was decreased with increase in the anode current density. Electrolysis of the same concentration and volume of sulfuric acid using periodically-reversed, direct current yielded 14.2 grams at an anode current density of 4.5 amperes per square centimeter and at a temperature of 5 to 8 °C. The time of electrolysis was one hour and the time ratio of direct to reverse electrolysis was 20. The current efficiency obtained under these conditions was 42.6 per cent. Decreasing the direct to reverse time ratio gave lower yields and current efficiencies. Apparently, there is no advantage in using periodically-reversed, direct current over the use of direct current for this reaction under the above experimental conditions. Electrolyses of 200 milliliters of sulfuric acid of the same concentration were performed with 60 cycles per second, alternating current superimposed on direct current. The direct current density was 4.5 amperes per square centimeter for the ten tests, but the surface area of the platinum anode was changed from two to one square centimeter and the direct current was decreased from 9.0 to 4.5 amperes. The current efficiency decreased sharply from 61.5 to approximately 31.0 per cent as the ratio of peak alternating to direct current increased from zero to 0.2 and then it remained constant until the ratio reached one. The current efficiency decreased suddenly to almost zero when the ratio was greater than one. The same sulfuric acid was electrolyzed under the same experimental conditions with 240 and 500 cycles per second, alternating current superimposed on direct current. Both direct and alternating anode current densities were varied. The direct current density was 2.2 and 4.5 amperes per square centimeter. The current efficiencies obtained during these tests were almost the same as that obtained with 60 cycles per second, alternating current within a specific limit of the ratio of peak alternating to direct current. The ratio of peak alternating current to direct current at which the current efficiencies suddenly dropped to zero was 0.75 for 240 cycles per second, and 0.5 for 500 cycles per second, instead of one for 60 cycles per second, superimposed alternating current. The platinum anode was activated and dissolved into the sulfuric acid when the ratio of peak alternating to direct current was greater than 1.0, 0.75, and 0.5 for 60, 240, and 500 cycles per second, alternating current superimposed on direct current. Apparently, there is no advantage in using alternating current superimposed on direct current over the use of direct current for electrolytic production of peroxydisulfuric acid. / Master of Science