M.Ing. (Electrical Engineering Science) / In today's rapidly changing technological environment, more and more importance is being attached to producing products as small as possible to save space as well as materials. Systems today use a wide range of signals, from those used to transmit energy, to small signal electronic signals used for control purposes. As these signals are not very compatible, they must each have their own cable harness to prevent unwanted interference between the signals. As a first step to reducing system size, the control signals (or any signal containing information) may be transmitted on the power transmission line, using techniques investigated in this dissertation. Systems using the same conductors for simultaneous energy and data transmission have many applications ranging from high tech systems to low cost rural communication. Examples of systems where this technology can be applied include: (a) distributed high frequency power systems, where switching of remote equipment can be done from a central point; (b) communication and control in harsh environments such as mining complexes, where switching of fans and motors for example can be done from a central point, while a communication network can be established by placing the information signals on the power cables; and (c) flexible manufacturing cells, where robots can be controlled via the power transmission harness. On the other hand, rural communication systems can be realised over the 50 Hz utility transmission network in remote areas. Such a system has the advantage of offering a low cost solution to providing access to communication to a large number of people spread over a large area. The work described In this dissertation covers two systems, firstly information transmission over the 50 Hz utility network and secondly, the design of a high frequency distributed power system utilising simultaneous information transmission on the transmission line.The first three chapters give an introduction to the technology and discuss the theory which must be applied to make simultaneous energy and information transmission over one conductor viable. Chapter 4 discusses the 50 Hz utility network as an information distribution network. The advantages and disadvantages are discussed, while some solutions are proposed how the disadvantages can be overcome. Chapter 5 discusses a high frequency distributed power system using simultaneous information transmission. The converter design is discussed, while some special design considerations are given which are essential to successful simultaneous information transmission in such a distributed system. To help with the design of the converter used, a simulation was carried out to predict the voltage and current waveforms in such a converter, the results of which can be seen in Appendix B.. The aim of simultaneously transmitting energy and information on the same transmission line was realised in both cases. In the 50 Hz system it was shown that adding external networks to guide the information carrier around obstacles such as 50 Hz power transformers improved the information transmission. A distributed power system however does not need external elements as long as the design of transformers follows the special considerations as described in chapter 5.

The 3C 273 and RX J1230.8+0115 sight lines probe the outskirts of the Virgo Cluster at physical separations between the sight lines of 200 and 500 h70-1 kpc. We present an analysis of available Hubble Space Telescope STIS echelle and Far-Ultraviolet Spectroscopic Explorer (FUSE) UV spectroscopy of RX J1230.8+ 0115, in which we detect five Lyα absorbers at Virgo distances. One of these absorbers is a blend of two strong metal-line absorbers at a recession velocity coincident with the highest neutral hydrogen column density absorber in the 3C 273 sight line, ∼350 h70-1 kpc away. The consistency of the metal-line column density ratios in the RX J1230.8+0115 sight line allows us to determine the ionization mechanism (photoionization) for these absorbers. While the low signal-to-noise ratio of the FUSE spectrum limits our ability to model the neutral hydrogen column density of these absorbers precisely, we are able to constrain them to be in the range 1016-1017 cm -2. The properties of these absorbers are similar to those obtained for the nearby 3C 273 absorber studied by Tripp and collaborators. However, the inferred line-of-sight size for the 3C 273 absorber is only 70 pc, much smaller than those inferred in RX J1230.8+0115, which are 10-30 h70-1 kpc. The small sizes of all three absorbers are at odds with the ≥ 350 h70-1 kpc minimum transverse size implied by an application of the standard QSO line-pair analysis. On the basis of absorber associations between these two sight lines we conclude that a large-scale structure filament produces a correlated, not contiguous, gaseous structure in this region of the Virgo Supercluster. These data may indicate that we are detecting overdensities in the large-scale structure filaments in this region. Alternatively, the presence of a galaxy 71 h70-1 kpc from a 3C 273 absorber may indicate that we have probed outflowing, starburst-driven shells of gas associated with nearby galaxies.

We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) and Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of the QSO PG 1211+143 (zem = 0.081) and a galaxy survey of the surrounding field. This sight line shows two strong intergalactic absorption systems at cz ≃ 15,300 and 19,300 km s-1. This sight line addresses the nature and origin of the O VI absorbers and their connection to galaxies. We explore the relationship of these absorbers to the nearby galaxies and compare them to other O VI-bearing absorbers in diverse environments. At 15,300 km s-1, we find four distinct H I components and associated C II, C III, C IV, Si II, Si III, Si IV, N V, and O VI, lying near a spiral-dominated galaxy group with a bright member galaxy 137 h 70-1 kpc from the sight line. The observed ions of C, Si, and N are likely to be photoionized, but the O VI is more consistent with collisional ionization. The ion ratios in this absorber resemble the highly ionized Galactic high-velocity clouds (HVCs); it may also trace the hot intragroup medium gas or the unbound wind of an undiscovered dwarf galaxy. At 19,300 km s-1, we find five H I components and associated C III, Si III, and collisionally ionized O VI lying 146 h70-1 kpc from an isolated galaxy. The properties of the O VI-bearing gas are consistent with an origin in strong shocks between low-metallicity gas (≥2%-6% solar) and one or more of the warm photoionized components. It is likely that these absorbers are related to the nearby galaxies, perhaps by outflows or gas stripped from unseen satellite galaxies by interactions. However, we cannot reject completely the hypothesis that they reside in the same large-scale structure in which the galaxies are embedded but are otherwise not directly related.

We provide an in-depth analysis of the He II and H I absorption in the intergalactic medium (IGM) at redshifts z = 2.3-2.9 toward HE 2347-4342, using spectra from the Far Ultraviolet Spectroscopic Explorer and the Ultraviolet-Visual Echelle Spectrograph on the Very Large Telescope. Following up on our earlier study, we focus here on two major topics: (1) small-scale variability (Δz ≈ 10-3) in the ratio η = N(He II)/N(H I) and (2) an observed correlation of high-η absorbers (soft radiation fields) with voids in the (H I) Lyα distribution. These effects may reflect fluctuations in the ionizing sources on scales of 1 Mpc, together with radiative transfer through a filamentary IGM whose opacity variations control the penetration of 1-5 ryd radiation over 30-40 Mpc distances. Given the photon statistics and backgrounds, we can measure optical depths over the ranges 0.1 < τHe II < 2.3 and 0.02 < τH I < 3.9 and reliably determine values of η ≈ 4τHe II/τH I over the range 0.1-460. Values η = 20-200 are consistent with models of photoionization by quasars with observed spectral indices α s = 0-3. Values η > 200 may require additional contributions from starburst galaxies, heavily filtered quasar radiation, or density variations. Regions with η < 30 may indicate the presence of local hard sources. We find that η is higher in "void" regions, where H I is weak or undetected and ∼80% of the path length has η > 100. These voids may be ionized by local soft sources (dwarf starbursts) or by QSO radiation softened by escape from the active galactic nucleus cores or transfer through the "cosmic web." The apparent differences in ionizing spectra may help to explain the 1.45 Gyr lag between the reionization epochs of H I (zH I ∼ 6.2 ± 0.2) and He II (zHe II ∼ 2.8 ± 0.2).

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Patrick Jaillet. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1979. / Microfiche copy available in Archives and Science. / Bibliography : leaves 82-83. / by Frank Parker Colby, Jr. / M.S.

ABF-1 is a human class ll basic helix-loop-helix transcription factor that is expressed predominately in EBV immortalized and activated B lymphocytes. A human cell line was stably transfected with a tetracycline regulated ABF-1 expression vector. The cell line revealed tight regulation of ABF-1 expression following stable incorporation of the vector into the genomic DNA. Upon induction of ABF-1 expression, the cell line exhibited a dramatic growth rate decrease. In order to monitor genes regulated by ABF-1, cells were collected both before and after induced ABF-1 expression and subjected to a microarray analysis. Early interpretations of the microarray data support the findings that ABF-1 may be regulating gene expression in a manner that facilitates withdrawal from the cell cycle.

The basic helix-loop-helix protein, activated B-cell factor-l (ABF-l), is a transcription factor involved in cellular proliferation and differentiation. ABF-1 shows patterns of expression that are stimulated in activated B cells, which may suggest ABF-1 is involved in the regulation of B-cell differentiation. To investigate the functional role of ABF-1, we have generated a human plasmacytoma cell line with inducible expression of ABF-1. We were able to induce expression of ABF-1 by using the tetracycline repressor system (teton/off). With addition of tetracycline we were able to stimulate the expression of the full-length ABF-1 in the cells. We also got induction of the truncated form of ABF-1, lacking the protein dimerization domain (HLH), with the addition of tetracycline. We then compared these two cell lines to uninduced cells. We confirmed that ABF-1 expression was induced by western blot analysis. We conclude that we have developed a human plasmacytoma cell line with inducible expression of ABF-1 and can use this cell line for further studies.

Activated B-cell Factor-I (ABF-1) is a class II basic helix-loop-helix protein expressed in activated B-cells, EBV -immortalized lymphoblastoid cell lines and embryonic skeletal muscle in mice. ABF -1 dimerizes with another bHLH protein E4 7 to form a transcriptional repressor ofE2A, which is a gene essential to the proper development of B- and T -cells. In an effort to study genes in B-cells regulated by ABF- 1, I have attempted to construct a Burkitt Lymphoma cell line allowing tetracycline regulated expression of ABF-1. The tetracycline repressor gene was first added to these cells, creating a parental line oftet repression. Next, both a full-length and a truncated version of ABF -1 were added to the cell line. The truncated version of the protein is expressed in the presence of tetracycline, but completely repressed in its absence, demonstrating a tightly-regulated system of inducible expression. The full-length version of ABF-1 has yet to be expressed in this cell line; however, it has been expressed in a HeLa cell line, demonstrating that the construct has been properly made.

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