Thesis (D.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1992 (Oral Biology). / Includes bibliographical references (leaves 70-84). / The ALG7 gene encodes the tunicamycin-sensitive, dolichol-P-dependent Nacetylglucosamine- 1-phosphate transferase, GPT, that catalyzes the synthesis of the first dolichollinked sugar, Dol-PP-GlcNAc, in the N-glycosylation pathway. ALG7 has been evQlutionarily conserved and is essential for growth in all eukaryotes. The ALG7 gene expression in yeast is known to be regulated in part by the 3' untranslated regions (UTR) of the ALG7 multiple transcripts at the posttranscriptional level. To examine the regulatory features of the mammalian ALG7 gene, cloning and characterization of the hamster ALG7 mRNAs were undertaken. Polymerase chain reaction (PCR) using a single ALG7 gene-specific primer was performed to clone the cDNAs corresponding to the 3' and 5' ends of the ALG7 mRNAs from the Chinese hamster ovary (CHO) cells. The initial Northern blot analysis using a hamster ALG7 genomic DNA as a probe has shown that in the CHO cells the ALG7 gene is transcribed into three major messages, approximately 1.5, 1.9, and 2.2 kb in size. The 1.9 kb transcripts were cloned and sequenced. There is one consensus polyadenylation signal AAUAAA located 12 nucleotides (nt) upstream to the major poly(A) site. Three additional minor poly(A) sites are located at 18, 21 and 29 nt downstream from the AAUAAA sequence in this 1.9 kb class of mRNAs. [TRUNCATED]

The aim of this thesis was to undertake a comprehensive research to study the broadband light absorption enhancement in organic solar cells (OSCs) with different nano-structures, thereby improving short-circuit current density and efficiency. Absorption enhancement in OSCs having different photonic structures, compared to the control planar cell configuration, was analyzed and studied using the optical admittance analysis and finite-difference time-domain (FDTD) method. After a brief overview of the latest progresses made in OSCs, the basic optical principles of light scattering, surface plasmon polaritons (SPPs), localized surface plasmon resonance (LSPR), diffraction effect and waveguide mode, that had been employed for light trapping in OSCs, are discussed. Optical admittance analysis reveals that light absorption in inverted OSCs, based on polymer blend layer of P3HT:PCBM, is always greater than the conventional geometry OSCs fabricated using an ITO/PEDOT:PSS anode. The inverted bulk heterojunction OSCs, made with a pair of an ultrathin Al-modified ITO front cathode and a bi-layer MoO3/Ag anode, exhibited a superior power conversion efficiency (PCE) of 4.16%, which is about 13% more efficient than a control normal OSC. It is shown that the reverse configuration allows improving charge collection at cathode/blend interface and also possessing a dawdling degradation behavior as compared to a control regular OSC in the accelerated aging test. Light absorption enhancement in ZnPc:C60-based OSCs, made with substrates having different structures, for example, surface-modified Ag nanoparticles and 1-D photonic structures, was analyzed. The effect of an ultra-thin plasma-polymerized fluorocarbon film (CFx)-modified Ag nanoparticles ii (NPs)/ITO anode on the performance of OSCs was optimized through theoretical simulation and experimental optimization. This work yielded a promising PCE of 3.5 ± 0.1%, notably higher than that with a bare ITO anode (2.7±0.1%). The work was extended to study the performance of OSCs made with CFx-modified Ag NPs/ITO/polyethylene terephthalate (PET) substrate. The resulting flexible OSCs had a relatively high PCE of 3.1±0.1%, comparable to that of structurally identical OSCs fabricated on ITO-coated glass substrate (PCE of 3.5±0.1%). The distribution of the sizes of the Ag NPs, formed by the thermal evaporation, was over the range from 2.0 nm to 10 nm. The results reveal that the localized surface plasmon resonance, contributing to the broadband light absorption enhancement in the organic photoactive layer, was strongly influenced by the size of Ag NPs and the dielectric constant of the surrounding medium. A new OSC structure incorporating a transparent PMMA/ITO double layer grating electrode was also developed. 1-D PMMA/ITO double layer grating, fabricated using nano-imprinting and low processing temperature ITO sputtering method, has a period of 500 nm. Light absorption in grating OSCs under TM, TE and TM/TE hybrid polarizations was calculated using FDTD simulation in the wavelength range from 400 nm to 800 nm. We profiled the electric field distribution and analyzed the structural requirement for confining the waveguide modes in the organic photoactive layer. The effects of the periodicity and the pitch size on light scattering, simultaneous excitation of horizontally propagating SPPs, LSPR and the waveguide modes for light harvesting in grating OSCs were analyzed. The efficiency enhancement in the grating OSCs (PCE 3.29%) over the planar control device (PCE 2.86%) is primarily due to the increase in the short-circuit current density from 11.93 mA/cm2 to 13.57 mA/cm2 (13.7% enhancement). The theoretical results agree with the experimental findings in showing that the improved performance in grating OSCs is attributed to the absorption enhancement in the active layer

Mucosal-associated invariant T (MAIT) cells are a population of innate-like lymphocytes within the gut, liver and blood, expressing a semi-invariant T cell receptor (TCR) and high levels of the C-type lectin-like receptor, CD161. These cells recognise a metabolite of the microbial riboflavin synthesis pathway, presented by the highly conserved Major Histocompatibility Complex (MHC) class I-related protein, MR1, and are critical for the control of bacterial infections. The factors regulating the broad effector functions of MAIT cells have not been fully investigated. Utilising a novel flow cytometric killing assay, MAIT cells were shown here to require the induction of a cytotoxic phenotype through bacterial stimulation to efficiently kill target cells. Further in depth phenotypic analysis highlighted a distinct non-cytotoxic subset of CD4+ MAIT cells, with an altered cytokine-producing capacity, enriched within lymphoid tissues. Investigation into the potential role of these cells in psoriatic diseases revealed that MAIT cells within the synovial fluid of psoriatic arthritis patients are potently activated with increased IL-17 production, their frequency correlating with measures of clinical activity. MAIT cells also have an innate-like responsiveness to cytokines, a feature originally attributed to Natural Killer (NK) cells. Microarray analysis and mass cytometry experiments demonstrated that CD161 marks immature NK cells that have retained this ability to respond to innate cytokines during their differentiation, and is lost upon cytomegalovirus (CMV)-induced maturation in both healthy and human immunodeficiency virus (HIV)-infected patients. Thus, CD161 marks cells with innate-effector functions both in T cells and NK cells.

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( i) A linear circuit is shown not to explain the behaviour of a conductivity cell towards a long rectangular pulse of amplitude less than the decomposition potential of the solution in the cell. (ii) It is shown that the flow of current through the cell is governed by diffusion to the electrode. The diffusion current expression is the familiar one used in the case of diffusion up to a plane micro-electrode, except that in this case the concentration in the layer next to the electrode is not zero, but only somewhat less than the bulk concentration. (iii) Except during a short initial period (less than 10 seconds), the resistance of the electrolytic cell varies directly with the square root of the time for which an e.m.f. (less than the decomposition potential) is applied to the cell, and inversely with the concentration difference between the electrode surface and the bulk of the solution.

Photovoltaic (PV) modules based on thin film systems of CuInSe2 (CIS) and its alloys on low cost substrates are promising candidates to meet the long term efficiency, reliability and manufacturing cost goals. The attention to the CIS solar cell technology is because of the high absorption coefficient of the solar cell absorber layer. Solar cells and PV modules are conventionally assessed by measuring the currentvoltage characteristic of the device. This thesis presents an assessment procedure developed capable of assessing the device parameters with reference to I-V measurements. This thesis then characterizes the performance of the CIS based solar cells and modules in conjunction with other PV modules of different technologies such as crystalline Silicon modules by analyzing the light and dark I-V measurements of the devices. The light and dark I-V characteristics of PV devices were investigated and device parameters were extracted from the I-V data. The extraction and interpretation of these device parameters has a variety of important applications. It has been proven that the device parameters can be used for quality control during production and to provide insights into the operation of the PV devices, thereby improving the efficiency of the devices. The assessment comprises light I-V measurements at standard test conditions (STC), irradiance dependence measurements, parasitic series and shunt resistances measurements and the dark I-V measurements of the PV devices. The PV modules assessed comprise different technologies, namely, thin film based modules (CIS and a-Si) and multicrystalline Si and Edged-defined Film-fed Growth Si (EFG-Si). The dark I-V measurements results showed that the EFG-Si module has acceptable shunt (900 W) and series (0.4 W) resistances, thereby leading to the higher power output depicted from the light I-V measurements. The low quality cells of a-Si module were so low that the fill factor was the smallest (43%). In addition, the dark I-V measurements results revealed that CIS modules are less dependent to temperature at high voltages.

The distribution of vimentin intermediate filaments in Sertoli cells during spermatogenesis was observed with immunofluorescence, and was confirmed with electron microscopy. The distribution of vimentin filaments within Sertoli cells changes with changes in the germ cell population. At stages where elongate spermatids reside in crypts located deep within the seminiferous epithelium, groups of eight to twelve intermediate filaments were consistently found at the convex surface of the spermatid heads. Here the filaments are in close association with ectoplasmic specializations. At later stages of spermatogenesis, intermediate filaments are not found in crypt areas. Because of their association with particular stages of developing germ cells, intermediate filaments in Sertoli cells may be involved in the attachment and positioning of developing germ cells within the seminiferous epithelium. Intermedate filaments in general are thought to be involved in anchoring the nucleus and cytoplasmic organelles within a cell. In order to test this hypothesis, acrylamide, a specific perturbant of intermediate filaments in vitro, was perfused through rat and ground squirrel testes in order to perturbate the intermediate filament system within Sertoli cells. No effects of acrylamide on intermediate filaments were observed in vivo at either the light microscopic or ultrastructural level. However, toxic effects were observed upon treatment with high concentrations of acrylamide, indicating that Sertoli cells and associated germ cells were indeed exposed to the perturbant. Based on these studies, one can conclude that: (1) vimentin filaments in Sertoli cells change their distribution during spermatogenesis; (2) vimentin filaments are closely associated with specific stages of developing germ cells, and may be involved in the positioning and attachment of these cells to Sertoli cells within the seminiferous epithelium, and (3) acrylamide has no effect on vimentin filaments in Sertoli cells in vivo. / Medicine, Faculty of / Graduate

The suppressor circuit and it's components have been studied extensively in this laboratory and others for the past ten years. This laboratory has produced factor-secreting hybridoma cells which are analogous to first-order T suppressor cells directed against the tumor P815 . A monoclonal antibody has been raised which recognizes a common portion of suppressor cells and factors. These tools are used in this study. It had been seen that when 20 µg A10F (factor secreted by A10, the Ts1 analogue) was injected into a mouse concurrently with P815, the suppression of the mouse's immune response was boosted. This led to increased tumor growth and accelerated death. However, when A10F was injected ten days prior to the mouse receiving P815, the opposite effect was seen. Mice had smaller tumors and longer survival times. This was not the contrasuppressive effect described by other laboratories, as the effect seen was not merely an abrogation of suppression, but rather enhancement of the immune response. The specificity and dose response of the effect was examined. This immune enhancement effect was not specific within the context of syngeneic tumor systems. It was found that the same effects were seen when P815 was replaced with L1210 or M-1, both also being H-2d tumors. In fact, L1210 was more sensitive to A10F than P815. There was some level of specificity to the enhancement effect. When A10F was replaced with Fd11F, a suppressor factor raised to ferredoxin, no effect was seen. Conversely, A10F did not produce the same effects as Fd11F in the ferredoxin system. Suppressor deletion therapy was used in both of these systems to confirm that suppressor cells were responsible for the effects seen. Dose response studies showed that the enhancement effect was dose dependent. Doses of A10F below 20 µg did not produce enhancement in the P815 system. Enhancement was seen with lower doses of A10F in the L1210 system, but the effect did decrease at the lower doses. A model is proposed for the data presented. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate