Two-dimensional band structure in honeycomb metal-organic frameworks

Metal-organic frameworks (MOFs) are an important class of materials that present intriguing opportunities in the fields of sensing, gas storage, catalysis, and optoelectronics. Very recently, two-dimensional (2D) MOFs have been proposed as a flexible material platform for realizing exotic quantum phases including topological and anomalous quantum Hall insulators. Experimentally, direct synthesis of 2D MOFs has been essentially confined to metal substrates, where the interaction with the substrate masks the intrinsic electronic properties of the MOF. Here, we demonstrate synthesis of 2D honeycomb metal-organic frameworks on a weakly interacting epitaxial graphene substrate. Using low-temperature scanning tunneling microscopy (STM) and atomic force microscopy (AFM) complemented by density-functional theory (DFT) calculations, we show the formation of 2D band structure in the MOF decoupled from the substrate. These results open the experimental path towards MOF-based designer quantum materials with complex, engineered electronic structures

Scientometric Portrait of Joan C. Durrance, a Respected Researcher in the Community Focused Library Services

The present study attempted to prepare the scientometric portrait of Joan C Durrance, a respected researcher in the community focused library services and a pioneer in the field of community informatics. The study focused on the aspects like Year and age wise publication output, Authorship pattern, Document types, Ranking of Collaborative authors, Preferred journal for communication of research results, Distribution of citations, and Ranking of top cited papers. She has contributed 165 publications including 39 seminar presentations since 1977 to 2011. Year wise growth indicated that she contributed the maximum number of scholarly output in 1996 at the age of 58 years. The pattern and other measures of authorship displayed its strength upon single authored publication. Among the document types most of the documents were Books/ Book Chapters followed by Journal articles. The most preferred journal by Durrance for the publication of her research results was Public Libraries with 7 publications. The top ranked co-author of Joan C Durrance is K. E. Fisher who co-authored 40 papers in 10 years of contributing ages. 61 publications (48.41%) received 2595 citations with an average of 20.6 citations per paper, 65 publications (51.58%) still remained uncited. The most cited paper of Durrance is a journal article published in 2004 and received 434 citations till date. The findings of this study will be beneficial for the researchers of LIS and Scientometric domain

Non linear behaviour of three terminal graphene devices

Graphene, a 2D allotrope of carbon, has, since its synthesis in 2004, taken the world of physicists by storm. By virtue of its unique energy spectrum grapheme exhibit many unique electronic properties - ultra high mobility of charge carriers and ambipolar effect are two of the most important ones. Three terminal ballistic junctions (TBJ), a new class of device, which has in past showed a host of novel non-linear electrical properties when fabricated out of semiconductor hetero structure, can be used to form active devices out of graphene that contravene the latter's gapless nature. In this thesis three terminal junctions were fabricated on both mono- and bilayer graphene. When operated in a push-pull configuration at room temperature both of them displayed near parabolic voltage and current output. Due to the ambipolar effect of graphene the nature of the output curves could be tuned with a back gate voltage. It was observed that the output curves tend to bend upward for operation in the electron transport regime and downward in the hole transport regime. Moreover, the output curves became progressively more non-linear as the back gate voltage drove the system deeper into either of these regimes. Both of these observations were in direct opposition to the data published in earlier literatures. The voltage rectification of the devices was found out to be about 5%. With clearer theoretical understanding of the mechanism and better fabrication strategies it is hoped that three terminal graphene junctions can be used to make rectifiers, frequency multipliers and logic gates capable of performing at high speed and low power

HIV-1 gp120 Mannoses Induce Immunosuppressive Responses from Dendritic Cells

The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 is a vaccine immunogen that can signal via several cell surface receptors. To investigate whether receptor biology could influence immune responses to gp120, we studied its interaction with human, monocyte-derived dendritic cells (MDDCs) in vitro. Gp120 from the HIV-1 strain JR-FL induced IL-10 expression in MDDCs from 62% of donors, via a mannose C-type lectin receptor(s) (MCLR). Gp120 from the strain LAI was also an IL-10 inducer, but gp120 from the strain KNH1144 was not. The mannose-binding protein cyanovirin-N, the 2G12 mAb to a mannose-dependent gp120 epitope, and MCLR-specific mAbs inhibited IL-10 expression, as did enzymatic removal of gp120 mannose moieties, whereas inhibitors of signaling via CD4, CCR5, or CXCR4 were ineffective. Gp120-stimulated IL-10 production correlated with DC-SIGN expression on the cells, and involved the ERK signaling pathway. Gp120-treated MDDCs also responded poorly to maturation stimuli by up-regulating activation markers inefficiently and stimulating allogeneic T cell proliferation only weakly. These adverse reactions to gp120 were MCLR-dependent but independent of IL-10 production. Since such mechanisms might suppress immune responses to Env-containing vaccines, demannosylation may be a way to improve the immunogenicity of gp120 or gp140 proteins

Molecular self-assembly on graphene - structure and effects

Graphene, a two-dimensional allotrope of carbon, has, since its discovery in 2004, taken the world of physics by storm. With its exceptionally high charge-carrier mobility, thermal conductivity, mechanical strength and current density, it has been posited as a serious contender to replace silicon in the semiconductor industry. However, its application in practical electronic circuits require means of opening a sizeable gap in its band-structure and precise control of its doping. Large organic molecules physisorbed on graphene offer a facile route to controllably dope graphene without sacrificing its desirable properties. Under the right conditions these molecules can self-assemble on the surface into periodic, two-dimensional structures and the potential modulation set up thus can potentially lead to opening a band-gap in graphene. Moreover, the electronically inert surface of graphene offers an interesting substrate on which the fundamentals of molecular self-assembly and the electronic properties of the molecules can be studied in detail. This is very important for the potential application of two-dimensional molecular crystals in "bottom-up" fabrication strategies. In this thesis, the structure and electronic properties of self-assembled layers of organic molecules physisorbed on graphene are studied using ultra-high vacuum, low-temperature scanning tunneling microscopy and spectroscopy. First, the assembly of cobalt phthalocyanine on technologically relevant graphene-on-insulator substrates is examined. A direct parallel is established between assembling motifs on graphene on hexagonal boron nitride and epitaxial graphene on iridium; the higher surface corrugation of graphene on silicon dioxide is found to limit the long-range order of the assembly. Next, going beyond conventional studies of close-packed assembly of molecules interacting via van der Waals forces, assemblies driven by directional intermolecular interactions is studied on graphene on iridium. The 3-fold symmetric molecule benzenetribenzoic acid is seen to assemble into extended honeycomb mesh on graphene, with the network being stabilised by linear hydrogen bonds between the molecules; the periodic nanopores are used to pattern the subsequent deposition of cobalt phthalocyanine. The strong electron acceptor tetrafluorotetracyanoquinodimethane has been proposed as a p-type dopant for graphene; at low coverage, its assembly on graphene on iridium is observed to be markedly site-specific. The molecules are charged and show pronounced structural relaxation, pointing towards a novel bonding mechanism on weakly interacting graphene. Finally, exploratory transport experiments on graphene field-effect transistors decorated with a variety of molecules reveal their effect on the charge-carriers of graphene

Murine Herpetic Stromal Keratitis: Cellular and Molecular Mechanisms Involved in its Pathogenesis

Herpetic Stromal Keratitis (HSK) is a leading cause of infectious blindness resulting from corneal infection with herpes simplex virus (HSV-1). Extensive corticosteroid therapy is required to achieve remission and sometimes corneal transplantation is the only means of restoring vision. Murine model research has revealed that the immunological process that clears infection conversely leads to corneal tissue damage. This immune-pathological reaction involves complex interactions of cellular and molecular events. Current knowledge about human and murine HSK pathogenesis is summarized in Part I. Parts II, III and IV progresses this knowledge using knockout and transgenic mice. Results in Part II clarify mechanisms that operate shortly after corneal infection using a mouse with defective neutrophil migration. Impaired corneal neutrophil migration delayed corneal viral clearance causing heightened inflammation in the cornea. The cytokine IL-6, a component of this response, was shown to be capable of inducing VEGF, resulting in an increased angiogenic response and enhanced HSK lesions. These results provide novel insights into the link between viral infection, pro-inflammatory molecules, neutrophil migration, angiogenesis and HSK development. The role of HSV reactive and non-reactive CD8+ T cells in HSK pathogenesis is discussed in Parts III and IV. It has been demonstrated that CD4+ T cells, crucial to the development of HSK, do not require HSV antigen recognition to mediate HSK. Instead they are activated and recruited to the cornea by bystander mechanisms apparently through the action of pro-inflammatory molecules. Our recent results indicate that bystander mechanisms also facilitate corneal recruitment of non-HSV specific CD8+ T cells. However, HSV reactive CD8+ cells were not involved directly in corneal lesions but instead modulated lesion severity and protected mice from lethal HSV induced encephalitis. This latter effect appeared to be due to the ability of HSV specific CD8+ T cells to control viral replication in the peripheral nervous system and thereby prevent spread to both the brain and the cornea. This dissertation presents research aimed at elucidating both molecular and cellular events in HSK pathogenesis. These results will serve as guidelines for future development of more efficient prophylactic and therapeutic strategies

In Vivo Rescue of Defective Memory CD8\u3csup\u3e+\u3c/sup\u3e T Cells by Cognate Helper T Cells

The magnitude and efficacy of CD8+ T cell memory may notably regress, especially if immune induction occurs in the absence of adequate CD4+ help. This report demonstrates that this CD8+ memory malfunction could be remedied if a source of cognate antigen-recognizing helper cells were provided during recall. The inability of adoptive transfer of memory SIINFEKL-specific CD8 cells to reject tumors was overcome if recipients were primed for ovalbumin-specific helper cell responses. Additionally, animals primed for a SIINFEKL-specific memory response and incapable of rejecting the tumor could regain protective immunity if given helper cells. This pattern of CD8+ T cell functional rescue or reprogramming by helper cell transfer was replicated using a Herpes simplex virus antiviral immunity system. Our results could mean that therapeutic vaccine approaches could be designed to compensate situations that have defective CD8+ T cell function

In vivo rescue of defective memory CD8 +

Abstract: The magnitude and efficacy of CD8 T cell memory may notably regress, especially if im-mune induction occurs in the absence of adequate CD4 help. This report demonstrates that this CD8 memory malfunction could be remedied if a source of cognate antigen-recognizing helper cells were provided during recall. The inability of adop-tive transfer of memory SIINFEKL-specific CD8 cells to reject tumors was overcome if recipients were primed for ovalbumin-specific helper cell responses. Additionally, animals primed for a SIINFEKL-specific memory response and incapa-ble of rejecting the tumor could regain protective immunity if given helper cells. This pattern of CD8 T cell functional rescue or reprogramming by helper cell transfer was replicated using a Her-pes simplex virus antiviral immunity system. Our results could mean that therapeutic vaccine ap-proaches could be designed to compensate situa-tions that have defective CD8 T cell function. J

Louis, duc de Noailles to Carl Linnaeus

Louis, duc de Noailles to Carl Linnaeu