68 research outputs found
Temporal dynamics of light-written waveguides in unbiased liquid crystals
No full textThe control of light by light is one of the main aims in modern photonics. In this context, a fundamental cornerstone is the realization of light-written waveguides in real time, resulting in all-optical reconfigurability of communication networks. Light-written waveguides are often associated with spatial solitons, that is, non-diffracting waves due to a nonlinear self-focusing effect in the harmonic regime. From an applicative point of view, it is important to establish the temporal dynamics for the formation of such light-written guides. Here, we investigate theoretically the temporal dynamics in nematic liquid crystals, a material where spatial solitons can be induced using continuous wave lasers with a few milliwatts of power. We fully address the role of the spatial walk-off and the longitudinal nonlocality in the waveguide formation. We show that for powers large enough to induce light self-steering the beam undergoes several fluctuations before reaching the stationary regime, in turn leading to a much longer formation time for the light-written waveguide
Interaction surface of the transcription terminator Rho required to form a complex with the C-terminal domain of the antiterminator NusG
No full textRho-dependent transcription termination in bacteria requires an interaction between the terminator Rho and the antiterminator NusG. The interaction surface of the Rho–NusG complex is unknown. Here we provide direct evidence that the β-sheet bundle of the C-terminal domain of NusG (NusG-CTD) has the binding determinants for Rho, proving the hypothesis described earlier [Mooney, R. A., Schweimer, K., Rosch, P., Gottesman, M., & Landick, R., (2009). Two structurally independent domains of E. coli NusG create regulatory plasticity via distinct interactions with RNA polymerase and regulators. J. Mol. Biol., 391, 341–358.]. Disulfide bridges can be engineered from NusG-CTD with the surface-exposed amino acids 217 and 224 of Rho, which belong to its P-loop ATPase domain. Mutational analyses of this region of Rho revealed that a hydrophobic pocket, located behind these amino acids of Rho, is the docking site for NusG-CTD. The proximity of this region of Rho to NusG-CTD in the Rho–NusG complex was also confirmed by an efficient fluorescence resonance energy transfer between residue K224 of Rho and residue A168 of NusG-CTD. The identification of the Rho–NusG interaction surface will be useful not only in understanding the role of NusG in the termination process but also in explaining the molecular basis of the involvement of NusG-CTD in recruiting Rho and the ribosome to the same transcription machinery
Electronic, thermoelectric and transport properties of cesium cadmium trifluoride: A DFT study
No full textVariational method in soliton theory
No full textWe have reported earlier the observation of a self-written waveguide inside a bulk methylene blue sensitized poly (Vinyl Alcohol) /Acrylamide photopolymer material [1]. In this work we develop a theoretical model to explain the experimental observation. We reduce the governing equations for the propagation of a low power laser beam through such a medium into the form of nonlinear Schrodinger equation with a cubic-quintic nonlinearity and solve this equation using variational method. It is found that there is agreement between experimental and theoretical results
A Novel Equivalent Circuit for Analysing the Effect of Local Hotspots in Micro PEM Fuel Cells
No full textAbstractThe lifetime of a micro proton exchange membrane fuel cell is hugely dependent on the durability and longevity of the membrane used in the cell. An ideal membrane is expected to have its membrane impedance constant and distributed uniformly throughout. But in practice, the case is quite different. Such non uniformities in the membrane impedance will generate local hotspots in the membrane which has fatal effects such as it reduces the life time of the fuel cell. So it is imperative that we have to analyse the effects of hotspots in the fuel cell. This paper study proposes a novel equivalent circuit to analyse the impedance variations in the fuel cell membrane. The study on the effect of local hotspots in the fuel cell will lead a further research to create the rectifying methodologies for this problem
Evaluation of Tyrosine Kinase receptor (TrK) Expression in Follicular and Plexiform types of Ameloblastoma: An Immunohistochemical study
No full textINTRODUCTION:
Ameloblastoma has two types of cells with different proliferative activity. The peripheral ameloblast like cells are known for their anti -apoptotic character, while the central stellate reticulum like cells are known for their proapoptotic activity. Neurotrophins are proteins with specific roleonnon-neuronal and neuronal cells. High affinity receptors - TrK are present in family of neurotrophins. Trk receptors activation leads to cell differentiation, survival,proliferation, and apoptosis through PI3KIAkt pathway, RasIMAPK pathway, and PLC-yl pathway. This study will evaluate the immunoreactivity of TrKreceptor in follicular and plexiform types of ameloblastoma.
AIM OF THE STUDY:
The study is aimed at evaluating the expression of Tyrosine Kinase receptor (TrK) in ameloblastoma in order to understand the possible role and mechanism of TrK.
OBJECTIVES:
1. To analyze the Immunohistochemical expression pattern of TrK receptor in follicular type of ameloblastoma.
2. To analyze the Immunohistochemical expression pattern of TrK receptor in plexiform type of ameloblastoma.
3. To compare the Immunohistochemical expression pattern of TrK receptor among the follicular and plexiform types of ameloblastoma.
MATERIAL AND METHODS:
The study sample comprises of 20 follicular and 20 plexiform types of ameloblastoma. Two serial sections of 3-4.5 microns thickness of the study samples were sectioned. The sections were stained immunohistochemically using TrKA+B+C primary antibody. Immunohistochemical reactivity were evaluated depending upon the staining intensity as : Negative (-), Positive (+) and Strongly Positive (++).
RESULTS:
4 samples of follicular ameloblastoma and 16samples of plexiform ameloblastoma had positive immuno-expressionfor TrK predominantly in the peripheral preameloblast like cells. The chi square value for the immuno expression between follicular and plexiform ameloblastoma was statistically significant with a p value <.005 .
CONCLUSION:
The positive expression of Trk in ameloblastoma helps in elucidation of the possible intracellular signal regulation mechanism in this tumor survivaland proliferation. The varied expression of Trkcould be the possible reason behind the differed biological behaviour between follicular and plexiform ameloblastoma
Multifunctional aspects of Piriformospora indica in plant endosymbiosis
No full textPiriformospora indica (Hymenomycetes, Basidiomycota) is an endophytic fungus that colonises plant roots, and was originally isolated from Rajasthan desert. It is comparable to Arbuscular Mycorrhizal (AM) fungi in terms of plant growth promotional effects. P. indica has been used as an ideal example to analyse the mechanisms of mutualistic symbiosis. Major benefit of P. indica over AM fungi is that it is axenically cultivable in different synthetic and complex media. A preliminary attempt was made to scrutinise the role of P. indica co-cultivation on seedling vigour of common vegetables like Cucumis sativus L., Abelmoschus esculentus (L.) Moench, Solanum melongena L. and Capsicum annuum L. The positive effect of P. indica co-culture on seedling performance was compared to the effects of growth hormones like indole acetic acid and benzyl amino purine when supplemented to the MS medium at a concentration of 0.1 mg ml−1. An exogenous supply of auxin resulted in enhanced production of roots and cytokinin supplement favoured shoot production, whereas P. indica co-culture favoured simultaneous production of shoot and root over the control. P. indica colonisation inside the roots of C. sativus L. was also successfully established. These preliminary results indicate the prospective role of P. indica in vegetable farming through its favourable effect on plant growth
Modulational instability of optical beams in photorefractive media due to two-wave or parametric four-wave mixing effects
No full textModulational instability in a photorefractive medium is studied in the presence of two-wave mixing. We then propose and derive a model for forward four-wave mixing in the photorefractive medium and investigate the modulational instability induced by four-wave mixing effects. By using the standard linear stability analysis the instability gain is obtained. In both cases, the geometry is such that the effect of self-phase-modulation self-focusing is suppressed and only the holographic focusing nonlinearity is acting
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