Superfocusing, Biosensing and Modulation in Plasmonics

Plasmonics could bridge the gap between photonics and electronics at the nanoscale, by allowing the realization of surface-plasmon-based circuits and plasmonic chips in the future. To build up such devices, elementary components are required, such as a passive plasmonic lens to focus free-space light to nanometre area and an active plasmonic modulator or switch to control an optical response with an external signal (optical, thermal or electrical). This thesis partially focuses on designing novel passive and active plasmonic devices, with a specific emphasis on the understanding of the physical principles lying behind these nanoscale optical phenomena. Three passive plasmonic devices, designed by conformal transformation optics, are numerically studied, including nanocrescents, kissing and overlapping nanowire dimers. Contrary to conventional metal nanoparticles with just a few resonances, these devices with structural singularities are able to harvest light over a broadband spectrum and focus it into well-defined positions, with potential applications in high efficiency solar cells and nanowire-based photodetectors and nanolasers. Moreover, thermo-optical and electrooptical modulation of plasmon resonances are realized in metallic nanostructures integrated with either a temperature-controlled phase transition material (vanadium dioxide, VO2), or ferroelectric thin films. Taking advantage of the high sensitivity of particle plasmon resonances to the change of its surrounding environment, we develop a plasmon resonance nanospectroscopy technique to study the effects of sizes and defects in the metal-insulator phase transition of VO2 at the single-particle level, and even single-domain level. Finally, we propose and examine the use of two-dimensional metallic nanohole arrays as a refractive index sensing platform for future label-free biosensors with good surface sensitivity and high-throughput detection ability. The designed plasmonic devices have great potential implications for constructing nextgeneration optical computers and chip-scale biosensors. The developed plasmon resonance nanospectroscopy has the potential to probe the interfacial or domain boundary scattering in polycrystalline and epitaxial thin films

Removal of nucleus pulposus from the intervertebral disc – the use of chymopapain enhances mechanical removal with rongeurs: a laboratory study

<p>Abstract</p> <p>Background</p> <p>A laboratory study was conducted, on cadaveric sheep spines to develop an effective procedure for removing as much nucleus as possible from an intervertebral disc with minimal disruption to the annulus. The results of many studies involving removal of nucleus, including chemonucleolysis, using chymopapain, have been published but we are not aware of any previous quantitative studies on procedures for removing as much nucleus as possible from the disc.</p> <p>Methods</p> <p>All procedures were performed via a 3 mm trocar. Four procedures were compared: (I) unilateral approach using rongeurs alone, (II) bilateral approach using rongeurs alone, (III) unilateral approach using rongeurs followed by chymopapain and (IV) bilateral approach using rongeurs followed by chymopapain.</p> <p>Results</p> <p>The percentages of nucleus removed were: (I) 34%, (II) 41%, (III) 52% and (IV) 75%; there were significant differences between the four sets of results according to ANOVA.</p> <p>Conclusion</p> <p>Significantly more nucleus is removed using a bilateral than a unilateral approach; significantly more nucleus is removed if chymopapain is used in addition to rongeurs. A brush is useful in removing strands of nucleus loosened by chymopapain.</p

Optimal Power Control Model of Direct Driven PMSG

AbstractIn order to analyze the performances of direct driven PMSG, an optimal power control model which includes maximum power extraction control model under low wind speed and pitch angle control model under high wind speed is established. The concept of the model is analyzed in a 1.5 MW direct drive variable speed permanent magnet synchronous generator (D-PMSG) WECS with back-to-back IGBT frequency converter. Vector control of the generator side rectifier is realized in the grid voltage vector reference frame. Confirmation of models and control schemes is demonstrated by using the EMTDC/PSCAD environment

Novel 24-membered octanuclear manganese(III) metallacrown

A novel octanuclear manganese metalladiazamacrocycle (1) was synthesized employing a new pentadentate ligand N-methacryl-5-methylsalicylhydrazide (H3mamshz) by supramolecular self assembly. The backbone of this metal-organic assembly is a repeating unit of Mn–N–N–Mn linkage that extends to complete a 24-membered cyclic structure involving 8 manganese(III) centers. Successive manganese centers are in an octanuclear cyclic structure. The temperature-dependent magnetic properties show a typical weakly coupled antiferromagnetic behaviour. KEY WORDS: Manganese, Octanuclear, Metalladiazamacrocycle, Pentadentate ligand, Antiferromagnetic behavior Bull. Chem. Soc. Ethiop. 2014, 28(3), 403-408.DOI: http://dx.doi.org/10.4314/bcse.v28i3.

Doping-free complementary WSe2 circuit via van der Waals metal integration.

Two-dimensional (2D) semiconductors have attracted considerable attention for the development of ultra-thin body transistors. However, the polarity control of 2D transistors and the achievement of complementary logic functions remain critical challenges. Here, we report a doping-free strategy to modulate the polarity of WSe2 transistors using same contact metal but different integration methods. By applying low-energy van der Waals integration of Au electrodes, we observed robust and optimized p-type transistor behavior, which is in great contrast to the transistors fabricated on the same WSe2 flake using conventional deposited Au contacts with pronounced n-type characteristics. With the ability to switch majority carrier type and to achieve optimized contact for both electrons and holes, a doping-free logic inverter is demonstrated with higher voltage gain of 340, at the bias voltage of 5.5 V. Furthermore, the simple polarity control strategy is extended for realizing more complex logic functions such as NAND and NOR

CircTADA2A Up-regulates MAPK8 by targeting MiR-214-3p and recruiting EIF4A3 to promote the invasion and migration of non-small cell lung cancer cells

Background. Non-small cell lung cancer (NSCLC) occupies 87% of all lung cancer cases. Due to delayed diagnosis, the prognosis of NSCLC is unfavorable. To improve the survival of patients with NSCLC, more effective therapeutic targets urgently need to be identified. Recently, circular RNAs (circRNAs) have been revealed to play a crucial role in NSCLC progression. Purpose. This research focused on the influence of circTADA2A on the malignant phenotype of NSCLC cells and its in-depth regulatory mechanisms. Methods. RT-qPCR and western blot assays were done to examine the level of gene/protein of interest. Wound healing and transwell assays were conducted to monitor the migration and invasion of NSCLC cells. Bioinformatics tools and mechanistic assays were utilized to delve into the underlying mechanism of circTADA2A in NSCLC cells. Results. The results demonstrated that circTADA2A presented a high expression in NSCLC. CircTADA2A knockdown was revealed to hamper migration and invasion of NSCLC cells. Mechanistically, circTADA2A elevated MAPK8 expression through sequestering miR214-3p and recruiting EIF4A3. Conclusion. CircTADA2A enhances MAPK8 expression by serving as a miR-214-3p sponge and EIF4A3 decoy, consequently promoting invasion and migration of NSCLC cells

Chiral anomaly and the pion transition form factor: Beyond the cutoff

In the presence of a momentum cutoff, effective theories seem unable to faithfully reproduce the so-called chiral anomaly in the Standard Model. A novel prospect to overcome this related issue is discussed herein via the calculation of the γ*π0γ transition form factor Gγ*π0γ(Q2), whose normalization is intimately connected with the chiral anomaly and dynamical chiral symmetry breaking (DCSB). To compute such transition, we employ a contact interaction model of quantum chromodynamics (QCD) under a modified rainbow ladder truncation, which automatically generates a quark anomalous magnetic moment term, weighted by a strength parameter ξ. This term, whose origin is also connected with DCSB, is interpreted as an additional interaction that mimics the complex dynamics beyond the cutoff. By fixing ξ to produce the value of Gγ*π0γ(0) dictated by the chiral anomaly, the computed transition form factor, as well as the interaction radius and neutral pion decay width, turn out to be comparable with QCD-based studies and experimental data