Ultrafast Imaging of Plasmons in a Transmission Electron Microscope

Miniaturized plasmonic and photonic integrated circuits are generally considered as the core of future generations of optoelectronic devices, due to their potential to bridge the size-compatibility gap between photonics and electronics. However, as the nanoscale is approached in increasingly small plasmonic and photonic systems, experimentally observing their behavior involves ever more stringent requirements in terms of both temporal and spatial resolution. This talk focuses on the use of time-resolved Photon-Induced Near-Field Electron Microscopy (PINEM) to study the excitation, propagation, (self-)interference and dynamics of surface plasmon polaritons (SPPs) in various plasmonic nanostructures with both nanometer and ultrafast resolution in a transmission electron microscope. Using this field-ofview technique, we directly show how photo-excited plasmonic interference patterns are controlled through the combination of excitation polarization and nanostructure geometry. Moreover, we capture the propagation of the photoinduced self-interfering plasmonic wave, clearly demonstrating the effects of axial confinement in nanostructured plasmonic thin film stacks

Branching of negative streamers in free flight

We recently have shown that a negative streamer in a sufficiently high homogeneous field can branch spontaneously due to a Laplacian instability, rather than approach a stationary mode of propagation with fixed radius. In our previous simulations, the streamer started from a wide initial ionization seed on the cathode. We here demonstrate in improved simulations that a streamer emerging from a single electron branches in the same way. In fact, though the evolving streamer is much more narrow, it branches after an even shorter propagation distance.Comment: 4 pages, 3 figure

Invasion Percolation with Temperature and the Nature of SOC in Real Systems

We show that the introduction of thermal noise in Invasion Percolation (IP) brings the system outside the critical point. This result suggests a possible definition of SOC systems as ordinary critical systems where the critical point correspond to set to 0 one of the parameters. We recover both IP and EDEN model, for $T \to 0$, and $T \to \infty$ respectively. For small $T$ we find a dynamical second order transition with correlation length diverging when $T \to 0$.Comment: 4 pages, 2 figure

3-Fluoro-4-hydroxyprolines:Synthesis, conformational analysis and stereoselective recognition by the VHL E3 ubiquitin ligase for targeted protein degradation

Hydroxylation and fluorination of proline alters the pyrrolidine ring pucker and the trans:cis amide bond ratio in a stereochemistry-dependent fashion, affecting molecular recognition of proline-containing molecules by biological systems. While hydroxyprolines and fluoroprolines are common motifs in medicinal and biological chemistry, the synthesis and molecular properties of prolines containing both modifications, i.e., fluoro-hydroxyprolines, have not been described. Here we present a practical and facile synthesis of all four diastereoisomers of 3-fluoro-4-hydroxyprolines (F-Hyps), starting from readily available 4-oxo-l-proline derivatives. Small-molecule X-ray crystallography, NMR spectroscopy, and quantum mechanical calculations are consistent with fluorination at C³ having negligible effects on the hydrogen bond donor capacity of the C⁴ hydroxyl, but inverting the natural preference of Hyp from C⁴-exo to C⁴-endo pucker. In spite of this, F-Hyps still bind to the von Hippel–Lindau (VHL) E3 ligase, which naturally recognizes C⁴-exo Hyp in a stereoselective fashion. Co-crystal structures and electrostatic potential calculations support and rationalize the observed preferential recognition for (3<i>R</i>,4<i>S</i>)-F-Hyp over the corresponding (3<i>S</i>,4<i>S</i>) epimer by VHL. We show that (3<i>R</i>,4<i>S</i>)-F-Hyp provides bioisosteric Hyp substitution in both hypoxia-inducible factor 1 alpha (HIF-1α) substrate peptides and peptidomimetic ligands that form part of PROTAC (proteolysis targeting chimera) conjugates for targeted protein degradation. Despite a weakened affinity, Hyp substitution with (3<i>S</i>,4<i>S</i>)-F-Hyp within the PROTAC MZ1 led to Brd4-selective cellular degradation at concentrations >100-fold lower than the binary <i>K</i>_d for VHL. We anticipate that the disclosed chemistry of 3-fluoro-4-hydroxyprolines and their application as VHL ligands for targeted protein degradation will be of wide interest to medicinal organic chemists, chemical biologists, and drug discoverers alike

Indoor free space optics link under the weak turbulence regime: measurements and model validation

This paper is a postprint of a paper submitted to and accepted for publication in [journal] and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital LibraryIn this study, the authors present the measurements performed on a free space optics (FSO) communications link using an indoor atmospheric chamber. In particular, the authors have generated several different optical turbulence conditions, demonstrating how even the weak turbulence regime can strongly affect the FSO link performance. The authors have carried out an in-depth analysis of the data collected during the measurements, and calculated the turbulence strength (i.e. scintillation index and Rytov variance) and the important performance metrics (i.e. the Q-factor and bit error rate) to evaluate the FSO link quality. Moreover, the authors have tested, for the first time, an appositely developed temporally-correlated gamma-gamma channel model to generate the temporal irradiance fluctuations observed at the receiver. This has been accomplished by using a complete analysis tool that enables the authors to fully simulate the experimental FSO link. Finally, the authors compare the generated time-series with the collected experimental data, showing a good agreement and thus proving the effectiveness of the model.This work was supported by the European Space Agency under grant no. 5401001020. We are very grateful to Dr. E. Armandillo for enlightening discussions. J. Perez's work was support by Spanish MINECO Juan de la Cierva Fellowship JCI-2012-14805. This research project falls within the frame of COST ICT Action IC1101 - Optical Wireless Communications - An Emerging Technology (OPTICWISE).Pernice, R.; Ando, A.; Cardinale, M.; Curcio, L.; Stivala, S.; Parisi, A.; Busacca, AC.... (2015). Indoor free space optics link under the weak turbulence regime: measurements and model validation. IET Communications. 9(1):62-70. https://doi.org/10.1049/iet-com.2014.0432S627091Tsukamoto, K., Hashimoto, A., Aburakawa, Y., & Matsumoto, M. (2009). The case for free space. IEEE Microwave Magazine, 10(5), 84-92. doi:10.1109/mmm.2009.933086Suriza, A. Z., Md Rafiqul, I., Wajdi, A. K., & Naji, A. W. (2013). Proposed parameters of specific rain attenuation prediction for Free Space Optics link operating in tropical region. Journal of Atmospheric and Solar-Terrestrial Physics, 94, 93-99. doi:10.1016/j.jastp.2012.11.008Nebuloni, R. (2005). Empirical relationships between extinction coefficient and visibility in fog. Applied Optics, 44(18), 3795. doi:10.1364/ao.44.003795García-Zambrana, A., Castillo-Vázquez, C., & Castillo-Vázquez, B. (2011). Outage performance of MIMO FSO links over strong turbulence and misalignment fading channels. Optics Express, 19(14), 13480. doi:10.1364/oe.19.013480Shokrollahi, A. (2006). Raptor codes. IEEE Transactions on Information Theory, 52(6), 2551-2567. doi:10.1109/tit.2006.874390MacKay, D. J. C. (2005). Fountain codes. IEE Proceedings - Communications, 152(6), 1062. doi:10.1049/ip-com:20050237Uysal, M., Jing Li, & Meng Yu. (2006). Error rate performance analysis of coded free-space optical links over gamma-gamma atmospheric turbulence channels. IEEE Transactions on Wireless Communications, 5(6), 1229-1233. doi:10.1109/twc.2006.1638639Tsiftsis, T. A. (2008). Performance of heterodyne wireless optical communication systems over gamma-gamma atmospheric turbulence channels. Electronics Letters, 44(5), 373. doi:10.1049/el:20083028Popoola, W. O., & Ghassemlooy, Z. (2009). BPSK Subcarrier Intensity Modulated Free-Space Optical Communications in Atmospheric Turbulence. Journal of Lightwave Technology, 27(8), 967-973. doi:10.1109/jlt.2008.2004950Nistazakis, H. E., Tsiftsis, T. A., & Tombras, G. S. (2009). Performance analysis of free-space optical communication systems over atmospheric turbulence channels. IET Communications, 3(8), 1402. doi:10.1049/iet-com.2008.0212Bayaki, E., Schober, R., & Mallik, R. (2009). Performance analysis of MIMO free-space optical systems in gamma-gamma fading. IEEE Transactions on Communications, 57(11), 3415-3424. doi:10.1109/tcomm.2009.11.080168Anguita, J. A., Neifeld, M. A., Hildner, B., & Vasic, B. (2010). Rateless Coding on Experimental Temporally Correlated FSO Channels. Journal of Lightwave Technology, 28(7), 990-1002. doi:10.1109/jlt.2010.2040136Andò, A., Mangione, S., Curcio, L., Stivala, S., Garbo, G., Pernice, R., & Busacca, A. C. (2013). Recovery Capabilities of Rateless Codes on Simulated Turbulent Terrestrial Free Space Optics Channel Model. International Journal of Antennas and Propagation, 2013, 1-8. doi:10.1155/2013/692915Ghassemlooy, Z., Le Minh, H., Rajbhandari, S., Perez, J., & Ijaz, M. (2012). Performance Analysis of Ethernet/Fast-Ethernet Free Space Optical Communications in a Controlled Weak Turbulence Condition. Journal of Lightwave Technology, 30(13), 2188-2194. doi:10.1109/jlt.2012.2194271Xiaoming Zhu, & Kahn, J. M. (2002). Free-space optical communication through atmospheric turbulence channels. IEEE Transactions on Communications, 50(8), 1293-1300. doi:10.1109/tcomm.2002.800829Xu, F., Khalighi, A., Caussé, P., & Bourennane, S. (2009). Channel coding and time-diversity for optical wireless links. Optics Express, 17(2), 872. doi:10.1364/oe.17.00087

Insight into trade‐off between wood decay and parasitism from the genome of a fungal forest pathogen

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91191/1/j.1469-8137.2012.04128.x.pd

Genetic signatures of parental contribution in black and white populations in Brazil

Two hundred and three individuals classified as white were tested for 11 single nucleotide polymorphisms plus two insertion/deletions in their Y-chromosomes. A subset of these individuals (n = 172) was also screened for sequences in the first hypervariable segment of their mitochondrial DNA (mtDNA). In addition, complementary studies were done for 11 of the 13 markers indicated above in 54 of 107 black subjects previously investigated in this southern Brazilian population. The prevalence of Y-chromosome haplogroups among whites was similar to that found in the Azores (Portugal) or Spain, but not to that of other European countries. About half of the European or African mtDNA haplogroups of these individuals were related to their places of origin, but not their Amerindian counterparts. Persons classified in these two categories of skin color and related morphological traits showed distinct genomic ancestries through the country. These findings emphasize the need to consider in Brazil, despite some general trends, a notable heterogeneity in the pattern of admixture dynamics within and between populations/groups

Selective Growth of Low Stored Energy Grains During δ Sub-solvus Annealing in the Inconel 718 Nickel-Based Superalloy

The microstructure stability during δ sub-solvus annealing in Inconel 718 was investigated, focusing on the conditions that may lead to the development of very large grains (about 100 μm) in a recrystallized fine grained matrix (4 to 5 μm) despite the presence of second-phase particles. Microstructure evolution was analyzed by EBSD (grain size, intragranular misorientation) and SEM (δ phase particles). Results confirm that, in the absence of stored energy, the grain structure is controlled by the δ phase particles, as predicted by the Smith–Zener equation. If the initial microstructure is strained (ε < 0.1) before annealing, then low stored energy grains grow to a large extent, despite the Zener pinning forces exerted by the second-phase particles on the grain boundaries. Those selectively growing grains could be those of the initial microstructure that were the least deformed, or they could result from a nucleation process. The balance of three forces acting on boundary migration controls the growth process: if the sum of capillarity and stored energy driving forces exceeds the Zener pinning force, then selective grain growth occurs. Such phenomenon could be simulated, using a level set approach in a finite element context, by taking into account the three forces acting on boundary migration and by considering a realistic strain energy distribution (estimated from EBSD measurements). © 2015, The Minerals, Metals & Materials Society and ASM International