Channel plasmon-polaritons: modal shape, dispersion, and losses

We theoretically study channel plasmon-polaritons (CPPs) with a geometry similar to that in recent experiments at telecom wavelengths (Bozhevolnyi et al., Nature 440, 508 (2006)). The CPP modal shape, dispersion relation, and losses are simulated using the multiple multipole method and the finite difference time domain technique. It is shown that, with the increase of the wavelength, the fundamental CPP mode shifts progressively towards the groove opening, ceasing to be guided at the groove bottom and becoming hybridized with wedge plasmon-polaritons running along the groove edges.Comment: 4 pages, 4 figure

Antimicrobial activity of nanoconjugated glycopeptide antibiotics and their effect on Staphylococcus Aureus biofilm

In the era of antimicrobial resistance, the use of nanoconjugated antibiotics is regarded as a promising approach for preventing and fighting infections caused by resistant bacteria, including those exacerbated by the formation of difficult-to-treat bacterial biofilms. Thanks to their biocompatibility and magnetic properties, iron oxide nanoparticles (IONPs) are particularly attractive as antibiotic carriers for the targeting therapy. IONPs can direct conjugated antibiotics to infection sites by the use of an external magnet, facilitating tissue penetration and disturbing biofilm formation. As a consequence of antibiotic localization, a decrease in its administration dosage might be possible, reducing the side effects to non-targeted organs and the risk of antibiotic resistance spread in the commensal microbiota. Here, we prepared nanoformulations of the ‘last-resort’ glycopeptides teicoplanin and vancomycin by conjugating them to IONPs via surface functionalization with (3-aminopropyl) triethoxysilane (APTES). These superparamagnetic NP-TEICO and NP-VANCO were chemically stable and NP-TEICO (better than NP-VANCO) conserved the typical spectrum of antimicrobial activity of glycopeptide antibiotics, being effective against a panel of staphylococci and enterococci, including clinical isolates and resistant strains. By a combination of different methodological approaches, we proved that NP-TEICO and, although to a lesser extent, NP-VANCO were effective in reducing biofilm formation by three methicillin-sensitive or resistant Staphylococcus aureus strains. Moreover, when attracted and concentrated by the action of an external magnet, NP-TEICO exerted a localized inhibitory effect on S. aureus biofilm formation at low antibiotic concentration. Finally, we proved that the conjugation of glycopeptide antibiotics to IONPs reduced their intrinsic cytotoxicity toward a human cell line. Copyright © 2021 Berini, Orlandi, Gamberoni, Martegani, Armenia, Gornati, Bernardini and Marinelli

Growth hormone therapy and respiratory disorders: Long-term follow-up in PWS children

Context: Adenotonsillar tissue hypertrophy and obstructive sleep apnea have been reported during short-term GH treatment in children with Prader-Willi syndrome (PWS). Objective: We conducted an observational study to evaluate the effects of long-term GH therapy on sleep-disordered breathing and adenotonsillar hypertrophy in children with PWS. Design: This was a longitudinal observational study. PatientsandMethods:Weevaluated 75 children with genetically confirmedPWS,ofwhom50 fulfilled the criteria and were admitted to our study. The patients were evaluated before treatment (t0), after 6 weeks (t1), after 6 months (t2), after 12 months (t3), and yearly (t4-t6) thereafter, for up to 4 years of GH therapy. The central apnea index, obstructive apnea hypopnea index (OAHI), respiratory disturbance index, and minimal blood oxygen saturation were evaluated overnight using polysomnography. We evaluated the adenotonsillar size using a flexible fiberoptic endoscope. Results: The percentage of patients with an OAHI of 1 increased from 3 to 22, 36, and 38 at t1, t4, and t6, respectively (2 12.2; P .05). We observed a decrease in the respiratory disturbance indexfrom1.4 (t0) to 0.8 (t3) (P.05)andthe centralapneaindexfrom1.2 (t0) to 0.1 (t4) (P.0001). We had to temporarily suspend treatment for 3 patients at t1, t4, and t5 because of severe obstructive sleep apnea. The percentage of patients with severe adenotonsillar hypertrophy was significantly higher at t4 and t5 than at t0. The OAHI directly correlated with the adenoid size (adjusted for age) (P .01) but not with the tonsil size and IGF-1 levels. Conclusion: Long-termGHtreatment in patients withPWSis safe; however,werecommend annual polysomnography and adenotonsillar evaluation

Metagenome-sourced microbial chitinases as potential insecticide proteins

Microbial chitinases are gaining interest as promising candidates for controlling plant pests. These enzymes can be used directly as biocontrol agents as well as in combination with chemical pesticides or other biopesticides, reducing their environmental impact and/or enhancing their efficacy. Chitinolytic enzymes can target two different structures in insects: the cuticle and the peritrophic matrix (PM). PM, formed by chitin fibrils connected to glycoproteins and proteoglycans, represents a physical barrier that plays an essential role in midgut physiology and insect digestion, and protects the absorptive midgut epithelium from food abrasion or pathogen infections. In this paper, we investigate how two recently discovered metagenomesourced chitinases (Chi18H8 and 53D1) affect, in vitro and in vivo, the PM integrity of Bombyx mori, a model system among Lepidoptera. The two chitinases were produced in Escherichia coli or, alternatively, in the unconventional \u2013 but more environmentally acceptable \u2013 Streptomyces coelicolor. Although both the proteins dramatically altered the structure of B. mori PM in vitro, when administered orally only 53D1 caused adverse and marked effects on larval growth and development, inducing mortality and reducing pupal weight. These in vivo results demonstrate that 53D1 is a promising candidate as insecticide protein

Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides

Single surface plasmon polaritons are excited using photons generated via spontaneous parametric down-conversion. The mean excitation rates, intensity correlations and Fock state populations are studied. The observed dependence of the second order coherence in our experiment is consistent with a linear uncorrelated Markovian environment in the quantum regime. Our results provide important information about the effect of loss for assessing the potential of plasmonic waveguides for future nanophotonic circuitry in the quantum regime.Comment: 21 pages, 6 figures, published in Nano Letters, publication date (web): March 27 (2012

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling

A planar slab of negative index material works as a superlens with sub-diffraction-limited imaging resolution, since propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here, we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of wavelength/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy, and thermal sensors.Comment: 20 pages, 6 figures, published as open access article in Nature Communications (see http://www.nature.com/ncomms/

Silver-based surface plasmon waveguide for terahertz quantum cascade lasers

Terahertz-frequency quantum cascade lasers (THz QCLs) based on ridge waveguides incorporating silver waveguide layers have been investigated theoretically and experimentally, and compared with traditional gold-based devices. The threshold gain associated with silver-, gold- and copper-based devices, and the effects of titanium adhesion layers and top contact layers, in both surface-plasmon and double-metal waveguide geometries, have been analysed. Our simulations show that silver-based waveguides yield lower losses for THz QCLs across all practical operating temperatures and frequencies. Experimentally, QCLs with silver-based surface-plasmon waveguides were found to exhibit higher operating temperatures and higher output powers compared to those with identical but gold-based waveguides. Specifically, for a three-well resonant phonon active region with a scaled oscillator strength of 0.43 and doping density of 6.83 × 10¹⁵ cm‾³, an increase of 5 K in the maximum operating temperature and 40% increase in the output power were demonstrated. These effects were found to be dependent on the active region design, and greater improvements were observed for QCLs with a larger radiative diagonality. Our results indicate that silver-based waveguide structures could potentially enable THz QCLs to operate at high temperatures

Macro-scale transport of the excitation energy along a metal nanotrack: exciton-plasmon energy transfer mechanism

Presently we report (i) excited state (exciton) propagation in a metal nanotrack over macroscopic distances, along with (ii) energy transfer from the nanotrack to adsorbed dye molecules. We measured the rates of both of these processes. We concluded that the effective speed of exciton propagation along the nanotrack is about 8 × 107 cm/s, much lower than the surface plasmon propagation speed of 1.4 × 1010 cm/s. We report that the transmitted energy yield depends on the nanotrack length, with the energy emitted from the surface much lower than the transmitted energy, i.e. the excited nanotrack mainly emits in its end zone. Our model thus assumes that the limiting step in the exciton propagation is the energy transfer between the originally prepared excitons and surface plasmons, with the rate constant of about 5.7 × 107 s-1. We also conclude that the energy transfer between the nanotrack and the adsorbed dye is limited by the excited-state lifetime in the nanotrack. Indeed, the measured characteristic buildup time of the dye emission is much longer than the characteristic energy transfer time to the dye of 81 ns, and thus must be determined by the excited state lifetime in the nanotrack. Indeed, the latter is very close to the characteristic buildup time of the dye emission. The data obtained are novel and very promising for a broad range of future applications.PR Institute of Functionalized Nanomaterials NASA EPSCoR grant (NASA Cooperative Agreement) NNX15AK43A National Centre for Research Resources NIH-NCRR-G12-RR03035 NIMHD-G12-MD007583info:eu-repo/semantics/publishedVersio

Roadmap on structured light

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized

Systematic review of dexketoprofen in acute and chronic pain

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Dexketoprofen, an NSAID used in the management of acute and chronic pains, is licensed in several countries but has not previously been the subjected of a systematic review. We used published and unpublished information from randomised clinical trials (RCTs) of dexketoprofen in painful conditions to assess evidence on efficacy and harm. Methods: PubMed and Cochrane Central were searched for RCTs of dexketoprofen for pain of any aetiology. Reference lists of retrieved articles and reviews were also searched. Menarini Group produced copies of published and unpublished studies (clinical trial reports). Data were abstracted into a standard form. For studies reporting results of single dose administration, the number of patients with at least 50 % pain relief was derived and used to calculate the relative benefit (RB) and number-needed-to-treat (NNT) for one patient to achieve at least 50 % pain relief compared with placebo. Results: Thirty-five trials were found in acute pain and chronic pain; 6,380 patients were included, 3,381 receiving dexketoprofen. Information from 16 trials (almost half the total patients) wa