Strong coupling between weakly guided semiconductor nanowire modes and an organic dye

The light-matter coupling between electromagnetic modes guided by a semiconductor nanowire and excitonic states of molecules localized in its surrounding media is studied from both classical and quantum perspectives, with the aim of describing the strong-coupling regime. Weakly guided modes (bare photonic modes) are found through a classical analysis, identifying those lowest-order modes presenting large electromagnetic fields spreading outside the nanowire while preserving their robust guided behavior. Experimental fits of the dielectric permittivity of an organic dye that exhibits excitonic states are used for realistic scenarios. A quantum model properly confirms through an avoided mode crossing that the strong-coupling regime can be achieved for this configuration, leading to Rabi splitting values above 100 meV. In addition, it is shown that the coupling strength depends on the fraction of energy spread outside the nanowire, rather than on the mode field localization. These results open up a new avenue towards strong-coupling phenomenology involving propagating modes in nonabsorbing media

Dynamic regulation of serum aryl hydrocarbon receptor agonists in MS

Objective: Several factors influence the clinical course of autoimmune inflammatory diseases such as MS and inflammatory bowel disease. Only recently, the complex interaction between the gut microbiome, dietary factors, and metabolism has started to be appreciated with regard to its potential to modulate acute and chronic inflammation. One of the molecular sensors that mediates the effects of these environmental signals on the immune response is the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor with key functions in immune cells. Methods: In this study, we analyzed the levels of AHR agonists in serum samples from patients with MS and healthy controls in a case-control study. Results: We detected a global decrease of circulating AHR agonists in relapsing-remitting MS patients as compared to controls. However, during acute CNS inflammation in clinically isolated syndrome or active MS, we measured increased AHR agonistic activity. Moreover, AHR ligand levels in patients with benign MS with relatively mild clinical impairment despite longstanding disease were unaltered as compared to healthy controls. Conclusions: Collectively, these data suggest that AHR agonists in serum are dynamically modulated during the course of MS. These findings may guide the development of biomarkers to monitor disease activity as well as the design of novel therapeutic interventions for MSInstituto de Salud Carlos III, Unión Europea PT13/0010/004

Paper-based ZnO self-powered sensors and nanogenerators by plasma technology

Nanogenerators and self-powered nanosensors have shown the potential to power low-consumption electronics and human-machine interfaces, but their practical implementation requires reliable, environmentally friendly and scalable, processes for manufacturing and processing. This article presents a plasma synthesis approach for the fabrication of piezoelectric nanogenerators (PENGs) and self-powered sensors on paper substrates. Polycrystalline ZnO nanocolumnar thin films are deposited by plasma-enhanced chemical vapour deposition on common paper supports using a microwave electron cyclotron resonance reactor working at room temperature yielding high growth rates and low structural and interfacial stresses. Applying Kinetic Monte Carlo simulation, we elucidate the basic shadowing mechanism behind the characteristic microstructure and porosity of the ZnO thin films, relating them to an enhanced piezoelectric response to periodic and random inputs. The piezoelectric devices are assembled by embedding the ZnO films in PMMA and using Au electrodes in two different configurations: laterally and vertically contacted devices. We present the response of the laterally connected devices as a force sensor for low-frequency events with different answers to the applied force depending on the impedance circuit, i.e. load values range, a behaviour that is theoretically analyzed. The vertical devices reach power densities as high as 80 nW/cm2 with a mean power output of 20 nW/cm2. We analyze their actual-scenario performance by activation with a fan and handwriting. Overall, this work demonstrates the advantages of implementing plasma deposition for piezoelectric films to develop robust, flexible, stretchable, and enhanced-performance nanogenerators and self-powered piezoelectric sensors compatible with inexpensive and recyclable supportsComment: 30 pages, 8 figures in main tex

Island and Mountain Ecosystems as Testbeds for Biological Control in the Anthropocene

For centuries, islands and mountains have incited the interest of naturalists, evolutionary biologists and ecologists. Islands have been the cradle for biogeography and speciation theories, while mountain ranges have informed how population adaptation to thermal floors shapes the distribution of species globally. Islands of varying size and mountains’ altitudinal ranges constitute unique “natural laboratories” where one can investigate the effects of species loss or global warming on ecosystem service delivery. Although invertebrate pollination or seed dispersal processes are steadily being examined, biological control research is lagging. While observations of a wider niche breadth among insect pollinators in small (i.e., species-poor) islands or at high (i.e., colder) altitudes likely also hold for biological control agents, such remains to be examined. In this Perspective piece, we draw on published datasets to show that island size alone does not explain biological control outcomes. Instead, one needs to account for species’ functional traits, habitat heterogeneity, host community make-up, phenology, site history or even anthropogenic forces. Meanwhile, data from mountain ranges show how parasitism rates of Noctuid moths and Tephritid fruit flies exhibit species- and context-dependent shifts with altitude. Nevertheless, future empirical work in mountain settings could clarify the thermal niche space of individual natural enemy taxa and overall thermal resilience of biological control. We further discuss how global databases can be screened, while ecological theories can be tested, and simulation models defined based upon observational or manipulative assays in either system. Doing so can yield unprecedented insights into the fate of biological control in the Anthropocene and inform ways to reinforce this vital ecosystem service under global environmental change scenarios.The development of this manuscript was funded by the Food and Agriculture Organization FAO through LOA/RAP/2021/57, executed by The University of Queensland. AS was supported by the "Ramon y Cajal" program (RYC2020029407-I), financed by the Spanish "Ministerio de Ciencia e Innovacion".info:eu-repo/semantics/publishedVersio

Rhodamine 6G and 800 intermolecular heteroaggregates embedded in PMMA for near-infrared wavelength shifting

The opto-electronic properties of small-molecules and functional dyes usually differ when incorporated into solid matrices with respect to their isolated form due to an aggregation phenomenon that alters their optical and fluorescent properties. These spectroscopic modifications are studied in the framework of the exciton theory of aggregates, which has been extensively applied in the literature for the study of molecular aggregates of the same type of molecules (homoaggregation). Despite the demonstrated potential of the control of the heteroaggregation process (aggregation of different types of molecules), most of the reported works are devoted to intramolecular aggregates, complex molecules formed by several chromophores attached by organic linkers. The intramolecular aggregates are specifically designed to hold a certain molecular structure that, on the basis of the exciton theory, modifies their optical and fluorescent properties with respect to the isolated chromophores that form the molecule. The present article describes in detail the incorporation of Rhodamine 6G (Rh6G) and 800 (Rh800) into polymeric matrices of poly-(methyl methacrylate), PMMA. The simultaneous incorporation of both dyes results in an enhanced fluorescent emission in the near-infrared (NIR), originating from the formation of ground-state Rh6G–Rh800 intermolecular heteroaggregates. The systematic control of the concentration of both rhodamines provides a model system for the elucidation of the heteroaggregate formation. The efficient energy transfer between Rh6G and Rh800 molecules can be used as wavelength shifters to convert effectively the light from visible to NIR, a very convenient wavelength range for many practical applications which make use of inexpensive commercial detectors and systems

Optical coherence tomography characteristics of group 2A idiopathic parafoveal telangiectasis

PURPOSE: To describe the optical coherence tomography (OCT) characteristics of patients with group 2A idiopathic parafoveal telangiectasis (IPFT) and to correlate them with biomicroscopic and fluorescein angiographic (FA) findings based on Gass and Blodi staging classification for group 2A IPFT. METHODS: Fifty-two eyes of 26 consecutive patients with IPFT underwent biomicroscopic fundus examination, color fundus photography, FA, and OCT. Main outcome measures were OCT characteristics and their correlation with biomicroscopy and FA. RESULTS: The most common OCT findings that help differentiate between stages in group 2A IPFT are 1) highly reflective dots in the inner retina that correspond with microvessels seen by FA in Stage 1 (5 eyes [62.5%]); 2) the presence of hyporeflective intraretinal spaces in the absence of retinal thickening and highly reflective dots in the retina in Stage 2 (9 [81.8%] and 10 eyes [90.9%], respectively); 3) in Stage 3, both outer and inner retina exhibit areas of similar high reflectivity. In addition, the retinal pigment epithelium (RPE)/choriocapillaris complex is thickened or disrupted as evidenced by an area of high reflectivity (13 eyes [81.2%]); 4) a highly reflective area nasal or temporal to the fovea in the inner or outer retinal layers in Stage 4 suggesting RPE proliferation and migration (13 eyes [100%]); and 5) a fusiform thickening and duplication of the highly reflective RPE/choriocapillaris complex corresponding to choroidal neovascularization in Stage 5 (4 eyes [100%]). Our OCT characteristics correlated well with biomicroscopic and FA findings for Stages 4 and 5. However, the hyporeflective spaces that are evident on OCT could not be seen clinically at the slit lamp or on FA. In addition, our OCT findings on eyes with group 2A IPFT Stage 3 have not, to our knowledge, been previously described. CONCLUSIONS: Optical coherence tomography findings in group 2A IPFT were characteristic for each stage and may be helpful in making the diagnosis as well as defining the anatomical staging proposed by Gass and Blodi. Optical coherence tomography complements biomicroscopic and FA findings in the evaluation of group 2A IPFT. © The Ophthalmic Communications Society, Inc

Absence of R-Ras1 and R-Ras2 causes mitochondrial alterations that trigger axonal degeneration in a hypomyelinating disease model

Fast synaptic transmission in vertebrates is critically dependent on myelin for insulation and metabolic support. Myelin is produced by oligodendrocytes (OLs) that maintain multilayered membrane compartments that wrap around axonal fibers. Alterations in myelination can therefore lead to severe pathologies such as multiple sclerosis. Given that hypomyelination disorders have complex etiologies, reproducing clinical symptoms of myelin diseases from a neurological perspective in animal models has been difficult. We recently reported that R-Ras1 and/or R-Ras2 mice, which lack GTPases essential for OL survival and differentiation processes, present different degrees of hypomyelination in the central nervous system with a compounded hypomyelination in double knockout (DKO) mice. Here, we discovered that the loss of R-Ras1 and/or R-Ras2 function is associated with aberrant myelinated axons with increased numbers of mitochondria, and a disrupted mitochondrial respiration that leads to increased reactive oxygen species levels. Consequently, aberrant myelinated axons are thinner with cytoskeletal phosphorylation patterns typical of axonal degeneration processes, characteristic of myelin diseases. Although we observed different levels of hypomyelination in a single mutant mouse, the combined loss of function in DKO mice lead to a compromised axonal integrity, triggering the loss of visual function. Our findings demonstrate that the loss of R-Ras function reproduces several characteristics of hypomyelinating diseases, and we therefore propose that R-Ras1 and R-Ras2 neurological models are valuable approaches for the study of these myelin pathologies.Spanish Ministry of Economy and Competitiveness (RTI2018-096303B-C33) to B. C., (RTI2018-096303B-C31) to F. W., and RTI2018-095166B-I00 to C. G. R. and P. L. and Instituto de Salud Carlos III and co-funded by the European Regional Development Fund (ERDF) within the “Plan Estatal de Investigación Científica y Técnica y de Innovación 2017–2020” (RD16/0008/0020; FIS/PI 18-00754

Electron pumping in graphene mechanical resonators

The combination of high frequency vibrations and metallic transport in graphene makes it a unique material for nano-electromechanical devices. In this letter, we show that graphene-based nano-electromechanical devices are extremely well suited for charge pumping, due to the sensitivity of its transport coefficients to perturbations in electrostatic potential and mechanical deformations, with the potential for novel small scale devices with useful applications