Nonreciprocal Wavefront Engineering with Time-Modulated Gradient Metasurfaces

We propose a paradigm to realize nonreciprocal wavefront engineering using time-modulated gradient metasurfaces. The essential building block of these surfaces is a subwavelength unit cell whose reflection coefficient oscillates at low frequency. We demonstrate theoretically and experimentally that such modulation permits tailoring the phase and amplitude of any desired nonlinear harmonic and determines the behavior of all other emerging fields. By appropriately adjusting the phase delay applied to the modulation of each unit cell, we realize time-modulated gradient metasurfaces that provide efficient conversion between two desired frequencies and enable nonreciprocity by (i) imposing drastically different phase gradients during the up/down conversion processes and (ii) exploiting the interplay between the generation of certain nonlinear surface and propagative waves. To demonstrate the performance and broad reach of the proposed platform, we design and analyze metasurfaces able to implement various functionalities, including beam steering and focusing, while exhibiting strong and angle-insensitive nonreciprocal responses. Our findings open an alternative direction in the field of gradient metasurfaces, in which wavefront control and magnetic-free nonreciprocity are locally merged to manipulate the scattered fields

Implementation of routine first trimester combined screening for pre-eclampsia: a clinical effectiveness study.

OBJECTIVE: Evaluate clinical effectiveness of the first trimester combined (FMF) pre-eclampsia screening programme when implemented in a public healthcare setting. DESIGN: Retrospective cohort study. SETTING: London tertiary hospital from January 2017 to March 2019. METHODS: 7720 women screened for pre-eclampsia according to National Institute for Health and Care Excellence (NICE) risk-based guidance and 4841 by the Fetal Medical Foundation (FMF) algorithm which combined maternal risk factors, blood pressure, PAPP-A and uterine artery Doppler indices in the first trimester. High risk was defined by standard NICE criteria in the pre-intervention cohort (prescribed 75 mg aspirin) or a risk of ≥1:50 for preterm pre-eclampsia from the FMF algorithm in the post-intervention cohort (prescribed 150 mg aspirin). MAIN OUTCOME MEASURES: Screening effectiveness, rates of pre-eclampsia. RESULTS: The FMF screening programme resulted in a significant reduction in the screen-positive rate (16.1 versus 8.2%, odds ratio [OR] 0.50, 95% confidence interval [CI] 0.41-0.53) with a concurrent increase in targeted aspirin use in women classified as high risk for pre-eclampsia (28.9 versus 99.0%, OR 241.6, 95% CI 89.6-652.0). Screening indices were uniformly improved for the FMF algorithm with receiver operating characteristic (ROC) analysis demonstrating excellent discrimination for preterm pre-eclampsia (area under the curve [AUC] = 0.846, 95% CI 0.778-0.915, P value <.001). Interrupted time series analysis showed that the FMF screening programme resulted in a significant 21-month relative effect reduction of 80% (P = .025) and 89% (P = .017), for preterm and early pre-eclampsia, respectively. CONCLUSIONS: First trimester combined screening for pre-eclampsia is both feasible and effective in a public healthcare setting. Such an approach results in a two-fold de-escalation of risk, doubling of pre-eclampsia detection, near total physician compliance of aspirin use and a significant reduction in the prevalence of preterm pre-eclampsia. TWEETABLE ABSTRACT: Implementation of 1st trimester combined pre-eclampsia screening effectively reduces prevalence of the disorder

Niche partitioning of feather mites within a seabird host, Calonectris borealis

According to classic niche theory, species can coexist in heterogeneous environments by reducing interspecific competition via niche partitioning, e.g. trophic or spatial partitioning. However, support for the role of competition on niche partitioning remains controversial. Here, we tested for spatial and trophic partitioning in feather mites, a diverse and abundant group of arthropods. We focused on the two dominant mite species, Microspalax brevipes and Zachvatkinia ovata, inhabiting flight feathers of the Cory's shearwater, Calonectris borealis. We performed mite counts across and within primary and tail feathers on free-living shearwaters breeding on an oceanic island (Gran Canaria, Canary Islands). We then investigated trophic relationships between the two mite species and the host using stable isotope analyses of carbon and nitrogen on mite tissues and potential host food sources. The distribution of the two mite species showed clear spatial segregation among feathers; M. brevipes showed high preference for the central wing primary feathers, whereas Z. ovata was restricted to the two outermost primaries. Morphological differences between M. brevipes and Z. ovata support an adaptive basis for the spatial segregation of the two mite species. However, the two mites overlap in some central primaries and statistical modeling showed that Z. ovata tends to outcompete M. brevipes. Isotopic analyses indicated similar isotopic values for the two mite species and a strong correlation in carbon signatures between mites inhabiting the same individual host suggesting that diet is mainly based on shared host-associated resources. Among the four candidate tissues examined (blood, feather remains, skin remains and preen gland oil), we conclude that the diet is most likely dominated by preen gland oil, while the contribution of exogenous material to mite diets is less marked. Our results indicate that ongoing competition for space and resources plays a central role in structuring feather mite communities. They also illustrate that symbiotic infracommunities are excellent model systems to study trophic ecology, and can improve our understanding of mechanisms of niche differentiation and species coexistence

TREX-DM: a low background Micromegas-based TPC for low mass WIMP detection

Dark Matter experiments are recently focusing their detection techniques in low-mass WIMPs, which requires the use of light elements and low energy threshold. In this context, we present the TREX-DM experiment, a low background Micromegas-based TPC for low-mass WIMP detection. Its main goal is the operation of an active detection mass $\sim$0.300 kg, with an energy threshold below 0.4 keVee and fully built with previously selected radiopure materials. This article describes the actual setup, the first results of the comissioning in Ar+2\%iC$_4$H$_{10}$ at 1.2 bar and the future updates for a possible physics run at the Canfranc Underground Laboratory in 2016. A first background model is also presented, based on Geant4 simulations and a muon/electron discrimination method. In a conservative scenario, TREX-DM could be sensitive to DAMA/LIBRA and other hints of positive WIMPs signals, with some space for improvement with a neutron/electron discrimination method or the use of other light gases.Comment: Proceedings of the 7th Symposium on Large TPCs for Low-Energy Rare Event Detectio

Effect of the Diesel, Inhibitor, and CO 2

In order to determine the diesel contribution in the coadsorption process of the oil-soluble inhibitors, electrochemical impedance spectroscopy measurements have been carried out to study the performance of oil-soluble inhibitors in both presence and absence of diesel and CO2. The results showed that the presence of the oil phase provides some protection to the steel because the water-soluble fractions are capable of being adsorbed on the steel surface thereby reducing the corrosion rate. The oily phase does not contribute to the adsorption process of the inhibitor because the inhibitor is absorbed into the water-soluble fractions. The oil-soluble inhibitors are effective only when the solution is saturated with CO2. CO2 saturation causes a decrease in the pH of the solution causing both an increase of the inhibitor solubility and a better dispersion of the inhibitor into the electrolyte

Infrared spectral fingerprint of neutral and charged endo- and exohedral metallofullerenes

Small metal-containing molecules have been detected and recognized as one of the hybrid species efficiently formed in space; especially in the circumstellar envelopes of evolved stars. It has been predicted also that more complex hybrid species like those formed by metals and fullerenes (metallofullerenes) could be present in such circumstellar environments. Recently, quantum-chemical simulations of metallofullerenes have shown that they are potential emitters contributing to the observed mid-IR spectra in the fullerene-rich circumstellar environments of different types of evolved stars. Here we present the individual simulated mid-IR (~5-50 um) spectra of twenty-eight metallofullerene species; both neutral and charged endo- and exohedral metallofullerenes for seven different metals (Li, Na, K, Ca, Mg, Ti, and Fe) have been considered. The changes induced by the metal-C60 interaction on the intensity and position of the spectral features are highlighted using charge density difference maps and electron density partitioning. Our calculations identify the fundamental IR spectral regions where, depending on the metal binding nature, there should be a major spectral contribution from each of the metallofullerenes. The metallofullerenes IR spectra are made publicly available to the astronomical community, especially James Webb Space Telescope users, for comparisons that could eventually lead to the detection of these species in space.Comment: Accepted for publication in The Astrophysical Journal Supplement Series on 19 September 2023 (in press) (13 pages, 7 figures, and 1 table