Imaging of Iso-frequency Contours via Resonance-Enhanced Scattering in Near-Pristine Photonic Crystals

The iso-frequency contours of a photonic crystal are important for predicting and understanding exotic optical phenomena that are not apparent from high-symmetry band structure visualizations. Here, we demonstrate a method to directly visualize the iso-frequency contours of high-quality photonic crystal slabs that shows quantitatively good agreement with numerical results throughout the visible spectrum. Our technique relies on resonance-enhanced photon scattering from generic fabrication disorder and surface roughness, so it can be applied to general photonic and plasmonic crystals, or even quasi-crystals. We also present an analytical model of the scattering process, which explains the observation of iso-frequency contours in our technique. Furthermore, the iso-frequency contours provide information about the characteristics of the disorder and therefore serve as a feedback tool to improve fabrication processes.Comment: 8 pages, 5 figure

Exploring how age influences sensory perception, thirst and hunger during the consumption of oral nutritional supplements using the check-all-that-apply methodology

The Check-all-that-apply (CATA) method has been widely used for the sensory characterisation of many different foods and beverages. However, this methodology has been rarely used with older adults. The aim of this study was to measure the effectiveness of the CATA methodology to investigate the differences in sensory perception of Oral Nutritional Supplements (ONS) between younger and community dwelling older adults over successive sips of a full volume of two ONS. The study also sought to measure the effects of ONS on thirst, hunger and fullness. 160 participants (eighty aged over 65 and eighty aged 18-35) evaluated two ONS over two different days. They consumed five 40 ml aliquots of ONS amounting to one serving. After each 40 ml they completed a CATA questionnaire, which recorded liking using a 9-point hedonic scale and hunger, fullness, desire, and thirst using 100 mm visual analogue scales. The results indicated significantly lower levels in hunger (p ≤ 0.01) and thirst (p ≤ 0.01) in the older cohort than the younger cohort. Significant differences in texture perception with age were also observed with the younger cohort selecting ‘Watery’ significantly more (p ≤ 0.05) than the older cohort for ONS 1 and ‘Thick’ and ‘Viscous’ significantly more (p ≤ 0.05) for ONS 2. The study showed that the CATA methodology is appropriate for use with older adults. The findings enhanced our understanding of how an older population experience ONS and drivers of ‘liking’. This information has the potential to enhance ONS adherence and ultimately improve the nutritional status of older people

Substrate-Independent Light Confinement in Bioinspired All-Dielectric Surface Resonators

Traditionally, photonic crystal slabs can support resonances that are strongly confined to the slab but also couple to external radiation. However, when a photonic crystal slab is placed on a substrate, the resonance modes become less confined, and as the index contrast between slab and substrate decreases, they eventually disappear. Using the scale structure of the Dione juno butterfly wing as an inspiration, we present a low-index zigzag surface structure that supports resonance modes even without index contrast with the substrate. The zigzag structure supports resonances that are contained away from the substrate, which reduces the interaction between the resonance and the substrate. We experimentally verify the existence of substrate-independent resonances in the visible wavelength regime. Potential applications include substrate-independent structural color and light guiding.United States. Army Research Office (W911NF-13-D-0001)Solid-State Solar-Thermal Energy Conversion Center (DE-SC0001299)National Science Foundation (U.S.) (1122374

Resolving spin, valley, and moir\'e quasi-angular momentum of interlayer excitons in WSe2/WS2 heterostructures

Moir\'e superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir\'e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moir\'e superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moir\'e quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moir\'e sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moir\'e superlattice and unambiguously determine their spin, valley, and moir\'e QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moir\'e sites can exhibit opposite optical selection rules due to the spatially-varying moir\'e QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moir\'e superlattices for optoelectronic and valleytronic applications

Safety, immunogenicity, and reactogenicity of BNT162b2 and mRNA-1273 COVID-19 vaccines given as fourth-dose boosters following two doses of ChAdOx1 nCoV-19 or BNT162b2 and a third dose of BNT162b2 (COV-BOOST): a multicentre, blinded, phase 2, randomised trial

BACKGROUND: Some high-income countries have deployed fourth doses of COVID-19 vaccines, but the clinical need, effectiveness, timing, and dose of a fourth dose remain uncertain. We aimed to investigate the safety, reactogenicity, and immunogenicity of fourth-dose boosters against COVID-19. METHODS: The COV-BOOST trial is a multicentre, blinded, phase 2, randomised controlled trial of seven COVID-19 vaccines given as third-dose boosters at 18 sites in the UK. This sub-study enrolled participants who had received BNT162b2 (Pfizer-BioNTech) as their third dose in COV-BOOST and randomly assigned them (1:1) to receive a fourth dose of either BNT162b2 (30 μg in 0·30 mL; full dose) or mRNA-1273 (Moderna; 50 μg in 0·25 mL; half dose) via intramuscular injection into the upper arm. The computer-generated randomisation list was created by the study statisticians with random block sizes of two or four. Participants and all study staff not delivering the vaccines were masked to treatment allocation. The coprimary outcomes were safety and reactogenicity, and immunogenicity (anti-spike protein IgG titres by ELISA and cellular immune response by ELISpot). We compared immunogenicity at 28 days after the third dose versus 14 days after the fourth dose and at day 0 versus day 14 relative to the fourth dose. Safety and reactogenicity were assessed in the per-protocol population, which comprised all participants who received a fourth-dose booster regardless of their SARS-CoV-2 serostatus. Immunogenicity was primarily analysed in a modified intention-to-treat population comprising seronegative participants who had received a fourth-dose booster and had available endpoint data. This trial is registered with ISRCTN, 73765130, and is ongoing. FINDINGS: Between Jan 11 and Jan 25, 2022, 166 participants were screened, randomly assigned, and received either full-dose BNT162b2 (n=83) or half-dose mRNA-1273 (n=83) as a fourth dose. The median age of these participants was 70·1 years (IQR 51·6-77·5) and 86 (52%) of 166 participants were female and 80 (48%) were male. The median interval between the third and fourth doses was 208·5 days (IQR 203·3-214·8). Pain was the most common local solicited adverse event and fatigue was the most common systemic solicited adverse event after BNT162b2 or mRNA-1273 booster doses. None of three serious adverse events reported after a fourth dose with BNT162b2 were related to the study vaccine. In the BNT162b2 group, geometric mean anti-spike protein IgG concentration at day 28 after the third dose was 23 325 ELISA laboratory units (ELU)/mL (95% CI 20 030-27 162), which increased to 37 460 ELU/mL (31 996-43 857) at day 14 after the fourth dose, representing a significant fold change (geometric mean 1·59, 95% CI 1·41-1·78). There was a significant increase in geometric mean anti-spike protein IgG concentration from 28 days after the third dose (25 317 ELU/mL, 95% CI 20 996-30 528) to 14 days after a fourth dose of mRNA-1273 (54 936 ELU/mL, 46 826-64 452), with a geometric mean fold change of 2·19 (1·90-2·52). The fold changes in anti-spike protein IgG titres from before (day 0) to after (day 14) the fourth dose were 12·19 (95% CI 10·37-14·32) and 15·90 (12·92-19·58) in the BNT162b2 and mRNA-1273 groups, respectively. T-cell responses were also boosted after the fourth dose (eg, the fold changes for the wild-type variant from before to after the fourth dose were 7·32 [95% CI 3·24-16·54] in the BNT162b2 group and 6·22 [3·90-9·92] in the mRNA-1273 group). INTERPRETATION: Fourth-dose COVID-19 mRNA booster vaccines are well tolerated and boost cellular and humoral immunity. Peak responses after the fourth dose were similar to, and possibly better than, peak responses after the third dose. FUNDING: UK Vaccine Task Force and National Institute for Health Research

Persistence of immunogenicity after seven COVID-19 vaccines given as third dose boosters following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK: three month analyses of the COV-BOOST trial

OBJECTIVES: To evaluate the persistence of immunogenicity three months after third dose boosters. METHODS: COV-BOOST is a multicentre, randomised, controlled, phase 2 trial of seven COVID-19 vaccines used as a third booster dose. The analysis was conducted using all randomised participants who were SARS-CoV-2 naïve during the study. RESULTS: Among the 2883 participants randomised, there were 2422 SARS-CoV-2 naïve participants until D84 visit included in the analysis with median age of 70 (IQR: 30-94) years. In the participants who had two initial doses of ChAd, schedules using mRNA vaccines as third dose have the highest anti-spike IgG at D84 (e.g. geometric mean concentration of 8674 ELU/ml (95% CI: 7461-10085) following ChAd/ChAd/BNT). However, in people who had two initial doses of BNT there was no significant difference at D84 in people given ChAd versus BNT (geometric mean ratio (GMR) of 0.95 (95%CI: 0.78, 1.15). Also, people given Ad26.COV2.S (Janssen; hereafter referred to as Ad26) as a third dose had significantly higher anti-spike IgG at D84 than BNT (GMR of 1.20, 95%CI: 1.01,1.43). Responses at D84 between people who received BNT (15 μg) or BNT (30 μg) after ChAd/ChAd or BNT/BNT were similar, with anti-spike IgG GMRs of half-BNT (15 μg) versus BNT (30 μg) ranging between 0.74-0.86. The decay rate of cellular responses were similar between all the vaccine schedules and doses. CONCLUSIONS: 84 days after a third dose of COVID-19 vaccine the decay rates of humoral response were different between vaccines. Adenoviral vector vaccine anti-spike IgG concentration at D84 following BNT/BNT initial doses were higher than for a three dose (BNT/BNT/BNT) schedule. Half dose BNT immune responses were similar to full dose responses. While high antibody tires are desirable in situations of high transmission of new variants of concern, the maintenance of immune responses that confer long-lasting protection against severe disease or death is also of critical importance. Policymakers may also consider adenoviral vector, fractional dose of mRNA, or other non-mRNA vaccines as third doses