Printable Light-Emitting Metasurfaces with Enhanced Directional Photoluminescence.

Nanoimprint lithography is gaining popularity as a cost-efficient way to reproduce nanostructures in large quantities. Recent advances in nanoimprinting lithography using high-index nanoparticles have demonstrated replication of photonic devices, but it is difficult to confer special properties on nanostructures beyond general metasurfaces. Here, we introduce a novel method for fabricating light-emitting metasurfaces using nanoimprinting lithography. By utilizing quantum dots embedded in resin, we successfully imprint dielectric metasurfaces that function simultaneously as both emitters and resonators. This approach to incorporating quantum dots into metasurfaces demonstrates an improvement in photoluminescence characteristics compared to the situation where quantum dots and metasurfaces are independently incorporated. Design of the metasurface is specifically tailored to support photonic modes within the emission band of quantum dots with a large enhancement of photoluminescence. This study indicates that nanoimprinting lithography has the capability to construct nanostructures using functionalized nanoparticles and could be used in various fields of nanophotonic applications.

Purcell Enhancement of a Cavity-Coupled Emitter in Hexagonal Boron Nitride.

Integration of solid-state quantum emitters into nanophotonic circuits is a critical step towards fully on-chip quantum photonic-based technologies. Among potential materials platforms, quantum emitters in hexagonal boron nitride (hBN) have emerged as a viable candidate over the last years. While the fundamental physical properties have been intensively studied, only a few works have focused on the emitter integration into photonic resonators. Yet, for a potential quantum photonic material platform, the integration with nanophotonic cavities is an important cornerstone, as it enables the deliberate tuning of the spontaneous emission and the improved readout of distinct transitions for a quantum emitter. In this work, the resonant tuning of a monolithic cavity integrated hBN quantum emitter is demonstrated through gas condensation at cryogenic temperature. In resonance, an emission enhancement and lifetime reduction are observed, with an estimate for the Purcell factor of ≈15.

Coupling Spin Defects in Hexagonal Boron Nitride to Monolithic Bullseye Cavities.

Color centers in hexagonal boron nitride (hBN) are becoming an increasingly important building block for quantum photonic applications. Herein, we demonstrate the efficient coupling of recently discovered spin defects in hBN to purposely designed bullseye cavities. We show that boron vacancy spin defects couple to the monolithic hBN cavity system and exhibit a 6.5-fold enhancement. In addition, by comparative finite-difference time-domain modeling, we shed light on the emission dipole orientation, which has not been experimentally demonstrated at this point. Beyond that, the coupled spin system exhibits an enhanced contrast in optically detected magnetic resonance readout and improved signal-to-noise ratio. Thus, our experimental results, supported by simulations, constitute a first step toward integration of hBN spin defects with photonic resonators for a scalable spin-photon interface.

Suppressor of cytokine signaling 2 is induced in Huntington's disease and involved in autophagy.

Suppressor of cytokine signaling (SOCS) proteins are primarily feedback inhibitors of cytokine signaling. The two conserved domains of SOCS proteins have distinct functions. Src homology 2 (SH2) domain inhibits cytokine receptor, while SOCS box acts as an E3 ubiquitin ligase. SOCS2, a cytokine signaling suppressor, has been primarily implicated in regulating inflammatory conditions in neuronal diseases. However, SOCS proteins have been suggested to play diverse roles in healthy and diseased nervous system including neurodegenerative disorders. In this study, SOCS2 was found to be upregulated in Huntington's disease and was substantially induced in extended polyglutamine (polyQ)-expressing striatal cells. The induced level was augmented under aging conditions. In extended polyQ-expressing cells, downregulated SOCS2 improved autophagic dysfunction rather than altered inflammatory conditions. Overall, we suggest that SOCS2 involves in regulating autophagy by functioning as an E3 ligase in extended polyQ conditions, and consequently regulates cell damage and cell death type.

Enhanced Emission from Interlayer Excitons Coupled to Plasmonic Gap Cavities.

The emergence of interlayer excitons (IEs) from atomic layered transition metal dichalcogenides (TMDCs) heterostructures has drawn tremendous attention due to their unique and exotic optoelectronic properties. Coupling the IEs into optical cavities provides distinctive electromagnetic environments which plays an important role in controlling multiple optical processes such as optical nonlinear generation or photoluminescence enhancement. Here, the integration of IEs in TMDCs into plasmonic nanocavities based on a nanocube on a metallic mirror is reported. Spectroscopic studies reveal an order of magnitude enhancement of the IE at room temperature and a 5-time enhancement in fluorescence at cryogenic temperatures. Cavity modeling reveals that the enhancement of the emission is attributed to both increased excitation efficiency and Purcell effect from the cavity. The results show a novel method to control the excitonic processes in TMDC heterostructures to build high performance photonics and optoelectronics devices.

Large few-layer hexagonal boron nitride flakes for nonlinear optics.

Hexagonal boron nitride (hBN) is a layered dielectric material with a wide range of applications in optics and photonics. In this work, we demonstrate a fabrication method for few-layer hBN flakes with areas up to 5000µm2. We show that hBN in this form can be integrated with photonic microstructures: as an example, we use a circular Bragg grating (CBG). The layer quality of the exfoliated hBN flake on and off a CBG is confirmed by Raman spectroscopy and second-harmonic generation (SHG) microscopy. We show that the SHG signal is uniform across the hBN sample outside the CBG and is amplified in the center of the CBG.

Photonic Nanobeam Cavities with Nanopockets for Efficient Integration of Fluorescent Nanoparticles.

Integrating fluorescent nanoparticles with high-Q, small mode volume cavities is indispensable for nanophotonics and quantum technologies. To date, nanoparticles have largely been coupled to evanescent fields of cavity modes, which limits the strength of the interaction. Here, we developed both a cavity design and a fabrication method that enable efficient coupling between a fluorescent nanoparticle and a cavity optical mode. The design consists of a fishbone-shaped, one-dimensional photonic crystal cavity with a nanopocket located at the electric field maximum of the fundamental optical mode. Furthermore, the presence of a nanoparticle inside the pocket reduces the mode volume substantially and induces subwavelength light confinement. Our approach opens exciting pathways to achieve tight light confinement around fluorescent nanoparticles for applications in energy, sensing, lasing, and quantum technologies.

Quasi-BIC Resonant Enhancement of Second-Harmonic Generation in WS2 Monolayers.

Atomically thin monolayers of transition metal dichalcogenides (TMDs) have emerged as a promising class of novel materials for optoelectronics and nonlinear optics. However, the intrinsic nonlinearity of TMD monolayers is weak, limiting their functionalities for nonlinear optical processes such as frequency conversion. Here we boost the effective nonlinear susceptibility of a TMD monolayer by integrating it with a resonant dielectric metasurface that supports pronounced optical resonances with high quality factors: bound states in the continuum (BICs). We demonstrate that a WS2 monolayer combined with a silicon metasurface hosting BICs exhibits enhanced second-harmonic intensity by more than 3 orders of magnitude relative to a WS2 monolayer on top of a flat silicon film of the same thickness. Our work suggests a pathway to employ high-index dielectric metasurfaces as hybrid structures for enhancement of TMD nonlinearities with applications in nonlinear microscopy, optoelectronics, and signal processing.

P62 Links the Autophagy Pathway and the Ubiquitin-Proteasome System in Endothelial Cells during Atherosclerosis.

Among autophagy-related molecules, p62/SQSTM1 is an adaptor for identifying and delivering intracellular cargo for degradation. Since ubiquitination is reversible, it has a switch role in autophagy. Ubiquitination is also involved in regulating autophagy in a timely manner. This study aimed to elucidate how p62-mediated autophagy is regulated in human endothelial cells and macrophages under atherosclerotic conditions, focusing on the lysosomal and proteasomal pathways. Co-cultured HUVECs and THP-1 cells were exposed to oxLDL (50 µg/mL) and autophagy was assessed. To downregulate p62, siRNA was administered, and the E3 ligases were inhibited by Heclin or MLN4924 treatment under the condition that cellular inflammatory processes were stimulated by oxLDL simultaneously initiated autophagy. Downregulating p62 induced an alternative degradation system, and the E3 ligases were found to be involved in the progression of atherosclerosis. Collectively, the present study demonstrated that the endothelial lipid accumulation under atherosclerotic conditions was caused by lysosomal dysfunction associated with autophagy.

A Single Chiral Nanoparticle Induced Valley Polarization Enhancement.

Valley polarization is among the most critical attributes of atomically thin materials. However, increasing contrast from monolayer transition metal dichalcogenides (TMDs) has so far been challenging. In this work, a large degree of circular polarization up to 45% from a monolayer WS2 is achieved at room temperature by using a single chiral plasmonic nanoparticle. The increased contrast is attributed to the selective enhancement of both the excitation and the emission rate having one particular handedness of the circular polarization, together with accelerated radiative recombination of valley excitons due to the Purcell effect. The experimental results are corroborated by the optical simulation using the finite-difference time-domain (FDTD) method. Additionally, the single chiral nanoparticle enables the observation of valley-polarized luminescence with a linear excitation. The results provide a promising pathway to enhance valley contrast from monolayer TMDs and utilize them for nanophotonic devices.

Akkermansia muciniphila Prevents Fatty Liver Disease, Decreases Serum Triglycerides, and Maintains Gut Homeostasis.

The objective of this study was to elucidate the effect of intestinal Akkermansia muciniphila bacteria on fatty liver disease. Five-week-old C57BL/6N mice were administered either phosphate-buffered saline (PBS; control) or A. muciniphila at 108 to 109 CFU/ml, and were fed either a 45% fat diet (high-fat diet [HFD]) or a 10% fat diet (normal diet [ND]) for 10 weeks. After 10 weeks, the mice were euthanized, and blood and tissue samples, including adipose tissue, cecum, liver, and brain, were immediately collected. Biochemical and histological analyses were conducted, and the expression levels of related factors were compared to determine the antiobesity effects of Akkermansia muciniphila The gut microbiome was analyzed in fecal samples. Oral administration of A. muciniphila significantly (P < 0.05) lowered serum triglyceride (TG) and alanine aminotransferase (ALT) levels in obese mice. Compared to the non-A. muciniphila-treated group, the expression of SREBP (regulator of TG synthesis in liver tissue) was decreased in the A. muciniphila-treated group. The expression of IL-6 in the liver of obese mice was decreased following the administration of A. muciniphila Furthermore, alterations in the ratio of Firmicutes to Bacteroidetes and the decrease in bacterial diversity caused by the HFD were restored upon the administration of A. muciniphila These results indicate that A. muciniphila prevents fatty liver disease in obese mice by regulating TG synthesis in the liver and maintaining gut homeostasis.IMPORTANCE This study investigated the effect of Akkermansia muciniphila on fatty liver disease. Although some research about the effects of A. muciniphila on host health has been published, study of the relationship between A. muciniphila administration and fatty liver, as well as changes in the gut microbiota, has not been conducted. In this study, we demonstrated that A. muciniphila prevented fatty liver disease by regulation of the expression of genes that regulate fat synthesis and inflammation in the liver.

The role of Pseudomonas aeruginosa DesB in pathogen-host interaction.

Pseudomonas aeruginosa, commonly found in environments, can cause chronic lung disease in immunocompromised patients. In previous study, an aerobic desaturase (DesB) in P. aeruginosa exerted considerable effects on virulence factor production. The objective of this study was to analyze the role of DesB on the virulence traits of P. aeruginosa in the host. For the in vitro experiments, cells and supernatants from wild-type (WT) P. aeruginosa and its desB mutant were collected. The diluted cells were added to the A549 cell monolayer in order to determine cell viability, invasion ability, and/or immune response. For the in vivo experiments, 6-week-old ICR mice were infected with 6-7 log CFU bacterial cells using endotracheal intubation. The ratio of lung weight to body weight and survival rate of each bacterial strain in the lung were measured. The histopathology of lung tissue was also studied. desB mutants exhibited lower cytotoxicity in A549 cells. In addition, more pro-inflammatory cytokines and chemokines were present in desB mutant-treated. In the lungs of mouse model, WT survived longer than desB mutant, and the WT migrated from the lung to the liver and spleen. The results suggest that P. aeruginosa DesB affects the pathogenicity of the organism in the host.

Synergistic effect of Lactobacillus gasseri and Cudrania tricuspidata on the modulation of body weight and gut microbiota structure in diet-induced obese mice.

High-fat diet (HFD)-induced obesity has been associated with alteration of gut microbiota alongside body weight gain. In this study, the synbiotic effect of Lactobacillus gasseri 505 (LG) and Cudrania tricuspidata (CT) in HFD-induced mice was revealed. After feeding mice with high-fat diet for 10 weeks, combination of LG and CT (LG_CT) exhibited the greatest reduction in the final body weight (11.9%). Moreover, microbial diversity significantly increased, and Principal Coordinate Analysis (PCoA) revealed that the LG_CT group showed closer cluster to NORM. At phylum level, the Firmicutes/Bacteroidetes (F/B) ratio increased in HFD, and the abundance of Bacteroidetes was restored by LG and CT. At genus level, notable changes in Alistipes, Desulfovibrio, Bilophila, and Acetatifactor were observed. Helicobacter elevated to 16.2% in HFD and diminished dramatically to less than 0.01% in LG and/or CT. At species level, L. gasseri increased after the administration of LG (0.54%) and LG_CT (1.14%), suggesting that LG may grow and colonize in the gut and CT can function as a prebiotic. Finally, functional analysis revealed certain metabolic factors correlated with body weight and gut microbiota. This study serves as a potential basis for the application of L. gasseri 505 and C. tricuspidata in the prevention and treatment of diet-induced obesity.Key Points • Combination of L. gasseri (LG) and C. tricuspidata (CT) reduced body weight gain.• Microbial diversity significantly increased in LG_CT treatment.• Abundance of microorganisms involved with leanness increased in LG, CT, and LG_CT.• Body weight is associated with some metabolic functions of gut microbiota.

Asymptomatic Clostridium perfringens Inhabitation in Intestine Can Cause Inflammation, Apoptosis, and Disorders in Brain.

Clostridium perfringens (CP) is a foodborne pathogen. The bacterium can also inhabit human gut without symptoms of foodborne illness. However, the clinical symptoms of long-term inhabitation have not been known yet. Therefore, the objective of this study was to elucidate the relationship between intestinal CP and other internal organs. Phosphate-buffered saline (PBS) and CP were orally injected into 5-week-old (YOUNG) and 12-month-old C57BL6/J (ADULT) mice. Gene expression levels related to inflammation (tumor necrosis factor-α [TNF-α], interleukin [IL]-1ß, and IL-6) and oxidative stress (superoxide dismutase [SOD]1, SOD2, SOD3, glutathione reductase [GSR], glutathione peroxidase [GPx]3, and catalase [CAT]) responses were evaluated in the brain, small intestine, and liver. In addition, apoptosis-related (BCL2-associated X [BAX]1 and high-mobility group box-1 [HMGB1]) and brain disorder-related genes (CCAAT-enhancer-binding protein [C/EBP]-ß, C/EBPδ, C/EBP homologous protein [CHOP], and amyloid precursor protein [APP]) as brain damage markers were examined. The protein expressions in the brain were also measured. Gene expression levels of inflammation and oxidative stress responses were higher (p < 0.05) in brains of CP-YOUNG and CP-ADULT mice, compared with PBS-YOUNG and PBS-ADULT, and the gene expression levels were higher (p < 0.05) in brains of CP-ADULT mice than CP-YOUNG mice. Apoptosis-related (BAX1 and HMGB1) and brain disorder-related genes (C/EBPß, C/EBPδ, CHOP, and APP) were higher (p < 0.05) in brains of CP-challenged mice, compared with PBS-challenged mice. Even oxidative stress response (GPx and SOD2), cell damage-related (HMGB1), and ß-amyloid proteins were higher (p < 0.05) in brains of CP- than in PBS-challenged mice. C/EBP protein was higher (p < 0.05) in CP-YOUNG, compared with PBS-YOUNG mice. However, these clinical symptoms were not observed in small intestine and liver. These results indicate that although asymptomatic intestinal CP do not cause foodborne illness, their inhabitation may cause brain inflammation, oxidative stress, apoptosis, and cell damage, which may induce disorders, especially for the aged group.

Combined Enrichment and Quantitative Polymerase Chain Reaction to Improve Sensitivity and Reduce Time of Detection of Listeria monocytogenes in Mushrooms.

This study evaluated a combined method for the detection of Listeria monocytogenes in mushrooms, involving enrichment and quantitative real-time polymerase chain reaction (qPCR), to improve sensitivity and reduce detection time. The growth of L. monocytogenes was evaluated in Listeria enrichment broth (LEB) with modified carbon and nitrogen sources, increasing sodium concentrations, and added micronutrients. Primers targeting the L. monocytogenes iap (iap1 and iap2), hlyA (hlyA1-hlyA6), and prfA (prfA1-prfA4) genes were developed and their sensitivity and specificity were evaluated. The greatest increase in L. monocytogenes cell count was observed after 6-h incubation at 30°C in LEB+2 × FAC (LEB plus 20 mL/L ferric ammonium citrate), where cell count increased by 1.4 log CFU (colony-forming unit)/mL, compared with 0.9 log CFU/mL in LEB (p < 0.05). iap2 primers targeting the iap gene showed high specificity and were the most sensitive among those tested, with a detection limit of 2 log CFU/mL in LEB medium, 3.1 log CFU/g in golden needle mushroom, and 3.5 log CFU/g in large oyster mushroom. When applied to detection in golden needle mushrooms, a combination of 3-h incubation in LEB+2 × FAC medium and qPCR analysis with iap2 primers permitted detection of L. monocytogenes, even at an inoculum of 1 log CFU/g. Similarly, in large oyster mushrooms, 10-h enrichment in LEB+2 × FAC medium resulted in a cell count of 3.7 log CFU/g. These results indicate that a combined detection method, using LEB+2 × FAC medium for enrichment followed by qPCR with iap2 primer pair, can reduce enrichment time and improve the sensitivity and specificity of L. monocytogenes detection in mushrooms.

Hexagonal Boron Nitride Cavity Optomechanics.

Hexagonal boron nitride (hBN) is an emerging layered material that plays a key role in a variety of two-dimensional devices, and has potential applications in nanophotonics and nanomechanics. Here, we demonstrate the first cavity optomechanical system incorporating hBN. Nanomechanical resonators consisting of hBN beams with average dimensions of 12 µm × 1.2 µm × 28 nm and minimum predicted thickness of 8 nm were fabricated using electron beam induced etching and positioned in the optical near-field of silicon microdisk cavities. Of the multiple devices studied here a maximum 0.16 pm/[Formula: see text] sensitivity to the hBN nanobeam motion is demonstrated, allowing observation of thermally driven mechanical resonances with frequencies between 1 and 23 MHz, and largest mechanical quality factor of 1100 for a 23 MHz mode, at room temperature in high vacuum. In addition, the role of air damping is studied via pressure dependent measurements. Our results constitute an important step toward realizing integrated optomechanical circuits employing hBN.

Vitamin E (α-tocopherol) consumption influences gut microbiota composition.

This study evaluated if vitamin E consumption affects gut microbiota. Mice were grouped into control, low vitamin E (LV), and high vitamin E (HV). LV and HV were fed DL-α-tocopherol at 0.06 mg/20 g and 0.18 mg/20 g of body weight per day, respectively, for 34 days. Body weight of mice was measured before and after vitamin E treatment. Animals were sacrificed, liver, spleen, small intestine and large intestine collected, and weight and length were measured. Composition of gut microbiota was determined by microbiome analysis. Spleen weight index of LV was the highest. However, liver weight indices and intestinal lengths were not different. Body weights of LV group were higher than those of control. Ratio of Firmicutes to Bacteroidetes was different in LV compared to control and HV. These results indicate that low-level consumption of vitamin E increases spleen and body weight, and changes gut microbiota.

The risk of aerotolerant Campylobacter jejuni strains in poultry meat distribution and storage.

Poultry meat is a major vector for Campylobacter jejuni foodborne illness. Since C. jejuni is microaerophillic, the cell counts gradually decreased during distribution and display under aerobic condition. However, if the pathogen can resist to aerobic condition, it may cause serious problem in food safety. This study determined the aerotolerance of C. jejuni isolated from poultry and the risk of the aerotolerant C. jejuni strains. Fourteen C. jejuni strains isolated from poultry were subjected to aerobic condition in a shaking incubator at 500 rpm and 37 °C. The cell counts of C. jejuni strains were enumerated on modified CCDA-Preston at 0, 24, 72 and 120 h, and the strains, having reduction less than 2 Log CFU/mL for 120 h were determined as aerotolerant C. jejuni strain. Non-aerotolerant and aerotolerant C. jejuni strains were then incubated at 4 °C under aerobic condition to compare the growth between aerotolerant and non-aerotolerant strains. In addition, transcriptomes for virulence and stress response genes (cadF, cdtB, ciaB, clpP and htrB) were compared between non-aerotolerant and aerotolerant C. jejuni strains. Among 14 C. jejuni strains, seven strains (50%) showed less than 2-Log CFU/mL reduction at 37 °C after 24 h, and five strains of them still showed less than 2-Log CFU/mL reduction after 48 h. Especially, C. jejuni SMFM2015-Du7 and C. jejuni SMFM2014-Du16 were still survived after 120 h under aerobic condition, which were then determined as aerotolerant C. jejuni. However, at 4 °C under aerobic condition, there were no significant differences in the reduction of C. jejuni cell counts and virulence gene expressions between non-aerotolerant (C. jejuni SMFM2014-Du8) and aerotolerant strains (C. jejuni SMFM2015-Du7 and C. jejuni SMFM2014-Du16) except for stress response gene (htrB). These results indicate that there are aerotolerant C. jejuni strains, but their risk is similar to non-aerotolerant C. jejuni strains at 4 °C under aerobic condition, which is distribution and storage condition for poultry meat. Therefore, additional food safety management for the aerotolerant C. jejuni is not necessary.

Optical analysis of the refractive index and birefringence of hexagonal boron nitride from the visible to near-infrared.

Two-dimensional materials such as hexagonal boron nitride (h-BN), graphene, and transition metal dichalcogenides have drawn great attention in various fields of photonics and electronics. Among them, h-BN has recently emerged as a promising material platform to study integrated quantum photonics due to its ultrabright quantum light emission capabilities. However, the fundamental optical properties of h-BN have not yet been investigated in the visible and near-infrared (NIR) spectrum thoroughly. In this Letter, we report the refractive indices of h-BN thin films in the visible to NIR range. To the best of our knowledge, this is the first experimental observation of h-BN birefringence. Accurate parameters of refractive indices enable more precise design of h-BN-based photonic devices in the integrated photonics platforms.

Second-harmonic generation in multilayer hexagonal boron nitride flakes.

In this Letter, we report the second-harmonic generation (SHG) from thick hexagonal boron nitride (hBN) flakes with approximately 109-111 layers. The resulting effective second-order susceptibility is similar to previously reported few-layer experiments. This confirms that thick hBN flakes can serve as a platform for nonlinear optics, which is useful because thick flakes are easy to exfoliate while retaining a large size. We also show spatial second-harmonic maps revealing that SHG remains a useful tool for the characterization of the layer structure, even in the case of a large number of layers.