Anti-Obesity Effect and Mechanism of Chitooligosaccharides Were Revealed Based on Lipidomics in Diet-Induced Obese Mice.

Chitooligosaccharide (COS) is a natural product from the ocean, and while many studies have reported its important role in metabolic diseases, no study has systematically elaborated the anti-obesity effect and mechanism of COS. Herein, COSM (MW ≤ 3000 Da) was administered to diet-induced obese mice by oral gavage once daily for eight weeks. The results show that COSM administration reduced body weight; slowed weight gain; reduced serum Glu, insulin, NEFA, TC, TG, and LDL-C levels; increased serum HSL and HDL-C levels; improved inflammation; and reduced lipid droplet size in adipose tissue. Further lipidomic analysis of adipose tissue revealed that 31 lipid species are considered to be underlying lipid biomarkers in COS therapy. These lipids are mainly enriched in pathways involving insulin resistance, thermogenesis, cholesterol metabolism, glyceride metabolism and cyclic adenosine monophosphate (cAMP), which sheds light on the weight loss mechanism of COS. The Western blot assay demonstrated that COSM intervention can improve insulin resistance, inhibit de novo synthesis, and promote thermogenesis and ß-oxidation in mitochondria by the AMPK pathway, thereby alleviating high-fat diet-induced obesity. In short, our study can provide a more comprehensive direction for the application of COS in obesity based on molecular markers.

Connection between gut microbiome and the development of obesity.

The potential role of the gut microbiota in various human diseases has attracted considerable attention worldwide. Here, we discuss the vital role of the intestinal microbiota in the development of obesity. First, we describe how the gut microbiota promotes fat accumulation. Additionally, a high-fat diet leads to structural instability among in the gut microbiota, further leading to an increase in endotoxins, which aggravates obesity. We then discuss how gut microbiota metabolites, including short-chain fatty acids and lipopolysaccharides, affect the host. Finally, we review several strategies for regulating the intestinal flora.

Upstream dispersion management supporting 100 km differential reach in TWDM-PON.

An optical dispersion compensator (ODC) with negative dispersion value in optical line terminal (OLT) is proposed to manage the chromatic dispersion of 10 Gb/s upstream directly-modulated signals from users with 100 km differential distances, achieving a maximal 51.9 dB loss budget thanks to the positive chirp of the directly-modulated signals and the characteristics of access networks that lower loss budget is required for the users at shorter transmission distance. The optimal dispersion value of the ODC is determined by the maximal distance of the users and the objective is to guarantee the loss budget monotonically improved with the increase of reach, therefore supporting differential reach. Experimental results show that it is a potential solution for practical implementation of long-reach and high splitting-ratio time and wavelength division multiplexed passive optical network (TWDM-PON).

Higher-order defect-mode laser in an optically thick photonic crystal slab.

The use of an optically thick slab may provide versatile solutions for the realization of a current injection-type laser using photonic crystals. Here, we show that a transversely higher-order defect mode can be designed to be confined by a photonic bandgap in such a thick slab. Using simulations, we show that a high Q of >10(5) is possible from a finely tuned second-order hexapole mode (2h). Experimentally, we achieve optically pumped pulsed lasing at 1347 nm from the 2h with a peak threshold pump power of 88 µW.

Self-aligned active quantum nanostructures in photonic crystals via selective wet-chemical etching.

We propose a method of forming quantum-size emitters within a pre-defined photonic crystal in a self-aligned fashion through controlled removal of quantum well layers via selective wet-chemical etching. To demonstrate the effectiveness of our method, we take the example of a two-dimensional photonic crystal slab containing multiple quantum wells at its center. We successfully fabricate vertically stacked quantum nanostructures (or quantum dots) well aligned with respect to the photonic crystal backbone. Micro-photoluminescence measurements performed at 78 K reveal that the radiative transition energy blue-shifts when the lateral dimension reaches less than 100 nm, which is compared with a simple model based on the 'particle-in-a-box' picture. The proposed method may find a broad range of applications in photonics and quantum optics, where the coupling between an emitter and an optical mode needs to be maximized.

Photonic crystal nanocavity laser in an optically very thick slab.

A photonic crystal (PhC) nanocavity formed in an optically very thick slab can support reasonably high-Q modes for lasing. Experimentally, we demonstrate room-temperature pulsed lasing operation from the PhC dipole mode emitting at 1324 nm, which is fabricated in an InGaAsP slab with thickness (T) of 606 nm. Numerical simulation reveals that when T≥800 nm, over 90% of the laser output power couples to the PhC slab modes, suggesting a new route toward an efficient in-plane laser for photonic integrated circuits.

Design of a surface-emitting, subwavelength metal-clad disk laser in the visible spectrum.

We analyze metal-clad disk cavities designed for nanolasers in the visible red spectrum with subwavelength device size and mode volume. Metal cladding suppresses radiation loss and supports low order modes with room temperature Q of 200 to 300. Non-degenerate single-mode operation with enhanced spontaneous emission coupling factor ß is expected with the TE(011) mode that has a 0.46(λ(0)/n)(3) mode volume and Q = 210 in a device of size 0.12λ(0)(3). Threshold gain calculations show that room temperature lasing is possible using multiple GaInP/AlGaInP quantum wells as the gain medium. Placing a planar metal reflector under the cavity can enhance radiation and extraction efficiencies or increase the Q, without incurring additional metallic absorption loss. We show that the far-field radiation characteristics are strongly affected by the devices' immediate surroundings, such as changes in metal cladding thickness, even as the resonant mode profile, frequency, and Q remain the same. When the metal cladding is 1 mm thick, light radiates upward with a distinct intensity maximum at 45° when the cladding is 100 nm thick, the emitted light spreads in a near-horizontal direction.

Towards a millivolt optical modulator with nano-slot waveguides.

We describe a class of modulator design involving slot waveguides and electro-optic polymer claddings. Such geometries enable massive enhancement of index tuning when compared to more conventional geometries. We present a semi-analytic method of predicting the index tuning achievable for a given geometry and electro-optic material. Based on these studies, as well as previous experimental results, we show designs for slot waveguide modulators that, when realized in a Mach-Zehnder configuration, will allow for modulation voltages that are orders of magnitude lower than the state of the art. We also discuss experimental results for nano-slot waveguides.

Nonreciprocal light propagation in a silicon photonic circuit.

Optical communications and computing require on-chip nonreciprocal light propagation to isolate and stabilize different chip-scale optical components. We have designed and fabricated a metallic-silicon waveguide system in which the optical potential is modulated along the length of the waveguide such that nonreciprocal light propagation is obtained on a silicon photonic chip. Nonreciprocal light transport and one-way photonic mode conversion are demonstrated at the wavelength of 1.55 micrometers in both simulations and experiments. Our system is compatible with conventional complementary metal-oxide-semiconductor processing, providing a way to chip-scale optical isolators for optical communications and computing.