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A switchable and wavelength interval adjustable multi-wavelength erbium-doped fiber actively Q-switched fiber laser based on EOM and improved Lyot filter is proposed. In the experiment, stable and switchable laser outputs of single to quintuple-wavelength can be achieved by adjusting the polarization controllers and the wavelength intervals are adjustable between 2 nm, 3 nm and 6 nm. With the increase of the pump power, the number of output wavelength reaches nine. Moreover, the single-dual and dual-pulse sequences can be observed in a modulation period and the dual-pulse interval can be tuned from 14.7 to 11.1 µs. The wavelength interval of the proposed laser and the pulse interval of the dual-pulse can be adjusted more flexibly. It has a broad application prospect in the fields of optical measurement and laser imaging. [ABSTRACT FROM AUTHOR]

Land use changes have profoundly influenced global environmental dynamics. The Yellow River (YR), as the world's fifth-longest river, significantly contributes to regional social and economic growth due to its extensive drainage area, making it a key global player. To ensure ecological stability and coordinate land use demand, modeling the future land allocation patterns of the Yellow River Basin (YRB) will assist in striking a balance between land use functions and the optimization of its spatial design, particularly in water and sand management. In this research, we used a multi-objective genetic algorithm (MOGA) with the PLUS model to simulate several different futures for the YRB's land use between 1990 and 2020 and predict its spatial pattern in 2030. An analysis of the spatiotemporal evolution of land use changes in the YRB indicated that construction land expansion is the primary driver of landscape pattern and structure changes and ecological degradation, with climate change also contributing to the expansion of the watershed area. On the other hand, the multi-scenario simulation, constrained by specific targets, revealed that economic development was mainly reflected in land expansion for construction. At the same time, grassland and woodland were essential pillars to support the region's ecological health, and increasing the development of unused land emerged as a potential pathway towards sustainable development in the region. This study could be used as a template for the long-term growth of other large river basins by elucidating the impacts of human activities on land use and rationalizing land resource allocation under various policy constraints. [ABSTRACT FROM AUTHOR]

In this paper, we propose a dual-channel broadband photonic-crystal fiber polarization filter with high loss based on surface plasmon resonance. We carefully design gold-coated elliptical air hole structure to improve the confinement loss and the isolation of x-polarized and y-polarized guided modes. Multi-order plasmonic modes are excited to broad the filtering band. Moreover, in view of our simulation results, we demonstrate that plasmonic resonance occurs at the wavelength, where birefringence abnormally changes; also, complete and incomplete mode coupling are able to be distinguished by birefringence. At communication wavelengths of 1550 and 1318 nm, the calculated confinement loss of x-polarized and y-polarized core modes are 744.63 and 1089 dB/cm, with crosstalk up to – 1282.54 and 2233.46 dB, respectively. The proposed dual-channel polarization filter will be a good choice for optical fiber communication. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a tunable and switchable low-threshold multi-wavelength erbiumdoped fiber pulsed laser. It is based on a composite structure of Lyot filter and nonlinear optical loop mirror. At a threshold of 30 mW, single-wavelength and dual-wavelength states can be obtained with a tuning range of 5 nm for the single wavelength and 1 nm for the dual wavelength. By adjusting the pump power and polarization controllers, the laser can achieve at most eightuple-wavelength operation. We use the nonlinear optical loop mirror as a saturable absorber to realize stable pulse output. The pulse sequences begin to appear when the pump power is 100 mW. The pulse repetition rate corresponding to the dual-wavelength is 40.52 kHz, and the pulse width is 144 ns. Due to its abundant range of wavelengths and significant pulse phenomenon, the proposed laser is widely used in fiber sensing and other fields. [ABSTRACT FROM AUTHOR]

Cognitive decline is one of the complications of type 2 diabetes (T2D). Intermittent fasting (IF) is a promising dietary intervention for alleviating T2D symptoms, but its protective effect on diabetes-driven cognitive dysfunction remains elusive. Here, we find that a 28-day IF regimen for diabetic mice improves behavioral impairment via a microbiota-metabolites-brain axis: IF enhances mitochondrial biogenesis and energy metabolism gene expression in hippocampus, re-structures the gut microbiota, and improves microbial metabolites that are related to cognitive function. Moreover, strong connections are observed between IF affected genes, microbiota and metabolites, as assessed by integrative modelling. Removing gut microbiota with antibiotics partly abolishes the neuroprotective effects of IF. Administration of 3-indolepropionic acid, serotonin, short chain fatty acids or tauroursodeoxycholic acid shows a similar effect to IF in terms of improving cognitive function. Together, our study purports the microbiota-metabolites-brain axis as a mechanism that can enable therapeutic strategies against metabolism-implicated cognitive pathophysiologies. Intermittent fasting (IF) has been shown beneficial in reducing metabolic diseases. Here, using a multi-omics approach in a T2D mouse model, the authors report that IF alters the composition of the gut microbiota and improves metabolic phenotypes that correlate with cognitive behavior. [ABSTRACT FROM AUTHOR]