SMEK1 ablation promotes glucose uptake and improves obesity-related metabolic dysfunction via AMPK signaling pathway.

Obesity has become a major risk of global public health. SMEK1 is also known as a regulatory subunit of protein phosphatase 4 (PP4). Both PP4 and SMEK1 have been clarified in many metabolic functions, including the regulation of hepatic gluconeogenesis and glucose transporter gene expression in yeast. Whether SMEK1 participates in obesity and the broader metabolic role in mammals is unknown. Thus, we investigated the function of SMEK1 in white adipose tissue and glucose uptake. GWAS/GEPIA/GEO database was used to analyze the correlation between SMEK1 and metabolic phenotypes/lipid metabolism-related genes/obesity. Smek1 KO mice were generated to identify the role of SMEK1 in obesity and glucose homeostasis. Cell culture and differentiation of stromal-vascular fractions (SVFs) and 3T3-L1 were used to determine the mechanism. 2-NBDG was used to measure the glucose uptake. Compound C was used to confirm the role of AMPK. We elucidated that SMEK1 was correlated with obesity and adipogenesis. Smek1 deletion enhanced adipogenesis in both SVFs and 3T3-L1. Smek1 KO protected mice from obesity and had protective effects on metabolic disorders, including insulin resistance and inflammation. Smek1 KO mice had lower levels of fasting serum glucose. We found that SMEK1 ablation promoted glucose uptake by increasing p-AMPKα(T172) and the transcription of Glut4 when the effect on AMPK-regulated glucose uptake was due to the PP4 catalytic subunits (PPP4C). Our findings reveal a novel role of SMEK1 in obesity and glucose homeostasis, providing a potential new therapeutic target for obesity and metabolic dysfunction.NEW & NOTEWORTHY Our study clarified the relationship between SMEK1 and obesity for the first time and validated the conclusion in multiple ways by combining available data from public databases, human samples, and animal models. In addition, we clarified the role of SMEK1 in glucose uptake, providing an in-depth interpretation for the study of its function in glucose metabolism.

Interferometric fiber-optic gyroscope based on mode-division multiplexing.

The interferometric fiber-optic gyroscope (IFOG) is widely used in the fields of inertial navigation and rotational seismology. A direct way to improve the sensitivity of the IFOG is to increase the length of the sensing fiber, but this increases the cost and size of the gyroscope. Here, we propose an IFOG based on mode-division multiplexing (MDM), which exhibits relatively high performance. The experimental results show that, the proposed IFOG is improved to twice as much in terms of sensitivity, angle random walk, and bias instability with the use of MDM. This research provides a novel, to the best of our knowledge, solution for the design and implementation of low-cost, high-sensitivity IFOGs, which could contribute to their application in a wider range of fields.

Dual-polarization interferometric fiber optic gyroscope based on a four-port circulator.

The dual-polarization interferometric fiber optic gyroscope (IFOG) has been studied for many years and achieved remarkable performance. In this study, we propose a novel dual-polarization IFOG configuration based on a four-port circulator, in which the polarization coupling errors and the excess relative intensity noise are well handled meanwhile. Experimental measurements of the short-term sensitivity and long-term drift using a fiber coil with a length of 2 km and a diameter of 14 cm show that the angle random walk of 5.0×10-5∘/h and bias instability of 9.0 × 10-5 °/h are achieved. Moreover, the root power spectrum density of 20n r a d/s/H z is almost flat from 0.001 Hz to 30 Hz. We believe this dual-polarization IFOG is a preferred candidate for the reference-grade performance IFOG.

Compensation of scale factor nonlinear error introduced by harmonic distortion for open-loop fiber optic gyroscopes.

The scale factor (SF) of a gyroscope is the ratio of the detection output rotational rate and the input, and is expected to be a constant. However, for open-loop interferometric fiber optic gyroscopes (IFOGs) with sinusoidal modulation, harmonic amplitudes are inevitably affected by detection defects, such as nonuniform frequency response of the photodetector or unequal gain of amplification circuits. As a result, harmonic distortion leads to SF nonlinearity, which seriously hinders the accuracy of high-precision gyroscopes. In this Letter, the theoretical form of the SF error introduced by harmonic distortion of open-loop gyroscopes is analyzed, and an effective and simple compensation method is proposed. Instead of traversing the whole dynamic range, the proposed method simplifies the calibration pretest, where only a section of the dynamic range needs to be tested. Experimental results on an open-loop IFOG prototype show that, with our proposed method, the SF nonlinear error is suppressed to 2.5 ppm within the range -300 to +300∘/s, which is 33 times less than that before compensation.

Angular accelerometer based on a dual-polarization fiber-optic Sagnac interferometer.

High-performance angular accelerometers are essential for precise dynamics control of aircraft, satellites, etc. Here, we propose, for the first time to the best of our knowledge, an angular accelerometer based on a dual-polarization fiber-optic Sagnac interferometer, which exhibits relatively high sensitivity and a broad bandwidth. The experimental results show that the angular accelerometer achieves a flat frequency response in the bandwidth range of 0.01-100 Hz. The sensitivity reaches 6.6 × 10-8 rad/s2/Hz. In addition, the proposed fiber-optic angular accelerometer does not rely on any mechanical structure and has strong environmental adaptability. This research provides a feasible solution for the design and implementation of new high-performance angular accelerometers, which contributes to their development in the fields of inertial navigation and rotational seismology.

Parameter estimation for nonlinear sandwich system using instantaneous performance principle.

The vast majority of reports mainly focus on the steady-state performance of parameter estimation. Few findings are reported for the instantaneous performance of parameter estimation because the instantaneous performance is difficult to quantify by using the design algorithm, for example, in the initial stage of parameter estimation, the error of parameter estimation varies in a specific region on the basis of the user's request. With that in mind, we design an identification algorithm to address the transient performance of the parameter estimations. In this study, the parameter estimation of nonlinear sandwich system is studied by using the predefined constraint technology and high-effective filter. To achieve the above purpose, the estimation error information reflecting the transient performance of parameter estimation is procured using the developed some intermediate variables. Then, a predefined constraint function is used to prescribe the error convergence boundary, in which the convergence rate is lifted. An error equivalent conversion technique is then employed to obtain the transformed error data for establishing an parameter adaptive update law, in which the estimation error convergence and the predefined domain can be achieved. In comparison with the available estimation schemes, the good instantaneous performance is obtained on the basis of the numerical example and practical process results.

New Insights into the Cellular Toxicity of Carbon Quantum Dots to Escherichia coli.

In this study, the cytotoxicity and toxic mechanism of carbon quantum dots (CQDs) to E. coli were evaluated in vitro. The synthetic CQDs were extremely small in size (~2.08 nm) and displayed strong fluorescence. The results demonstrated that CQDs showed good biocompatibility with E. coli within a short culture time. However, when the exposure time exceeded 24 h, the toxicity of CQDs became apparent, and the contents of reactive oxygen species, lactate dehydrogenase, and the crystal violet absorption rate increased significantly. To further explore the cytotoxic mechanism, approaches including confocal laser scanning microscopy, scanning electron microscopy, and biological transmission electron microscopy combined with zeta potential tests, osmotic pressure measurement, and comet assays were performed. On the one hand, the CQDs altered the surface charges of cells and induced lipid peroxidation by adhesion on the surface of E. coli, leading to an increase in the permeability of the cell wall. On the other hand, when the concentration of CQDs reached 200 µg/mL, the osmotic pressure of the extracellular environment was significantly reduced. These are the main factors that lead to cell edema and death. Finally, the comet assays confirmed that CQDs could induce DNA damage, which could inhibit the proliferation of E. coli.

Study of the Surfactant Transport Law Based on an Improved Adsorption Model with an Artificial Seismic Wave.

To explore the law and mechanism of enhanced surfactant flooding with a low-frequency artificial seismic wave, for single-phase fluids in porous media, a heterogeneous two-stage adsorption model for a surfactant with a low-frequency artificial seismic wave is introduced into the surfactant transport equation of a single-phase fluid. With this model, the surfactant fluid transport model in porous media with an artificial seismic wave is obtained. The model is solved using the C-N difference and chasing method. The migration law of the surfactant is simulated and quantitatively analyzed for different vibration accelerations, injection slug sizes, displacement speeds, and reservoir parameters with the action of low-frequency artificial seismic waves. The results show that artificial seismic waves can increase the effective range of the surfactants and reduce the number of chemical agents through reduced adsorption. Low-frequency vibration with the same surfactant injection rate can increase the effective range by a factor greater than one. For the same effective action distance, the dose of chemical agents can be reduced by more than 60%, and the optimal acceleration and the injection slug size are 0.3 m/s2 and 0.4 PV, respectively. With the increase of the injection rate, the effect of low-frequency vibration on the diffusion and transport of the surfactant decreases. A low-frequency wave combined surfactant has a better effect on the low permeability reservoirs. The research results provide important support for further understanding of the low-frequency artificial seismic wave composite surfactant flooding law and the optimization of the field parameters.

The Development of a New IFOG-Based 3C Rotational Seismometer.

For many years, seismological research mainly focuses on translational ground motions due to the lack of appropriate sensors. However, because of the development of devices based on Sagnac effect, measuring rotational waves directly comes available. In this work, a portable three-component broadband rotational seismometer named RotSensor3C based on open loop interferometric fiber optic gyroscope (IFOG) is designed and demonstrated. Laboratory tests and results are illustrated in detail. The self-noise ranging from 0.005 Hz to 125 Hz is about 1.2×10-7rads-1/Hz, and with the harmonics compensation the scale factor variation over ±250∘/s is lower than 10 ppm (parts per million). The misalignment matrix method is adopted to revise the output rotation rate. In a special near field experiment using the explosive source, the back-azimuths and phase velocity are estimated by the recorded acceleration and rotation rate. All the results prove the practicability of this new rotational sensor.

Cytotoxic Effect of Graphene Oxide Nanoribbons on Escherichia coli.

The biological and environmental toxicity of graphene and graphene derivatives have attracted great research interest due to their increasing applications. However, the cytotoxic mechanism is poorly understood. Here, we investigated the cytotoxic effect of graphene oxide nanoribbons (GORs) on Escherichia coli (E. coli) in an in vitro method. The fabricated GORs formed long ribbons, 200 nm wide. Based on the results of the MTT assay and plate-culture experiments, GORs significantly inhibited the growth and reproduction of E. coli in a concentration-dependent manner. We found that GORs stimulated E. coli to secrete reactive oxygen species, which then oxidized and damaged the bacterial cell membrane. Moreover, interaction between GORs and E. coli cytomembrane resulted in polysaccharide adsorption by GORs and the release of lactic dehydrogenase. Furthermore, GORs effectively depleted the metal ions as nutrients in the culture medium by adsorption. Notably, mechanical cutting by GORs was not obvious, which is quite different from the case of graphene oxide sheets to E. coli.

Sensitivity enhancement through RIN suppression in dual-polarization fiber optic gyroscopes for rotational seismology.

Portable sensors with a sufficiently high sensitivity in detecting small rotational motions have attracted significant attention in the field of rotational seismology. In this study, we propose and demonstrate a dual-polarization fiber optic gyroscope (IFOG) with a portable-sized fiber coil. Excess relative intensity noise (RIN) is effectively compensated for owing to the opposite parities and strong correlation of the two orthogonal polarized light, whereas other noises including coherent phase noise and thermal phase noise have also been handled well. In a test on detecting the rotation rate of the Earth, an enhanced sensitivity of 20nrad/s/Hz over a frequency range of 0.01 Hz to 30 Hz was demonstrated using the proposed design with an enclosed area of only 68 m2.

Effect of Acupuncture on Muscle Endurance in the Female Shoulder Joint: A Pilot Study.

Shoulder joint dysfunction is the leading cause of decreased athletic ability in athletes. Shoulder joint sports injuries affect the athletic performance of athletes. Improvements in the muscle endurance of the shoulder joint can reduce the incidence of shoulder joint dysfunction. Acupuncture has been an important part of Asian culture for a long time. In acupuncture, nerves are stimulated, inducing postactivation potentiation (PAP) in the body's motor units and enhancing muscle strength. In this research, 20 female participants with full flexion/extension and adduction/abduction ranges of motion in the shoulder joint during isokinetic exercises underwent stimulation of the following acupuncture points in the shoulder joint: Binao (LI14), Jianyu (LI15), Jianliao (SJ14), Naohui (SJ13), Yuzhong (KI26), Zhongfu (LU1), Yunmen (LU2), Xiabai (LU4), Chize (LU5), Tianfu (LU3), and Xiaoluo (SJ12). In the study, there were significant increases after acupuncture in the average maximum torque in flexion, extension, and adduction; the average work in flexion/extension and adduction/abduction; the average power in flexion/extension and adduction/abduction; the total work in flexion/extension and adduction/abduction; the total net sagittal-plane work (flexion + extension); and the total net frontal-plane work (adduction + abduction) (P < 0.05). The average maximum abduction torque did not increase significantly, potentially due to antagonistic forces of muscles. Therefore, acupuncture at acupoints around the shoulder joint can increase muscle excitability, thereby delaying muscle fatigue and increasing muscle endurance.

Weakly-coupled 7-core-2-LP-mode transmission using commercial SFP + transceivers enabled by all-fiber spatial multiplexer and demultiplexer.

Spatial division multiplexing transmission over few-mode multicore fiber (FM-MCF) recently attracts great interests by simultaneously exploiting two more dimensions than conventional single mode fibers. In this paper, we propose an all-fiber spatial multiplexer (MUX) by cascading mode-selective fiber couplers (MSCs) with a fiber-bundle-type fan-in device, and spatial demultiplexer (DEMUX) by cascading a fiber-bundle-type fan-out device with degenerate-mode-selective fiber couplers and MSCs. Thanks to the low crosstalk of the FM-MCF, spatial MUX/DEMUX and their coupling, weakly-coupled 7-core-2-LP-mode real-time transmission over 1-km of FM-MCF is successfully demonstrated using 10-Gbps commercial enhanced small form-factor pluggable (SFP + ) transceivers.

Thermal phase noise in giant interferometric fiber optic gyroscopes.

The thermal phase noise in giant interferometric fiber optic gyroscopes (fiber length L > 10 km) and its impact on the detection sensitivity are theoretically derived and experimentally verified. It is confirmed that thermal phase noise cannot be overlooked for the giant IFOGs. Utilizing high order eigen frequency modulation can effectively suppress the walk-off component of thermal phase noise, but the residual part contributes to high-frequency range thus limits the detection bandwidth of giant IFOGs. The self-noise is experimentally demonstrated as 3.5 nrad/s/Hz at low frequencies and 5.2 nrad/s/Hz at 100 Hz in the IFOG with a 30-km single mode fiber coil. Discussions about the fiber characteristics on thermal phase noise are presented, which paves the way to the design of giant IFOGs.

Weakly-coupled 4-mode step-index FMF and demonstration of IM/DD MDM transmission.

Weakly coupled-mode division multiplexing (MDM) over few-mode fibers (FMF) for short-reach transmission has attracted great interest, which can avoid multiple-input-multiple-output digital signal processing (MIMO-DSP) by greatly suppressing modal crosstalk. In this paper, step-index FMF supporting 4 linearity polarization (LP) modes for MIMO-free transmission is designed and fabricated for the first time, to our knowledge. Modal crosstalk of the fiber is suppressed by increasing the mode effective refractive index differences. The same fabrication method as standard single-mode fiber is adopted so that it is practical and cost-effective. The mode multiplexer/demultiplexer (MUX/DEMUX) consists of cascaded mode-selective couplers (MSCs), which are designed and fabricated by tapering the proposed FMF with single-mode fiber (SMF). The mode MUX and DEMUX achieve very low modal crosstalk not only for the multiplexing/demultiplexing but also for the coupling to/from the FMF. Based on the fabricated FMF and mode MUX/DEMUX, we successfully demonstrate the first simultaneous 4-modes (LP01, LP11, LP21 & LP31) 10-km FMF transmission with 10-Gb/s intensity modulation and MIMO-free direct detection (IM/DD). The modal crosstalk of the whole transmission link is successfully suppressed to less than -16.5 dB. The experimental results indicate that FMF with simple step-index structure supporting 4 weakly-coupled modes is feasible.

Effective suppression of residual coherent phase error in a dual-polarization fiber optic gyroscope.

The impact of residual coherent phase error in a dual-polarization interferometric fiber optic gyroscope (IFOG) is investigated. Although it has been intuitively assumed that the coherence of a light source can be eliminated by a sufficient long fiber delay, the experiment and theory indicate that it still contributes a remarkable portion to long-term instability. After the residual coherent phase error is well handled, we demonstrate a dual-polarization IFOG with bias instability of 3.56×10-4°/h. Comparisons show that such performance is even better than the conventional "minimal scheme" that operates on one polarization.

Suppressing polarization non-reciprocity error with reverse phase modulation in dual-polarization fiber optic gyroscopes.

In a dual-polarization interferometric fiber optic gyroscope (IFOG), polarization non-reciprocity (PN) errors are significant, which degrades the IFOG performance due to the polarization coupling between two orthogonal axes. A dual-polarization IFOG with reverse phase modulation is proposed in which PN phase error can be sufficiently suppressed. In our scheme using a 2-km polarization maintaining coil with open-loop configuration, angle random walk of 4.62×10-4°/h and a bias instability of 4.6 × 10-4 °/h is demonstrated in detecting the Earth's rotation rate.

Compensation of thermal strain induced polarization nonreciprocity in dual-polarization fiber optic gyroscope.

Dual-polarization interferometric fiber optic gyroscope (IFOG) is a novel scheme in which the polarization nonreciprocal (PN) phase error of the two orthogonal polarizations can be optically compensated. In this work, we investigate the effective of PN phase error compensation under varying temperature. It is proved that, the thermally induced strain deforms the fiber, and results in perturbations on the birefringence and polarization cross coupling which degrades the IFOG's stability. A wave propagation model and analytical expressions of PN phase error are derived by using coupled-wave equation and Jones matrix. We theoretically and experimentally verify that, although the single-mode (SM) and polarization-maintaining (PM) fiber coils behave different owing to their intrinsic properties of wave propagation, the thermal strain induced PN phase error can still be compensated under slow and adiabatic temperature variations. This could be a promising feature to overcome the temperature fragility of IFOG.

Analytical and statistical investigation on structural fluctuations induced radiation in photonic crystal slabs.

We extend the coupled-wave-theory (CWT) framework to a supercell lattice photonic crystal (PC) structure to model the radiation of high-Q resonances under structural fluctuations since they are inevitable in realistic devices. The comparison of CWT results and the finite-element-method (FEM) simulations confirm the validity of CWT. It is proved that the supercell model approaches a realistic finite-size PC device when the supercell size is large enough. The Q factors within fluctuated structures are constraint owing to the appearance of fractional orders of radiative waves, which are induced by structural fluctuations. For a large enough footprint size, the upper bound of the Q factor is determined by the fabrication precision, and further increasing the device size will no longer benefit the Q factor.

Demonstration of all-optical MDM/WDM switching for short-reach networks.

Mode division multiplexing (MDM) has been widely investigated in optical transmission systems and networks to improve network capacity. However, the MDM receiver is always expensive and complex because coherent detection and multiplex-input-and-multiplex-output (MIMO) digital signal processing (DSP) are required to demultiplex each spatial mode. In this paper, we investigate the application of MDM in short-reach scenarios such as datacenter networking. Two-dimensional MDM and wavelength division multiplexing node structure based on low modal-crosstalk few-mode fiber (FMF) and components is proposed, in which signal in each mode or wavelength can be independently switched. We experimentally demonstrate independent adding, dropping and switching functionalities with two linearly polarized modes and four wavelength channels over a total 11.8-km 2-mode low modal-crosstalk FMFs. The structure is simple without coherent detection or MIMO DSP. Only slight penalties of receiver sensitivity are observed for all switching operations. The influence of modal-crosstalk accumulation for cascaded switching nodes is also investigated.