Suppression of damping in a diamagnetically levitated dielectric sphere via eddy currents and static charge reduction.

Diamagnetically levitated micro-nano oscillators play a crucial role in fundamental physics research and the advancement of high-precision sensors. Achieving high sensitivity in acceleration or force sensing is a fundamental requirement within these research domains. The primary limitation in achieving such sensitivity is thermal noise, which is directly proportional to the motion damping of the oscillator. Theoretical modeling suggests the presence of significant damping mechanisms induced by eddy currents. In this study, we validated the theoretical model by optimizing the structure of the magnet trap, confirming the impact of eddy currents on the damping of the oscillators. Additionally, we observed another type of damping caused by static charge in moving levitated dielectrics. Subsequently, we proposed an innovative theoretical model to explain this phenomenon and verified its validity during the charge neutralization process. Through these efforts, we successfully reduced the total damping from 1.6 mHz to 0.15 mHz, resulting in an order of magnitude improvement in performance. Our sensing system achieved the highest sensitivity of acceleration sensing in diamagnetically levitated submillimeter-scale dielectric to date, measuring 7.6±0.8)×10-10g/Hz. The exploration conducted in this study regarding the analysis and suppression of electromagnetic damping, along with associated thermal noise, holds significant promise for frontier research involving sensing with levitating dielectrics.

Theoretical Analysis and Experimental Verification of the Influence of Polarization on Counter-Propagating Optical Tweezers.

Counter-propagating optical tweezers are experimental platforms for the frontier exploration of science and precision measurement. The polarization of the trapping beams significantly affects the trapping status. Using the T-matrix method, we numerically analyzed the optical force distribution and the resonant frequency of counter-propagating optical tweezers in different polarizations. We also verified the theoretical result by comparing it with the experimentally observed resonant frequency. Our analysis shows that polarization has little influence on the radial axis motion, while the axial axis force distribution and the resonant frequency are sensitive to polarization change. Our work can be used in designing harmonic oscillators which can change their stiffness conveniently, and monitoring polarization in counter-propagating optical tweezers.

Analysis and Suppression of Laser Intensity Fluctuation in a Dual-Beam Optical Levitation System.

Levitated micro-resonators in vacuums have attracted widespread attention due to their application potential in precision force sensing, acceleration sensing, mass measurement and gravitational wave sensing. The optically levitated microsphere in a counter-propagating dual-beam optical trap has been of particular interest because of its large measurement range and flexible manipulation. In this system, laser intensity fluctuation directly influences the trap stability and measurement sensitivity, which makes it a crucial factor in improving trapping performance. In this paper, a time-varying optical force (TVOF) model is established to characterize the influence of laser intensity fluctuation in a dual-beam optical trap. The model describes the relationship between the laser intensity fluctuation, optical force and the dynamic motion of the micro-sized sphere. In addition, an external laser intensity control method is proposed, which achieved a 16.9 dB laser power stability control at the relaxation oscillation frequency. The long-term laser intensity fluctuation was suppressed from 3% to 0.4% in a one-hour period. Experiments showed that the particle's position detection sensitivity and the stability of the relaxation oscillation could be improved by laser intensity fluctuation suppression.

Revolution of a trapped particle in counter-propagating dual-beam optical tweezers under low pressure.

We presented faster and more accurate simulations and experiments describing the revolution of a suspended particle in optical tweezers under a low pressure. Instead of the state-of-the-art offline method of pinhole alignment, we proposed an in situ method of revolution suppression by adjusting the laser beam while observing the power spectral density and time-domain plot of the particle centroid displacement. The experimental results under different air pressures show that our method is more effective at low pressures. We observed that "revolution occurs when radial alignment error is below the threshold" and uncovered the mechanism behind this phenomenon. The rapidly growing Q value of the revolution indicates a high-precision resonance measurement method under lower air pressure compared with random translation measurements.

Fabrication of Biomolecule-Loaded Composite Scaffolds Carried by Extracellular Matrix Hydrogel.

Fabrication of multifunctional scaffolds with biomimicking physical and biological signals play an important role in enhancing tissue regeneration. Multifunctional features come from the composite scaffold with various bioactive molecules. However, simple, biocompatible, and controllable hybridization strategy is still lacking. In this study, we leverage naturally derived extracellular matrix (ECM) as chemically controllable hydrogel carrier to effectively load functional biomolecules. The use of ECM hydrogel takes advantage of both native functionality of ECM components and tunability of hydrogel in controlling release of loaded molecules. As a proof of concept, porous acellular bone scaffold was selected as the solid pristine scaffold to be composited with BMP-2 and VEGF, which are loaded by spinal cord-derived ECM (SC-ECM) hydrogel. Crosslinking degree of SC-ECM hydrogel is tuned by changing genipin concentration, which renders the control over release kinetics of BMP-2 and VEGF. The mechanical strength of scaffold maintained after hybridization and is not significantly decreased in wet condition. In vitro evaluations of scaffolds cocultured with osteoblasts and mesenchymal stem cells (MSCs) demonstrate the biocompatible and bioactive features resulting from the composite scaffolds. Evidenced by alkaline phosphatase test, immunofluorescence, and real-time polymerase chain reaction, differentiation of MSCs towards osteoblast lineage is significantly enhanced by composite scaffolds. Therefore, our strategy in fabricating composite scaffold enabled by biomolecule-loaded ECM hydrogel holds great promise in regenerating diverse tissue types by appropriate combinations of solid pristine scaffolds, ECM, and bioactive molecules. Impact statement We developed a bioactive molecule (e.g., growth factor, protein) loading method using extracellular matrix hydrogel as a carrier. It brings a new strategy to fabricate composite scaffolds with unique biofunctions.

Displacement Detection Decoupling in Counter-Propagating Dual-Beams Optical Tweezers with Large-Sized Particle.

As a kind of ultra-sensitive acceleration sensing platform, optical tweezers show a minimum measurable value inversely proportional to the square of the diameter of the levitated spherical particle. However, with increasing diameter, the coupling of the displacement measurement between the axes becomes noticeable. This paper analyzes the source of coupling in a forward-scattering far-field detection regime and proposes a novel method of suppression. We theoretically and experimentally demonstrated that when three variable irises are added into the detection optics without changing other parts of optical structures, the decoupling of triaxial displacement signals mixed with each other show significant improvement. A coupling detection ratio reduction of 49.1 dB and 22.9 dB was realized in radial and axial directions, respectively, which is principally in accord with the simulations. This low-cost and robust approach makes it possible to accurately measure three-dimensional mechanical quantities simultaneously and may be helpful to actively cool the particle motion in optical tweezers even to the quantum ground state in the future.

Gelatin Methacryloyl Microneedle Patches for Minimally Invasive Extraction of Skin Interstitial Fluid.

The extraction of interstitial fluid (ISF) from skin using microneedles (MNs) has attracted growing interest in recent years due to its potential for minimally invasive diagnostics and biosensors. ISF collection by absorption into a hydrogel MN patch is a promising way that requires the materials to have outstanding swelling ability. Here, a gelatin methacryloyl (GelMA) patch is developed with an 11 × 11 array of MNs for minimally invasive sampling of ISF. The properties of the patch can be tuned by altering the concentration of the GelMA prepolymer and the crosslinking time; patches are created with swelling ratios between 293% and 423% and compressive moduli between 3.34 MPa and 7.23 MPa. The optimized GelMA MN patch demonstrates efficient extraction of ISF. Furthermore, it efficiently and quantitatively detects glucose and vancomycin in ISF in an in vivo study. This minimally invasive approach of extracting ISF with a GelMA MN patch has the potential to complement blood sampling for the monitoring of target molecules from patients.

Eigen frequency measurements of a fiber optic gyroscope based on a staircase waveform with large temperature range.

The eigen frequency is a key parameter of a fiber optic gyroscope (FOG). We present an online eigen frequency tracking method for FOG technology based on the staircase waveform and a four-step frequency perturbation. Results show that the measurement accuracy of the eigen frequency does not exceed 1.7 Hz for a temperature range of 27.5°C-62.5°C and a variation rate of 0.24°C/min. This is in good agreement with the theoretical model. The method, which exhibits a low time-space complexity, simply requires the addition of a low-rate digital-to-analog converter to the existing gyro system. There is no requirement for the type of staircase waveform in the phase modulation, and the staircase waveform remains unchanged. Thus, this method can be easily transplanted into other algorithms.

Tissue Transglutaminase-Regulated Transformed Growth Factor-ß1 in the Parasite Links Schistosoma japonicum Infection with Liver Fibrosis.

Transforming growth factor (TGF-ß1) is among the strongest factors of liver fibrogenesis, but its association with Schistosoma-caused liver fibrosis is controversial. Tissue transglutaminase (tTG) is the principal enzyme controlling TGF-ß1 maturation and contributes to Sj-infected liver fibrosis. Here we aim to explore the consistency between tTG and TGF-ß1 and TGF-ß1 source and its correlation with liver fibrosis after Sj-infection. TGF-ß1 was upregulated at weeks 6 and 8 upon liver fibrosis induction. During tTG inhibition, TGF-ß1 level decreased in sera and liver of infected mice. TGF-ß1 showed positive staining in liver containing Sj adult worms and eggs. TGF-ß1 was also detected in Sj adult worm sections, soluble egg antigen and Sj adult worm antigen, and adult worms' culture medium. The TGF-ß1 mature peptide cDNA sequence and its extended sequence were amplified through RT-PCR and RACE-PCR using adult worms as template, and sequence is analyzed and loaded to NCBI GenBank (number GQ338152.1). TGF-ß1 transcript in Sj eggs was higher than in adult worms. In Sj-infected liver, transcriptional level of TGF-ß1 from Sj, but not mouse liver, correlated with liver fibrosis extent. This study provides evidence that tTG regulates TGF-ß1 and illustrates the importance of targeting tTG in treating Sj infection-induced fibrosis.

Involvement of IL-13 and tissue transglutaminase in liver granuloma and fibrosis after schistosoma japonicum infection.

Schistosomiasis, one of the most devastating parasitic diseases, is caused by Schistosoma japonicum (Sj) infection resulting in serious liver fibrosis. Interleukin- (IL-) 13, which is produced by TH2 cells, is a critical profibrotic cytokine found in various organs, including the liver. Tissue transglutaminase (tTG), a group of multifunctional enzymes, serves a central function in the pathogenesis of chronic liver diseases. However, the relationship between IL-13, tTG, and liver fibrosis during Schistosoma infection has not been established. This study investigated the involvement of IL-13 and tTG in liver fibrogenesis during Sj infection in mice. Five weeks after Sj infection, granuloma and fibrosis development in the liver coincided with an increase in IL-13 and tTG in the liver and the upregulation of serum IL-13 in infected mice. Administration of cystamine, an inhibitor of tTG, abrogated the increase in both tTG and IL-13 in infected mice and ameliorated liver fibrogenesis and granuloma development. This result establishes a novel link among IL-13, tTG, and liver granuloma and fibrosis under Sj infection. Based on their important functions in liver fibrosis induced by Sj infection, IL-13 and tTG could be promising potential drug targets against schistosomiasis.

[Expression of Toll-like receptors 2 and 6 in mice liver during Schistosoma japonicum infection].

OBJECTIVE: To investigate the expression of hepatic Toll-like receptor 1 (TLR1), TLR2 and TLR6 on mice with Schistosoma japonicum infection. METHODS: Fifty BALB/c mice were infected with 20 +/- 3 S. japonicum cercariae through abdominal skin. At 6 weeks post-infection, the mice (n = 10) in treatment group were administered intragastrically with praziquantel [250 microg/(g x d)] for 3 d. The livers of mice (n = 10) were collected at pre-infection and 5, 6, 8 and 12 weeks post-infection, and then the mRNA expression levels of hepatic TLR1, TLR2, TLR6 gene were detected with reverse transfer PCR. Hepatic TLR2, TLR6 protein levels were detected by immunohistochemical staining. RESULTS: The mRNA levels of TLR1, TLR2, and TLR6 on 5, 6, 8 and 12 weeks post infection were significantly higher than that of uninfected mice. After praziquantel treatment, the mRNA level of TLR2 and TLR6 in murine liver of treatment group was lower than that of infection group, but the level of TLR1 mRNA had no obvious change. Furthermore, immunohistochemistry results revealed that the expression of TLR2 and TLR6 proteins in murine liver was up-regulated at 5, 6, 8 and 12 weeks post-infection. After praziquantel treatment, the percentage of TLR2 positive area in liver of infected mice without and with praziquantel treatment were (44.2 +/- 4.3)%, (8.8 +/- 3.1)%, respectively, and TLR2 protein level was considerably down-regulated (P < 0.01). The percentage of TLR6 positive area in liver of infected mice without and with praziquantel treatment was (48.4 +/- 5.4)%, (37.4 +/- 3.5)%, respectively, and TLR6 level decreased slightly (P < 0.05). CONCLUSION: The expression level of TRL2 and TLR6 in murine liver increases after Schistosoma japonicum infection. While compared with TLR2, the role of TLR6 in this progress is a weaker one.

Permissibility of Mongolian gerbil for Angiostrongylus cantonensis infection and utility of this animal model for anthelmintic studies.

The Mongolian gerbil (Meriones unguiculatus) has been indicated to be a useful experimental model host for studying nematode. To understand the possibility of the Mongolian gerbil as an animal model of Angiostrongylus cantonensis infection, we investigated the development, migration, and tissue distribution of A. cantonensis and pathological changes in the brain and lungs of the infected Mongolian gerbils. The first stage larvae of A. cantonensis in the stool of the infected gerbils were examined by direct smear method at 45th day postinfection (PI). In addition, a group of the infected gerbils were orally fed with albendazole (100 mg/kg/day/gerbil) at the 8th day PI and continued for 3 consecutive days. The results showed that mortality rate of Mongolian gerbils infected with 10 third stage larvae of A. cantonensis was about 62% at the 30th day PI; the peak period of death was from the 23rd to 30th day PI. About 93% (27/29) of the worms in survivors of infected gerbils could develop to complete sexual maturity at the 46th day PI, and the examinations of 12 gerbils in G3 group revealed that first stage larvae of A. cantonensis could be found in the feces of 4 gerbils at the 45th day PI. About 80% of the worms were in the brain of infected gerbils and 20% in the lungs from the 23rd to 25th day PI; during migration of the worms from the brain to lungs, more than 90% of the worms arrived to the lungs and less than 10% of them still stayed in the brain during from the 45th to 46th day PI. Pathological examination revealed that injuries induced by A. cantonensis in infected gerbils were characterized by eosinophilic meningitis and granulomatous pneumonia. Otherwise, albendazole exhibited a good larvicidal activity in the infected Mongolian gerbils. In contrast with infected control group, no gerbils died in administering albendazole, no worms were recovered, and no nervous system symptoms caused by the infection occurred at the 26th day PI. These findings clearly indicated that Mongolian gerbils should be a potential incomplete permissive host for A. cantonensis and are very susceptive to A. cantonensis infection. Moreover, it has been certified that gerbils as an experimental animal can be used in screening of drug against A. cantonensis. The study provides us a new, selectable experimental animal model for research of A. cantonensis.