Background and purpose
Previous studies suggested that the overall burden of prior infections contributes to cardiovascular diseases and stroke. In the present study, the association between ...infectious burden (IB) and Alzheimer's disease (AD) was examined.
Methods
Antibody titers to common infectious pathogens including cytomegalovirus (CMV), herpes simplex virus type 1 (HSV‐1), Borrelia burgdorferi, Chlamydophila pneumoniae and Helicobacter pylori were measured by enzyme‐linked immunosorbent assay in 128 AD patients and 135 healthy controls. IB was defined as a composite serological measure of exposure to these common pathogens.
Results
Seropositivities toward zero−two, three and four−five of these pathogens were found in 44%, 40% and 16% of healthy controls but in 20%, 44% and 36% of AD patients, respectively. IB, bacterial burden and viral burden were independently associated with AD after adjusting for age, gender, education, APOE genotype and various comorbidities. Mini‐Mental State Examination scores were negatively correlated with IB in all cases. Serum beta‐amyloid protein (Aβ) levels (i.e. Aβ40, Aβ42 and total Aβ) and inflammatory cytokines (i.e. interferon‐γ, tumor necrosis factor α, interleukin‐1β and interleukin‐6) in individuals exposed to four−five infectious pathogens were significantly higher than those exposed to zero−two or three pathogens.
Conclusions
IB consisting of CMV, HSV‐1, B. burgdorferi, C. pneumoniae and H. pylori is associated with AD. This study supports the role of infection/inflammation in the etiopathogenesis of AD.
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Osteoarthritis (OA) is a complicated degenerative disease that affects whole joint tissue. Currently, apart from surgical approaches to treat late stage OA, effective treatments to reverse OA are not ...available. Thus, the mechanisms leading to OA, and more effective approaches to treat OA should be investigated. According to available evidence, the PI3K/AKT/mTOR signaling pathway is essential for normal metabolism of joint tissues, but is also involved in development of OA. To provide a wide viewpoint to roles of PI3K/AKT/mTOR signaling pathway in osteoarthritis, a comprehensive literature search was performed using PubMed terms ‘PI3K OR AKT OR mTOR’ and ‘osteoarthritis’. This review highlights the role of PI3K/AKT/mTOR signaling in cartilage degradation, subchondral bone dysfunction, and synovial inflammation, and discusses how this signaling pathway affects development of the disease. We also summarize recent evidences of therapeutic approaches to treat OA by targeting the PI3K/AKT/mTOR pathway, and discuss potential challenges in developing these strategies for clinical treatment of OA.
Bragg-gratings have been frequently used to design compact and high extinction ratio (ER) on-chip polarizers. However, the strong reflection of the unwanted polarization may deteriorate the ...performance of the light source or cause unwanted interferences. In this paper, we propose a Bragg-grating-based all-silicon TM-pass polarizer with low reflection, low insertion loss (IL) and high ER. Unlike previously reported polarizers based on single mode waveguides, we construct the Bragg grating with a multimode waveguide, which not only acts as a Bragg reflector, but also a mode-order converter to convert the reflected TE light into higher order modes to be eventually filtered out by utilizing a tapered transition. On the other hand, the grating has little adverse influence on the TM input light since it works at sub-wavelength-guided wave propagation regime. Finally, the polarizer obtained has a length of 30µm, an ER of 51.83dB, an IL of 0.08dB, and an operating bandwidth of ∼61nm for ER > 30dB at the wavelength of 1.55µm. More importantly, the reflection of the unwanted polarization is suppressed to −12.6dB, which can be further lowered via additional design optimization. Our work points to a new direction for making better on-chip polarizers.
We propose and demonstrate a dual-loop harmonic Fourier domain mode-locked optoelectronic oscillator (FDML-OEO) for drastically reducing the side-mode spurs. The frequency domain mode-locking is ...achieved by synchronizing the scanning period of the filter to an integer fraction of the round trip times of the two loops with a self-made low cost diode-tuned RF filter. We found, for the first time to the best of authors' knowledge, that the frequency scanning bandwidth (FSBW) of the mode-locked output is strongly affected by the length mismatch between the two fiber loops. By using the phase noise of FDML OEO's delayed self-heterodyne signal as a performance indicator, we found experimentally that both the locking bandwidth and the FSBW of the device are inversely proportional to the length mis-match of the two loops. Finally, with dual-loop fiber lengths of 2041m and 2449.2m, including 2039m common fiber loop, we successfully obtained linearly chirped microwave signals around 9GHz with a phase noise of -127dBc/Hz at 10kHz offset from the 9GHz carrier, a FSBW of 0.4GHz, and a chirp rate of 200THz/s at 500.38 kHz repetition rate. More impressively, the side-mode spur ratio of the linear frequency modulated (LFM) signal is reduced to less than -83dB, the lowest ever achieved for a FDML OEO to the best of authors' knowledge, which is more than 50dB improvement over that achieved with a single loop FDML OEO reported previously.
We propose a novel scheme for 3D sensing or Lidar without the need for beam scan or 2D photo-imaging. The scheme is enabled by the combination of a lens' position-to-angle conversion and the ...wavelength division multiplexing/demultiplexing (WDM) commonly used in optical fiber communication systems. However, unlike in a WDM system where different wavelengths carry different data channels, here lights of different wavelengths are demultiplexed into different waveguides or fibers with their exiting ends placed in the focal plane of the lens, which converts the exiting lights into beams of different angles to form a 1D or 2D beam array according to the relative position of the fiber ends with respect to the optical axis of the lens for illuminating the targets and finally sensing the light reflected from different directions. The returned signals are then demultiplexed into different photodetectors to determine the distances of the reflections in different directions. We show that the scheme has the potential to be implemented in photonics integrated circuit (PIC) for low cost production. We successfully demonstrate the scheme with the off-the-shelf discrete fiber optic components using 4 WDM channels and time-of-flight (ToF) technique for distance measurement, although hundreds wavelength channels from a photonic integrated microcomb may be used in practice. Finally, we demonstrate that the angular resolution of the beam array of different wavelengths can be improved by dithering the fiber array or the lens. We believe this new scheme provides an attractive alternative to the MEMS and optical phased array based beam scanning and can be explored further to enable low cost and high speed 3D sensing, particularly Lidar systems.
We propose and demonstrate a four-wavelength-switchable erbium-doped fiber laser (4WS-EDFL) with a four-channel superimposed high-birefringence fiber Bragg grating (SI-HBFBG) and a dual-coupler ring ...based compound-cavity (DCR-CC) filter. Both for the first time, a SI-HBFBG as a four-channel reflective filter is used in a multi-wavelength switchable fiber laser to define wavelength channels and a DCR-CC filter is used to select a single mode from dense longitudinal-modes in a fiber laser. We present in detail how to design, fabricate, and characterize the DCR-CC filter with both theoretical analysis and experimental results, which we believe is the first systematic approach for making a compound-cavity based filter used for selecting single-longitudinal mode (SLM) in a fiber laser. The enhanced polarization hole burning effect in a 2.9 m long erbium-doped fiber, coiled inside a three-loop polarization controller, and the polarization-mismatch-induced losses are introduced into the laser cavity to achieve wavelength-switching operations. We show that the 4WS-EDFL can be switched among fifteen lasing states, including four single-wavelength operations, six dual-wavelength operations, four three-wavelength operations and one four-wavelength operation, all with high stability. For demonstration, in switchable single-wavelength operations, the four SLM lasing outputs measured are all with an optical signal to noise ratio of >80 dB, a linewidth of <700 Hz, a relative intensity noise of ≤-156.7 dB/Hz at frequencies over 3 MHz, an output power fluctuation of ≤0.555 dB and excellent polarization characteristics.
Mg-based materials are promising candidates for high capacity hydrogen storage. However, their poor hydrogenation/dehydrogenation kinetics and high desorption temperature are the main obstacles to ...their applications. This paper reports a method for in situ formation of cycle stable CeH2.73-MgH2-Ni nanocomposites, from the hydrogenation of as-melt Mg80Ce18Ni2 alloy, with excellent hydrogen storage performance. The nanocomposites demonstrate reversible hydrogen storage capacity of more than 4.0 wt %, at a low desorption temperature with fast kinetics and long cycle life. The temperature for the full hydrogenation/dehydrogenation cycle of the composites is significantly decreased to 505 K, which is about 100 K lower than that for pure Mg. The hydrogen desorption activation energy is 63 ± 3 kJ/mol H2 for the composites, which is significantly lower than those of Mg3Ce alloy and pure Mg (104 ± 7 and 158 ± 2 kJ/mol H2, respectively). X-ray diffraction and transmission electron microscopy have been used to reveal the mechanism that delivers this excellent cycle stability and fast hydriding/dehydriding kinetics. It is found that the hydriding/dehydriding process is catalyzed by the combination of in situ formed extremely fine CeH2/CeH2.73 and Ni to Mg/MgH2. In addition, this nanocomposite structure can effectively suppress Mg/MgH2 grain growth and enable the material to maintain its high performance for more than 500 hydrogenation dehydrogenation cycles.
By phase-locking to a commercial reference microwave source with good long-term stability, but relatively poor phase noises at high offset frequencies, we successfully obtained an opto-electronic ...oscillator (OEO) operating at 10 GHz with unprecedented long-term stability while maintaining the OEO’s low phase noise. In particular, for the first time to the best of the authors’ knowledge, we achieved an Allan deviation of Formula Omitted at 1 s, a frequency drift of much less than 0.1 Hz (limited by the resolution of the measurement instrument) for over 10 h, and ultralow phase noises of −124 dBc/Hz@1 kHz and −151 dBc/Hz@10 kHz from the 10 GHz carrier, while maintaining the side-mode spur of less than 90 dB and total spur less than 70 dB. Equally as important, we applied the Laplacian domain feedback noise model to analyze the phase noise properties of the phase-locked OEO, with the analytical results successfully verified experimentally, which not only helps to understand the locking process, but also validates an effective analytical tool for optimizing the operation parameters of the phase-locked OEO. As a result, we are able to suppress the phase noise of the OEO at 10 Hz frequency from the carrier by up to 30 dB from −50 to −80 dBc/Hz, limited primarily by the open loop gain of the feedback loop and the phase noise of reference source. Our work provides a practical OEO reference design for achieving both superb long-term stability and ultralow phase noise for practical applications.
We report what we believe to be the first demonstration of a direct distributed transverse-force (TF) sensing along a single-mode fiber (SMF) using a self-built polarization-analyzing optical ...frequency-domain reflectometry (PA-OFDR). The transverse line-force (TLF) distribution along a SMF can be directly obtained from the absolute measurement of birefringence induced by the TF via photo-elastic effect at different locations along the fiber, without the need of complicated force-to-strain conversion. We show that our system is capable of sensing a weight of merely 0.68 g but yet has a large dynamic range of over 44 dB. In particular, we obtained a maximum detectable TLF of 16.8 N/mm, a minimum detectable TLF of 6.61×10
−4
N/mm, a TLF measurement uncertainty of <2.432%, a TF sensing spatial resolution of 3.7 mm and a TF sensing distance of 103.5 m. We also experimentally investigated the influence of different fiber coatings on the TF sensing and found that the polyimide coating is a better choice due to its high TF measurement sensitivity and response speed, although it induces relatively high residual birefringence in the SMF to limit the minimum detectable TLF. Our work is an important step forward for practical distributed TF sensing and shall prove useful for engineers and scientists to implement the PA-OFDR technology for distributed TF sensing with low cost SMFs.
Most optical characterization methods rely on measuring the complex optical fields emerging from the interaction between light and material systems. Nevertheless, inherent scattering and absorption ...cause ambiguities in both interferometric and noninterferometric attempts to measure phase. Here we demonstrate that the complete information about a probe optical field can be encoded into the states of polarization, and develop a topography measurement method by blindly varying the ambient refractive index surrounding the sample in a wedged cuvette, which is capable of simultaneously measuring the thickness and the ambient refractive index of the sample in real time, as well as extending the measurement range of the sample thickness. With the method, we have successfully measured the topography of a 136.7 µm thick coverslip by blindly changing the ambient refractive index by 0.001246, resulting in the thickest sample characterization ever achieved by quantitative phase imaging, to the best of our knowledge. An efficient and complete characterization of optical fields is critical for any high-resolution imaging approach and the technique demonstrated here should prove attractive for applications ranging from microscopy to remote sensing. Thanks to the high precision and fast response speed, this method may pave a new way for measuring the topography of the thick samples, such as biological tissues.
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