阿尔茨海默病A/T/N研究框架及其磁共振成像研究进展

随着全球老龄化程度加剧,老年神经变性疾病发病率显著增高。其中,阿尔茨海默病(Alzheimer's disease,AD)是目前最常见的神经变性疾病,已成为当下的全球公共卫生难题。AD相关的核心病理改变主要包括细胞外β淀粉样蛋白(Amyloid-β,Aβ)沉积与细胞内神经纤维缠结(neurofibrillary tangles,NFT),在出现临床症状前数十年就已存在[1]。因此,神经病理学检查是定义AD的金标准。

Xueshuantong improves cerebral blood perfusion in elderly patients with lacunar infarction

A total of 64 patients with acute lacunar infarction were enrolled within 24 hours of onset. The patients received conventional therapy （antiplatelet drugs and hypolipidemic drugs） alone or conventional therapy plus 450 mg Xueshuantong once a day. The main ingredient of the Xueshuantong lyophilized powder used for injection was Panax notoginseng saponins. Assessments were made at admission and at discharge using the National Institutes of Health Stroke Scale, the Activity of Daily Living and the Mini-Mental State Examination. Additionally, the relative cerebral blood flow, relative cerebral blood volume and relative mean transit time in the region of interest were calculated within 24 hours after the onset of lacunar infarction, using dynamic susceptibility contrast magnetic resonance perfusion imaging technology. Patients underwent a follow-up MRI scan after 4 weeks of treatment. There was an improvement in the Activity of Daily Living scores and a greater reduction in the scores on the National Institutes of Health Stroke Scale in the treatment group than in the control group. However, the Mini-Mental State Examination scores showed no significant differences after 4 weeks of treatment. Compared with the control group, the relative cerebral blood flow at discharge had increased and showed a greater improvement in the treatment group. Furthermore, there was a reduction in the relative mean transit time at discharge and the value was lower in the treatment group than in the control group. The experimental findings indicate that Xueshuantong treatment improves neurological deficits in elderly patients with lacunar infarction, and the mechanism may be related to increased cerebral perfusion.

Magnetic Resonance Imaging Studies of Neurodegenerative Disease:From Methods to Translational Research

Neurodegenerative diseases(NDs)have become a significant threat to an aging human society.Numerous studies have been conducted in the past decades to clarify their pathologic mechanisms and search for reliable biomarkers.Magnetic resonance imaging(MRI)is a powerful tool for investigating structural and functional brain alterations in NDs.With the advantages of being non-invasive and non-radioactive,it has been frequently used in both animal research and large-scale clinical investigations.MRI may serve as a bridge connecting micro-and macro-level analysis and promoting bench-to-bed translational research.Nevertheless,due to the abundance and complexity of MRI techniques,exploiting their potential is not always straightforward.This review aims to briefly introduce research progress in clinical imaging studies and discuss possible strategies for applying MRI in translational ND research.

Optical meta-waveguides for integrated photonics and beyond

The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits,giving rise to numerous metawaveguides with unprecedented strength in controlling guided electromagnetic waves.Here,we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms,such as dielectric or plasmonic waveguides and optical fibers.Foundational results and representative applications are comprehensively summarized.Brief physical models with explicit design tutorials,either physical intuition-based design methods or computer algorithms-based inverse designs,are cataloged as well.We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems,by enhancing light-matter interaction strength to drastically boost device performance,or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities.We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits,biomedical sensing,artificial intelligence and beyond.

Inverse design of digital nanophotonic devices using the adjoint method

A high-efficiency inverse design of"digital"subwavelength nanophotonic devices using the adjoint method is proposed.We design a single-mode 3dB power divider and a dual-mode demultiplexer to demonstrate the efficiency of the proposed inverse design approach,called the digitized adjoint method,for single-and dual-object optimization,respectively.The optimization comprises three stages:1)continuous variation for an"analog"pattern;2)forced permittivity biasing for a"quasi-digital"pattern;and 3)a multilevel digital pattern.Compared with the conventional brute-force method,the proposed method can improve design efficiency by about five times,and the performance optimization can reach approximately the same level.The method takes advantages of adjoint sensitivity analysis and digital subwavelength structure and creates a new way for the efficient and high-performance design of compact digital subwavelength nanophotonic devices,which could overcome the efficiency bottleneck of the brute-force method,which is restricted by the number of pixels of a digital pattern,and improve the device performance by extending a conventional binary pattern to a multilevel one.

Ultracompact dual-mode waveguide crossing based on subwavelength multimode-interference couplers

We propose and experimentally demonstrate a novel ultracompact dual-mode waveguide crossing based on subwavelength multimode-interference couplers for a densely integrated on-chip mode-division multiplexing system.By engineering the lateral-cladding material index and manipulating phase profiles of light at the nanoscale using an improved inverse design method, a subwavelength structure could theoretically realize the identical beat length for both TE_0 and TE1, which can reduce the scale of the device greatly. The fabricated device occupied a footprint of only 4.8 μm× 4.8 μm. The measured insertion losses and crosstalks were less than 0.6 d B and-24 d B from 1530 nm to 1590 nm for both TE0 and TE1 modes, respectively. Furthermore, our scheme could also be expandedto design waveguide crossings that support more modes.

Longitudinal Alterations of Local Spontaneous Brain Activity in Parkinson's Disease

We used resting-state fMRI to evaluate longitu- dinal alterations in local spontaneous brain activity in Parkinson＇s disease （PD） over a 2-year period. Data were acquired from 23 PD patients at baseline and follow-up, and 27 age- and sex-matched normal controls. Regional homogeneity （ReHo） and voxel-based-morphometry （VBM） were used to identify differences in local sponta- neous brain activity and grey matter volume. With disease progression, we observed a progressive decrease in ReHo in the sensorimotor cortex, default-mode network, and left cerebellum, but increased ReHo in the supplementary motor area, bilateral temporal gyrus, and hippocampus. Moreover, there was a significant positive correlation between the rates of ReHo change in the left cerebellum and the rates of change in the Unified Parkinson＇s Disease Rating Scale-III scores. VBM revealed no significant differences in the grey matter volume among the three sets of acquisitions. We conclude that ReHo may be a suitable non-invasive marker of progression in PD.

Region-Specific Iron Measured by MRI as a Biomarker for Parkinson's Disease

The identification of sensitive and specific biomarkers for Parkinson＇s disease （PD） poses an impor- tant clinical challenge. A potential biomarker for early diagnosis and disease monitoring of PD is region-specific iron. Iron accumulation in the substantia nigra pars compacta is considered a main characteristic of PD. However, questions remain, such as the relationship between nigral iron and clinical indices of PD （motor impairment or disease duration）. Further, previous studies have suggested the influence of iron on other nuclei. Iron quantification using magnetic resonance imaging （MRI） allows for studies of the relationship between regional iron and clinical symptoms in vivo. Thus, in this review we discuss the following topics： the technological develop- ment of MRI in measuring brain iron, nigral iron as a potential marker for PD in both clinical and prodromal stages, other influences of regional iron on PD, and clinical translation and future perspectives.

On-chip cyclic-AWG-based 12 × 12 silicon wavelength routing switches with minimized port-to-port insertion loss fluctuation

With the rapidly increasing bandwidth requirements of optical communication networks, compact and low-cost large-scale optical switches become necessary. Silicon pbotonics is a promising technology due to its small footprint, cost competitiveness, and high bandwidth density. In this paper, we demonstrate a 12 × 12 silicon wavelength routing switch employing cascaded arrayed waveguide interconnection network on a the switch＇s footprint. We single chip. We optimize develop an algorithm based gratings （AWGs） connected by a silicon waveguide the connecting strategy of the crossing structure to reduce on minimum standard deviation to minimize the port-to- port insertion loss （IL） fluctuation of the switch globally. The simulated port-to-port IL fluctuation decreases by about 3 dB compared with that of the conventional one. The average measured port-to-port IL is 13.03 dB, with a standard deviation of 0.78 dB and a fluctuation of 2.39 dB. The device can be used for wide applications in core networks and data centers.

Highly efficient tunable optical filter based on liquid crystal micro-ring resonator with large free spectral range

A highly efficient tunable optical filter of liquid crystal （LC） optical micro-r/rig resonator （MRR） was proposed. The 4-pro-radius ring consists of a silicon-on- insulator （SOI） asymmetric bent slot waveguide with a LC cladding. The geometry of the slot waveguide resulted in the strong electro-optic effect of the LC, and therefore induced an increase in effective refractive index by 0.0720 for the quasi-TE mode light in the slot-waveguide. The ultra-wide tuning range （56.0 nm） and large free spectral range （FSR） （-28.0nm） of the optical filters enabled wavelength reconfigurable multiplexing devices with a drive voltage of only 5 V. The influences of parameters, such as the slot width, total width of Si rails and slot shift on the device＇s performance, were analyzed and the optimal design was given. Moreover, the influence of fabrication tolerances and the loss of device were both investigated. Compared with state-of-the-art tunable MRRs, the proposed electrically tunable micro-ring resonator owns the excellent features of wider tuning ranges, larger FSRs and ultralow voltages.

4×4 MIMO fiber-wireless transmission based on an integrated four-channel directly modulated optical transceiver

In this paper, an integrated compact four-channel directly modulated analog optical transceiver is proposed and fabricated. The 3 d B bandwidth of this optical transceiver exceeds 20 GHz, and the measured spurious-free dynamic range is up to 91.2 d B · Hz^2∕3. The optical coupling efficiency(CE) is improved by using a precise submicron alignment technique for lens coupling in a transmitter optical subassembly, and the highest CE is achieved when the oblique angle of the arrayed waveguide grating using a silica-based planar lightwave circuit(AWG-PLC) in receiver optical sub assembly is set to 42°. Based on the proposed optical transceiver, we have experimentally demonstrated a 6.624 Gbit/s 4 × 4 multi-input multioutput(MIMO) 16-quadrature amplitude modulation orthogonal frequency division multiplexing(16 QAM-OFDM) radio signal over 15.5 km standard single mode fiber, together with 1.2 m wireless transmission in both an uplink and a downlink. To cope with the channel interference and noise of the fiber-wireless transmission system, a low-complexity MIMO demodulation algorithm based on lattice reduction zero-forcing(LR-ZF) is designed. In our experiment, 1.6 d B power penalty is achieved by using the proposed LR-ZF algorithm, compared to the commonly used zero-forcing algorithm.Moreover, this LR-ZF algorithm has much less complexity than the optimal maximum-likelihood sequence estimation(MLSE) at a given transmission performance. These results not only demonstrate the feasibility of the integrated optical transceiver for MIMO fiber-wireless application but also validate that the proposed LR-ZF algorithm is effective to eliminate the interference for hybrid fiber-wireless transmission.

On-chip reconfigurable mode converter based on cross-connected subwavelength Y-junctions

A novel power-efficient reconfigurable mode converter is proposed and experimentally demonstrated based on cross-connected symmetric Y-junctions assisted by thermo-optic phase shifters on a silicon-on-insulator platform.Instead of using conventional Y-junctions,subwavelength symmetric Y-junctions are utilized to enhance the mode splitting ability.The reconfigurable functionality can be realized by controlling the induced phase differences.Benefited from the cross-connected scheme,the number of heating electrodes can be effectively reduced,while the performance of the device is maintained.With only one-step etching,our fabricated device shows the average insertion losses and cross talks are less than 2.45 and-16.6 d B,respectively,measured with conversions between two arbitrary compositions of the first four TE modes over an observable 60 nm bandwidth.The converter is switchable and CMOS-compatible,and could be extended for more modes;hence,it can be potentially deployed for advanced and flexible mode multiplexing optical networks-on-chip.