Pericytes,the mural cells enveloping small vessels,play a crucial role in maintaining the integrity of the blood-brain barrier(BBB)(Armulik et al.,2010;Daneman et al.,2010).Their loss leads to significant defects in B...Pericytes,the mural cells enveloping small vessels,play a crucial role in maintaining the integrity of the blood-brain barrier(BBB)(Armulik et al.,2010;Daneman et al.,2010).Their loss leads to significant defects in BBB function,characterized by increased transcytosis across endothelial cells(ECs),diminished deposition of the cerebrovascular basement membrane,and compromised differentiation of astrocyte end-feet(Armulik et al.,2010;Daneman et al.,2010).展开更多
Photonic integrated switches that are both space and wavelength selective are a highly promising technology for data-intensive applications as they benefit from multi-dimensional manipulation of optical signals.Howeve...Photonic integrated switches that are both space and wavelength selective are a highly promising technology for data-intensive applications as they benefit from multi-dimensional manipulation of optical signals.However,scaling these switches normally poses stringent challenges such as increased fabrication complexity and control difficulties,due to the growing number of switching elements.In this work,we propose a new type of dilated crosspoint topology,which efficiently handles both space and wavelength selective switching,while reducing the required switching element count by an order of magnitude compared to reported designs.To the best of our knowledge,our design requires the fewest switching elements for an equivalent routing paths number and it fully cancels the first-order in-band crosstalk.We demonstrate such an ultra-compact space-and-wavelength selective switch(SWSS)at a scale of 4×4×4λ on the silicon-on-insulator(SOI)platform.Experimental results reveal that the switch achieves an insertion loss ranging from 2.3 dB to 8.6 dB and crosstalk levels in between−35.3 dB and−59.7 dB.The add-drop microring-resonators(MRRs)are equipped with micro-heaters,exhibiting a rise and fall time of 46μs and 0.33μs,respectively.These performance characteristics highlight the switch’s ultralow element count and crosstalk with low insertion loss,making it a promising candidate for advanced data center applications.展开更多
Silicon photonic switches are widely considered as a cost-effective solution for addressing the ever-growing data traffic in datacenter networks,as they offer unique advantages such as low power consumption,low latenc...Silicon photonic switches are widely considered as a cost-effective solution for addressing the ever-growing data traffic in datacenter networks,as they offer unique advantages such as low power consumption,low latency,small footprint and high bandwidth.Despite extensive research efforts,crosstalk in large-scale photonic circuits still poses a threat to signal integrity.In this paper,we present two designs of silicon Mach-Zehnder Interferometer(MZI)switches achieving ultra-low-crosstalk,driven thermally and electrically.Each switch fabric is optimized at both the device and circuit level to suppress crosstalk and reduce system complexity.Notably,for the first time to the best of our knowledge,we harness the inherent self-heating effect in a carrier-injection-based MZI switch to create a pair of phase shifters that offers arbitrary phase differences.Such a pair of phase shifters induces matched insertion loss at each arm,thus minimizing crosstalk.Experimentally,an ultra-low crosstalk ratio below−40 dB is demonstrated for both thermooptic(T-O)and electro-optic(E-O)switches.The T-O switch exhibits an on-chip loss of less than 5 dB with a switching time of 500µs,whereas the E-O switch achieves an on-chip loss as low as 8.5 dB with a switching time of under 100 ns.In addition,data transmission of a 50 Gb/s on–off keying signal is demonstrated with high fidelity on the E-O switch,showing the great potential of the proposed switch designs.展开更多
The fruits of China＇s rapid economic development over the 3 decades have not been distributed fairly across different regions. Using data from a sample of 815 Chinese listed firrns during 1998-2004, our error-correct...The fruits of China＇s rapid economic development over the 3 decades have not been distributed fairly across different regions. Using data from a sample of 815 Chinese listed firrns during 1998-2004, our error-correction investment model showes evidence of different financial constraints on firms＇ investment in different regions. We argue that China＇s regional development policies have contributed greatly to the regional inequalities. To control the rising inequality, China has shifted its focus from the coast to the interior regions. However, it is becoming increasingly difficult for the government to direct the economy, as market mechanisms now have afar greater influence on the economy than the government does. The people-centered approach of the current leadership has meant that substantial attention has been placed on regional development disparities in an attempt to build a ＂harmonious society. ＂ China needs further extensive reforms if all the measures for reducing regional disparity are to be effective.展开更多
An N×N iterative photonic processor is proposed for the first time, we believe, for fast computation of complexvalued matrix inversion, a fundamental but computationally expensive linear algebra operation. Compar...An N×N iterative photonic processor is proposed for the first time, we believe, for fast computation of complexvalued matrix inversion, a fundamental but computationally expensive linear algebra operation. Compared to traditional digital electronic processing, optical signal processing has a few unparalleled features that could enable higher representational efficiency and faster computing speed. The proposed processor is based on photonic integration platforms–the inclusion of Ⅲ-V gain blocks offers net neutral loss in the phase-sensitive loops. This is essential for the Richardson iteration method that is adopted in this paper for complex linear systems. Wavelength multiplexing can be used to significantly improve the processing efficiency, allowing the computation of multiple columns of the inverse matrix using a single processor core. Performances of the key building blocks are modeled and simulated, followed by a system-level analysis, which serves as a guideline for designing an N×N Richardson iteration processor. An inversion accuracy of>98%can be predicted for a 64×64 photonic processor with a>80times faster inversion rate than electronic processors. Including the power consumed by both active components and electronic circuits, the power efficiency of the proposed processor is estimated to be over an order of magnitude more energy-efficient than electronic processors. The proposed iterative photonic integrated processor provides a promising solution for future optical signal processing systems.展开更多
基金supported by the National Key R&D Program of China(2019YFA0801603 to J.L.)National Natural Science Foundation of China(31701265 to X.P.)+2 种基金Shanghai Natural Science Foundation(22ZR1469700 to J.L.)SA-SIBS Scholarship Program(to J.L.)Youth Innovation Promotion Association of Chinese Academy of Sciences(to J.L.)。
文摘Pericytes,the mural cells enveloping small vessels,play a crucial role in maintaining the integrity of the blood-brain barrier(BBB)(Armulik et al.,2010;Daneman et al.,2010).Their loss leads to significant defects in BBB function,characterized by increased transcytosis across endothelial cells(ECs),diminished deposition of the cerebrovascular basement membrane,and compromised differentiation of astrocyte end-feet(Armulik et al.,2010;Daneman et al.,2010).
基金Engineering and Physical Sciences Research Council (EP/T028475/1)European Union's Horizon Europe Research and Innovation Program (101070560,101017088)。
文摘Photonic integrated switches that are both space and wavelength selective are a highly promising technology for data-intensive applications as they benefit from multi-dimensional manipulation of optical signals.However,scaling these switches normally poses stringent challenges such as increased fabrication complexity and control difficulties,due to the growing number of switching elements.In this work,we propose a new type of dilated crosspoint topology,which efficiently handles both space and wavelength selective switching,while reducing the required switching element count by an order of magnitude compared to reported designs.To the best of our knowledge,our design requires the fewest switching elements for an equivalent routing paths number and it fully cancels the first-order in-band crosstalk.We demonstrate such an ultra-compact space-and-wavelength selective switch(SWSS)at a scale of 4×4×4λ on the silicon-on-insulator(SOI)platform.Experimental results reveal that the switch achieves an insertion loss ranging from 2.3 dB to 8.6 dB and crosstalk levels in between−35.3 dB and−59.7 dB.The add-drop microring-resonators(MRRs)are equipped with micro-heaters,exhibiting a rise and fall time of 46μs and 0.33μs,respectively.These performance characteristics highlight the switch’s ultralow element count and crosstalk with low insertion loss,making it a promising candidate for advanced data center applications.
基金supported by the UK EPSRC Programme Grant QUDOS(EP/T028475/1)TRANSNET(EP/R035342/1)+3 种基金Communication Hub TITAN(EP/X04047X/1 and EP/Y037243/1)UK EPSRC CEPS CDT(EP/S022139/1)the European Union’s Horizon Europe Research and Innovation Program under Agreement 101070560(PUNCH)the European Union’s Horizon 2020 research and innovation program,project INSPIRE(101017088).
文摘Silicon photonic switches are widely considered as a cost-effective solution for addressing the ever-growing data traffic in datacenter networks,as they offer unique advantages such as low power consumption,low latency,small footprint and high bandwidth.Despite extensive research efforts,crosstalk in large-scale photonic circuits still poses a threat to signal integrity.In this paper,we present two designs of silicon Mach-Zehnder Interferometer(MZI)switches achieving ultra-low-crosstalk,driven thermally and electrically.Each switch fabric is optimized at both the device and circuit level to suppress crosstalk and reduce system complexity.Notably,for the first time to the best of our knowledge,we harness the inherent self-heating effect in a carrier-injection-based MZI switch to create a pair of phase shifters that offers arbitrary phase differences.Such a pair of phase shifters induces matched insertion loss at each arm,thus minimizing crosstalk.Experimentally,an ultra-low crosstalk ratio below−40 dB is demonstrated for both thermooptic(T-O)and electro-optic(E-O)switches.The T-O switch exhibits an on-chip loss of less than 5 dB with a switching time of 500µs,whereas the E-O switch achieves an on-chip loss as low as 8.5 dB with a switching time of under 100 ns.In addition,data transmission of a 50 Gb/s on–off keying signal is demonstrated with high fidelity on the E-O switch,showing the great potential of the proposed switch designs.
文摘The fruits of China＇s rapid economic development over the 3 decades have not been distributed fairly across different regions. Using data from a sample of 815 Chinese listed firrns during 1998-2004, our error-correction investment model showes evidence of different financial constraints on firms＇ investment in different regions. We argue that China＇s regional development policies have contributed greatly to the regional inequalities. To control the rising inequality, China has shifted its focus from the coast to the interior regions. However, it is becoming increasingly difficult for the government to direct the economy, as market mechanisms now have afar greater influence on the economy than the government does. The people-centered approach of the current leadership has meant that substantial attention has been placed on regional development disparities in an attempt to build a ＂harmonious society. ＂ China needs further extensive reforms if all the measures for reducing regional disparity are to be effective.
文摘An N×N iterative photonic processor is proposed for the first time, we believe, for fast computation of complexvalued matrix inversion, a fundamental but computationally expensive linear algebra operation. Compared to traditional digital electronic processing, optical signal processing has a few unparalleled features that could enable higher representational efficiency and faster computing speed. The proposed processor is based on photonic integration platforms–the inclusion of Ⅲ-V gain blocks offers net neutral loss in the phase-sensitive loops. This is essential for the Richardson iteration method that is adopted in this paper for complex linear systems. Wavelength multiplexing can be used to significantly improve the processing efficiency, allowing the computation of multiple columns of the inverse matrix using a single processor core. Performances of the key building blocks are modeled and simulated, followed by a system-level analysis, which serves as a guideline for designing an N×N Richardson iteration processor. An inversion accuracy of>98%can be predicted for a 64×64 photonic processor with a>80times faster inversion rate than electronic processors. Including the power consumed by both active components and electronic circuits, the power efficiency of the proposed processor is estimated to be over an order of magnitude more energy-efficient than electronic processors. The proposed iterative photonic integrated processor provides a promising solution for future optical signal processing systems.
