| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Qu, Yanhua, 1974-, et al.
(författare)
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Ground tit genome reveals avian adaptation to living at high altitudes in the Tibetan plateau.
- 2013
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 2071-
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Tidskriftsartikel (refereegranskat)abstract
- The ground tit (Parus humilis) is endemic to the Tibetan plateau. It is a member of family Paridae but it was long thought to be related to the ground jays because of their morphological similarities. Here we present the ground tit's genome and re-sequence two tits and one ground jay, to clarify this controversially taxonomic status and uncover its genetic adaptations to the Tibetan plateau. Our results show that ground tit groups with two tits and it diverges from them between 7.7 and 9.9 Mya. Compared with other avian genomes, ground tit shows expansion in genes linked to energy metabolism and contractions in genes involved in immune and olfactory perception. We also found positively selected and rapidly evolving genes in hypoxia response and skeletal development. These results indicated that ground tit evolves basic strategies and 'tit-to-jay' change for coping with the life in an extreme environment.
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| 3. |
- Zhang, Longhai, et al.
(författare)
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Rational Design of Multinary Metal Chalcogenide Bi0.4Sb1.6Te3 Nanocrystals for Efficient Potassium Storage
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Ingår i: Advanced Materials. - 0935-9648.
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Tidskriftsartikel (refereegranskat)abstract
- Multinary metal chalcogenides hold considerable promise for high-energy potassium storage due to their numerous redox reactions. However, challenges arise from issues such as volume expansion and sluggish kinetics. Here, a design featuring a layered ternary Bi0.4Sb1.6Te3 anchored on graphene layers as a composite anode, where Bi atoms act as a lattice softening agent on Sb, is presented. Benefiting from the lattice arrangement in Bi0.4Sb1.6Te3 and structure, Bi0.4Sb1.6Te3/graphene exhibits a mitigated expansion of 28% during the potassiation/depotassiation process and demonstrates facile K+ ion transfer kinetics, enabling long-term durability of 500 cycles at various high rates. Operando synchrotron diffraction patterns and spectroscopies including in situ Raman, ex situ adsorption, and X-ray photoelectron reveal multiple conversion and alloying/dealloying reactions for potassium storage at the atomic level. In addition, both theoretical calculations and electrochemical examinations elucidate the K+ migration pathways and indicate a reduction in energy barriers within Bi0.4Sb1.6Te3/graphene, thereby suggesting enhanced diffusion kinetics for K+. These findings provide insight in the design of durable high-energy multinary tellurides for potassium storage.
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| 4. |
- Li, Hansen, et al.
(författare)
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Can Residential Greenspace Exposure Improve Pain Experience? A Comparison between Physical Visit and Image Viewing
- 2021
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Ingår i: Healthcare. - : MDPI. - 2227-9032. ; 9:7
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Tidskriftsartikel (refereegranskat)abstract
- Reducing the burden of pain via greenspace exposure is a rising research topic. However, insufficient evidence has been found in relation to the environmental effect itself. Residential greenspace, as a convenient but limited natural environment for urban dwellers, has benefits and services yet to be discovered. Therefore, the current study recruited 24 young adults to evaluate the effects of physical visit to, or image viewing of, residential greenspace on pain perception and related psychophysiological outcomes, via simulated pain. Pain threshold and tolerance were recorded via the level of pain stimuli, and pain intensity was evaluated using the Visual Analog Scale (VAS). The state scale of the State-Trait Anxiety Inventory (STAI-S) and two adjective pairs were employed to measure the state anxiety and subjective stress, respectively. Meanwhile, heart rate (HR), heart rate variability (HRV), and blood pressure (BP) were measured to investigate physiological responses. Besides, Scenic Beauty Estimation (SBE) was also employed to assess participants' preference regarding the experimental environments. The results revealed that visiting the greenspace significantly increased the pain threshold and tolerance, while no significant effect was observed for image viewing. On the other hand, no significant difference was observed in pain-related psychophysiological indices between the experimental settings, but significantly negative associations were found between the scores of SBE and subjective stress and state anxiety. In conclusion, the current study brings experimental evidence of improving pain experience via residential greenspace exposure, while the related psychophysiological benefits require further investigation.
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| 5. |
- Li, Hansen, et al.
(författare)
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Green Exercise : Can Nature Video Benefit Isometric Exercise?
- 2021
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 18:11
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Tidskriftsartikel (refereegranskat)abstract
- Green exercise is the combination of physical activity and nature exposure, which has been associated with positive effects on psychophysiological health. This study aimed to investigate the effects of nature video viewing on isometric exercise and find a useful practice for green exercise in urban living. In the current study, 18 male subjects were recruited in a randomized crossover trial and underwent a sequence of wall squat exercises. The whole experiment contained three periods of baseline (before exercise), exercise, and recovery (after exercise), and each period lasted for 2 min. A video of forest walking was played in the exercise and recovery periods as treatment, while a black screen was set as control. The Rate of Perceived Exertion Scale (RPE) and Feeling Scale (FS) were employed to measure perceived exertion and affective responses in the exercise period; heart rate (HR) and heart rate variability (HRV) including the standard deviation of normal-to-normal RR intervals (SDNN), the root mean square of successive differences (RMSSD), and the standard deviations of the Poincaré plot (SD1), were recorded in the three periods. Heart rate recovery (HRR) in the recovery period was further calculated based on 30 s and 60 s time frames. Results demonstrated that during the exercise period nature video viewing was associated with better affective responses (median of 1.00 and an interquartile (IQR) of 2.00, p = 0.017), lower perceived exertion (median = 6.00, IQR = 2.00, p = 0.021), and lower HR (median = 89.60, IQR = 20.94, p = 0.01), but the differences in HRV indices between the experimental settings were not statistically significant. In the recovery period, significantly higher values of RMSSD (median = 34.88, IQR = 24.52, p = 0.004), SD1 (median = 24.75, IQR = 17.41, p = 0.003), and HR (median = 84.18, IQR = 16.58, p = 0.001) were observed in the treatment setting, whereas no statistically significant difference was found for HRR. In general, our findings support that nature video viewing may help reduce perceived exertion, increase exercise pleasure, buffer heart rate, and improve cardiac autonomic recovery for wall squat exercising, which implies the potential of nature-based stimuli in green exercise. However, due to the limited research sample, further study may need to include female participants and focus on various populations to confirm the effectiveness of using virtual and environments depicting nature at home or in public exercise places to promote positive exercise experience.
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| 6. |
- Li, Hansen, et al.
(författare)
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Psychological benefits of green exercise in wild or urban greenspaces : A meta-analysis of controlled trials
- 2022
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Ingår i: Urban Forestry & Urban Greening. - : Elsevier. - 1618-8667 .- 1610-8167. ; 68
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Tidskriftsartikel (refereegranskat)abstract
- Green exercise, the combination of exercise and nature exposure, is known to benefit physical and mental health. However, there is a lack of quantitative evidence to support the psychological advantage of green exercise over non-green exercise. Also, it is unclear if there are psychological differences between green exercise in wild environments and urban greenspaces. Therefore, we conducted a systematic literature search for outcomes concerning measures including the Profile of Mood States (POMS), Spielberger State-Trait Anxiety Inventory (STAI), Semantic Differential Method (SDM), Positive and Negative Affect Schedule (PANAS), and Restorative Outcome Scale (ROS). Nineteen studies with 1662 participants were included in a meta-analysis to examine the advantages of green exercise and compare them in the two types of natural environments. The results indicate that green exercise may lower negative affect, including anxiety, tension, anger, depression, and fatigue. Meanwhile, green exercise may lead to higher positive moods and emotions, including vigor, comfort, natural feeling, and relaxation. Nevertheless, the effect on overall positive affect was not statistically significant. The comparative results suggest that wild environments may be more effective than urban greenspaces in improving vigor and comfort during green exercise. In conclusion, our findings support the advantages of green exercise over non-green exercise, meanwhile implying potential psychological differences between exercises in wild environments and urban greenspaces. Due to the limited number of studies and high heterogeneities, a future review is warranted to re-examine the psychological benefits.
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| 7. |
- Pang, Xiaodan, Dr., et al.
(författare)
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Key technologies to enable terabit-scale digital radio-over-fiber systems
- 2019
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9781510625327
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Konferensbidrag (refereegranskat)abstract
- With the approach of the 5G era, stringent requirements are imposed on the data transport solutions, including both of the supported transmission reach and the capacity. Radio-over-fiber technologies are considered to be promising candidates to cope with both aspects, owing to the low-loss and broad-bandwidth nature of the optical fibers. Meanwhile with such optical transport solutions, signals can be collected from the distributed remote radio sites and processed in a centralized manner. In this report, we target on the digital radio-over-fiber systems, and discuss about several key technologies, focusing on the aspects of coding and transmission, which could potentially enable terabit-scale data transport.
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| 8. |
- Qiu, Zhijun, et al.
(författare)
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Role of Si implantation in control of underlap length in Schottky-barrier source/drain MOSFETs on ultrathin body SOI
- 2008
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Ingår i: Proceedings of ULIS. - NEW YORK : IEEE. ; , s. 175-178, s. 175-178
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Konferensbidrag (refereegranskat)abstract
- This works demonstrates a novel approach using Si implantation prior to Pt deposition and PtSi formation to control the underlap length between the PtSi source/drain regions to the gate in Schottky-Barrier (SB-) MOSFETs. Dopant segregation at the PtSi/Si interface is used to enhance device performance. With the lon /Ioff current ratio as an indicator, optimized Si implant doses are found for both n- and p-channel SB-MOSFETs. Through an effective barrier width, the underlap length has direct implication on the leakage current.
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| 9. |
- Wang, Yu, et al.
(författare)
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A Novel MIMO-SAR Echo Separation Solution for Reducing the System Complexity : Spectrum Preprocessing and Segment Synthesis
- 2023
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Ingår i: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892. ; 61
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Tidskriftsartikel (refereegranskat)abstract
- The problem of echo separation using digital beamforming (DBF) on receive for multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) is of notable importance to allow for practical systems. Regrettably, current DBF-MIMO-SAR schemes, such as the short-term shift-orthogonal (STSO) scheme, are computationally cumbersome, increasing the required hardware complexity. To alleviate this problem, we here propose an improved echo separation solution for realizing a low-cost MIMO-SAR system. We detail a generic waveform design scheme and optimized monostatic radar waveforms (e.g., nonlinear frequency modulation (NLFM) signal), showing how these can be directly adopted in the proposed scheme to improve imaging performance. The proposed scheme enables the number of interference segments generated by unmatched waveforms to be halved by the use of the fast time spectrum preprocessing and segment synthesis, dramatically simplifying the array configuration, and reduces the system complexity. By exploiting interpulse phase coding techniques, the proposed method can provide a reconfigurable waveform transmitting scheme, allowing the system resources in range frequency, elevation space, and Doppler domains to be jointly exploited for the separation of aliased signal returns. The proposed scheme is evaluated using extensive numerical and measured datasets, demonstrating the feasibility and potential of the proposed method for resource-limited spaceborne/airborne MIMO-SAR systems.
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| 10. |
- Zhang, Lu, et al.
(författare)
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Nonlinearity-aware 200 Gbit/s DMT transmission for C-band short-reach optical interconnects with a single packaged electro-absorption modulated laser
- 2018
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Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 43:2, s. 182-185
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the transmission of a 200 Gbit/s discrete multitone (DMT) at the soft forward error correction limit in an intensity-modulation direct-detection system with a single C-band packaged distributed feedback laser and traveling-wave electro absorption modulator (DFB-TWEAM), digital-to-analog converter and photodiode. The bit-power loaded DMT signal is transmitted over 1.6 km standard single-mode fiber with a net rate of 166.7 Gbit/s, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. Meanwhile, net rates of 174.2 Gbit/s and 179.5 Gbit/s are also demonstrated over 0.8 km SSMF and in an optical back-to-back case, respectively. The feature of the packaged DFB-TWEAM is presented. The nonlinearity-aware digital signal processing algorithm for channel equalization is mathematically described, which improves the signal-to-noise ratio up to 3.5 dB.
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| 11. |
- Zhang, Xing, et al.
(författare)
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Auto-Regulation Method vs. Fixed-Loading Method in Maximum Strength Training for Athletes : A Systematic Review and Meta-Analysis
- 2021
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Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 12
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Forskningsöversikt (refereegranskat)abstract
- The auto-regulation method is a rising training strategy to improve strength and motor performance, and the Autoregulatory Progressive Resistance Exercise (APRE), Rating of Perceived Exertion program (RPE), and Velocity-Based Training (VBT) are the three common auto-regulation programs. However, whether the auto-regulation method is more effective than the traditional strength training (the fixed-loading method) in maximum strength training is still unclear. The present study searched the Pubmed, SPORTDiscus, Web of Science, Embase, EBSCO, Cochrane, CNKI, and CQVIP databases, and included eight related studies published between 2010 and 2020, with a total of 166 subjects including division 1 college players and athletes with at least 1-year training history, and interventions ranging from 5 to 10 weeks. A meta-analysis was performed to check the difference between the two training methods, and analyzed the differences in the existing auto-regulation programs' effectiveness. The overall results showed that the auto-regulation method was more effective than the fixed-loading method in maximum strength training (effect size = 0.64; P < 0.001; I2 = 0%). In specific, the pooled results in subgroup analysis indicated that the auto-regulation method may effectively improve the strength performance in squat (effect size = 4.64; P < 0.05; I2 = 54%) and bench press (effect size = 3.21; P < 0.05; I2 = 62%). Greater benefits of the auto-regulation method on strength improvement could be achieved in an 8-week or even shorter training (effect size = 0.87; P < 0.001; I2 = 0%) compared with those of 8–10 weeks (effect size = 0.32; P < 0.001; I2 = 0%). The APRE is the most effective training program among the three auto-regulation programs (effect size = 0.78; P < 0.001; I2 = 0%). In conclusion, the auto-regulation method could be more effective than the fixed-loading method in maximum strength training. The APRE is a convenient and effective training program that may be considered a practical training program to replace traditional training in athletes.
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| 12. |
- Gong, Ze, et al.
(författare)
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The Association Between Quadriceps Strength and Synovitis in Knee Osteoarthritis : An Exploratory Study From the Osteoarthritis Initiative
- 2023
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Ingår i: The Journal of rheumatology. - : The Journal of Rheumatology. - 0315-162X .- 1499-2752. ; 50:4, s. 548-555
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of this study was to explore the association between quadriceps strength and synovitis in knee osteoarthritis (KOA). METHODS: This study was derived from the Osteoarthritis Initiative (OAI), which recruited adults from the OAI cohort with or at risk of KOA. Knees with complete records of isometric quadriceps strength and effusion-synovitis and Hoffa-synovitis assessments were included. Quadriceps strength was measured isometrically at baseline. Effusion-synovitis and Hoffa-synovitis were measured using the Magnetic Resonance Imaging Osteoarthritis Knee Score at baseline and at 1-year and 2-year follow-ups. Generalized estimating equations were used to analyze the associations of baseline quadriceps strength with changes in effusion-synovitis and Hoffa-synovitis in multivariable analyses. Additionally, analyses were stratified by synovitis-driven inflammatory phenotypes. RESULTS: A total of 1513 knees were included in this study. In total, 61% of the subjects were female; subjects had an average age of 61.9 (SD 8.8) years and a mean BMI of 29.4 (SD 4.7). Regarding the whole population, baseline quadriceps strength was negatively associated with baseline effusion-synovitis and follow-up changes in effusion-synovitis (odds ratio [OR] 0.77-0.86), but no significant association was observed in terms of Hoffa-synovitis. Stratified by synovitis-driven inflammatory phenotype, baseline quadriceps strength was significantly associated with follow-up changes in effusion-synovitis-but not in Hoffa-synovitis-in the population with existing effusion-synovitis (OR 0.75-0.79). CONCLUSION: Higher baseline quadriceps strength was negatively associated with changes in effusion-synovitis-but not in Hoffa-synovitis-especially in the population with existing effusion-synovitis. Our findings suggested a potential protective role of the quadriceps in effusion-synovitis.
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| 13. |
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| 14. |
- Jia, Shi, et al.
(författare)
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Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications
- 2022
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Photonic generation of Terahertz (THz) carriers displays high potential for THz communications with a large tunable range and high modulation bandwidth. While many photonics-based THz generations have recently been demonstrated with discrete bulky components, their practical applications are significantly hindered by the large footprint and high energy consumption. Herein, we present an injection-locked heterodyne source based on generic foundry-fabricated photonic integrated circuits (PIC) attached to a uni-traveling carrier photodiode generating high-purity THz carriers. The generated THz carrier is tunable within the range of 0-1.4 THz, determined by the wavelength spacing between the two monolithically integrated distributed feedback (DFB) lasers. This scheme generates and transmits a 131 Gbits(-1) net rate signal over a 10.7-m distance with -24 dBm emitted power at 0.4 THz. This monolithic dual-DFB PIC-based THz generation approach is a significant step towards fully integrated, cost-effective, and energy-efficient THz transmitters. A photonic Terahertz source based on injection-locking an integrated dual-laser chip generates and transmits a 131 Gbps THz signal over 10.7-m distance, showing great potential towards fully integrated and energy-efficient THz transmitters for 6G.
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| 15. |
- Li, Hansen, et al.
(författare)
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The Effects of Green and Urban Walking in Different Time Frames on Physio-Psychological Responses of Middle-Aged and Older People in Chengdu, China
- 2020
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Nighttime walking is becoming a popular exercise for many middle-aged and older people in Asian countries. However, the health benefits of nighttime walking in urban areas and green spaces are still unclear. This study evaluated the physiological and psychological responses of 48 middle-aged and older people who walked 1.6 km through a green space and an urban area during daytime and nighttime. The Positive and Negative Affect Schedule (PANAS), Profile of Mood States (POMS), Perceived Restorativeness Scale (PRS), and Restorative Outcome Scale (ROS) were employed to measure the psychological responses, and pulse rate and blood pressure (SBP, DBP and MAP) were measured to evaluate the physiological responses. The results showed that the daytime green walking induced psychological improvements and lowered blood pressure (p < 0.05), while the daytime urban walking resulted in slight deterioration of all the measured parameters (p > 0.05). On the other hand, the nighttime green walking induced lowered blood pressure (p < 0.05), whilst the nighttime urban walking resulted in psychological improvements and lowered blood pressure (p < 0.05), and no significant difference was found in any measured parameter between the two nighttime walking groups. In conclusion, urban areas are noisy and irritating in the daytime, and not suitable for walking, but may become pleasurable and attractive at night. The psychological benefits of green walking may decrease at night, and nighttime walking in either an urban area or a green space may achieve similar health benefits. Therefore, we recommend that urban citizens start nighttime walking in a green space or an urban area to keep fit when the air is less polluted.
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| 16. |
- Ozolins, Oskars, et al.
(författare)
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300 Gbps Short-Reach C-Band Optical Links
- 2020
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Ingår i: 2020 22nd international conference on transparent optical networks (ICTON 2020). - : IEEE. - 2162-7339. - 9781728184234
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Konferensbidrag (refereegranskat)
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| 17. |
- Pang, Xiaodan, Dr., et al.
(författare)
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200 Gbps & x002F;Lane IM & x002F;DD Technologies for Short Reach Optical Interconnects
- 2020
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 38:2, s. 492-503
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Tidskriftsartikel (refereegranskat)abstract
- Client-side optics are facing an ever-increasing upgrading pace, driven by upcoming 5G related services and datacenter applications. The demand for a single lane data rate is soon approaching 200 Gbps. To meet such high-speed requirement, all segments of traditional intensity modulation direct detection (IM & x002F;DD) technologies are being challenged. The characteristics of electrical and optoelectronic components and the performance of modulation, coding, and digital signal processing (DSP) techniques are being stretched to their limits. In this context, we witnessed technological breakthroughs in several aspects, including development of broadband devices, novel modulation formats and coding, and high-performance DSP algorithms for the past few years. A great momentum has been accumulated to overcome the aforementioned challenges. In this article, we focus on IM & x002F;DD transmissions, and provide an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond. Our recent demonstrations of 200 Gbps short-reach transmissions with 4-level pulse amplitude modulation (PAM) and discrete multitone signals are also presented as examples to show the system requirements in terms of device characteristics and DSP performance. Apart from digital coherent technologies and advanced direct detection systems, such as Stokes-vector and Kramers-Kronig schemes, we expect high-speed IM & x002F;DD systems will remain advantageous in terms of system cost, power consumption, and footprint for short reach applications in the short- to mid- term perspective.
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| 18. |
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| 19. |
- Qu, Yanhua, 1974-, et al.
(författare)
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Genetic responses to seasonalvariation in altitudinal stress: whole-genome resequencing ofgreat tit in eastern Himalayas
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Species that undertake altitudinal migrations are exposed to a considerable seasonal variationin oxygen levels and temperature. How they cope with this was studied in a population of greattit (Parus major) that breeds at high elevations and winters at lower elevations in the easternHimalayas. Comparison of population genomics of high altitudinal great tits and those living inlowlands revealed an accelerated genetic selection for carbohydrate energy metabolism (aminosugar, nucleotide sugar metabolism and insulin signaling pathways) and hypoxia response (PI3K-akt,mTOR and MAPK signaling pathways) in the high altitudinal population. The PI3K-akt, mTOR andMAPK pathways modulate the hypoxia-inducible factors, HIF-1α and VEGF protein expression thusindirectly regulate hypoxia induced angiogenesis, erythropoiesis and vasodilatation. The strategiesobserved in high altitudinal great tits differ from those described in a closely related species onthe Tibetan Plateau, the sedentary ground tit (Parus humilis). This species has enhanced selectionin lipid-specific metabolic pathways and hypoxia-inducible factor pathway (HIF-1). Comparativepopulation genomics also revealed selection for larger body size in high altitudinal great tits.
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| 20. |
- Udalcovs, Aleksejs, et al.
(författare)
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Towards 25+Gbpsλ IM-DD PON : NRZ, duobinary, PAM4, and DMT transmission and optical budget comparison
- 2019
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Ingår i: International Conference on Transparent Optical Networks. - : IEEE Computer Society. - 9781728127798
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Konferensbidrag (refereegranskat)abstract
- While infrastructure providers are expanding their portfolio to offer a sustainable solution for beyond 10 Gbps in optical access network segment, we compare experimentally several alternatives that may be used in future passive optical networks (PONs) to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM-DD) systems employing the following modulation formats: (i) duobinary, (ii) 4-level pulse amplitude modulation (PAM4), and (iii) discrete multitone (DMT), which are all more bandwidth efficient than the non-return-to-zero (NRZ) in current 10G PON solutions. In this paper, we focus on the optical budget after transmission over a 20 km single-mode fiber (SMF) link in C-band and discuss the intrinsic imperfections of optical components that may significantly reduce the received signal quality.
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| 21. |
- Wang, Hong, et al.
(författare)
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Polymer-Derived Heteroatom-Doped Porous Carbon Materials
- 2020
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Ingår i: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 120:17, s. 9363-9419
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Forskningsöversikt (refereegranskat)abstract
- Heteroatom-doped porous carbon materials (HPCMs) have found extensive applications in adsorption/separation, organic catalysis, sensing, and energy conversion/storage. The judicious choice of carbon precursors is crucial for the manufacture of HPCMs with specific usages and maximization of their functions. In this regard, polymers as precursors have demonstrated great promise because of their versatile molecular and nanoscale structures, modulatable chemical composition, and rich processing techniques to generate textures that, in combination with proper solid-state chemistry, can be maintained throughout carbonization. This Review comprehensively surveys the progress in polymer-derived functional HPCMs in terms of how to produce and control their porosities, heteroatom doping effects, and morphologies and their related use. First, we summarize and discuss synthetic approaches, including hard and soft templating methods as well as direct synthesis strategies employing polymers to control the pores and/or heteroatoms in HPCMs. Second, we summarize the heteroatom doping effects on the thermal stability, electronic and optical properties, and surface chemistry of HPCMs. Specifically, the heteroatom doping effect, which involves both single-type heteroatom doping and codoping of two or more types of heteroatoms into the carbon network, is discussed. Considering the significance of the morphologies of HPCMs in their application spectrum, potential choices of suitable polymeric precursors and strategies to precisely regulate the morphologies of HPCMs are presented. Finally, we provide our perspective on how to predefine the structures of HPCMs by using polymers to realize their potential applications in the current fields of energy generation/conversion and environmental remediation. We believe that these analyses and deductions are valuable for a systematic understanding of polymer-derived carbon materials and will serve as a source of inspiration for the design of future HPCMs.
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| 22. |
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| 23. |
- Zhang, Lu, et al.
(författare)
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Digital mobile fronthaul employing differential pulse code modulation with suppressed quantization noise
- 2017
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:25, s. 31921-31936
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Tidskriftsartikel (refereegranskat)abstract
- A differential pulse code modulation (DPCM) based digital mobile fronthaul architecture is proposed and experimentally demonstrated. By using a linear predictor in the DPCM encoding process, the quantization noise can be effectively suppressed and a prediction gain of 7~8 dB can be obtained. Experimental validation is carried out with a 20 km 15-Gbaud/λ 4-level pulse amplitude modulation (PAM4) intensity modulation and direct detection system. The results verify the feasibility of supporting 163, 122, 98, 81 20-MHz 4, 16, 64, 256 QAM based antenna-carrier (AxC) containers with only 3, 4, 5, 6 quantization bits at a sampling rate of 30.72MSa/s in LTE-A environment. Further increasing the number of quantization bits to 8 and 9, 1024 quadrature amplitude modulation (1024 QAM) and 4096 QAM transmission can be realized with error vector magnitude (EVM) lower than 1% and 0.5%, respectively. The supported number of AxCs in the proposed DPCM-based fronthaul is increased and the EVM is greatly reduced compared to the common public radio interface (CPRI) based fronthaul that uses pulse code modulation. Besides, the DPCM-based fronthaul is also experimentally demonstrated to support universal filtered multicarrier signal that is one candidate waveform for the 5th generation mobile systems.
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| 24. |
- Zhang, Lu, et al.
(författare)
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Digital Radio-Over-Multicore-Fiber System with Self-Homodyne Coherent Detection and Entropy Coding for Mobile Fronthaul
- 2018
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Ingår i: European Conference on Optical Communication, ECOC. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrate a 28-Gbaud 16-QAM self-homodyne digital radio-over-33.6km-7-core-fiber system with entropy coding for mobile fronthaul, achieving error-free carrier aggregation of 330 100-MHz 4096-QAM 5G-new-radio channels and 921 100-MHz QPSK 5G-new-radio channels with CPRI-equivalent data rate up to 3.73-Tbit/s.
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| 25. |
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| 26. |
- Zhang, Lu, et al.
(författare)
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Fixed and Mobile Convergence with Stacked Modulation
- 2018
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Ingår i: 22ND INTERNATIONAL CONFERENCE ON OPTICAL NETWORK DESIGN AND MODELING (ONDM 2018). - : IEEE. ; , s. 36-40
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Konferensbidrag (refereegranskat)abstract
- We propose a stacked modulation mechanism to realize the transmission convergence of fixed broadband and wireless access networks. As an integrated solution, the direct current biased analog signal for wireless data is multiplied by the digital optical signal carrying fixed broadband service, where the low-speed analog signal becomes an envelope of the high-speed digital signal. At the receiver, the analog signal is firstly recovered with the image edge detection algorithm, after which the digital signal is recovered with the least-square algorithm. This scheme can realize fixed and mobile convergence with a single wavelength, which reduces the access network cost in terms of number of transceivers. Besides, the link capacity and spectrum efficiency are also improved. Moreover, this method is compatible with the existing access networks since the transceivers can be adopted to the scenario by turning off the unused modules. Simulation results show that in case of intensity modulation direct detection system sensitivity, penalty of only 1 similar to 2 dB can be obtained for the 10Gbps/lambda passive optical network when broadband access services are favored. Meanwhile, the wireless service needs more power than the broadband service to achieve the QoT requirements, and it has a higher penalty (similar to 5 dB) compared with broadband access services.
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| 27. |
- Zhang, Lu, et al.
(författare)
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K-means Clustering based Multi-Dimensional Quantization Scheme for Digital Mobile Fronthaul
- 2018
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Ingår i: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781943580385
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Konferensbidrag (refereegranskat)abstract
- We propose to group highly-correlated neighboring samples into multi-dimensional vectors and adopt k-means clustering for quantization in mobile fronthaul. 30-Gbit/s transmissions have been experimentally demonstrated for up to 40 100MHz LTE channels over 20km fiber.
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| 28. |
- Zhang, Lu, et al.
(författare)
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Kernel affine projection for compensating nonlinear impairments in optical direct detection systems
- 2019
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Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2019:CP765
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Konferensbidrag (refereegranskat)abstract
- We propose a novel kernel affine projection (KAP) algorithm, which combines kernel mapping and affine projection for channel equalization in optical direct detection systems. Experimental results show that the KAP algorithm can mitigate nonlinear impairments in short-reach communications while maintaining low computational complexity.
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| 29. |
- Zhang, Lu, et al.
(författare)
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Kernel Affine Projection for Nonlinearity Tolerant Optical Short Reach Systems
- 2020
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Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 68:10, s. 6403-6412
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinearity is one of the key issues that hinder the development of high-capacity optical short reach systems. This paper proposes three variants of kernel affine projection (KAP) algorithms, all of which combine kernel mapping and affine projection in a reproducing kernel Hilbert space for compensating nonlinear impairments in optical short reach systems. An intensity modulation/direct detection system with a single digital-to-analogue converter, a packaged externally modulated laser and a packaged InP photo-detector is used for experimental demonstration, achieving 238-Gbps (net rate 222-Gbps). Experimental results show that the KAP algorithms can mitigate nonlinear impairments in short-reach communications while maintaining low complexity in reproducing kernel Hilbert space.
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| 30. |
- Zhang, Lu, et al.
(författare)
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Kernel mapping for mitigating nonlinear impairments in optical short-reach communications
- 2019
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Ingår i: Optics Express. - : OSA - The Optical Society. - 1094-4087. ; 27:21, s. 29567-29580
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear impairments induced by the opto-electronic components are one of the fundamental performance-limiting factors in high-speed optical short-reach communications, significantly hindering capacity improvement. This paper proposes to employ a kernel mapping function to map the signals in a Hilbert space to its inner product in a reproducing kernel Hilbert space, which has been successfully demonstrated to mitigate nonlinear impairments in optical short-reach communication systems. The operation principle is derived. An intensity modulation/direct detection system with 1.5-µm vertical cavity surface emitting laser and 10-km 7-core fiber achieving 540.68-Gbps (net-rate 505.31-Gbps) has been carried out. The experimental results reveal that the kernel mapping based schemes are able to realize comparable transmission performance as the Volterra filtering scheme even with a high order.
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| 31. |
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| 32. |
- Zhang, Lu, et al.
(författare)
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Nonlinearity Tolerant High-speed DMT Transmission with 1.5-μm Single-mode VCSEL and Multi-core Fibers for Optical Interconnects
- 2019
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Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 37:2, s. 380-388
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the generation of 107-Gbit/s net-rate optical discrete multitone (DMT) signal using a 1.5-μm single-mode vertical cavity surface emitting laser (VCSEL) with modulation bandwidth of 22-GHz. Utilizing a nonlinearity-tolerant channel equalization algorithm for digital signal processing (DSP), total net-rates of 726.6-Gbit/s over 2.5-km dispersion-uncompensated 7-core fiber and 533.1-Gbit/s over 10-km dispersion-compensated 7-core fiber below 7% overhead hard-decision forward error correction (HD-FEC) limit have been experimentally achieved with a 1.5-μm VCSEL based intensity-modulation direct-detection (IM/DD) system. The features of the 1.5-μm single-mode VCSEL, 2.5-km/10km multi-core fibers and fan-in/fan-out modules are presented. Besides, the Volterra series based nonlinearity-tolerant channel equalization algorithm, which improves the signal-to-noise ratio (SNR) with more than 5-dB, is mathematically described and experimentally validated. The results have demonstrated that 1.5-μm single-mode VCSEL and multi-core fiber based transmission can be a promising candidate to solve the capacity challenges in short-reach optical interconnects.
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| 33. |
- Zhang, Lu, et al.
(författare)
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Spectrally efficient digitized radio-over-fiber system with k-means clustering-based multidimensional quantization
- 2018
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 43:7, s. 1546-1549
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Tidskriftsartikel (refereegranskat)abstract
- We propose a spectrally efficient digitized radio-over-fiber (D-RoF) system by grouping highly correlated neighboring samples of the analog signals into multidimensional vectors, where the k-means clustering algorithm is adopted for adaptive quantization. A 30 Gbit/s D-RoF system is experimentally demonstrated to validate the proposed scheme, reporting a carrier aggregation of up to 40 100 MHz orthogonal frequency division multiplexing (OFDM) channels with quadrate amplitude modulation (QAM) order of 4 and an aggregation of 10 100 MHz OFDM channels with a QAM order of 16384. The equivalent common public radio interface rates from 37 to 150 Gbit/s are supported. Besides, the error vector magnitude (EVM) of 8% is achieved with the number of quantization bits of 4, and the EVM can be further reduced to 1% by increasing the number of quantization bits to 7. Compared with conventional pulse coding modulation-based D-RoF systems, the proposed D-RoF system improves the signal-to-noise-ratio up to similar to 9 dB and greatly reduces the EVM, given the same number of quantization bits. (c) 2018 Optical Society of America
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| 34. |
- Zhang, Lu, et al.
(författare)
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Toward terabit digital radio over fiber systems : Architecture and key technologies
- 2019
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Ingår i: IEEE Communications Magazine. - : Institute of Electrical and Electronics Engineers Inc.. - 0163-6804 .- 1558-1896. ; 57:4, s. 131-137
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Tidskriftsartikel (refereegranskat)abstract
- To support massive deployment of broadband radio applications, such as 5G and high-definition videos for terrestrial televisions, large system capacity and high spectrum efficiency are highly demanded in radio over fiber (RoF) systems. In this article, we propose a terabit digital RoF system capable of providing high-speed transmission, where multicore fiber (MCF) is introduced for the access segment between the central unit and remote unit. Two key technologies that greatly enhance system capacity and spectrum efficiency, namely MCF enabled self-homodyne detection and compressed quantization, are demonstrated.
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| 35. |
- Zuntini, Alexandre R., et al.
(författare)
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Phylogenomics and the rise of the angiosperms
- 2024
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Ingår i: NATURE. - 0028-0836 .- 1476-4687. ; 629, s. 843-850
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Tidskriftsartikel (refereegranskat)abstract
- Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods(1,2). A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome(3,4). Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins(5-7). However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes(8). This 15-fold increase in genus-level sampling relative to comparable nuclear studies(9) provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade.
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