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| 2. |
- Álvarez-Muñiz, Jaime, et al.
(författare)
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The Giant Radio Array for Neutrino Detection (GRAND) : Science and design
- 2020
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Ingår i: Science China Physics, Mechanics & Astronomy. - : Springer Science and Business Media LLC. - 1674-7348 .- 1869-1927. ; 63:1
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Forskningsöversikt (refereegranskat)abstract
- The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 108 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10000 radio antennas deployed over 10000 km(2). A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.
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| 3. |
- Sun, Xiaoming, et al.
(författare)
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Adjustable hardness of hydrogel for promoting vascularization and maintaining sternness of stem cells in skin flap regeneration
- 2018
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Ingår i: Applied Materials Today. - : Elsevier. - 2352-9407. ; 13, s. 54-63
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Tidskriftsartikel (refereegranskat)abstract
- The matrix mechanical stiffness of biomaterials plays an important role in the pluripotency and biological function of stem cells in the microenvironment. It is a key step to adjust the stiffness of biomaterials for inducing stem cells to promote vascularization in order to promote damaged tissue repair. In this study, we transplant adipose derived stem cells (ADSCs) within an in situ forming dextran hydrogel with controllable mechanical strength formed by cross-linking glycidyl methacrylate derivatized dextran and dithiothreitol, which can regulate the stemness and biological functions of stem cells. We show that softer dextran hydrogel can better maintain stemness markers expression of ADSCs, and significantly stimulate ADSCs to secrete angiogenic factors. The ADSCs-encapsulated hydrogel distinctly promote the skin flap survival compared to direct cell injection. Bioluminescence imaging analysis shows that in situ forming dextran hydrogel can improve cells retention, and postmortem analysis reveals that the transplanted ADSCs with hydrogel can promote vascularization. These results support the use of injectable dextran hydrogel for skin ischemia tissue regeneration. (C) 2018 Elsevier Ltd. All rights reserved.
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| 4. |
- Liu, Zhigang, et al.
(författare)
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Gut microbiota mediates intermittent-fasting alleviation of diabetes-induced cognitive impairment
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1, s. 855-
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Tidskriftsartikel (refereegranskat)abstract
- Cognitive decline is one of the complications of type 2 diabetes (T2D). Intermittent fasting (IF) is a promising dietary intervention for alleviating T2D symptoms, but its protective effect on diabetes-driven cognitive dysfunction remains elusive. Here, we find that a 28-day IF regimen for diabetic mice improves behavioral impairment via a microbiota-metabolites-brain axis: IF enhances mitochondrial biogenesis and energy metabolism gene expression in hippocampus, re-structures the gut microbiota, and improves microbial metabolites that are related to cognitive function. Moreover, strong connections are observed between IF affected genes, microbiota and metabolites, as assessed by integrative modelling. Removing gut microbiota with antibiotics partly abolishes the neuroprotective effects of IF. Administration of 3-indolepropionic acid, serotonin, short chain fatty acids or tauroursodeoxycholic acid shows a similar effect to IF in terms of improving cognitive function. Together, our study purports the microbiota-metabolites-brain axis as a mechanism that can enable therapeutic strategies against metabolism-implicated cognitive pathophysiologies.
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| 5. |
- Xiong, Shaobing, et al.
(författare)
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Reducing nonradiative recombination for highly efficient inverted perovskite solar cells via a synergistic bimolecular interface
- 2024
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Reducing interface nonradiative recombination is important for realizing highly efficient perovskite solar cells. In this work, we develop a synergistic bimolecular interlayer (SBI) strategy via 4-methoxyphenylphosphonic acid (MPA) and 2-phenylethylammonium iodide (PEAI) to functionalize the perovskite interface. MPA induces an in-situ chemical reaction at the perovskite surface via forming strong P-O-Pb covalent bonds that diminish the surface defect density and upshift the surface Fermi level. PEAI further creates an additional negative surface dipole so that a more n-type perovskite surface is constructed, which enhances electron extraction at the top interface. With this cooperative surface treatment, we greatly minimize interface nonradiative recombination through both enhanced defect passivation and improved energetics. The resulting p-i-n device achieves a stabilized power conversion efficiency of 25.53% and one of the smallest nonradiative recombination induced Voc loss of only 59 mV reported to date. We also obtain a certified efficiency of 25.05%. This work sheds light on the synergistic interface engineering for further improvement of perovskite solar cells. Reducing interface nonradiative recombination is important for realizing highly efficient perovskite solar cells. Here, the authors employ a bimolecular interlayer to functionalize the perovskite interface, achieving cooperative surface treatment and certified power conversion efficiency of 25.05%.
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| 6. |
- Zhang, Guoqing, et al.
(författare)
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Extensive and drastically different alpine lake changes on Asia's high plateaus during the past four decades
- 2017
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Ingår i: Geophysical Research Letters. - 0094-8276. ; 44:1, s. 252-260
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Tidskriftsartikel (refereegranskat)abstract
- Asia's high plateaus are sensitive to climate change and have been experiencing rapid warming over the past few decades. We found 99 new lakes and extensive lake expansion on the Tibetan Plateau during the last four decades, 1970–2013, due to increased precipitation and cryospheric contributions to its water balance. This contrasts with disappearing lakes and drastic shrinkage of lake areas on the adjacent Mongolian Plateau: 208 lakes disappeared and 75% of the remaining lakes have shrunk. We detected a statistically significant coincidental timing of lake area changes in both plateaus, associated with the climate regime shift that occurred during 1997/1998. This distinct change in 1997/1998 is thought to be driven by large-scale atmospheric circulation changes in response to climate warming. Our findings reveal that these two adjacent plateaus have been changing in opposite directions in response to climate change. These findings shed light on the complex role of the regional climate and water cycles, and provide useful information for ecological and water resource planning in these fragile landscapes.
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| 7. |
- Zhang, Zhisen, et al.
(författare)
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Effects of Graphene Nanopore Geometry on DNA Sequencing
- 2014
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 5:9, s. 1602-1607
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter we assess the effect of graphene nanopore geometries on DNA sequencing by considering DNA fragments including A, T, C, G, and 5-methylcytosine (MC) pulled out of graphene nanopores of different geometries with diameters down to similar to 1 nm. Using steered molecular dynamics simulations it is demonstrated that the bases (A, T, C, G, and MC) can be indentified at single-base resolution through the characteristic peaks on the force profile in a circular graphene nanopore but not in nanopores with other asymmetric geometries. Our study suggests that the graphene nanopore surface should be modified as symmetrically as possible in order to sequence DNA by atomic force microscopy or optical tweezers.
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| 8. |
- Zhou, Wencai, et al.
(författare)
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The Role of Grain Boundaries on Ion Migration and Charge Recombination in Halide Perovskites
- 2024
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Ingår i: Small. - : WILEY-V C H VERLAG GMBH. - 1613-6810 .- 1613-6829.
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Tidskriftsartikel (refereegranskat)abstract
- Grain boundaries (GBs) have a significant role in polycrystalline perovskite solar cells (PSCs). However, there is ongoing debate regarding the impact of GBs on the performance and long-term stability of PSCs. Employing the first-principles molecular dynamics for perovskites, the iodine vacancy defect migrations both in bulk and at GBs are investigated. i) The positive iodine vacancy (VI+) is found that have both lower formation energy (1.4 eV) and activation energy (0.18 eV) than those of neutral iodine vacancy (VI), statistically. It indicated the VI+ acts as the dominant migrated iodine vacancy rather than VI; ii) the iodine vacancy at GBs has approximate to 0.48 eV higher activation energy than those in bulk, which leads to the accumulation of iodine vacancy at GBs; iii) the presence of VI+ result in a 3-fold increase in charge recombination ratio at GBs, compared to pristine PSCs. Based on quantum molecular dynamics statistical results, which are consistent with experimental measurements, insights into iodine vacancy migration both at GBs and in the bulk are gained. This understanding can be valuable for defects engineering related to ion migration, in order to improve the long-term stability and promote the performance of PSCs. Understanding defects engineering related to ion migration is crucial for enhancing the long-term stability and performance of hybrid perovskite solar cells. Iodine vacancies accumulate at grain boundaries due to lower formation energy and higher migration potential barrier compared to those in the bulk, which further increase the nonradiative recombination. image
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| 9. |
- Ahmad, Mohd Riduan, et al.
(författare)
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Emission Heights of Narrow Bipolar Events in a Tropical Storm over the Malacca Strait
- 2017
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Ingår i: 2017 International Conference On Electrical Engineering And Computer Science (Icecos). - : IEEE. - 9781479976751 - 9781479976768 - 9781479976744 ; , s. 305-309
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Konferensbidrag (refereegranskat)abstract
- Emission heights for narrow bipolar events (NBEs) have been reported mostly from observations at mid latitudes but none have been reported from tropical regions. In this paper, we are reporting for the first time the heights of NBE emissions from a tropical storm over the Malacca Strait, a narrow water passage between the Malay Peninsula and Sumatra Island. A total of 49 positive NBEs (+NBEs) were detected from the storm. The NBE activity can be divided into two stages according to the emission heights and radar reflectivity data. The first stage (or S1) lasted for only 6 minutes, started with the first detected NBE, and produced 20 NBEs (41%). The emission heights ranged between 12.0 and 16.7 km. Radar reflectivity data showed that the storm reached maximum values at 55 dBZ within the period S1. In contrast, the second stage (S2) lasted longer (32 minutes) and produced 29 NBEs (59%). The emission heights were lower and ranged from 8.5 to 13.7 km. Radar reflectivity data showed that the storm reached maximum values at 50 dBZ within the period S2.
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| 10. |
- Baharin, Shamsul Ammar Shamsul, et al.
(författare)
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Microwave radiation associated with stepped leaders of negative cloud-to-ground flashes
- 2022
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Ingår i: Atmospheric research. - : Elsevier. - 0169-8095 .- 1873-2895. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, Very-High Frequency (VHF) and microwave radiation pulses associated with stepped leader pulses (conventional breakdown) are examined. A total of 100 stepped leader pulses (SLPs) with the associated 100 quiet periods (QPs) from ten negative cloud-to-ground (CG) flashes within the reversal distance (<8 km) have been analyzed. The QP is defined as the period between two SLPs when no electrical activity within the fast antenna sensor bandwidth was detected. The measurement system is made up of fast antenna (FA) and slow antenna (SA) sensors, a VHF sensor (60 MHz center frequency with 40 MHz bandwidth), and a microwave sensor (0.97 GHz center frequency with 20 MHz bandwidth). The waveforms were sampled at 2.5 GHz (400 ps). The total durations of the SLPs and QPs were 2.648 +/- 1.152 mu s and 2.708 +/- 1.670 mu s, respectively. All microwave and VHF radiation waveforms have been detected as clear individual oscillating pulses. The key finding is that the microwave radiation can be classified into three categories based on the total number of detected individual oscillating pulses during the QP. Two microwave pulses detected during the QP (Category 1) are suggested to be associated with the electron avalanche/corona process at the tip of an existing negative leader and a space stem. The VHF pulses associated with the microwave pulses are suggested to be emitted by propagating streamers. On the other hand, a single microwave pulse detected during the QP (Category 2) is suggested to be emitted by the electron avalanche/corona process of a space stem. The VHF pulses associated with the microwave pulse are suggested to be emitted by propagating streamers. In both categories, 70% of the microwave radiation pulses have been observed to precede VHF radiation pulses with an average lead time of 0.848 +/- 1.336 mu s. The head-on collision of a downward propagating negative streamer and an upward propagating positive streamer (from space stem) emitted significant microwave radiation. A new negative leader was formed when the head-on collision took place. The microwave radiation pulses emitted by the head-on collision process were observed to precede SLPs with an average lead time of 0.423 +/- 0.378 mu s. Around 80% of the microwave radiation pulses preceded VHF radiation pulses with average lead time of 0.540 +/- 0.596 mu s. Therefore, microwave and VHF radiation pulses are suggested to be emitted by different processes of the electrical breakdown mechanism. The microwave radiation is emitted by electron avalanche/corona/head-on collision while the VHF radiation is emitted by propagating streamers.
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