Aluminum nitride(AlN)is the promising substrates material for the epitaxial growth ofⅢ-nitrides devices,such as high-power,high-frequency electronic,deep ultraviolet optoelectronics and acoustic devices.However,it is...Aluminum nitride(AlN)is the promising substrates material for the epitaxial growth ofⅢ-nitrides devices,such as high-power,high-frequency electronic,deep ultraviolet optoelectronics and acoustic devices.However,it is rather difficult to obtain the high quality and crack-free thick AlN wafers because of the low surface migration of Al adatoms and the large thermal and lattice mismatches between the foreign substrates and AlN.In this work,the fabrication of AlN material by hydride vapor phase epitaxy(HVPE)was summarized and discussed.At last,the outlook of the production of AlN by HVPE was prospected.展开更多
Currently,the preparation of large-size and high-quality hexagonal boron nitride is still an urgent problem.In this study,we investigated the growth and diffusion of boron and nitrogen atoms on the sapphire/h-BN buffe...Currently,the preparation of large-size and high-quality hexagonal boron nitride is still an urgent problem.In this study,we investigated the growth and diffusion of boron and nitrogen atoms on the sapphire/h-BN buffer layer by first-principles calculations based on density functional theory.The surface of the single buffer layer provides several metastable adsorption sites for free B and N atoms due to exothermic reaction.The adsorption sites at the ideal growth point for B atoms have the lowest adsorption energy,but the N atoms are easily trapped by the N atoms on the surface to form N-N bonds.With the increasing buffer layers,the adsorption process of free atoms on the surface changes from exothermic to endothermic.The diffusion rate of B atoms is much higher than that of the N atoms thus the B atoms play a major role in the formation of B-N bonds.The introduction of buffer layers can effectively shield the negative effect of sapphire on the formation of B-N bonds.This makes the crystal growth on the buffer layer tends to two-dimensional growth,beneficial to the uniform distribution of B and N atoms.These findings provide an effective reference for the h-BN growth.展开更多
Objective: To study the relationship between 14-3-3 sigma gene promoter hypermethylation and its transcrip-tion levels in sporadic breast carcinogenesis. Methods: Hypermethylation of 14-3-3 sigma gene was detected by ...Objective: To study the relationship between 14-3-3 sigma gene promoter hypermethylation and its transcrip-tion levels in sporadic breast carcinogenesis. Methods: Hypermethylation of 14-3-3 sigma gene was detected by sensitive MSP assay in carcinous, non-cancerious and normal tissue, and its mRNA was also detected by real-time PCR based on SYBR Green 1. Results: The hypermethylation frequencies of 14-3-3 sigma were 90% in 68 cases of sporadic breast cancer patients. Hypermethylation was presented in portions (2/13,18%) of hyperplastic samples, and no hypermethylation was presented in normal tissue. The hypermethylation change of 14-3-3 sigma gene was markedly related with various types, grades and lymph node metastases (P < 0.05), and no significant differences in methylation frequencies were seen between premenopause and postmenopause (P > 0.05). The hypermethylation of 14-3-3 sigma showed reverse relationship with its mRNA transcription (P < 0.05). Only lymph node metastases was strongly associated with poor outcome (P = 0.02). Whether 14-3-3 sigma promoter methylation or not did not affect the 5-year survival rate of sporadic breast cancer (P > 0.05). Conclu-sion: Epigenetics alterations of the 14-3-3 sigma can contribute to reducing or losing the expression of 14-3-3 sigma protein, which plays an important role in the development of sporadic breast carcinomas including various types, grades and lymph node metastases.展开更多
During the past 3000 years,cattle on the Qinghai-Xizang Plateau have developed adaptive phenotypes under the selective pressure of hypoxia,ultraviolet(UV)radiation,and extreme cold.The genetic mechanism underlying thi...During the past 3000 years,cattle on the Qinghai-Xizang Plateau have developed adaptive phenotypes under the selective pressure of hypoxia,ultraviolet(UV)radiation,and extreme cold.The genetic mechanism underlying this rapid adaptation is not yet well understood.Here,we present whole-genome resequencing data for 258 cattle from 32 cattle breeds/populations,including 89 Tibetan cattle representing eight populations distributed at altitudes ranging from 3400 m to 4300 m.Our genomic analysis revealed that Tibetan cattle exhibited a continuous phylogeographic cline from the East Asian taurine to the South Asian indicine ancestries.We found that recently selected genes in Tibetan cattle were related to body size(HMGA2 and NCAPG)and energy expenditure(DUOXA2).We identified signals of sympatric introgression from yak into Tibetan cattle at different altitudes,covering 0.64%–3.26%of their genomes,which included introgressed genes responsible for hypoxia response(EGLN1),cold adaptation(LRP11),DNA damage repair(LATS1),and UV radiation resistance(GNPAT).We observed that introgressed yak alleles were associated with noncoding variants,including those in present EGLN1.In Tibetan cattle,three yak introgressed SNPs in the EGLN1 promoter region reduced the expression of EGLN1,suggesting that these genomic variants enhance hypoxia tolerance.Taken together,our results indicated complex adaptation processes in Tibetan cattle,where recently selected genes and introgressed yak alleles jointly facilitated rapid adaptation to high-altitude environments.展开更多
It remains an urgent task to develop alternative hole-transporting layer(HTL)materials beyond commonly used PEDOT:PSS to increase the shelf-life of organic solar cells(OSCs).Inorganic metal oxide type materials,such a...It remains an urgent task to develop alternative hole-transporting layer(HTL)materials beyond commonly used PEDOT:PSS to increase the shelf-life of organic solar cells(OSCs).Inorganic metal oxide type materials,such as NiO_(x),CoO_(x)and VO_(x),with suitable work functions have attracted numerous research attention recently.In this work,more abundant and easily accessible oxygenated salt,vanadyl sulfate(VOSO_(4))has been demonstrated to be excellent choice as HTL for OSCs.The VOSO_(4)-based HTL can be readily processed by spin-coating from the precursor solution with subsequent thermal annealing and UVO treatment.As a consequence,a high power conversion efficiency(PCE)of 18.72%can be achieved for PM8:L8-BO based OSCs with the VOSO_(4)-based HTL.High transmittance,smooth film surface,suitable energy level and high conductivity were revealed to contribute to the high OSC performance.More importantly,compared to device with PEDOT:PSS,VOSO_(4)-based OSCs exhibit improved stability when stored in the N_(2)filled glove box.After being stored for 600 h,VOSO_(4)-based device can retain 89%of its initial efficiency.Notably,VOSO_(4)can be used as general HTL in PM6:BTP-BO-4Cl and PM6:IT-4F based OSCs,yielding high PCEs of 17.87%and 13.85%,respectively.展开更多
The thermal stability of F ion-implanted isolated AlGaN/GaN heterostructures was investigated,with B ion-implanted isolation shown for comparison.The sheet resistance of as-implanted samples with F ions was lower than...The thermal stability of F ion-implanted isolated AlGaN/GaN heterostructures was investigated,with B ion-implanted isolation shown for comparison.The sheet resistance of as-implanted samples with F ions was lower than that with B ions due to enhanced hopping conduction.The leakage current for both implanted samples initially decreased and then increased with increases in post-annealing temperature,indicating a damage-induced isolation mechanism.Leakage reached a minimum value after 400~oC annealing,which was over 10～8times lower than the saturated current(I_(sat))of the as-grown structure,suggesting a successful isolation.After relatively high-temperature annealing,the leakage for F implantation showed a small change,whereas that for B implantation showed significant increase,suggesting that F-implanted isolation exhibited excellent thermal stability.Leakage and F or B ion-implanted samples indicated that the leakage current originated from the region above the high-resistance GaN layer.Variation in E_arevealed that the optimal contributing states for conduction changed with operating temperature,annealing temperature,and ion species.展开更多
The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were betw...The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were between 800 and 950 ℃, the AlN-Ti/Al/Ni/Au contacts became ohmic contacts and the resistance decreased with the increase of annealing temperature. A lowest specific contacts resistance of 0.379 Ω·cm^2 was obtained for the sample annealed at 950 ℃. In this work, we confirmed that the formation mechanism of ohmic contacts on Al N was due to the formation of Al-Au, Au-Ti and Al-Ni alloys, and reduction of the specific contacts resistance could originate from the formation of Au2Ti and AlAu2 alloys. This result provided a possibility for the preparation of Al N-based high-frequency, high-power devices and deep ultraviolet devices.展开更多
基金partly supported by Beijing Municipal Natural Science Foundation (No. 4182046)the National Natural Science Foundation of China (No. 61874007)+3 种基金the Fundamental Research Funds for the Central Universities (Nos. buctrc201802, buctrc201830)the Funding for Bagui Talent of Guangxi province (Nos. T31200992001 and T3120097921)ASEAN Young Talented Scientist Program (No. Y312001913)Talent Model Base, China (No. AE31200065)
文摘Aluminum nitride(AlN)is the promising substrates material for the epitaxial growth ofⅢ-nitrides devices,such as high-power,high-frequency electronic,deep ultraviolet optoelectronics and acoustic devices.However,it is rather difficult to obtain the high quality and crack-free thick AlN wafers because of the low surface migration of Al adatoms and the large thermal and lattice mismatches between the foreign substrates and AlN.In this work,the fabrication of AlN material by hydride vapor phase epitaxy(HVPE)was summarized and discussed.At last,the outlook of the production of AlN by HVPE was prospected.
基金partly supported by the National Natural Science Foundation of China(61874007,12074028)the Beijing Municipal Natural Science Foundation(4182046)+2 种基金Shandong Provincial Major Scientific and Technological Innovation Project(2019JZZY010209)Key-area research and the development program of Guangdong Province(2020B010172001)the Fundamental Research Funds for the Central Universities(buctrc201802,buctrc201830,buctrc202127)。
文摘Currently,the preparation of large-size and high-quality hexagonal boron nitride is still an urgent problem.In this study,we investigated the growth and diffusion of boron and nitrogen atoms on the sapphire/h-BN buffer layer by first-principles calculations based on density functional theory.The surface of the single buffer layer provides several metastable adsorption sites for free B and N atoms due to exothermic reaction.The adsorption sites at the ideal growth point for B atoms have the lowest adsorption energy,but the N atoms are easily trapped by the N atoms on the surface to form N-N bonds.With the increasing buffer layers,the adsorption process of free atoms on the surface changes from exothermic to endothermic.The diffusion rate of B atoms is much higher than that of the N atoms thus the B atoms play a major role in the formation of B-N bonds.The introduction of buffer layers can effectively shield the negative effect of sapphire on the formation of B-N bonds.This makes the crystal growth on the buffer layer tends to two-dimensional growth,beneficial to the uniform distribution of B and N atoms.These findings provide an effective reference for the h-BN growth.
基金Supported by a grant from the Natural Sciences Foundation of Hubei Province (No. 2007ABA371).
文摘Objective: To study the relationship between 14-3-3 sigma gene promoter hypermethylation and its transcrip-tion levels in sporadic breast carcinogenesis. Methods: Hypermethylation of 14-3-3 sigma gene was detected by sensitive MSP assay in carcinous, non-cancerious and normal tissue, and its mRNA was also detected by real-time PCR based on SYBR Green 1. Results: The hypermethylation frequencies of 14-3-3 sigma were 90% in 68 cases of sporadic breast cancer patients. Hypermethylation was presented in portions (2/13,18%) of hyperplastic samples, and no hypermethylation was presented in normal tissue. The hypermethylation change of 14-3-3 sigma gene was markedly related with various types, grades and lymph node metastases (P < 0.05), and no significant differences in methylation frequencies were seen between premenopause and postmenopause (P > 0.05). The hypermethylation of 14-3-3 sigma showed reverse relationship with its mRNA transcription (P < 0.05). Only lymph node metastases was strongly associated with poor outcome (P = 0.02). Whether 14-3-3 sigma promoter methylation or not did not affect the 5-year survival rate of sporadic breast cancer (P > 0.05). Conclu-sion: Epigenetics alterations of the 14-3-3 sigma can contribute to reducing or losing the expression of 14-3-3 sigma protein, which plays an important role in the development of sporadic breast carcinomas including various types, grades and lymph node metastases.
基金supported by the National Key R&D Program of China(2021YFD1200400 and 2021YFF1001000)the National Natural Science Foundation of China(32102523,32372854,31861143014,32260823,and 32172706)+5 种基金the Key Research and Development Program of Xizang Autonomous Region of China(XZ202301ZY0008N)the Yunnan Expert Workstations(202305AF150156),the China Agriculture Research System of MOF and MARA(CARS-37)the Postdoctoral Fellowship Program of CPSF(GZC20232149)the Program of Yunling Scholar and Yunling Cattle Special Program of Yunnan Joint Laboratory of Seeds and Seeding Industry(202205AR070001)the Construction of Yunling Cattle Technology Innovation Center and Industrialization of Achievements(2019ZG007)Finally,we thank the High-Performance Computing(HPC)Center of Northwest A&F University(NWAFU)and Hefei Advanced Computing Center for providing computing resources.
文摘During the past 3000 years,cattle on the Qinghai-Xizang Plateau have developed adaptive phenotypes under the selective pressure of hypoxia,ultraviolet(UV)radiation,and extreme cold.The genetic mechanism underlying this rapid adaptation is not yet well understood.Here,we present whole-genome resequencing data for 258 cattle from 32 cattle breeds/populations,including 89 Tibetan cattle representing eight populations distributed at altitudes ranging from 3400 m to 4300 m.Our genomic analysis revealed that Tibetan cattle exhibited a continuous phylogeographic cline from the East Asian taurine to the South Asian indicine ancestries.We found that recently selected genes in Tibetan cattle were related to body size(HMGA2 and NCAPG)and energy expenditure(DUOXA2).We identified signals of sympatric introgression from yak into Tibetan cattle at different altitudes,covering 0.64%–3.26%of their genomes,which included introgressed genes responsible for hypoxia response(EGLN1),cold adaptation(LRP11),DNA damage repair(LATS1),and UV radiation resistance(GNPAT).We observed that introgressed yak alleles were associated with noncoding variants,including those in present EGLN1.In Tibetan cattle,three yak introgressed SNPs in the EGLN1 promoter region reduced the expression of EGLN1,suggesting that these genomic variants enhance hypoxia tolerance.Taken together,our results indicated complex adaptation processes in Tibetan cattle,where recently selected genes and introgressed yak alleles jointly facilitated rapid adaptation to high-altitude environments.
基金supported by NSFC(52163018,52073016,92163128)Jiangxi Provincial Department of Science and Technology(No.20212BCJ23035)+1 种基金Jiangxi Academy of Sciences(2023YJC1001,2023YSBG22025,2022YRCS002)the Hong Kong scholar program(XJ2022019)。
文摘It remains an urgent task to develop alternative hole-transporting layer(HTL)materials beyond commonly used PEDOT:PSS to increase the shelf-life of organic solar cells(OSCs).Inorganic metal oxide type materials,such as NiO_(x),CoO_(x)and VO_(x),with suitable work functions have attracted numerous research attention recently.In this work,more abundant and easily accessible oxygenated salt,vanadyl sulfate(VOSO_(4))has been demonstrated to be excellent choice as HTL for OSCs.The VOSO_(4)-based HTL can be readily processed by spin-coating from the precursor solution with subsequent thermal annealing and UVO treatment.As a consequence,a high power conversion efficiency(PCE)of 18.72%can be achieved for PM8:L8-BO based OSCs with the VOSO_(4)-based HTL.High transmittance,smooth film surface,suitable energy level and high conductivity were revealed to contribute to the high OSC performance.More importantly,compared to device with PEDOT:PSS,VOSO_(4)-based OSCs exhibit improved stability when stored in the N_(2)filled glove box.After being stored for 600 h,VOSO_(4)-based device can retain 89%of its initial efficiency.Notably,VOSO_(4)can be used as general HTL in PM6:BTP-BO-4Cl and PM6:IT-4F based OSCs,yielding high PCEs of 17.87%and 13.85%,respectively.
基金supported by the National Natural Science Foundation of China(61874007,12074028,and 52102152)Shandong Provincial Major Scientific and Technological Innovation Project(2019JZZY010209)+2 种基金the Key-area Research and Development Program of Guangdong Province(2020B010172001)the Fundamental Research Funds for the Central Universities(buctrc201802,buctrc201830,and buctrc202127)Beijing Outstanding Young Scientist Program(BJJWZYJH01201910010024)。
基金supported by the National Natural Science Foundation of China(Grant Nos.61504071,and 61474133)the Natural Science Foun-dation of Nantong University(Grant No.03081003)+1 种基金the Research Project of Beijing University of Chemical Technology(Grant Nos.buctrc201802,and YY1701)and the Natural Science Foundation of Beijing Municipal(Grant No.4182046)
文摘The thermal stability of F ion-implanted isolated AlGaN/GaN heterostructures was investigated,with B ion-implanted isolation shown for comparison.The sheet resistance of as-implanted samples with F ions was lower than that with B ions due to enhanced hopping conduction.The leakage current for both implanted samples initially decreased and then increased with increases in post-annealing temperature,indicating a damage-induced isolation mechanism.Leakage reached a minimum value after 400~oC annealing,which was over 10～8times lower than the saturated current(I_(sat))of the as-grown structure,suggesting a successful isolation.After relatively high-temperature annealing,the leakage for F implantation showed a small change,whereas that for B implantation showed significant increase,suggesting that F-implanted isolation exhibited excellent thermal stability.Leakage and F or B ion-implanted samples indicated that the leakage current originated from the region above the high-resistance GaN layer.Variation in E_arevealed that the optimal contributing states for conduction changed with operating temperature,annealing temperature,and ion species.
文摘The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were between 800 and 950 ℃, the AlN-Ti/Al/Ni/Au contacts became ohmic contacts and the resistance decreased with the increase of annealing temperature. A lowest specific contacts resistance of 0.379 Ω·cm^2 was obtained for the sample annealed at 950 ℃. In this work, we confirmed that the formation mechanism of ohmic contacts on Al N was due to the formation of Al-Au, Au-Ti and Al-Ni alloys, and reduction of the specific contacts resistance could originate from the formation of Au2Ti and AlAu2 alloys. This result provided a possibility for the preparation of Al N-based high-frequency, high-power devices and deep ultraviolet devices.
