A new measurement method for the spatial distribution of neutron beam flux in boron neutron capture therapy(BNCT)is being developed based on the two-dimensional Micromegas detector.To address the issue of long process...A new measurement method for the spatial distribution of neutron beam flux in boron neutron capture therapy(BNCT)is being developed based on the two-dimensional Micromegas detector.To address the issue of long processing times in traditional offline position reconstruction methods,this paper proposes a field programmable gate array based online position reconstruction method utilizing the micro-time projection chamber principle.This method encapsulates key technical aspects:a self-adaptive serial link technique built upon the dynamical adjustment of the delay chain length,fast sorting,a coordinate-matching technique based on the mapping between signal timestamps and random access memory(RAM)addresses,and a precise start point-merging technique utilizing a circular combined RAM.The performance test of the selfadaptive serial link shows that the bit error rate of the link is better than 10-12 at a confidence level of 99%,ensuring reliable data transmission.The experiment utilizing the readout electronics and Micromegas detector shows a spatial resolution of approximately 1.4 mm,surpassing the current method’s resolution level of 5 mm.The beam experiment confirms that the readout electronics system can obtain the flux spatial distribution of neutron beams online,thus validating the feasibility of the position reconstruction method.The online position reconstruction method avoids traditional methods,such as bubble sorting and traversal searching,simplifies the design of the logic firmware,and reduces the time complexity from O(n2)to O(n).This study contributes to the advancement in measuring neutron beam flux for BNCT.展开更多
Nondestructive and noninvasive neutron assays are essential applications of neutron techniques.Neutron resonance transmission analysis(NRTA)is a powerful nondestructive method for investigating the elemental compositi...Nondestructive and noninvasive neutron assays are essential applications of neutron techniques.Neutron resonance transmission analysis(NRTA)is a powerful nondestructive method for investigating the elemental composition of an object.The back-streaming neutron line(Back-n)is a newly built time-of-flight facility at the China Spallation Neutron Source(CSNS)that provides neutrons in the eV to 300 MeV range.A feasibility study of the NRTA method for nuclide identification was conducted at the CSNS Back-n via two test experiments.The results demonstrate that it is feasible to identify different elements and isotopes in samples using the NRTA method at Back-n.This study reveals its potential future applications.展开更多
Titanium matrix composites reinforced with ceramic particles are considered a promising engineering material due to their combination of high specific strength,low density,and high modulus.In this study,the TA15-based...Titanium matrix composites reinforced with ceramic particles are considered a promising engineering material due to their combination of high specific strength,low density,and high modulus.In this study,the TA15-based composites reinforced with a volume fraction of 10% to 25%(TiB+TiC)were prepared using powder metallurgy and casting technique.Microstructural characterization and phase constitution were examined using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray diffraction(XRD).In addition,the microhardness,room temperature(RT)and high temperature(HT)tensile properties of the composites were evaluated.Results revealed that the reinforcements are distributed uniformly even in the composites with a high volume of TiB and TiC.However,as the volume fraction exceeds 15%,TiB and TiC particles become coarsening and exhibit rod-like and dendritic-like morphology.Microhardness increases gradually from 321.2 HV for the base alloy to a maximum of 473.3 HV as the reinforcement increases to 25vol.%.Tensile test results indicate that a reinforcement volume fraction above 20% is beneficial for enhancing tensile strength and yield strength at high temperatures,but it has an adverse effect on room temperature elongation.Conversely,if the reinforcement volume fraction is below 20%,it can improve high-temperature elongation when the temperature exceeds 600℃.展开更多
The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types ...The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018.These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam.These gamma rays,commonly referred to as in-beam gamma rays,can induce a non-negligible experimental background in neutron-reaction measurements.Studying the characteristics of in-beam gamma rays is important for understanding the experimental background.However,measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons;thus,discriminating between neutron-induced signals and those from in-beam gamma rays is difficult.In this study,we propose the use of the black resonance filter method and a CeBr_(3) scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n.Four types of black resonance filters,^(181)Ta,^(59)Co,^(nat)Ag,and^(nat)Cd,were used in this measurement.The time-of-flight(TOF)technique was used to select the detector signals remaining in the absorption region of the TOF spectra,which were mainly induced by in-beam gamma rays.The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr_(3) scintillation detector and using Monte Carlo simulations.Based on the results of this study,the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated,which is beneficial for enhancing both the experimental methodology and data analysis.展开更多
The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurem...The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.展开更多
Taxonomic uncertainties of rare species often hinder effective prioritization for conservation.One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii.F.chienii was previously only known from the typ...Taxonomic uncertainties of rare species often hinder effective prioritization for conservation.One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii.F.chienii was previously only known from the type specimens collected in 1935 in Pingwu County of Sichuan Province,China,and has long been thought to be on the verge of extinction.However,morphological similarities to closely related Fagus species have led many to question the taxonomic status of F.chienii.To clarify this taxonomic uncertainty,we used the newly collected samples to reconstruct a molecular phylogeny of Chinese Fagus species against the phylogenetic backbone of the whole genus using seven nuclear genes.In addition,we examined nine morphological characters to determine whether F.chienii is morphologically distinct from its putatively closest relatives(F.hayatae,F.longipetiolata,and F.lucida).Both morphological and phylogenetic analyses indicated that F.chienii is conspecific with F.hayatae.We recommended that F.chienii should not be treated as a separate species in conservation management.However,conservation strategies such as in situ protection and ex situ germplasm preservation should be adopted to prevent the peculiar“F.chienii”population from extinction.展开更多
A Fourier transform spectrometer(FTS)has been used to observe solar activities due to its ultra-high spectral resolution.However,the FTS in-band spectra are usually distorted and some artifacts appear in out-of-band r...A Fourier transform spectrometer(FTS)has been used to observe solar activities due to its ultra-high spectral resolution.However,the FTS in-band spectra are usually distorted and some artifacts appear in out-of-band regions due to nonlinear effects.Therefore,the FTS nonlinear problem must be corrected.In this study,we proposed a novel method to correct the nonlinear effects using simulated annealing.We simulated several nonlinear spectra to evaluate the performance of our method.The calculated quadratic coefficients are extremely close to the given values,demonstrating that the method is effective and accurate.The proposed method is further used to correct the blackbody and solar spectra with nonlinearity obtained by Bruker IFS-125HR installed at the Huairou Solar Observing Station,which is a pathfinder for the accurate infrared magnetic field measurements of the Sun project.To the blackbody spectra,the nonlinearity in low-and high-frequency regions are corrected by 89.09%and 60.84%.The nonlinear correction of the solar spectra in the low-and high-frequency regions have reached 65.34%and 81.04%,respectively.These results prove that our method can correct the nonlinear problem to improve the data accuracy.展开更多
The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and composit...The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and compositions of the TA15 alloy and its composites were analyzed by XRD and EDS,and their electrochemical corrosion behaviors in the 3.5%NaCl solution were studied.Corrosion wear testing was conducted using a reciprocating ball-on-disc wear tester under a 10 N load.Results show that the in situ fibrous TiB phase and the granular TiC phase are uniformly distributed on the composite matrix.The microhardness can reach up to 531 HV as 25vol.%TiC+TiB reinforcement is added.Compared with the TA15 alloy,the volume wear rate decreases from(2.21±0.07)×10^(-4)to(1.75±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1)by adding 15vol.%TiC+TiB reinforcement,and the wear mechanism is adhesive wear.When the volume percentage of the reinforcement phase reaches 25%,the volume wear rate increases from(1.75±0.07)×10^(-4)to(2.41±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1),and the wear mechanism changes into abrasive wear.The volume loss resulted by the interaction between corrosion and wear accounts for more than 27%of the total wear volume.The volume loss due to wear-induced corrosion changes from 1.94%to 4.06%with different additions of reinforcement.The volume loss caused by corrosion-induced wear initially increases from 24.08%to 26.90%as the reinforcement increases from 0 to 15%due to the increase of corrosion potential,and then decreases from 26.90%to 25.68%as the reinforcement increases from 15%to 25%due to the peeling of TiC phase.展开更多
The Full-disk Magneto Graph(FMG),a payload onboard the Advanced Space Solar Observatory(ASO-S),will measure the vector magnetic field in the photosphere.The instrument consists of a frontwindow filter,a telescope,an L...The Full-disk Magneto Graph(FMG),a payload onboard the Advanced Space Solar Observatory(ASO-S),will measure the vector magnetic field in the photosphere.The instrument consists of a frontwindow filter,a telescope,an LCVR polarimeter,an image-stabilization system,a seven-stage tunable Lyot filter,a CMOS camera with 4096×4096 pixels and a pair of calibration/focus wheels.In this paper,we describe the design of the FMG instrument and provide a summary of test observations carried out with the FMG prototype.展开更多
Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n w...Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n white neutron source),which was completed in March 2018.The Back-n neutron beam is very intense,at approximately 29107 n/cm2/s at 55 m from the target,and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices.In addition,the excellent energy spectrum spanning from 0.5 eV to 200 MeV,and a good time resolution related tothe time-of-flight measurements make it a typical white neutron source for nuclear data measurements;its overall performance is among that of the best white neutron sources in the world.Equipped with advanced spectrometers,detectors,and application utilities,the Back-n facility can serve wide applications,with a focus on neutron-induced cross-sectional measurements.This article presents an overview of the neutron beam characteristics,the experimental setups,and the ongoing applications at Backn.展开更多
AIM To explore the features and prognostic value of lymph node metastasis in patients with T1-stage colorectal cancer(CRC).METHODS In all,321 cases of T1-stage CRC were selected from 10132 patients with CRC who receiv...AIM To explore the features and prognostic value of lymph node metastasis in patients with T1-stage colorectal cancer(CRC).METHODS In all,321 cases of T1-stage CRC were selected from 10132 patients with CRC who received surgical therapy in six large-scale hospitals in China and were retrospectively analyzed. Univariate and multivariate analyses were performed to analyze the risk factors for lymphatic metastasis. A survival analysis was then performed to analyze the prognostic value of lymph node metastasis.RESULTS The occurrence rate of T1 stage was 3.17%(321/10132);of these patients,the lymph node metastasis rate was 8.41%(27/321),and the non-lymph node metastasis rate was 91.59%(294/321). Univariate analysis showed that preoperative serum CEA,preoperative serum CA199,preoperative serum CA724,vascular invasion,and degree of differentiation were associated with lymph node metastasis in T1-stage CRC(P < 0.05 for all). Multivariate analysis indicated that preoperative serum CA724,vascular invasion,and degree of differentiation were closely related to lymph node metastasis(P < 0.05 for all). Log-rank survival analysis showed that age,preoperative serum CEA,preoperative serum CA199,vascular invasion,degree of differentiation,and lymph node metastasis(χ2 = 24.180,P < 0.001) were predictors of 5-year overall survival(OS)(P < 0.05 for all). COX regression analysis demonstrated that preoperative serum CA199 and lymph node metastasis(HR = 5.117;P < 0.05;95%CI: 0.058-0.815) were independent prognostic indicators of 5-year OS in patients with T1-stage CRC(P < 0.05 for both). CONCLUSION The morbidity of T1-stage CRC was 3.17% for all CRC cases. Preoperative serum CA724,vascular invasion,and degree of differentiation are independent risk factors for lymph node metastasis. Lymph node metastasis is an independent prognostic factor for OS in patients with T1-stage CRC.展开更多
BACKGROUND Lymphovascular invasion (LVI) is suggested to be an early and important step in tumor progression toward metastasis, but its prognostic value and genetic mechanisms in colorectal cancer (CRC) have not been ...BACKGROUND Lymphovascular invasion (LVI) is suggested to be an early and important step in tumor progression toward metastasis, but its prognostic value and genetic mechanisms in colorectal cancer (CRC) have not been well investigated. AIM To investigate the prognostic value of LVI in CRC and identify the associated genomic alterations. METHODS We performed a retrospective analysis of 1219 CRC patients and evaluated the prognostic value of LVI for overall survival by the Kaplan-Meier method and multivariate Cox regression analysis. We also performed an array-based comparative genomic hybridization analysis of 47 fresh CRC samples to examine the genomic alterations associated with LVI. A decision tree model was applied to identify special DNA copy number alterations (DCNAs) for differentiating between CRCs with and without LVI. Functional enrichment and protein-protein interaction network analyses were conducted to explore the potential molecular mechanisms of LVI. RESULTS LVI was detected in 150 (12.3%) of 1219 CRCs, and the presence was positively associated with higher histological grade and advanced tumor stage (both P < 0.001). Compared with the non-LVI group, the LVI group showed a 1.77-fold (95% confidence interval: 1.40-2.25, P < 0.001) increased risk of death and a significantly lower 5-year overall survival rate (P < 0.001). Based on the comparative genomic hybridization data, 184 DCNAs (105 gains and 79 losses) were identified to be significantly related to LVI (P < 0.05), and the majority were located at 22q, 17q, 10q, and 6q. We further constructed a decision tree classifier including seven special DCNAs, which could distinguish CRCs with LVI from those without it at an accuracy of 95.7%. Functional enrichment and proteinprotein interaction network analyses revealed that the genomic alterations related to LVI were correlated with inflammation, epithelial-mesenchymal transition, angiogenesis, and matrix remodeling. CONCLUSION LVI is an independent predictor for survival in CRC, and its development may correlate with inflammation, epithelial-mesenchymal transition, angiogenesis, and matrix remodeling.展开更多
To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The m...To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The measurement is performed at the Back-n white neutron source with a 76-m time-of-flight path using the China Spallation Neutron Source. A multilayer fast fission chamber with 235U and 238U is employed as the neutron detector. The diameter and thickness of the natural graphite sample are 70 mm and 40 mm, respectively. Signal waveforms are collected using a data acquisition system. Off-line data processing was used to obtain the neutron time-of-flight spectra and transmissions. The uncertainty of the counting statistics is generally approximately 3% for each bin in the energy range of 1–20 MeV. It is determined that the results for the neutron total cross section of carbon obtained using ^235U cells are in good agreement with the results obtained using 238U cells within limits of statistical uncertainty. Moreover, the measured total cross sections show good agreement with the broadening evaluated data.展开更多
Casting technology of thin-wall TiAl alloy turbochargers was studied by investment casting and numerical simulation.Misruns and gas holes were the main defects observed in preliminary work due to the poor fluidity of ...Casting technology of thin-wall TiAl alloy turbochargers was studied by investment casting and numerical simulation.Misruns and gas holes were the main defects observed in preliminary work due to the poor fluidity of alloy,and to gas entrapment.In order to eliminate these defects,cast parameters,such as centrifugal rotation rate and mould preheating temperature,were optimized by numerical simulation,meanwhile,the structure of the shell mould was optimized to improve the filling capacity of TiAl alloy.Pouring experiments were carried out by vacuum induction melting furnace equipped with a water-cooled copper crucible based on the above optimization.The quality of the TiAl alloy casting was analyzed by fluorescent penetrant inspection and X-ray detection.The results show that a centrifugal rotation rate of 200 rpm,mould preheating temperature of 600°C,shell preparation through organic fiber addition can dramatically improve the mould filling capacity,and integrated turbochargers were finally prepared.展开更多
AIM： To study the relationship between particularly interesting new cysteine-histidine rich protein （PINCH） expression and clinicopathological factors in Chinese colorectal cancer patients. METHODS： The expression...AIM： To study the relationship between particularly interesting new cysteine-histidine rich protein （PINCH） expression and clinicopathological factors in Chinese colorectal cancer patients. METHODS： The expression of PINCH was examined by immumohistochemistry in 141 samples of primary colorectal adenocarcinoma and 92 normal samples of colorectal mucosa. Eighty of the cases had both primary tumour and normal mucosa from the same patients. RESULTS： PINCH was expressed in the stroma of normal mucosa and tumours. PINCH expression in tumourassociated stroma was increased compared to normal mucosa in both unmatched cases （n = 141, x^2 = 85.79, df = 3, P〈 0.0001） and matched cases （n =80, x^2= 45.86, df= 3, P〈 0.0001）. Among 135 tumours with visible invasive margin, 86 （64%） showed stronger PINCH expression at the invasive margin than in the intratumoural stroma. The frequency of PINCH strong expression in mucinous and signet-ring cell carcinomas was higher （52%） compared to non-mucinous carcinomas （29%, x^2=5.13, P= 0.02）. We did not find that PINCH expres- sion was related to patient＇s gender, age, tumour location, tumour size, gross status, histological type, differentiation, invasion depth, lymph node status and Dukes＇ stage （P 〉 0.05）.CONCLUSION： The expression of PINCH was upregulated in colorectal cancers, and especially at the margin of tumours, and further was related to mucinous and signet-ring cell carcinomas. The results suggest that expression of PINCH may be involved in the tumourigenesis and aggressiveness of colorectal cancers.展开更多
Objective To assese the healing of stoma after magnetic anastomosis for the reconstruction of biliary-enteric continuity under severe inflammation. Methods Acute bile duct injury was constructed as a bile peritonitis ...Objective To assese the healing of stoma after magnetic anastomosis for the reconstruction of biliary-enteric continuity under severe inflammation. Methods Acute bile duct injury was constructed as a bile peritonitis model in mongrel dogs(n=32). Magnetic anastomosis(group A, n=16) and traditional suture anastomosis(group B, n=16) were performed to reconstruct the biliary-enteric continuity in one stage. Half of the dogs in each group were euthanized on the 30 th postoperative day, and the other half on the 90 th postoperative day to harvest the stoma region. The healing conditions of the stoma after the 2 anastomotic approaches were observed with naked eyes, under light microscope and scanning electron microscope. Results The stoma leakage rate(50% versus 0% on the 30 th postoperative day, 37.5% versus 12.5% on the 90 th postoperative day, both P<0.05) and stenosis degree(13.9%±0.3% versus 7.1%±0.3% on the 30 th postoperative day, 17.2%±0.4% versus 9.4%±0.4% on the 90 th postoperative day, both P<0.01) were significantly higher in group B than in group A. Compared with traditional manual anastomoses, the histological analysis under light and electron microscope showed a more continuous stoma with more regular epithelium proliferation and collagen arrangement, less inflammation in group A. Conclusions Magnetic anastomosis stent ensures better healing of the stoma even under the circumstance of severe inflammation.展开更多
The limited molecular classifications and disease signatures of osteoarthritis(OA)impede the development of prediagnosis and targeted therapeutics for OA patients.To classify and understand the subtypes of OA,we colle...The limited molecular classifications and disease signatures of osteoarthritis(OA)impede the development of prediagnosis and targeted therapeutics for OA patients.To classify and understand the subtypes of OA,we collected three types of tissue including cartilage,subchondral bone,and synovium from multiple clinical centers and constructed an extensive transcriptome atlas of OA patients.By applying unsupervised clustering analysis to the cartilage transcriptome,OA patients were classified into four subtypes with distinct molecular signatures:a glycosaminoglycan metabolic disorder subtype(C1),a collagen metabolic disorder subtype(C2),an activated sensory neuron subtype(C3),and an inflammation subtype(C4).Through ligand-receptor crosstalk analysis of the three knee tissue types,we linked molecular functions with the clinical symptoms of different OA subtypes.For example,the Gene Ontology functional term of vasculature development was enriched in the subchondral bone-cartilage crosstalk of C2 and the cartilage-subchondral bone crosstalk of C4,which might lead to severe osteophytes in C2 patients and apparent joint space narrowing in C4 patients.Based on the marker genes of the four OA subtypes identified in this study,we modeled OA subtypes with two independent published RNA-seq datasets through random forest classification.The findings of this work contradicted traditional OA diagnosis by medical imaging and revealed distinct molecular subtypes in knee OA patients,which may allow for precise diagnosis and treatment of OA.展开更多
Sinomanglietia glauca is a critically endangered species described from Jiangxi Province in the 1990s. Recently two populations were discovered from Yongshun County of west Hunan Province, about 450 km away from those...Sinomanglietia glauca is a critically endangered species described from Jiangxi Province in the 1990s. Recently two populations were discovered from Yongshun County of west Hunan Province, about 450 km away from those in Jiangxi. Because of the new findings and the poor reproducibility inherent to RAPD and ISSR markers of previous studies, the population structure of this rare species was reanalyzed with chloroplast PCR-SSCP （single-stranded conformation polymorphism）, including all of four recorded populations. The results showed that two distinct haplotypes characterized Jiangxi and Hunan populations separately, with no genetic variation occurring within regions. We postulated that this surprising pattern might result from habitat fragmenta- tion and demographic bottlenecks during and/or after the Quaternary glaciation. On the basis of the pronounced genetic structure, two evolutionarily significant units （ESUs） were recommended for effective conservation of S. glauca.展开更多
基金supported by the National Natural Science Foundation of China(No.12075237)。
文摘A new measurement method for the spatial distribution of neutron beam flux in boron neutron capture therapy(BNCT)is being developed based on the two-dimensional Micromegas detector.To address the issue of long processing times in traditional offline position reconstruction methods,this paper proposes a field programmable gate array based online position reconstruction method utilizing the micro-time projection chamber principle.This method encapsulates key technical aspects:a self-adaptive serial link technique built upon the dynamical adjustment of the delay chain length,fast sorting,a coordinate-matching technique based on the mapping between signal timestamps and random access memory(RAM)addresses,and a precise start point-merging technique utilizing a circular combined RAM.The performance test of the selfadaptive serial link shows that the bit error rate of the link is better than 10-12 at a confidence level of 99%,ensuring reliable data transmission.The experiment utilizing the readout electronics and Micromegas detector shows a spatial resolution of approximately 1.4 mm,surpassing the current method’s resolution level of 5 mm.The beam experiment confirms that the readout electronics system can obtain the flux spatial distribution of neutron beams online,thus validating the feasibility of the position reconstruction method.The online position reconstruction method avoids traditional methods,such as bubble sorting and traversal searching,simplifies the design of the logic firmware,and reduces the time complexity from O(n2)to O(n).This study contributes to the advancement in measuring neutron beam flux for BNCT.
基金This work was supported by the National Natural Science Foundation of China(No.12035017)Youth Innovation Promotion Association CAS(No.2023014)Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515010360 and 2022B1515120032).
文摘Nondestructive and noninvasive neutron assays are essential applications of neutron techniques.Neutron resonance transmission analysis(NRTA)is a powerful nondestructive method for investigating the elemental composition of an object.The back-streaming neutron line(Back-n)is a newly built time-of-flight facility at the China Spallation Neutron Source(CSNS)that provides neutrons in the eV to 300 MeV range.A feasibility study of the NRTA method for nuclide identification was conducted at the CSNS Back-n via two test experiments.The results demonstrate that it is feasible to identify different elements and isotopes in samples using the NRTA method at Back-n.This study reveals its potential future applications.
基金financially supported by the National Key Research&Development Program of China(Nos.2020YFB2008300,2020YFB2008303)。
文摘Titanium matrix composites reinforced with ceramic particles are considered a promising engineering material due to their combination of high specific strength,low density,and high modulus.In this study,the TA15-based composites reinforced with a volume fraction of 10% to 25%(TiB+TiC)were prepared using powder metallurgy and casting technique.Microstructural characterization and phase constitution were examined using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray diffraction(XRD).In addition,the microhardness,room temperature(RT)and high temperature(HT)tensile properties of the composites were evaluated.Results revealed that the reinforcements are distributed uniformly even in the composites with a high volume of TiB and TiC.However,as the volume fraction exceeds 15%,TiB and TiC particles become coarsening and exhibit rod-like and dendritic-like morphology.Microhardness increases gradually from 321.2 HV for the base alloy to a maximum of 473.3 HV as the reinforcement increases to 25vol.%.Tensile test results indicate that a reinforcement volume fraction above 20% is beneficial for enhancing tensile strength and yield strength at high temperatures,but it has an adverse effect on room temperature elongation.Conversely,if the reinforcement volume fraction is below 20%,it can improve high-temperature elongation when the temperature exceeds 600℃.
基金supported by the Youth Talent Program of China National Nuclear Corporationthe Continuous-Support Basic Scientific Research Project(BJ010261223282)+1 种基金the National Natural Science Foundation of China(No.11790321)the Research and development project of China National Nuclear Corporation。
文摘The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018.These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam.These gamma rays,commonly referred to as in-beam gamma rays,can induce a non-negligible experimental background in neutron-reaction measurements.Studying the characteristics of in-beam gamma rays is important for understanding the experimental background.However,measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons;thus,discriminating between neutron-induced signals and those from in-beam gamma rays is difficult.In this study,we propose the use of the black resonance filter method and a CeBr_(3) scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n.Four types of black resonance filters,^(181)Ta,^(59)Co,^(nat)Ag,and^(nat)Cd,were used in this measurement.The time-of-flight(TOF)technique was used to select the detector signals remaining in the absorption region of the TOF spectra,which were mainly induced by in-beam gamma rays.The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr_(3) scintillation detector and using Monte Carlo simulations.Based on the results of this study,the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated,which is beneficial for enhancing both the experimental methodology and data analysis.
基金supported by the National Natural Science Foundation of China(Nos.11675155,11790321,and 12075216)the National Key Research and Development Plan(No.2016YFA0401603).
文摘The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.
基金supported by grants from the National Natural Science Foundation of China(No.31770236)the Guangxi Key Research and Development Projects(Guike AB21220057)Training Program for Academic and Technical Leaders(leading talents)in Major Disciplines of Jiangxi Province(grant to Zhiyong Zhang,20213BCJ22006)。
文摘Taxonomic uncertainties of rare species often hinder effective prioritization for conservation.One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii.F.chienii was previously only known from the type specimens collected in 1935 in Pingwu County of Sichuan Province,China,and has long been thought to be on the verge of extinction.However,morphological similarities to closely related Fagus species have led many to question the taxonomic status of F.chienii.To clarify this taxonomic uncertainty,we used the newly collected samples to reconstruct a molecular phylogeny of Chinese Fagus species against the phylogenetic backbone of the whole genus using seven nuclear genes.In addition,we examined nine morphological characters to determine whether F.chienii is morphologically distinct from its putatively closest relatives(F.hayatae,F.longipetiolata,and F.lucida).Both morphological and phylogenetic analyses indicated that F.chienii is conspecific with F.hayatae.We recommended that F.chienii should not be treated as a separate species in conservation management.However,conservation strategies such as in situ protection and ex situ germplasm preservation should be adopted to prevent the peculiar“F.chienii”population from extinction.
基金supported by the Joint Funds of the National Natural Science Foundation of China(U1931107)supported by the National Key Research and Development Program of China No.2021YFA1600500。
文摘A Fourier transform spectrometer(FTS)has been used to observe solar activities due to its ultra-high spectral resolution.However,the FTS in-band spectra are usually distorted and some artifacts appear in out-of-band regions due to nonlinear effects.Therefore,the FTS nonlinear problem must be corrected.In this study,we proposed a novel method to correct the nonlinear effects using simulated annealing.We simulated several nonlinear spectra to evaluate the performance of our method.The calculated quadratic coefficients are extremely close to the given values,demonstrating that the method is effective and accurate.The proposed method is further used to correct the blackbody and solar spectra with nonlinearity obtained by Bruker IFS-125HR installed at the Huairou Solar Observing Station,which is a pathfinder for the accurate infrared magnetic field measurements of the Sun project.To the blackbody spectra,the nonlinearity in low-and high-frequency regions are corrected by 89.09%and 60.84%.The nonlinear correction of the solar spectra in the low-and high-frequency regions have reached 65.34%and 81.04%,respectively.These results prove that our method can correct the nonlinear problem to improve the data accuracy.
基金This work was financially supported by the National Key Research and Development Program of China(Grant Nos.2020YFB2008305,2020YFB2008303)the Natural Science Foundation of Shenyang City(Grant No.22315605).
文摘The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and compositions of the TA15 alloy and its composites were analyzed by XRD and EDS,and their electrochemical corrosion behaviors in the 3.5%NaCl solution were studied.Corrosion wear testing was conducted using a reciprocating ball-on-disc wear tester under a 10 N load.Results show that the in situ fibrous TiB phase and the granular TiC phase are uniformly distributed on the composite matrix.The microhardness can reach up to 531 HV as 25vol.%TiC+TiB reinforcement is added.Compared with the TA15 alloy,the volume wear rate decreases from(2.21±0.07)×10^(-4)to(1.75±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1)by adding 15vol.%TiC+TiB reinforcement,and the wear mechanism is adhesive wear.When the volume percentage of the reinforcement phase reaches 25%,the volume wear rate increases from(1.75±0.07)×10^(-4)to(2.41±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1),and the wear mechanism changes into abrasive wear.The volume loss resulted by the interaction between corrosion and wear accounts for more than 27%of the total wear volume.The volume loss due to wear-induced corrosion changes from 1.94%to 4.06%with different additions of reinforcement.The volume loss caused by corrosion-induced wear initially increases from 24.08%to 26.90%as the reinforcement increases from 0 to 15%due to the increase of corrosion potential,and then decreases from 26.90%to 25.68%as the reinforcement increases from 15%to 25%due to the peeling of TiC phase.
基金China Aerospace Science and Technology Corporation, the NO.771 InstituteChina Academy of Engineering Physics+4 种基金Changchun Institute of Optics, Fine Mechanics and Physics, CASNational Space Science Center, CASShanghai Engineering Center for Microsatellites, CASPurple Mountain Observatory, CASsupported by Grants:XDA15320102, 11427901 and XDA15052200
文摘The Full-disk Magneto Graph(FMG),a payload onboard the Advanced Space Solar Observatory(ASO-S),will measure the vector magnetic field in the photosphere.The instrument consists of a frontwindow filter,a telescope,an LCVR polarimeter,an image-stabilization system,a seven-stage tunable Lyot filter,a CMOS camera with 4096×4096 pixels and a pair of calibration/focus wheels.In this paper,we describe the design of the FMG instrument and provide a summary of test observations carried out with the FMG prototype.
基金This work was jointly supported by the National Key Research and Development Program of China(No.2016YFA0401600)National Natural Science Foundation of China(Nos.11235012 and 12035017)+1 种基金the CSNS Engineering Projectthe Back-n Collaboration Consortium fund。
文摘Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n white neutron source),which was completed in March 2018.The Back-n neutron beam is very intense,at approximately 29107 n/cm2/s at 55 m from the target,and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices.In addition,the excellent energy spectrum spanning from 0.5 eV to 200 MeV,and a good time resolution related tothe time-of-flight measurements make it a typical white neutron source for nuclear data measurements;its overall performance is among that of the best white neutron sources in the world.Equipped with advanced spectrometers,detectors,and application utilities,the Back-n facility can serve wide applications,with a focus on neutron-induced cross-sectional measurements.This article presents an overview of the neutron beam characteristics,the experimental setups,and the ongoing applications at Backn.
文摘AIM To explore the features and prognostic value of lymph node metastasis in patients with T1-stage colorectal cancer(CRC).METHODS In all,321 cases of T1-stage CRC were selected from 10132 patients with CRC who received surgical therapy in six large-scale hospitals in China and were retrospectively analyzed. Univariate and multivariate analyses were performed to analyze the risk factors for lymphatic metastasis. A survival analysis was then performed to analyze the prognostic value of lymph node metastasis.RESULTS The occurrence rate of T1 stage was 3.17%(321/10132);of these patients,the lymph node metastasis rate was 8.41%(27/321),and the non-lymph node metastasis rate was 91.59%(294/321). Univariate analysis showed that preoperative serum CEA,preoperative serum CA199,preoperative serum CA724,vascular invasion,and degree of differentiation were associated with lymph node metastasis in T1-stage CRC(P < 0.05 for all). Multivariate analysis indicated that preoperative serum CA724,vascular invasion,and degree of differentiation were closely related to lymph node metastasis(P < 0.05 for all). Log-rank survival analysis showed that age,preoperative serum CEA,preoperative serum CA199,vascular invasion,degree of differentiation,and lymph node metastasis(χ2 = 24.180,P < 0.001) were predictors of 5-year overall survival(OS)(P < 0.05 for all). COX regression analysis demonstrated that preoperative serum CA199 and lymph node metastasis(HR = 5.117;P < 0.05;95%CI: 0.058-0.815) were independent prognostic indicators of 5-year OS in patients with T1-stage CRC(P < 0.05 for both). CONCLUSION The morbidity of T1-stage CRC was 3.17% for all CRC cases. Preoperative serum CA724,vascular invasion,and degree of differentiation are independent risk factors for lymph node metastasis. Lymph node metastasis is an independent prognostic factor for OS in patients with T1-stage CRC.
基金the National Natural Science Foundation of China,No.81874201Shanghai Municipal Commission of Health and Family Planning,No.ZK2015A32 and No.201840359
文摘BACKGROUND Lymphovascular invasion (LVI) is suggested to be an early and important step in tumor progression toward metastasis, but its prognostic value and genetic mechanisms in colorectal cancer (CRC) have not been well investigated. AIM To investigate the prognostic value of LVI in CRC and identify the associated genomic alterations. METHODS We performed a retrospective analysis of 1219 CRC patients and evaluated the prognostic value of LVI for overall survival by the Kaplan-Meier method and multivariate Cox regression analysis. We also performed an array-based comparative genomic hybridization analysis of 47 fresh CRC samples to examine the genomic alterations associated with LVI. A decision tree model was applied to identify special DNA copy number alterations (DCNAs) for differentiating between CRCs with and without LVI. Functional enrichment and protein-protein interaction network analyses were conducted to explore the potential molecular mechanisms of LVI. RESULTS LVI was detected in 150 (12.3%) of 1219 CRCs, and the presence was positively associated with higher histological grade and advanced tumor stage (both P < 0.001). Compared with the non-LVI group, the LVI group showed a 1.77-fold (95% confidence interval: 1.40-2.25, P < 0.001) increased risk of death and a significantly lower 5-year overall survival rate (P < 0.001). Based on the comparative genomic hybridization data, 184 DCNAs (105 gains and 79 losses) were identified to be significantly related to LVI (P < 0.05), and the majority were located at 22q, 17q, 10q, and 6q. We further constructed a decision tree classifier including seven special DCNAs, which could distinguish CRCs with LVI from those without it at an accuracy of 95.7%. Functional enrichment and proteinprotein interaction network analyses revealed that the genomic alterations related to LVI were correlated with inflammation, epithelial-mesenchymal transition, angiogenesis, and matrix remodeling. CONCLUSION LVI is an independent predictor for survival in CRC, and its development may correlate with inflammation, epithelial-mesenchymal transition, angiogenesis, and matrix remodeling.
基金supported by the National Key Research and Development Plan(No.2016YFA0401603)the National Natural Science Foundation of China(No.11675155)
文摘To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The measurement is performed at the Back-n white neutron source with a 76-m time-of-flight path using the China Spallation Neutron Source. A multilayer fast fission chamber with 235U and 238U is employed as the neutron detector. The diameter and thickness of the natural graphite sample are 70 mm and 40 mm, respectively. Signal waveforms are collected using a data acquisition system. Off-line data processing was used to obtain the neutron time-of-flight spectra and transmissions. The uncertainty of the counting statistics is generally approximately 3% for each bin in the energy range of 1–20 MeV. It is determined that the results for the neutron total cross section of carbon obtained using ^235U cells are in good agreement with the results obtained using 238U cells within limits of statistical uncertainty. Moreover, the measured total cross sections show good agreement with the broadening evaluated data.
基金financially supported by the Liaoning Natural Science Foundation ( Grant No.20170540888)the Liaoning Science and Technology Project (Grant No.2017221006)
文摘Casting technology of thin-wall TiAl alloy turbochargers was studied by investment casting and numerical simulation.Misruns and gas holes were the main defects observed in preliminary work due to the poor fluidity of alloy,and to gas entrapment.In order to eliminate these defects,cast parameters,such as centrifugal rotation rate and mould preheating temperature,were optimized by numerical simulation,meanwhile,the structure of the shell mould was optimized to improve the filling capacity of TiAl alloy.Pouring experiments were carried out by vacuum induction melting furnace equipped with a water-cooled copper crucible based on the above optimization.The quality of the TiAl alloy casting was analyzed by fluorescent penetrant inspection and X-ray detection.The results show that a centrifugal rotation rate of 200 rpm,mould preheating temperature of 600°C,shell preparation through organic fiber addition can dramatically improve the mould filling capacity,and integrated turbochargers were finally prepared.
基金Supported by grants from the Cancer Research Coordinating Committee of the University of California, United Stated.
文摘AIM： To study the relationship between particularly interesting new cysteine-histidine rich protein （PINCH） expression and clinicopathological factors in Chinese colorectal cancer patients. METHODS： The expression of PINCH was examined by immumohistochemistry in 141 samples of primary colorectal adenocarcinoma and 92 normal samples of colorectal mucosa. Eighty of the cases had both primary tumour and normal mucosa from the same patients. RESULTS： PINCH was expressed in the stroma of normal mucosa and tumours. PINCH expression in tumourassociated stroma was increased compared to normal mucosa in both unmatched cases （n = 141, x^2 = 85.79, df = 3, P〈 0.0001） and matched cases （n =80, x^2= 45.86, df= 3, P〈 0.0001）. Among 135 tumours with visible invasive margin, 86 （64%） showed stronger PINCH expression at the invasive margin than in the intratumoural stroma. The frequency of PINCH strong expression in mucinous and signet-ring cell carcinomas was higher （52%） compared to non-mucinous carcinomas （29%, x^2=5.13, P= 0.02）. We did not find that PINCH expres- sion was related to patient＇s gender, age, tumour location, tumour size, gross status, histological type, differentiation, invasion depth, lymph node status and Dukes＇ stage （P 〉 0.05）.CONCLUSION： The expression of PINCH was upregulated in colorectal cancers, and especially at the margin of tumours, and further was related to mucinous and signet-ring cell carcinomas. The results suggest that expression of PINCH may be involved in the tumourigenesis and aggressiveness of colorectal cancers.
基金Supported by the National Natural Science Foundation of China(30830099)China Postdoctoral Science Foundation(20100481341)Scienceand Technology Research and Development Project of Shaanxi Province(2009K14-01)
文摘Objective To assese the healing of stoma after magnetic anastomosis for the reconstruction of biliary-enteric continuity under severe inflammation. Methods Acute bile duct injury was constructed as a bile peritonitis model in mongrel dogs(n=32). Magnetic anastomosis(group A, n=16) and traditional suture anastomosis(group B, n=16) were performed to reconstruct the biliary-enteric continuity in one stage. Half of the dogs in each group were euthanized on the 30 th postoperative day, and the other half on the 90 th postoperative day to harvest the stoma region. The healing conditions of the stoma after the 2 anastomotic approaches were observed with naked eyes, under light microscope and scanning electron microscope. Results The stoma leakage rate(50% versus 0% on the 30 th postoperative day, 37.5% versus 12.5% on the 90 th postoperative day, both P<0.05) and stenosis degree(13.9%±0.3% versus 7.1%±0.3% on the 30 th postoperative day, 17.2%±0.4% versus 9.4%±0.4% on the 90 th postoperative day, both P<0.01) were significantly higher in group B than in group A. Compared with traditional manual anastomoses, the histological analysis under light and electron microscope showed a more continuous stoma with more regular epithelium proliferation and collagen arrangement, less inflammation in group A. Conclusions Magnetic anastomosis stent ensures better healing of the stoma even under the circumstance of severe inflammation.
基金the National Key R&D Program of China(2017YFA0104900)the National Natural Science Foundation of China(81630065,31830029,and 81802195)the China Postdoctoral Science Foundation(2017M621913).
文摘The limited molecular classifications and disease signatures of osteoarthritis(OA)impede the development of prediagnosis and targeted therapeutics for OA patients.To classify and understand the subtypes of OA,we collected three types of tissue including cartilage,subchondral bone,and synovium from multiple clinical centers and constructed an extensive transcriptome atlas of OA patients.By applying unsupervised clustering analysis to the cartilage transcriptome,OA patients were classified into four subtypes with distinct molecular signatures:a glycosaminoglycan metabolic disorder subtype(C1),a collagen metabolic disorder subtype(C2),an activated sensory neuron subtype(C3),and an inflammation subtype(C4).Through ligand-receptor crosstalk analysis of the three knee tissue types,we linked molecular functions with the clinical symptoms of different OA subtypes.For example,the Gene Ontology functional term of vasculature development was enriched in the subchondral bone-cartilage crosstalk of C2 and the cartilage-subchondral bone crosstalk of C4,which might lead to severe osteophytes in C2 patients and apparent joint space narrowing in C4 patients.Based on the marker genes of the four OA subtypes identified in this study,we modeled OA subtypes with two independent published RNA-seq datasets through random forest classification.The findings of this work contradicted traditional OA diagnosis by medical imaging and revealed distinct molecular subtypes in knee OA patients,which may allow for precise diagnosis and treatment of OA.
基金funded by the Foundation from Education Department of Jiangxi Province (2007-149)the National Natural Science Foundation of China (30460020)the Cultivation Programs for Young Scientists of Jiangxi Province (2008DQ01500)
文摘Sinomanglietia glauca is a critically endangered species described from Jiangxi Province in the 1990s. Recently two populations were discovered from Yongshun County of west Hunan Province, about 450 km away from those in Jiangxi. Because of the new findings and the poor reproducibility inherent to RAPD and ISSR markers of previous studies, the population structure of this rare species was reanalyzed with chloroplast PCR-SSCP （single-stranded conformation polymorphism）, including all of four recorded populations. The results showed that two distinct haplotypes characterized Jiangxi and Hunan populations separately, with no genetic variation occurring within regions. We postulated that this surprising pattern might result from habitat fragmenta- tion and demographic bottlenecks during and/or after the Quaternary glaciation. On the basis of the pronounced genetic structure, two evolutionarily significant units （ESUs） were recommended for effective conservation of S. glauca.
