最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：Background: Synchrotron Radiation X-ray fluorescence analysis is an advanced method of quantitative elemental analysis.It is a scientific platform for life science,material science,and environmental science.Purpose: In this present study,the drug loading behavior of dendrimers nano-vectors was investigated by using the method of Synchrotron Radiation X-ray fluorescence analysis.Methods: The copper（II） ions were loaded into acetyl-modified generation 5（G5） PAMAM dendrimers.We monitored and imaged the distribution of copper in A549 cell by Shanghai Synchrotron Radiation Facility（SSRF） to observe the cellular uptake of copper-dendrimers conjugates.Results: The results of hard X-ray fluorescence mapping showed a stronger fluorescence of Cu in the cells treated with G5-Ac-Cu than that of control.Conclusions: This investigation provided a method of using synchrotron radiation X-ray fluorescence analysis to study the drug loading behavior of dendrimers.关键词：Synchrotron radiation;Hard X-ray fluorescence mapping;Dendrimers;Nano-vectors
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发布时间：2021-06-03 - 摘要：Background: Fe-Ga alloy is a new magnetostrictive material of lower price and better extensibility in comparison with conventional Tb-Dy-Fe alloys.Many researches revealed that the microstructure and magnetostriction are influenced by preparing method and heat treatment.Purpose: In order to study the influence of microstructure on magnetostrctive properties of Fe-Ga alloy,the phase structures,local structure and magnetostrictive properties of Fe85Ga15 ribbons prepared by different wheel speed was studied.Methods: We utilized high resolution x-ray diffraction（HRXRD） to characterize the phase structure and used Extend X-ray absorption fine structure（EXAFS） to study the local structure of the ribbons in Synchrotron Radiation Facility.Results: X-ray diffraction showed that only disordered BCC phase was observed in as-cast Fe85Ga15alloy.Modified-DO3phase were detected in all of the melt spun samples.Both the HRXRD and EXAFS results indicated that Ga atoms were located as second-nearest neighbour along [100] orientation.A little DO3 phase was found in ribbons annealed at 1000℃ under Ar atmosphere.Conclusions: Higher wheel speed will generate more modified-DO3 phase which will enhance the magnetostriction.DO3phase in the annealing sample will deteriorate the magnetostrictive properties of Fe-Ga ribbons.关键词：Fe-Ga alloys;Microstructure;Modified DO3phase;Magnetostriction
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发布时间：2021-06-03 - 摘要：Background: Pulsed fast/thermal neutron analysis（PFTNA） is an advanced bulk technique for non-destructive elemental characterization,which was applied to landmine identification in some advanced countries.Purpose: To demonstrate the feasibility of the PFTNA landmine detection method.Methods: A PFTNA landmine identification system was set up based on a millisecond pulsed D-T neutron generator and a LaBr3（Ce） gamma detector.Interrogative experiment was carried out on different landmines and distracters in the typical organic soils and inorganic soils.Results: The fast neutron induced spectra and the thermal neutron induced spectra of the samples were obtained successfully through time-sharing measurement circuit.The relative contents of 12C、16O、1H、14N contained in the objects were obtained through the analysis of the neutron induced spectra.Conclusions: It could be concluded that the PFTNA method can identify the landmines from the common distracters.关键词：Pulsed fast/thermal neutron analysis（PFTNA）;Neutron-based interrogation;Landmine identification
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发布时间：2021-06-03 - 摘要：Background: B4C/Al composite is an ideal neutron shielding material with good mechanical property,which is successfully made as spent fuel container.Purpose: To study its shielding property under different conditions,so as to make use of it properly.Method: Monte-Carlo method is applied to calculate the shielding property of B4C/Al composite.Results: The content of B4C and transmission coefficient is a linear relationship,with a small drop.Transmission coefficient show up and down with the increasing neutron energy,When the neutron energy is 0.5,0.8 or 1.2 MeV,there is a low transmission coefficient.Material thickness and transmission coefficient is a exponential relationship,with a great drop.It can reach ideal shielding effect when it’s thickness is more than 13 cm.Conclusions: the content of carbide boron can not change neutron shielding effect significantly.B4C/Al composite is suitable for shielding neutron of 0.5,0.8,1.2 MeV.To reduced neutron radiation effect,adding thickness of material is the best way.关键词：B4C/Al composite;Neutron shielding;Monte-Carlo simulation
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发布时间：2021-06-03 - 摘要：Background: Being one of the sixteen radionuclide laboratories for CTBT,Beijing radionuclide laboratory studied the β-γ coincidence system to measure the activities of xenon isotopes（131mXe,133mXe,133Xe and 135Xe）.The efficiency calibration is an important and difficult technique in the β-γ coincidence measurement.Purpose: The study is carried out to calibrate the efficiency for the β-γ coincidence system.Methods: The efficiency of the β（γ） particle can be calculate by the ratio of the coincidence counts/single γ（β） counts without knowing the sample activity.A 133Xe and131mXe mixture,whose activity is not known,is used to calibrate the efficiency.Results: The efficiency for the β-γ coincidence system is got by this method.Conclusions: The method has been used to calibrate the efficiencies of β-γ coincidence system in our laboratory.关键词：β-γcoincidence system;Detection efficiency;133Xe;131mXe
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发布时间：2021-06-03 - 摘要：Background: LaBr3（Ce） detector has played an important role in detecting explosive,contraband and landmine because of its high detection efficiency and good energy resolution etc.Purpose: To calibrate detector in wide energy region.Methods: The gamma spectra of NH4Cl and C3H6N6 induced by 252Cf neutron source were measured.Results: Comparing their gamma spectra,characteristic gamma lines can be located and the energy calibration curve was obtained.Conclusions: Radio nuclides can be identified by the calibration curve fitted with quadratic or cubic polynomial.
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发布时间：2021-06-03 - 摘要：Background: Equivalent dose（De） is one of the most important parameters in OSL dating.In the standardized growth curve（SGC） method for Dedetermination,the arithmetic average values of all Des were taken as a sample’s final De.However,without De error for each individual aliquot,it is not possible to determine the De maximum likelihood estimation value use SGC.Purpose: In this study,we try to estimate the error for each individual aliquot,and then obtain maximum likelihood estimation of a De.Methods: We found that the Deerrors by our method and the SAR method are in good agreement.Results & Conclusions: For a sample with multi-aliquot Des,the maximum likelihood estimation is more close to the actual value,and the maximum likelihood estimation method is better than other estimate methods used.关键词：OSL dating;Standardized growth curve;Equivalent dose error
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发布时间：2021-06-03 - 摘要：Background: The failure phenomenon is difficult to analyze for the flash memories when the whole chip is exposed to irradiation since both the memory array and the peripheral circuits might be degraded.Purpose: In order to detect the radiation susceptibility and corresponding phenomenon of the related circuits that included in the flash memories,the X-ray microbeam is used as the radiation source instead of 60 Co.Methods: The failure phenomenon is studied respectively when the memory array,decoder circuits,the charge pump circuits as well as the I/O circuits are exposed to radiation.The errors are mapped according to the logical address and the failure mechanism is analyzed based on the circuits.Results: Irradiated on the memory array will lead to regularly distributed 0→1 bit flips,while only 1→0 are found when the row decoder is under exposure.Degradation of the charge pump circuits would lead to the erase/program functional failure.Conclusions: The results suggest that the X-ray microbeam radiation test is a good method for detecting the radiation susceptibility of the integrated circuits that contains lots of circuit modules.关键词：Flash ROM;X-ray microbeam;Localized total dose;Error map
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发布时间：2021-06-03 - 摘要：Background: The global supply shortage of medical radioisotopes caused by the unscheduled shutdown of the aged reactors which supply over 90% of radioisotopes overall the world,has severely affected the normal healthcare system which depend on the technology of molecular imaging for diagnoses and therapy as well as the development of nuclear molecular imaging technology.Purpose: It is urgently needed to develop new alternative technologies to solve the problem of global radioisotope supply shortage.Methods: The proton cyclotron is a potential alternative technology to produce the99mTc and the most of medical radioisotopes of clinical importance.Results: The quality of 99mTc produced by cyclotron,such as nuclide purity,specific activity and nonradioisotope impurities,has reached and/or exceeded that eluted from99Mo/99mTc generator produced by reactor.Conclusions: It is the most operational and sustainable way to substitute the conventional global centralized supply by reactors with local centralized supply of radioisotopes by proton cyclotrons for securing the national supply of radioisotopes.关键词：Radioisotope;99mTc;Cyclotron;Reactor;Global centralized supply;Local centralized supply
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发布时间：2021-06-03 - 摘要：Background: Shanghai Soft X-ray FEL is under design and construction at Shanghai Institute of Applied Physics（SINAP）.Purpose: The stability of the existing SSRF Linac modulator has achieved 500ppm.But the Soft X-FEL requires 100PPM.Methods: This paper describes control strategy based on pulse amplitude feedback technology,and gives the design of signal conditioning circuit in more details.The signal conditioning circuit contains amplitude fading,LPF and cutting etc.Results: The relevant experiments show that the circuit reaches required function and stability.Conclusions: Feedback control strategy is useful for the existing modulator.关键词：Pulse modulator;Stability;Signal acquisition and processing;Filter;Cutting and amplification
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发布时间：2021-06-03 - 摘要：Background: Detection efficient is one of the important technical parameters in the device of measuring radon in balloon method.Its value would influence the veracity of the result.Purpose: This paper had explored a new method about calculating detection efficient of the device measuring radon in balloon method.Methods: The expression of detection efficient has been deduced based on the principle of measuring radon and the new device which is IED-3000F developed by Chengdu University of Technology.Results: The detection efficient’ experimental value has been measured.Conclusions: The result show that this theory used in calculating detection of balloon method for measurement of radon is quite feasible in the range of error.关键词：Radon daughter;Balloon method for measuring radon;Detection efficiency
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发布时间：2021-06-03 - 摘要：Background: Core promoters,which immediately flank transcriptional starting sites,play an important role in eukaryotic transcriptional regulation.As a new frontier in this field,their diversified shapes,structures and regulatory mechanisms have been discovered in higher eukaryotes in recent years.Purpose: To further analyze their structure and transcriptional regulation mechanisms in simple eukaryotes.Methods: We used CAGE technology to capture the transcriptional starting sites in fission yeast（Schizosaccharomyces pombe） on a genome-wide scale.We identified their core promoter regions and analyzed their shape and sequence.Results: Our research revealed that lower eukaryotes,like yeast,share the similar diversity in their core promoter structure with higher eukaryotes.Conclusions: Our result suggests that transcriptional regulations are probably more complicated in lower eukaryotes than we previously thought.关键词：Transcriptional starting sites;Core promoter;DNA motif;Fission yeast
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发布时间：2021-06-03 - 摘要：Background: Unlike the traditional solid fuel reactor with fixed boundary conditions,the inlet and outlet pipe and the core of molten salt reactor fuel is connected so that the flowing liquid fuel can travel freely between the pipe and core.Purpose: This article has made systematic study of the influence of different molten salt fuel regions on reactor physics,including the top and bottom fuel of the core vessel and the pipe fuel.The core physics was researched under different boundary conditions,and the region of the effective core was indicated subsequently.Methods: MSRE was taken as the reference reactor and the calculation was completed based on the Monte Carlo Code MCNP.Results: Results show that the fuel in the top and bottom of vessel impacts on keff and energy spectrum obviously.The influence of outlet pipe on keffwas negligible when pipe radius less than 25 cm,and the perturbation of outlet pipe on the keffcould be neglected when its length more than 20 cm.Conclusions: Results provide rational theory for the design of MSR and the development of computation code.关键词：Molten salt reactor;Effective core;MSRE;Boundary conditions
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发布时间：2021-06-03 - 摘要：Background: In nuclear plant vapor explosion analysis,fuel drop diameter is an important parameter which could significantly influence the evaluation of explosion pressure.Purpose: Decrease the uncertainty of vapor explosion calculation caused by fuel drop diameter.Methods: A simulation model of typical vapor explosion was built using MC3D to take sensitive analysis of fuel drop diameter.Results: The calculation relates to fuel drop energy,fuel drop fragmentation rate and vapor explosion pressure.The effect of fuel drop diameter in vapor explosion is analyzed based on theoretical analysis and the calculation.Conclusions: The results show that the vapor explosion pressure is very sensitive to fuel drop diameter,which is mainly caused by the fuel drop energy and the fuel drop fragmentation rate.关键词：Severe accident;Vapor explosions;FCI（fuel-coolant interaction）;Fuel drop diameter
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发布时间：2021-06-03 - 摘要：Background: Nonparametric statistical method is a kind of statistical inference method not depending on a certain distribution;it calculates the tolerance limits under certain probability level and confidence through sampling methods.The DNBR margin is one important parameter of NPP design,which presents the safety level of NPP.Purpose & Methods: This paper uses nonparametric statistical method basing on Wilks formula and VIPER-01 subchannel analysis code to calculate the DNBR design limits（DL） of 300MW NPP（Nuclear Power Plant） during the complete loss of flow accident,simultaneously compared with the DL of DNBR through means of ITDP to get certain DNBR margin.Results: The results indicate that this method can gain 2.96% DNBR margin more than that obtained by ITDP methodology.Conclusions: Because of the reduction of the conservation during analysis process,the nonparametric statistical method can provide greater DNBR margin and the increase of DNBR margin is benefited for the upgrading of core refuel scheme.关键词：Nonparametric statistics;DNBR limit;Complete loss of flow;Subchannel analysis code
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发布时间：2021-06-03
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