The observations of Ultra High Energy Cosmic Rays （UHECR） are renewed, focusing on the energy spectra as measured by HiRes, Telescope Array （TA） and Auger detectors （PAO）. It is found that highest energy Auger s...The observations of Ultra High Energy Cosmic Rays （UHECR） are renewed, focusing on the energy spectra as measured by HiRes, Telescope Array （TA） and Auger detectors （PAO）. It is found that highest energy Auger steepening does not agree with GZK cutoff, which is most probably explained by the nuclei mass composition detected by Auger. At present the difference in mass composition in Auger and HiRes/TA data remains the main unsolved problem of UHECR origin.展开更多
We propose a photon-photon collider based on synchrotron gamma sources driven by relativistic electron beams in hollow plasma channels.The collimated(with a divergence angle of~1 mrad)and ultrabrilliant(>10^(28)pho...We propose a photon-photon collider based on synchrotron gamma sources driven by relativistic electron beams in hollow plasma channels.The collimated(with a divergence angle of~1 mrad)and ultrabrilliant(>10^(28)photons s^(-1)·mrad^(-2)·mm^(-2)per 0.1% bandwidth at 0.6 MeV)photon beams are generated by strong electromagnetic fields induced by current filamentation instability,and up to~10^(6) Breit-Wheeler(BW)pairs can be created per shot.Notably,the usage of hollow plasma channels not only enhances synchrotron radiation,but also allows flexible control of the produced photon beams,ensuring the alignment of the two colliding beams and maximizing the two-photon BW process.This setup has the advantage of a clean background by eliminating the yield from the nonlinear BW process,and the signal-to-noise ratio is higher than 10^(2).展开更多
Mutation breeding is based on the induction of genetic variations; hence knowledge of the frequency and type of induced mutations is of paramount importance for the design and implementation of a mutation breeding pro...Mutation breeding is based on the induction of genetic variations; hence knowledge of the frequency and type of induced mutations is of paramount importance for the design and implementation of a mutation breeding program. Although γ ray irradiation has been widely used since the 1960 s in the breeding of about 200 economically important plant species, molecular elucidation of its genetic effects has so far been achieved largely by analysis of target genes or genomic regions. In the present study, the whole genomes of six γ-irradiated M2 rice plants were sequenced; a total of 144–188 million high-quality（Q〉20） reads were generated for each M2 plant, resulting in genome coverage of 45 times for each plant. Single base substitution（SBS） and short insertion/deletion（Indel） mutations were detected at the average frequency of 7.5×10^-6～9.8×10^-6 in the six M2 rice plants（SBS being about 4 times more frequent than Indels）. Structural and copy number variations, though less frequent than SBS and Indel, were also identified and validated. The mutations were scattered in all genomic regions across 12 rice chromosomes without apparent hotspots. The present study is the first genome-wide single-nucleotide resolution study on the feature and frequency of γ irradiation-induced mutations in a seed propagated crop; the findings are of practical importance for mutation breeding of rice and other crop species.展开更多
Free living conchocelis of Porphyra yezoensis Ueda (Bangiales, Rhodophyta) were treated with 6 0Co γ rays of different doses (ranging from 100 Gy to 1000 Gy) to induce mutation. Most of the conchocelis maintained the...Free living conchocelis of Porphyra yezoensis Ueda (Bangiales, Rhodophyta) were treated with 6 0Co γ rays of different doses (ranging from 100 Gy to 1000 Gy) to induce mutation. Most of the conchocelis maintained the capability of penetrating into shells, growing and forming colonies in shells, but their vitality was seriously impaired by the irradiation of γ rays. A few conchocelis pigments were mutagenized directly into different color pigment mutants whose progeny conchospores and foliose thalli had the same colors. However, some irradiated conchocelis did not show the change in color at the conchocelis stage. The pigment mutation could be observed only after the conchospores of these conchocelis had germinated into young foliose thalli. Irradiation of low dose (100 Gy) promoted the growth of thallus and many with altered morphology were observed. Conchospores of the irradiated conchocelis attached to the culture nets were cultured in the sea, and growth of these progenies was observed and measured.展开更多
The refraction of rays in the Savart polariscope is different from the isotropic medium. We have analysed and discussed the refraction of rays in the Savart polariscope on the basis of the Snell law. The refraction fo...The refraction of rays in the Savart polariscope is different from the isotropic medium. We have analysed and discussed the refraction of rays in the Savart polariscope on the basis of the Snell law. The refraction formulae of the extraordinary rays and ordinary rays were derived. Results obtained may provide theoretical and practical guide lines for studying, developing and engineering of polarization interference imaging spectrometer.展开更多
The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chos...The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.展开更多
The DArk Matter Particle Explorer（DAMPE）,also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals o...The DArk Matter Particle Explorer（DAMPE）,also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.展开更多
AIM To investigate the effects of DNA repair synthesis induced by DNA polymerase β in hepatoma cells after γ ray irradiation. METHODS Cell nuclei were prepared from SMMC LTNM hepatoma which is a transplanted hu...AIM To investigate the effects of DNA repair synthesis induced by DNA polymerase β in hepatoma cells after γ ray irradiation. METHODS Cell nuclei were prepared from SMMC LTNM hepatoma which is a transplanted human liver cancer born on nude mice. Samples were irradiated with 60 Co γ rays at different doses or dose rates. N ethylmaleimide (NEM) and ddTTP were used as selective inhibitors to DNA polymerases. The reaction of DNA repair synthesis was carried out with the selective inhibitor test. RESULTS It was found that the 3H TTP incorporation in irradiated nuclei or calf thymus DNA was significantly higher than that in the non irradiated ones, under the conditions of DNA polymerase α or γ being inhibited. When NEM and ddTTP which selectively inhibits DNA polymerase β both existed in the DNA repair synthesis reaction mixture, the 3H TTP incorporation in irradiated DNA did not significantly increased. Furthermore, 3H TTP incorporation into DNA of SMMC LTNM hepatoma nuclei was higher than that of normal hepatocyte nuclei ( P <0 01). The DNA repair synthesis induced by DNA polymerase β reacted more fast in hepatoma nuclei than in hepatocyte nuclei. CONCLUSION The effects of DNA repair synthesis induced by DNA polymerase β in some tumor cells might be stronger than that in normal cells, which may facilitate the cells to repair DNA damages from radiation.展开更多
The objective of this work is to analyze the transient effects of ^60Co gamma rays in the CMOS image sensor (CIS) using the Monte Carlo method, based on Geant4. The track, energy spectrum, and angle of produced electr...The objective of this work is to analyze the transient effects of ^60Co gamma rays in the CMOS image sensor (CIS) using the Monte Carlo method, based on Geant4. The track, energy spectrum, and angle of produced electrons when gamma rays traversed a silicon or silicon dioxide cube were calculated. A simplified model of a 500 × 500 CIS array was established, and the transient effects of gamma rays in the CIS were simulated. The raw images were captured when the CIS was irradiated by gamma rays. The experimental results were compared with the simulation results. The characteristics of the typical events induced by transient effects were analyzed.展开更多
In this study, the mass attenuation coefficient of boron-containing ores in the Liaoning province of China was calculated using Win XCOM software to investigate the shielding effectiveness of these ores against gamma ...In this study, the mass attenuation coefficient of boron-containing ores in the Liaoning province of China was calculated using Win XCOM software to investigate the shielding effectiveness of these ores against gamma rays. The mass attenuation coefficients were also calculated using MCNP-4 B code and compared with Win XCOM results; consequently, a good consistency between the results of Win XCOM and MCNP-4 B was observed. Furthermore, the G-P fitting method was used to evaluate the values of exposure buildup factor(EBF) in the energy range of 0.015–15 Me V up to 40 mean free paths. Among the selected ores, boron-bearing iron concentrate ore(M3)was determined to be the best gamma ray shielding ore owing to its higher values of mass attenuation coefficient and equivalent atomic number and lower value of EBF.Moreover, American Evaluated Nuclear Data File(ENDF/B-VII) was used to analyze the shielding effectivenessagainst thermal neutrons. It was determined that Szaibelyite(M2) is the best thermal neutron shielding material.This study would be useful for demonstrating the potential of boron-containing ores for applications in the field of nuclear engineering and technology.展开更多
In recent years,there has been an increasing interest in wood properties,because wood is a commonly used and advanced building material.In this paper,the effect of anatomical characters on the transverse fracture prop...In recent years,there has been an increasing interest in wood properties,because wood is a commonly used and advanced building material.In this paper,the effect of anatomical characters on the transverse fracture properties of green wood was investigated.The specific fracture energy(Gf J/m2)of ash(Fraxinus excelsior),cherry(Prunus avium)and birch(Betula pendula)was evaluated using double edge notched tensile tests.The tests were performed on both earlywood(EW)and latewood(LW)zones in both the radial-tangential(RT)and the tangential-radial(TR)crack propagation systems.Wood anatomy and the failure patterns of each species were also investigated using environmental scanning electron microscopy(ESEM)and light microscopy(LMC).The results showed that the Gfof RT fracture systems was around 1.5 times greater than in the TR one,whereas there were no significant differences between EW and LW zones.ESEM micrographs showed that the RT fracture system had a rougher fracture surface,while the TR had a nearly smooth and fiat fracture surface.In particular,the wood ofF.excelsior was the toughest,because of its greater percentage of rays and homogenous distribution of ray cells,while P.avium and B.pendula showed a lower Gf due to their smaller percentage of rays with a distinctive arrangement of ray cells.展开更多
This paper gives an estimate of excess functions of rays on complete non-compact manifolds. By using this estimation, the authors can get the results in [3] as corollaries, which asserts that a complete manifold is di...This paper gives an estimate of excess functions of rays on complete non-compact manifolds. By using this estimation, the authors can get the results in [3] as corollaries, which asserts that a complete manifold is diffeomorphic to Rn under some curvature and pinching conditions. At last, they obtain a refinement of them with extra Ricci condition.展开更多
Panicles of an indica rice line TM7-5 were subjected to radiation with 137^Cs gamma rays at 0 （control）, 5, 10, 15 and 20 Gy respectively, and then its anthers were cultured. There were slight differences among the ...Panicles of an indica rice line TM7-5 were subjected to radiation with 137^Cs gamma rays at 0 （control）, 5, 10, 15 and 20 Gy respectively, and then its anthers were cultured. There were slight differences among the treatments in peak emerging time of callus initiation, from 38 to 44 days after inoculation （DAI） as well as the frequency of callus initiation （2.3-3.5%）. About two thirds calli were induced before 44 DAI, and calli derived beyond 60 DAI lost the regeneration ability. Green plant regeneration frequency was significantly stimulated from two- to three-fold by irradiation of the 1370S gamma rays compared with the control, and the maximum was 22,81% （15 Gy）. The culture ability based on callus initiation and green plantlet regeneration was 0.19% for the control while it was over 0.45% for all the irradiated treatments, and the maximum was 0,59% for 15 Gy treatment. The advantages of panicle irradiation before anther culture and the potential application in rice anther culture, especially for recalcitrant indica rice, were discussed.展开更多
To evaluate the influence of the DNA concentra-tion in the aqueous solution on DNA radiation damage, the plasmid DNA in the presence or absence of Mannitol (scavenger of free radical OH-) was irradiated by 7Li ions a...To evaluate the influence of the DNA concentra-tion in the aqueous solution on DNA radiation damage, the plasmid DNA in the presence or absence of Mannitol (scavenger of free radical OH-) was irradiated by 7Li ions and γ rays at various DNA concentrations. Gel electrophore-sis analysis revealed that the DNA damage of single and double strand breaks induced by irradiation was dependent on DNA concentra-tion and became more severe at lower DNA concentration in the radiation experiment when all others parameters are the same. In the con-dition of γ-ray irradiation, most of double strand breaks (DSB) damage was neutralized and less associated with DNA concentration in the presence of mannitol. However, under 7Li irradiation, the DSB damage could not be cleared by mannitol but was gradually aggravated with de- creasing DNA concentrations. Our study sheds light on the underlying mechanisms in the DNA radiation damage process. And there are poten-tial significances for the human space flight, cancer therapy by heavy ions as well as the ra-diation security assessment.展开更多
The influence of a new anisotropic factor onto the mechanism of accelerating cosmic rays up to ultrahigh energies (CR UHE) due to a new global natural force with the anisotropic behavior is considered. The directions ...The influence of a new anisotropic factor onto the mechanism of accelerating cosmic rays up to ultrahigh energies (CR UHE) due to a new global natural force with the anisotropic behavior is considered. The directions in the physical space along which CR UHE can arrive, are predicted. A brief comparative analysis of these directions together with the obtained experimental results is given. Their qualitative coincidences are shown.展开更多
文摘The observations of Ultra High Energy Cosmic Rays （UHECR） are renewed, focusing on the energy spectra as measured by HiRes, Telescope Array （TA） and Auger detectors （PAO）. It is found that highest energy Auger steepening does not agree with GZK cutoff, which is most probably explained by the nuclei mass composition detected by Auger. At present the difference in mass composition in Auger and HiRes/TA data remains the main unsolved problem of UHECR origin.
基金supported by the Fund of the National Key Laboratory of Plasma Physics(Grant No.6142A04230204)the National Natural Science Foundation of China(Project No.12075046).
文摘We propose a photon-photon collider based on synchrotron gamma sources driven by relativistic electron beams in hollow plasma channels.The collimated(with a divergence angle of~1 mrad)and ultrabrilliant(>10^(28)photons s^(-1)·mrad^(-2)·mm^(-2)per 0.1% bandwidth at 0.6 MeV)photon beams are generated by strong electromagnetic fields induced by current filamentation instability,and up to~10^(6) Breit-Wheeler(BW)pairs can be created per shot.Notably,the usage of hollow plasma channels not only enhances synchrotron radiation,but also allows flexible control of the produced photon beams,ensuring the alignment of the two colliding beams and maximizing the two-photon BW process.This setup has the advantage of a clean background by eliminating the yield from the nonlinear BW process,and the signal-to-noise ratio is higher than 10^(2).
基金supported by the National Natural Science Foundation of China(No.11275171)the National Key Technology R&D Program of China(No.2014BAA03B04)the Mutation Breeding Project of the Forum for Nuclear Cooperation in Asia(FNCA)
文摘Mutation breeding is based on the induction of genetic variations; hence knowledge of the frequency and type of induced mutations is of paramount importance for the design and implementation of a mutation breeding program. Although γ ray irradiation has been widely used since the 1960 s in the breeding of about 200 economically important plant species, molecular elucidation of its genetic effects has so far been achieved largely by analysis of target genes or genomic regions. In the present study, the whole genomes of six γ-irradiated M2 rice plants were sequenced; a total of 144–188 million high-quality（Q〉20） reads were generated for each M2 plant, resulting in genome coverage of 45 times for each plant. Single base substitution（SBS） and short insertion/deletion（Indel） mutations were detected at the average frequency of 7.5×10^-6～9.8×10^-6 in the six M2 rice plants（SBS being about 4 times more frequent than Indels）. Structural and copy number variations, though less frequent than SBS and Indel, were also identified and validated. The mutations were scattered in all genomic regions across 12 rice chromosomes without apparent hotspots. The present study is the first genome-wide single-nucleotide resolution study on the feature and frequency of γ irradiation-induced mutations in a seed propagated crop; the findings are of practical importance for mutation breeding of rice and other crop species.
文摘Free living conchocelis of Porphyra yezoensis Ueda (Bangiales, Rhodophyta) were treated with 6 0Co γ rays of different doses (ranging from 100 Gy to 1000 Gy) to induce mutation. Most of the conchocelis maintained the capability of penetrating into shells, growing and forming colonies in shells, but their vitality was seriously impaired by the irradiation of γ rays. A few conchocelis pigments were mutagenized directly into different color pigment mutants whose progeny conchospores and foliose thalli had the same colors. However, some irradiated conchocelis did not show the change in color at the conchocelis stage. The pigment mutation could be observed only after the conchospores of these conchocelis had germinated into young foliose thalli. Irradiation of low dose (100 Gy) promoted the growth of thallus and many with altered morphology were observed. Conchospores of the irradiated conchocelis attached to the culture nets were cultured in the sea, and growth of these progenies was observed and measured.
基金supported by the State Key Program of National Natural Science of China (Grant No 40537031)the National Natural Science Foundation of China (Grant Nos 40375010 and 60278019)+2 种基金the Science and Technology Plan Foundation of Shaanxi Province of China (Contract No 2005K04-G18)the special research project of Shaanxi Provincial Educational Department of China (Grant Nos 07JK261 and 05JK197)the research project of Xi’an Polytechnic University of China (Grant No 2006XG34)
文摘The refraction of rays in the Savart polariscope is different from the isotropic medium. We have analysed and discussed the refraction of rays in the Savart polariscope on the basis of the Snell law. The refraction formulae of the extraordinary rays and ordinary rays were derived. Results obtained may provide theoretical and practical guide lines for studying, developing and engineering of polarization interference imaging spectrometer.
基金supported by the National Natural Science Foundation of China(Nos.11475013,11975040 and U1832130)
文摘The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.
基金founded by the strategic priority science and technology projects in space science of the Chinese Academy of Sciences (Nos.XDA04040000 and XDA04040400)supported in part by the National Key Research and Development Program of China (2016YFA0400200)+7 种基金the National Basic Research Program of China (No.2013CB837000)the Strategic Priority Research Program of the Chinese Academy of Sciences “Multi-Waveband Gravitational Wave Universe” (No.XDB23040000)Youth Innovation Promotion Association of CASthe National Natural Science Foundation of China (Nos.11525313,11673075,11773086,11303107,11303105,11773085,U1738123,U1738136,U1738207 and U1738210)the Young Elite Scientists Sponsorship program by CAST (No.YESS20160196)the 100 Talents Program of Chinese Academy of Sciencessupport by the Swiss National Science Foundation (SNSF)Switzerland and the National Institute for Nuclear Physics (INFN),Italy
文摘The DArk Matter Particle Explorer（DAMPE）,also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.
文摘AIM To investigate the effects of DNA repair synthesis induced by DNA polymerase β in hepatoma cells after γ ray irradiation. METHODS Cell nuclei were prepared from SMMC LTNM hepatoma which is a transplanted human liver cancer born on nude mice. Samples were irradiated with 60 Co γ rays at different doses or dose rates. N ethylmaleimide (NEM) and ddTTP were used as selective inhibitors to DNA polymerases. The reaction of DNA repair synthesis was carried out with the selective inhibitor test. RESULTS It was found that the 3H TTP incorporation in irradiated nuclei or calf thymus DNA was significantly higher than that in the non irradiated ones, under the conditions of DNA polymerase α or γ being inhibited. When NEM and ddTTP which selectively inhibits DNA polymerase β both existed in the DNA repair synthesis reaction mixture, the 3H TTP incorporation in irradiated DNA did not significantly increased. Furthermore, 3H TTP incorporation into DNA of SMMC LTNM hepatoma nuclei was higher than that of normal hepatocyte nuclei ( P <0 01). The DNA repair synthesis induced by DNA polymerase β reacted more fast in hepatoma nuclei than in hepatocyte nuclei. CONCLUSION The effects of DNA repair synthesis induced by DNA polymerase β in some tumor cells might be stronger than that in normal cells, which may facilitate the cells to repair DNA damages from radiation.
基金supported by the National Natural Science Foundation of China(Nos.11805155,11875223,and 11690043)the Chinese Academy of Sciences strategic pilot science and technology project(No.XDA15015000)+1 种基金the Innovation Foundation of Radiation Application(No.KFZC2018040201)the Foundation of State Key Laboratory of China(Nos.SKLIPR1803 and 1610)
文摘The objective of this work is to analyze the transient effects of ^60Co gamma rays in the CMOS image sensor (CIS) using the Monte Carlo method, based on Geant4. The track, energy spectrum, and angle of produced electrons when gamma rays traversed a silicon or silicon dioxide cube were calculated. A simplified model of a 500 × 500 CIS array was established, and the transient effects of gamma rays in the CIS were simulated. The raw images were captured when the CIS was irradiated by gamma rays. The experimental results were compared with the simulation results. The characteristics of the typical events induced by transient effects were analyzed.
基金supported by the National Natural Science Foundation of China(Nos.51472048,50774022)the Key Laboratory Project of Liaoning Province Education Office(No.LZ 2014-022)
文摘In this study, the mass attenuation coefficient of boron-containing ores in the Liaoning province of China was calculated using Win XCOM software to investigate the shielding effectiveness of these ores against gamma rays. The mass attenuation coefficients were also calculated using MCNP-4 B code and compared with Win XCOM results; consequently, a good consistency between the results of Win XCOM and MCNP-4 B was observed. Furthermore, the G-P fitting method was used to evaluate the values of exposure buildup factor(EBF) in the energy range of 0.015–15 Me V up to 40 mean free paths. Among the selected ores, boron-bearing iron concentrate ore(M3)was determined to be the best gamma ray shielding ore owing to its higher values of mass attenuation coefficient and equivalent atomic number and lower value of EBF.Moreover, American Evaluated Nuclear Data File(ENDF/B-VII) was used to analyze the shielding effectivenessagainst thermal neutrons. It was determined that Szaibelyite(M2) is the best thermal neutron shielding material.This study would be useful for demonstrating the potential of boron-containing ores for applications in the field of nuclear engineering and technology.
文摘In recent years,there has been an increasing interest in wood properties,because wood is a commonly used and advanced building material.In this paper,the effect of anatomical characters on the transverse fracture properties of green wood was investigated.The specific fracture energy(Gf J/m2)of ash(Fraxinus excelsior),cherry(Prunus avium)and birch(Betula pendula)was evaluated using double edge notched tensile tests.The tests were performed on both earlywood(EW)and latewood(LW)zones in both the radial-tangential(RT)and the tangential-radial(TR)crack propagation systems.Wood anatomy and the failure patterns of each species were also investigated using environmental scanning electron microscopy(ESEM)and light microscopy(LMC).The results showed that the Gfof RT fracture systems was around 1.5 times greater than in the TR one,whereas there were no significant differences between EW and LW zones.ESEM micrographs showed that the RT fracture system had a rougher fracture surface,while the TR had a nearly smooth and fiat fracture surface.In particular,the wood ofF.excelsior was the toughest,because of its greater percentage of rays and homogenous distribution of ray cells,while P.avium and B.pendula showed a lower Gf due to their smaller percentage of rays with a distinctive arrangement of ray cells.
文摘This paper gives an estimate of excess functions of rays on complete non-compact manifolds. By using this estimation, the authors can get the results in [3] as corollaries, which asserts that a complete manifold is diffeomorphic to Rn under some curvature and pinching conditions. At last, they obtain a refinement of them with extra Ricci condition.
文摘Panicles of an indica rice line TM7-5 were subjected to radiation with 137^Cs gamma rays at 0 （control）, 5, 10, 15 and 20 Gy respectively, and then its anthers were cultured. There were slight differences among the treatments in peak emerging time of callus initiation, from 38 to 44 days after inoculation （DAI） as well as the frequency of callus initiation （2.3-3.5%）. About two thirds calli were induced before 44 DAI, and calli derived beyond 60 DAI lost the regeneration ability. Green plant regeneration frequency was significantly stimulated from two- to three-fold by irradiation of the 1370S gamma rays compared with the control, and the maximum was 22,81% （15 Gy）. The culture ability based on callus initiation and green plantlet regeneration was 0.19% for the control while it was over 0.45% for all the irradiated treatments, and the maximum was 0,59% for 15 Gy treatment. The advantages of panicle irradiation before anther culture and the potential application in rice anther culture, especially for recalcitrant indica rice, were discussed.
文摘To evaluate the influence of the DNA concentra-tion in the aqueous solution on DNA radiation damage, the plasmid DNA in the presence or absence of Mannitol (scavenger of free radical OH-) was irradiated by 7Li ions and γ rays at various DNA concentrations. Gel electrophore-sis analysis revealed that the DNA damage of single and double strand breaks induced by irradiation was dependent on DNA concentra-tion and became more severe at lower DNA concentration in the radiation experiment when all others parameters are the same. In the con-dition of γ-ray irradiation, most of double strand breaks (DSB) damage was neutralized and less associated with DNA concentration in the presence of mannitol. However, under 7Li irradiation, the DSB damage could not be cleared by mannitol but was gradually aggravated with de- creasing DNA concentrations. Our study sheds light on the underlying mechanisms in the DNA radiation damage process. And there are poten-tial significances for the human space flight, cancer therapy by heavy ions as well as the ra-diation security assessment.
文摘The influence of a new anisotropic factor onto the mechanism of accelerating cosmic rays up to ultrahigh energies (CR UHE) due to a new global natural force with the anisotropic behavior is considered. The directions in the physical space along which CR UHE can arrive, are predicted. A brief comparative analysis of these directions together with the obtained experimental results is given. Their qualitative coincidences are shown.
