Study on the optimal incident proton energy of ^(7)Li(p,n)^(7)Be neutron source for boron neutron capture therapy

Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT applications.The^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional benefits.This study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head phantom.The study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 MeV.Furthermore,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.

The rhizosphere pH change of Pinus koraiensis seedlings as affected by N sources of different levels and its effect on the availability and uptake of Fe, Mn, Cu and Zn

Dark brown forest soil was collected from the upper 20 cm soil layer in Changbai Mountain Research Station of Ecosystem, Chinese Academy of Sciences. The soil was amended with two different forms of nitrogen fertilizers: NO3- as Ca(NO3)2, NH4+ as NH4Cl at the concentrations of 50, 100, 200 and 400 mgkg-1 respectively. The experiment was carried out with 2-yr-old Pinus koraiensis seedlings in pot. The pH change of rhizosphere soil and the contents of available Fe, Mn, Cu, and Zn in soil and leaves were analyzed. The result indicated that the addition of NH4--N decreased the rhizosphere pH value, while the addition of NO3--N increased the rhizosphere pH value in contrast with the control treatment. The direction and extent of the pH change mainly depended on N source and its concentrations applied. The rhizosphere pH change had a remarkable influence on the availability of the micronutrients in the rhizosphere, and thereafter affected the nutrient uptake by the seedlings. The contents of available mineral nutrients had a negative correlation with the pH value in the rhizosphere soil. The contents of available mineral nutrients in leaves were positively correlated to the levels of the available nutrients in the rhizosphere soils.

A half-century of radioisotope neutron sources in China

Near 50 years history of the development of radioisotope neutron sources in China is briefly reviewed.The structure design,preparing technology and production status of routine neutron sources including 210Po-Be sources,210Po mock fission sources,241Am-Be sources,238Pu-Be sources,252Cf spontaneous fission sources and other special-shape neutron sources are summarized.In addition,the prospects of development on radioisotope neutron source in China are predicted from the needs of nuclear power construction,oil well-logging,neutron moisture gauge and neutron brachytherapy.

Effects of N source and nitrification pretreatment on growth of Arthrospira platensis in human urine

Culture ofArthrospiraplatensis （Spirulinaplatens） in human urine was investigated to get valuable biomass. NO3-N was the proper N source, in comparison with other N source, including urea, NH4-N and NO2-N. As a result, aerobic nitrification of human urine was performed, with above 93.6% nitrification percentage finally achieved with total-N （TN） load of 46.52 mg/（L.d）, in which Arthrospira platensis was successfully grown. The main compositions of the obtained biomass are close to those in Zarrouk medium. Thus, it is possible to culture Arthrospiraplatensis in nitrified human urine for food production within bioregenerative life support systems （BLSSs）.

Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils

The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carried out at 60%WHC(water holding capacity)and 25℃to evaluate the gross N transformation rates and N_(2)O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province,China.The results showed that the gross rates of N mineralization,immobilization,and nitrification were 3.60,1.90,and 5.63 mg N/(kg·d)in silt loam soil,respectively,which were 3.62,4.26,and 3.13 times those in sandy loam soil,respectively.The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia)in sandy loam soil and silt loam soil were all higher than 1.00,whereas the n/ia in sandy loam soil(4.36)was significantly higher than that in silt loam soil(3.08).This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil,and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_(3)–leaching.Under aerobic conditions,both nitrification and denitrification made contributions to N_(2)O emissions.Nitrification was the dominant pathway leading to N_(2)O production in soils and was responsible for 82.0%of the total emitted N_(2)O in sandy loam soil,which was significantly higher than that in silt loam soil(71.7%).However,the average contribution of denitrification to total N_(2)O production in sandy loam soil was 17.9%,which was significantly lower than that in silt loam soil(28.3%).These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.

Nitrogen source and fate of typical orchard with gentle slope in semi-arid areas

Excessive nitrogen (N) exports caused by human activities are one of the main reasons for the numerous environmental problems in agricultural production. Orchards, as an essential part of agricultural production, play a crucial role in rural economic development and ecological environment construction. Understanding the migration pathways of N in orchards is significant for the scientific management of orchards and the reduction of environmental pollution. In this research, the source and fate of N in a typical orchard in Beijing were quantitatively analyzed. N management strategies were proposed in combination with agricultural production habits. The total N input into the orchard was 487.19 kg/hm^(2)·a, of which 85.44%, 10.99%, 3.30% and 0.27% of N input were from fertilizer application, atmospheric deposition, biological N fixation and pesticide, respectively. A large amount of N fertilizer application was the primary source of N input in the orchard. For the N fate, the N surplus in the soil could reach up to 68.40% of total N inputs, and only 20.16% were absorbed and utilized by plants. The amount of N losses through ammonia volatilization, runoff and sediment, nitrification and denitrification accounted for 10.68%, 0.39% and 0.37%, respectively. N input in the orchard mainly remained in soil, while N loss was mainly through ammonia volatilization. There were 176.72, 99.00, and 57.52 kg/hm^(2)·a N surplus in 0-40 cm, 40-80 cm, and over 80 cm soil layers, respectively. To deal with the N accumulation on the soil surface and the migration of N from the soil surface to the deep layer of orchards, reducing N fertilizer application, substituting circular furrow for the whole orchard fertilization, adjusting irrigation schedule by reducing the amount of single irrigation, increasing the frequency of irrigation to three times in the normal year, and adopting efficient water-saving irrigation technology are realizable methods.

Assessment of Nitrogen Pollutant Sources in Surface Waters of Taihu Lake Region

The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.

N pollution sources and denitrification in waterbodies in Taihu Lake region

Herein presented are the researches of the past few years related to characteristics of N pollution of waterbodies and N transport from croplands to the waterbodies in Suzhou and Wuxi regions, the center of the Taihu Lake valley. Based on the types of waterbodies, concentrations ofinorganic N of different forms, concentrations of PO_4^(3-), δ15NH4 values in river and lake waterbodies,the pollution sources of N in the river, lake and well waters are distinguished, and comparisons are made of trend of variation and amplitude of concentration between years, seasons and N pollutants in waterbodies. The increase in N2O concentration in different waterbodies and high δ15NO_3^(-)value in different waterbodies are deemed as an evidence of the existence of denitrification in the river, lake and well waters. Moreover, the role of denitrification in the waterbodies plays in stabilizing chronically concentration of N as pollutant in the waterbodies and mitigating N load in the waterbodies.

Parasitic source resistance at different temperatures for AlGaN/AlN/GaN heterostructure field-effect transistors

The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） and current–voltage（I–V） characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field（PCF） scattering exhibits a significant impact on RSat the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.

Effects of nitrogen specification and culture method on growth of Enteromorpha prolifera

Eutrophication, which is the enrichment of a water mass with inorganic and organic nutrients that support plant growth, is a key factor in stimulating phytoplankton growth. In this study, we determined the effects of various nitrogen sources, different nitrogen concentrations in the culture medium, and two culture methods on the growth of the green alga, Enteromorpha prolifera. The relationship between the specific growth rate of E. prolifera and NO3-N concentration was consistent with that estimated using the Monod equation （R2=0.9713, P〈0.01）. In the N O3-N medium, the maximum specific growth rate was calculated to be 0.1634/d and the semi-saturation constant was calculated to be 16.86 μmol/L. Our results show that E. prolijkra can effectively utilize NH4^＋-N, NO3^-N, and NO^2-N and urea-N in the range of 5 to 50 μmol/L. NH4^＋-N was preferentially assimilated by E. prolifera, and urea-N was favorable for long-term growth.

Behaviour of Potassium and Trace Elements in Rhizosphere of Flue-Cured Tobacco (Nicotiana Tabacum L.)

The study on the behaviourof potassium, phosphate and trace elements, Fe, Mn, Cu and Zn, in the rhizosphere of different varieties of flue-cured tobacco (Nicotiana tabacum L.) with high and low potassium application rate with rhizobag technique showed that soil available K, soil available P, and slow available K was in depletion status, whereas DTPA extractable Fe, Mn, Zn and Cu accumulated obviously in rhizosphere. The depletion and accumulation rates of mineral nutrients differed in degree with K application rate, soil type, and tobacco variety. The content of a vailable K in both rhizosphere and bulk soil and K concentration in tobacco leaf increased significantly, and the available P in rhizosphere dropped with more K applicatin. The DTPA-Fe content of red soil much lower in pH was higher than that of calcareous soil in bulk soil. But the DTPA-Fe content of calcareous soil was much higher than that of red soil in rhizosphere, which was considered perhaps to be mainly related to releasing of Fe phytosiderophore. Nitrate could increase depletion of available K in rhizosphere and also soil pH in comparison with ammonium.

Effect of Carbon and Nitrogen Availability on Metabolism of Amino Acids in Germinating Spores of Arbuscular Mycorrhizal Fungi

The effects of carbon （C） and nitrogen （N） sources on N utilization and biosynthesis of amino acids were examined in the germinating spores of the arbuscular mycorrhizal （AM） fungus Glomus intraradices Schenck ＆ Smith after exposure to various N substrates, CO2, glucose, and/or root exudates. The N uptake and de novo biosynthesis of amino acids were analyzed using stable isotopic labeling with mass spectrometric detection. High-performance liquid chromatography-based analysis was used to measure amino acid levels. In the absence of exogenous N sources and in the presence of 25 mL L^-1 CO2, the germinating AM fungal spores utilized internal N storage as well as C skeletons derived from the degradation of storage lipids to biosynthesize the free amino acids, in which serine and glycine were produced predominantly. The concentrations of internal amino acids increased gradually as the germination time increased from 0 to 1 or 2 weeks. However, asparagine and glutamine declined to the low levels; both degraded to provide the biosynthesis of other amino acids with C and N donors. The availability of exogenous inorganic N （ammonium and nitrate） and organic N （urea, arginine, and glutamine） to the AM fungal spores using only CO2 for germination generated more than 5 times more internal free amino acids than those in the absence of exogenous N. A supply of exogenous nitrate to the AM fungal spores with only CO2 gave rise to more than 10 times more asparagine than that without exogenous N. In contrast, the extra supply of exogenous glucose to the AM fungal spores generated a significant enhancement in the uptake of exogenous N sources, with more than 3 times more free amino acids being produced than those supplied with only exogenous CO2. Meanwhile, arginine was the most abundant free amino acid produced and it was incorporated into the proteins of AM funsal spores to serve as an N storage compound.

The contribution of microorganisms and metazoans to mineral nutrition in bromeliads

Aims One critical challenge for plants is to maintain an adequate nutrient supply under fluctuating environmental conditions.This is particularly true for epiphytic species that have limited or no access to the pedosphere and often live in harsh climates.Bromeliads have evolved key innovations such as epiphytism,water-absorbing leaf trichomes,tank habit and Crassulacean acid metabolism(CAM)photosynthesis that enable them to survive under various environmental conditions.Bromeliads encompass diverse ecological types that live on different substrates(they can be terrestrial,epilithic or epiphytic)and vary in their ability to retain water(they can be tank-forming or tankless)and photosynthetic pathway(i.e.C3 or CAM).In this review,we outline the nutritional modes and specializations that enable bromeliads to thrive in a wide range of nutrient-poor(mostly nitrogen-depleted)environments.Important FindingsBromeliads have evolved a great diversity of morphologies and functional adaptations leading to the existence of numerous nutritional modes.Focusing on species that have absorptive foliar trichomes,we review evidence that bromeliads have evolved multi-faceted nutritional strategies to respond to fluctuations in the supply of natural nitrogen(N).These plants have developed mutualistic associations with many different and functionally diverse terrestrial and aquatic microorganisms and metazoans that contribute substantially to their mineral nutrition and,thus,their fitness and survival.Bacterial and fungal microbiota-assisted N provisioning,protocarnivory,digestive mutualisms and myrmecotrophic pathways are the main strategies used by bromeliads to acquire nitrogen.The combination of different nutritional pathways in bromeliads represents an important adaptation enabling them to exploit nutrient-poor habitats.Nonetheless,as has been shown for several other vascular plants,multiple partners are involved in nutrient acquisition indicating that there have been convergent adaptations to nutrient scarcity.Finally,we point out some gaps in the current knowledge of bromeliad nutrition that offer fascinating research opportunities.

Erratum:Measurement of(n,α)and(n,2n)reaction cross sections at a neutron energy of 14.92±0.02 MeV for potassium and copper with uncertainty propagation,[A.Gandhi,Aman Sharma,Rebecca Pachuau et al.,Chin.Phys.C 46,014002(2022)]

Experimentally measured neutron activation cross sections are presented for the^(65)Cu(n,α)^(62m)Cu,^(41)K(n,α)^(38)Cl,and^(65)Cu(n,2n)^(64)Cu reactions with detailed uncertainty propagation.The neutron cross sections were measured at an incident energy of 14.92±0.02 MeV,and the neutrons were based on the t(d,n)αfusion reaction.The^(27)Al(n,α)^(24)Na reaction was used as a reference reaction for the normalization of the neutron flux.The pre-calibrated lead-shielded HPGe detector was used to detect the residues'γ-ray spectra.The data from the measured cross sections are compared to the previously measured cross sections from the EXFOR database,theoretically calculated cross sections using the TALYS and EMPIRE codes,and evaluated nuclear data.

Symbionts in Mucuna pruriens stimulate plant performance through nitrogen fixation and improved phosphorus acquisition

Aims South Africa is mainly dominated by savanna and grasslands ecosystems which have been previously reported to be acidic and nutrient deficient,specifically with regard to phosphorus(P)and nitrogen(N).Mucuna pruriens(L.)DC,commonly known as velvet bean,is an indigenous legume in most African countries and has been reported to withstand these adverse soil conditions.The legume is used in many countries of the world for their medicinal value as well as for soil fertilization purposes.Although there are reports on M.pruriens growth and establishment in nutrient stressed ecosystems,no investigation has been conducted on M.pruriens symbiotic interactions,N source preference and associated growth carbon costs when subjected to P deficiency.In this study,we determined the impact of microbial symbionts on N nutrition and growth carbon costs of M.pruriens under P deficiency.Methods Microbe inoculation soils were collected from four geographical distinct KwaZulu-Natal locations.Thereafter,seeds were germinated in these natural soils and in early stages of nodule development,then seedlings were transferred in sterile quartz sand and supplied with Long Ashton nutrient media with varying P concentrations.Important Findings The 16S RNA sequence results revealed that M.pruriens was nodulated by Burkholderia sp.,Paenibacillus sp.and Bacillus irrespective of P concentrations.Even though P deficiency resulted in decreased overall biomass/growth,the root biomass,nodule number and carbon costs increased.In addition,low P supplied saplings showed the highest arbuscular mycorrhiza fungi percentage root colonization.In M.pruriens,nitrogen derived from atmosphere had a positive correlation with P level and the saplings had a dual reliance on atmospheric derived N and soil derived N with increased reliance on soil N in low P supplied plants.Therefore,M.pruriens exhibited different morphological and microbial symbiosis when subjected to P deficiency.

Measurement of(n,α)and(n,2n)reaction cross sections at a neutron energy of 14.92±0.02 MeV for potassium and copper with uncertainty propagation

Experimentally measured neutron activation cross sections are presented for the ^(65)Cu(n,0)^(62m)Cu,^(41) K(n,a)^(38C)l,and ^(65)Cu(n.2n)^(64)Cu reactions with detailed uncertainty propagation.The neutron cross secions were measured at an incident energy of 14.92±0.02 MeV,and the neutrons were based on the(d,n)a fusion reaction.The ^(27) Al(n,a)^(24)Na reaction was used as a reference reaction for the normalization of the neutron flux.The pre-calib-rated lead-shielded HPGe detector was used to detect the residues'γ-ray spetra.The data from the measured cross sections are compared to the previously measured cross sections from the EXFOR database,theoretically calculated cross sections using the TALYS and EMPIRE codes,and evaluated nuclear data.

Systematic study of the(n,2n)reaction cross section for^(121)Sb and^(123)Sb isotopes

The cross sections of the^(121)Sb(n,2n)^(120)Sb^(m) and ^(123)Sb(n,2n)^(122)Sb reactions were measured at 12.50,15.79 and 18.87 MeV neutron energies relative to the standard ^(27)Al(n,α)^(24)Na monitor reaction using neutron activation and offline γ-ray spectrometry.Irradiation of the samples was performed at the BARC-TIFR Pelletron Linac Facility,Mumbai,India.The quasi-monoenergetic neutrons were generated via the ^(7)Li(p,n)reaction.Statistical model calculations were performed by nuclear reaction codes TALYS(ver.1.9)and EMPIRE(ver.3.2.2)using various input parameters and nuclear level density models.The cross sections of the ground and the isomeric state as well as the isomeric cross section ratio were studied theoretically from reaction threshold to 26 MeV energies.The effect of pre-equilibrium emission is also discussed in detail using different theoretical models.The present measured cross sections were discussed and compared with the reported experimental data and evaluation data of the JEFF-3.3,ENDF/B-VIII.0,JENDL/AD-2017 and TENDL-2019 libraries.A detailed analysis of the uncertainties in the measured cross section data was performed using the covariance analysis method.Furthermore,a systematic study of the(n,2n)reaction cross section for^(121)Sb and^(123)Sb isotopes was also performed within 14-15 MeV neutron energies using various systematic formulae.This work helps to overcome discrepancies in Sb data and illustrate a better understanding of pre-equilibrium emission in the(n,2n)reaction channel.