The first heavy ion fusion–evaporation reaction study for 74Ge has been performed through the reaction channel Zn70(Li7,2np)Ge74 at beam energies of 30 and 35 MeV. Previously known yrast band is extended to higher spins and five new collective bands are established. Based on comparison with the neighboring 72,76Ge isotopes, an intermediate pattern of energy staggering S(I) is observed in the γ band of 74Ge. The collective structure of 74Ge, including the excitation energies and transition probabilities of ground-state band and γ band, is reproduced by the state-of-the-art five-dimensional collective Hamiltonian (5DCH) model constructed from the covariant density functional. By including the 72,76,78Ge isotopes, systematical investigation of the structure evolution in Ge isotopes is performed. Based on the systematic comparisons and analysis, the triaxial evolution with spin in 74Ge is revealed and 74Ge is found to be the crucial nucleus marking the triaxial evolution from soft to rigid in Ge isotopes.
β-decay studies of neutron-rich nuclei in and around the "island of inversion" have been performed. With a systematic investigation of half-lives for the isotonic chains from N=19 to 22, conspicuous kinks observed at Z=13 provide a clear signature of a boundary on the northern (high-Z) side of the island. Based on the comparison with shell model calculations using Gogny D1S and SDPF-M interactions, a newly determined 22+ state in 34Si at 4519 keV presents an experimental evidence of triaxiality in this region and sheds more light on the structure of the transition across the northern boundary of the island.
Freshwater green algae Chlorella vulgaris was selected as an adsorbent, and a simple, rapid, economical and environmentally friendly method for the detection of heavy metal Cd in water samples based on preconcentration with C. vulgaris combined with energy dispersive X-ray fluorescence (EDXRF) spectrometry was proposed. Chlorella vulgaris could directly and rapidly adsorb Cd 2+ without any pretreatment, and the maximum adsorption efficiency could be obtained when the contact time was 1 min with an optimal pH of 10. The obtained Cd-enriched thin samples after preconcentration with C. vulgaris by suction filtration of reaction solution had very good uniformity, which could be directly measured by EDXRF spectrometry, and the net integral fluorescence intensity of Cd K α characteristic peak had a very good linear relationship with the initial concentration of Cd in the range of 0.703–74.957 µg ml −1 with a correlation coefficient of 0.9979. When the Cd thin samples with a Cd-enriched region of 15.1 mm in diameter were formed by the developed preconcentration method with suction filtration of 10 ml reaction solution, the detection limit of this method was 0.0654 µg ml −1 , which was lower than the maximum allowable discharge concentration of Cd in various industrial wastewaters. The proposed method was simple to operate, and could effectively remove the influence of matrix effect of water samples and effectively improve the sensitivity and stability of EDXRF spectrometry directly detecting heavy metals in water samples, which was successfully applied to detect Cd in real water samples with satisfactory results, and the recoveries ranged from 94.80% to 116.94%. Moreover, this method can be applied to the rapid detection and early warning of excessive Cd in discharged industrial wastewaters. This work will provide a methodological basis for the development of rapid and online monitoring technology and instrument of heavy metal pollutants in water.
Abstract To better understand the amendment effects and mechanisms of aluminum (Al(III)) phytotoxicity mitigation by different regional crop straw biochars, wheat seedling root elongation trials were conducted. The contributions of liming effect, oxygen-containing surface functional group adsorption, and oxyanions precipitation to Al(III) phytotoxicity mitigation by Ca(OH) 2 , pristine and ash-free canola straw biochar were evaluated. The results indicated that biochars derived from canola straw collected from four different regions (Yingtan, Xuancheng, Nanjing, and Huaiyin) caused 22–70% wheat seedling root elongation, which might be linked to liming effect. Incorporation of the corresponding ash-free biochars caused 15–30% elongation, which could be attributed to the surface functional group adsorption. About 0–60% of changes could be explained by Al(III) precipitation with inorganic oxyanions. These findings provide new insights into the physicochemical properties, potential applications, efficiencies, and underlying mechanisms of crop straw biochar in alleviating Al(III) phytotoxicity, which is dependent on the cultivation soil, and indicate similar application of crop straw biochar for acidic soil amelioration, contaminated soil remediation, and arable soil improvement. Graphical Abstract
The heavy ion fusion–evaporation reaction study for the high-spin spectroscopy of 75As has been performed via the reaction channel 70Zn(9Be, 1p3n)75As at a beam energy of 42 MeV. The collective structure especially a dipole band in 75As is established for the first time. The properties of this dipole band are investigated in terms of the self-consistent tilted axis cranking covariant density functional theory. Based on the theoretical description and the examination of the angular momentum components, this dipole band can be interpreted as a novel stapler band, where the valence neutrons in (1g9/2) orbital rather than the collective core are responsible for the closing of the stapler of angular momentum.
Excited states of the odd–odd nucleus 74As have been investigated via heavy ion fusion evaporation reaction Zn70(Li7,3n)As74 at beam energy of 30 MeV. The properties of the positive- and the negative- parity bands can be interpreted in terms of the Cranked Nilsson–Strutinsky (CNS) model calculations which show that the observed bands are built on the triaxial deformed shape. The inversion of the favored and unfavored signature branches observed in the positive-parity bands presents at high spins rather than normal signature inversion occurs at low spins. This phenomenon may be explained as the origin of unpaired band crossing in a highly rotating triaxial nucleus.
We report for the first time the discrimination of the core fragment knockout and valence nucleon knockout reaction mechanisms at medium energy range, by the use of the recoil proton tagging technique. Intense 8He beams at 82.3 MeV/u were supplied by the RIPS beam line at RIKEN, and impinged on both hydrogen and carbon targets. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The core fragment knockout mechanism is identified through the polar angle correlation and checked by various kinematics relations. This mechanism may be used to extract the cluster structure information of unstable nuclei. On the other hand, with the selection of the tagged valence nucleon knockout mechanism, a narrower peak of 7He ground state is obtained. The extracted neutron spectroscopic factor Sn=0.512(18) is relatively smaller than the no-tagged one, and is in good agreement with the prediction of ab initio Green's function Monte Carlo calculations.
The roots of 4 japonica, 4 indica, and 7 hybrid rice varieties were obtained by hydroponic experiment and used to explore the relationship between charge characteristics and exchangeable manganese(II) (Mn(II)) on rice roots and Mn(II) absorption in roots and shoots of the rice. Results indicated Mn(II) adsorbed on rice roots mainly existed as exchangeable Mn(II) after 2 h. The roots of indica and hybrid rice carried more negative charges than the roots of japonica rice. Accordingly, this led to more exchangeable Mn(II) to be adsorbed on roots of indica and hybrid rice after 2 h and more Mn(II) absorbed in the roots of the same varieties after 48 h. However, this was contrary to the result of Mn(II) absorption in rice shoots after 48 h. Coexisting cations of K+, Na+, Ca2+, and Mg2+ reduced the exchangeable Mn(II) on rice roots through their competition with Mn(II) for sorption sites on rice roots, which led to the decrease in Mn(II) absorption in rice roots and shoots. Ca2+ and Mg2+ showed a greater decrease in the Mn(II) absorbed in roots and shoots than K+ and Na+. The reduction of Mn(II) absorption in the roots of indica rice and hybrid rice induced by Ca2+ and Mg2+ was more than that of japonica rice. This was attributed to more negative charges on the roots of the former than the latter. Therefore, the absorption of Mn(II) by rice roots was determined by surface charge properties and exchangeable Mn(II) on the rice roots. The results suggested that Ca2+ and Mg2+ have potential to alleviate Mn(II) toxicity to rice.
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