Design of simulated-gas calibration source and self-attenuation correction methods for radioactive noble gas measurement with HPGe detector.

In this study, to achieve accurate measurement of radioactive noble gas and enhance the precision of efficiency calibration, a relatively low-cost and low-density simulated-gas calibration source (SGCS) was produced from polyurethane foam with a density of ρ = 0.098 g cm-3. Using SGCS with a Marinelli beaker geometry, the efficiency calibration was applied to a BE5030, 50.5% relative efficiency HPGe detector in an energy range of 59.54 keV∼1836.06 keV. Then, taking the 81 keV gamma-ray emitted by 133Xe as an example, due to the density difference between the SGCS and the 133Xe gas sample, it is necessary to correct for self-attenuation effects. Therefore, a semi-empirical function for self-attenuation correction was established by using LabSOCS software and XCOM. Upon validation, the relative deviation of efficiency calibration values between the SGCS and the LabSOCS of 133Xe under the density of 0.001 g cm-3 to 0.01 g cm-3 was about 3%. After using the self-attenuation correction method established in this study, the results verified a good consistency of the efficiency calculated by SGCS and LabSOCS software.

Radon adsorption and air purification by Spanish moss (Tillandsia usneoides) and its metabolic response to radon exposure.

The capacity of Spanish moss (Tillandsia usneoides), an aerial plant, to adsorb radon (Rn) and absorb CO2 was assessed to analyze its capacity to remove pollutants from indoor air and to determine its radon (Rn) tolerance mechanism. Transcriptomics and metabolomics techniques were used to analyze the response of the plant to Rn exposure. Spanish moss absorbed indoor CO2 at night using the type of photosynthesis termed crassulacean acid metabolism. The CO2 absorption efficiency of the plant was mainly affected by the light duration and diurnal temperature differences. The highest purification efficiency was 48.25%, and the scales on the Spanish moss leaf surface were the key sites for Rn adsorption. Metabolome analysis showed that Rn exposure induced differential metabolites significantly enriched in the metabolism of lipids, amino acids, nucleotides, and carbohydrates. Transcriptome analysis showed significantly upregulated expression levels of functional genes in Rn-exposed leaves. Rn had significant effects on respiratory metabolism, as indicated by upregulated expression of metabolites and functional genes related to the glycolysis pathway, pyruvate oxidation, tricarboxylic acid cycle, and oxidative phosphorylation pathway. These responses indicated that the internal mechanism by which Spanish moss alleviates Rn stress involves an enhancement of cellular energy supplies and regulation of respiratory metabolic pathways to allow adaptation to Rn pollution.

Stability and superfluidity of the Bose-Einstein condensate in a two-leg ladder with magnetic field.

The stability and superfluidity of the Bose-Einstein condensate in two-leg ladder with magnetic field are studied. The dispersion relation and the phase diagram of the system are obtained. Three phases are revealed: the Meissner phase, the biased ladder (BL) phase, and the vortex phase. The dispersion relation and phase transition of the system strongly depend on the magnitude of atomic interaction strength, the rung-to-leg coupling ratio and the magnetic flux. Particularly, the change of the energy band structure in the phase transition region is modified significantly by the atomic interaction strength. Furthermore, based on the Bogoliubov theory, the energetic and dynamical stability of the system are invested. The stability phase diagram in the full parameter space is presented, and the dependence of superfluidity on the dispersion relation is illustrated explicitly. The atomic interaction strength can produce dynamical instability in the energetic unstable region and can expand the superfluid region. The results show that the stability of the system can be controlled by the atomic interaction strength, the rung-to-leg coupling ratio and the magnetic flux. In addition, the excitation spectrums in the Meissner phase, BL phase and vortex phase are further studied. The modulation of the excitation spectrum and the energetic stability of the system by the atomic interaction strength, the rung-to-leg coupling ratio and magnetic flux is discussed. Finally, through the numerical simulation, the dynamical instability of the system is verified by the time evolution of the Bloch wave and rung current. This provides a theoretical basis for controlling the superfluidity of the system.

Ground-state phase and superfluidity of tunable spin-orbit-coupled Bose-Einstein condensates.

We theoretically study the ground-state phases and superfluidity of tunable spin-orbit-coupled Bose-Einstein condensates (BECs) under the periodic driving of Raman coupling. An effective time-independent Floquet Hamiltonian is proposed by using a high-frequency approximation, and we find single-particle dispersion, spin-orbit-coupling, and asymmetrical nonlinear two-body interaction can be modulated effectively by the periodic driving. The critical Raman coupling characterizing the phase transition and relevant physical quantities in three different phases (the stripe phase, plane-wave phase, and zero momentum phase) are obtained analytically. Our results indicate that the boundary of ground-state phases can be controlled and the system will undergo three different phase transitions by adjusting the external driving. Interestingly, we find the contrast of the stripe density can be enhanced by the periodic driving in the stripe phase. We also study the superfluidity of tunable spin-orbit-coupled BECs and find the dynamical instability can be tuned by the periodic driving of Raman coupling. Furthermore, the sound velocity of the ground-state and superfluidity state can be controlled effectively by tuning the periodic driving strength. Our results indicate that the periodic driving of Raman coupling provides a powerful tool to manipulate the ground-state phase transition and dynamical instability of spin-orbit-coupled BECs.

Localization and spin dynamics of spin-orbit-coupled Bose-Einstein condensates in deep optical lattices.

We analytically and numerically discuss the dynamics of two pseudospin components Bose-Einstein condensates (BECs) with spin-orbit coupling (SOC) in deep optical lattices. Rich localized phenomena, such as breathers, solitons, self-trapping, and diffusion, are revealed and strongly depend on the strength of the atomic interaction, SOC, Raman detuning, and the spin polarization (i.e., the initial population difference of atoms between the two pseudospin components of BECs). The critical conditions for the transition of localized states are derived analytically. Based on the critical conditions, the detailed dynamical phase diagram describing the different dynamical regimes is derived. When the Raman detuning satisfies a critical condition, localized states with a fixed initial spin polarization can be observed. When the critical condition is not satisfied, we use two quenching methods, i.e., suddenly and linearly quenching Raman detuning from the soliton or breather state, to discuss the spin dynamics, phase transition, and wave packet dynamics by numerical simulation. The sudden quenching results in a damped oscillation of spin polarization and transforms the system to a new polarized state. Interestingly, the linear quenching of Raman detuning induces a controllable phase transition from an unpolarized phase to an expected polarized phase, while the soliton or breather dynamics is maintained.

Effects of Jitai tablet, a traditional Chinese medicine, on plasma adrenocorticotropic hormone and cortisol levels in heroin addicts during abstinence.

OBJECTIVES: To investigate the changes in adrenocorticotropic hormone (ACTH) and cortisol in heroin addicts given Jitai tablet treatment during abstinence. DESIGN: Double-blind, randomized, placebo-controlled clinical trial. SETTINGS/LOCATION: Drug Rehabilitation Bureau of Shanghai Police, China. PARTICIPANTS: 99 volunteers, including 69 heroin addicts and 30 healthy volunteers. INTERVENTIONS: 69 heroin addicts randomly divided into two groups: the Jitai tablet group, which comprised 34 heroin addicts given Jitai tablet treatment during abstinence, and the placebo group, which comprised 35 heroin addicts given placebo. A control group consisted of 30 sex- and age-matched healthy volunteers. OUTCOME MEASURES: ACTH and cortisol in plasma were measured in all groups at baseline and in the Jitai tablet and placebo groups on the third, seventh, and 14th days of abstinence. RESULTS: Levels of both ACTH (p<.01) and cortisol (p<.001) were significantly higher in heroin addicts at baseline than in the healthy volunteers. Jitai tablet treatment restored plasma cortisol levels to normal more rapidly than did placebo treatment (p<.05), but not ACTH levels. A positive correlation between ACTH and cortisol values at baseline (p<.01) was also found with withdrawal symptom scores and daily dosages of heroin. CONCLUSIONS: Heroin addicts could respond to Jitai tablets through changes in the hypothalamus-pituitary-adrenal axis.