[en] In high-temperature quark-gluon plasma and its subsequent hadronic matter created in a high-energy nucleus-nucleus collision, the quark-antiquark potential depends on the temperature. The temperature-dependent potential is expected to be derived from the free energy obtained in lattice gauge theory calculations. This requires one to study the relationship between the quark-antiquark potential and the quark-antiquark free energy. When the system's temperature is above the critical temperature, the potential of a heavy quark and a heavy antiquark almost equals the free energy, but the potential of a light quark and a light antiquark, of a heavy quark and a light antiquark and of a light quark and a heavy antiquark is substantially larger than the free energy. When the system's temperature is below the critical temperature, the quark-antiquark free energy can be taken as the quark-antiquark potential. This allows one to apply the quark-antiquark free energy to study hadron properties and hadron-hadron reactions in hadronic matter. (authors)

[en] Objective: To evaluate the methods and clinical value of mammary sentinel lymphoscintigraphy in breast cancer. Methods: 117 patients with breast tumor in stage T_1-2N₀ were examined before sentinel node biopsy were considered. Some of them were compared in different injection volume at both side and several cases with SPECT/CT tomographic fusions. 13 patients were subdermally injected with 55.5 MBq (0.5 ml) ⁹⁹Tc^m-DTPA-human serum albumin (HSA) on the surface of the lesion, 50 patients with 92.5 MBq (4 ml) unfiltered ⁹⁹Tc^m-sulfur colloid (SC) in four divided doses around the lesion and 54 patients in the upper part of the lesion with the same volume of the SC in one-point-injection. Results: The sentinel lymph node (SLN) could quickly be shown by any of three methods but the best time of view and number of lymph nodes differed personly and mainly affected by injection depth and volume. It was showed that the 3rd method could find more juxtaclavicular, supraclavicular and internal mammary nodes. SLN were successfully identified in 69.2% with HSA in 30 min and over 84% with SC in 2 h. SPECT/CT tomographic fusions were more helpful to recognize SLN and abnormal lymphatic drainage. Conclusion: The mammary sentinel lymphoscintigraphy in breast cancer is differ from past lymphatic imaging and is essential for localizing SLN correctly, identifying abnormal lymphatic drainage and designing new therapeutic regime

[en] Highlights: • The decrease disturbances of different parameters are applied to the boundary. • Dryout and transient heat transfer of once-through steam generator are simulated. • Movable boundaries of each heat transfer region of secondary side are considered. • Sensitivities of dryout and transient heat transfer performance are investigated. - Abstract: A transient mathematical model is developed based on the distributed-parameter method by dividing the heat transfer regions of the secondary side of the once-through steam generator into single-phase preheating region, subcooled boiling region, nucleate boiling region, liquid deficient region (also known as post-dryout region) and single-phase superheating region in present work. And then it is used to simulate dryout phenomenon and transient heat transfer of the once-through steam generator. The results show that the developed mathematical model and method can be used to reasonably predict dryout phenomenon and transient heat transfer performance at different loads of the once-through steam generator. The heat transfer coefficient of the secondary side decreases sharply when dryout occurs, correspondingly the wall temperature shows a soaring trend and the maximum rising amplitude within present operating range is about 23 °C. The reduction of inlet enthalpy and mass flow rate of the primary side of the once-through steam generator both lead to a reduction of the outlet steam superheat and a downstream movement of the dryout point. The steam at the outlet cannot reach the superheating condition when the inlet enthalpy of the primary side decreases by 5%. The decrease of the inlet enthalpy of the secondary side within current range has little effect on the overall heat transfer performance, while the decrease of the mass flow rate of the secondary side leads to the upstream displacement of the dryout point and a rising outlet steam temperature.

[en] An effective method to improve the irradiation resistance of austenitic stainless steels is adding oversized solutes into steels. In this work, the irradiation resistances of two type of modified 310S steels, in one of which Zr was added and in another Nb, Ta, and W were added, were investigated by proton irradiations at 563 K. Irradiation induced vacancy-type defects was characterized with positron annihilation spectroscopy (PAS), while dislocation loops and bubbles whose size are greater than 1 nm are characterized with transmission electron microscopy (TEM). It is found that the relative S parameter ΔS/S extracted from PAS is more effective than S parameter in evaluating the quantity of vacancy-type defects. It was revealed from ΔS/S that more vacancy-type defects produced in (Nb, Ta, W)-added steels than that in Zr-added steels, and this trend became more obvious with the dose increasing. S-W curves reveal that proton irradiation induced two kinds of vacancy-type defects, i.e. vacancy clusters and proton-vacancy clusters. TEM observation shows that the density of small bubbles induced by proton in (Nb, Ta, W)-added steels is much higher than that in Zr-added steels. Both $\frac{1}{3}$ 1 1 1 and $\frac{1}{2}$ 1 1 0 dislocation loops were observed with TEM in all of the specimens. The mean size and number density of dislocation loops in (Nb, Ta, W)-added steels are slightly larger than that in Zr-added steels, and increased with increasing irradiation dose. Both PAS and TEM observations shows that irradiation damage in Zr-added steels is less serious than that (Nb, Ta, W)-added steels, and the possible mechanisms are discussed through the enhancement of point defect recombination by oversized solute atoms.

[en] Highlights: • Direct and clear observation of hydrogen bubbles evolution by TEM is provided. • The role of temperature playing in bubble formation and evolution is fully explored. • Vacancy trapping mechanism is verified in this experiment. - Abstract: In order to see how hydrogen is behaving in tungsten and to understand the way bubbles form and grow up, specimens were irradiated by hydrogen ions from room temperature to 800 °C to fluence of 2.25 × 10²¹ m⁻². Experimental results show that higher temperature helped bubble acquire higher internal pressure, causing interstitial loop punching to happen. In this process bubbles’ size grew and dislocation loops were formed but dislocation loops migrated away at and above 350 °C. And bubble number density reached peak value at 600 °C but then dropped dramatically at 800 °C. Because continuously increasing temperature would cause small bubbles dissolution or leaking out. Besides, high temperature also prevented tiny bubbles growing to be visible under TEM observation by their reaching equilibrium pressure before reaching threshold pressure for loop punching. In the other set of experiments, specimens were irradiated by low hydrogen fluence of 1 × 10²⁰ m⁻² at 600 °C, in which case few hydrogen bubbles appeared. With further increasing irradiation fluence, bubble number density quickly increased. Small bubbles tended to coalesce to become larger visible bubbles. And they continued to grow through loop punching until their internal pressure cannot support their size expansion any more

[en] Highlights: • Different responses of cavities to temperature variation have been observed in two modified 310S steels. • It is found that it is easier for Ta and Nb to precipitate under irradiation compared with W and Zr in 310S steels. • A simple model is built to understand the observed phenomena. -- Abstract: The effects of oversized additive atoms on microstructure evolution in 310S stainless steel under irradiation was investigated. Ar ion irradiations were conducted on modified 310S stainless steels at 290 °C and 550 °C. SC-1 was modified with Zr and SC-2 was modified with Nb, Ta and W. Compared with SC-2, lower density, smaller vacancy clusters formed in SC-1 at 290 °C. When irradiation temperature was increased from 290 °C to 550 °C, the average size of vacancy clusters increased while the number density dropped to a lower value in SC-1; however, in SC-2, the average size and number density of vacancy clusters shifted to larger values. At 550 °C, lower density and larger size of vacancy clusters were observed in SC-1 compared with that in SC-2. In addition, precipitates enriched with Ni were observed in SC-1, while Nb- and Ta-enriched precipitates were found in SC-2. A possible mechanism is discussed.

[en] Highlights: • Dose dependence of RIS at grain boundary in AL-6XN was characterized by TEM with EDX. • High concentration of retained hydrogen can broaden the region of RIS near grain boundaries. • An abnormal phenomenon was found that the degree of RIS increased with decreasing irradiation temperature. - Abstract: The effect of high concentration of hydrogen on the segregation of radiation-induced segregation (RIS) in AL-6XN stainless steels has been investigated by transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy. Specimens were irradiated with 100 keV H₂⁺ ions from 1 dpa to 5 dpa at 380 °C to investigated the dose dependence of grain boundary RIS. A specimen was irradiated to 5 dpa at 290 °C to study the effect of irradiation temperature. The trends of Cr depletion and Ni enrichment with irradiation dose is similar to that of other austenitic steels reported in the literatures, but the higher concentration of hydrogen made the RIS profile wider. An abnormal phenomenon that the degree of RIS increased with decreasing irradiation temperature was found, indicating that with the retention of hydrogen in the steels, temperature dependence of RIS is dominated by the quantity of retained hydrogen, rather than by thermal segregation processes.

[en] Bubbles induced by single-ion (He or H) and sequential-ion (H/He or He/H) irradiation in tungsten were investigated using transmission electron microscopy (TEM). Specimens were irradiated with 12 keV He⁺ and 6.7 keV H⁺ under different fluences at 600 °C. Bubbles were observed after single He⁺ irradiation. And then bubbles grew larger with the increasing of the fluence of post-irradiated H⁺ under sequential He/H condition. Post-implanted H⁺ might make bubbles grow larger. For sequential H/He conditions, the size of bubbles changed little while the number density of bubbles grew significantly compared with single He⁺ irradiation condition. Pre-implanted H⁺ might enhance bubbles nucleated. The size of bubbles was smaller while the density was larger compared with sequential He/H irradiation condition at the same fluence. Possible explanations were discussed in this paper.

[en] Dislocation loops induced by single (He or H) ion beam and sequential (H/He or He/H) ion beam irradiation in reduced activation martensitic steels were investigated with transmission electron microscopy (TEM). Specimens were irradiated with 30 keV He⁺ and 18 keV H⁺ respectively under three different doses at 450 °C. Dislocation loops with mean size of 41.3 nm were observed under single He ion beam irradiated to 0.1 dpa. Sequential ion irradiation could induce larger dislocation loops than the case of single ion irradiation. It was interesting that mean size of dislocation loops induced by He/H sequential ion irradiation was larger than that induced by H/He sequential ion irradiation at the same dose. Possible explanations were presented and synergistic effects of He and H on dislocation loops were discussed.

[en] Single-beam and sequential-beam irradiations were performed to investigate the H/He synergistic effect on dislocation loops in reduced-activation ferritic/martensitic (RAFM) steels. The irradiations were carried out with 10 keV H"+, 18 keV He"+ and 160 keV Ar"+, alone and in combination at 723 K. He"+ single-beam irradiation induced much larger dislocation loops than that induced by both H"+ and Ar"+ single-beam irradiation. H"+ post-irradiation after He"+ irradiation further increased the size of dislocation loops, whilst He"+ post-irradiation or Ar"+ post-irradiation following H"+ irradiation only slightly increased the size of dislocation loops. The experiment results indicate that pre-implanted H"+ can drastically inhibit the growth while post-implanted H"+ can significantly enhance the growth of dislocation loops induced by He"+ irradiation. The mechanisms behind the complex synergistic phenomena between H and He and the different roles that H and He played in the growth of dislocation loops are discussed.