[en] Background: Fission product gas accumulation in Tri-structural iso-tropic (TRISO) coated fuel particles can cause the failure of TRISO fuel elements. Purpose: The aim is to study the fission product gases (xenon and krypton) accumulation in UO_2 and ThO_2 coated particles with respect to various neutron spectra and neutron flux, Methods: Calculations were conducted using ORIGEN code with the neutron databases of THERMAL.LIB, BWRU.LIB, CANDUSEU.LIB and PWRU.LIB as input. Results: It was found that, with the same neutron spectrum, neutron flux and running time, the production of xenon is about 7 times of that of krypton in the UO_2 coated particles, and about 4.5 times in the ThO_2 coated particles. For the ThO_2 coated particles, both xenon and krypton reach saturation earlier when the neutron spectrum are softer, and the saturation values are smaller compared with those in the harder spectrum environment. Conclusion: Taking the fission product gas accumulation as the main factor of TRISO coated particles, the calculation implies that the ThO_2 coated particles can have a longer lifetime than the UO_2 coated particles under the same neutron environment. (authors)

[en] Background and purpose: To evaluate the prognostic value of gross primary tumor volume (GTV-P) in nasopharyngeal carcinoma (NPC) patients treated with intensity modulated radiotherapy (IMRT). Methods and materials: A total of 694 nonmetastatic and histologically proven NPC patients who underwent IMRT were retrospectively reviewed. Samples were split randomly into a training set (n = 232) and a test set (n = 462) to analysis. The receiver operating characteristic (ROC) curves were calculated to identify the cut-off point and test the prognostic validity of the GTV-P. The correlations between GTV-P and the American Joint Committee on Cancer (AJCC) disease stages were also analyzed. Results: The 5-year disease-free survival (DFS), overall survival (OS), local relapse-free survival (LRFS) and distant metastasis-free survival (DMFS) rates for NPC patients with GTV-P < 19 vs. ⩾19 ml were 94.9% vs. 64.8%, 97.0% vs. 76.4%, 98.2% vs. 92.5% and 97.1% vs. 75.2%, respectively (all P < 0.05) in all patients. Multivariate analysis indicated GTV-P was an independent prognostic factor. The ROC curve verified that the predictive ability of T classifications was improved when combined with GTV-P (P < 0.001). Conclusions: GTV-P is an independent prognostic indicator for treatment outcome after IMRT, and significantly improves the prognostic validity of T classifications in NPC.

[en] We use THz time-domain spectroscopy to investigate the far-infrared properties of vanadium dioxide thin films, strain-engineered through epitaxial growth on (100)_R TiO₂ substrates. The films exhibit a large uniaxial tensile strain along the rutile c-axis. X-ray diffraction measurements reveal a structural transition temperature of 340 K, whereas independent THz conductivity measurements yield a metal–insulator transition temperature of 365 K along c_R. Analysis of these results suggests a Mott–Hubbard behavior along the c_R-axis. Along c_R the conductivity is approximately 5500 (Ω cm)⁻¹, comparable to bulk single crystals. The tensile strain leads to remarkably uniform cracking oriented along the rutile c-axis, resulting in a large conductivity anisotropy in our single-crystal epitaxial thin films. We discuss our results in the context of previous measurements and calculations of the properties of VO₂, under different strain conditions. This work demonstrates the potential of strain engineering to tune the properties of complex materials while also serving as a powerful discriminatory tool for probing microscopic responses. (paper)

[en] In this study, ferromagnetic MnAl films were prepared by alternating Al/Mn quasi-monolayer deposition using a novel biased target ion beam deposition (BTIBD) technique. XRD results showed that the magnetic τ phase was well formed in MnAl thin films (∼10 nm), which grew epitaxially on single crystal MgO (001) substrates. The optimized saturation magnetization was ∼394 emu/cc. Furthermore, we observed a thickness-dependent uniaxial anisotropy in ferromagnetic MnAl films, which was attributed to the change of the tetragonal lattice distortion as a function of film thickness. The relationship between the film thicknesses and saturation magnetizations suggested the existence of a magnetically dead layer ∼2.7 nm with an extrapolated saturation moment around 523 emu/cc (∼1.90 μ_B/Mn). This value has exceeded the experimental value in bulk materials and is close to the theoretically predicted magnetization (∼1.975 μ_B/Mn).

[en] Ge_1-xMn_x thin films with an average Mn concentration of 0.64 at. % were fabricated through Mn ion implantation into crystalline germanium-on-insulator wafers. Implantation damage was removed and crystallinity restored by pulsed laser melting from a single 30-ns 308-nm XeCl⁺ excimer laser pulse. Resolidified films demonstrated higher Curie temperatures but smaller saturation magnetizations than those of both as-implanted films and implanted films subjected to rapid thermal annealing. These findings are attributed to the redistribution of Mn during solidification.

[en] Amorphous Ge_1-xMn_x thin films have been prepared by co-depositing Ge and Mn on SiO₂/Si using an ultrahigh vacuum molecular beam epitaxy system. Across a range of growth temperatures and Mn concentrations (2.8 at. %, 10.9 at. %, and 21.3 at. %), we achieved enhanced magnetic and electrical properties with non-magnetic codopants dispersed in the films. Self-assembled Mn-rich amorphous nanostructures were observed in the amorphous Ge matrix, either as isolated nanoclusters or as nanocolumns, depending on Mn concentration. The ferromagnetic saturation moments were found to increase with Mn concentration and reached a maximum of 0.7 μ_B/Mn in the as-grown samples. Two magnetic transition temperatures around 15 K and 200 K were observed in these amorphous MBE-grown samples. Coercivity is considered within the context of local magnetic anisotropy. The anomalous Hall effect confirmed a strong correlation between the magnetization and transport properties, indicating that global ferromagnetic coupling was carrier-mediated rather than through direct exchange. In addition, negative magnetoresistance was detected from 5 K to room temperature.

[en] For the clinical application of bone tissue engineering with the combination of biomaterials and mesenchymal stem cells (MSCs), bone scaffolds should possess excellent biocompatibility and osteoinductivity to accelerate the repair of bone defects. Herein, strontium hydroxyapatite [SrHAP, Ca_10−xSr_x(PO₄)₆(OH)₂]/chitosan (CS) nanohybrid scaffolds were fabricated by a freeze-drying method. The SrHAP nanocrystals with the different x values of 0, 1, 5 and 10 are abbreviated to HAP, Sr1HAP, Sr5HAP and Sr10HAP, respectively. With increasing x values from 0 to 10, the crystal cell volumes and axial lengths of SrHAP become gradually large because of the greater ion radius of Sr²⁺ than Ca²⁺, while the crystal sizes of SrHAP decrease from 70.4 nm to 46.7 nm. The SrHAP/CS nanohybrid scaffolds exhibits three-dimensional (3D) interconnected macropores with pore sizes of 100–400 μm, and the SrHAP nanocrystals are uniformly dispersed within the scaffolds. In vitro cell experiments reveal that all the HAP/CS, Sr1HAP/CS, Sr5HAP/CS and Sr10HAP/CS nanohybrid scaffolds possess excellent cytocompatibility with the favorable adhesion, spreading and proliferation of human bone marrow mesenchymal stem cells (hBMSCs). The Sr5HAP nanocrystals in the scaffolds do not affect the adhesion, spreading of hBMSCs, but they contribute remarkably to cell proliferation and osteogenic differentiation. As compared with the HAP/CS nanohybrid scaffold, the released Sr²⁺ ions from the SrHAP/CS nanohybrid scaffolds enhance alkaline phosphatase (ALP) activity, extracellular matrix (ECM) mineralization and osteogenic-related COL-1 and ALP expression levels. Especially, the Sr5HAP/CS nanohybrid scaffolds exhibit the best osteoinductivity among four groups because of the synergetic effect between Ca²⁺ and Sr²⁺ ions. Hence, the Sr5HAP/CS nanohybrid scaffolds with excellent cytocompatibility and osteogenic property have promising application for bone tissue engineering. - Highlights: • We fabricate strontium hydroxyapatite/chitosan nanohybrid scaffolds. • Ca₅Sr₅(PO₄)₆(OH)₂ nanocrystals in scaffolds enhance osteogenic differentiation. • 3D interconnected macropores improve cell adhesion and spreading. • Nanohybrid scaffold has a great potential for bone tissue engineering.

[en] Purpose: To subclassify patients with the T4 classification nasopharyngeal carcinoma (NPC), according to the seventh edition of the American Joint Committee on Cancer staging system, using magnetic resonance imaging (MRI), and to evaluate the prognostic value of subclassification after intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 140 patients who underwent MRI and were subsequently histologically diagnosed with nondisseminated classification T4 NPC received IMRT as their primary treatment and were included in this retrospective study. T4 patients were subclassified into two grades: T4a was defined as a primary nasopharyngeal tumor with involvement of the masticator space only; and T4b was defined as involvement of the intracranial region, cranial nerves, and/or orbit. Results: The 5-year overall survival (OS) rate and distant metastasis-free survival (DMFS) rate for T4a patients (82.5% and 87.0%, respectively), were significantly higher than for T4b patients (62.6% and 66.8%; p = 0.033 and p = 0.036, respectively). The T4a/b subclassification was an independent prognostic factor for OS (hazard ratio = 2.331, p = 0.032) and DMFS (hazard ratio = 2.602, p = 0.034), and had no significant effect on local relapse-free survival. Conclusions: Subclassification of T4 patients, as T4a or T4b, using MRI according to the site of invasion, has prognostic value for the outcomes of IMRT treatment in NPC.