Search

ZMT04 muscovite serves as a quality control reference material for K--Ar dating, with a recommended age of 1804 ± 21 Ma (2σ). Here, we check the homogeneity for ZMT04 muscovite and compare its age against the reference material Fish Canyon sanidine (FCs). Five sub-samples of ZMT04 muscovite were irradiated in three different reactors with different irradiation doses, analysed at varying sample masses over different time periods, and subjected to different mass spectrometric measurement procedures in two independent laboratories, which yielded consistent plateau ages with a mean of 1772.2 ± 2.7 Ma (2σ, MSWD = 1.30, and P = 0.18) and RFCs=28.294±0.072Ma ZMT04 = 105.53 ± 0.25 (2sd, MSWD = 0.88, and P = 0.57). The single-grain results are consistent with the multi-grain stepwise heating results, indicating good reproducibility and homogeneity of 40Ar* and K at the single-grain level. A single grain is sufficient to yield a high precision result when the J-value >0.01. We recommend 1 mg as the minimum sample mass to yield enough neutron-induced 39Ar signals for high-precision analysis (J-value <0.001). Accordingly, ZMT04 muscovite can represent a reliable 40Ar/ 39Ar dating and K--Ar dating reference material for Paleoproterozoic geological samples. [ABSTRACT FROM AUTHOR]

Background Reconstruction of cervicofacial scarring continues to present challenges for surgical treatment. Here we present our clinical experience in repairing cervicofacial scarring using pre-expanded thoracodorsal artery perforator flaps. Methods From January 2007 to December 2012, 15 patients were treated for severe cervicofacial scarring. In the first surgical stage, expanders were implanted subcutaneously in the zone nourished by thoracodorsal artery perforators. The expansion generally took 3 to 6 months. In the second surgical stage, the cervicofacial cicatricial contracture was released and the secondary defect was covered with local flaps. The remaining wound was covered by the free thoracodorsal artery perforator expanded flap, which was anastomosed to the facial vascular bundle. The donor site was closed directly in all the patients. Results The postoperative follow-up time ranged from 1 to 5 years. The deformities were corrected, all flaps survived completely and none were bulky. Themaximum length of the flaps was 32 cm (mean, 22.4 ± 4.2 cm), and the maximum width was 17 cm (mean, 14.4 ± 2.2 cm). All patients exhibited recovery of neck movement, and there was no recurrence of neck contracture. Conclusion The pre-expanded thoracodorsal artery perforator flap is an ideal method for reconstruction of severe cervicofacial cicatricial contracture. [ABSTRACT FROM AUTHOR]