The Qehan Lake Basin (QLB) and its system of lakes are located in a marginal monsoon zone and are extremely sensitive to global climate change. In this paper, using aerial photographs from different periods, in addition to MSS, TM, and ETM images, and combining these with regional topographic maps, we analyze lake area changes from 1958 to 2010 and the relation between Qehan Lake (QL) and climate variability. Our results indicate that there was a relatively high lake level in 1959, when the area and volume of the lake were 118.9 km2 and 151.9 × 106 m3, respectively, but this level was subject to a shrinking trend until 2010, when the lake area was only 28.1 km2, and the water volume was 41.1 × 106 m3. West Qehan Lake (WQL) has experienced severe water shrinkage and lake level fluctuation. In 1958, WQL was 80.2 km2 in area and 124.1 × 106 m3 in volume. However, due to a rapid decrease in precipitation and increases in both temperature and evaporation, it began to dry up in 2002. The WQL Water area decreased by 1.82 km2/a, and the lake level declined by 7 m during 1958–2002, so it became an ephemeral lake.
Background Whether routine lymph node dissection for early endometrial cancer is beneficial to survival is still controversial. However, surgeons usually perform lymph node dissection on all patients with early endometrial cancer. This study aimed to prove that the risk of lymph node metastasis, as defined by our standard, is very low in such patients and may change the current surgical practice. Methods 36 consecutive patients who had staged surgery for endometrial cancer were collected. All eligible patients meet the following very low risk criteria for lymph node metastasis, including: (1) preoperative diagnosis of endometrial cancer (preoperative pathological diagnosis), (2) tumors confined to the uterine cavity and not beyond the uterine body, (3) PET-MRI lymph node metastasis test is negative. PET-MRI and pathological examination were used to assess the extent and size of the tumor, the degree of muscular invasion, and lymph node metastasis. Results The median age at diagnosis was 52 years (range 35–72 years). The median tumor size on PET-MRI was 2.82 cm (range 0.66–6.37 cm). Six patients underwent robotic surgery, 20 underwent laparoscopic surgery, 8 underwent Laparoscopic-assisted vaginal hysterectomy, and 2 underwent vaginal hysterectomy. 23% (63.9%) patients had high-grade (i.e. 2 and 3) tumors. Among the 36 patients who underwent lymph node sampling, the median number of lymph nodes retrieved was 32 (range 9–57 nodules). No patient (0%) was diagnosed with lymph node metastasis. According to the policy of each institution, 8 patients (22.2%) received adjuvant therapy, and half of them also received chemotherapy (4 patients; 50%). Conclusions None of the patients who met the criteria had a pathological assessment of lymph node metastasis. Omitting lymph node dissection may be reasonable for patients who meet our criteria.
The crystal structure, mechanical anisotropy, elastic properties and electronic characteristics, as well as the stability, of P4/m BN are predicted by means of density functional theory. In this work, BN in the P4/m phase demonstrates mechanical and dynamical stability. Compared with the values of bulk B, E and G in the P4/m phase, the B of BN in the P4/m phase is greater than that of dz4 BN, while the G and E of P4/m BN are greater than those of Pnc2 BN and dz4 BN. The ratio of the bulk-to-shear modulus for P4/m BN is less than 1.75 and dz4 BN, dz2 BN and lzlz2 BN, indicating that P4/m BN is more brittle than dz4 BN, dz2 BN and lzlz2 BN. P4/m BN exhibits stronger mechanical anisotropy in G and E than Pbca BN, P42/mnm BN and Pm-3m BN but much weaker mechanical anisotropy than P4/mbm BN, B7N7, B11N11 and B15N15. In addition, P4/m BN is a quasi-direct bandgap semiconductor, and the difference between the direct and the indirect bandgap is 0.008 eV. In order to obtain further characteristics of P4/m BN for future synthetic verification, the X-ray diffraction (XRD) patterns for P4/m BN are also calculated. Given its properties, P4/m BN is a good candidate for photoelectric devices.
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