Reconstruction of Hydraulic Fractures Using Passive Ultrasonic Travel-Time Tomography

The knowledge of hydraulic fracture morphology is significant for the analysis of fracture mechanisms. This paper utilizes passive Ultrasonic Travel-time Tomography (UTT) to characterize the hydraulic fracture. We constructed a velocity model based on X-ray computerized tomography (X-CT) images scanned on a real hydraulically fractured shale column. Then, ray-paths and travel times corresponding to the source-receiver configuration were calculated by curved ray-tracing schemes. Lastly, we performed tomographic inversions using total variation regularization (TVR). The simulation results showed that 3D passive UTT based on TVR is an accurate, efficient, and stable method to reconstruct the velocity structures with fractures, even in the case of sparse ray-coverage or high noise level. Meanwhile, we also verified that the passive UTT is a valid alternative to X-CT in depicting the hydraulic fracturing rock via a proper interpretation method

Thick lead-free ferroelectric films with high Curie temperatures through nanocomposite-induced strain

Ferroelectric materials are used in applications ranging from energy harvesting to high-power electronic transducers1. However, industry-standard ferroelectric materials contain lead, which is toxic and environmentally unfriendly2. The preferred alternative, BaTiO3, is non-toxic and has excellent ferroelectric properties, but its Curie temperature of ~130 °C is too low to be practical3. Strain has been used to enhance the Curie temperature of BaTiO3 (ref. 4) and SrTiO3 (ref. 5) films, but only for thicknesses of tens of nanometres, which is not thick enough for many device applications. Here, we increase the Curie temperature of micrometre-thick films of BaTiO3 to at least 330 °C, and the tetragonal-to-cubic structural transition temperature to beyond 800 °C, by interspersing stiff, self-assembled vertical columns of Sm2O3 throughout the film thickness. The columns, which are 10 nm in diameter, strain the BaTiO3 matrix by 2.35%, forcing it to maintain its tetragonal structure and resulting in the highest BaTiO3 transition temperatures so far

Transperitoneal vs retroperitoneal laparoscopic radical nephrectomy: a double-arm, parallel-group randomized clinical trial

Abstract Objective To compare the outcomes of patients undergoing Retroperitoneal laparoscopic Radical nephrectomy (RLRN) and Transperitoneal laparoscopic Radical nephrectomy (TLRN). Methods A total of 120 patients with localized renal cell carcinoma were randomized into either RLRN or TLRN group. Mainly by comparing the patient perioperative related data, surgical specimen integrity, pathological results and tumor results. Results Each group comprised 60 patients. The two group were equivalent in terms of perioperative and pathological outcomes. The mean integrity score was significantly lower in the RLRN group than TLRN group. With a median follow-up of 36.4 months after the operation, Kaplan–Meier survival analysis showed no significant difference between RLRN and TLRN in overall survival (89.8% vs. 88.5%; P = 0.898), recurrence-free survival (77.9% vs. 87.7%; P = 0.180), and cancer-specific survival (91.4% vs. 98.3%; P = 0.153). In clinical T2 subgroup, the recurrence rate and recurrence-free survival in the RLRN group was significantly worse than that in the TLRN group (43.2% vs. 76.7%, P = 0.046). Univariate and multivariate COX regression analysis showed that RLRN (HR: 3.35; 95%CI: 1.12–10.03; P = 0.030), male (HR: 4.01; 95%CI: 1.07–14.99; P = 0.039) and tumor size (HR: 1.23; 95%CI: 1.01–1.51; P = 0.042) were independent risk factor for recurrence-free survival. Conclusions Our study showed that although RLRN versus TLRN had roughly similar efficacy, TLRN outperformed RLRN in terms of surgical specimen integrity. TLRN was also significantly better than RLRN in controlling tumor recurrence for clinical T2 and above cases. Trial registration Chinese Clinical Trial Registry ( https://www.chictr.org.cn/showproj.html?proj=24400 ), identifier: ChiCTR1800014431, date: 13/01/2018

Additional file 1 of Transperitoneal vs retroperitoneal laparoscopic radical nephrectomy: a double-arm, parallel-group randomized clinical trial

Additional file 1: Supplementary Table 1. Univariate and multivariate analysis of recurrence-free survival in patients with clinical T2 stage RCC