Using field-angle, temperature, and back-gate-voltage dependence of the weak anti-localization (WAL) and universal conductance fluctuations of thin Bi1.5Sb0.5Te1.7Se1.3 topological-insulator single crystals, in combination with gate-tuned Hall resistivity measurements, we reliably separated the surface conduction of the topological nature from both the bulk conduction and topologically trivial surface conduction. We minimized the bulk conduction in the crystals and back-gate tuned the Fermi level to the topological bottom-surface band while keeping the top surface insensitive to back-gating with the optimal crystal thickness of ∼100 nm. We argue that the WAL effect occurring by the coherent diffusive motion of carriers in relatively low magnetic fields is more essential than other transport tools such as the Shubnikov-de Hass oscillations for confirming the conduction by the topologically protected surface state. Our approach provides a highly coherent picture of the surface transport properties of TIs and a reliable means of investigating the fundamental topological nature of surface conduction and possible quantum-device applications related to momentum-locked spin polarization in surface states.

Abstract:Energy storage systems are increasingly gaining importance with regard to their role in achieving load levelling, especially for matching intermittent sources of renewable energy with customer demand, as well as for storing excess nuclear or thermal power during the daily cycle. Compressed air energy storage (CAES), with its high reliability, economic feasibility, and low environmental impact, is a promising method for large-scale energy storage. Although there are only two large-scale CAES plants in existence, recently, a number of CAES projects have been initiated around the world, and some innovative concepts of CAES have been proposed. Existing CAES plants have some disadvantages such as energy loss due to dissipation of heat of compression, use of fossil fuels, and dependence on geological formations. This paper reviews the main drawbacks of the existing CAES systems and presents some innovative concepts of CAES, such as adiabatic CAES, isothermal CAES, micro-CAES combined with air-cycle heating and cooling, and constant-pressure CAES combined with pumped hydro storage that can address such problems and widen the scope of CAES applications, by energy and exergy analyses. These analyses greatly help us to understand the characteristics of each CAES system and compare different CAES systems. OPEN ACCESS

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PurposeNewly developed extra-mammary multiple primary cancers (MPCs) are an issue of concern when considering the management of breast cancer survivors. This study aimed to investigate the prevalence of MPCs and to evaluate the implications of MPCs on the survival of breast cancer patients.Materials and MethodsA total of 8204 patients who underwent surgery at Severance Hospital between 1990 and 2012 were retrospectively selected. Clinicopathologic features and survival over follow-up periods of ≤5 and >5 years were investigated using univariate and multivariate analyses.ResultsDuring a mean follow-up of 67.3 months, 962 MPCs in 858 patients (10.5%) were detected. Synchronous and metachronous MPCs were identified in 23.8% and 79.0% of patients, respectively. Thyroid cancer was the most prevalent, and the second most common was gynecologic cancer. At ≤5 years, patients with MPCs were older and demonstrated significantly worse survival despite a higher proportion of patients with lower-stage MPCs. Nevertheless, an increased risk of death in patients with MPCs did not reach statistical significance at >5 years. The causes of death in many of the patients with MPCs were not related to breast cancer. Stage-matched analysis revealed that the implications of MPCs on survival were more evident in the early stages of breast disease.ConclusionBreast cancer patients with MPCs showed worse survival, especially when early-stage disease was identified. Therefore, it is necessary to follow screening programs in breast cancer survivors and to establish guidelines for improving prognosis and quality of life.

Background Nipple-sparing mastectomy (NSM), followed by immediate reconstruction (IR) of the breast, has become a preferred surgical procedure with good cosmesis results and patient satisfaction. However, nipple-areolar complex (NAC) ischemia and necrosis remain major problems after NSM and IR. Methods We retrospectively analyzed patients who underwent NSM and IR at Gangnam Severance Hospital from January 2009 to June 2018. We compared the patient characteristics and complication rate among three different incisions (inframammary fold [IMF], radial, periareolar). Additionally, we identified the risk factors of NAC necrosis. Results Data from 290 eligible breasts in 275 patients were analyzed. Patients with IMF incision had relatively lower breast weights. The overall complication rate was the highest with periareolar incision and the lowest with IMF incision (42.6% vs. 18.8%, p < 0.001). The rate of NAC ischemia or necrosis was significantly different among the three incisions (9.7%, 17.0%, and 31.1% in IMF, radial, and periareolar, respectively; p < 0.001). Moreover, surgical treatments were more frequently needed in patients with periareolar incision. Periareolar incision, short distance from the tumor to the nipple base, and large breast weight were independent risk factors of NAC ischemia or necrosis in multivariable analysis. Conclusions Compared with IMF incision, periareolar incision was associated with higher incidences of surgical complications and NAC necrosis. Careful consideration is needed when planning NSM in patients with a large breast volume or a tumor close to the nipple.