The remarkably high superconducting transition temperature and upper critical field of iron(Fe)-based layered superconductors, despite ferromagnetic material base, open the prospect for superconducting electronics. However, success in superconducting electronics has been limited because of difficulties in fabricating high-quality thin films.We report the growth of high-quality c-axis-oriented cobalt(Co)-doped SrFe 2 As 2 thin films with bulk superconductivity by using an in-situ pulsed laser deposition technique with a 248-nm-wavelength KrF excimer laser and an arsenic(As)-rich phase target. The temperature and field dependences of the magnetization showing strong diamagnetism and transport critical current density with superior J c -H performance are reported.These results provide necessary information for practical applications of Fe-based superconductors. \pacs{} The classes of Iron (Fe)-based superconductors [1][2][3][4][5][6][7][8] have remarkably high superconducting transition temperatures (T c ) in spite of the ferromagnetic material base; the highest T c is 55 K in LnFeAsO (FeAs-1111, Ln = lanthanide) [2] and 37.5 K in AEFe 2 As 2 (FeAs-122, AE = alkaline-earth element) [7]. The zero-temperature upper critical field (H c2 (0)) was found to be up to 65 T in the FeAs-1111 [9]. The discovery of these new classes of superconductors has regenerated interest in superconductivity because of an opportunity to tune these materials in many ways [10,11]. This potentially allows one to reveal the mechanism of high-temperature superconductors.Ever since discovering these compounds, much progress has been made in measuring the fundamental physical properties in order to understand the superconducting mechanism. However, controversy still exists because the measurements were carried out on bulk polycrystals, except for some works on single crystals [8,[12][13][14][15][16]. Highquality thin films are needed to investigate the physical properties and to develop superconducting electronic devices, such as Josephson junctions. However, controlling the stoichiometry of the FeAs-1111 phase is difficult because the crystal structure contains two different anions [17]. Also, in the FeAs-1111 phase, electrons are doped by partially replacing oxygen ions with fluorine (F), which is easily evaporated in a vacuum chamber at a high temperature because of its very high vapor pressure. These reasons make it difficult to fabricate high-quality thin film [17][18][19].Very recently, Hosono et al. reported success in growing cobalt (Co)-doped SrFe 2 As 2 thin film [18,19]. Even though this compound has a relatively lower T c , Codoping is more suitable for thin film growth than other types of doping (F or potassium (K)) because of the low vapor pressure of Co. Also, SrFe 2 As 2 contains only one anion species. Hosono et al. fabricated the thin films by using pulsed laser deposition (PLD) with a second-harmonic 532-nm-wavelength Nd:YAG laser and a stoichiometric target disk.In general, an ultraviolet (UV) wavelength is known ...
PurposeParanasal sinus mucocele is a benign, expansile mass which can occur as a result of trauma or spontaneous obstruction of a sinus tract. The purpose of this study was to describe and compare the clinical characteristics of primary mucoceles occurring in patients with no previous sinus surgery history or known cause of mucoceles and secondary mucoceles resulting as a complication following endoscopic sinus surgery or the Caldwell-Luc operation.Materials and MethodsWe performed a retrospective chart review of 33 cases of primary mucoceles and 60 cases of secondary mucoceles which were diagnosed and surgically corrected between 1996 and 2008.ResultsThe most common presenting symptoms in primary mucoceles were nasal obstruction (19.4%) and rhinorrhea (17.7%). In secondary mucoceles, the most common symptoms were cheek pain (31.7%) and nasal obstruction (18.3%). The most common origins of primary mucoceles were the ethmoid sinus (45.5%) and the maxillary sinus (18.2%). In secondary mucoceles, the maxillary sinus was the most common site (86%), followed by the ethmoid sinus (7.1%). All patients with secondary mucoceles had a history of sinus surgery.ConclusionThe maxillary sinus was the most common site of secondary mucoceles while the ethmoid sinus was the most common origin of primary mucoceles. Cases of secondary mucoceles that occurred following sinus endoscopic surgery developed more frequently in the ethmoid sinus than in those following the Caldwell-Luc procedure, therefore, we suggest that the incidence of maxillary sinus mucoceles in the Asian population would decrease as the rate of endoscopic sinus surgery increases.
The first objective of this study was to discuss the applicability of the CO2/CH4 ratio method in order to assess CH4 oxidation efficiency. To achieve this objective, a comparison between CO2/CH4 ratios and the mass balance method was conducted. The second objective of this study was to estimate the CH4 oxidation efficiency in an interim landfill soil cover and assess how a CH4 influx influences the CH4 oxidation efficiency. The results showed that despite the CO2 problems brought by respiration, the CH4 oxidation efficiencies obtained by the CO2/CH4 ratio method led to similar results compared to the mass balance method. In this respect, the CO2/CH4 ratio method can be an indicator of the CH4 oxidation efficiencies for landfill cover soils. The CH4 oxidation efficiencies derived in this study through the CO2/CH4 ratio method ranged between 46% and 64%, and between 41% and 62% through the mass balance method. The results imply that the Intergovernmental Panel on Climate Change's (IPCC) default value of 10% for the CH4 oxidation efficiency is an underestimation for landfill cover soils. CH4 oxidation efficiency tends to be negatively correlated with CH4 influx. Therefore, CH4 influx reaching a landfill cover should be limited in order to increase the CH4 oxidation efficiency.
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