34 research outputs found
Comparison of crystal structures and effects of Co substitution in a new member of Fe-1111 superconductor family AeFeAsF(Ae = Ca and Sr): a possible candidate for higher Tc superconductor
We refined crystal structures of newly found members of the Fe-1111
superconductor family, CaFe\_{1-x}Co\_{x}AsF and SrFe\_{1-x}Co\_{x}AsF (x = 0,
0.06, 0.12) by powder synchrotron X-ray diffraction analysis. The tetragonal to
orthorhombic phase transitions were observed at ~120 K for unsubstituted
CaFeAsF and at ~180 K for unsubstituted SrFeAsF, the transition temperatures
agreeing with kinks observed in temperature-dependent resistivity curves.
Although the transition temperature decreases, the structural phase transitions
were observed below 100 K in both samples of x = 0.06, and finally they were
suppressed in the doping level of x = 0.12. The refined structures reveal that
distortions of the FeAs4 tetrahedron from the regular tetrahedron likely
originate from mismatches in atomic radii among the constituent elements. In
this system, the enlarged FeAs4 tetrahedron resulting from larger radius of Sr
than that of Ca is flattened along a-b plane, whereas the smaller radius of Ca
makes the tetrahedron closer to regular one, and their characteristic shapes
are further enhanced by Co substitution. These results suggest that the CaFeAsF
compound is a promising candidate for higher-Tc superconductor.Comment: 17 pages, 8 figures, 2 tables, Supplementary information is included
at the end of the documen
Electronic and Magnetic Phase Diagram of a Superconductor, SmFeAsO1-xFx
A crystallographic and magnetic phase diagram of SmFeAsO1-xFx is determined
as a function of x in terms of temperature based on electrical transport and
magnetization, synchrotron powder x-ray diffraction, 57Fe Mossbauer spectra
(MS), and 149Sm nuclear resonant forward scattering (NRFS) measurements. MS
revealed that the magnetic moments of Fe were aligned antiferromagnetically at
~144 K (TN(Fe)). The magnetic moment of Fe (MFe) is estimated to be 0.34
myuB/Fe at 4.2 K for undoped SmFeAsO; MFe is quenched in superconducting
F-doped SmFeAsO. 149Sm NRFS spectra revealed that the magnetic moments of Sm
start to order antiferromagnetically at 5.6 K (undoped) and 4.4 K (TN(Sm)) (x =
0.069). Results clearly indicate that the antiferromagnetic Sm sublattice
coexists with the superconducting phase in SmFeAsO1-xFx below TN(Sm), while
antiferromagnetic Fe sublattice does not coexist with the superconducting
phase.Comment: Accepted in New Journal of Physic
Successful management of tracheo-innominate artery fistula with endovascular stent graft repair
AbstractTracheo-innominate artery fistula is a highly lethal complication after tracheostomy. A 37-year-old man who had undergone a tracheostomy 14 years earlier because of dysphagia after brain surgery had a tracheo-innominate artery fistula with exsanguinating hemorrhage from his tracheostomy site. After temporary control of the bleeding, a stent graft was implanted in the innominate artery through the brachial artery. The patient recovered uneventfully and remained well 14 months after the procedure, with no sign of infection. Endovascular stent grafting may be the treatment of choice for patients with tracheo-innominate artery fistula. (J Vasc Surg 2001;33:1280-2.
Genome Sequence of Striga asiatica Provides Insight into the Evolution of Plant Parasitism
Parasitic plants in the genus Striga, commonly known as witchweeds, cause major crop losses in sub-Saharan Africa and pose a threat to agriculture worldwide. An understanding of Striga parasite biology, which could lead to agricultural solutions, has been hampered by the lack of genome information. Here, we report the draft genome sequence of Striga asiatica with 34,577 predicted protein-coding genes, which reflects gene family contractions and expansions that are consistent with a three-phase model of parasitic plant genome evolution. Striga seeds germinate in response to host-derived strigolactones (SLs) and then develop a specialized penetration structure, the haustorium, to invade the host root. A family of SL receptors has undergone a striking expansion, suggesting a molecular basis for the evolution of broad host range among Striga spp. We found that genes involved in lateral root development in non-parasitic model species are coordinately induced during haustorium development in Striga, suggesting a pathway that was partly co-opted during the evolution of the haustorium. In addition, we found evidence for horizontal transfer of host genes as well as retrotransposons, indicating gene flow to S. asiatica from hosts. Our results provide valuable insights into the evolution of parasitism and a key resource for the future development of Striga control strategies.Peer reviewe
Iliopsoas Muscle Hematoma Secondary to Alcoholic Liver Cirrhosis
Iliopsoas muscle hematoma in a patient with alcoholic liver cirrhosis is rarely seen, however it has a high mortality. Thus we should cautiously make a diagnosis and treatment. This is the case of a 60-year-old male. He had a 15-year history of alcoholic liver disease and emphysema. He presented with low back pain after a fall that had happened 2 months before. Due to persistent back pain, he went to see a local physician who, after detailed examination, suspected rupture of bilateral common iliac artery aneurysms and transferred the patient to our hospital. The same presumptive diagnosis was made, and on this basis, an aortic bifemoral Y-graft was implanted. He developed aspiration pneumonia and hepatic and renal dysfunction postoperatively, which led to multiple organ failure and subsequent in-hospital death on postoperative day 62. This was believed to be a case of iliopsoas muscle hematoma developed in a patient with liver cirrhosis, and considering it was a case with poor surgical risk, a conservative treatment option such as transcatheter arterial embolization should also have been considered. Although iliopsoas muscle hematoma with alcoholic liver cirrhosis is rare, an appropriate treatment plan should be determined on a case-by-case basis despite its poor prognosis