Unconventional Fermi surface in an insulating state Tan, B. S.; Hsu, Y.-T.; Zeng, B. ...
Science (American Association for the Advancement of Science),
07/2015, Letnik:
349, Številka:
6245
Journal Article
Recenzirano
Odprti dostop
Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of ...an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. The quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.
The search for a Fermi surface in the absence of a conventional Fermi liquid has thus far yielded very few potential candidates. Among promising materials are spin-frustrated Mott insulators near the ...insulator–metal transition, where theory predicts a Fermi surface associated with neutral low-energy excitations. Here we reveal another route to experimentally realize a Fermi surface in the absence of a Fermi liquid by the experimental study of a Kondo insulator SmB6 positioned close to the insulator–metal transition. We present experimental signatures down to low temperatures (≪1 K) associated with a Fermi surface in the bulk, including a sizeable linear specific heat coefficient, and on the application of a finite magnetic field, bulk magnetic quantum oscillations, finite quantum oscillatory entropy, and substantial enhancement in thermal conductivity well below the charge gap energy scale. Thus, the weight of evidence indicates that despite an extreme instance of Fermi liquid breakdown in Kondo insulating SmB6, a Fermi surface arises from novel itinerant low-energy excitations that couple to magnetic fields, but not weak DC electric fields.
To determine the identity and context of genes conferring antibiotic resistance in a sporadic multiply antibiotic-resistant Acinetobacter baumannii recovered at Royal Children's Hospital, Brisbane.
...The antibiotic resistance phenotype for 23 antibiotics was determined using disc diffusion or MIC determination. The whole-genome sequence of RCH51 was determined using the Illumina HiSeq platform. Antibiotic resistance determinants were identified using ResFinder. Plasmids were recovered by transformation.
Isolate RCH51 belongs to the uncommon STs ST103 IP (7-3-2-1-7-1-4) and ST514 OX (1-52-29-28-18-114-7). It was found to be resistant to sulfamethoxazole, tetracycline, gentamicin, tobramycin and kanamycin and also exhibited reduced susceptibility to imipenem (MIC 2 mg/L) and meropenem (MIC 6 mg/L). RCH51 carries the oxa235 , sul2 , floR , aadB and tet39 resistance genes, all located on plasmids. The largest of the three plasmids, pRCH51-3, is 52 789 bp and carries oxa235 in the ISAba1-bounded transposon Tn 6252 , as well as sul2 and floR . pRCH51-3 represents a new A. baumannii plasmid family that is potentially conjugative as it contains several genes predicted to encode transfer functions. However, conjugation of pRCH51-3 was not detected. The aadB and tet39 resistance genes were each found in small plasmids identical to the known plasmids pRAY*-v1 and pRCH52-1, respectively.
The resistance gene complement of RCH51 was found in three plasmids. pRCH51-3, which carries the oxa235 , sul2 and floR resistance genes, represents a new, potentially conjugative A. baumannii plasmid type.
Abstract
The nature of the Fermi surface observed in the recently discovered family of unconventional insulators starting with SmB
6
is a subject of intense inquiry. Here we shed light on this ...question by accessing quantum oscillations in the high magnetic field-induced metallic regime above ≈47 T in YbB
12
, which we compare with the unconventional insulating regime. In the field-induced metallic regime, we find prominent quantum oscillations in the electrical resistivity characterised by multiple frequencies and heavy effective masses. The close similarity in Lifshitz-Kosevich low-temperature growth of quantum oscillation amplitude in insulating YbB
12
to field-induced metallic YbB
12
, points to an origin of quantum oscillations in insulating YbB
12
from in-gap neutral low energy excitations. Higher frequency Fermi surface sheets of heavy quasiparticle effective mass emerge in the field-induced metallic regime of YbB
12
in addition to multiple heavy Fermi surface sheets observed in both insulating and metallic regimes.
f
-electron hybridisation is thus observed to persist from the unconventional insulating to the field-induced metallic regime of YbB
12
, in contrast to the unhybridised conduction electron Fermi surface observed in unconventional insulating SmB
6
. Our findings thus require an alternative model for YbB
12
, of neutral in-gap low energy excitations, wherein the
f
-electron hybridisation is retained.
We investigated hemodynamics and plasma catecholamine concentrations in eight consecutive patients undergoing laparoscopic adrenalectomy for suspected pheochromocytoma. The same anesthesia protocol ...was used in all patients: a continuous infusion of sufentanil 0.5 microg x kg(-1) x h(-1) and isoflurane 0.4% (end-tidal) in 50% N2O/O2. Systolic arterial pressure was maintained between 120 and 160 mm Hg by adjusting an infusion of nicardipine, a calcium-channel blocker, while tachycardia (>100 bpm) was treated by 1-mg boluses of atenolol. Hemodynamics (thermodilution technique) and plasma catecholamine concentrations were measured before surgery, after the induction of anesthesia, after turning the patient to the lateral position, during pneumoperitoneum, during tumor manipulation, after adrenalectomy, and at the end of surgery. Two events resulted in significant catecholamine release: creation of the pneumoperitoneum and adrenal gland manipulation. As a consequence, a twofold increase in cardiac output was recorded. Adjustments of nicardipine infusion (2-6 microg x kg(-1) x min(-1)) minimized changes in mean arterial pressure. Beta-adrenergic blockade was necessary in six patients. In conclusion, laparoscopic adrenalectomy for pheochromocytoma results in marked catecholamine release during pneumoperitoneum and tumor manipulation. Titration of a nicardipine infusion allowed easy and quick control of the hemodynamic aberrancies related to these processes.
Pneumoperitoneum during laparoscopy, now used for adrenalectomy, may complicate anesthetic management of patients with pheochromocytoma. In this study, laparoscopic adrenalectomy was associated with catecholamine release during the creation of pneumoperitoneum and tumor manipulation. Adjustments of a nicardipine infusion readily attenuated the subsequent hemodynamic aberrancies.
The
global clone 1 isolate AB307-0294, recovered in the USA in 1994, and the global clone 2 (GC2) isolate ACICU, isolated in 2005 in Italy, were among the first
isolates to be completely sequenced. ...AB307-0294 is susceptible to most antibiotics and has been used in many genetic studies, and ACICU belongs to a rare GC2 lineage. The complete genome sequences, originally determined using 454 pyrosequencing technology, which is known to generate sequencing errors, were re-determined using Illumina MiSeq and MinION (Oxford Nanopore Technologies) technologies and a hybrid assembly generated using Unicycler. Comparison of the resulting new high-quality genomes to the earlier 454-sequenced versions identified a large number of nucleotide differences affecting protein coding sequence (CDS) features, and allowed the sequences of the long and highly repetitive
and
genes to be properly resolved for the first time in ACICU. Comparisons of the annotations of the original and revised genomes revealed a large number of differences in the protein CDS features, underlining the impact of sequence errors on protein sequence predictions and core gene determination. On average, 400 predicted CDSs were longer or shorter in the revised genomes and about 200 CDS features were no longer present.
Thromboprophylaxis in Microsurgery Lecoq, J.P.; Senard, M.; Hartstein, G.M. ...
Acta chirurgica belgica,
2006, Letnik:
106, Številka:
2
Journal Article
Recenzirano
Microsurgical free tissue transfer has become a gold standard in a wide range of clinical situations. Thrombosis at the anastomotic site is not only the most common cause of failure of microsurgical ...operations, but it is also one of the factors resulting in microcirculatory intravascular thrombosis in free flaps. All conditions of thrombus formation, defined by Virchow in 1856, are encountered in free flap surgery.
This literature review concerns the problem of thromboprophylaxis in microsurgery. All citations published this last ten years (1996-2005) concerning this problem are noted. Data are confronted with other specialties, particularly vascular surgery, or with large retrospective studies. Protocol used in our institution is presented at the end of this lecture.
To describe the potential complication of intracranial abscess in the setting of orbital abscess.
We retrospectively reviewed case reports and the literature. Three patients were found to have ...pansinusitis progressing to subperiosteal abscess of the orbit and subsequent intracranial abscess.
Three patients, ages 14, 26, and 57 years, with concurrent pansinusitis, subperiosteal abscess of the orbit, and intracranial abscess were treated with intravenous antibiotics and surgical drainage of the orbital abscess and sinuses. Two of the three patients required drainage of the intracranial abscess.
Although rare, intracranial abscess is a life-threatening complication of orbital abscess. It requires aggressive intervention by a multidisciplinary team.
Ocular parameters are influenced by sleep derivation and the use of chemical substances which are two major causes for traffic accidents. We assessed the use of these parameters as an objective ...screening tool for a driver's fitness for duty. Pupillary diameter, pupil reaction to light and saccadic velocity were measured in 29 army truck drivers every morning for two months and compared to baseline measurements taken while the subjects were alert. An index which expressed the difference between study and baseline measurements was calculated, and drivers with significant deviation from baseline were disqualified and interviewed. Non-disqualified drivers served as controls. Twenty-nine percent of disqualified drivers reported sleeping less than the minimum of 7
h required by army regulations compared with 8% of control drivers (
p
=
0.01). Disqualified drivers had worse sleep quality the night before the test (Groningen Sleep Quality Scale,
p
=
0.03) and incurred more accidents per driving day during their service (0.023 vs. 0.015 accidents/day,
p
=
0.03). Two disqualified drivers admitted to using alcohol or sleeping pills. Thus, these ocular parameters may serve as a screening tool for drivers that are at high risk for driving. Drivers who were disqualified even once, tend to be involved in more motor vehicle accidents than their peers.
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