193 research outputs found
Impurity-induced smearing of the spin resonance peak in Fe-based superconductors
The spin resonance peak in the iron-based superconductors is observed in
inelastic neutron scattering experiments and agrees well with predicted results
for the extended s-wave () gap symmetry. On the basis of four-band and
three-orbital tight binding models we study the effect of nonmagnetic disorder
on the resonance peak. Spin susceptibility is calculated in the random phase
approximation with the renormalization of the quasiparticle self-energy due to
the impurity scattering in the static Born approximation. We find that the spin
resonance becomes broader with the increase of disorder and its energy shifts
to higher frequencies. For the same amount of disorder the spin response in the
state is still distinct from that of the state.Comment: 4 pages, 2 figure
Automorphisms fixing a variable of K<x,y,z>
We study automorphisms of the free associative algebra K over a field
K which fix z and such that the images of x, y are linear with respect to x, y.
We prove that some of these automorphisms are wild in the class of all
automorphisms fixing z, including the well known automorphism discovered by
Anick, and show how to recognize the wild ones. This class of automorphisms
induces tame automorphisms of the polynomial algebra K[x,y,z]. For n>2 the
automorphisms of K which fix z and are linear in the x's are
tame.Comment: 8 page
On the lifting of the Nagata automorphism
It is proved that the Nagata automorphism (Nagata coordinates, respectively)
of the polynomial algebra over a field cannot be lifted to a
-automorphism (-coordinate, respectively) of the free associative algebra
. The proof is based on the following two new results which have
their own interests: degree estimate of and tameness of
the automorphism group .Comment: 15 page
Videolaparoscopic surgical treatment of strangulated paraesophageal hiatal hernia (clinical observation)
Relevance. Paraesophageal hiatal hernias are much less common than other types of diaphragmatic hernias. The risk of strangulation in this pathology is about 21Β %. It is often very difficult to establish the correct diagnosis in time, because patients are admitted with an atypical clinic of acute cardiological or pulmonary pathology. Usually, the correct diagnosis is established only on the 4th day. Due to late diagnosis, necrosis and perforation of the strangulated organ occur, which causes high mortality; sometimes the correct diagnosis is established only at autopsy.Clinical observation. The patient was admitted to the surgical department on an emergency basis with complaints of intense pain in the lower chest and epigastric region, vomiting of eaten food. From the anamnesis it is known that about a year ago, periodic nausea and vomiting of food eaten began to bother. The last 12 hours before admission to the hospital, pain in the chest and epigastrium intensified, all eaten food came out with vomiting. X-ray diagnosed strangulated paraesophageal hernia of the esophageal opening of the diaphragm. During esophagogastroduodenoscopy it was impossible to pass into the distal parts of the stomach; hyperemia and petechial hemorrhages were detected in the zone of strangulation. Video-laparoscopic reduction of the hernial contents, resection of the hernial sac and anterior diaphragm crurorrhaphy were urgently performed. The early postoperative period was uneventful. The presented clinical observation indicates the promise of using video-endoscopic technologies for diagnosis and treatment of strangulated diaphragmatic hernias. The key to success is the timely establishment of the correct diagnosis. We consider it impractical to perform an antireflux intervention simultaneously in conditions of an acute inflammatory process
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