Apparent and intrinsic Q: the one-dimensional case

The propagation of plane waves through statistically layered media is investigated both numerically and with single-scattering theory in the one-dimensional case. Exact apparent or stratigraphic Q, Qs, is determined from synthetic seismograms with the spectral-ratio method. Maximum velocity (impedance) fluctuations up to 30% (~40%) are studied; the fluctuations are uniformly distributed with zero mean. In all cases the trend of Qs as a function of frequency is well described by the analytical Qs, as determined from single-scattering theory under the assumption of an exponential autocorrelation function of the impedance fluctuations. The frequency dependence of the analytical Qs-1 follows a Debye-peak function, its maximum is γ2/2 and corresponds to the wavelength 4πa (γ2 = variance of relative impedance fluctuation, a = correlation distance). In further numerical calculations intrinsic or anelastic Q, Qa, is introduced, and it is shown that total attenuation Q -1 agrees very well with the sum of apparent and anelastic attenuation, Qs-1+Qa-1.  Finally, a simple, minimum-phase stratigraphic attenuation operator is derived which describes the amplitude decay and the dispersion in a one-dimensional random medium with good accuracy. Stratigraphic attenuation is similar to the anelastic attenuation of a standard linear solid.           ARK: https://n2t.net/ark:/88439/y038753 Permalink: https://geophysicsjournal.com/article/119 &nbsp

Vascular Perforation During Coil Embolization of an Intracranial Aneurysm: the Incidence, Mechanism, and Clinical Outcome

PurposeThe occurrence of a vascular perforation during an endovascular procedure is an unexpected and feared complication which can be fatal. However, the incidence, risk or the mechanism of vascular perforation which can occur in the endovascular management of aneurysms remains unclear. The purpose of the present study was to evaluate the incidence of vascular perforation during endovascular coil embolization of a cerebral aneurysm, and to reveal characteristics and clinical outcomes.Materials and MethodsWe reviewed the endovascular coil embolization procedures performed for the treatment of 459 aneurysms. Incidence and clinical, radiological and technical data of patients concerning the vascular perforation were reviewed from medical records and radiological findings.ResultsThe incidence of procedure-related vascular perforation in our patient group was 0.87% (4/459). For all four occurrences, the cause of vascular perforation involved the guidewire or microcatheter. Clinical outcome was poor in 2 cases and favorable in 2 cases.ConclusionAlthough rare, the occurrence of vascular perforation during coil embolization for treatment of an aneurysm may be fatal. Therefore, careful management of the guidewire is suggested for the prevention of vascular rupture during an endovascular procedure

Successful Internalization of a Chronic Biliary Cutaneous Fistula After Liver Transplantation: Deepithelializing the Fistula Tract

Biliary cutaneous fistulas are uncommon sequelae after biliary surgery and can be a source of significant morbidity. We describe a liver recipient who developed a biliary cutaneous fistula secondary to hepatic artery thrombosis; this subsequently drained for over 7 years. Through a novel approach, using the transabdominal fistula tract as a conduit, the fistula skin opening was deepithelialized and anastomosed to a jejunal loop, internally draining the tract. For over 7 years postoperatively, this internal drainage procedure has continued to function effectively. This approach may have value in internalizing longstanding biliary cutaneous fistulas in well-selected patients in whom there is no existing biliary ductal system or the existing system anatomically does not lend itself to restoration of functional internal drainage through conventional approaches

Management of Massive Arterial Hemorrhage After Pancreatobiliary Surgery: Does Embolotherapy Contribute to Successful Outcome?

Massive arterial hemorrhage is, although unusual, a life-threatening complication of major pancreatobiliary surgery. Records of 351 patients who underwent major surgery for malignant pancreatobiliary disease were reviewed in this series. Thirteen patients (3.7%) experienced massive hemorrhage after surgery. Complete hemostasis by transcatheter arterial embolization (TAE) or re-laparotomy was achieved in five patients and one patient, respectively. However, 7 of 13 cases ended in fatality, which is a 54% mortality rate. Among six survivors, one underwent selective TAE for a pseudoaneurysm of the right hepatic artery (RHA). Three patients underwent TAE proximal to the proper hepatic artery (PHA): hepatic inflow was maintained by successful TAE of the gastroduodenal artery in two and via a well-developed subphrenic artery in one. One patient had TAE of the celiac axis for a pseudoaneurysm of the splenic artery (SPA), and hepatic inflow was maintained by the arcades around the pancreatic head. One patient who experienced a pseudoaneurysm of the RHA after left hemihepatectomy successfully underwent re-laparotomy, ligation of RHA, and creation of an ileocolic arterioportal shunt. In contrast, four of seven patients with fatal outcomes experienced hepatic infarction following TAE proximal to the PHA or injury of the common hepatic artery during angiography. One patient who underwent a major hepatectomy for hilar bile duct cancer had a recurrent hemorrhage after TAE of the gastroduodenal artery and experienced hepatic failure. In the two patients with a pseudoaneurysm of the SPA or the superior mesenteric artery, an emergency re-laparotomy was required to obtain hemostasis because of worsening clinical status. Selective TAE distal to PHA or in the SPA is usually successful. TAE proximal to PHA must be restricted to cases where collateral hepatic blood flow exists. Otherwise or for a pseudoaneurysm of the superior mesenteric artery, endovascular stenting, temporary creation of an ileocolic arterioportal shunt, or vascular reconstruction by re-laparotomy is an alternative

Standard of Practice for the Endovascular Treatment of Thoracic Aortic Aneurysms and Type B Dissections

Thoracic endovascular aortic repair (TEVAR) represents a minimally invasive technique alternative to conventional open surgical reconstruction for the treatment of thoracic aortic pathologies. Rapid advances in endovascular technology and procedural breakthroughs have contributed to a dramatic transformation of the entire field of thoracic aortic surgery. TEVAR procedures can be challenging and, at times, extraordinarily difficult. They require seasoned endovascular experience and refined skills. Of all endovascular procedures, meticulous assessment of anatomy and preoperative procedure planning are absolutely paramount to produce optimal outcomes. These guidelines are intended for use in quality-improvement programs that assess the standard of care expected from all physicians who perform TEVAR procedures

Anders-Sein : process of self cultivation with techno music

Postmodern society is characterized by quick changes and can be called liquid modernity (Bauman, 2000), wherein individualization is ubiquitous (Reckwitz, 2017). Some people are Anders and attempt not to conform nor have conformist consumption practices (Hemetsberger and Weinberg, 2012). Individuals are in between conformist and nonconformist and cultivate reflections of themselves. For this reason, self-reflection is an essential tool for a continuous change of ones identity. Self-reflection as a process (Atkins and Murphy, 1993) is a tool for reflecting on past impressions and situations to further develop new perspectives and personal growth. This study offers insights into people who go clubbing to techno music and shows domains where individuals are reflecting themselves. The outcome of this self-reflection can be that changes or significant turning points in life must occur to increase well-being and improve ones sense of identity. Furthermore, the study shows the integration of reflective clubbing as a part of consumption in ones personality.submitted by Alexander GorichUniversity of Innsbruck, Masterarbeit, 2019(VLID)363778