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Within the framework of elastic anisotropy, caused in a phononic crystal due to low crystallographic symmetry, we adopt a model structure, already introduced in the case of photonic metamaterials, and by analogy, we study the effect of birefringence and acoustical activity in a phononic crystal. In particular, we investigate its low-frequency behavior and comment on the factors which determine chirality by reference to this model. [ABSTRACT FROM AUTHOR]

Aim-Background: The indication for performing a left carotid-subclavian bypass in the case of an occluded left subclavian artery following endovascular stent placement in the descending thoracic aorta is not well established. Case report: We describe a case report of a 72-year-old patient with a ruptured aortic isthmus and an aberrant left vertebral artery originating from the aortic arch, who was treated with emergent endovascular stent-graft placement in the descending thoracic aorta.In the immediate postoperative period, the patient complained of left upper extremity pain and loss of sensation, and the limb was pale. Arterial Doppler ultrasonography of the left extremity revealed monophasic arterial pulse waves associated with low flow velocities. The patient was taken to the operating room and was submitted to a left carotidsubclavian bypass using an 8mm PTFE graft. Conclusion: In the present case immediate revascularization using a carotid-subclavian bypass is strongly indicated to relieve left upper extremity ischaemia due to the absence of collateral circulation from the vertebral artery [ABSTRACT FROM AUTHOR]

We present a case of a 52-year-old male patient who died from massive hematemesis as a result of perforation of a benign peptic ulcer into the descending thoracic aorta, 1 year after esophagectomy for esophageal cancer and gastric tube interposition. We also review the literature for mechanisms of ulceration in intrathoracic gastric grafts and for complications of such ulcers. [ABSTRACT FROM AUTHOR]