Objective To assess the diagnostic value of chest radiographs in patients presenting to a busy inner-city Emergency Department with subsequently proven acute aortic dissection. Methods A retrospective review of initia...Objective To assess the diagnostic value of chest radiographs in patients presenting to a busy inner-city Emergency Department with subsequently proven acute aortic dissection. Methods A retrospective review of initial chest radiographs and charts of patients with the confirmed diagnosis of acute aortic dissection was done for a period of 5 years from 1998 to 2003. A comparison was made between the initial readings of chest radiographs prior to confirmation of the aortic dissection, and a retrospective review of the same radiographs by two board-certified radiologists with special attention to the classic findings of acute aortic dissection identifiable on plain films. Results The charts of nine patients (four men, five women) with proven acute aortic dissection were reviewed. All nine patients were suspected of having acute aortic dissection based on presenting history and symptoms of chest pain (66% ), migratory pain (89% ), back pain (89% ), and the abruptness of onset of pain (89% ). Initial plain portable chest X-rays were obtained in the Emergency Department in all nine patients. Six of nine (67%) radiographs were read as normal, while three (33%) demonstrated a widened mediastinum (＞ 8.0cm), two (22%) showed an abnormal aortic contour, with one ( 11% ) displaying an apical cap. Confirmation of the diagnosis was obtained with either a spiral CT angiogram or transesophageal echocardiography (TEE). All nine plain radiographs were retrospectively reviewed by two board-certified radiologists aware of the diagnosis of acute dissection without a change in the readings. Conclusions Plain portable chest radiographs are of limited usefulness for the screening of acute aortic dissection. Further radiologic evaluation should be dictated by the clinical presentation and an awareness of the low sensitivity of portable chest X- rays.展开更多
Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization a...Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization are not well understood. By using atomic sources to control the extent of the oxygen and nitrogen functionalization, we studied the evolution in the structure and properties at the atomic scale. Atomic oxygen reversibly introduces epoxide groups whilst, under similar conditions, atomic nitrogen irreversibly creates diverse functionalities including substitutional, pyridinic, and pyrrolic nitrogen. Atomic oxygen leaves the Fermi energy at the Dirac point （i.e., undoped）, whilst atomic nitrogen results in a net n-doping; however, the experimental results are consistent with the dominant electronic effect for both being a transition from delocalized to localized states, and hence the loss of the signature electronic structure of graphene.展开更多
文摘Objective To assess the diagnostic value of chest radiographs in patients presenting to a busy inner-city Emergency Department with subsequently proven acute aortic dissection. Methods A retrospective review of initial chest radiographs and charts of patients with the confirmed diagnosis of acute aortic dissection was done for a period of 5 years from 1998 to 2003. A comparison was made between the initial readings of chest radiographs prior to confirmation of the aortic dissection, and a retrospective review of the same radiographs by two board-certified radiologists with special attention to the classic findings of acute aortic dissection identifiable on plain films. Results The charts of nine patients (four men, five women) with proven acute aortic dissection were reviewed. All nine patients were suspected of having acute aortic dissection based on presenting history and symptoms of chest pain (66% ), migratory pain (89% ), back pain (89% ), and the abruptness of onset of pain (89% ). Initial plain portable chest X-rays were obtained in the Emergency Department in all nine patients. Six of nine (67%) radiographs were read as normal, while three (33%) demonstrated a widened mediastinum (＞ 8.0cm), two (22%) showed an abnormal aortic contour, with one ( 11% ) displaying an apical cap. Confirmation of the diagnosis was obtained with either a spiral CT angiogram or transesophageal echocardiography (TEE). All nine plain radiographs were retrospectively reviewed by two board-certified radiologists aware of the diagnosis of acute dissection without a change in the readings. Conclusions Plain portable chest radiographs are of limited usefulness for the screening of acute aortic dissection. Further radiologic evaluation should be dictated by the clinical presentation and an awareness of the low sensitivity of portable chest X- rays.
文摘Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization are not well understood. By using atomic sources to control the extent of the oxygen and nitrogen functionalization, we studied the evolution in the structure and properties at the atomic scale. Atomic oxygen reversibly introduces epoxide groups whilst, under similar conditions, atomic nitrogen irreversibly creates diverse functionalities including substitutional, pyridinic, and pyrrolic nitrogen. Atomic oxygen leaves the Fermi energy at the Dirac point （i.e., undoped）, whilst atomic nitrogen results in a net n-doping; however, the experimental results are consistent with the dominant electronic effect for both being a transition from delocalized to localized states, and hence the loss of the signature electronic structure of graphene.
