Living ring-opening homo- and copolymerisation of ε-caprolactone and L-lactide by cyclic ß-ketiminato aluminium complexes.

A series of novel aluminium complexes containing cyclic ß-ketiminato ligands of type Me2Al{O-[(ArN=CHC4H4(C6H4))]} (3a, Ar = 2,6-(i)Pr2C6H3; 3b, Ar = C6H5; 3c, Ar = C6F5) have been prepared in high yields. These complexes were identified by (1)H, (13)C NMR spectroscopy and elemental analysis. X-ray structural analyses for 3a-c revealed that these complexes have a distorted tetrahedral geometry around Al, and both bond distances and bond angles were considerably influenced by the ligand structure. These complexes were tested as catalyst precursors for ring-opening polymerisation of ε-caprolactone (ε-CL) and L-lactide (L-LA) in the presence of 2-propanol as an initiator. Complex 3a could polymerize ε-CL in a controlled manner with high efficiency. Based on the living characteristics, the preparation of well-defined block copolymers PCL-b-PLLA via sequential addition of monomers was performed by 3a. Note that complex 3c exhibited rather high catalytic activity for the ROP of L-LA with narrow molecular weight distribution. The monomer conversion reached completion only in 4 h when the L-LA/Al molar ratio was 100 at 80 °C. PLLA-b-PCL copolymers were thus easily produced by 3c.

Misdiagnosis of aortic dissection: experience of 361 patients.

Aortic dissection (AD) is a life-threatening condition that requires immediate diagnosis and surgical correction. Patients with acute AD usually present clinically with an insignificant medical history, leading to a high probability of misdiagnosis. The aim of the present study was to investigate the number of misdiagnoses of patients with AD in order to understand this problem and to avoid future misdiagnosis in the emergency department. Clinical data from 361 patients with AD admitted between January 2003 and June 2008 were reviewed as part of a retrospective chart review. Diagnosis of AD was made using either chest x-ray, computed tomography, magnetic resonance imaging, or angiography. Fifty-one patients had an initial misdiagnosis (14.1%), later found to have experienced AD. The condition may clinically present in a varied number of manifestations, including syncope, chest pain, abdominal pain, back pain, acute congestive heart failure, or alternatively with minimal symptoms. Persons of any age can experience an AD, with key clinical manifestations of pain. Echocardiography can be used for primary examination of patients with suspected AD; however, a definite diagnosis is usually made using computed tomographic or magnetic resonance angiography. Care should be taken, particularly in the emergency department, to maintain a level of suspicion for AD diagnosis in order to avoid the potential for misdiagnosis.