No abstract

In this article, the extrapolation procedures of π-π* electronic transition energy on π-conjugated oligomers are reexamined. Different models, including the simplest coupled oscillator, the free electron, the Hückel approach, the molecular exciton model, and some specific fitting-functions, are compared using the transition energies derived from theoretical calculations on three thiophene-based oligomer series. Specifically, oligomers of up to 30 repeating units have been considered to include the saturation effects as a function of chain length. The coupled oscillator model of W. Kuhn and the fitting-function of Hirayama are the models that present the better suit on the transition energy interpolation as a function of chain length. Using only the first four oligomers of the series (n = 2 up to 8) yields an estimation of the transition energy on the polymer limit with an average error of ∼1.5%. The vertical and adiabatic ionization potential present a better fit with the Hückel model approach. Finally, implications of the environmental polarity on the electronic properties, molecular geometry, charge distribution, and aromaticity are shortly discussed.

lected HCC are similar to the results in cirrhotic patients Cumulative recurrence after surgical resection for hewithout tumor. (HEPATOLOGY 1997;25:1485-1489.) patocellular carcinoma (HCC) is very high. Several retrospective analyses have shown that liver transplantation was more effective than resection for patients with Hepatocellular carcinoma (HCC) usually occurs with the HCC at early tumor stages. Consequently, in January presence of cirrhosis and is considered to have a poor progno-1990, we decided to prospectively indicate orthotopic sis.1 To the present, surgical resection has been the treatment liver transplantation (OLT) as the first surgical treat-of choice whenever feasible.2 However, the resection rate rement for small, localized HCC in cirrhotic patients with-mains low in cirrhotic patients. 3,4 In the last few years, some out nodal involvement independently of the degree of groups have reported disappointing long-term results after liver function. The aim of this prospective cohort study resection of small tumors in cirrhotic patients. The 5-year was to analyze prognosis, recurrence rate, and survival recurrence rate is very high, 74% among 386 patients acafter liver transplantation in patients in whom the main cording to Makuuchi, 5 and 100% in Belghiti's series. 6 Other indication was HCC with cirrhosis. Thirty-eight patients authors have accepted orthotopic liver transplantation (OLT) in whom the main indication for liver transplantation as a treatment indication in patients with advanced tumors was HCC and hepatic cirrhosis were compared with 136 or with associated end-stage liver disease.7-11 Moreover, sevtransplantations because of cirrhosis without tumor, eral retrospective analyses have recently shown that OLT performed in our unit from January 1990 to December was more effective than liver resection for patients with HCC 1995. HCC arising in noncirrhotic livers and those inci-at early tumor stages. 7,8,10,11 However unfavorable results dently discovered after OLT were excluded from the compared with benign disease and a shortage of donor organs study. Chemoembolization using doxorubicin, lipiodol, have led to a restricted indication of liver transplantation for and Gelfoam was performed before OLT in 31 patients HCC.12-14 On the other hand, the absence of recurrence after with good liver function. There were no differences in transplantation for incidental HCC prompted us to look for gender, but HCC patients were older (57 { 7 vs. 50 { 10 favorable preoperative staging criteria for small HCC in ciryears [P õ .001]). Liver function was better in HCC rhosis with regard to OLT, 15 but there is no general agree-(Child-Pugh score: 6.9 { 2 vs. 8.6 { 1.8; P õ .001), and ment as to the selection of ideal candidates for OLT. [7][8][9][10][11][12]16 hepatitis C virus antibody was positive in 31 (82%) vs. 51The 5-year survival rate after liver resection for HCC is (37%) (P õ .007). Seven tumors had bilobar involvement very poor, ranging from 12% to 50% in both eastern and (18%). Capsule was presen...