ABSTRACT
We present a short overview and two benchmark applications of the Molecular Orbital-Valence Bond (MO-VB) method, a quantum mechanical scheme developed within the framework of modern Valence Bond theory. The MO-VB has been especially designed to deal with weak intermolecular interactions, and in recent years it has been successfully applied to compute the potential energy surface of several complexes, namely He(2), He-H(2)O, He-CH(4) and Ne-CH(4). In this investigation we test extensively the performance of the MO-VB on two limit systems, the He dimer and the LiH-He complex, which span three extremes in the field of van der Waals interactions: a purely dispersive system (He...He) and, thanks to the highly polar Li-H bond, a noble gas approaching a cation (He...Li(+)), and an anion (He...H(-)). Very accurate computations are available in the literature for He(2) and LiH-He, performed either with conventional Molecular Orbital or Monte Carlo approaches, and hence these systems are the ideal candidates to establish the capabilities of the MO-VB. Based on the results of our study, we conclude that in He(2) and LiH-He the MO-VB overestimates the correlation energy contribution to the interaction energy of about 5%, and hence it is a valid option for computing accurate lower bounds to the potential energy surface of these complexes.
ABSTRACT
The electronic structure of nitrilimine HCNNH is shown to essentially be propargylic by CASSCF and Spin-Coupled (modern VB) calculations; in contrast to a recent claim, the carbenic resonance form is absent.
ABSTRACT
PURPOSE: Small-cell lung cancer (SCLC) is increasingly diagnosed in elderly patients, who are at higher risk of treatment-related morbidity and mortality. We conducted a randomized two-stage phase II study to assess the therapeutic index of two different platinum/etoposide regimens, attenuated-dose (AD) and full-dose (FD) plus prophylactic lenograstim. PATIENTS AND METHODS: SCLC patients older than 70 years were randomized to receive four courses of cisplatin 25 mg/m(2) on days 1 and 2, and etoposide 60 mg/m(2) on days 1, 2, and 3 every 3 weeks (AD); or cisplatin 40 mg/m(2) on days 1 and 2, and etoposide 100 mg/m(2) on days 1, 2, and 3 every 3 weeks, plus lenograstim 5 mg/kg days 5 through 12, every 3 weeks (FD). A combined primary end point named therapeutic success (TS), which took into account activity, toxicity, and compliance, was used. RESULTS: Ninety-five patients were enrolled. Seventy-five percent and 72% of the patients in the AD and FD arms, respectively, completed the treatment as per protocol. Response rate was 39% and 69% in the AD and FD arms, respectively, and 1-year survival probability was 18% and 39%, respectively. Treatment was well tolerated in both groups, with no grade 3 to 4 myelotoxicity in the AD arm, and 12% myelotoxicity in the FD arm. Overall, the observed TSs were 10 (36%) of 28 patients and 42 (63%) of 67 patients for AD and FD treatments, respectively. CONCLUSION: In elderly patients with SCLC a full-dose cisplatin/etoposide regimen combined with prophylactic lenograstim is active and feasible, while attenuated doses of the same regimen are associated with a poor therapeutic outcome.