The interaction of a series of molecular probes (O
3, H
2S, CO, NH
3, (CH
3)
2CO, C
5H
5N and CH
3CN) with the hydrated SiO
2 surface has been investigated by QM/MM calculations and diffuse ...reflectance infrared Fourier transform spectroscopy. Theoretical estimates of O–H stretchings are shown to be improved by a new treatment of the molecular mechanics part of the model. Such a result is encouraging for the application of the adopted approach to other systems.
Quasi-relativistic density functional calculations have been used to look into the molecular and electronic properties of
cis-Pt(η
3-C
3H
5){η
1-C(PPh
3)(CO)}
2BF
4. Numerical experiments have been ...run for both isomers compatible with IR and NMR outcomes. Binding energies and computed CCO stretching frequencies are very similar for both species, thus indicating their possible coexistence in solution. The comparison with homogeneous theoretical data pertaining to
cis/
trans-Pt(η
3-C
3H
5)
2 and
trans-PtCl
2{η
1-C(PPh
3)(CO)}
2 provides a rationale of the Pt(η
3-C
3H
5){η
1-C(PPh
3)(CO)}
2BF
4 low stability.
The structure of the
cis-Pt(η
3-C
3H
5){η
1-C(PPh
3)CO}
2
+ ion has been studied by means of quasi-relativistic density functional calculations. Theoretical outcomes compare well with experiment and ultimately indicate that the high instability of this species is a consequence of the low binding energy between the charged Pt(η
3-C
3H
5)
+ fragment and the neutral
cis-{η
1-C(PPh
3)CO}
2 moiety.
To compare the haemodynamic effects of identical values of continuous negative external pressure (CNEP) and positive end-expiratory pressure (PEEP) in a group of mechanically ventilated patients.
...General ICU, Vicenza Hospital, Italy.
15 consecutive patients, admitted after road accident trauma.
We compared the haemodynamic effects of ZEEP, 10 cmH2O of PEEP, and 10 cmH2O CNEP, applied in random order, in 15 head trauma patients under going controlled mechanical ventilation; 9 had associated thoracic trauma, while 6 did not have lung involvement. CNEP was obtained with a "poncho".
We observed a significant increase in CI during CNEP, compared with both ZEEP and PEEP 10 cmH2O. Accordingly the oxygen delivery index significantly increased during CNEP, compared with PEEP 10 cmH2O. Conversely, Qs/Qt decreased with CNEP, if compared with PEEP, both in patients with and without lung damage.
CNEP can significantly increase CI in mechanically ventilated patients in patients with and without associated lung damage.
Abstract
The Al
III
‐binding abilities of two aldaric acids,
D
‐saccharic acid and mucic acid (the neutral form is denoted as H
2
L), were studied in solution by means of pH potentiometric,
1
H and
...13
C NMR, and ESI‐MS techniques. The most probable conformations and isomeric binding modes of the complexes formed in solution were determined by density functional theory (DFT) calculations. A solid
D
‐saccharic acid complex K
2
{Al(LH
−2
)(H
2
O)}
2
⋅H
2
O was isolated and crystallographically characterised. The two alcoholic hydroxy groups α to the terminal COO
−
groups were found to take part in the coordination, but in different ways. One of them coordinates in a bridging mode. Detailed ESI‐MS and NMR studies proved that the complex retains its structure in solution. However, depending on the ligand and the pH, such complexes may exist in two isomeric forms. DFT calculations on the ion {Al(LH
−2
)(H
2
O)}
2
2−
revealed that several orbitals participate in stabilizing the dimeric arrangement.
The electronic and molecular properties of interstitial O
3 in SiO
2 have been theoretically studied by coupling the molecular cluster model to the density functional theory. We find that, on passing ...from the free species to the interstitial one, electronic and molecular structures of O
3 are only slightly perturbed. Moreover, in agreement with the experimental assignment of Skuja et al., it is confirmed that the ubiquitous absorption band at 4.8 eV characterizing 7.9 eV photon-irradiated SiO
2 samples includes a contribution due to excitations between O
3 based occupied and unoccupied MOs.
