End Of CO Research Articles

Hybrid Ring- and Tree-Topology RoF Transmission System with Disconnection Protection

This paper proposes a hybrid ring- and tree-topology radio over fiber (RoF) transmission system with self-disconnection protection that can support the high distribution density of base stations (BSs) in a metropolitan area and strengthen the network quality of service through self-disconnection protection. The number of supportable BS in the system can be increased significantly by integrating the time- and wavelength-division multiplexing techniques and properly utilizing a new-generation single-line bidirectional add/drop multiplexer (SBOADM) into the proposed system. Moreover, when the ring–fiber link of the system is interrupted for any reason, the system operator can recover the broken connections quickly only by transforming an optical switch state at the CO end to allow the downlink optical signals to transmit along the clockwise and counterclockwise directions of the ring–fiber link simultaneously. In this case, the downstream optical signals can be delivered to each set of BS-groups through the two-way transmission characteristics of the SBOADM automatically, and the uplink optical signals, originally, from each set of BS-groups can be transmitted back to the CO end along the opposite direction of the downlink signal-routing path. In this way, the interference caused by fiber breakage can be avoided immediately, and the entire transport system can be reconnected to ensure the quality of network services. Our experimental results prove that the overall transmission performances are similar to those under normal circumstances.

Metal-CO Bonding in Mononuclear Transition Metal Carbonyl Complexes.

DFT calculations have been carried out for coordinatively saturated neutral and charged carbonyl complexes [M(CO)n]q where M is a metal atom of groups 2–10. The model compounds M(CO)2 (M = Ca, Sr, Ba) and the experimentally observed [Ba(CO)]+ were also studied. The bonding situation has been analyzed with a variety of charge and energy partitioning approaches. It is shown that the Dewar–Chatt–Duncanson model in terms of M ← CO σ-donation and M → CO π-backdonation is a valid approach to explain the M–CO bonds and the trend of the CO stretching frequencies. The carbonyl ligands of the neutral complexes carry a negative charge, and the polarity of the M–CO bonds increases for the less electronegative metals, which is particularly strong for the group 4 and group 2 atoms. The NBO method delivers an unrealistic charge distribution in the carbonyl complexes, while the AIM approach gives physically reasonable partial charges that are consistent with the EDA-NOCV calculations and with the trend of the C–O stretching frequencies. The AdNDP method provides delocalized MOs which are very useful models for the carbonyl complexes. Deep insight into the nature of the metal–CO bonds and quantitative information about the strength of the [M] ← (CO)8 σ-donation and [M(d)] → (CO)8 π-backdonation visualized by the deformation densities are provided by the EDA-NOCV method. The large polarity of the M–CO π orbitals toward the CO end in the alkaline earth octacarbonyls M(CO)8 (M = Ca, Sr, Ba) leads to small values for the delocalization indices δ(M–C) and δ(M···O) and significant overlap between adjacent CO groups, but the origin of the charge migration and the associated red-shift of the C–O stretching frequencies is the [M(d)] → (CO)8 π-backdonation. The heavier alkaline earth metals calcium, strontium and barium use their s/d valence orbitals for covalent bonding. They are therefore to be assigned to the transition metals.

Physiologic effects of pneumoperitoneum in adults with sickle cell disease undergoing laparoscopic cholecystectomy (A case control study)

Many studies have demonstrated the adverse consequences of pneumoperitoneum. However, few studies have examined the physiologic effects of pneumoperitoneum in adults with sickle cell disease (SCD) during laparoscopic cholecystectomy (LC). 60 ASA 1-capital PE, Cyrillic capital PE, Cyrillic patients, with cholelithiasis, scheduled for elective LC were allocated into two equal groups: group 1, normal patients without SCD (control group), and group 2, patients with SCD. The perioperative parameters of 30 SCD patients matched by age and sex to the 30 members of the non-sickler control group who underwent cholecystectomy were assessed. Study parameters (in the two groups) included heart rate (HR) per minute, mean blood pressure (MAP, mmHg), PETCO(2), and O(2) saturation (SpO(2)) at the following intervals: before induction of anesthesia in the supine position (all except PETCO(2)), after anesthesia and before CO(2) insufflations in the supine position, 15, 30, 45, 60 min after CO(2) insufflations in the anti-Trendelenburg position, at the end of CO(2) exsufflation in the supine position and 5 min after the end of CO(2) exsufflation in the supine position. Arterial blood gases, to measure pH, PaCO(2), and PaO(2), were determined after induction of anesthesia and before CO(2) insufflation in the supine position, then 30 min after CO(2) insufflations in the anti-Trendelenburg position, and 5 min after the end of CO(2) exsufflation in the supine position. Statistical significance was established at the p < 0.05 level. Induction of anesthesia produced a significant increase in HR in both groups. CO(2) insufflations led to an additional increase in HR and persisted till abdominal deflation. After CO(2) insufflations, MAP significantly increased from the baseline at 15, 30, 45, and 60 min, and just before deflation in the anti-Trendelenburg position. CO(2) insufflations led to a significant increase in end-tidal CO(2) (ETCO(2)) in the study groups, reaching a maximum level just before abdominal deflation in the anti-Trendelenburg position. Regarding SpO(2) and PaO(2), there were insignificant changes in the two study groups throughout the procedure. In group 2, none of the patients experienced vaso-occlusive crises or other SCD- related complications. This study proved the safety of LC in patients with SCD and cholelithiasis, and that they can tolerate the physiological effects of pneumoperitoneum as non-SCD adults.

Adsorption properties of CO on low-index Pt 3Sn surfaces

The adsorption properties of CO on Pt 3Sn were investigated by utilizing quantum mechanical calculations. The (1 1 1), (1 1 0) and (0 0 1) surfaces of Pt 3Sn were generated with all possible bulk terminations, and on these terminations all types of active sites were determined. The adsorption energies and the geometries of the CO molecule at those sites were found. Those results were compared with the results obtained from the adsorption of CO on similar sites of Pt(1 1 1), Pt(1 1 0) and Pt(0 0 1) surfaces. The comparison reveals that adsorption of CO is stronger on Pt surfaces; this may be the reason why catalysts with Pt 3Sn phase do not suffer from CO posioning in experimental works. Aiming to understand the interactions between CO and the metal adsorption sites in detail, the local density of states (LDOS) profiles were produced for atop-Pt adsorption, both for the carbon end of CO for its adsorbed and free states, and for the Pt atom of the binding site. LDOS profiles of C of free and adsorbed CO and Pt for corresponding pure Pt surfaces, Pt(1 1 1), Pt(1 1 0) and Pt(0 0 1) were also obtained. The comparison of the LDOS profiles of Pt atoms of atop adsorption sites on the same faces of bare Pt 3Sn and Pt surfaces showed the effect of alloying with Sn on the electronic properties of Pt atoms. Comparison of LDOS profiles of the C end of CO in its free and atop adsorbed states on Pt 3Sn and LDOS of Pt on bare and CO adsorbed Pt 3Sn surface were used to clear out the electronic changes occurred on CO and Pt upon adsorption. The study showed that (i) inclusion of a Sn atom at the adsorption site structure causes dramatic decrease in stability which limits the number of possible CO adsorption sites on Pt 3Sn surface, (ii) the presence of Sn causes angles different from 180° for M–C–O orientation, (iii) the presence of Sn in the neighborhood of Pt on which CO is adsorbed causes superposition of the 5σ/1π derived-state peaks at the carbon end of CO and changes in adsorption energy of CO, (iv) Sn present beneath the adsorption site strengthens the CO adsorption, whereas neighboring Sn on the surface weakens it for all Pt 3Sn surfaces tested and (v) the most stable site for CO adsorption is the atop-Pt site of the mixed atom termination of Pt 3Sn(1 1 0).

The Electric Dipole Moment of the CO2–CO van der Waals Complex

Radiofrequency transitions withinK= 2 asymmetry doublets have been observed for the CO2–CO van der Waals complex. A Stark effect measurement on theJ= 2,K= 2 transition provides an electric dipole moment of μ = 0.2493(1) D. Combining this result with the permanent moment of CO, μCO= 0.1098 D, gives a change of moment on complex formation of Δμ = 0.140 D. The sign of Δμ is such that the CO end of the complex is more positive than CO2. The origin of Δμ should not be attributed to any single mechanism, and several different contributions to Δμ are discussed.

The rovibrational spectrum of the ArCO complex calculated from a semiempirically extrapolated coupled pair functional potential energy surface

The rovibrational spectrum of the ArCO van der Waals complex has been calculated using a recently published ab initio potential energy surface determined by the coupled pair functional approach. Comparison with known experimental values for some of the transitions shows that the anisotropy of this surface comes out reasonably well, although its well depth of 72 cm−1 is too small. Based on a comparison of coupled pair functional interaction energies for Ne2, NeAr, and Ar2 with empirical potential energy curves an extrapolation scheme for the differential correlation energy is suggested. This semiempirical extrapolation scheme, with a slight modification to account for anisotropy, is also applied to the coupled pair functional interaction energies for ArCO, resulting in a surface which is characterized by a well depth of 109 cm−1 at a T-shaped geometry and a barrier of 20 cm−1 for rotation of Ar around the oxygen end of CO and of 26 cm−1 for rotation around the carbon end. The rovibrational spectrum calculated from this potential is in very good agreement with the known experimental data, so that for the first time a realistic level scheme for the ArCO complex can be presented. Couplings between rotational levels of different van der Waals modes play an important role and are analysed in some detail. The intensities of infrared transitions have also been calculated in order to help in the experimental determination of the predicted new van der Waals modes.

Vibrational analysis of glutathione.

Infrared and Raman spectra have been obtained of crystalline glutathione and its deuterated derivative and interpreted by normal mode analysis. The force field consisted of our empirical force fields for the peptide group and NH3+ and CO2- end groups, plus our ab initio force fields for the CH2SH and CH2COOH moieties. Observed bands are reproduced with an average error of 5 cm-1, demonstrating that the vibrational spectrum of such a complex molecule can be understood in great depth.

The in vivo carbon dioxide dissociation curve of true plasma

In thirteen experiments, nine healthy subjects breathed 5 % or 6 % CO 2 in air for periods of up to 80 min. Blood samples were taken before, during and up to 50 min after the end of CO 2 breathing. In three further experiments upon two subjects, blood samples were taken before, during and after a similar period of voluntary hyperventilation. It was found that when blood is equilibrated with different CO 2 pressures in vivo, the change in plasma pH per unit change in plasma bicarbonate (−dpH p/dHCO 3,p −) is greater than when blood is equilibrated in vitro. However -dpHp/dHCO 3,p − is only half the value it would be if the blood were responsible for buffering the entire extracellular space (e.c.f.). It is suggested that the difference may be accounted for in terms of ion transfers across the boundaries of e.c.f.