A study on the rapid diagnosis of chronic heart failure by measuring the difference in pulse oxygen saturation before and after arm compression.

BACKGROUND: Clinically, the pulse oxygen saturation of patients with chronic heart failure does not decrease significantly, and the clinical manifestations of labor-related dyspnea are not typical. As such, it is difficult to make a rapid diagnosis. OBJECTIVE: To investigate changes in pulse oxygen saturation in patients with chronic heart failure and examine the relationship between B-type natriuretic peptide (BNP) and normal pulse oxygen saturation. METHODS: A total of 80 hospitalized patients with chronic heart failure and increased BNP were randomly selected as the study group; the family members of 60 patients without dyspnea were randomly selected as the control group. The researchers measured the value of pulse oxygen saturation before and after upper arm compression, calculating the difference and analyzing the correlation between this difference and BNP values. The data were statistically analyzed using the SPSS Statistics 17.0 program. RESULTS: The decrease in pulse oxygen saturation in the study group was greater than in the control group; the decrease in pulse oxygen saturation of patients with chronic heart failure positively correlated with BNP. CONCLUSION: The value of pulse oxygen saturation in patients with chronic heart failure decreased more than in the control group, and this difference positively correlated with BNP. The measurement of pulse oxygen saturation before and after upper arm compression is a simple and effective method for diagnosing and evaluating chronic heart failure.

A density functional theory study of a water gas shift reaction on Ag(111): potassium effect.

Density functional theory (DFT) calculations are executed to investigate the effect of a potassium (K) promoter on the activity of the water gas shift reaction (WGSR) over an Ag(111) surface. It is found that the WGSR proceeds mainly through the OH(O)-assisted carboxy pathway in which H2O dehydrogenation is the rate-controlling step on both Ag(111) and K/Ag(111) surfaces. Energetic span model analysis shows that K addition can enhance the activity of the WGSR by reducing the apparent activation energy of the whole reaction since it can promote H2O dissociation and stabilize the adsorption of the reactants (CO and H2O). Importantly, the K adatom can stabilize the binding of all oxygenates by direct K-O bonding and the stabilizing effect of K on OH adsorption of the transition state (TS) plays a leading role in promoting H2O dissociation. Moreover, the K-O distance and K coverage are two key factors affecting H2O activation, that is, the shorter the K-O distance (2-3 Å) the more the K coverage (25%) contributes to the stronger promotion effect. For various metals catalyzing the WGSR, K promotes H2O dissociation on inert metals like Ag, Au and Cu better than those on reactive metals (Pd and Ni) since the more inert metal surfaces would weaken the K and O binding and accordingly strengthen the interaction between them, resulting in a higher promotion effect.

Dissociative adsorption modes of TATB on the Al (111) surface: a DFT investigation.

Herein, the adsorption modes and electronic structures of TATB/Al (111) systems were investigated using the density functional theory (DFT) approach. We found that chemical adsorption led to the decomposition of the TATB molecule on the Al surface by four adsorption modes. All the adsorption configurations were accompanied by fractures of the N-O bonds in the nitro groups. In addition, there was a hydrogen atom transfer for 5P. For parallel and vertical adsorptions, the TATB molecules favored planar or quasi-planar structures. The order of total energy with BSSE correction matches well with the order of adsorption energy. The absolute values of energy and adsorption energy of 6P and 6V are highest in the parallel and vertical adsorption systems, respectively. Electrons are transferred from the Al (111) surface to the TATB molecule; this results in the activation of TATB on the Al (111) surface and obvious augmentation of the PDOS (partial density of states) peaks of the N and O atoms. From the Al (111) surface to the TATB molecule, the transfer of the electrons of 4P (14.00e) and 6V (9.04e) is largest for the parallel and vertical adsorptions, respectively.

The generalized block-localized wavefunction method: a case study on the conformational preference and C-O rotational barrier of formic acid.

A Lewis structure corresponding to the most stable electron-localized state is often used as a reference for the measure of electron delocalization effect in the valence bond (VB) theory. As the simplest variant of ab initio VB theory, the generalized block-localized wavefunction (BLW) method defines the wavefunction for an electron-localized state with block-localized orbitals without the orthogonalization constraint on different blocks. The validity of the method can be critically examined with experimental evidences. Here the BLW method has been applied to the investigation of the roles of both the π conjugation and σ hyperconjugation effects in the conformational preference of formic acid for the trans (Z) conformer over the cis (E) conformer. On one hand, our computations showed that the deactivation of the π conjugation or σ hyperconjugation has little impact on the Z-E energy gap, thus neither is decisive and instead the local dipole-dipole electrostatic interaction between the carbonyl and hydroxyl groups is the key factor determining the Z-E energy gap. On the other hand, the present study supported the conventional view that π conjugation is largely responsible for the C-O rotation barrier in formic acid, though the existence of hyperconjugative interactions in the perpendicular structure lowers the barrier considerably.

A computational study on the chemical fixation of carbon dioxide with epoxide catalyzed by LiBr salt.

The chemical fixation of carbon dioxide with 2,3-epoxypropyl phenyl ether catalyzed by LiBr salt to produce a five-membered cyclic carbonate, 4-(phenoxymethyl)-1,3-dioxolan-2-one, has been extensively investigated at the B3LYP density functional level of theory. The solvent effects have been studied by means of a PCM model. All possible pathways are examined, and their corresponding energetics are demonstrated. Our results reveal that the overall reaction comprises three main steps: epoxide ring-opening, carbon dioxide insertion, and ring-closure of cyclic carbonate, none of which contains significantly large barriers. On the basis of the computed free energies of activation, the rate-determining step can be the ring-opening of epoxide or the ring-closure of cyclic carbonate with variation in the reaction conditions in N-methylpyrrolidinone (NMP) solvent. Our calculations indicate that path 2 is more favorable than path 1 in the gas phase, while both of them exist possibly in NMP solvent. The overall reaction is exothermic. Furthermore, the free energy profiles of all reaction pathways along the minima energy path in the gas phase and in NMP solvent were obtained and compared. It is shown that NMP solvent does not change the general trends for the reaction potential energy surfaces.

Ligand effects on structures and spectroscopic properties of pyridine-2-aldoxime complexes of Re(CO)3(+): DFT/TDDFT theoretical studies.

The series of novel rhenium(I) tricarbonyl mixed-ligand complexes Re(X)(CO)(3)(N^N) (N^N = pyridine-2-aldoxime; X = -Cl, 1; X = -CN, 2; and X = -C≡C, 3) has been investigated theoretically to explore the ligand X effect on their electronic structures and spectroscopic properties. The contribution of the X ligand to the highest occupied molecular orbital (HOMO) and HOMO-1 decreases in the order of 3 > 1 > 2, in line with the π-donating abilities of the X: -C≡C > -Cl > -CN. The reorganization energy (λ) calculations show that 1 and 3 will result in the higher efficiency of organic light-emitting diodes than 2. The lowest-lying absorptions of 1 and 3 can be assigned to the {[d(xz), d(yz)(Re) + π(CO) + π(X)] → [π* (N^N)]} transition with mixing metal-to-ligand, ligand-to-ligand, and X ligand-to-ligand charge transfer (MLCT/LLCT/XLCT) character, whereas this absorption at 354 nm (H-1 → L) of 2 is assigned to {[d(xz), d(yz)(Re) + π(CO) + π(N^N)] → [π* (N^N)]} transition with MLCT/LLCT/ILCT (intraligand charge transfer). Furthermore, the absorptions are red-shifted in the order 2, 1, and 3, with the increase of π-donating abilities of X ligands. The solvent effects cause red shifts of the absorption and emission spectra with decreasing solvent polarity.

Substituent and solvent effects on electronic structure and spectral property of ReCl(CO)3(N∧N) (N∧N = glyoxime): DFT and TDDFT theoretical studies.

The ground- and excited-state structures of five Re(I) halide glyoxime complexes ReCl(CO)(3)(N(∧)N) (N(∧)N = glyoxime (DHG 1), dimethylglyoxime (DMG 2), cyclohexane dione glyoxime (CHDG 3), dibromoglyoxime (DBG 4), and dimethylformylgloxime (DMFG 5)) have been studied with density functional theory (DFT) and configuration interaction with single excitations (CIS) methods. Time-dependent density functional theory/polarized continuum model (TDDFT/PCM) was carried out to predict the absorption and emission spectra in different media. The effect of substituent and solvent has been researched. It is found that electron-donating groups increase the lowest unoccupied molecular orbital (LUMO) energy resulting in the increased highest occupied molecular orbital (HOMO)-LUMO energy gap. The change leads to their absorption spectra blue shifts in the order 1 > 2 > 3, which arises from the HOMO-1 → LUMO. Just the opposite, electron-withdrawing groups lead to the spectra red shifts (5 > 4 > 1) because of the decreased HOMO-LUMO energy gap. The reorganization energy (λ) calculations show that the relatively balanceable charges transfer abilities of 2 will result in the higher efficiency of organic light emitting devices (OLEDs). In addition, both the absorption and the emission spectra display red shifts in different extents with the decrease of solvent polarity.