Search

Background: Early in the COVID-19 pandemic, it became apparent that members of marginalized populations and immigrants were also at risk of being hospitalized and dying more frequently from COVID-19. To examine how the pandemic affected underserved and marginalized populations, we analyzed data on changes in the number of deaths among people with and without Swiss citizenship during the first and second SARS-CoV-2 waves., Method: We analyzed the annual number of deaths from the Swiss Federal Statistical Office from 2015 to 2020, and weekly data from January 2020 to May 2021 on deaths of permanent residents with and without Swiss citizenship, and we differentiated the data through subdivision into age groups., Results: People without Swiss citizenship show a higher increase in the number of deaths in 2020 than those who were Swiss citizens. The increase in deaths compared to the previous year was almost twice as high for people without Swiss citizenship (21.8%) as for those with it (11.4%). The breakdown by age group indicates that among people between the ages of 64 and 75, those without Swiss citizenship exhibited an increase in mortality (21.6%) that was four times higher than that for people with Swiss citizenship (4.7%)., Conclusion: This study confirms that a highly specialized health care system, as is found in Switzerland, does not sufficiently guarantee that all parts of the population will be equally protected in a health crisis such as COVID-19., Competing Interests: Author SM was employed by Demo SCOPE AG. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Plümecke, Mikosch, Mohrenberg, Supik, Bartram, Ellebrecht, zur Nieden, Schnieder, Schönberger, Schulze-Marmeling and Gutzeit.)

This paper examines the incidence of firm bankruptcies and start-ups in Switzerland based on unique register data. We propose to assess the frequency of bankruptcies over time using the concept of excess mortality. During the COVID-19 crisis in 2020 and the first half of 2021, bankruptcy rates were substantially lower as compared to the pre-crisis period. This holds across most industries and regions. The Great Recession and the Swiss Franc Shock showed reverse patterns. Bankruptcies dropped more in industries and cantons, in which the share of firms who received a COVID-19 loan is comparatively high. In winter 2021, bankruptcies rebounded strongly. Since summer 2020, the number of new firm formations has been significantly higher compared to the time before the crisis. This is also in contrast to the previous crises. The strong start-up activity is driven by industries where the pandemic induced structural adjustments., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2022.)

This paper documents daily compound indicators on physical mobility and sales activity in Switzerland during the Corona crisis. We report several insights from these indicators: The Swiss population substantially reduced its activities already before the shops closed and before the authorities introduced containment policies in mid-March 2020. Activity started to gradually recover from the beginning of April onwards, again substantially before the first phase of the shutdown easing started at the end of April. Low physical mobility during the second half of March and during April likely contributed to the quick fall in new COVID-19 infections since mid-March. The sharp drop in economic activity in consumer-related services during March and April and the gradual recovery in these sectors since May correlate strongly with the reduction and subsequent gradual resurgence of mobility. In addition, while activity within Switzerland was back to normal levels by late June, activity of Swiss residents outside of Switzerland was still below normal., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2020.)

The adsorption of sulphur multilayers on Au(100) has been studied using density functional theory (DFT) within the generalized gradient approximation (GGA). The first sulphur layer was adsorbed on the four-fold sites of the unreconstructed Au(100) surface forming a lattice. The experimental parameters of the lattice were reproduced taking into account the surface expansion of the topmost Au(100) layer. This expansion should occur when gold islands are formed after the lifting of hex-reconstruction, which allows the lateral movement of the gold atoms. The second sulphur layer, on top of the lattice, consisted of eight S atoms (octomer phase) in a quasi-rectangular arrangement. The structural optimization of the octomer phase was achieved in a specific spatial orientation with respect to the lattice. The analysis of Bader atomic charges and the projected density of states (PDOS) demonstrated that charge transfer from the Au(100) surface to the sulphur layers, sulphur chemisorption and sulphur-sulphur inter-layer mixing of electronic states control the formation of sulphur multilayers.

The adsorption of nitric oxide as dinitrosyls and the deNOx proton-mediated reaction mechanism are assessed using electronic structure methods and transition state theory. Dinitrosyls bind to copper cations either via a N-atom or via an O-atom, with N-binding being more stable. In their ground states, dinitrosyls reach a planar configuration with the metal cation. The two nitric oxide molecules are kept together in O-bonded dinitrosyls by the N-N bond and the adsorption complex obtains a cyclic planar structure, while N-bonded dinitrosyls have out-of-plane conformations with low energy barriers. An asymmetric structure ZCu(ON)(NO) with one N-bonded nitrosyl and the other O-bonded is of the lowest stability. The cyclic hyponitrite ZCu(ON)2 adsorption complex undergoes O-N bond breaking upon protonation of one oxygen atom and this lowers the energy barrier of the first reaction step of nitric oxide dissociation to yield N2O and a hydroxylated copper site ZCu(OH) by 45 kJ mol(-1) for Cu-SAPO-34 and by 46 kJ mol(-1) for Cu-SSZ-13. The more stable N-bonded dinitrosyl ZCu(NO)2 provides less favorable reaction which passes through the asymmetric ZCu(ON)(NO) intermediate structure. Brønsted acid sites facilitate the reversal of one nitrosyl group. The role of proton transfer from a Brønsted acid site to dinitrosyls is not limited to the initial step of facilitating the N-O bond cleavage, but it also contributes to the stabilization of intermediate oxygen species formed at the copper site as hydroxide ZCu(OH) and hydroperoxide, ZCuOOH. Without protonation, the unstable ZCuO intermediate causes structural deformation with strongly lengthened T-O bonds in the framework. The rate determining step is N2O decomposition to N2 and O2, whether starting with a ZCu(NO)2 or a ZCu(ON)2 adsorption complex, and Cu-SSZ-13 has a clear advantage with an energy barrier of 195 kJ mol(-1)vs. 265 kJ mol(-1) for Cu-SAPO-34. In the final step the Brønsted acid site is restored by proton transfer from the hydroperoxide ZCuOOH to the framework and molecular oxygen is released. The overall energy barrier for the proton-assisted reaction of ZCu(ON)2 decomposition for Cu-SSZ-13 is by 48 kJ mol(-1) lower than the barrier of the proton-free pathway.

The molecular properties, geometric parameters, atomic charges, and vibrational spectra of sodium 1,2,4-triazolate were investigated with both experimentally and quantum chemical modeling. During the quantum chemical calculations the possible tautomery and the aqueous environment were considered since the compound is hygroscopic. The polar environment was modeled as an aqueous solvent, and by adding water molecules as structural water. The two kinds of effects were also applied together., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The infrared and Raman spectra of dehydroacetic acid and some of its derivatives were measured. The assignments of the vibrational bands were based on quantum chemical calculations and normal coordinate analysis. The optimized structures, atomic net charges and dipole moments of the investigated molecules were also results of our quantum chemical calculations. The analysis of the last properties made possible a deeper insight into the structure and substituent effect on the investigated molecules. One of them is presented in the graphical abstract., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The mechanism of carbon dioxide reduction to methanol on Cu(I) oxide nanolayers and clusters using water as the source of hydrogen was traced using density functional theory. The nature of the active sites is revealed, namely the role of surface copper dimers, which are present on the Cu2O(001) surface and in the nanoclusters of size Cu32O16 and Cu14O7. The major difference between metal catalysts and Cu2O is outlined: the CO2 molecule interacts strongly with the oxide and undergoes bending prior to hydrogenation. The first step of CO2 hydrogenation results in the formation of a stable carboxyl intermediate, -CO(OH), which in the following steps is converted to methanol via formic acid and formaldehyde intermediates. The consumption of hydrogen from water leaves surface peroxo- and hydroperoxo-species. The peroxides easily desorb molecular oxygen, while for hydroperoxides the reaction of oxygen evolution requires an activation energy of 130 kJ mol(-1). The maxima in the absorption spectra correspond well with the required activation energies in the elementary steps.

The iron sulfide dimers (FeS)2 and their persulfide isomers with S-S bonds are studied with the B3LYP density functional as bare clusters and as hexacarbonyls. The disulfides are more stable than the persulfides as bare clusters and the persulfide ground state lies at 3.2 eV above the global minimum, while in the hexacarbonyl complexes this order is reversed: persulfides are more stable, but the energy gap between disulfides and persulfides becomes much smaller and the activation barrier for the transition persulfide → disulfide is 1.11 eV. Carbonylation also favors a non-planar Fe2S2 ring for both the disulfides and the persulfides and high electron density in the Fe2S2 core is induced. The diamagnetic ordering is preferred in the hexacarbonyls, unlike the bare clusters. The hexacarbonyls possess low-lying triplet excited states. In the persulfide, the lowest singlet-to-triplet state excitation occurs by electron transition from the iron centers to an orbital located predominantly at S2 via metal-to-ligand charge transfer. In the disulfide this excitation corresponds to ligand-to-metal charge transfer from the sulfur atoms to an orbital located at the iron centers and the Fe-Fe bond. Water splitting occurs on the hexacarbonyls, but not on the bare clusters. The singlet and triplet state reaction paths were examined and activation barriers were determined: 50 kJ mol(-1) for HO-H bond dissociation and 210 kJ mol(-1) for hydrogen evolution from the intermediate sulfoxyl-hydroxyl complexes Fe2S(OH)(SH)(CO)6 formed. The lowest singlet-singlet excitations in the hexacarbonyls, the water adsorption complexes and in the reaction intermediates, formed prior to dihydrogen release, fall in the visible light region. The energy barrier of 210 kJ mol(-1) for the release of one hydrogen molecule corresponds to one visible photon of 570 nm. The dissociation of a second water molecule, followed by H2 and O2 release via hydro-peroxide intermediate is a two-step process, with activation barriers of 218 and 233 kJ mol(-1), which also fall in the visible light region. A comparison of the full reaction path with that on diiron dioxide hexacarbonyls Fe2O2(CO)6 is traced.

Experimental scanning tunneling microscopy (STM) studies have shown for more than two decades rectangular formations when sulfur atoms are deposited on Au(111) surfaces. The precursors have ranged from simple molecules or ions, such as SO2 gas or sulfide anions, to more complex organosulfur compounds. We investigated, within the framework of the Density Functional Theory, the structure of these rectangular patterns assuming them entirely composed of sulfur atoms as the experimental evidence suggests. The sulfur coverage at which the simulations were carried out (0.67 ML or higher) provoked that the sulfur-sulfur association had to be taken into account for achieving a good agreement between the sets of simulated and experimental STM images. A combination of four sulfur dimers per rectangular formation properly explained the trends obtained by the experimental STM analysis which were related with the rectangles' size and shape fluctuations together with sulfur-sulfur distances within these rectangles. Finally, a projected density of states analysis showed that the dimers were capable of altering the Au(5d) electronic states at the same level as atomic sulfur adsorbed at low coverage. Besides, sulfur dimers states were perfectly distinguished, whose presence near and above the Fermi level can explain both: sulfur-sulfur bond elongation and dimers stability when they stayed adsorbed on the surface at high coverage.

The iron oxide dimers (FeO)2 and their peroxide isomers are studied with the B3LYP density functional as bare clusters and as hexacarbonyls. Among the bare clusters the planar four-member ring structures are more stable than the non-planar ones and the rhombic dioxide Fe2O2 with antiferromagnetically ordered electrons on iron centers is the global minimum. Water adsorption on the bare diiron dioxide is exothermic, but dissociation does not occur. Carbonylation favors a non-planar Fe2O2 ring for both the dioxides and the peroxides and high electron density at the Fe centers is induced, evidenced by the natural charge distribution, the high proton affinity, and the values of global electronegativity and hardness. The iron dioxide hexacarbonyl Fe2O2(CO)6 is diamagnetic in the state of the global minimum. It is separated from the next low-lying triplet state by a small energy gap of 0.22 eV. Time-dependent density functional theory methods were applied to examine electron excitations from the ground state to the low-lying triplet states in the hexacarbonyls and their adsorption complexes with water. Singlet-to-triplet state excitations occur via ligand-to-metal charge transfer in the hexacarbonyls; in the adsorption complexes excitations from the oxygen lone pairs to the adsorption center also occur and they appear in the IR-visible region. The lowest energy singlet and triplet state reaction paths for water splitting were followed. On the singlet potential energy surface (PES), water splitting is spontaneous, while for the triplet PES an activation barrier of 14.1 kJ mol(-1) was determined.

Parallel ligand- and structure-based virtual screenings of 269 steroids with anabolic activity evaluated in vivo were performed. The quantitative structure-activity relationship (QSAR) model expressed by selected descriptors as the octanol-water partition coefficient, the molar volume and the quantum mechanical calculated charge values on atoms C1, C2, C5, C9, C10, C14 and C17 of the steroid skeleton, expresses structural features of anabolic steroids (AS) contributing to the transport and steroid-receptor interaction. On the other hand, computational simulations of a candidate ligand binding to a receptor study (a "docking" procedure) predict the association of these AS with the human androgen receptor (AR). Fourteen compounds were identified as lead; the most potent was the 7α-methylestr-4-en-3, 17-dione. It was concluded that a good anabolic activity requires hydrogen bonding interactions between both Arg752 and Gln711 residues in the cycles A with O3 atom of the steroid and either Asn705 and Thr877 residues in the cycles D of steroid with O17 atom., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Carvedilol (CRV) is an important medicament for heart arrhythmia. The aim of this work was the interpretation of its vibrational spectra with consideration on the solvent effect. Infrared and Raman spectra were recorded in solid state as well in solution. The experimental spectra were evaluated using DFT quantum chemical calculations computing the optimized structure, atomic net charges, vibrational frequencies and force constants. The same calculations were done for the molecule in DMSO and aqueous solutions applying the PCM method. The calculated force constants were scaled to the experimentally observed solid state frequencies. The characters of the vibrational modes were determined by their potential energy distributions. Solvent effects on the molecular properties were interpreted. Based on these results vibrational spectra were simulated., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Quantum chemical model calculations were carried out for modeling the ion transport through an isolated ion channel of a cell membrane. An isolated part of a natural ion channel was modeled. The model channel was a calixarene derivative, hydrated sodium and potassium ions were the models of the transported ion. The electrostatic potential of the channel and the energy of the channel-ion system were calculated as a function of the alkali ion position. Both attractive and repulsive ion-channel interactions were found. The calculations - namely the dependence of the system energy and the atomic charges of the water molecules with respect to the position of the alkali ion in the channel - revealed the molecular-structural background of the potassium selectivity of this artificial ion channel. It was concluded that the studied ion channel mimics real biological ion channel quite well.

The dimers of cobalt oxide (CoO)(2) with cyclic and open bent structure are studied with the B1LYP density functional; the ordering of states is validated by the CCSD(T) method. The D(2h)-symmetry rhombic dioxide Co(2)O(2) with antiferromagnetically ordered electrons on cobalt centers is the global minimum. The cyclic peroxide Co(2)(O(2)) with side-on-bonded dioxygen in (7)B(2) ground state is separated from the global minimum by an energy gap of 3.15 eV. The dioxide is highly reactive as indicated by the high value of proton affinity and chemical reactivity indices. The four-member ring structures are more stable than those with three-member ring or chain configuration. The thermodynamic stability toward dissociation to CoO increases upon carbonylation, whereas proton affinity and reactivity with release of molecular oxygen also increase. The global minimum of Co(2)O(2)(CO)(6) corresponds to a triplet state (3)A" with oxygen atoms shifted above the molecular plane of the rhombic dioxide Co(2)O(2). The SOMO-LUMO gap in the ground-state carbonylated dioxide is wider, compared to the same gap in the bare dicobalt dioxide. The peroxo-isomer Co(2)(O(2))(CO)(6) retains the planar Co(2)(O(2)) ring and is only stable in a high-spin state (7)A". The carbonylated clusters have increased reactivity in both redox and nucleophilic reactions, as a result of the increased electron density in the Co(2)O(2)-ring area.

For studying both hydrogen bond and dipole-dipole interactions between methanol molecules (self-association) the geometry of clusters of increasing numbers of methanol molecules (n = 1,2,3) were optimized and also their vibrational frequencies were calculated with quantum chemical methods. Beside these B3LYP/6-311G** calculations, PCM calculations were also done for all systems with PCM at the same quantum chemical method and basis set, for considering the effect of the liquid continuum on the cluster properties. Comparing the results, the measured and calculated infrared spectra are in good accordance., (This journal is © the Owner Societies 2011)

In the present paper, indole and its seven derivatives were compared, namely 3-formylindole, 1-methyl-3-formylindole, 1-ethyl-3-formylindole, 3-acetylindole, 1-methyl-3-acetylindole, 1-ethyl-3-acetylindole and 1,3-diacetylindole. The substitution of indole in position 3 with aldehydes and with alkyl groups cause only minor changes in the molecular geometry, however, substantially larger alterations are found in the charge distribution and in the vibrational force constants. The appearance of the aldehyde groups increased the degree of association as it was observable on the shape of infrared NH stretching band and its shifts. The alkyl substitution shifts the aldehyde carbonyl stretch band frequencies to somewhat higher values. The effect of the second acetyl group in position 1 is not comparable with those of the 1-alkyl groups. The latter effect is observable in the molecular geometry, however, it is more pronounced in the changes of the net charge distribution, the vibrational force constants and the infrared spectra.

The 3d-element transition metal dioxide MO(2), peroxide M(O(2)), and superoxide MOO clusters (M=Sc-Zn), are studied by density functional theory with the B1LYP functional. The reliability of the methods and basis sets employed was tested by a reinvestigation of the monoxides, for which a database of experimental data is available. The global minima on the M+O(2) potential energy surfaces correspond to dioxide structure, the only exception being CuOO, with a superoxide structure. All Zn dioxygen clusters are thermodynamically unstable-their ground states lie higher than the dissociation limit to Zn+O(2). Our calculations are in favor of the high-spin configurations for the FeO(2), CoO(2), and NiO(2) ground states, which are still a subject of extensive theoretical and experimental studies. These assignments are confirmed by the coupled-cluster method, CCSD(T), except for NiO(2). Based on the existence of a stable NiO(2) monoanion in a (4)B(1) state, however, it can be concluded that NiO(2) in its (5)A(1) state should also be stable. The vibrational frequencies are calculated for clusters entrapped in the cubic cell of solid Ar matrix and compared with those obtained for gas-phase clusters. The matrix has no influence on the vibrations of the monoxides and most of the dioxides; however, Co and Ni-dioxoclusters interact strongly with the atoms from the noble gas matrix. The most intense frequencies in the IR spectra are shifted to lower energies and the ordering of the low-lying electronic states by stability is also reversed. According to the electrostatic potential maps, the oxygen atoms in the peroxides are more nucleophilic than those in the dioxides and superoxides. The terminal oxygen atom in superoxides is more nucleophilic than its M-bonded oxygen atom, though charge distribution analysis predicts a smaller negative charge on the terminal oxygen. TiO(2) is the only dioxide in which nucleophilic character in the vicinity of the metal cation is induced.

Compounds formed by exchanging one of the resveratrol hydroxy groups to methoxy or formyl groups are biologically important. Quantum chemical DFT calculations were applied for the simulation of some of their properties. Their optimized structures and charge distributions were computed. Based on the calculated vibrational force constants and optimized molecular structure infrared and Raman spectra were calculated. The characteristics of the vibrational modes were determined by normal coordinate analysis. Applying the calculated thermodynamic functions also for resveratrol, methanol, formaldehyde and water, thermodynamic equilibria were calculated for the equilibria between resveratrol and its methyl and formyl substituted derivatives, respectively.

In this article the authors deal with the experimental and theoretical interpretation of the vibrational spectra of trans-resveratrol (3,5,4'-trihydroxy-trans-stilbene) of diverse beneficial biological activity. Infrared and Raman spectra of the compound were recorded; density functional calculations were carried out resulting in the optimized geometry and several properties of the molecule. Based on the calculated force constants, a normal coordinate analysis yielded the character of the vibrational modes and the assignment of the measured spectral bands.

Twelve H-bonded supersystems constructed between the adenine tautomers and methanol, ethanol, and i-propanol were studied at the B3LYP and MP2 levels of theory using 6-311G(d,p) and 6-311++G(d,p) basis functions. The thermodynamic parameters of the complex formations were calculated in order to estimate the exact stability of the supersystems. It was proven that the calculated energy barriers of the alcohol-assisted proton transfers are about 60% lower than those of the intramolecular proton transfers in adenine found earlier (Gu and Leszczynski in J Phys Chem A 103:2744-2750, 1999).

Eight H-bonded complexes between isocytosine (isoC) tautomeric forms and R/S-lactic acid (LA) have been studied at the B3LYP and HF levels of theory using 6-31+G(d) basis set. The energy barriers of the intermolecular proton transfers were also estimated as the results showed that they are several times lower than those of the intramolecular proton transfers of isoC in the gas phase. Furthermore, the energy barriers of the tautomerizations in which the carboxylic H-atom takes part are several times lower than those in which the LA OH group assists the proton transfer.

The structure of four natural mycotoxins, the aflatoxin B1, B2, G1 and G2 and their demethylated products were optimized with quantum chemical method. The energies and the thermodynamic functions of the molecules were calculated and applied to calculation of the reaction energies of the demethylations. Further results of the calculations are the vibrational force constants, the infrared spectra of the molecules and the assignments of the spectral bands.

Eight H-bonded complexes between serotonin (5-hydroxy-tryptamine) and water/hydrogen peroxide were studied at the B3LYP and HF levels of theory, using the 6-31+G(d) basis set. A thermodynamic analysis was performed in order to find the most stable complex. The calculated bonding parameters showed that the most stable H-bonded complex is formed between serotonin and hydrogen peroxide by means of the intermolecular H-bond -H2N...H-OOH. Theoretical study of the hydrogen-bonded supersystems serotonin-water/hydrogen peroxide. [Figure: see text].

A computational study of hydrogen-bonded complexes between the oxo-/hydroxo-amino N7/9H tautomers of guanine and water, methanol, and hydrogen peroxide has been performed at the B3LYP/6-31 + G(d) level of theory. The mechanisms of the water-, methanol-, and hydrogen peroxide-assisted proton transfers in guanine were studied and compared with the intramolecular proton transfer in guanine in the gas phase. It was found that the assisted proton transfers pass through about three times lower energy barriers than those found for isolated guanine tautomers.

Five stable H-bonded complexes (supersystems) between acetylacetone and two methanol molecules were investigated at the B3LYP and HF levels of theory using the 6-311G** and 6-11++G** basis sets. The most stable complex was found as the one with the highest relative bonding and interaction energies. All vibrational frequencies resulting from calculations with the 6-311++G** basis set were compared with the recorded IR spectrum of acetylacetone/methanol mixture in a molar ratio 1:2.

The interaction of N(2) and O(2) with extraframework cations of zeolite frameworks was studied by DFT, using the B3LYP method. The extraframework cation sites located in the vicinity of the double six-member rings (D6R) of FAU zeolites (SI, SI', SIII') were considered and clusters with composition (M(n)(+))(2/)(n)()H(12)Si(10)Al(2)O(18), M = Li(+), Na(+), K(+), Ca(2+), were selected to represent the adsorption centers. The cation sites SII in the center of single six-membered rings (S6R) were modeled by [M(I)H(12)Si(4)Al(2)O(6)](-) and M(II)H(12)Si(4)Al(2)O(6) clusters. The adsorption energy of N(2) and O(2) is the highest for Li(+) cations at the SIII' cation sites, while for the SI' and SII sites the adsorption energies decrease in the order Ca(2+) > Na(+) > Li(+). The calculated small N(2) adsorption energy for Li(+) cations at SII sites suggests that these sites do not take part in the sorption process in agreement with results of NMR studies and Monte Carlo simulations. The N(2) adsorption complexes with the extraframework cations are linear, while those of O(2) are bent regardless of the extraframework cation location. The SIII' cation sites are the most favorable ones with respect to N(2) adsorption capacity and N(2)/O(2) selectivity; the SII sites are less selective and the SI sites are not accessible.

The 3d-transition-metal dioxo-, peroxo-, and superoxoclusters with the general composition MO2, M(O2), and MOO (M = Mn, Fe, Co, and Ni) were studied by DFT by the B1LYP functional. The dioxides in their ground states represent the global minima for the M + O2 system. Both ground-state dioxides and the lowest-energy peroxides are in their (d-only) highest spin states. The 6A1 state of Co(O2) exceeds the d-only spin-multiplicity value (quartet), being nearly isoenergetic with the 4A1 state of Co(O2). The energy gain on transforming the peroxides to the corresponding dioxides decreases in the order Mn(O2) > Fe(O2) > Co(O2) > Ni(O2) and varies in the range 0.27-1.8 eV. The dissociation energy to M + O2 for all studied peroxides is less than 1 eV being the lowest (0.47 eV) for Mn(O2). The Mn and Fe peroxides need less than 0.3 eV to rupture one of the MO bonds to form the corresponding superoxide. Mn and Fe superoxides are less stable than the corresponding peroxides; the superoxide of Co is more stable than its peroxide, while Ni superoxide is unstable--its energy is above the limit of dissociation to Ni + O2. According to the electrostatic potential maps, the oxygen atoms in the peroxides are more nucleophilic than those in the dioxides and superoxides, in which the terminal oxygen atom is more nucleophilic than the M-bonded oxygen atom. This result differs from the expectations based on charge-distribution analysis.

Intestinal infarction in the absence of organic vascular occlusion received increasing attention in recent years. There is strong evidence from experimental work and clinical observations that cardiac glycosides may play an important role in the pathophysiology of this disorder. Our experiments using the so called mechanical ventricular massage confirm this theory. We could demonstrate that the decrease in mesenteric arterial perfusion following the i.v. administration of ouabain is caused by extracardiac effects of the glycoside on vascular smooth muscle. The Ca++ -antagonistic compound (Verapamil) blocks and reverses the Ca++-synergistic action of the glycoside independent of the time of injection.

The vasoconstrictor effects of strophanthin on mesenteric hemodynamics were studied using mechanical ventricular massage to exclude the cardiac effects of the drug. The administration of a calcium antagonistic compound prior to digitalis, together with and after digitalis application, prevented the vasoconstrictor response completely. From our experimental experience the combination of cardiac glycosides with calcium antagonistic compounds seems rational.