Model Description of Some Molecular Properties by the Modified-Atom-in-Molecule (MAM) Approach

Conclusive evidence is presented whlch shows that the concept of modified atoms in molecule (MAM) is a viable model for a good description of numerous molecular properties. Atomic modification . can be decomposed to isotropic and anisotropic components. The isotropic change caused by molecular formation is given by the electric monopoles of atoms. It is a consequence of the charge drift accompanying chemical bonding. Atomic monopoles reproduce diamagneticshielding of the nuclei rJAd, diamagnetic susceptibility xd and ESCA shifts with an intriguing success. The atomic monopole model is easily extended to include higher local multipoles (i. e. anisotropic contribution), thus yielding satisfactory total molecular multipoles and extramolecular electrostatic potentials. Salient directional properties of covalent bonds are well described by the use of polarized atomic orbitals. It was shown that hybridization is the underlying concept which explains interrelations between steric features and local bond properties. Hybridization rationalizes in a natural and simple way the electron pair (Lewis) bond which is one of the corner stones of chemistry being particularly important for the first row atoms. It was concluded that the high information content of hybrid AOs can be ascribed to the fact that they conform to the local symmetry of the immediate molecular environment. Thus the HAOs are local wavefunctions of the zeroth order which describe atomic angular distortions. Although atoms can not be uniquely defined within molecules, the MAM model has high interpretative power yielding reasonable results. Special attention deserves a picture of charged atoms immersed in the »sea« of mixed electron density, because it is free of any arbitrariness in the slicing of molecular volume of partitioning of overlap charge. Finally, the definition of pseudo-observables is given. It was concluded that atomic monopoles and hybridization indices are pseudo-observables par exceHence. A.pparently there is colour, apparently sweetness, apparently bitterness; actuaUy there are only atoms and the void. Democritus, 420 B. C

Model Description of Some Molecular Properties by the Modified-Atom-in-Molecule (MAM) Approach

Conclusive evidence is presented whlch shows that the concept of modified atoms in molecule (MAM) is a viable model for a good description of numerous molecular properties. Atomic modification . can be decomposed to isotropic and anisotropic components. The isotropic change caused by molecular formation is given by the electric monopoles of atoms. It is a consequence of the charge drift accompanying chemical bonding. Atomic monopoles reproduce diamagneticshielding of the nuclei rJAd, diamagnetic susceptibility xd and ESCA shifts with an intriguing success. The atomic monopole model is easily extended to include higher local multipoles (i. e. anisotropic contribution), thus yielding satisfactory total molecular multipoles and extramolecular electrostatic potentials. Salient directional properties of covalent bonds are well described by the use of polarized atomic orbitals. It was shown that hybridization is the underlying concept which explains interrelations between steric features and local bond properties. Hybridization rationalizes in a natural and simple way the electron pair (Lewis) bond which is one of the corner stones of chemistry being particularly important for the first row atoms. It was concluded that the high information content of hybrid AOs can be ascribed to the fact that they conform to the local symmetry of the immediate molecular environment. Thus the HAOs are local wavefunctions of the zeroth order which describe atomic angular distortions. Although atoms can not be uniquely defined within molecules, the MAM model has high interpretative power yielding reasonable results. Special attention deserves a picture of charged atoms immersed in the »sea« of mixed electron density, because it is free of any arbitrariness in the slicing of molecular volume of partitioning of overlap charge. Finally, the definition of pseudo-observables is given. It was concluded that atomic monopoles and hybridization indices are pseudo-observables par exceHence. A.pparently there is colour, apparently sweetness, apparently bitterness; actuaUy there are only atoms and the void. Democritus, 420 B. C

Transiente Druckfelder in zweiphasigen Strömungen

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Dominant Role of the pi Framework in Cyclobutadiene

The extrinsic antiaromaticity of archetypal cyclobutadiene (CBD) is addressed with particular emphasis on the sigma-pi separability problem. The destabilization energy E(d)(CBD) of CBD is obtained by appropriate homodesmotic reactions involving the open chain zigzag, polyene(s). It is shown that E(d)(CBD) does not depend on the electron correlation and the zero-point vibrational energy contributions, since they are small and of the opposite sign. Consequently, they cancel in the first approximation. Further, it turns out that E(d)(CBD) can be estimated accurately enough with a very modest cc-pVDZ basis set at the Hartree-Fock (HF) level. The extrinsic antiaromatic destabilization E(ean)(CBD) of CBD is deduced after extracting the angular strain energy estimated to be 32 kcal/mol. The resulting E(ean)(CBD) value of 52 kcal/mol is in excellent agreement with the experimental thermodynamic data. If the E(ean)(CBD) is estimated relative to two isolated C=C double bonds, then it assumes 38 kcal/mol, which is roughly 10 kcal/mol per one pi electron. It is, therefore, safe to state that extrinsic antiaromaticity of CBD is larger than its angular strain. Although the sigma and pi electrons are coupled by a mutual Coulomb interaction V-ee(sigmapi), several attempts of their decoupling is made by using three partitioning schemes: stockholder, equipartition, and standard pi-electron theory recipe. The latter allocates the V-nn and V-ee(sigmapi) terms to the sigma- and pi-electron frameworks, respectively. The nuclear repulsion term V-nn is dissected into sigma and pi components in the former two partitioning schemes by using stockholder criterion. It appears that the extrinsic antiaromatic destabilization E(ean)(CBD) is determined by the pi-electron framework according to all three partitioning models

Lenticulostriate vasculopathy in routine brain ultrasonography in infants: next step?

Lenticulostriate vasculopathy (LSV) is a relatively common fi nding in routine cranial ultrasound examination that has been associated with many infectious and non-infectious conditions. The aim of this review was to provide a better understanding of LSV ultrasound fi nding, as well as the need for further laboratory and imaging examinations in infants. The most of the published studies represented small series, with few prospective long-term studies involving the control groups. Authors have mostly found an association between LSV, especially higher-grade (although there is no universally accepted classifi cation) with congenital cytomegalovirus (CMV) infection, classifying those children as at risk for sensorineural hearing loss. In contrast, some authors pointed out that LSV could be found relatively often, and believe that isolated LSV, especially lower-grade, is not predictive for an unfavourable outcome and a long-term prognosis. Therefore, although 35 years have passed since the fi rst publication of LSV, there is still no consensus among experts on the clinical signifi cance of isolated LSV, but caution is certainly needed given the fact that most infants with congenital CMV are asymptomatic

Surfactant administration in premature infants with RDS

Background. The significant advancement in the treatment of respiratory distress syndrome can be attributed to prenatal identification of high risk pregnancies, prevention of illness through antenatal care, prenatal administration of glucocorticoids, advancement in respiratory support and surfactant therapy. These measures resulted in the reduction of mortality and morbidity rates in preterm infants. Patients and methods. We analyzed data of 78 preterm babies with respiratory distress syndrome hospitalized in the NICU of the Pediatric Clinic, KCU Sarajevo. All children included in the study were mechanically ventilated and treated with one or more doses of bovine surfactant (Survanta) as rescue therapy. Surfactant was given to children with clinical and radiological signs of RDS, who required FiO2>0,40. We used the standard procedure of giving surfactant therapy to intubated children in sterile conditions, after we confirmed, by X-ray, correct tube placement. Results. We investigated the clinical efficacy of surfactant in relation to time of administration, O2 requirement and necessity of one or more doses of surfactant. We found that early treatment with surfactant replacement- within 6 hours of birth- is more effective, and resulted in a significant reduction of mortality rate (p<0,01). Treatment with multiple doses is more effective in comparison to one dose, although there was not a significant difference (p<0,20) between the treated groups. There is a significant difference (p<0,01) between groups related to O2 requirement. In the group of babies which required 60% or more O2 concentration in inhaled air at the time of surfactant replacement, mortality rate was significantly higher (p<0,01). Conclusion. Our study confirmed the benefits of surfactant therapy in preterm babies with respiratory distress syndrome. We confirmed the advantages of early treatment vs. late treatment, but we could not confirm the obvious advantage of multiple over single doses. So, a reasonable recommendation is to treat the infants as soon as clinical signs of developing respiratory distress appear with an individual dose for each infant

Electronic excited state of protonated aromatic molecules: protonated Fluorene

The photo-fragmentation spectrum of protonated fluorene has been recorded in the visible spectral region, largely red shifted as compared to the first excited state absorption of neutral fluorene. The spectrum shows two different vibrational progressions, separated by 0.19 eV that are assigned to the absorption of two isomers. As in protonated linear PAHs, comparison with ab-initio calculations indicates that the red shift is due to the charge transfer character of the excited state

Verification of a new CFD compressible segregated and multi-phase solver with different flux updates-equations sequences

A new solver capable of calculating liquid and/or gas problems has been developed, verified and validated. Compressible solvers in Computational Fluid Dynamics use both mass flux and volumetric fluxes through the cell surface to calculate derivative terms. These fluxes depend on density and velocity fields, therefore the stability of the solver is affected by "how" and "where" density and velocity are calculated or updated. In addition to verification and validation, this paper deals with how different flux updates-equations sequences change the computational solution, reaching the conclusion that for mono-phase solvers no extra-updates should be used in order to minimize computational cost, but for multi-phase solvers with high density gradients an extra-update should be implemented to improve the stability of the solver.This research was funded in the frame the project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo Diesel" reference TRA2013-36932 from Ministerio de Enonomia y Competitividad (Spanish Ministry of Economy).Payri, R.; Ruiz Rosales, S.; Gimeno, J.; Marti-Aldaravi, P. (2015). Verification of a new CFD compressible segregated and multi-phase solver with different flux updates-equations sequences. Applied Mathematical Modelling. 39(2):851-861. https://doi.org/10.1016/j.apm.2014.07.011S85186139