Relativistic effects in physics and chemistry of element 105. [Part] III.

Electronic structures of MOCl_3 and MOBr_3 molecules, where M = V, Nb, Ta, Pa, and element 105, hahnium, have been calculated using the relativistic Dirac-Slater discrete variational method. The character of bonding has been analyzed using the Mulliken population analysis of the molecular orbitals. It was shown that hahnium oxytrihalides have similar properties to oxytrihalides of Nb and Ta and that hahnium has the highest tendency to form double bond with oxygen. Some peculiarities in the electronic structure of HaOCl_3 and HaOBr_3 result from relativistic effects. Volatilities of the oxytrihalides in comparison with the corresponding pentahalides were considered using results of the present calculations. Higher ionic character and lower covalency as well as the presence of dipole moments in MOX_3 (X = Cl, Br) molecules compared to analogous MX_5 ones are the factors contributing to their lower volatilities.

Relativistic effects in physics and chemistry of element 105. [Part] IV.

Results of relativistic (Dirac-Slater and Dirac-Fock) and nonrelativistic (Hartree-Fock-Slater) atomic and molecular calculations have been compared for the group 5 elements Nb, Ta, and Ha and their compounds MCl_5, to elucidate the influence of relativistic effects on their properties especially in going from the 5d element Ta to the 6d element Ha. The analysis of the radial distribution of the valence electrons of the metals for electronic configurations obtained as a result of the molecular calculations and their overlap with ligands show opposite trends in behavior for ns_1/2, np_l/2, and (n -1 )d_5/2 orbitals for Ta and Ha in the relativistic and nonrelativistic cases. Relativistic contraction and energetic stabilization of the ns_1/2 and np_l/2 wave functions and expansion and destabilization of the (n-1)d_5/2 orbitals make hahnium pentahalide more covalent than tantalum pentahalide and increase the bond strength. The nonrelativistic treatment of the wave functions results in an increase in ionicity of the MCl_5 molecules in going from Nb to Ha making element Ha an analog of V. Different trends for the relativistic and nonrelativistic cases are also found for ionization potentials, electronic affinities, and energies of charge-transfer transitions as well as the stability of the maximum oxidation state.

Cooperative Physics of Fly Swarms: An Emergent Behavior

We have simulated the behavior of several artificial flies, interacting visually with each other. Each fly is described by a simple tracking system (Poggio and Reichardt, 1973; Land and Collett, 1974) which summarizes behavioral experiments in which individual flies fixate a target. Our main finding is that the interaction of theses implemodules gives rise to a variety of relatively complex behaviors. In particular, we observe a swarm-like behavior of a group of many artificial flies for certain reasonable ranges of our tracking system parameters.

Make progress with physics and chemistry. 'Haz progresos con física y química'.

Seleccionado en la convocatoria: Licencias por estudios destinadas a funcionarios docentes no universitarios, Gobierno de Aragón 2009-10

Methods of Math Physics

Lecture notes for a course on methods of mathematical physics.

Physics Information Skills

An introduction to high quality information resources and databases in Physics and related disciplines. Refers to resources of information and methods of searching them.

Physics video for AS/A Level Science & Art Competition

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AS/A Level Science & Art Competition: Particle Physics

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School of Physics and Astronomy Logo - Vector and Raster

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Variety in Chemistry Education / Physics Higher Education Conference 2016 abstract submission.

Abstract submission form. More information available on conference website.

Convergencia de vías de señalización en un modelo de apoptosis

La sepsis es un evento inflamatorio generalizado del organismo inducido por un daño causado generalmente por un agente infeccioso. El patógeno más frecuentemente asociado con esta entidad es el Staphylococcus aureus, responsable de la inducción de apoptosis en células endoteliales debida a la producción de ceramida. Se ha descrito el efecto protector de la proteína C activada (PCA) en sepsis y su relación con la disminución de la apoptosis de las células endoteliales. En este trabajo se analizó la activación de las quinasas AKT, ASK1, SAPK/JNK y p38 en un modelo de apoptosis endotelial usando las técnicas de Western Blotting y ELISA. Las células endoteliales (EA.hy926), se trataron con C2-ceramida (130μM) en presencia de inhibidores químicos de cada una de estas quinasas y PCA. La supervivencia de las células en presencia de inhibidores químicos y PCA fue evaluada por medio de ensayos de activación de las caspasas 3, 7 y 9, que verificaban la muerte celular por apoptosis. Los resultados evidencian que la ceramida reduce la activación de AKT y aumenta la activación de las quinasas ASK, SAPK/JNK y p38, en tanto que PCA ejerce el efecto contrario. Adicionalmente se encontró que la tiorredoxina incrementa la activación/fosforilación de AKT, mientras que la quinasa p38 induce la defosforilación de AKT.

Salters Horners Advanced Physics Project : un proyecto contextualizado para la enseñanza de la física.

resumen literal de la revista