A first principles simulation of rigid water

We present the results of Car-Parrinello (CP) simulations of water at ambient conditions and under pressure, using a rigid molecule approximation. Throughout our calculations, water molecules were maintained at a fixed intramolecular geometry corresponding to the average structure obtained in fully unconstrained simulations. This allows us to use larger time steps than those adopted in ordinary CP simulations of water, and thus to access longer time scales. In the absence of chemical reactions or dissociation effects, these calculations open the way to ab initio simulations of aqueous solutions that require timescales substantially longer than presently feasible (e.g. simulations of hydrophobic solvation). Our results show that structural properties and diffusion coefficients obtained with a rigid model are in better agreement with experiment than those determined with fully flexible simulations. Possible reasons responsible for this improved agreement are discussed

Learning spatial orientation tasks in the radial-maze and structural variation in the hippocampus in inbred mice

In the present paper we review a series of experiments showing that heritable variations in the size of the hippocampal intra- and infrapyramidal mossy fiber (IIPMF) terminal fields correlate with performance in spatial, but not non-spatial radial-maze tasks. Experimental manipulation of the size of this projection by means of early postnatal hyperthyroidism produces the effects predicted from the correlations obtained with inbred mouse strains. Although the physiological mechanisms behind these correlations are unknown as yet, several lines of evidence indicate that these correlations are causal

Phase separation in hydrogen-helium mixtures at Mbar pressures

The properties of hydrogen-helium mixtures at Mbar pressures and intermediate temperatures (4000 to 10000 K) are calculated with first-principles molecular dynamics simulations. We determine the equation of state as a function of density, temperature, and composition and, using thermodynamic integration, we estimate the Gibbs free energy of mixing, thereby determining the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen. These results are directly relevant to models of the interior structure and evolution of Jovian planets. We find that the temperatures for the demixing of helium and hydrogen are sufficiently high to cross the planetary adiabat of Saturn at pressures around 5 Mbar; helium is partially miscible throughout a significant portion of the interior of Saturn, and to a lesser extent in Jupiter.Comment: 6 pages, 7 figures. Published in "Proceedings of the National Academy of Sciences USA

Electronic structure of aqueous solutions: Bridging the gap between theory and experiments

Predicting the electronic properties of aqueous liquids has been a long-standing challenge for quantum mechanical methods. However, it is a crucial step in understanding and predicting the key role played by aqueous solutions and electrolytes in a wide variety of emerging energy and environmental technologies, including battery and photoelectrochemical cell design. We propose an efficient and accurate approach to predict the electronic properties of aqueous solutions, on the basis of the combination of first-principles methods and experimental validation using state-of-the-art spectroscopic measurements. We present results of the photoelectron spectra of a broad range of solvated ions, showing that first-principles molecular dynamics simulations and electronic structure calculations using dielectric hybrid functionals provide a quantitative description of the electronic properties of the solvent and solutes, including excitation energies. The proposed computational framework is general and applicable to other liquids, thereby offering great promise in understanding and engineering solutions and liquid electrolytes for a variety of important energy technologies

Facilitators and Barriers to Sustainable Employment After Spinal Cord Injury or Acquired Brain Injury: The Person's Perspective

BackgroundSustaining employment after initial return to work represents a major challenge for people with a disability. While individuals with spinal cord injury (SCI) and acquired brain injury (ABI) make a prime example for this challenge, their view on factors supporting and hindering sustainable employment have rarely been investigated in depth so far.PurposeTo examine facilitators and barriers to sustainable employment, as perceived by persons with SCI or ABI.MethodsFourteen focus groups and four individual interviews were conducted and thematically analyzed.ResultsPerceived facilitators and barriers to sustainable employment reflected the three biopsychosocial areas of personal, impairment-related and environmental factors. For both condition groups, key facilitators included environmental factors (i.e., aspects of the work organization, the workplace, supportive private and work environment) and personal factors (i.e., the ability to self-advocate, to communicate and to learn how to live with one's own disability). Major barriers comprised injury-related impairments, including decreased mobility and pain for people with SCI and fatigue and limited cognitive resources for persons with ABI, as well as environmental factors related to insurance procedures and the social security system for both conditions.ConclusionsThe biopsychosocial factors identified in our study as well as their interplay should receive particular attention to optimally support sustainable employment in vocational integration and work retention practice. Interventions should particularly focus on the empowerment of those affected as well as on the creation of supportive work environments that match their abilities and needs

Calcium urinary excretion in dairy cows with different levels of glucose tolerance.

O objetivo deste estudo foi avaliar a excreção urinária de Ca durante o periparto em vacas leiteiras com diferentes níveis de tolerância à glicose durante o período de pré-parto

Resumption of postpartum ovarian cyclicity in dairy cows and its relationship with acute phase proteins, uterine health and lipolysis during the transition period.

O objetivo deste estudo foi avaliar a retomada do pós-parto ciclicidade e sua relação com proteínas de fase aguda, a saúde uterina e lipólise durante o período de transição de vacas leiteiras