Beyond Ehrenfest: correlated non-adiabatic molecular dynamics

A method for introducing correlations between electrons and ions that is computationally affordable is described. The central assumption is that the ionic wavefunctions are narrow, which makes possible a moment expansion for the full density matrix. To make the problem tractable we reduce the remaining many-electron problem to a single-electron problem by performing a trace over all electronic degrees of freedom except one. This introduces both one- and two-electron quantities into the equations of motion. Quantities depending on more than one electron are removed by making a Hartree-Fock approximation. Using the first-moment approximation, we perform a number of tight binding simulations of the effect of an electric current on a mobile atom. The classical contribution to the ionic kinetic energy exhibits cooling and is independent of the bias. The quantum contribution exhibits strong heating, with the heating rate proportional to the bias. However, increased scattering of electrons with increasing ionic kinetic energy is not observed. This effect requires the introduction of the second moment.

Abell 41: shaping of a planetary nebula by a binary central star

ABSTRACT We present the first detailed spatiokinematical analysis and modelling of the planetary nebula Abell 41, which is known to contain the well-studied close-binary system MT Ser. This object represents an important test case in the study of the evolution of planetary nebulae with binary central stars as current evolutionary theories predict that the binary plane should be aligned perpendicular to the symmetry axis of the nebula. Deep narrow-band imaging in the light of [NII]6584Å, [OIII]5007 Å and [SII]6717+6731Å, obtained using ACAM on the William Herschel Telescope, has been used to investigate the ionization structure of Abell 41. Long-slit observations of the Ha and [NII]6584Å emission were obtained using the Manchester Echelle Spectrometer on the 2.1-m San Pedro Mártir Telescope. These spectra, combined with the narrow-band imagery, were used to develop a spatiokinematical model of [NII]6584Å emission from Abell 41. The best-fitting model reveals Abell 41 to have a waisted, bipolar structure with an expansion velocity of ~40 km s-1 at the waist. The symmetry axis of the model nebula is within 5° of perpendicular to the orbital plane of the central binary system. This provides strong evidence that the close-binary system, MT Ser, has directly affected the shaping of its nebula, Abell 41. Although the theoretical link between bipolar planetary nebulae and binary central stars is long established, this nebula is only the second to have this link, between nebular symmetry axis and binary plane, proved observationally.

Urotensin II in the central nervous system of the frog Rana ridibunda: Immunohistochemical localization and biochemical characterization

Urotensin II (UII) is traditionally regarded as a product of the neurosecretory cells in the caudal portion of the spinal cord of jawed fishes. A peptide related to UII has been recently isolated from the frog brain, thereby providing the first evidence that UII is also present in the central nervous system of a tetrapod. In the present study, we have investigated the distribution of UII-immunoreactive elements in the brain and spinal cord of the frog Rana ridibunda by immunofluorescence using an antiserum directed against the conserved cyclic region of the peptide. Two distinct populations of UII-immunoreactive perikarya were visualized. The first group of positive neurons was found in the nucleus hypoglossus of the medulla oblongata, which controls two striated muscles of the tongue. The second population of immunoreactive cell bodies was represented by a subset of motoneurons that were particularly abundant in the caudal region of the cord (34% of the motoneuron population). The telencephalon, diencephalon, mesencephalon, and metencephalon were totally devoid of UII-containing cell bodies but displayed dense networks of UII-immunoreactive fibers, notably in the thalamus, the tectum, the tegmentum, and the granular layer of the cerebellum. In addition, a dense bundle of long varicose processes projecting rostrocaudally was observed coursing along the ventral surface of the brain from the midtelencephalon to the medulla oblongata. Reversed-phase high-performance liquid chromatography analysis of frog brain, medulla oblongata, and spinal cord extracts revealed that, in all three regions, UII-immunoreactive material eluted as a single peak which exhibited the same retention time as synthetic frog UII. Taken together, these data indicate that UII, in addition to its neuroendocrine functions in fish, is a potential regulatory peptide in the central nervous system of amphibians. (C) 1996 Wiley-Liss, Inc.

Evaluation of an Older Persons’ Assessment Educational Workbook with second year nursing students in the UK.

Background: As a first step to successfully meet the complex health and social needs of older people, patient assessment has become a central feature of government policy and practice in order to ensure that care planning is person-centred. A core component of nurse education is clinical practice in order to support the development of clinical skills and competence; therefore it is important to help students and their practice-based mentors to develop and apply older person assessment skills. Therefore, an educational workbook was developed to help 2nd year nursing students to learn a structured, systematic and individualised older person assessment process with the support of their mentor.

Aim: A pilot study to evaluate the impact of an Older Persons’ Assessment Educational Workbook and explore second year nursing students’ competence and their opinions and use of an older person’s assessment skills workbook.

Research Methodology: A pre-experimental design (pre and post-test with no comparison group) was undertaken with n=6 2nd year students in 2014. The outcome measure was the Nursing Competence Questionnaire and results were analysed using the Wilcoxin Signed Rank Test in SPSS version 21. Content analysis of completed workbooks and a survey (n=5) of opinions regarding the workbook was undertaken.

Key Findings- No pre-post-test difference was found in the Nursing Competence Questionnaire with p=0.058 for the total scale. However, as this was a pilot, the study was under-powered and all students’ scores improved. Content analysis of the workbook found that 3 of the 5 participants completed all components of the workbook, with a mean of 1051 words used (Std dev 281.8). Through the survey students reported the workbook as a useful guide when undertaking a patient assessment.

Conclusions: The workbook showed potential as an intervention to help support development of nursing students’ assessment skills in practice.