Accurate long-range coefficients for two excited like isotope He atoms: He(21P2 ^1P)--He(21P2 ^1P), He(21P2 ^1P)--He(23P2 ^3P), and He(23P2 ^3P)--He(23P2 ^3P)

A general formalism is used to express the long-range potential energies in inverse powers of the separation distance between two like atomic or molecular systems with $P$ symmetries. The long-range molecular interaction coefficients are calculated for the molecular symmetries $\Delta$, $\Pi$, and $\Sigma$, arising from the following interactions: He($2 ^1P$)--He($2 ^1P$), He($2 ^1P$)--He($2 ^3P$), and He($2 ^3P$)--He($2 ^3P$). The electric quadrupole-quadrupole term, $C_{5}$, the van der Waals (dispersion) term $C_{6}$, and higher-order terms, $C_{8}$, and $C_{10}$, are calculated \textit{ab initio} using accurate variational wave functions in Hylleraas coordinates with finite nuclear mass effects. A comparison is made with previously published results where available

Skeleton Cave, Leigh Woods, Bristol

An account is given of the discovery and excavation of this small cave in the 1960s. It is recorded that archaeological finds were made, but of these, only a single human mandible can now be traced. Radiocarbon dating shows the specimen to be early Neolithic in age; a metrical analysis was less conclusive.http://www.ubss.org.uk/resources/proceedings/vol27/UBSS_Proc_27_2_197-209.pd

Functional and anatomic correlates of two frequently observed temporal lobe seizure-onset patterns.

Intracranial depth electrode EEG records of 478 seizures, recorded in 68 patients undergoing diagnostic monitoring with depth electrodes, were evaluated to investigate the correlates of electrographic onset patterns in patients with temporal lobe seizures. The seizure onsets in 78% of these patients were identified as either hypersynchronous onsets, beginning with low-frequency, high-amplitude spikes, or low-voltage fast (LVF) onsets, increasing in amplitude as the seizure progressed. The number of patients (35) having hypersynchronous seizure onsets was nearly twice that of patients (18) having LVF onsets. Three major differences were seen among patients with the two seizure-onset patterns. When compared with patients having LVF onsets, patients with hypersynchronous seizure onsets had a significantly greater probability of having (1) focal rather than regional seizure onsets (p < 0.01), (2) seizures spreading more slowly to the contralateral mesial temporal lobe (p < 0.003), and (3) cell counts in resected hippocampal tissue showing greater neuronal loss (p < 0.001). The results provide evidence that the most frequent electrographic abnormality associated with mesial temporal seizures is local hypersynchrony, a condition associated with major neuronal loss in the hippocampus. The results also indicate that LVF seizure onsets more frequently represent widely distributed discharges, which interact with and spread more rapidly to surrounding neocortical areas

Theory and simulation of spectral line broadening by exoplanetary atmospheric haze

Atmospheric haze is the leading candidate for the flattening of expolanetary spectra, as it's also an important source of opacity in the atmospheres of solar system planets, satellites, and comets. Exoplanetary transmission spectra, which carry information about how the planetary atmospheres become opaque to stellar light in transit, show broad featureless absorption in the region of wavelengths corresponding to spectral lines of sodium, potassium and water. We develop a detailed atomistic model, describing interactions of atomic or molecular radiators with dust and atmospheric haze particulates. This model incorporates a realistic structure of haze particulates from small nano-size seed particles up to sub-micron irregularly shaped aggregates, accounting for both pairwise collisions between the radiator and haze perturbers, and quasi-static mean field shift of levels in haze environments. This formalism can explain large flattening of absorption and emission spectra in haze atmospheres and shows how the radiator - haze particle interaction affects the absorption spectral shape in the wings of spectral lines and near their centers. The theory can account for nearly all realistic structure, size and chemical composition of haze particulates and predict their influence on absorption and emission spectra in hazy environments. We illustrate the utility of the method by computing shift and broadening of the emission spectra of the sodium D line in an argon haze. The simplicity, elegance and generality of the proposed model should make it amenable to a broad community of users in astrophysics and chemistry.Comment: 16 pages, 4 figures, submitted to MNRA

Long-range interactions between a He(23S2 ^3S) atom and a He(23P2 ^3P) atom for like isotopes

For the interactions between a He($2 ^3S$) atom and a He($2 ^3P$) atom for like isotopes, we report perturbation theoretic calculations using accurate variational wave functions in Hylleraas coordinates of the coefficients determining the potential energies at large internuclear separations. We evaluate the coefficient $C_{3}$ of the first order resonant dipole-dipole energy and the van der Waals coefficients $C_{6}$, $C_{8}$, and $C_{10}$ for the second order energies arising from the mutual perturbations of instantaneous electric dipole, quadrupole, and octupole interactions. We also evaluate the coefficient $C_{9}$ of the leading contribution to the third order energy. We establish definitive values including treatment of the finite nuclear mass for the ${}^3$He($2 ^3S$)--${}^3$He($2 ^3P$) and ${}^4$He($2 ^3S$)--${}^4$He($2 ^3P$) interactions.Comment: This article has been accepted by Physical Review

Ultracold collisions of metastable helium atoms

We report scattering lengths for the singlet Sigma g +, triplet Sigma u + and quintet Sigma g + adiabatic molecular potentials relevant to collisions of two metastable (n=2 triplet S) helium atoms as a function of the uncertainty in these potentials. These scattering lengths are used to calculate experimentally observable scattering lengths, elastic cross sections and inelastic rates for any combination of states of the colliding atoms, at temperatures where the Wigner threshold approximation is valid.Comment: 20 pages, 8 figures, RevTeX, epsf. Small additions of tex