A luminescent gold complex: bis-μ-[bis(dicyclohexylphosphino)ethane-P,P']-digold bis(hexafluorophosphate)

[Au_2(C_(26)H_(48)P_2h](PF_6)_2, M_r = 1529·1, tetragonal, P4n2, ɑ= 15·917 (5), c = 12-448 (1) A, V = 3154 (1) A3 , Z = 2, Dx = 1·61 g cm^(-3), λ(Mo Ka) = 0·71073 A, μ = 50·1 cm^(-1), F(000) = 1528, room temperature (297 K), R = 0·064 for 3525 reflections with F/_o^2 > 0,0·038 for 2440 with F/_o^2 > 3σ(F/_o^2). This [Au_2(C_26)H_(48)P_2)_2] (PF_6)_2 compound shows a strong luminescence in the solid state at 77 K. The cation consists of two Au atoms joined by two bis (dicyclohexylphosphino )ethane links, with one Au atom and one half of a link being the asymmetric unit. The Au-Au distance [2·936 (1) Å] is only slightly longer than the 2·884 Å found in gold metal, indicative of substantial metal-metal bonding

Effect of spin-orbit coupling on the actinide dioxides AnO2 (An=Th, Pa, U, Np, Pu, and Am): A screened hybrid density functional study

We present a systematic comparison of the lattice structures, electronic density of states, and band gaps of actinide dioxides, AnO2 (An=Th, Pa, U, Np, Pu, and Am) predicted by the Heyd-Scuseria-Ernzerhof screened hybrid density functional (HSE) with the self-consistent inclusion of spin-orbit coupling (SOC). The computed HSE lattice constants and band gaps of AnO2 are in consistently good agreement with the available experimental data across the series, and differ little from earlier HSE results without SOC. ThO2 is a simple band insulator (f 0), while PaO2, UO2, and NpO2 are predicted to be Mott insulators. The remainders (PuO2 and AmO2) show considerable O2p/An5f mixing and are classified as charge-transfer insulators. We also compare our results for UO2, NpO2, and PuO2 with the PBE+U, self interaction correction (SIC), and dynamic mean-field theory (DMFT) many-body approximations

A luminescent gold complex: bis-μ-[bis(dicyclohexylphosphino)ethane-P,P']-digold bis(hexafluorophosphate)

[Au_2(C_(26)H_(48)P_2h](PF_6)_2, M_r = 1529·1, tetragonal, P4n2, ɑ= 15·917 (5), c = 12-448 (1) A, V = 3154 (1) A3 , Z = 2, Dx = 1·61 g cm^(-3), λ(Mo Ka) = 0·71073 A, μ = 50·1 cm^(-1), F(000) = 1528, room temperature (297 K), R = 0·064 for 3525 reflections with F/_o^2 > 0,0·038 for 2440 with F/_o^2 > 3σ(F/_o^2). This [Au_2(C_26)H_(48)P_2)_2] (PF_6)_2 compound shows a strong luminescence in the solid state at 77 K. The cation consists of two Au atoms joined by two bis (dicyclohexylphosphino )ethane links, with one Au atom and one half of a link being the asymmetric unit. The Au-Au distance [2·936 (1) Å] is only slightly longer than the 2·884 Å found in gold metal, indicative of substantial metal-metal bonding

Beta-delayed proton decay of proton-rich nuclei 23Al and 31Cl and explosive H-burning in classical novae

We have developed a technique to measure beta-delayed proton decay of proton-rich nuclei produced and separated with the MARS recoil spectrometer of Texas A&M University. The short-lived radioactive species are produced in-flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. The beam is pulsed and beta-p decay of the pure sources collected in beam is measured between beam pulses. Implantation avoids the problems with detector windows and allows us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. Using this technique, we have studied the isotopes 23Al and 31Cl, both important for understanding explosive H-burning in novae. They were produced in the reactions 24Mg(p,2n)23Al and 32S(p,2n)31Cl, respectively, in inverse kinematics, from stable beams at 48 and 40 MeV/u, respectively. We give details about the technique, its performances and the results for 23Al and 31Cl beta-p decay. The technique has shown a remarkable selectivity to beta-delayed charged-particle emission and would work even at radioactive beam rates of a few pps. The states populated are resonances for the radiative proton capture reactions 22Na(p,g)23Mg and 30P(p,g)31S, respectively.Comment: Submitted on Oct. 6, 2008 for the Proceedings of the 10th Symposium on Nuclei in the Cosmos Mackinac Island, Michigan, USA 27 July - 1 August, 2008 Acceptance pendin

Experimental study of beta-delayed proton decay of (23)Al for nucleosynthesis in novae

Journals published by the American Physical Society can be found at http://publish.aps.org/The beta-delayed gamma and proton decay of (23)Al has been studied with an alternative detector setup at the focal plane of the momentum achromat recoil separator MARS at Texas AandM University. We could detect protons down to an energy of 200 keV and determine the corresponding branching ratios. Contrary to results of previous beta-decay studies, no strong proton intensity from the decay of the isobaric analog state (IAS) of the (23)Al ground state at E(x) = 7803 keV in (23)Mg was observed. Instead we assign the observed low-energy group E(p,c.m.) = 206 keV to the decay from a state that is 16 keV below the IAS. We measured both proton and gamma branches from the decay of this state at E(x) = 7787 keV in (23)Mg, which is a very rare case in the literature. Combining our data with its measured lifetime, we determine its resonance strength to be omega gamma = 1.4(-0.4)(+0.5) meV. The value is in agreement with older direct measurements, but disagrees with a recent direct measurement. This state is the most important resonance for the radiative proton capture (22)Na(p, gamma)(23)Mg in some astrophysical environments, such as novae

Exploring the spin states of 90

The 90Zr nucleus was produced by three different reactions: 90Zr(p,p’), 91Zr(p,d), and 92Zr(p,t), and the spin-parity (Jπ) population of the 90Zr states produced by these reactions was studied to investigate the surrogate reaction approach, which aims at indirectly determining cross sections for compound-nuclear reactions involving unstable targets such as 89Zr(n,γ). Discrete γ-rays, associated with the de-excitation of 90Zr and 89Zr, were measured in coincidence with light ions at 90Zr excitation energies extending above the neutron separation energy. Low-lying states populated by (p,d) and (p,t) reactions agreed well with the previous measurements. The measured γ transition systematics were used to gain insights into the Jπ distribution of 90Zr around the neutron separation energy and it was found that the (p,p’) reaction preferentially produces lower J states than (p,d) and (p,t) reactions in the studied energy region

Fluid Mechanics in Dentinal Microtubules Provides Mechanistic Insights into the Difference between Hot and Cold Dental Pain

Dental thermal pain is a significant health problem in daily life and dentistry. There is a long-standing question regarding the phenomenon that cold stimulation evokes sharper and more shooting pain sensations than hot stimulation. This phenomenon, however, outlives the well-known hydrodynamic theory used to explain dental thermal pain mechanism. Here, we present a mathematical model based on the hypothesis that hot or cold stimulation-induced different directions of dentinal fluid flow and the corresponding odontoblast movements in dentinal microtubules contribute to different dental pain responses. We coupled a computational fluid dynamics model, describing the fluid mechanics in dentinal microtubules, with a modified Hodgkin-Huxley model, describing the discharge behavior of intradental neuron. The simulated results agreed well with existing experimental measurements. We thence demonstrated theoretically that intradental mechano-sensitive nociceptors are not “equally sensitive” to inward (into the pulp) and outward (away from the pulp) fluid flows, providing mechanistic insights into the difference between hot and cold dental pain. The model developed here could enable better diagnosis in endodontics which requires an understanding of pulpal histology, neurology and physiology, as well as their dynamic response to the thermal stimulation used in dental practices