Photoelectron spectra of anionic sodium clusters from time-dependent density-functional theory in real-time

We calculate the excitation energies of small neutral sodium clusters in the framework of time-dependent density-functional theory. In the presented calculations, we extract these energies from the power spectra of the dipole and quadrupole signals that result from a real-time and real-space propagation. For comparison with measured photoelectron spectra, we use the ionic configurations of the corresponding single-charged anions. Our calculations clearly improve on earlier results for photoelectron spectra obtained from static Kohn-Sham eigenvalues

Consideration of space applications transfer centers for the NASA office of applications

The concept of Space Applications Transfer Centers is examined to consider the design of the first of these facilities. The questions to be considered are listed

Nucleation threshold and deactivation mechanisms of nanoscopic cavitation nuclei

The acoustic nucleation threshold for bubbles trapped in cavities has theoretically been predicted within the crevice theory by Atchley and Prosperetti [“The crevice model of bubble nucleation,” J. Acoust. Soc. Am. 86, 1065 (1989)]. Here, we determine this threshold experimentally, by applying\ud a single pressure pulse to bubbles trapped in cylindrical nanoscopic pits (“artificial crevices”) with radii down to 50 nm. By decreasing the minimum pressure stepwise, we observe the threshold for which the bubbles start to nucleate. The experimental results are quantitatively in good agreement with the theoretical predictions of Atchley and Prosperetti. In addition, we provide the mechanism which explains the deactivation of cavitation nuclei: gas diffusion together with an aspherical bubble collapse. Finally, we present superhydrophobic nuclei which cannot be deactivated, unless with a high-speed liquid jet directed into the pit

Hyperglycemia and Hyperlipidemia Act Synergistically to Induce Renal Disease in LDL Receptor-Deficient BALB Mice

Diabetic nephropathy is the leading cause of end-stage renal disease in Western countries, but only a portion of diabetic patients develop diabetic nephropathy. Dyslipidemia represents an important aspect of the metabolic imbalance in diabetic patients. In this study, we addressed the impact of combined hyperlipidemia and hyperglycemia on renal pathology. Kidneys from wildtype (WT) or LDL receptor-deficient BALB/cBy mice (BALB. LDLR -/-) were examined at 22 weeks of age. Diabetes was induced by administration of streptozotocin and mice were randomly assigned to either standard chow or Western diet. Chow fed BALB. LDLR -/- mice did not demonstrate renal abnormalities, whereas BALB. LDLR -/- mice fed a Western diet showed occasional glomerular and tubulointerstitial foam cells. Diabetic WT mice had modestly increased glomerular cellularity and extracellular matrix. Hyperlipidemic and diabetic BALB. LDLR -/- mice exhibited an increase in glomerular cellularity and extracellular matrix, accumulation of glomerular and tubulointerstitial foam cells and mesangial lipid deposits. The tubular epithelium demonstrated pronounced lipid induced tubular degeneration with increased tubular epithelial cell turnover. Hyperlipidemia and hyperglycemia seem to act synergistically in inducing renal injury in the BALB. LDLR-/- mouse. This model of diabetic nephropathy is unique in its development of tubular lesions and may represent a good model for hyperlipidemia-exacerbated diabetic nephropathy. Copyright (C) 2004 S. Karger AG, Basel

Violation of the `Zero-Force Theorem' in the time-dependent Krieger-Li-Iafrate approximation

We demonstrate that the time-dependent Krieger-Li-Iafrate approximation in combination with the exchange-only functional violates the `Zero-Force Theorem'. By analyzing the time-dependent dipole moment of Na5 and Na9+, we furthermore show that this can lead to an unphysical self-excitation of the system depending on the system properties and the excitation strength. Analytical aspects, especially the connection between the `Zero-Force Theorem' and the `Generalized-Translation Invariance' of the potential, are discussed.Comment: 5 pages, 4 figure

Benthic Foraminiferal response to sea level change in the mixed siliciclastic-carbonate system of southern Ashmore Trough (Gulf of Papua)

Ashmore Trough in the western Gulf of Papua (GoP) represents an outstanding modern example of a tropical mixed siliciclastic-carbonate depositional system where significant masses of both river-borne silicates and bank-derived neritic carbonates accumulate. In this study, we examine how benthic foraminiferal populations within Ashmore Trough vary in response to sea level–driven paleoenvironmental changes, particularly organic matter and sediment supply. Two 11.3-m-long piston cores and a trigger core were collected from the slope of Ashmore Trough and dated using radiocarbon and oxygen isotope measurements of planktic foraminifera. Relative abundances, principal component analyses, and cluster analyses of benthic foraminiferal assemblages in sediment samples identify three distinct assemblages whose proportions changed over time. Assemblage 1, with high abundances of Uvigerina peregrina and Bolivina robusta, dominated between ∼83 and 70 ka (early regression); assemblage 2, with high abundances of Globocassidulina subglobosa, dominated between ∼70 and 11 ka (late regression through lowstand and early transgression); and assemblage 3, with high abundances of neritic benthic species such as Planorbulina mediterranensis, dominated from ∼11 ka to the present (late transgression through early highstand). Assemblage 1 represents heightened organic carbon flux or lowered bottom water oxygen concentration, and corresponds to a time of maximum siliciclastic fluxes to the slope with falling sea level. Assemblage 2 reflects lowered organic carbon flux or elevated bottom water oxygen concentration, and corresponds to an interval of lowered siliciclastic fluxes to the slope due to sediment bypass during sea level lowstand. Assemblage 3 signals increased off-shelf delivery of neritic carbonates, likely when carbonate productivity on the outer shelf (Great Barrier Reef) increased significantly when it was reflooded. Benthic foraminiferal assemblages in the sediment sink (slopes of Ashmore Trough) likely respond to the amount and type of sediment supplied from the proximal source (outer GoP shelf)

QCD Tests of the Puzzling Scalar Mesons

Motivated by several recent data, we test the QCD spectral sum rules (QSSR) predictions based on different proposals (\bar qq, \bar q\bar q qq, and gluonium) for the nature of scalar mesons. In the I=1 and 1/2 channels, the unusual (wrong) splitting between the a_0(980) and \kappa(900) and the a_0(980) width can be understood from QSSR within a \bar qq assignement. However, none of the \bar qq and \bar q\bar q qq results can explain the large \kappa width, which may suggest that it can result from a strong interference with non-resonant backgrounds. In the I=0 channel, QSSR and some low-energy theorems (LET) require the existence of a low mass gluonium \sigma_B(1 GeV) coupled strongly to Goldstone boson pairs which plays in the U(1)_V channel, a similar role than the \eta' for the value of the U(1)_A topological charge. The observed \sigma(600) and f_0(980) mesons result from a maximal mixing between the gluonium \sigma_B and \bar qq(1 GeV) mesons, a mixing scheme which passes several experimental tests. OZI violating J/\psi--> \phi\pi^+\pi^-, D_s--> 3\pi decays and J/\psi--> \gamma S glueball filter processes may indicate that most of the I=0 mesons above 1 GeV have important gluonium in their wave functions. We expect that the f_0(1500), f_0(1710) and f_0(1790) have significant gluonium component in their wave functions, while the f_0(1370) is mostly \bar qq. Tests of these results can be provided by the measurements of the pure gluonium \eta'\eta and 4\pi specific U(1)_A decay channels.Comment: Version to appear in Phys. Rev. D (one previous figure corrupted

Relativistic and retardation effects in the two--photon ionization of hydrogen--like ions

The non-resonant two-photon ionization of hydrogen-like ions is studied in second-order perturbation theory, based on the Dirac equation. To carry out the summation over the complete Coulomb spectrum, a Green function approach has been applied to the computation of the ionization cross sections. Exact second-order relativistic cross sections are compared with data as obtained from a relativistic long-wavelength approximation as well as from the scaling of non-relativistic results. For high-Z ions, the relativistic wavefunction contraction may lower the two-photon ionization cross sections by a factor of two or more, while retardation effects appear less pronounced but still give rise to non-negligible contributions.Comment: 6 pages, 2 figure