Role of Self-Interaction Effects in the Geometry Optimization of Small Metal Clusters

By combining the Self-Interaction Correction (SIC) with pseudopotential perturbation theory, the role of self-interaction errors inherent to the Local Density Approximation (LDA) to Density Functional Theory is estimated in the determination of ground state and low energy isomeric structures of small metallic clusters. Its application to neutral sodium clusters with 8 and 20 atoms shows that the SIC provides sizeable effects in Na_8, leading to a different ordering of the low lying isomeric states compared with ab-initio LDA predictions, whereas for Na_20, the SIC effects are less pronounced, such that a quantitative agreement is achieved between the present method and ab-initio LDA calculations.Comment: RevTeX, 4 pages, 1 figure available from [email protected]

Ab initio simulations of liquid systems: Concentration dependence of the electric conductivity of NaSn alloys

Liquid NaSn alloys in five different compositions (20, 40, 50, 57 and 80% sodium) are studied using density functional calculations combined with molecular dynamics(Car-Parrinello method). The frequency-dependent electric conductivities for the systems are calculated by means of the Kubo-Greenwood formula. The extrapolated DC conductivities are in good agreement with the experimental data and reproduce the strong variation with the concentration. The maximum of conductivity is obtained, in agreement with experiment, near the equimolar composition. The strong variation of conductivity, ranging from almost semiconducting up to metallic behaviour, can be understood by an analysis of the densities-of-states.Comment: LaTex 6 pages and 2 figures, to appear in J.Phys. Cond. Ma

Investigation of the influence of earthquakes on the water level in the geothermal reservoir of Waiwera (New Zealand)

The water level of the Waiwera geothermal reservoir is mainly governed by the production operations due to a commonly strong pumping signal. However, in the hours and days after the Kaikoura earthquake on 14 November 2016, it increased by more than 0.5&thinsp;m, indicating that seismic events can have an influence as well. In a continuous time series consisting of monthly means of water level data and pumping rates starting in 1986, we tried to determine if events above a certain strength alter groundwater dynamics at Waiwera in general. We applied an empirical equation and calculated the on-site seismic energy density from earthquake magnitudes and distances. All recorded earthquakes with a magnitude above 4 within a radius of about 1500&thinsp;km around New Zealand have been taken into account. A clear correlation cannot be proven but none of the recorded earthquakes led to such a high energy density in Waiwera as the Kaikoura event did. For the future, it is recommended to increase the resolution of the metred water production rates to daily averages to improve the detectability of water level changes following earthquakes.</p

Calculated lifetimes of hot electrons in aluminum and copper using a plane-wave basis set

We report about the lifetimes of hot electrons in crystalline aluminum and copper. For aluminum the results agree quantitatively with the experimental results. For copper we get good agreement for quasiparticle energies in the (110) direction above 2 eV which shows that the lifetimes for quasiparticle states above 2 eV are determined by sp bands, explaining the puzzling fact that simple Fermi liquid theory describes Cu in this direction quite well. The calculations were performed within the shielded interaction approximation using a plane-wave basis expansion for the wave functions. We show that for Cu this basis leads to equally good results as the more demanding linearized augmented plane-wave basis

Temporal and spatial variability of prehistoric aquatic resource procurement: a case study from Mesolithic Northern Iberia

Prehistoric shell middens hold valuable evidence of past human–environment interactions. In this study, we used carbon (δ13C) and oxygen (δ18O) stable isotopes of Mytilus galloprovincialis shells excavated from El Perro, La Fragua and La Chora, three Mesolithic middens in Cantabria, Northern Spain, to examine hunter-gatherer subsistence strategies in terms of seasonality and collection areas. Furthermore, we used shell δ18O to reconstruct water temperature during the early Holocene. Stable isotopes reveal a shellfish harvesting diversification trend represented by the gradual establishment of the upper estuaries as new procurement areas and an increase of harvesting mobility in both coastal and in-land sites. These innovations in subsistence strategies during the Mesolithic coincided with major changes in the surrounding environment as attested by the water temperature reconstructions based on δ18O and backed by several global and regional records. Overall, our results show that shell δ13C and δ18O stable isotopes have an underexplored potential as provenance proxies which stimulates their application to the archaeological record to further understand prehistoric human resource procurement and diet

Time-dependent screening of a positive charge distribution in metals: Excitons on an ultra-short time scale

Experiments determining the lifetime of excited electrons in crystalline copper reveal states which cannot be interpreted as Bloch states [S. Ogawa {\it et al.}, Phys. Rev. B {\bf 55}, 10869 (1997)]. In this article we propose a model which explains these states as transient excitonic states in metals. The physical background of transient excitons is the finite time a system needs to react to an external perturbation, in other words, the time which is needed to build up a polarization cloud. This process can be probed with modern ultra-short laser pulses. We calculate the time-dependent density-response function within the jellium model and for real Cu. From this knowledge it is possible within linear response theory to calculate the time needed to screen a positive charge distribution and -- on top of this -- to determine excitonic binding energies. Our results lead to the interpretation of the experimentally detected states as transient excitonic states.Comment: 24 pages, 9 figures, to appear in Phys. Rev. B, Nov. 15, 2000, issue 2

Gender Differences in Body Evaluation: Do Men Show More Self-Serving Double Standards Than Women?

Generally speaking, compared to women, men are less dissatisfied with their own body and consider themselves to be better-looking and less overweight. So far, however, it is unclear whether these divergent body ratings arise from the application of double standards. With the present study, we examined whether men apply different standards to their own body than to other men’s bodies and whether they differ from women in this regard. To this aim, we presented n = 104 women and n = 93 men with pictures of thin, average-weight, overweight, athletic and hypermuscular male and female bodies on a computer screen. To manipulate identification, we showed the bodies of the respective participant’s gender once with the participant’s own face and once with the face of another person. Identity cues, such as faces, might activate different body schemata, which influence body ratings and thus lead to the application of double standards. Participants were instructed to rate their emotional reaction to the bodies according to valence and arousal, and to rate the bodies with respect to attractiveness, body fat, and muscle mass. The application of double standards was determined by calculating the difference between the rating of a body presented with the participant’s face and the rating of the same body presented with another person’s face. Both women and men showed self-deprecating double standards in valence, body attractiveness, body fat and muscle mass for the overweight body. Men also revealed self-deprecating double standards for the thin, average-weight and hypermuscular bodies, but evaluated the athletic body as more attractive and with a higher positive feeling when it was presented with their own face. Women did not show any self-serving double standards and showed fewer self-deprecating double standards than men. The results indicate that men devalue non-ideal bodies and upvalue ideal bodies when they are self-related, whereas women more rate in a fair-minded manner. Thus, in contrast to women, an advantage for men may be that they are able to self-enhance in the case of desirable bodies. This ability to self-enhance regarding desirable features might be beneficial for men’s self-worth and body satisfaction

Life history, environment and extinction of the scallop Carolinapecten eboreus (Conrad) in the Plio-Pleistocene of the U.S. eastern seaboard.

Plio-Pleistocene mass extinction of marine bivalves on the U.S. eastern seaboard has been attributed to declines in temperature and primary production. We investigate the relationship of growth rate in the scallop Carolinapecten eboreus to variation in these parameters to determine which contributed to its extinction. We use ontogenetic profiles of shell d18O to estimate growth rate and seasonal temperature, microgrowth-increment data to validate d18O-based figures for growth rate, and shell d13C to supplement assemblage evidence of production. Postlarval growth started in the spring/summer in individuals from the Middle Atlantic Coastal Plain but in the autumn/winter in some from the Gulf Coastal Plain. Growth rate typically declined with age and was usually higher in summer than winter. Many individuals died in winter but the largest forms typically died in spring, possibly on spawning for the first time. No individuals lived longer than two years and some grew exceedingly fast overall, up to 60% more rapidly than any other scallop species (, 145.7 mm in a year). Faster growth was generally achieved by secreting more rather than larger microgrowth increments. Some very fast-growing individuals lived in settings of high production and low temperature. No individuals grew slowly under high production whereas most if not all grew slowly under ‘average’ production and low temperature. In that the rapid growth evidently enabled by high production would have afforded protection from predators, Plio-Pleistocene decline in production was probably contributory to the extinction of C. eboreus. However, the negative impact of low temperature on growth under ‘average’ production suggests that temperature decline played some part.British Geological Survey (BUFI S157), NERC Isotope Goscience Facilities (IP-1351-1112), University of Derby (Research-Inspired Curriculum Fund

Coralline alga reveals first marine record of subarctic North Pacific climate change

While recent changes in subarctic North Pacific climate had dramatic effects on ecosystems and fishery yields, past climate dynamics and teleconnection patterns are poorly understood due to the absence of century-long high-resolution marine records. We present the first 117-year long annually resolved marine climate history from the western Bering Sea/Aleutian Island region using information contained in the calcitic skeleton of the long-lived crustose coralline red alga Clathromorphum nereostratum, a previously unused climate archive. The skeletal δ18O-time series indicates significant warming and/or freshening of surface waters after the middle of the 20th century. Furthermore, the time series is spatiotemporally correlated with Pacific Decadal Oscillation (PDO) and tropical El Niño-Southern Oscillation (ENSO) indices. Even though the western Bering Sea/Aleutian Island region is believed to be outside the area of significant marine response to ENSO, we propose that an ENSO signal is transmitted via the Alaskan Stream from the Eastern North Pacific, a region of known ENSO teleconnections