Chlorophylls - natural solar cells

A molecular modeling study was conducted on a series of six natural occurring chlorophylls. Quantum chemistry calculated orbital energies were used to estimate frequency of transitions between occupied molecular orbital and unoccupied molecular orbital energy levels of chlorophyll molecules in vivo conditions in standard (ASTMG173) environmental conditions. Obtained results are in good agreement with energies necessary to fix the Magnesium atom by chlorophyll molecules and with occurrence of chlorophylls in living vegetal organisms.Comment: 6 pages, 1 figure, 4 tables; paper in proceeding

Strain enhanced superconductivity of MoX2X_2 (XX=S or Se) bilayers with Na intercalation

Mo$X_2$ ($X$=S or Se) is a semiconductor family with two-dimensional structure. And a recent calculation predicted the superconductivity in electron doped MoS$_2$ monolayer. In this work, the electronic structure and lattice dynamics of Mo$X_2$ bilayers with monolayer Na intercalated, have been calculated. According to the electron-phonon interaction, it is predicted that these bilayers can be transformed from indirect-gap semiconductors to a superconductors by Na intercalation. More interestingly, the biaxial tensile strain can significantly enhance the superconducting temperature up to $\sim10$ K in Na-intercalated MoS$_2$. In addition, the phonon mean free path at room-temperature is also greatly improved in Na intercalated MoSe$_2$, which is advantaged for related applications.Comment: 6 pages, 5 figure

Psychological aspects of information seeking on the Internet

Two studies are presented that investigate information seeking behaviour on the Internet. In Study One, soccer fans’ information seeking on the World Wide Web (WWW) is investigated. In Study Two, access rates to a cancer information website are analysed. It is tentatively argued that there is a tendency for people to access information more commonly avoided in ‘real life’, although in the case of football fans, the tendency to ‘bask in reflected glory’ remains when online, while cutting off reflected failure is minimised. Implications for understanding and researching psychological processes of web browsing behaviour are discussed

Lattice dynamics and electronic structure of energetic solids LiN3 and NaN3: A first principles study

We report density functional theory calculations on the crystal structure, elastic, lattice dynamics and electronic properties of iso-structural layered monoclinic alkali azides, LiN3 and NaN3. The effect of van der Waals interactions on the ground- state structural properties is studied by using various dispersion corrected density functionals. Based on the equilibrium crystal structure, the elastic constants, phonon dispersion and phonon density of states of the compounds are calculated. The accurate energy band gaps are obtained by using the recently developed Tran Blaha-modified Becke Johnson (TB-mBJ) functional and found that both the azides are direct band gap insulators

New Bounds for the Joint Replenishment Problem: Tighter, but not always better

In this paper we present new bounds on the basic cycle time for optimal methods to solve the JRP. They are tighter than the ones reported in Viswanathan [7]. We carry out extensive numerical experiments to compare them and to investigate the computational complexity.computational complexity;joint replenishment problem;bounds

First-principles investigation of organic photovoltaic materials C60_{60}, C70_{70}, [C60_{60}]PCBM, and bis-[C60_{60}]PCBM using a many-body G0W0G_0W_0-Lanczos approach

We present a first-principles investigation of the excited-state properties of electron acceptors in organic photovoltaics including C$_{60}$, C$_{70}$, [6,6]-phenyl-C$_{61}$-butyric-acid-methyl-ester ([C$_{60}$]PCBM), and bis-[C$_{60}$]PCBM using many-body perturbation theory within the Hedin's $G_0W_0$ approximation and an efficient Lanczos approach. Calculated vertical ionization potentials (VIP) and vertical electron affinities (VEA) of C$_{60}$ and C$_{70}$ agree very well with experimental values measured in gas phase. The density of states of all three molecules is also compared to photoemission and inverse photoemission spectra measured on thin-films, exhibiting a close agreement - a rigid energy-gap renormalization owing to intermolecular interactions in the thin-films. In addition, it is shown that the low-lying unoccupied states of [C$_{60}$]PCBM are all derived from the highest-occupied molecular orbitals and the lowest-unoccupied molecular orbitals of fullerene C$_{60}$. The functional side group in [C$_{60}$]PCBM introduces a slight electron transfer to the fullerene cage, resulting in small decreases of both VIP and VEA. This small change of VEA provides a solid justification for the increase of open-circuit voltage when replacing fullerene C$_{60}$ with [C$_{60}$]PCBM as the electron acceptor in bulk heterojunction polymer solar cells.Comment: 9 pages, 4 figures, and 7 table

Coexistence of 'alpha+ 208Pb' cluster structures and single-particle excitations in 212Po

Excited states in 212Po have been populated by alpha transfer using the 208Pb(18O,14C) reaction at 85MeV beam energy and studied with the EUROBALL IV gamma multidetector array. The level scheme has been extended up to ~ 3.2 MeV excitation energy from the triple gamma coincidence data. Spin and parity values of most of the observed states have been assigned from the gamma angular distributions and gamma -gamma angular correlations. Several gamma lines with E(gamma) < 1 MeV have been found to be shifted by the Doppler effect, allowing for the measurements of the associated lifetimes by the DSAM method. The values, found in the range [0.1-0.6] ps, lead to very enhanced E1 transitions. All the emitting states, which have non-natural parity values, are discussed in terms of alpha-208Pb structure. They are in the same excitation-energy range as the states issued from shell-model configurations.Comment: 21 pages, 19 figures, corrected typos, revised arguments in Sect. III