Orientation-dependent binding energy of graphene on palladium

Using density functional theory calculations, we show that the binding strength of a graphene monolayer on Pd(111) can vary between physisorption and chemisorption depending on its orientation. By studying the interfacial charge transfer, we have identified a specific four-atom carbon cluster that is responsible for the local bonding of graphene to Pd(111). The areal density of such clusters varies with the in-plane orientation of graphene, causing the binding energy to change accordingly. Similar investigations can also apply to other metal substrates, and suggests that physical, chemical, and mechanical properties of graphene may be controlled by changing its orientation.Comment: 5 pages, 6 figure

Hydrogen molecule in a magnetic field: The lowest states of the Pi manifold and the global ground state of the parallel configuration

The electronic structure of the hydrogen molecule in a magnetic field is investigated for parallel internuclear and magnetic field axes. The lowest states of the $\Pi$ manifold are studied for spin singlet and triplet$(M_s = -1)$ as well as gerade and ungerade parity for a broad range of field strengths $0 \leq B \leq 100 a.u.$ For both states with gerade parity we observe a monotonous decrease in the dissociation energy with increasing field strength up to $B = 0.1 a.u.$ and metastable states with respect to the dissociation into two H atoms occur for a certain range of field strengths. For both states with ungerade parity we observe a strong increase in the dissociation energy with increasing field strength above some critical field strength $B_c$. As a major result we determine the transition field strengths for the crossings among the lowest $^1\Sigma_g$, $^3\Sigma_u$ and $^3\Pi_u$ states. The global ground state for $B \lesssim 0.18 a.u.$ is the strongly bound $^1\Sigma_g$ state. The crossings of the $^1\Sigma_g$ with the $^3\Sigma_u$ and $^3\Pi_u$ state occur at $B \approx 0.18$ and $B \approx0.39 a.u.$, respectively. The transition between the $^3\Sigma_u$ and $^3\Pi_u$ state occurs at $B \approx 12.3 a.u.$ Therefore, the global ground state of the hydrogen molecule for the parallel configuration is the unbound $^3\Sigma_u$ state for $0.18 \lesssim B \lesssim 12.3 a.u.$ The ground state for $B \gtrsim 12.3 a.u.$ is the strongly bound $^3\Pi_u$ state. This result is of great relevance to the chemistry in the atmospheres of magnetic white dwarfs and neutron stars.Comment: submitted to Physical Review

Mapping of the SDHA Locus to Bovine Chromosome 20

Source/description Primer sequences PCR and PCR-RFLP conditions Polymorphism Linkage analysis and chromosomal location Acknowledgements Reference

Implicit theories of emotion shape regulation of negative affect

Mental contrasting of a desired future with the present reality strengthens the link between expectations and goal pursuit: The higher expectations of success, the more people engage in goal pursuit; the lower expectations of success, the more people let go or disengage from goal pursuit. In three studies, we tested if mental contrasting increases the link between expectations and goal pursuit by affecting the strength of mental associations between future and reality. We used lexical decision tasks to measure the strength of associations between future and reality for different domains of goal pursuit (i.e., interpersonal relations, achievement), and compared results in the mental contrasting condition to relevant control conditions (i.e., reverse contrasting and content control). In the mental contrasting condition but not in the control conditions emerged a strong link between expectations of success and the strength of associations between future and reality (Study 1, 2). The strength of associations between future and reality in turn mediated the link between expectations and self-reported as well as other-rated goal pursuit in the mental contrasting condition (Study 1, 2). Finally, the link between expectations and the strength of associations between future and reality in the mental contrasting condition vanished when the goal was attained (Study 3). Taken together, these results suggest that strength of future–reality associations are a mechanism specific to mental contrasting effects on goal pursuit

Contacting single bundles of carbon nanotubes with alternating electric fields

Single bundles of carbon nanotubes have been selectively deposited from suspensions onto sub-micron electrodes with alternating electric fields. We explore the resulting contacts using several solvents and delineate the differences between Au and Ag as electrode materials. Alignment of the bundles between electrodes occurs at frequencies above 1 kHz. Control over the number of trapped bundles is achieved by choosing an electrode material which interacts strongly with the chemical functional groups of the carbon nanotubes, with superior contacts being formed with Ag electrodes.Comment: 4 pages, RevTe

Exchange and correlation energies of ground states of atoms and molecules in strong magnetic fields

Using a Hartree-Fock mesh method and a configuration interaction approach based on a generalized Gaussian basis set we investigate the behaviour of the exchange and correlation energies of small atoms and molecules, namely th e helium and lithium atom as well as the hydrogen molecule, in the presence of a magnetic field covering the regime B=0-100a.u. In general the importance of the exchange energy to the binding properties of at oms or molecules increases strongly with increasing field strength. This is due to the spin-flip transitions and in particular due to the contributions of the tightly bound hydrogenic state s which are involved in the corresponding ground states of different symmetries. In contrast to the exchange energy the correlation energy becomes less relevant with increasing field strength. This holds for the individual configurations constituting the ground state and for the crossovers of the global ground state.Comment: 4 Figures acc.f.publ.in Phys.Rev.

Potential Neutrino Signals from Galactic Gamma-Ray Sources

The recent progress made in Galactic gamma-ray astronomy using the High Energy Stereoskopic System (H.E.S.S.) instrument provides for the first time a population of Galactic TeV gamma-rays, and hence potential neutrino sources, for which the neutrino flux can be estimated. Using the energy spectra and source morphologies measured by H.E.S.S., together with new parameterisations of pion production and decay in hadronic interactions, we estimate the signal and background rates expected for these sources in a first-generation water Cherenkov detector (ANTARES) and a next-generation neutrino telescope in the Mediterranean Sea, KM3NeT, with an instrumented volume of 1 km^3. We find that the brightest gamma-ray sources produce neutrino rates above 1 TeV, comparable to the background from atmospheric neutrinos. The expected event rates of the brightest sources in the ANTARES detector make a detection unlikely. However, for a 1 km^3 KM3NeT detector, event rates of a few neutrinos per year from these sources are expected, and the detection of individual sources seems possible. Although generally these estimates should be taken as flux upper limits, we discuss the conditions and type of gamma-ray sources for which the neutrino flux predictions can be considered robust.Comment: 20 pages, 4 figures; v2: ERROR in energy scale of KM3NeT effective neutrino area corrected which resulted in event rates being about a factor 3 too low; v3: grammatical changes and update of references after receiving proof

On-board demux/demod

To make satellite channels cost competitive with optical cables, the use of small, inexpensive earth stations with reduced antenna size and high powered amplifier (HPA) power will be needed. This will necessitate the use of high e.i.r.p. and gain-to-noise temperature ratio (G/T) multibeam satellites. For a multibeam satellite, onboard switching is required in order to maintain the needed connectivity between beams. This switching function can be realized by either an receive frequency (RF) or a baseband unit. The baseband switching approach has the additional advantage of decoupling the up-link and down-link, thus enabling rate and format conversion as well as improving the link performance. A baseband switching satellite requires the demultiplexing and demodulation of the up-link carriers before they can be switched to their assigned down-link beams. Principles of operation, design and implementation issues of such an onboard demultiplexer/demodulator (bulk demodulator) that was recently built at COMSAT Labs. are discussed