E7(7) constraints on counterterms in N=8 supergravity

We prove by explicit computation that 6-point matrix elements of D^4R^4 and D^6R^4 in N=8 supergravity have non-vanishing single-soft scalar limits, and therefore these operators violate the continuous E7(7) symmetry. The soft limits precisely match automorphism constraints. Together with previous results for R^4, this provides a direct proof that no E7(7)-invariant candidate counterterm exists below 7-loop order. At 7-loops, we characterize the infinite tower of independent supersymmetric operators D^4R^6, R^8, phi^2 R^8,... with n>4 fields and prove that they all violate E7(7) symmetry. This means that the 4-graviton amplitude determines whether or not the theory is finite at 7-loop order. We show that the corresponding candidate counterterm D^8R^4 has a non-linear supersymmetrization such that its single- and double-soft scalar limits are compatible with E7(7) up to and including 6-points. At loop orders 7, 8, 9 we provide an exhaustive account of all independent candidate counterterms with up to 16, 14, 12 fields, respectively, together with their potential single-soft scalar limits.Comment: 9 pages, 1 table. Reference added, minor clarifications in abstract, typos correcte

Comparison between phosphine and NHC-modified Pd catalysts in the telomerization of butadiene with methanol – a kinetic study combined with model-based experimental analysis

The authors thank the European Community within its project SYNFLOW (FP7; grant agreement n8 NMP2-LA-2010-246461) for financial support.The telomerization of butadiene with methanol was investigated in the presence of different palladium catalysts modified either with triphenylphosphine (TPP) or 1,3-dimesityl-imidazol-2-ylidene (IMes) ligand. When pure butadiene was used as substrate, a moderate selectivity for the Pd-TPP catalyst toward the desired product 1-methoxy-2,7-octadiene (1-Mode) of around 87 % was obtained, while the IMes carbene ligand almost exclusively formed 1-Mode with 97.5 % selectivity. The selectivity remained unchanged when the pure butadiene feed was replaced by synthetic crack-C4 (sCC4), a technical feed of 45 mol% butadiene and 55 mol% inerts (butenes and butanes). The TPP-modified catalyst showed a lower reaction rate, which was attributed to the expected dilution effect caused by the inerts. Surprisingly, the IMes-modified catalyst showed a higher rate with sCC4 compared to the pure feed. By means of a model-based experimental analysis, kinetic rate equations could be derived. The kinetic modeling supports the assumption that the two catalyst systems follow different kinetic rate equations. For the Pd-TPP catalyst, the reaction kinetics were related to the Jolly mechanism. In contrast, the Jolly mechanism had to be adapted for the Pd-IMes catalyst as the impact of the base seems to differ strongly from that for the Pd-TPP catalyst. The Pd-IMes system was found to be zero order in butadiene at moderate to high butadiene concentrations and first order in base while the nucleophilicity of the base is influenced by the methanol amount resulting in a negative reaction order for methanol.PostprintPeer reviewe

Dehydrogenation of perhydro-N-ethylcarbazole under reduced total pressure

Liquid organic hydrogen carrier (LOHC) systems represent a promising storage option for hydrogen produced from renewable electricity by water electrolysis. Regarding the efficiency of the endothermal hydrogen release reaction, this technology greatly benefits from a direct heat integration with the waste heat of the energetic use of the released hydrogen, e. g. in a fuel cell. To enable such beneficial set-up, the reaction temperature of hydrogen release must be below the operation temperature of the applied fuel cell which calls for both low temperature dehydrogenation catalysis and high temperature fuel cell operation. This paper demonstrates that such combination may be suitable if reduced pressure dehydrogenation of perhydro-N-ethylcarbazole (H12-NEC) is combined with hydrogen electrification in a high temperature polymer electrolyte membrane fuel cell (HT PEMFC). Dehydrogenation reactions of H12-NEC were carried out between 160 °C and 200 °C applying different hydrogen partial pressures in the dehydrogenation unit to mimic the effect of a sucking fuel cell operation mode, i.e. the reduction of hydrogen partial pressure in the dehydrogenation unit caused by the fuel cell operation. Our kinetic analysis reveals that a dehydrogenation temperature of 180 °C combined with 500 mbar hydrogen partial pressure represent, for example, a suitable parameter set for efficient hydrogen release

1-Bit Full Adder in Perpendicular Nanomagnetic Logic using a Novel 5-Input Majority Gate

In this paper, we show that perpendicular Nanomagnetic Logic (pNML) is particularly suitable to realize threshold logic gate (TLG)-based circuits. Exemplarily, a 1-bit full adder circuit using a novel 5-input majority gate based on TLGs is experimentally demonstrated. The theory of pNML and its extension by TLGs is introduced, illustrating the great benefit of pNML. Majority gates based on coupling field superposition enable weighting each input by its geometry and distance to the output. Only 5 magnets, combined in two logic gates with a footprint of 1:95 µm2 and powered by a perpendicular clocking field, are required for operation. MFM and magneto-optical measurements demonstrate the functionality of the fabricated structure. Experimental results substantiate the feasibility and the benefits of the combination of threshold logic with pNML

1-Bit Full Adder in Perpendicular Nanomagnetic Logic using a Novel 5-Input Majority Gate

In this paper, we show that perpendicular Nanomagnetic Logic (pNML) is particularly suitable to realize threshold logic gate (TLG)-based circuits. Exemplarily, a 1-bit full adder circuit using a novel 5-input majority gate based on TLGs is experimentally demonstrated. The theory of pNML and its extension by TLGs is introduced, illustrating the great benefit of pNML. Majority gates based on coupling field superposition enable weighting each input by its geometry and distance to the output. Only 5 magnets, combined in two logic gates with a footprint of 1:95 µm2 and powered by a perpendicular clocking field, are required for operation. MFM and magneto-optical measurements demonstrate the functionality of the fabricated structure. Experimental results substantiate the feasibility and the benefits of the combination of threshold logic with pNML