C-N Coupling in Reactions between Atomic Nitrogen and Ethylene on Rh(111)

Reactions between adsorbed at. nitrogen and ethylene on Rh(111) have been investigated by temp.-programmed reaction spectroscopy (TPRS), secondary ion mass spectrometry (SIMS), and work function measurements. Coadsorption of a small amt. of ethylene to 0.10 monolayer of at. nitrogen results in the formation of a surface cyanide species, which is detected by SIMS through the Rh2CN+ cluster ion. Cyanide formation has been followed by measuring the decrease of the at. nitrogen and carbon coverages and the accompanied increase in the CN coverage in temp.-programmed SIMS expts. The CN formation kinetics is described by a preexponential factor and an activation energy of 1011+-1 s-1 and 111 +- 10 kJ/mol, resp. In the absence of surface hydrogen, CN groups are stable up to .apprx.700 K. CN decompn. results in reaction-limited desorption of N2 with a max. at 800 K and is described by a preexponential factor and an activation energy of 1013+-1 s-1 and 210 +- 15 kJ/mol. Coadsorption of large amts. of ethylene to 0.10 monolayer of Nads results in the desorption of almost all nitrogen in the form of HCN between 500 and 700 K. Cyanogen was also obsd. as a reaction product although the selectivity was small, 3% at max. Work function measurements indicate that surface cyanide is present as a neg. charged species on the Rh(111) surfac

Formation of NH3 and N-2 from Atomic Nitrogen and Hydrogen on Rhodium(111)

Reactions of adsorbed N atoms on Rh(111) to N2 and NH3 were studied with temp. programmed desorption, temp. programmed reaction spectroscopy, and static secondary ion mass spectrometry. For N-atom coverages below ~0.15 monolayers, desorption of N2 follows simple second-order kinetics, but at higher coverages the desorption traces broaden to higher temps. Hydrogenation to NH3 can be described by a stepwise addn. of H atoms to Nads in which the reaction from NH2,ads+Hads to NH3,ads dets. the rate. The activation energy for the rate detg. step is 76 kJ/mol. The desorption of NH3 from Rb(111) was studied sep. The kinetic parameters for desorption at low NH3 coverage are 81 kJ/mol and 1013 s-1, but the rate of desorption increases rapidly with increasing NH3 coverage. It is argued that the remarkable coverage dependence of the desorption rate is unlikely to be caused by lateral repulsive interactions but may be due to a coverage of the pre-exponential facto

C-N Coupling in Reactions between Atomic Nitrogen and Ethylene on Rh(111)

Reactions between adsorbed at. nitrogen and ethylene on Rh(111) have been investigated by temp.-programmed reaction spectroscopy (TPRS), secondary ion mass spectrometry (SIMS), and work function measurements. Coadsorption of a small amt. of ethylene to 0.10 monolayer of at. nitrogen results in the formation of a surface cyanide species, which is detected by SIMS through the Rh2CN+ cluster ion. Cyanide formation has been followed by measuring the decrease of the at. nitrogen and carbon coverages and the accompanied increase in the CN coverage in temp.-programmed SIMS expts. The CN formation kinetics is described by a preexponential factor and an activation energy of 1011+-1 s-1 and 111 +- 10 kJ/mol, resp. In the absence of surface hydrogen, CN groups are stable up to .apprx.700 K. CN decompn. results in reaction-limited desorption of N2 with a max. at 800 K and is described by a preexponential factor and an activation energy of 1013+-1 s-1 and 210 +- 15 kJ/mol. Coadsorption of large amts. of ethylene to 0.10 monolayer of Nads results in the desorption of almost all nitrogen in the form of HCN between 500 and 700 K. Cyanogen was also obsd. as a reaction product although the selectivity was small, 3% at max. Work function measurements indicate that surface cyanide is present as a neg. charged species on the Rh(111) surfac

Modeling of the reactivity of vibrationally excited molecules in a corona plasma for catalytic reactions

A model is developed to describe the transfer of vibrational energy from excited gas molecules to a heterogeneous surface or to heating of the gas. Diffusion of excited species is included in the model. The model is used to compute the maximum possible energy efficiency of a plasma-induced catalytic reaction, which is driven by vibrationally excited molecules. The computational results of the model are correlated to experimental data on quenching rates and the relevant parameters of the self-sustained discharge. It is con cluded that the mechanism of plasma-induced catalysis with vibrationally excited molecules is highly unlikely

Cyanide intermediates in catalytic reduction of NO by C2H4 on Rhodium(III)

Temp.-programmed reaction spectroscopy and secondary ion mass spectrometry (SIMS) have been applied to study reactions of NO and C2H4 coadsorbed on Rh(111). As expected, H2O, CO2, and N2 are the main products at low C2H4 coverages, but at higher coverages H2, HCN, CO, and NO, and even some C2N2 evolve as well. Static SIMS indicates the formation of a large supply of adsorbed cyanide species, part of which desorbs as HCN, while the remainder decomps. and is responsible for delayed formation of N2. For the highest C2H4 coverages, the majority of the nitrogen atoms in the initially adsorbed NO desorbs as HC

The Digital Police Officer using linguistic analysis to identify cybercriminals

The aim of the Digital Police Officer project (DPO) is to identify cybercriminals based on their writing style. When a criminal underground forum is closed down, cybercriminals move to another one to further their illicit business. These users do not necessarily return with the same uername. We are producing a demo that can still identify such cybercriminals. We look at the way they communicate, analysing the characteristics of forum users (i.e. based on their vocabulary and grammar) to build a linguistic fingerprin

You can't see what you can't see: Experimental evidence for how much relevant information may be missed due to Google's Web search personalisation

The influence of Web search personalisation on professional knowledge work is an understudied area. Here we investigate how public sector officials self-assess their dependency on the Google Web search engine, whether they are aware of the potential impact of algorithmic biases on their ability to retrieve all relevant information, and how much relevant information may actually be missed due to Web search personalisation. We find that the majority of participants in our experimental study are neither aware that there is a potential problem nor do they have a strategy to mitigate the risk of missing relevant information when performing online searches. Most significantly, we provide empirical evidence that up to 20% of relevant information may be missed due to Web search personalisation. This work has significant implications for Web research by public sector professionals, who should be provided with training about the potential algorithmic biases that may affect their judgments and decision making, as well as clear guidelines how to minimise the risk of missing relevant information.Comment: paper submitted to the 11th Intl. Conf. on Social Informatics; revision corrects error in interpretation of parameter Psi/p in RBO resulting from discrepancy between the documentation of the implementation in R (https://rdrr.io/bioc/gespeR/man/rbo.html) and the original definition (https://dl.acm.org/citation.cfm?id=1852106) as per 20/05/201

Василь Васильович Тарновський: духовні витоки українського патріотизму та благодійності

Context: Climate change can directly affect habitats within ecological networks, but may also have indirect effects on network quality by inducing land use change. The relative impact of indirect effects of climate change on the quality of ecological networks currently remains largely unknown. Objectives: The objective of this study was to determine the relative impact of direct and indirect effects of climate change on a network of breeding habitat of four meadow bird species (Black-tailed godwit, Common redshank, Eurasian oystercatcher and Northern lapwing) in the Netherlands. Methods: Habitat models were developed that link meadow bird breeding densities to three habitat characteristics that are sensitive to environmental change (landscape openness, land use and groundwater level). These models were used to assess the impact of scenarios of landscape change with and without climate change on meadow bird breeding habitat quality for a case study area in the peat meadow district of the Netherlands. Results: All scenarios led to significantly reduced habitat quality for all species, mainly as a result of conversion of grassland to bioenergy crops, which reduces landscape openness. Direct effects of climate change on habitat quality were largely absent, indicating that especially human adaptation to climate change rather than direct effects of climate change was decisive for the degradation of ecological network quality for breeding meadow birds. Conclusions: We conclude that scenario studies exploring impacts of climate change on ecological networks should incorporate both land use change resulting from human responses to climate change and direct effects of climate change on landscapes