Non-equilibrium noise in the (non-)Abelian fractional quantum Hall effect

We analyse the noise of the edge current of a generic fractional quantum Hall state in a tunnelling point contact system. We show that the non-symmetrized noise in the edge current for the system out-of-equilibrium is completely determined by the noise in the tunnelling current and the Nyquist-Johnson (equilibrium) noise of the edge current. Simply put, the noise in the tunnelling current does not simply add up the equilibrium noise of the edge current. A correction term arises associated with the correlation between the tunnelling current and the edge current. We show, using a non-equilibrium Ward identity, that this correction term is determined by the anti-symmetric part of the noise in the tunnelling current. This leads to a non-equilibrium fluctuation-dissipation theorem and related expressions for the excess and shot noise of the noise in the edge current. Our approach makes use of simple properties of the edge, such as charge conservation and chirality, and applies to generic constructions of the edge theory which includes edges of non-Abelian states and edges with multiple charged channels. Two important tools we make use of are the non-equilibrium Kubo formula and the non-equilibrium Ward identity. We discuss these identities in the appendix.Comment: 20 pages, 5 figure

The use of niobia in oxidation catalysis

This paper summarises the background to work carried out at the University of Twente on the use of niobia as a catalyst for the oxidative dehydrogenation of propane to propylene and discusses the development of promoted niobia catalysts for this reaction. Results are also presented which illustrate the use of niobia in catalysts for other reactions such as the oxidative coupling of methane, the oxidative dehydrogenation of ethane and the oxidative dehydrogenation of methanol. It appears that niobia and niobia-modified catalysts, when used in high-temperature oxidation processes, can exhibit relatively high selectivities compared with more conventional catalysts

Influence of preparation method on the performance of vanadia-niobia catalysts for the oxidative dehydrogenation of propane

The influence of various preparation methods on the performance of V-Nb-0 catalysts has been investigated. It was found that the activity and selectivity of a vanadium site depend on the nature of the neighbouring atoms. Vanadium neighbours provide activity, while niobium neighbours provide selectivity. Careful preparation of these catalysts ensures a homogeneous distribution and good mixing of the vanadium and niobium. It was also found that the vanadium becomes mobile upon reduction and this results in better distribution of vanadium in used catalysts

In search of relevance: The changing contract between science and society

This paper presents a framework to study the historical development of the relationship between science and society. We elaborate this relationship as a contract that specifies the mission of scientific research, the rationales for public support for science, and the conditions under which scientists work. These three structural elements will always be part of the contract, but their specific content can vary. The credibility cycle, as a model for scientific practice, helps to describe and understand the consequences of a changing contract for the work of individual scientists. A brief case study of chemistry in the Netherlands demonstrates the usefulness of the framework. We show how concepts of relevance have changed since 1975 and how this affects the practice of academic chemistry.relevance, contract, credibility cycle, chemistry

Longitudinal spin-relaxation in nitrogen-vacancy centers in electron irradiated diamond

We present systematic measurements of longitudinal relaxation rates ($1/T_1$) of spin polarization in the ground state of the nitrogen-vacancy (NV$^-$) color center in synthetic diamond as a function of NV$^-$ concentration and magnetic field $B$. NV$^-$ centers were created by irradiating a Type 1b single-crystal diamond along the [100] axis with 200 keV electrons from a transmission electron microscope with varying doses to achieve spots of different NV$^-$ center concentrations. Values of ($1/T_1$) were measured for each spot as a function of $B$.Comment: 4 pages, 8 figure

Resonant diaphragm pressure measurement system with ZnO on Si excitation

The principle of measuring pressure by means of a resonant diaphragm has been studied. An oscillator consisting of an integrated amplifier with a piezoelectrically driven diaphragm in its feedback loop has been built. The oscillator frequency is accurately proportional to the square of the pressure in the range of 60 to 130 Torr.\ud The frequency range is 1324 to 1336 Hz (this range being limited by a spurious mode which could be suppressed by better processing) for a 25 mm diameter diaphragm made of a silicon wafer and with PZT ceramics as driver and receptor. We have made an integrated version (1 × 1 mm2) of a square resonant diaphragm pressure guage by selective etching of (1 0 0) planes with ethylenediamine. The piezoelectric driving materials was sputtered zinc oxide. A driver was deposited midway between the bending point and the point of greatest curvature.\ud A receptor was located at a symmetrical position to give a optimum transfer condition.\ud The integrated current amplifier had a low impedance differential input stage, two gain cells and a high impedance output stage. These electrical conditions ensured maximum elastic freedom of the diaphragm. A digital circuit in I2L technology has been designed and made with eight-bit parallel read out of the frequency. This circuit may be directly connected to a microprocessor. The whole system contains the sensor chip, the analog amplifier chip and the digital chip, all in compatible technology.\ud \u

Theoretical He I Emissivities in the Case B Approximation

We calculate the He I case B recombination cascade spectrum using improved radiative and collisional data. We present new emissivities over a range of electron temperatures and densities. The differences between our results and the current standard are large enough to have a significant effect not only on the interpretation of observed spectra of a wide variety of objects but also on determinations of the primordial helium abundance.Comment: Accepted to ApJ

Wall-bounded turbulent flows at high Reynolds numbers: Recent advances and key issues

Wall-bounded turbulent flows at high Reynolds numbers have become an increasingly active area of research in recent years. Many challenges remain in theory, scaling, physical understanding, experimental techniques, and numerical simulations. In this paper we distill the salient advances of recent origin, particularly those that challenge textbook orthodoxy. Some of the outstanding questions, such as the extent of the logarithmic overlap layer, the universality or otherwise of the principal model parameters such as the von Kármán “constant,” the parametrization of roughness effects, and the scaling of mean flow and Reynolds stresses, are highlighted. Research avenues that may provide answers to these questions, notably the improvement of measuring techniques and the construction of new facilities, are identified. We also highlight aspects where differences of opinion persist, with the expectation that this discussion might mark the beginning of their resolution