A study of various synthetic routes to produce a halogen-labeled traction fluid

Several synthetic routes were studied for the synthesis of the compound 1, 1, 3-trimethyl-1, 3-dicyclohexyl-2 chloropropane. This halogen-labeled fluid would be of use in the study of high traction lubricants under elastohydrodynamic lubrication conditions using infrared emission spectroscopy. The synthetic routes included: dimerization of alpha-methylstyrene, methanol addition to alpha-methylstyrene, a Wittig reaction, and an organometallic approach. Because of steric hindrance and competing reactions, none of these routes were successful

Recent commodity price developments : causes and effects

In the past few years, constant price increases have attracted much attention to commodity markets. The nominal prices of oil and most metals reached record levels, and their real prices reached the highest level in many years. The recent price surge was due mainly to a strong increase in demand for commodities. This can be attributed to the strong economic growth of the past few years and to the integration of a substantial part of the world population into the global economy and international trade. The price increase was also partly the result of supply side developments, such as the scarcity of spare production and refining capacity. This made the oil price sensitive to every event that had a negative influence on the oil supply, such as the recurrent geopolitical tensions. In recent years, economic growth and inflation in the oil-importing countries have been fairly resistant to the sharp increase in commodity prices, largely thanks to the changes in the monetary policy framework in comparison to the seventies, structural changes in the developed countries, the effect of globalisation and the favourable economic environment. Financial markets expect oil prices to remain at high levels in the short- and medium term. Moreover, according to the International Energy Agency and other observers, high oil prices are also expected to persist in the long term. Metal prices are forecast to ease from their current high levels, mainly as a result of supply side flexibility, as extra capacity can be added quite quickly. In view of the major economic impact of oil prices and the increasing concern about the effect of energy consumption on climate change, the government has an important role in the energy debate. Over the last couple of years there have been some initiatives to establish a common European energy and climate policy.commodity markets, energy, metals, oil, OPEC.

Observations of Invertebrate Drift in the Skunk River, Iowa

Invertebrate drift was collected weekly from four sites on the Skunk River in the summer of 1971. Drift was composed primarily of lotic insects. The composition and abundance of drift was related to predominant substrate types and water quality. There was a significant (P =.05) negative correlation between drift density and discharge at sites with sand bottom sediments, but drift density was not related to discharge at sampling areas with gravel and rubble substrates

Cryogenic Q-factor measurement of optical substrates for optimization of gravitational wave detectors

Future generations of gravitational wave interferometers are likely to be operated at cryogenic temperatures because one of the sensitivity limiting factors of the present generation is the thermal noise of end mirrors and beam splitters that occurs in the optical substrates as well as in the dielectric coatings. A possible method for minimizing thermal noise is cooling to cryogenic temperatures, maximizing the mechanical quality factor Q, and maximizing the eigenfrequencies of the substrate. We present experimental details of a new cryogenic apparatus that is suitable for the measurement of the temperature-dependent Q-factor of reflective, transmissive as well as nano-structured grating optics down to 5 K. In particular, the SQUID-based and the optical interferometric approaches to the measurement of the amplitude of vibrating test bodies are compared and the method of ring-down recording is described

High-sensitivity tool for studying phonon related mechanical losses in low loss materials

Fundamental mechanical loss mechanisms exist even in very pure materials, for instance, due to the interactions of excited acoustic waves with thermal phonons. A reduction of these losses in a certain frequency range is desired in high precision instruments like gravitational wave detectors. Systematic analyses of the mechanical losses in those low loss materials are essential for this aim, performed in a highly sensitive experimental set-up. Our novel method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy), is well suited to systematically determine losses at the resonant frequencies of the samples of less than 10^(-9) in the wide temperature range from 5 to 300 K. A high precision set-up in a specially built cryostat allows contactless excitation and readout of the oscillations of the sample. The experimental set-up and measuring procedure are described. Limitations to our experiment due to external loss mechanisms are analysed. The influence of the suspension system as well as the sample preparation is explained.Comment: 4 pages, 3 figures, proceedings of PHONONS07, submitted to Journal of Physics: Conference Serie

Dark-State Polaritons for multi-component and stationary light fields

We present a general scheme to determine the loss-free adiabatic eigensolutions (dark-state polaritons) of the interaction of multiple probe laser beams with a coherently driven atomic ensemble under conditions of electromagnetically induced transparency. To this end we generalize the Morris-Shore transformation to linearized Heisenberg-Langevin equations describing the coupled light-matter system in the weak excitation limit. For the simple lambda-type coupling scheme the generalized Morris-Shore transformation reproduces the dark-state polariton solutions of slow light. Here we treat a closed-loop dual-V scheme wherein two counter-propagating control fields generate a quasi stationary pattern of two counter-propagating probe fields -- so-called stationary light. We show that contrary to previous predictions,there exists a single unique dark-state polariton; it obeys a simple propagation equation.Comment: 6 pages, 2 figure

High transport currents in mechanically reinforced MgB2 wires

We prepared and characterized monofilamentary MgB2 wires with a mechanically reinforced composite sheath of Ta(Nb)/Cu/steel, which leads to dense filaments and correspondingly high transport currents up to Jc = 10^5 A/cm^2 at 4.2 K, self field. The reproducibility of the measured transport currents was excellent and not depending on the wire diameter. Using different precursors, commercial reacted powder or an unreacted Mg/B powder mixture, a strong influence on the pinning behaviour and the irreversibility field was observed. The critical transport current density showed a nearly linear temperature dependency for all wires being still 52 kA/cm^2 at 20 K and 23 kA/cm^2 at 30 K. Detailed data for Jc(B,T) and Tc(B) were measured.Comment: 21 pages, 13 figures, revised version, to be published in Supercond. Sci. Techno