Variable angle photoelectron spectroscopy of the fluoroethylenes

He I photoelectron spectra of fluoroethylene, 1,1‐difluoroethylene, cis‐1,2‐difluoroethylene, trans‐1,2‐difluoroethylene, trifluoroethylene, and perfluoroethylene were obtained over the scattering angle range of 45° to 120° and compared with those of ethylene. Vibrational frequencies of the ionic states were measured and their symmetry modes assigned. The asymmetry parameter β as a function of the ionization potential was measured for each molecule. The value of β for the first ionization potential band of these molecules was found to decrease monotonically with increasing fluorine substitution. This variation was interpreted as being due to resonance mixing of the lone pair F π orbitals with C–C π orbitals. The data obtained were used to assign some of the spectral bands observed

Sputtered silicon nitride coatings for wear protection

Silicon nitride films were deposited by RF sputtering on 304 stainless steel substrates in a planar RF sputtering apparatus. The sputtering was performed from a Si3N4 target in a sputtering atmosphere of argon and nitrogen. The rate of deposition, the composition of the coatings, the surface microhardness and the adhesion of the coatings to the substrates were investigated as a function of the process parameters, such as: substrate target distance, fraction nitrogen in the sputtering atmosphere and sputtering pressure. Silicon rich coating was obtained for fraction nitrogen below 0.2. The rate of deposition decreases continuously with increasing fraction nitrogen and decreasing sputtering pressure. It was found that the adherence of the coatings improves with decreasing sputtering pressure, almost independently of their composition

Some properties of RF sputtered hafnium nitride coatings

Hafnium nitride coatings were deposited by reactive RF sputtering from a hafnium target in nitrogen and argon gas mixtures. The rate of deposition, composition, electrical resistivity and complex index of refraction were investigated as a function of target substrate distance and the fraction nitrogen, (fN2) in the sputtering atmosphere. The relative composition of the coatings is independent on fN2 for values above 0.1. The electric resistivity of the hafnium nitride films changes over 8 orders of magnitude when fN2 changes from 0.10 to 0.85. The index of refraction is almost constant at 2.8(1-0.3i) up to fN2 = 0.40 then decreases to 2.1(1 - 0.01i) for higher values of fN2

Parallel markets, the foreign exchange auction, and exchange rate unification in Zambia

A large thriving parallel market for foreign exchange has coexisted with a rich menu of official exchange rate policies aimed at achieving a more flexible exchange rate and price system as well as financial and trade liberalization. Despite aggresive policies in these areas, particularly for the exchange rate, the black market premium (defined as the ratio of the black market rate to the official rate) remains high. The authors examine the origins of the parallel market, the statistical properties of the parallel premium, and the shocks and macroeconomic policy changes that influence its evolution. Using annual data, they specify and estimate and eclectic error-correction model for the premium. They find that the large parallel market might have caused problems in macroeconomic management and economic reform. Also, the findings show that foreign inflation and depreciation of the black market rate (in a cost-push manner) directly increases domestic inflation. The authors conclude that exchange rate reform without fiscal reform may be futile and that it is important to liberalize major trade and financial markets in such a way as to compress the parallel market and prevent the premium from serving as a major signal to the economy.Environmental Economics&Policies,Fiscal&Monetary Policy,Macroeconomic Management,Economic Theory&Research,Economic Stabilization

Lichen specific thallus mass and secondary compounds change across a retrogressive fire-driven chronosequence

In the long-term absence of major disturbances ecosystems enter a state of retrogression, which involves declining soil fertility and consequently a reduction in decomposition rates. Recent studies have looked at how plant traits such as specific leaf mass and amounts of secondary compounds respond to declining soil fertility during retrogression, but there are no comparable studies for lichen traits despite increasing recognition of the role that lichens can play in ecosystem processes. We studied a group of 30 forested islands in northern Sweden differing greatly in fire history, and collectively representing a retrogressive chronosequence, spanning 5000 years. We used this system to explore how specific thallus mass (STM) and carbon based secondary compounds (CBSCs) change in three common epiphytic lichen species (Hypogymnia phsyodes, Melanohalea olivacea and Parmelia sulcata) as soil fertility declines during this retrogression. We found that STMs of lichens increased sharply during retrogression, and for all species soil N to P ratio (which increased during retrogression) was a strong predictor of STM. When expressed per unit area, medullary CBSCs in all species and cortical CBSCs in P. sulcata increased during retrogression. Meanwhile, when expressed per unit mass, only cortical CBSCs in H. physodes responded to retrogression, and in the opposite direction. Given that lichen functional traits are likely to be important in driving ecological processes that drive nutrient and carbon cycling in the way that plant functional traits are, the changes that they undergo during retrogression could potentially be significant for the functioning of the ecosystem