Apakah Opec Merupakan Kartel?: Pendekatan Kausalitas Granger dalam Kerangka Vector Autoregressive

One would believe that The Organization of Petroleum Exporting Countries (OPEC) is certainly a cartel which curbs production in order to raise the price of its product as well as to share the market among its members. Did energy shock of the 1970\u27s engineered by an effective cartel of OPEC members acting to share the market by controlling output and influencing market prices? One would also expect OPEC\u27s production to significantly affect the market price of oil as the organization is often accused of curbing production in order to raise prices. This paper tries to determine whether OPEC has the power of affecting the market price of oil and or vice versa. This study uses the Toda and Yamamoto (1995) procedure for testing for Granger non-causality in Vector Autoregressive (VAR) models that involves variables that are integrated of an arbitrary order and that are possibly cointegrated. The results indicate that there is no statistically significant causal relationship between real crude oil price and OPEC production in either direction for full sample period 1974 – 2005. Instead, we find that real crude oil price Granger cause OPEC production in 2 different sub samples period, but not in other direction. As overall we reject cartel hypothesis for OPEC as a whole

Structure of Flux Line Lattices with Weak Disorder at Large Length Scales

Dislocation-free decoration images containing up to 80,000 vortices have been obtained on high quality Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ superconducting single crystals. The observed flux line lattices are in the random manifold regime with a roughening exponent of 0.44 for length scales up to 80-100 lattice constants. At larger length scales, the data exhibit nonequilibrium features that persist for different cooling rates and field histories.Comment: 4 pages, 3 gif images, to appear in PRB rapid communicatio

Atomic Calligraphy: The Direct Writing of Nanoscale Structures Using a Microelectromechanical System

We present a microelectromechanical system (MEMS) based method for the resist-free patterning of nanostructures. Using a focused ion beam to customize larger MEMS machines, we fabricate apertures with features less than 50 nm in diameter on plates that can be moved with nanometer precision over an area greater than 20 × 20 μm². Depositing thermally evaporated gold atoms though the apertures while moving the plate results in the deposition of nanoscale metal patterns. Adding a shutter positioned micrometers above the aperture enables high speed control of not only where but also when atoms are deposited. With this shutter, different-sized apertures can be opened and closed selectively for nanostructure fabrication with features ranging from nano- to micrometers in scale. The ability to evaporate materials with high precision, and thereby fabricate circuits and structures in situ, enables new kinds of experiments based on the interactions of a small number of atoms and eventually even single atoms

High-spectral-efficiency mode-multiplexed transmission over graded-index multimode fiber

We demonstrate mode-multiplexed 90×90 MIMO transmission over all nine mode groups of a 26.5-km graded-index multimode fiber span, achieving a record spectral efficiency of 202 bit/s/Hz