Effects of vinyl substitutions on resonance Raman spectra of (bacterio)chlorophylls

Soret resonance and Qy preresonance Raman spectra are reported and compared for a series of (bacterio)chlorophylls. Chlorophyll a, 2-acetylchlorophyll a, bacteriochlorophyll a and 2-vinylbacteriochlorophyll a were studied in the non-protic solvent tetrahydrofuran. These experiments were designed to identify Raman bands corresponding to the stretching mode(s) of the vinyl group at the C-2 position of ring I of chlorophyll a and 2-vinylbacteriochlorophyll a, and to ascertain whether additional bands corresponding to Ca Cm and/or Cb Cb vibrations could be observed in the 1615-1660 cm-1 region. Raman spectra of chlorophyll a and 2-vinylbacteriochlorophyll a exhibit a 1625 cm-1 band, which is absent from the Raman spectra of 2-acetylchlorophyll a and bacteriochlorophyll a. It is assigned to the vC2a C2b mode of the vinyl group. No other band can be definitively assigned to any mode predominantly arising from vinyl motions. The acetyl-containing molecules 2-acetylchlorophyll a and bacteriochlorophyll a give rise to a ca. 1070 cm-1 band, which appears to be related to the presence of the acetyl substituent. The 1615-1660 cm-1 region of the Raman spectra of all four derivatives did not contain any additional band which could be ascribed to modes involving the vCa Cm and/or Cb Cb coordinates

Oil and the Macroeconomy Since the 1970s

Increases in oil prices have been held responsible for recessions, periods of excessive inflation, reduced productivity and lower economic growth. In this paper, we review the arguments supporting such views. First, we highlight some of the conceptual difficulties in assigning a central role to oil price shocks in explaining macroeconomic fluctuations, and we trace how the arguments of proponents of the oil view have evolved in response to these difficulties. Second, we challenge the notion that at least the major oil price movements can be viewed as exogenous with respect to the US macroeconomy. We examine critically the evidence that has led many economists to ascribe a central role to exogenous political events in modeling the oil market, and we provide arguments in favor of 'reverse causality' from macroeconomic variables to oil prices. Third, although none of the more recent oil price shocks has been associated with stagflation in the US economy, a major reason for the continued popularity of the oil shock hypothesis has been the perception that only oil price shocks are able to explain the US stagflation of the 1970s. We show that this is not the case.

Do We Really Know that Oil Caused the Great Stagflation? A Monetary Alternative

This paper argues that major oil price increases were not nearly as essential a part of the causal mechanism that generated the stagflation of the 1970s as is often thought. There is neither a theoretical presumption that oil supply shocks are stagflationary nor robust empirical evidence for this view. In contrast, we show that monetary expansions and contractions can generate stagflation of realistic magnitude even in the absence of supply shocks. Furthermore, monetary fluctuations help to explain the historical movements of the prices of oil and other commodities, including the surge in the prices of industrial commodities that preceded the 1973/74 oil price increase. Thus, they can account for the striking coincidence of major oil price increases and worsening stagflation.

Self-propelled particles with selective attraction-repulsion interaction - From microscopic dynamics to coarse-grained theories

In this work we derive and analyze coarse-grained descriptions of self-propelled particles with selective attraction-repulsion interaction, where individuals may respond differently to their neighbours depending on their relative state of motion (approach versus movement away). Based on the formulation of a nonlinear Fokker-Planck equation, we derive a kinetic description of the system dynamics in terms of equations for the Fourier modes of a one-particle density function. This approach allows effective numerical investigation of the stability of possible solutions of the system. The detailed analysis of the interaction integrals entering the equations demonstrates that divergences at small wavelengths can appear at arbitrary expansion orders. Further on, we also derive a hydrodynamic theory by performing a closure at the level of the second Fourier mode of the one-particle density function. We show that the general form of equations is in agreement with the theory formulated by Toner and Tu. Finally, we compare our analytical predictions on the stability of the disordered homogeneous solution with results of individual-based simulations. They show good agreement for sufficiently large densities and non-negligible short-ranged repulsion. Disagreements of numerical results and the hydrodynamic theory for weak short-ranged repulsion reveal the existence of a previously unknown phase of the model consisting of dense, nematically aligned filaments, which cannot be accounted for by the present Toner and Tu type theory of polar active matter.Comment: revised version, 37pages, 11 figure

China, the United States, and the Climate Change Challenge

Outlines China's climate change policy, U.S. concerns about transfer of carbon-intensive jobs to China and ways to address them, ways for U.S. policy and legislation to spur China's adoption of clean technologies, and specific mechanisms for cooperation

The highD Dataset: A Drone Dataset of Naturalistic Vehicle Trajectories on German Highways for Validation of Highly Automated Driving Systems

Scenario-based testing for the safety validation of highly automated vehicles is a promising approach that is being examined in research and industry. This approach heavily relies on data from real-world scenarios to derive the necessary scenario information for testing. Measurement data should be collected at a reasonable effort, contain naturalistic behavior of road users and include all data relevant for a description of the identified scenarios in sufficient quality. However, the current measurement methods fail to meet at least one of the requirements. Thus, we propose a novel method to measure data from an aerial perspective for scenario-based validation fulfilling the mentioned requirements. Furthermore, we provide a large-scale naturalistic vehicle trajectory dataset from German highways called highD. We evaluate the data in terms of quantity, variety and contained scenarios. Our dataset consists of 16.5 hours of measurements from six locations with 110 000 vehicles, a total driven distance of 45 000 km and 5600 recorded complete lane changes. The highD dataset is available online at: http://www.highD-dataset.comComment: IEEE International Conference on Intelligent Transportation Systems (ITSC) 201

Forecasting the Price of Oil

We address some of the key questions that arise in forecasting the price of crude oil. What do applied forecasters need to know about the choice of sample period and about the tradeoffs between alternative oil price series and model specifications? Are real or nominal oil prices predictable based on macroeconomic aggregates? Does this predictability translate into gains in out-of-sample forecast accuracy compared with conventional no-change forecasts? How useful are oil futures markets in forecasting the price of oil? How useful are survey forecasts? How does one evaluate the sensitivity of a baseline oil price forecast to alternative assumptions about future demand and supply conditions? How does one quantify risks associated with oil price forecasts? Can joint forecasts of the price of oil and of U.S. real GDP growth be improved upon by allowing for asymmetries?Econometric and statistical methods; International topics