Improving the currency composition of external debt : applications in Indonesia and Turkey

Changes in exchange rates affect both the level and the structure of a country's external debt. Indonesia's debt service increased from 10 percent in 1980 to 37 percent in 1986, largely because of the depreciation of the U.S. dollar and the fall in oil prices. Developed countries can hedge against exchange rate and commodity price changes by purchasing currency futures or other hedging instruments, but most developing countries do not have access to futures markets. They can, however, reduce their exposure by matching the currency composition of their external debt with the currency composition of the cash flows with which they service their debt. Using advanced econometric techniques, the authors analyze what the currency exposures might have been in Indonesia and Turkey, and suggest borrowing portfolios that might be effective in hedging these countries'terms of trade against exchange rate fluctuations. The results are promising for Indonesia, where the optimal currency portfolios might have resulted in a significant reduction in risk. The results are less satisfying for Turkey, although they do indicate possible research directions.Economic Theory&Research,Fiscal&Monetary Policy,Environmental Economics&Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Macroeconomic Management

Realization of an atomically thin mirror using monolayer MoSe2

Advent of new materials such as van der Waals heterostructures, propels new research directions in condensed matter physics and enables development of novel devices with unique functionalities. Here, we show experimentally that a monolayer of MoSe2 embedded in a charge controlled heterostructure can be used to realize an electrically tunable atomically-thin mirror, that effects 90% extinction of an incident field that is resonant with its exciton transition. The corresponding maximum reflection coefficient of 45% is only limited by the ratio of the radiative decay rate to the linewidth of exciton transition and is independent of incident light intensity up to 400 Watts/cm2. We demonstrate that the reflectivity of the mirror can be drastically modified by applying a gate voltage that modifies the monolayer charge density. Our findings could find applications ranging from fast programmable spatial light modulators to suspended ultra-light mirrors for optomechanical devices

Simus inter Exempla: Exempla and Innovation in Valerius Maximus, Seneca and Juvenal

Exempla, vivid stories recounting laudable or shameful actions performed by named individuals, were a common rhetorical device in ancient Roman literature. Generally, they were meant to encourage emulation of good deeds and avoidance of bad. In this work, I investigate how Valerius Maximus, the philosopher Seneca, and the satirist Juvenal employ and deviate from the exemplary tradition, specifically focusing on negative exempla. While Valerius’ encyclopedia of exempla categorized by representative virtue or vice remains within the usual rhetorical sphere (though remarkable for its size - 967 stories), Seneca and Juvenal deliberately endeavor to innovate within the framework of exemplary discourse. Seneca tends to consider more private, personal events, whereas Juvenal emphasizes the publicity, shock-value, and humor possible with detailed accounts of everyday vice parading through Rome. Both provide theories about how vice spreads and how exempla might function, illustrating that they are not merely content to use exempla as in past authors, like Valerius, but want to use them for their own purposes. In alignment with his Stoic beliefs, Seneca uses exempla in part to establish a moral code that does not deal with legal courts or public office, but rather daily life. For Juvenal, in contrast, the theorizing helps to justify his never-ending list of negative exempla and provides comic moments, albeit sometimes ones with disturbing overtones. Finally, although it seems that exempla are traditional by definition, new exempla must also be created at certain points. The tendency in Seneca and Juvenal to use new, rather than old exempla, which are prominent in the work of Valerius Maximus, shows that they are consciously working to expand and continue the tradition of exempla in unique ways. Thus, from Valerius’ relatively simple compendium of exempla to Seneca’s works and Juvenal’s Satires, the exemplary tradition remained vibrant, expanding to accommodate the purposes of different authors

Development of a high throughput screen for the expression of membrane proteins and their purification and crystallisation

Every biological cell is surrounded by a membrane, which functions as a barrier to the environment and as a support matrix for membrane proteins. Membrane proteins facilitate the transport of manifold substrates across the membrane and are involved in fundamental cellular processes, such as signalling or energy generation to name a few. The key to the function of membrane proteins lies in their three dimensional structure, which can be determined by single crystal X-ray crystallography. However, membrane proteins are one of the most difficult protein classes to work with, which is reflected by the small number of available membrane protein structures. Protein crystallography requires milligram amounts of pure protein, which has to be expressed and purified to monodispersity to allow crystallisation. As membrane proteins have to be inserted into the membrane, recombinant expression yields are often low. In order to obtain enough protein for purification and crystallisation studies, the expression of membrane proteins requires screening for the best expression conditions. Purification of membrane proteins requires, due to their amphipathic character, the use of detergents to solubilise the membrane protein. The optimal combination of detergent and membrane protein is crucial for stability in aqueous solution in order to allow purification to monodispersity. Furthermore, the detergent has a high influence on the crystallisation of membrane proteins. An approach to overcome the challenges of membrane protein structural biology is to work in a high throughput (HTP) manner to increase the chances of success. The aim is to find the most promising targets out of a library of membrane proteins and in the presented work a small-scale HTP expression screen was developed in order to find the optimal expression conditions for each membrane protein from a target library of 12 E. coli inner membrane proteins. The targets were then expressed in the determined optimal conditions in sufficient amounts to allow purification. All membrane proteins were subjected to a purification pipeline, which employed a subset of parameters, that have proved to be the most successful to date in membrane protein purification for structural studies. Five membrane proteins were purified to monodispersity and were submitted to crystallisation trials. Crystals of two targets were obtained, which diffracted to 7 Å and 15 Å. Furthermore, the data collected on the expression and purification behaviour of the 12 membrane proteins, will help to optimise the starting parameters for the screening of future targets

Effects of Growth Temperatures and Elevated CO2 on Respiration Rates in Norway Spruce

Projected increase in growth temperatures and CO2 may affect carbon balance in Norway spruce (Picea abies), a dominant coniferous species of the boreal forest ecosystem. To examine this, I exposed three-year-old Norway spruce seedlings to six treatments: ambient (400 ppm) and elevated (750 ppm) CO2 concentrations combined with three growth temperatures: ambient, ambient +4 oC, and ambient +8 oC. I found that while net growth was generally not affected by growth CO2 or temperature, leaf nitrogen concentrations were reduced, mortality rates were higher, and needles were shorter and thinner in +8 oC treatments, compared to cooler treatments. I found that net CO2 assimilation rates and dark respiration acclimated to temperature but not CO2, while patterns of acclimation of light respiration in the light varied between years. The highest net CO2 assimilation rates were found in trees grown at +4 oC combined with elevated CO2, which could indicate that a slight increase in growth temperature with elevated CO2 may benefit the carbon balance of Norway spruce. However, further warming had negative effects on carbon uptake, with trees from the +8 oC treatments showing the lowest CO2 assimilation and dark respiration rates. The Q10 of light respiration was 35% higher than the Q10 of dark respiration, so that the ratio of light respiration to dark respiration increased as leaf temperature increased. I conclude that light respiration is not a constant fraction of dark respiration, although both parameters are tightly correlated, and this relationship can be used to improve models of terrestrial vegetation

Deterministic entanglement between a propagating photon and a singlet--triplet qubit in an optically active quantum dot molecule

Two-electron charged self-assembled quantum dot molecules exhibit a decoherence-avoiding singlet-triplet qubit subspace and an efficient spin-photon interface. We demonstrate quantum entanglement between emitted photons and the spin-qubit after the emission event. We measure the overlap with a fully entangled state to be $69.5\pm2.7\,\%$, exceeding the threshold of $50\,\%$ required to prove the non-separability of the density matrix of the system. The photonic qubit is encoded in two photon states with an energy difference larger than the timing resolution of existing detectors. We devise a novel heterodyne detection method, enabling projective measurements of such photonic color qubits along any direction on the Bloch sphere

Forecasting volatility in commodity markets

Commodity prices have historically been among the most volatile of international prices. Measured volatility (the standard deviation of price changes) has not been below 15 percent and at times has been more than 50 percent. Often the volatility of commodity prices has exceeded that of exchange rates and interest rates. The large price variations are caused by disturbances in demand and supply. Stockholding leads to some price smoothing, but when stocks are low, prices can jump sharply. As a result, commodity price series are not stationary and in some periods they jump abruptly to high levels or fall precipitously to low levels relative to their long-run average. Thus it is difficult to determine long-term price trends and the underlying distribution of prices. The volatility of commodity prices makes price forecasting difficult. Indeed, realized prices often deviate greatly from forecasted prices, which has led to the practice of giving forecasts probability ranges. But assigning probability ranges requires forecasting future price volatility, which, given uncertainties about true price distribution, is difficult. One potentially useful source of information for forecasting volatility is the volatility forecasts imbedded in the prices of options written on commodities traded in exchanges. Options give the holder the right to buy (call) or sell (put) a certain commodity at a certain date at a fixed (exercise) price. Options prices depend on several variables, one of which is the expected volatility up to the maturity date. Given a specific theoretical model, the market prices of options can be used to derive the market's expectations about price volatility and the price distribution. The authors systematically analyze different methods'abilities to forecast commodity price volatility (for several commodities). They collected the daily prices of commodity options and other variables for seven commodities (cocoa, corn, cotton, gold, silver, sugar, and wheat). They extracted the volatility forecasts implicit in options prices using several techniques. They compared several volatility forecasting methods, divided into three categories: (1) forecasts using only expectations derived form options prices; (2) forecasts using only time-series modeling; (3) forecasts that combine market expectations and time-series modeling (a new method devised for this purpose). They find that the volatility forecasts produced by method 3 outperform the first two as well as the naive forecast based on historical volatility. This result holds both in and out of sample for almost all commodities considered.Markets and Market Access,Access to Markets,Economic Theory&Research,Economic Forecasting,Science Education