Versatile Digital GHz Phase Lock for External Cavity Diode Lasers

We present a versatile, inexpensive and simple optical phase lock for applications in atomic physics experiments. Thanks to all-digital phase detection and implementation of beat frequency pre-scaling, the apparatus requires no microwave-range reference input, and permits phase locking at frequency differences ranging from sub-MHz to 7 GHz (and with minor extension, to 12 GHz). The locking range thus covers ground state hyperfine splittings of all alkali metals, which makes this system a universal tool for many experiments on coherent interaction between light and atoms.Comment: 4.5 pages, 5 figures v3: fixed error in schematic: R10 connects to other end of C

A Monolithic Filter Cavity for Experiments in Quantum Optics

By applying a high-reflectivity dielectric coating on both sides of a commercial plano-convex lens, we produce a stable monolithic Fabry-Perot cavity suitable for use as a narrow band filter in quantum optics experiments. The resonant frequency is selected by means of thermal expansion. Owing to the long term mechanical stability, no optical locking techniques are required. We characterize the cavity performance as an optical filter, obtaining a 45 dB suppression of unwanted modes while maintaining a transmission of 60%.Comment: 4 pages, 4 figure

Pain in traumatic upper limb amputees in Sierra Leone.

Data on 40 upper limb amputees (11 bilateral) with regard to stump pain, phantom sensation and phantom pain is presented. All the patients lost their limbs as a result of violent injuries intended to terrorise the population and were assessed 10-48 months after the injury. All amputees reported stump pain in the month prior to interview and ten of the 11 bilateral amputees had bilateral pain. Phantom sensation was common (92.5%), but phantom pain was only present in 32.5% of amputees. Problems in translation and explanation may have influenced the low incidence of phantom pain and high incidence of stump pain. In the bilateral amputees phantom sensation, phantom pain and telescoping all showed bilateral concordance, whereas stump pain and neuromas did not show concordance. About half the subjects (56%) had lost their limb at the time of injury (primary) while the remainder had an injury, then a subsequent amputation in hospital (secondary). There was no association between the incidence of phantom pain and amputation irrespective of being primary or secondary

Transmission Expansion Planning Considering Energy Storage

In electricity transmission networks, energy storage systems (ESS) provide a means of upgrade deferral by smoothing supply and matching demand. We develop a mixed integer programming (MIP) extension to the transmission network expansion planning (TEP) problem that considers the installation and operation of ESS as well as additional circuits. The model is demonstrated on the well known Garver's 6-bus and IEEE 25-bus test circuits for two 24 hour operating scenarios; a short peak, and a long peak. We show optimal location and capacity of storage is sensitive not only to cost, but also variability of demand in the network

The Impact of Institutional Differences on Derivatives Usage

This paper examines the influence of institutional differences on risk management practices in the US andthe Netherlands. This comparison is interesting because the Dutch firms' institutional setting differs fromthe US setting with respect to shareholder orientation, international trade, disclosure regulation, andreliance on financial markets. In contrast with previous comparisons, we apply a matching and weightingstrategy that corrects for differences over industry and size classes across the Dutch and US samples.After these corrections, the remaining results can be attributed more directly to institutional differences.We find that due to the greater openness of the Netherlands, Dutch firms hedge more financialrisk, especially more currency risk, than US firms. Dutch firms, however, show a lower level of concernover derivatives usage, which is consistent with having less active minority shareholders and less strictdisclosure requirements than the US has. Dutch firms focus le ss on stabilizing accounting earnings withderivatives than US firms, which is likely attributable to the strong shareholder orientation in the USversus the stakeholder orientation in the Netherlands. Whereas Dutch firms tend to rely almostexclusively on OTC-transactions, US firms use exchange-traded derivatives and more counter-parties.This results in US firms imposing stricter requirements on counter-party rating for derivativestransactions. This distinction can be attributed to the differences in the financial environments betweenthe US and the Netherlands. These, and other results, strongly suggest that institutional differencesbetween the US and the Netherlands have an important impact on risk management practices andderivatives use across US and Dutch firms.hedging;risk management;derivatives;international finance

A Firm-Specific Analysis of the Exchange-Rate Exposure of Dutch Firms

We examine the relationship between exchange-rate changes and stockreturns for a sample of Dutch firms over 1994-1998. We find that over50% of the firms are significantly exposed to exchange-rate risk.Furthermore, all firms with significant exchange-rate exposure benefitfrom a depreciation of the Dutch guilder relative to a trade-weightedcurrency index. This result confirms that firms in open economies,such as the Netherlands, exhibit significant exchange-rate exposure.We collect unique information on the most relevant individualcurrencies for each firm with respect to their influence on firmvalue. Our results indicate that the use of a trade-weighted currencyindex and the use of individual exchange rates are complements. Wealso measure the determinants of exchange-rate exposure. As expected,we find that firm size and the foreign sales ratio are significantlyand positively related to exchange-rate exposure. In contrast with ourhypothesis, off-balance hedging using derivatives has no significanteffects. Finally, in line with theory, we find that exposure issignificantly reduced through on-balance sheet hedging, i.e. throughforeign loans and by producing in factories abroad.risk management;The Netherlands;foreign exchange rates;international finance;exposure measurement

The Impact of Institutional Differences on Derivatives Usage: A Comparative Study of US and Dutch Firms

This paper tests the influence of institutional differences on risk management practices.Several survey studies have investigated derivatives usage for risk management purposes in the US (see, among others, Bodnar, Hayt, Marston and Smithson, 1995 and Bodnar, Hayt and Marston, 1996, 1998).In this paper, we compare derivative practices of US and Dutch firms.This comparison is interesting because the institutional setting for Dutch firms differs from the US setting with respect to shareholder orientation, international trade, disclosure regulation, and the reliance on financial markets.In a number of survey studies additional countries have been studied, such as New Zealand (Berkman, Bradbury and Magan, 1997), Sweden (Alkebäck and Hagelin, 1999) and Germany (Bodnar and Gebhardt, 1999).In contrast with these papers, we facilitate a comparison by applying a matching and a weighting strategy, which corrects for different distributions over industry and size classes in the Dutch and US samples.After these corrections, the remaining results can be attributed to institutional differences.We find that Dutch firms hedge more financial risk. Because of the greater openness of the Netherlands, Dutch firms experience far more foreign exchange exposure and hedge more currency risk.US firms have more concerns regarding derivative usage, which may be linked to the stricter disclosure requirements in the US.US firms also focus more on accounting earnings, which may be attributable to the shareholder orientation in the US versus the stakeholder orientation in the Netherlands.Whereas Dutch firms tend to rely on OTC-transactions, US firms use exchange-traded derivatives and therefore require a higher counter party rating for derivatives transactions. This distinction can be accredited to the differences in the financial environments between the US and the Netherlands.The aforementioned results indicate that institutional differences between the US and the Netherlands have a significant effect on the risk management practices and derivatives use of US and Dutch firms.risk management;hedging;derivatives

Infective Hepatitis and Associated Maladies: Being an Answer to "An Appeal" as Made by W. N. Pickles M. D. in His "Epidemiology in Country Practice" (Bristol 1939)

Abstract Not Provided