Narrow Results

Antimirov and Mosses proposed a rewrite system for deciding the equivalence of two (extended) regular expressions. They argued that this method could lead to a better average-case algorithm than those based on the comparison of the equivalent minimal deterministic finite automata. In this paper we present a functional approach to that method, prove its correctness, and give some experimental comparative results. Besides an improved functional version of Antimirov and Mosses's algorithm, we present an alternative one using partial derivatives. Our preliminary results lead to the conclusion that, indeed, these methods are feasible and, most of the time, faster than the classical methods.

Regular expressions are often ambiguous. We present a novel method based on Brzozowski’s derivatives to aid the user in diagnosing ambiguous regular expressions. We introduce a derivative-based finite state transducer to generate parse trees and minimal counter-examples. The transducer can be easily customized to either follow the POSIX or Greedy disambiguation policy and based on a finite set of examples it is possible to examine if there are any differences between POSIX and Greedy.

For a regular language $L$, let $\mathrm{\text{Var}}(L)$ be the minimal number of nonterminals necessary to generate $L$ by right linear grammars. Moreover, for natural numbers $k_1,k_2,\dots ,k_n$ and an $n$-ary regularity preserving operation $f$, let the range $g_f^{\mathrm{\text{Var}}}(k_1,k_2,\dots ,k_n)$ be the set of all numbers $k$ such that there are regular languages $L_1,L_2,\dots ,L_n$ with $\mathrm{\text{Var}}(L_i)=k_i$ for $1\le i\le n$ and $\mathrm{\text{Var}}(f(L_1,L_2,\dots ,L_n))=k$. We show that, for the circular shift operation $\mathrm{\text{Circ}}$, $g_{\mathrm{\text{Circ}}}^{\mathrm{\text{Var}}}(n)$ is infinite for all $n$, and we completely determine the set $g_{\mathrm{\text{Circ}}}^{\mathrm{\text{Var}}}(2)$. Moreover, we give a precise range for the left right quotient and a partial result for the left quotient. Furthermore, we add some values to the range for the operation intersection which improves the result of [2].

We study transverse projective structures of foliations and construct an invariant, which is a homomorphism from a foliated cohomology to the ordinary one. It is shown that the infinitesimal derivatives of the Godbillon–Vey class and the Bott class are determined by the invariant. As a corollary, a rigidity theorem for the Godbillon–Vey class and the Bott class is shown.

Nigella sativa (N. sativa) seed has been an important nutritional flavoring agent and natural remedy for many ailments for centuries in ancient systems of medicine, e.g. Unani, Ayurveda, Chinese and Arabic Medicines. Many active components have been isolated from N. sativa, including thymoquinone, thymohydroquinone, dithymoquinone, thymol, carvacrol, nigellimine-N-oxide, nigellicine, nigellidine and alpha-hederin. In addition, quite a few pharmacological effects of N. sativa seed, its oil, various extracts and active components have been identified to include immune stimulation, anti-inflammation, hypoglycemic, antihypertensive, antiasthmatic, antimicrobial, antiparasitic, antioxidant and anticancer effects. Only a few authors have reviewed the medicinal properties of N. sativa and given some description of the anticancer effects. A literature search has revealed that a lot more studies have been recently carried out related to the anticancer activities of N. sativa and some of its active compounds, such as thymoquinone and alpha-hederin. Acute and chronic toxicity studies have recently confirmed the safety of N. sativa oil and its most abundant active component, thymoquinone, particularly when given orally. The present work is aimed at summarizing the extremely valuable work done by various investigators on the effects of N. sativa seed, its extracts and active principles against cancer. Those related to the underlying mechanism of action, derivatives of thymoquinone, nano thymoquinone and combinations of thymoquinone with the currently used cytotoxic drugs are of particular interest. We hope this review will encourage interested researchers to conduct further preclinical and clinical studies to evaluate the anticancer activities of N. sativa, its active constituents and their derivatives.

Ginger is a commonly used spice and herbal medicine worldwide. Besides its extensive use as a condiment, ginger has been used in traditional Chinese medicine for the management of various medical conditions. In recent years, ginger has received wide attention due to its observed antiemetic and anticancer activities. This paper reviews the potential role of ginger and its active constituents in cancer chemoprevention. The phytochemistry, bioactivity, and molecular targets of ginger constituents, especially 6-shogaol, are discussed. The content of 6-shogaol is very low in fresh ginger, but significantly higher after steaming. With reported anti-cancer activities, 6-shogaol can be served as a lead compound for new drug discovery. The lead compound derivative synthesis, bioactivity evaluation, and computational docking provide a promising opportunity to identify novel anticancer compounds originating from ginger.

The author shares his theory on market creation and evolution from his perspective as an academic and a practitioner who has been involved in financial innovation for five decades. Rather than being spontaneously created, markets appear to follow a clear set of steps (the “seven-stage” process) from inception to maturity. It is critical that the benefits from transacting are greater than the costs of establishing the market — otherwise the evolution does not occur. Historical examples of the process outlined by the author can be found in commodity, equity, fixed income and environmental markets. The author provides observations and lessons that his evolutionary framework shares with financial inventive activity in new and existing products in our rapidly evolving digital world. Recent digital innovations such as the blockchain have evolved in a framework that did not require a legislative or regulatory framework (or what the author calls a “permissionless” environment). A properly designed regulatory environment can be permissionless regarding inventive activity (withness the Commodity Futures Trading Commission in the United States). A permissionless environment has historical precedent in other “analog” innovations such as wheat trading in the 19th century or financial futures in the mid-1970s. Following the seven-stage process, those innovations arose from structural changes or latent economic demands. Their standards and infrastructure were only much later understood and adopted by the regulators. Given that, the author suggests that since changes now occur at hyper speed, the implications for the future shape of derivatives markets are likely to be profound.

Two classical non-deterministic automata recognize the language denoted by a regular expression: the position automaton which deduces from the position sets defined by Glushkov and McNaughton–Yamada, and the equation automaton which can be computed via Mirkin's prebases or Antimirov's partial derivatives. Let |E| be the size of the expression and ‖E‖ be its alphabetic width, i.e. the number of symbol occurrences. The number of states in the equation automaton is less than or equal to the number of states in the position automaton, which is equal to ‖E‖+1. On the other hand, the worst-case time complexity of Antimirov algorithm is O(‖E‖³· |E|²), while it is only O(‖E‖·|E|) for the most efficient implementations yielding the position automaton (Brüggemann–Klein, Chang and Paige, Champarnaud et al.). We present an O(|E|²) space and time algorithm to compute the equation automaton. It is based on the notion of canonical derivative which makes it possible to efficiently handle sets of word derivatives. By the way, canonical derivatives also lead to a new O(|E|²) space and time algorithm to construct the position automaton.

We develop a recombining tree method for pricing of options by using a general two-factor stochastic-variance (SV) diffusion model for asset price dynamics. We show that it is possible to construct a riskless hedge by including additional short-term options in the hedging portfolio. This procedure gives us Partial Differential Equation (PDE) that can be solved by using standard numerical techniques giving us a unique option's price. We show that the option's price does not depend on the long run volatility forecast but only on the parameters of the model, which are related to the volatility of variance. We show one particular transformation of PDE to the Finite Difference Equation (FDE) that leads to the three-dimensional lattice method similar to the standard binomial-tree method. Our tree grows in the price-variance space and similarly to the binomial-tree, the coefficients of the FDE can be interpreted as risk neutral probabilities for jumping between the tree nodes. By investigating an error accumulation in the tree we found the stability criterion and the method that can be applied in order to achieve a stabile procedure. Our option pricing method can be used for European and American options and various payoffs. Since the procedure converges quickly and can be easily implemented, we believe that it could be useful for practitioners. The SV model we used here was shown earlier to be a diffusion limit of various GARCH-type models giving the possibility of using parameters obtained in the discrete-time GARCH framework as an input for our option pricing method.

This study investigates the empirical relationship between the use of derivatives by Korean banks and risk. In doing so, we employ two alternative measures of proxy for firm risk: systematic risk and ex ante earnings volatility.

Contrary to the general concerns about the risk-increasing role of the use of derivative products, our results indicate that banks' derivatives are, on average, associated with two measures of risk in negative ways. The evidence is consistent with the conjectures that derivative use reduces noise related to exogenous factors and hence decreases firm risk. This suggests that equity market participants, on average, perceive derivative activities by banks as a sign of banks' efforts to reduce risk.

The main purpose of this paper is to examine the impact that the introduction of exchange traded derivative warrants has on the underlying securities' price, volume and volatility in the Australian market. The impact that derivative trading has on the underlying security is essential to our understanding of security market behaviour and important in the fields of market efficiency and pricing of derivatives. The major findings of significant negative abnormal returns, reduction in skewness, no change in beta and small changes in variance are consistent with recent research findings in the US, UK and Hong Kong. However, the findings of derivative warrant listing resulting in decreased trading volume is in contrast with most prior research in the field. The results of this research, showing a negative price impact, decreased volume and no change in risk, and other recent empirical findings such as Mayhew and Mihov (2000) or Faff and Hillier (2003), indicate a requirement for further development of the theoretical frameworks.

We examine how information asymmetry affects a firm's incentive to hedge versus speculate by using foreign currency derivatives. We find a quadratic relation between asymmetric information and a firm's risk management activities. In particular, we find that the firms facing medium level of information asymmetry are more likely to hedge, while firms with very high and low levels of asymmetric information tend to speculate. Moreover, we find that our results hold primary for firms operating in highly competitive industries.

The first motivation of the creation of derivatives is hedging risk but unfortunately this motivation has changed over the decades since more conventional contracts are used for speculation. The purpose of this study is to use derivatives solely for hedging while respecting principles of profit and risk sharing. According to previous work about the pricing of Waad Bil Mourabaha and using the conventional expression of the contingent premium option, we will propose a model of Participating CPO.

This work aims to inspect the common debate about the implication of derivative instruments in amplifying the last financial crisis. To reach this goal, the study chooses a sample of banks entirely from emerging countries — over the whole period 2003–2011 — in which we examine the impact of derivatives simultaneously on performance, risk and stability during the ordinary period “the pre-crisis period”, 2003–2006, and the unstable period “the crisis and post crisis period”, 2007–2011. The regressions are estimated by generalized methods of moments (GMM) as developed by Blundell and Bond (1998). The major conclusion reveals that only swaps can be considered as implicated in the intensification of the last financial crisis. Therefore, the rest of derivatives instruments cannot be responsible in the amplification of the recent financial crisis. Indeed, the widespread idea accusing all derivatives to be in part responsible of the intensification of the last financial crisis should be revised.

This study examines derivative practices of Australian and Canadian firms from 2009 to 2013 in a post-global financial crisis environment. Our results show significant differences in the level of derivative usage between both countries, in contrast to earlier hedging studies. We also observe that Canadian firms have a higher propensity to use financial derivatives. We find similarities in derivative usage for firms operating in the industrials, materials, consumer discretionary, and healthcare industries. However, corporate derivative practices seem to be significantly different for energy and IT firms during the sample period.

We introduced a new method to compute the European Call (and Put) Option price under the assumption of multifractional Brownian motion (mBm). The reason why we need a procedure for estimating the Option price is due to the absence of a closed formula for this process. To compute the Option price, we first simulated the logarithmic price under mBm and, by using a discount factor, we computed the option’s pay-off. Then, we fitted the best probability distribution associated to the discounted pay-off, computing the European Call Option price as its average.

Derivatives have been blamed in recent years for many financial disasters and there is evidence that disclosure influences hedging activity and corporate value. Nevertheless, standards for the mandatory disclosure of derivatives usage have been very controversial. This paper examines the nature and determinants of voluntary disclosures of currency derivatives usage by large industrial firms under SFAS 107 and has implications for the new derivatives disclosures under SFAS 133. This study documents that, consistent with higher disclosure levels being associated with lower cost of capital and higher shareholder value, firms with higher quality voluntary disclosures have higher market/book value ratios. However, consistent with agency, political, and disclosure cost arguments, industry leaders and firms with higher executive compensation in the form of stock options are more likely to have poor voluntary disclosure. In addition, we do not find any evidence indicating firms with more exposure to currency risk or firms with higher levels of currency derivatives usage provide increased disclosure of derivatives activity.

Four possible hedge accounting treatments for a foreign currency forward contract used to hedge a purchase of equipment are illustrated. In addition to journal entries illustrating the accounting, the pros and cons of the alternative treatments are discussed.

This paper investigates the effects of SFAS 133 on earnings volatility, earnings predictability, and equity volatility in bank holding companies (BHCs). In contrast to large BHCs' assertion prior to the adoption of SFAS 133, the three income-affecting portions (i.e. hedge ineffectiveness gains/losses, gains/losses excluded in the assessment of effectiveness, and effects from canceled forecasted transactions once designated as cash flow hedge) did not increase earnings volatility in the top 30 BHCs for the first 12 quarters after adoption. Also, the three income-affecting portions did not deteriorate analysts' forecast performance. In addition, there is no evidence that volatility of stockholders' equity significantly increases due to SFAS 133. Further investigation of notes to financial statements reveals that some BHCs adjusted their usage of derivatives prior to SFAS 133 to mitigate the impact of SFAS 133 on earnings volatility.

Managers use derivatives to reduce cash flow volatility and achieve earnings smoothing. In 1998, FASB issued SFAS No. 133, under which firms are no longer allowed to simultaneously record all offsetting gains and losses on the items being hedged. Thus, critics argued that this treatment could potentially induce volatility in earnings. The critics also argued that SFAS No. 133 would deter the use of derivatives. Consequently, cash flows were expected to become more volatile, which would also lead to increased volatility in earnings. Based on a sample of Fortune 500 firms, the current study documents that: (1) derivative usage did not significantly decline following the implementation of SFAS No. 133, and (2) derivative users' cash flow volatility did not increase. Although derivative users' earnings volatility did increase following the implementation of SFAS No. 133, the evidence suggests that this increase may have been caused by factors other than the new standard.