Potential Use of a Terbium-Transferrin Complex as a Label in an Immunoassay for Gentamicin

A study has been made of the potential use of a terbium - transferrin complex as a non-isotopic label in the immunoassay determination of the antibiotic gentamicin. The fluorescence properties of the complex have been characterised. The labelled gentamicin was formed using a controlled carbodiimide reaction, conditions being chosen to produce a gentamicin-bound complex containing the correct amount of gentamicin for use in a competitive binding assay. Recognition of the gentamicin-bound complex by antisera to gentamicin was verified using a standard radioimmunoassay for gentamicin

Back to basics: historical option pricing revisited

We reconsider the problem of option pricing using historical probability distributions. We first discuss how the risk-minimisation scheme proposed recently is an adequate starting point under the realistic assumption that price increments are uncorrelated (but not necessarily independent) and of arbitrary probability density. We discuss in particular how, in the Gaussian limit, the Black-Scholes results are recovered, including the fact that the average return of the underlying stock disappears from the price (and the hedging strategy). We compare this theory to real option prices and find these reflect in a surprisingly accurate way the subtle statistical features of the underlying asset fluctuations.Comment: 14 pages, 2 .ps figures. Proceedings, to appear in Proc. Roy. So

Black-Scholes option pricing within Ito and Stratonovich conventions

Options financial instruments designed to protect investors from the stock market randomness. In 1973, Fisher Black, Myron Scholes and Robert Merton proposed a very popular option pricing method using stochastic differential equations within the Ito interpretation. Herein, we derive the Black-Scholes equation for the option price using the Stratonovich calculus along with a comprehensive review, aimed to physicists, of the classical option pricing method based on the Ito calculus. We show, as can be expected, that the Black-Scholes equation is independent of the interpretation chosen. We nonetheless point out the many subtleties underlying Black-Scholes option pricing method.Comment: 14 page

Modeling electricity loads in California: a continuous-time approach

In this paper we address the issue of modeling electricity loads and prices with diffusion processes. More specifically, we study models which belong to the class of generalized Ornstein-Uhlenbeck processes. After comparing properties of simulated paths with those of deseasonalized data from the California power market and performing out-of-sample forecasts we conclude that, despite certain advantages, the analyzed continuous-time processes are not adequate models of electricity load and price dynamics.Comment: To be published in Physica A (2001): Proceedings of the NATO ARW on Application of Physics in Economic Modelling, Prague, Feb. 8-10, 200

An investigation of fluorine overvoltage at carbon anodes

PhD ThesisThe high anode overvoltage exhibited by fluorine cells has been variously attributed to bubble overvoltage and to inhibition of the electron transfer process by a layer of insulating carbon fluoride on the surface of the electrode. This thesis presents the results of various experiments which attempt to assess the contribution of the carbon fluoride film to the anode overvoltage in the absence of bubble overvoltage. Fluorine evolution from the molten salt KF.2HF at 85°C was studied at vertical carbon anodes. The techniques employed to study the kinetics and mechanism of this reaction included cyclic voltammetry, steady state potentiostatic polarisation, A.C. impedance, potential pulse and constant current electrolysis. Such measurements indicated that several types of carbon fluoride can be produced on the anode evolving fluorine, depending on the potential of electrolysis. These measurements also show the difficulty in obtaining kinetic parameters for the fluorine evolution reaction. The nature of the fluoride film produced on the carbon anode was investigated using XPS and SIMS analysis of electrodes polarised in the KF.2HF melt at 5V and 9V. These measurements indicated that the film is not one single carbon fluoride but more of a graded nature becoming more heavily fluorinated at higher potentials. The inhibiting effect of the solid film was studied by transfering carbon electrodes, following fluorine evolution in the KF.2HF melt under well' defined conditions, to other electrochemical systems using aqueous or organic electrolytes at room temperature, where electrode kinetic studies were made of redox reactions. Kinetic data were compared with those obtained with unfluorinated carbon surfaces. Observations obtained by the above methods have been related to estimates of the thickness of the carbon fluoride film as determined by measurements of the double layer capacitance in the KF.2HF melt and in other solvent systems. Both capacitance measurements and kinetic studies of redox reactions indicate that the film became progressively thicker as the potential of the fluorine anode was raised. Rates of redox reactions fell by at least two orders of magnitude in the presence of a film formed by polarising the carbon at 6.0V in the KF.2HF melt. Attempts were made to overcome the inhibiting effect of the fluoride films by incorporating transition metals in the carbon anodes. The last section of this thesis explains the manufacture of doped carbon samples and presents results obtained in the KF.2HF melt using such anode materials.SERC, British Nuclear Fuels Plc

Weak randomness completely trounces the security of QKD

In usual security proofs of quantum protocols the adversary (Eve) is expected to have full control over any quantum communication between any communicating parties (Alice and Bob). Eve is also expected to have full access to an authenticated classical channel between Alice and Bob. Unconditional security against any attack by Eve can be proved even in the realistic setting of device and channel imperfection. In this Letter we show that the security of QKD protocols is ruined if one allows Eve to possess a very limited access to the random sources used by Alice. Such knowledge should always be expected in realistic experimental conditions via different side channels

Quantum Sign Permutation Polytopes

Convex polytopes are convex hulls of point sets in the $n$-dimensional space \E^n that generalize 2-dimensional convex polygons and 3-dimensional convex polyhedra. We concentrate on the class of $n$-dimensional polytopes in \E^n called sign permutation polytopes. We characterize sign permutation polytopes before relating their construction to constructions over the space of quantum density matrices. Finally, we consider the problem of state identification and show how sign permutation polytopes may be useful in addressing issues of robustness

The escape problem under stochastic volatility: the Heston model

We solve the escape problem for the Heston random diffusion model. We obtain exact expressions for the survival probability (which ammounts to solving the complete escape problem) as well as for the mean exit time. We also average the volatility in order to work out the problem for the return alone regardless volatility. We look over these results in terms of the dimensionless normal level of volatility --a ratio of the three parameters that appear in the Heston model-- and analyze their form in several assymptotic limits. Thus, for instance, we show that the mean exit time grows quadratically with large spans while for small spans the growth is systematically slower depending on the value of the normal level. We compare our results with those of the Wiener process and show that the assumption of stochastic volatility, in an apparent paradoxical way, increases survival and prolongs the escape time.Comment: 29 pages, 12 figure

2D pattern evolution constrained by complex network dynamics

Complex networks have established themselves along the last years as being particularly suitable and flexible for representing and modeling several complex natural and human-made systems. At the same time in which the structural intricacies of such networks are being revealed and understood, efforts have also been directed at investigating how such connectivity properties define and constrain the dynamics of systems unfolding on such structures. However, lesser attention has been focused on hybrid systems, \textit{i.e.} involving more than one type of network and/or dynamics. Because several real systems present such an organization (\textit{e.g.} the dynamics of a disease coexisting with the dynamics of the immune system), it becomes important to address such hybrid systems. The current paper investigates a specific system involving a diffusive (linear and non-linear) dynamics taking place in a regular network while interacting with a complex network of defensive agents following Erd\"os-R\'enyi and Barab\'asi-Albert graph models, whose nodes can be displaced spatially. More specifically, the complex network is expected to control, and if possible to extinguish, the diffusion of some given unwanted process (\textit{e.g.} fire, oil spilling, pest dissemination, and virus or bacteria reproduction during an infection). Two types of pattern evolution are considered: Fick and Gray-Scott. The nodes of the defensive network then interact with the diffusing patterns and communicate between themselves in order to control the spreading. The main findings include the identification of higher efficiency for the Barab\'asi-Albert control networks.Comment: 18 pages, 32 figures. A working manuscript, comments are welcome

Algorithm for characterizing stochastic local operations and classical communication classes of multiparticle entanglement

It is well known that the classification of pure multiparticle entangled states according to stochastic local operations leads to a natural classification of mixed states in terms of convex sets. We present a simple algorithmic procedure to prove that a quantum state lies within a given convex set. Our algorithm generalizes a recent algorithm for proving separability of quantum states [Barreiro et al., Nat. Phys. 6, 943 (2010)]. We give several examples which show the wide applicability of our approach. We also propose a procedure to determine a vicinity of a given quantum state which still belongs to the considered convex set