Observational Aspects of Symmetries of the Neutral B Meson System

We revisit various results, which have been obtained by the BABAR and Belle Collaborations over the last twelve years, concerning symmetry properties of the Hamiltonian, which governs the time evolution and the decay of neutral B mesons.We find that those measurements, which established CP violation in B meson decay, 12 years ago, had as well established T (time-reversal) symmetry violation. They also confirmed CPT symmetry in the decay (T_CPT = 0) and symmetry with respect to time-reversal (epsilon? = 0) and to CPT (delta? = 0) in the B0 ?B0bar oscillation.Comment: Original arguments and conclusions unchanged. Relation to other work explained in more detail. 2 references adde

A Remark on the Principle of Zero Utility

Let u(x) be a utility function, i.e., a function with u′(x)>0, u″(x)<0 for all x. If S is a risk to be insured (a random variable), the premium P = P(x) is obtained as the solution of the equation which is the condition that the premium is fair in terms of utility. It is clear that an affine transformation of u generates the same principle of premium calculation. To avoid this ambiguity, one can standardize the utility function in the sense that for an arbitrarily chosen point y. Alternatively, one can consider the risk aversion which is the same for all affine transformations of a utility function. Given the risk aversion r(x), the standardized utility function can be retrieved from the formula It is easily verified that this expression satisfies (2) and (3). The following lemma states that the greater the risk aversion the greater the premium, a result that does not surpris

Stop-loss a tempo continuo e protezione dinamica di un fondo d'investimento

Nella prima parte del nostro lavoro, il surplus di una compagnia d'assicurazione è modellizzato come un processo di Wiener. Consideriamo un contratto d'assicurazione dinamica di solvibilità. Secondo questo contratto, i pagamenti necessari sono effettutati istantaneamente, in modo che il surplus modificato non divenga mai negativo. Matematicamente, questo corrisponde ad introdurre una barriera riflettente in zero. Otteniamo così un'espressione esplicita per il premio netto di un tale contratto. Nella seconda parte, consideriamo un fondo d'investimento il cui valore unitario è modellizzato da un moto browniano geometrico. Differenti forme di protezione di fondi d'investimento sono esaminate. La più semplice consiste in una garanzia che fornisce istantaneamente i pagamenti necessari, di modo che il valore unitario modificato del fondo non scenda sotto un determinato livello protetto. Esiste un'espressione esplicita per il prezzo di una tale garanzia. Questo risultato può anche essere utilizzato per valutare il prezzo di una garanzia in cui il livello protetto è una funzione esponenziale del tempo. In più, è dimostrato come sintetizzare questa garanzia, costruendo il portafoglio replicante. La garanzia dinamica di fondi d'investimento è paragonata all'opzione di vendita corrispondente, e si è osservato che per delle scadenze corte, il rapporto dei due prezzi è di circa 2. Infine ci interesseremo al prezzo di una protezione più esotica, nella quale il valore unitario garantito in ogni momento è una frazione fissa del valore unitario modificato massimo osservato fino a quel moment

On optimal investiment strategies

Suppose an investor has a fixed decision horizon and an appropriate utility function for measuring his or her utility of wealth. If there are only two investment vehicles, a risky and a risk-free asset, then the optimal investment strategy is such that, at any time, the amount invested in the risky asset must be the product of his or her "current risk tolerance” and the risk premium on the risky asset, divided by the square of the diffusion coefficient of the risky asset. In the case of more than one risky asset, the optimal investment strategy is similar, with the ratios of the amounts invested in the different risky assets being constant over tim

Circuit de commande pour Anti Collision Lamps ACL

Objectif Les ACL sont des ampoules 28V/200W utilisés dans le domaine de l’éclairage professionnel. Habituellement, 8 ampoules sont branchées en série sur le réseau. Suite à ce montage, une commande individuelle de la luminosité n’est pas possible. L’appareil conçu dans ce projet met toutes les ampoules en parallèle sur un bus de tension continue à 28Vdc. La commande individuelle est maintenant possible. Une protection anti-courtcircuit est aussi conçue afin de sécuriser l’installation. Pour alimenter le bus de tension continue, un pont H résonnant est utilisé. Pour diminuer au mieux les pertes de ce système, un redresseur actif est utilisé. Ce dernier fonctionne en utilisant la tension induite d’une self saturable. Résultats L’alimentation du bus de tension continue au travers du redresseur actif n’a pas pu être réalisée car le signal de la self saturable n’est pas assez fiable. La protection anti-court-circuit fonctionne correctement. La lampe fait du bruit lorsque celle est alimentée par des flancs de courant trop brusques à des fréquences audibles. La solution consisterait à l’alimenter à des fréquences élevées.Ziel ACLs sind Lampen 28V/200W, welche im Bereich der professionellen Beleuchtung verwendet werden. Normalerweise sind 8 Lampen in Serie am Netz angeschlossen. Durch diese Anordnung ist eine individuelle Lichtsteuerung nicht möglich. Mit dem in diesem Projekt zu entwickelnden Gerät werden alle Lampen parallel auf einen Spannungsbus von 28Vdc gelegt: Dadurch wird die individuelle Ansteuerung ermöglicht. Zur besseren Sicherheit wird auch eine Kurzschlusssicherheit realisiert. Der Spannungsbus wird mittels einer resonanten H-Brückenschaltung verwirklicht. Resultate Der synchrone Gleichrichter konnte nicht getestet werden da die Steuersignalgenerierung mit Sättigungsdrossel nicht zuverlässig funktioniert. Die Kurzschlusssicherheit funktioniert einwandfrei. Im Betrieb der Lampe entsteht ein störendes Geräusch, weil die Ansteuerung mit steilen Stromflanken sich in hörbaren Frequenzen abspielt. Zur Behebung dieses Geräusches können Speisungen mit höheren Schaltfrequenzen verwendet werden

Peripheral nerve-derived VEGF promotes arterial differentiation via neuropilin 1-mediated positive feedback

In developing limb skin, peripheral nerves are required for arterial differentiation, and guide the pattern of arterial branching. In vitro experiments suggest that nerve-derived VEGF may be important for arteriogenesis, but its role in vivo remains unclear. Using a series of nerve-specific Cre lines, we show that VEGF derived from sensory neurons, motoneurons and/or Schwann cells is required for arteriogenesis in vivo. Arteriogenesis also requires endothelial expression of NRP1, an artery-specific coreceptor for VEGF^(164) that is itself induced by VEGF. Our results provide the first evidence that VEGF is necessary for arteriogenesis from a primitive capillary plexus in vivo, and show that in limb skin the nerve is indeed the principal source of this signal. They also suggest a model in which a `winner-takes-all' competition for VEGF may control arterial differentiation, with the outcome biased by a VEGF^(164)-NRP1 positive-feedback loop. Our results also demonstrate that nerve-vessel alignment is a necessary, but not sufficient, condition for nerve-induced arteriogenesis. Different mechanisms therefore probably underlie these endothelial patterning and differentiation processes

Speed and force of spore ejection in Selaginella martensii

Schneller J., Gerber H. and Zuppiger A. 2008. Speed and force of spore ejection in Selaginella martensii. Bot. Helv. 118: 13 - 20. Spores of the genus Selaginella are discharged through an ejection mechanism caused by the anatomical differentiation of the sporangium. To understand the evolution of these specialised dispersal mechanisms, it is important to know how effective they are, i.e. what distance is reached by the spores, how rapidly they are ejected, and what forces must be developed by the plants to achieve this speed. Here we present a method to determine these important variables. We observed the spore discharge process for Selaginella martensii using a high-speed camera, which allowed us to resolve the movement to 1/1000 s. The mico- and megasporangia opened slowly, separating into two ovoid valves, which subsequently dried and closed in a sudden, quick movement, ejecting the spores. The distances of spore dispersal were determined by placing single shoots of Selaginella on paper in the laboratory. Microspores reached up to 5-6cm from the spore source, while megaspores reached up to 65cm from the source, with a mean flight distance of 21.3cm. Based on the flight trajectories observed on the photographs and the mean weight of a megaspore (1.4μg), we calculated the speed and forces responsible for the ejection mechanism. The speed of the spores at ejection time was 0.6 m/s for microspores, and 4.5 m/s for megaspores. The initial impulse of one megaspore was estimated as 6.3 pNs. A force greater than 7μN is necessary to accelerate the megaspore in less than 1ms to this speed. Our new method to determine the impulse and initial speed of Selaginella spores makes possible more detailed studies about the role and function of biological structures responsible for spore ejectio

Martingale Approach to Pricing Perpetual American Options

The method of Esscher transforms is a tool for valuing options on a stock, if the logarithm of the stock price is governed by a stochastic process with stationary and independent increments. The price of a derivative security is calculated as the expectation, with respect to the risk-neutral Esscher measure, of the discounted payoffs. Applying the optional sampling theorem we derive a simple, yet general formula for the price of a perpetual American put option on a stock whose downward movements are skip-free. Similarly, we obtain a formula for the price of a perpetual American call option on a stock whose upward movements are skip-free. Under the classical assumption that the stock price is a geometric Brownian motion, the general perpetual American contingent claim is analysed, and formulas for the perpetual down-and-out call option and Russian option are obtained. The martingale approach avoids the use of differential equations and provides additional insight. We also explain the relationship between Samuelson's high contact condition and the first order condition for optimalit