In this paper, we discuss statistical families P with the property that if the distribution of a random variable X is in P, then so is the distribution of ZwBi(X, p) for 0%p%1. (Here we take ZwBi(X, p) to mean that given XZx, Z is a draw from the binomial distribution Bi(x, p).) It is said that the family is closed under binomial subsampling. We characterize such families in terms of probabilit...

Here we model the price of a stock in discrete time by a Markov chain of the recursive form Sn+1 = SnYn+1, n ≥ 0, where the {Yi} are iid with distribution P (Y = u) = p, P (Y = d) = 1 − p. Here 0 < d < 1 + r < u are constants with r the risk-free interest rate ((1 + r)x is the payoff you would receive one unit of time later if you bought $x worth of the risk-free asset (a bond for example, or p...

Financial derivatives are contracts concerning rights and obligations to engage in future transactions on some underlying financial instrument. A major concern in financial markets is to compute an expected value of such contracts as a basis for trading decisions. The Cox, Ross and Rubinstein (CRR) binomial tree model is a popular discrete approach to such computations, which requires time quad...

There are many options available to savvy searchers to help focus topical searches. These include limiting the search to one or more specific fields, such as title, descriptor or abstract in fulltext databases to eliminate items where the search term(s) occur only in the full-text, often just mentioned in passing. This article looks at systems that have a value-added information element that sh...

Patients with hematologic malignancies as well as allogeneic hematopoietic stem cell transplantation (HSCT) patients are at high risk for invasive aspergillosis. Here, we report a culture- and autopsy-proven fatal invasive aspergillosis in an allogeneic HSTC patient which he developed despite posaconazole prophylaxis. The agent was determined to be an azole-resistant Aspergillus fumigatus strai...

The underlying principles of photovoltaic energy conversion are brie&y reviewed, with particular reference to solar application. Although most photovoltaic converters to date have been based on semiconductor p–n junctions, more general structures and materials are feasible. The fundamental requirements for photovoltaic conversion are discussed, as is a generic approach for analysing the limitin...

Idiopathic thrombocytopenic purpura in children usually a self limiting disorder. It may follow a viral infection or immunisation and is caused by an inappropriate response of the immune system. About 20-30% of children will fail to remit over six months (chronic idiopathic thrombocytopenic purpura). This is more likely in older children, especially girls. The disease is reviewed with reference...