background: due to difficulty of obtaining a 24h urine (especially in children), a random urine calcium sample is recommended to detect of hypercalciuria. however, recent studies have shown that the urinary calcium/creatinine ratio varies with age and geographic areas. so, the aim of this study was determining the normal value of urinary calcium to creatinine ratio in healthy adolescent’s child...

We investigated emission from single CdSe nanocrystals in poly methyl methacrylate . A fraction of the nanocrystals exhibited switching between two energy states which had similar total intensities but distinctly different spectra. We found that the characteristic frequency of this spectral shift increased with the pump power. By using the dynamic shift in the spectral position of emission peak...

This paper deals with testing the mean of a log-normal population. We apply a newly developed Computational Approach Test (CAT), which is essentially a parametric bootstrap method. An advantage of the CAT is that it does not require the explicit knowledge of the sampling distribution of the test statistic. The CAT is then compared with three accepted testsCox method, modified Cox method and gen...

Starting point of our work is a previous paper by Flarup, Koiran, and Lyaudet [5]. There the expressive power of certain families of polynomials is investigated. Among other things it is shown that polynomials arising as permanents of bounded tree-width matrices have the same expressiveness as polynomials given via arithmetic formulas. A natural question is how expressive such restricted perman...

A simple nonconstructive argument shows that most CNF formulas with clauses (where is a large enough constant) are not satisfiable. It is an open question whether there is an efficient refutation algorithm that for most formulas with clauses proves that they are not satisfiable. We present a polynomial time algorithm that for most CNF formulas with clauses (where is a large enough constant) fin...

We consider the deficiency and the maximal deficiency "! #$ % of a clauseset (a conjunctive normal form), where is the number of clauses in and is the number of variables. Combining ideas from matching and matroid theory with techniques from the area of resolution refutations, we prove that for clause-sets with '& ( , where ( is considered as a constant, the SAT problem, the minimally unsatisfi...

We introduce and investigate a new type of reductions between counting problems, which we call subtractive reductions. We show that the main counting complexity classes #P, #NP, as well as all higher counting complexity classes # · kP, k 2, are closed under subtractive reductions. We then pursue problems that are complete for these classes via subtractive reductions. We focus on the class #NP (...

A central topic in query learning is to determine which classes of Boolean formulas are e ciently learnable with membership and equivalence queries. We consider the class Rk consisting of conjunctions of k unate DNF formulas. This class generalizes the class of k-clause CNF formulas, and the class of unate DNF formulas, both of which are known to be learnable in polynomial time with membership ...

The consequences of the existence of sparse hard sets for NP have been investigated for nearly 20 years. Many surprising results have been found, e.g. the result of Ogihara and Watanabe that P = NP is implied by the existence of sparse pbtt -hard sets for NP. It is clear that the existence of sparse hard sets for a weak reduction (e.g. pm) implies stronger results than the existence of sparse h...

This article, from an algorithmic point of view, studies the satisfiability problem SAT restricted to a CNF fraction MHF whose members consist of a Horn formula and a 2-CNF part. In general SAT is NP-complete for such formulas. We consider various structurally defined subclasses of MHF, for which SAT can be solved in polynomial time. The instances defined here are required to have a linear, or ...