Constructions of almost difference sets from finite fields

Almost difference sets are an interesting subject of combinatorics, and have applications in many areas of engineering such as CDMA communications, error correcting codes and cryptography. The objective of this paper is to present some new constructions of almost difference sets, together with several results on the equivalence relation.     

Maximal difference matrices of order q

Recently, A. B. Evans proved the following Theorem: There is a maximal set of (p ? 3)/2 [(resp. (p ? 1)/2] mutually orthogonal Latin squares of order p if p is a prime p ≡ 3 mod 4 (resp. p ≡ 1 mod 4). In this article I will give a slightly different proof using more geometric arguments and results of Rédei. Further, I discuss possible generalizations of Evans' Theorem to the case of Latin squares whose order is a prime power. © 1993 John Wiley & Sons, Inc.     

Grüneisen parameter of cerium compounds with unstable 4f shells

We give experimental results of magnetic susceptibility, thermal expansion and elastic constant measurements for CeSn₃ and CePd₃. We interpret these results with a phenomenological scaling function for the free energy and we include a brief discussion of CeAl₃. The coupling between the electronic system and the lattice can be described by an electronic Grüneisen parameter Ω_g associated with the unstable 4f system which turns out to become a system specific constant far below the fluctuation temperatureT ₀. The coupling parameter T₀Ω_g is an order of magnitude larger than the coupling constant for stable valentRE systems extracted from crystal field effects. A generalization to include magnetic field dependent effects is also given.     

Logarithmic mean oscillation on the polydisc,endpoint results for multi-parameter paraproducts,and commutators on BMO

We study boundedness properties of a class ofmultiparameter paraproducts on the dual space of the dyadic Hardy space H _d ¹ (T ^N ), the dyadic product BMO space BMO ^d (T ^N ). For this, we introduce a notion of logarithmic mean oscillation on the polydisc. We also obtain a result on the boundedness of iterated commutators on BMO [0, 1] ^N ).     

Determination of Glycerol in Biodiesel Using a Nickel(II) Oxyhydroxide Chemically Modified Electrode by Cyclic Voltammetry

A glassy carbon electrode chemically modified with nickel oxyhydroxide from a nickel hexacyanoferrate (NiHCF) film was used to determine glycerol in biodiesel by cyclic voltammetry. The modified electrode exhibited a linear response to glycerol concentration in the range from 0.05 to 0.35 mmol L^?1, and a detection limit of 0.030 mmol L^?1. The glycerol concentration found in the biodiesel sample was 0.156 mmol L^?1. The method developed in this study showed a recovery of (100.3±5.0)%.     

DNA Intercalation in Neutral Multilamellar Membranes: Experiments and Theory

We report both an experimental and a theoretical work on the effect of confinement on a biological polymer (DNA) incorporated to multilamellar phase. We can see that even when no electrostatic interaction are involved this semi-flexible polymer can be incorporated in between the membranes. X-ray provides experimental evidence for the existence of a mixed DNA/Phospholipid structure. The nature of the DNA ordering is briefly described. A theoretical model is developed to describe the phase diagram. We emphasize the role of the isotropic/nematic transition of the DNA molecules to explain the ability to confine DNA in membranes.     

CCZ and EA equivalence between mappings over finite Abelian groups

CCZ- and EA-equivalence, which are originally defined for vectorial Boolean functions, has been extended to mappings between finite abelian groups G and H. We obtain an extension theorem for CCZ-equivalent but not EA-equivalent mappings. Recent results in [2] are improved and generalized.     

Hadamard and Conference Matrices

We discuss new constructions of Hadamard and conference matrices using relative difference sets. We present the first example of a relative -difference set where n – 1 is not a prime power.     

Correlations between the orientation of magnetic recording media determined by Mössbauer Spectroscopy and magnetic methods

The orientation of the easy magnetization axis of magnetic particles is a key parameter of the recording performance of magnetic recording media. Usually the orientation is measured by magnetic methods, but the applicability of the Mössbauer Spectroscopy has also been shown in the past. We show up and discuss the correlations between the results obtained by magnetic and Mössbauer measurements for the example of several magnetic tapes. We demonstrate that by a combination of both methods we are even able to estimate the mean canting angles distribution width of the easy axis of magnetization.