Security and Authentication in the Mobile World

Mobile systems are evolving into data centric, packet switched,multiacess networks. New types of security threats are emerging in thesenew networks. From the user point of view a seamless solution for thesethreats is required. This paper presents a vision of network convergenceand its implications to authentication and authorization solutions.Security requirements are discussed and current authentication solutionsin GSM, UMTS and operator wireless local area networks (OWLAN) areintroduced. All-IP multimedia session security is discussed.Implications of AdHoc network architecture into security requirement arediscussed.     

Occupational Exposure to Pesticides in Finland

Abstract

The annual use of pesticides in Finland counted as ingredients has been around 2000 tons from the seventies. Herbicides, which are mostly used in agriculture, are almost 80% of the total use of pesticides. Amount of workers occupationally exposed to pesticides is about 170000. Farmers are the largest group among exposed persons. Their number is around 50000 but their exposure periods last only for few days every summer. In greenhouses, around 20000, and in forestry, nearly 1500 workers are exposed to pesticides with more regular and longer lasting exposure than that of farmers. In the Finnish Register of Occupational Diseases, 79 cases caused by pesticides were reported during the years 1972-1991. Most of the cases were from greenhouses, agriculture and forestry. Typical symptoms in reports were toxic eczema or acute symptoms. Occupational exposure of workers to pesticides in Finland has been mainly studied by the Kuopio Regional Institute of Occupational Health since 1978. Exposure levels have been evaluated by occupational hygienic measurements and biological monitoring. Field studies done in agriculture, forestry and greenhouses revealed that exposure of the workers in most cases is at low level. Skin contamination is the main factor of exposure. Therefore, the use of personal protective clothing is essential for minimising exposure. Situations, where risk for exposure is high, are the dilution of formulation before spraying, preparation of equipment on fields, and contamination of skin when the work is started immediately after applications on fields and in greenhouses.     

Superharmonic functions are locally renormalized solutions

We show that different notions of solutions to measure data problems involving p-Laplace type operators and nonnegative source measures are locally essentially equivalent. As an application we characterize singular solutions of multidimensional Riccati type partial differential equations.     

Phase separation and crystallinity in proton conducting membranes of styrene grafted and sulfonated poly(vinylidene fluoride)

A series of proton exchange membranes have been prepared by the preirradiation grafting method. Styrene was grafted onto a matrix of poly(vinylidene fluoride) (PVDF) after electron beam irradiation. Part of the samples was crosslinked with divinylbenzene (DVB) or bis(vinylphenyl)ethane (BVPE). Subsequent sulfonation gave membranes grafted with poly(styrene sulfonic acid) and marked PVDF‐g‐PSSA. It was found that the intrinsic crystallinity of the matrix decreased in both the grafting and the sulfonation reaction in all the membranes. The graft penetration and the ion conductivity are influenced strongly by the crosslinker. The ion conductivity is considerably lower in crosslinked membranes than in noncrosslinked ones. Generally, the mechanical strength decreases with crosslinking. The membranes show a regular phase separated structure in which the sulfonated grafts are incorporated in the amorphous parts of the matrix polymer. The phase separated domains are small, of the order of magnitude of 100–250 nm. These were resolved on transmission electron micrographs and on atomic force images but could not be resolved with microprobe Raman spectroscopy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1741–1753, 1999     

Zebra Factorizations in Free Semigroups

Let $S$ be a semigroup of words over an alphabet $A$. Let $\Omega(S)$ consist of those elements $w$ of $S$ for which every prefix and suffix of $w$ belongs to $S$. We show that $\Omega(S)$ is a free semigroup. Moreover, $S$ is called separative if also the complement $S^c = A^+\setminus S$ is a semigroup. There are uncountably many separative semigroups over $A$, if $A$ has at least two letters. We prove that if $S$ is separative, then every word $w \in A^+$ has a unique minimum factorization $w = z_1z_2 \cdots z_n$ with respect to $\Omega(S)$ and $\Omega(S^c)$, where $z_i \in \Omega(S) \cup \Omega(S^c)$ and $n$ is as small as possible.     

Exciplex intermediates in photoinduced electron transfer of porphyrin-fullerene dyads

The photoinduced electron transfer in differently linked zinc porphyrin-fullerene dyads and their free-base porphyrin analogues was studied in polar and nonpolar solvents with femto- to nanosecond absorption and emission spectroscopies. A new intermediate state, different from the locally excited (LE) chromophores and the complete charge-separated (CCS) state, was observed. It was identified as an exciplex. The exciplex preceded the CCS state in polar benzonitrile and the excited singlet state of fullerene in nonpolar toluene. The behavior of the dyads was modeled by using a common kinetic scheme involving equilibria between the exciplex and LE chromophores. The scheme is suitable for all the studied porphyrin-fullerene compounds. The rates of reaction steps depended on the type of linkage between the moieties. The scheme and Marcus theory were applied to calculate electronic couplings for sequential reactions, and consistent results were obtained.     

Lipid membrane formation by vesicle fusion on silicon dioxide surfaces modified with alkyl self-assembled monolayer islands

Using atomic force microscopy, we have investigated the formation of the dipalmitoylphosphatidylcholine (DPPC) membrane by the vesicle fusion method on SiO2 surfaces modified with self-assembled monolayer (SAM) islands of octadecyltrichlorosilane (OTS) with sizes comparable to those of the vesicles. OTS-SAM islands with various sizes and coverages can be constructed on the SiO2 surfaces prepared by thermal oxidation followed by partial hydroxylation in a H2O2/H2SO4 solution. When vesicles are sufficiently smaller than the SiO2 domains, DPPC bilayers and DPPC/OTS layers form on the SiO2 and OTS domains, respectively. However, the adhesion of larger vesicles onto SiO2 is prevented by the OTS islands; therefore only DPPC/OTS layers form without formation of DPPC bilayers on the SiO2 domains. On surfaces with domains on the scale of tens to hundreds of nanometers, the relative size between the hydrophilic domains and the vesicles becomes an important factor in the membrane formation by the fusion of vesicles.     

Comparative study for differentiation of aquatic humic-type organic constituents by capillary zone electrophoresis using polyvinyl alcohol-coated capillary

Capillary zone electrophoresis (CZE) with UV detection (254 nm) was applied to characterize aquatic dissolved humic matter (DHM) from different environmental sources (lake, river and sea waters, in all 15 different samples). A series of separation examples of DHMs using a polyvinyl alcohol (PVA)-coated silica open tubular capillary were carried out in a phosphate buffer (40 mM) as a background electrolyte at neutral acidity (pH 6.8). The separative power of electropherograms was reasonable and the reproducibility was above the mark. Each electropherogram was characteristic of the corresponding humic sample. Special functional fulvic and humic acids or their overall mixtures separated with XAD, DAX and DEAE sorbing solids as well as the original dissolved organic matter (DOM) were nicely differentiated according to their environmental sources. The PVA coating of open tubular silica capillaries seems to be very potential in electrophoretic characterization and separation of different humic solutes at neutral acidities with low sample concentrations thus permitting a workable technique, in a growing series of CZE studies, for better compared results from different studies.     

On-surface and sub-surface oxygen on ideal and reconstructed Cu(1 0 0)

In order to understand the first steps of the Cu(1 0 0) oxidation we performed first principles calculations for on-surface and sub-surface oxygen on this surface. According to our calculations, the adsorption energies for all on-surface site oxygen atoms increase, whereas the energies of the sub-surface atoms decrease with the increasing oxygen coverage. At coverage 1 ML and higher on the reconstructed surface, structures including both on- and sub-surface atoms are energetically more favourable than structures consisting only of on-surface adsorbates. On the ideal (1 0 0) surface this change can be perceived at coverage 0.75 ML.