A Unique Nickel System having Versatile Catalytic Activity of Biological Significance

A new dinuclear nickel(II) complex, [Ni-2(LH2)(H2O)(2)(OH)(NO3)](NO3)(3) (1), of an "end-off" compartmental ligand 2,6-bis(N-ethylpiperazine-iminomethyl)-4-methyl-phenolato, has been synthesized and structurally characterized. The X-ray single crystal structure analysis shows that the piperazine moieties assume the expected chair conformation and are protonated. The complex 1 exhibits versatile catalytic activities of biological significance, viz. catecholase, phosphatase, and DNA cleavage activities, etc. The catecholase activity of the complex observed is very dependent on the nature of the solvent. In acetonitrile medium, the complex is inactive to exhibit catecholase activity. On the other hand, in methanol, it catalyzes not only the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very difficult to oxidize, under aerobic conditions. UV vis spectroscopic investigation shows that TCC oxidation proceeds through the formation of an intermediate. The intermediate has been characterized by an electron spray ionizaton-mass spectrometry study, which suggests a bidentate rather than a monodentate mode of TCC coordination in that intermediate, and this proposition have been verified by density functional theory calculation. The complex also exhibits phosphatase (with substrate p-nitrophenylphosphate) and DNA cleavage activities. The DNA cleavage activity exhibited by complex 1 most probably proceeds through a hydroxyl radical pathway. The bioactivity study suggests the possible applications of complex 1 as a site specific recognition of DNA and/or as an anticancer agent.

Lapset, media ja symbolinen vuorovaikutus : Suomalaisten, englantilaisten ja saksalaisten lasten mediasuhteen tarkastelua

Tämän hetken mediaympäristölle on ominaista intensiivisyys ja jatkuva läsnäolo. Medialla on merkittävä rooli myös pienten lasten jokapäiväisessä elämässä, sillä he aloittavat median säännöllisen seuraamisen keskimäärin kolmen vuoden iässä. Mediasisällöt, mediavälineet ja mediaan liittyvät sosiaaliset suhteet muodostavatkin lapsille mediaympäristön, jossa lapset rakentavat identiteettejään, oppivat sosiaalista kanssakäymistä ja kehittävät näkemyksiään yhteiskunnasta ja kulttuurista. Tutkimuksessa on selvitetty 4-6-vuotiaitten suomalaisten, englantilaisten ja saksalaisten lasten audiovisuaalisen median tulkintaa ja median roolia heidän elämässään. Tutkimuksen tavoitteena on ollut syventää tutkimuksellista tietoa median sosiaalisesta ja kulttuurisesta merkityksestä pienten lasten elämässä ja sitä, miten he tulkitsevat mediasisältöä. Tutkimuksessa lasten mediasuhdetta on tarkasteltu välineellisenä, sosiaalisena, symbolisena ja kulttuurisena tulkintaympäristönä. Edellisten lisäksi tutkimuksessa on arvioitu harvemmin viestinnän tutkimuksessa käytetyn symbolisen interaktionismin teorian tarjoamia mahdollisuuksia lasten mediasuhteen tarkasteluun. Suomessa, Englannissa ja Saksassa kootun kansainvälisen aineiston pohjalta on tarkasteltu myös vertailuryhmien välillä olevia mediaan liittyviä kulttuurisia eroja. Eri vertailumaiden melko samankaltaisesta mediaympäristöstä huolimatta tutkimus antaa viitteitä mediatulkinnoissa olevista kulttuurisista eroista. Media mahdollistaa lapsen erilaistan taitojensa kehittymistä ja voi siten muodostaa heille sosiaalisia, symbolisia ja kulttuurisia resursseja, joilla on merkitystä lapsen kehittymisen kannalta. Lapsen ja median suhde on kaksisuuntainen vuorovaikutussuhde ja mediainformaation tulkinnassa ovat mukana lapsen aiemmat tiedolliset ja sosiaaliset kokemukset. Aktiivisessa mediatulkintasuhteessaan lapsi kehittää sanavarastoaan, havainnointiaan, ajatteluaan ja tunne-elämäänsä. Median käyttö sosiaalisena tapahtumana kehittää osaltaan lapsen sosiaalisia valmiuksia. Siten esimerkiksi perheen median käyttöön liittyvät säännöt ja ohjeet ohjaavat perheen sisäistä toimintaa ja määrittävät lapsen asemaa perheessä. Median sisällöt ja niihin liittyvät erilaiset oheistuotteet toimivat osaltaan lapsen kulttuuristen koodistojen ja luokittelujen muodostajana. Tutkimus osoittaa myös symbolisen interaktionismin teorian tarjoavan varsin poikkitieteellisen tutkimuksellisen viitekehyksen lapsia ja mediaa koskevalle tutkimukselle ja mahdollistaa lasten mediasuhteen tutkimisen ja ymmärtämisen useiden, erilaisten tekijöiden suhteena.

The significance of brittle reaction layers in fusing of dental ceramics to titanium

This thesis comprises four intercomplementary parts that introduce new approaches to brittle reaction layers and mechanical compatibility of metalloceramic joints created when fusing dental ceramics to titanium. Several different methods including atomic layer deposition (ALD), sessile drop contact angle measurements, scanning acoustic microscopy (SAM), three-point bending (TPB, DIN 13 927 / ISO 9693), cross-section microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) were employed. The first part investigates the effects of TiO2 layer structure and thickness on the joint strength of the titanium-metalloceramic system. Samples with all tested TiO2 thicknesses displayed good ceramics adhesion to Ti, and uniform TPB results. The fracture mode was independent of oxide layer thickness and structure. Cracking occurred deeper inside titanium, in the oxygen-rich Ti[O]x solid solution surface layer. During dental ceramics firing TiO2 layers dissociate and joints become brittle with increased dissolution of oxygen into metallic Ti and consequent reduction in the metal plasticity. To accomplish an ideal metalloceramic joint this needs to be resolved. The second part introduces photoinduced superhydrophilicity of TiO2. Test samples with ALD deposited anatase TiO2 films were produced. Samples were irradiated with UV light to induce superhydrophilicity of the surfaces through a cascade leading to increased amount of surface hydroxyl groups. Superhydrophilicity (contact angle ~0˚) was achieved within 2 minutes of UV radiation. Partial recovery of the contact angle was observed during the first 10 minutes after UV exposure. Total recovery was not observed within 24h storage. Photoinduced ultrahydrophilicity can be used to enhance wettability of titanium surfaces, an important factor in dental ceramics veneering processes. The third part addresses interlayers designed to restrain oxygen dissolution into Ti during dental ceramics fusing. The main requirements for an ideal interlayer material are proposed. Based on these criteria and systematic exclusion of possible interlayer materials silver (Ag) interlayers were chosen. TPB results were significantly better in when 5 μm Ag interlayers were used compared to only Al2O3-blasted samples. In samples with these Ag interlayers multiple cracks occurred inside dental ceramics, none inside Ti structure. Ag interlayers of 5 μm on Al2O3-blasted samples can be efficiently used to retard formation of the brittle oxygen-rich Ti[O]x layer, thus enhancing metalloceramic joint integrity. The most brittle component in metalloceramic joints with 5 μm Ag interlayers was bulk dental ceramics instead of Ti[O]x. The fourth part investigates the importance of mechanical interlocking. According to the results, the significance of mechanical interlocking achieved by conventional surface treatments can be questioned as long as the formation of the brittle layers (mainly oxygen-rich Ti[O]x) cannot be sufficiently controlled. In summary in contrast to former impressions of thick titanium oxide layers this thesis clearly demonstrates diffusion of oxygen from sintering atmosphere and SiO2 to Ti structures during dental ceramics firing and the following formation of brittle Ti[O]x solid solution as the most important factors predisposing joints between Ti and SiO2-based dental ceramics to low strength. This among other predisposing factors such as residual stresses created by the coefficient of thermal expansion mismatch between dental ceramics and Ti frameworks can be avoided with Ag interlayers.

Prognostic significance of cyclooxygenase-2 and associated molecules in gastric cancer

Background and aims: Low stage and curative surgery are established factors for improved survival in gastric cancer. However, not all low-stage patients have a good prognosis. Cyclooxygenase-2 (COX-2) is known to associate with reduced survival in several cancers, and has been shown to play an important role in gastric carcinogenesis. Since new and better prognostic markers are needed for gastric cancer, we studied the prognostic significance of COX-2 and of markers that associate with COX-2 expression. We also studied markers reflecting proliferation and apoptosis, and evaluated their association with COX-2. Our purpose was to construct an accurate prognostic model by combining tissue markers and clinicopathogical factors. Materials and methods: Of 342 consecutive patients who underwent surgery for gastric cancer at Meilahti Hospital, Helsinki University Central Hospital, 337 were included in this study. Low stages I to II were represented by 141 (42%) patients, and high stages III to IV by 196 (58%). Curative surgery was performed on 176 (52%) patients. Survival data were obtained from the national registers. Slides from archive tissue blocks were prepared for immunohistochemistry by use of COX-2, human antigen R (HuR), cyclin A, matrix metalloproteinases 2 and 9 (MMP-2, MMP-9), and Ki-67 antibodies. Immunostainings were scored by microscopy, and scores were entered into a database. Associations of tumor markers with clinicopathological factors were calculated, as well as associations with p53, p21, and results of flow cytometry from earlier studies. Survival analysis was performed by the Kaplan-Meier method, and Cox multivariate models were reconstructed. Cell culture experiments were performed to explore the effect of small interfering (si)RNA of HuR on COX-2 expression in a TMK-1 gastric cancer cell line. Results: Overall 5-year survival was 35.1%. Study I showed that COX-2 was an independent prognostic factor, and that the prognostic impact of COX-2 was more pronounced in low-stage patients. Cytoplasmic HuR expression also associated with reduced survival in gastric cancer patients in a non-independent manner. Cell culture experiments showed that HuR can regulate COX-2 expression in TMK-1 cells in vitro, with an association also between COX-2 and HuR tissue expression in a clinical material. In Study II, cyclin A was an independent prognostic factor and was associated with HuR expression in the gastric cancer material. The results of Study III showed that epithelial MMP-2 associated with survival in univariate, but not in multivariate analysis. However, MMP-9 showed no prognostic value. MMP-2 expression was associated with COX-2 expression. In Study IV, the prognostic power of COX-2 was compared with that of all tested markers associated with survival in Studies I to III, as well as with p21, p53, and flow cytometry results. COX-2 and p53 were independent prognostic factors, and COX-2 expression was associated with that of p53 and Ki-67 and also with aneuploidy. Conclusions: COX-2 is an independent prognostic factor in gastric cancer, and its prognostic power emerges especially in low stage cancer. COX-2 is regulated by HuR, and is associated with factors reflecting invasion, proliferation, and apoptosis. In an extended multivariate model, COX-2 retained its position as an independent prognosticator. COX-2 can be considered a promising new prognostic marker in gastric cancer.

The Significance of Gender in the Prevalence, Forms and Perceptions of Workplace Bullying

Workplace bullying has been shown to have severe negative consequences for both the victims and organisations concerned. Thus, the aim of this paper is to further understanding of workplace bullying by in particular exploring the significance of gender in this phenomenon. The focus is on the prevalence, forms and perceptions of bullying, and the extent to which these interactions and perceptions can be understood as gendered. The aim of the paper is twofold: firstly, to describe gender differences in bullying in the male-dominated business world, and, secondly, to explain these differences by discussing how gender is linked to bullying and victimisation. It is argued that the higher prevalence rates reported by women can be seen as the result of an interaction between higher actual exposure rates to negative behaviours, lower perceived possibilities to defend themselves, and less reluctance to classify negative experiences as bullying, which all are mediated by perceptions of power.

A study of symbolic processing and computational aspects in helicopter dynamics

Even research models of helicopter dynamics often lead to a large number of equations of motion with periodic coefficients; and Floquet theory is a widely used mathematical tool for dynamic analysis. Presently, three approaches are used in generating the equations of motion. These are (1) general-purpose symbolic processors such as REDUCE and MACSYMA, (2) a special-purpose symbolic processor, DEHIM (Dynamic Equations for Helicopter Interpretive Models), and (3) completely numerical approaches. In this paper, comparative aspects of the first two purely algebraic approaches are studied by applying REDUCE and DEHIM to the same set of problems. These problems range from a linear model with one degree of freedom to a mildly non-linear multi-bladed rotor model with several degrees of freedom. Further, computational issues in applying Floquet theory are also studied, which refer to (1) the equilibrium solution for periodic forced response together with the transition matrix for perturbations about that response and (2) a small number of eigenvalues and eigenvectors of the unsymmetric transition matrix. The study showed the following: (1) compared to REDUCE, DEHIM is far more portable and economical, but it is also less user-friendly, particularly during learning phases; (2) the problems of finding the periodic response and eigenvalues are well conditioned.

Variable Elimination in Linear Constraints

Gauss and Fourier have together provided us with the essential techniques for symbolic computation with linear arithmetic constraints over the reals and the rationals. These variable elimination techniques for linear constraints have particular significance in the context of constraint logic programming languages that have been developed in recent years. Variable elimination in linear equations (Guassian Elimination) is a fundamental technique in computational linear algebra and is therefore quite familiar to most of us. Elimination in linear inequalities (Fourier Elimination), on the other hand, is intimately related to polyhedral theory and aspects of linear programming that are not quite as familiar. In addition, the high complexity of elimination in inequalities has forces the consideration of intricate specializations of Fourier's original method. The intent of this survey article is to acquaint the reader with these connections and developments. The latter part of the article dwells on the thesis that variable elimination in linear constraints over the reals extends quite naturally to constraints in certain discrete domains.

Male-biased adult sex ratios and their significance for cooperative breeding in dhole, Cuon alpinus, packs

Two free-ranging packs of dholes (Asiatic wild dog, Cuon alpinus) were monitored for a period of 6 yr (Sep. 1990-Sep. 1996) in the Mudumalai sanctuary, southern India. Demographic data on age structure, litter-size, sex ratio and age and sex specific dispersal were collected. Behavioural data on social interactions and reproductive behaviour among pack members were obtained to determine the frequencies of dominant and subordinate behaviours shown by malt: and female pack members and a measure of each male's reproductive access to females. Behaviours displayed by pack members at dens were recorded to determine whether any age- or sex-specific role specialization existed during pup care. Tenures for dominant males and females within the pack were calculated to ascertain the rate of breeding vacancies occurring within packs. Approximate levels of genetic relatedness within packs were determined by studying pedigrees. In most years one study pack had a male-biased adult sex ratio. This was caused by almost twofold higher dispersal of adult females over adult males. A considerable variance existed in the percentage of sub-adults dispersing from the two packs. Differences existed in the frequencies of dominant and subordinate behaviours shown by males. For males, dominance ranks and ranks based on submissive behaviours were not correlated with frequencies of reproductive behaviours. Subordinate males also displayed reproductive behaviours. In packs, dominant males had lower tenures than dominant females indicating that among males breeding vacancies arose more quickly. The litter size was found to be negatively correlated with the age of the breeding female. There were no significant differences across individuals of varying age or sex classes in the display of pup care behaviours. Significant differences did exist among individual adults. Genetic relatedness among packs tended to vary temporally as a consequence of possible mating by subordinate animals and immigration of new males into the pack. In conclusion, it appears that males delay dispersal and cooperate within their natal packs because of the variety of reproductive strategies they could pursue within. A combination of ecological constraints and the difficulties of achieving breeding status within non-natal packs may make early dispersal and independent breeding less beneficial.

Mutagenic significance of proton acidities in methylated guanine and thymine bases and deoxynucleosides: A theoretical study

Proton changes have been advanced as being the key molecular basis for the mutagenecity of alkylated DNA bases and nucleosides, leading to questions as to which protons are involved and whether the protic changes are tautomeric shifts or abstractions. This semiempirical molecular orbital study seeks to clarify the issue by examining the various possibilities open for these protic changes in a number of methylated guanines and thymines and their deoxynucleosides. Proton shifts leading to tautomer formation are not predicted as being thermodynamically favourable in most cases. The most feasible proton abstractions are predicted to involve the Watson-Crick protons in all cases, which corroborates Watson-Crick proton loss as providing the key molecular basis for the induction of point mutations. The calculated proton acidities correlate well with experimental data. The gas-phase deprotonation enthalpies for a number of alkylated nucleosides are found to correlate linearly with the solvent-phase pK(a) values. The theoretically calculated enthalpies in a simulated aqueous solvent phase of the deprotonation reactions of various nucleic acid bases are also found to have good linear correlations with experimental pK(a) values. The consensus of these calculations is that O-6-alkyldeoxyguanosines, and O-2- and O-4-alkyldeoxythymidines would be mutagenic while N-7-alkyldeoxyguanosines would not be mutagenic (as experiment indicates). The untested N-3-methyldeoxyguanosine is predicted to be mutagenic. (C) 1997 Elsevier Science B.V.

Functional Significance of an Evolutionarily Conserved Alanine (GCA) Resume Codon in tmRNA in Escherichia coli

Occasionally, ribosomes stall on mRNAs prior to the completion of the polypeptide chain. In Escherichia coli and other eubacteria, tmRNA-mediated trans-translation is a major mechanism that recycles the stalled ribosomes. The tmRNA possesses a tRNA-like domain and a short mRNA region encoding a short peptide (ANDENYALAA in E. coli) followed by a termination codon. The first amino acid (Ala) of this peptide encoded by the resume codon (GCN) is highly conserved in tmRNAs in different species. However, reasons for the high evolutionary conservation of the resume codon identity have remained unclear. In this study, we show that changing the E. coli tmRNA resume codon to other efficiently translatable codons retains efficient functioning of the tmRNA. However, when the resume codon was replaced with the low-usage codons, its function was adversely affected. Interestingly, expression of tRNAs decoding the low-usage codon from plasmid-borne gene copies restored efficient utilization of tmRNA. We discuss why in E. coli, the GCA (Ala) is one of the best codons and why all codons in the short mRNA of the tmRNA are decoded by the abundant tRNAs.