Second-order hydroelastic analysis of a floating plate in multidirectional irregular waves

Based on an analysis of second-order hydrodynamic forces induced by coupling of first-order wave potentials, second-order hydroelastic equations are established and solved in the frequency domain. The responses of a very large floating structure in multidirectional irregular waves are studied. The characteristics of the difference and sum frequency coordinates are discussed in detail; peaks can be found at the difference and sum frequencies close to the wet resonant frequencies of each mode. We present and analyze the maximum vertical displacement of different points as well as the time history of the vertical displacements of selected points. The differences of the combined (the summation of the linear and non-linear responses) and linear displacements of the selected points are calculated. Our results demonstrate that non-linear fluid forces influence the total responses of the referenced floating structure.     

The Vitamin D Status Among Tibetans

UVB from the sun and intake from food are the only human sources of vitamin D. Tibet is a unique region for comparisons of these sources: (1) it lies at a low latitude and at a high altitude and has very large annual fluences of UVB; (2) the traditional Tibetan food is poor in vitamin D. Blood samples were taken from 63 persons of different age, with different occupations and staying at different places. UVB doses at these places were measured. The samples were analyzed by a standard radioimmune assay for determination of the serum concentration of 25 hydroxyvitamin D (25(OH)D). The main finding was that among nomads, there seems to be severe vitamin D deficiency (serum levels of 25(OH)D < 30 n m ). We tentatively propose that the low level of 25(OH)D of nomads is related to their clothing and sun exposure habits. For persons of other occupations (students, teachers and farmers) the levels are higher, although a significant fraction of these persons also have lower levels than 75 n m , by many regarded as a limit for insufficiency related to a number of negative health conditions. The annual dose of vitamin D-generating UVB is about five times larger in Lhasa than in Oslo. Despite this, the average vitamin D status seems to be similar, except in the case of nomads. This phenomenon is certainly related to food habits. In conclusion, the 25(OH)D status among nomads in Tibet appears to be alarmingly low. However, for people of other occupations the status is more normal.     

Diamino acid derivatives of PpIX as potential photosensitizers for photodynamic therapy of squamous cell carcinoma and prostate cancer: In vitro studies

Photodynamic therapy (PDT) is an alternative treatment modality involving light activated drugs, called photosensitizers (PSs), to treat cancer and non-cancerous conditions. The search for new compounds which might become effective PSs is the major direction for PDT development. In the present work we have studied the dark toxicity, intracellular localization and photodynamic properties of four potential, water soluble, second generation PSs – PP(Arg)₂, PP(Ser)₂Arg₂, PP(Ala)₂Arg₂, PP(Phe)₂Arg₂, all diamino acid derivatives of protoporphyrin IX. Human prostate cancer (DU-145) and squamous carcinoma (A431) cells were used as experimental model.Among investigated compounds PP(Ser)₂Arg₂ exhibited the lowest dark toxicity and the highest PDT effectiveness towards both cell lines. Fluorescence microscopy revealed the time-dependent changes in intracellular localization of the PS which were related to the phototoxicity. The results show that PP(Ser)₂Arg₂ may be a potential PS for PDT.     

Spectral and thermal studies of 4-(phenyldiazenyl)phenyl 2-furoate as corrosion inhibitor for carbon steel

The azo-ester, namely 4-(phenyldiazenyl)phenyl 2-furoate (PPF) by a coupling reaction between 4-(phenyldiazenyl)phenol and 2-furoyl chloride in the presence of pyridine was obtained. For characterization of this compound UV–Vis, FTIR, and thermal analysis were used. PPF was investigated as corrosion inhibitor for carbon steel in saline waters using potentiodynamic polarization. Morphology of the surface before and after corrosion was examined by optical microscopy. Potentiodynamic polarization shows that the corrosion current densities decrease and values of polarization resistance and inhibition efficiency increase with PPF concentration reaching a maximum of 89.6 %, at 0.1 mmol L^?1.     

Convergence of the Magnus Series

The Magnus series is an infinite series which arises in the study of linear ordinary differential equations. If the series converges, then the matrix exponential of the sum equals the fundamental solution of the differential equation. The question considered in this paper is: When does the series converge? The main result establishes a sufficient condition for convergence, which improves on several earlier results.     

Intracellular localization of sulfonated meso-tetraphenylporphines in a human carcinoma cell line

The intracellular localization of meso-tetraphenylporphines sulfonated to different degrees (TPPSn), in a human cervix carcinoma cell line (NHIK 3025), was studied by fluorescence microscopy and fluorescence spectroscopy. After an 18 h incubation, TPPS4, TPPS2a and TPPS2o were localized in extranuclear granules. Studies of cells stained with both TPPS4, and acridine orange, which is known to fluoresce red in lysosomes, indicated that these granules were lysosomes. In addition, a fraction of the cellbound TPPS4, TPPS2a and TPPS2o seems to be associated with the plasma membrane. Fluorescence quenching studies of cells doublestained with acridine orange and TPPS4 indicated that TPPS4 is also localized in the nucleus and in the extralysosomal cytoplasm. The intracellular location of TPPS1 differed from that of the other TPPSns studied: In 6 out of 9 experiments fluorescing extranuclear granules were found. A diffuse fluorescence extending from the perinuclear area was also observed.     

PRIMARY DNA DAMAGE, HPRT MUTATION AND CELL INACTIVATION PHOTOINDUCED WITH VARIOUS SENSITIZERS IN V79 CELLS

DNA strand breaks and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutants were measured in parallel in photochemically treated (PCT) cells and compared at the same level of cell survival. Chinese hamster fibroblasts (V79 cells) were either incubated with the lipophilic dyes tetra(3—hydroxyphenyl)porphyrin (3THPP) and Photofrin II (PII), the anionic dye meso -tetra(4—sulfonatophenyl)porphine (TPPS₄) or the cationic dye meso -tetra( N -methyl-4-pyridyl)porphine ( p -TMPyPH₂ before light exposure. In the cells, the lipophilic dyes were localized in membranes, including the nuclear membrane, while the hydrophilic dyes were taken up primarily into spots in the cytoplasm. In addition, the hydrophilic TPPS₄ was distributed homogeneously throughout the whole cytoplasm and nucleoplasm. According to the HPRT mutation test, the mutagenicity of light doses survived by 10% of the cells was a factor of six higher in the presence of 3THPP than of PII, whereas for X-rays it was a factor of three higher than for PCT with 3THPP. Light exposure in the presence of the hydrophilic dyes TPPS₄ and p -TMPyPH₂ was not significantly mutagenic. There was no correlation between the induced rates of HPRT mutants and of DNA strand breaks. Thus, TPPS₄ was the most efficient sensitizer with regard to DNA strand breaks when compared at the same level of cell survival, followed by 3THPP, PII and p -TMPyPH₂. Hence, the rate of DNA strand breaks cannot be used to predict the mutagenicity of PCT.     

The photosensitizing effect of the photoproduct of protoporphyrin IX

The photodynamic effect of a photoproduct of protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) was investigated in WiDr cells, a human adenocarcinoma cell line. The fluorescence excitation and emission spectra of PpIX and the photoproduct were measured. After 1, 3 or 5 min exposure of the ALA-incubated cells to 140 mW/cm² light at 635 nm, the photoproduct — the chlorin photoprotoporphyrin (Ppp), had an emission band around 670 nm. The Ppp excitation peak at 670 nm is well separated from the PpIX peak at 635 nm. The outcome of photodynamic therapy (PDT) was determined by measuring intracellular fluorescence intensity of propidium iodide (PI) 2 h following PDT and methylene blue (MB) staining 24 h following PDT. A significant increase in the fluorescence intensity of PI was noted when the ALA-loaded cells were exposed to 670 nm light after exposure to 635 nm, indicating enhanced cell membrane inactivation induced by the photodynamic action of the photoproduct. However, the fraction of the cells that survived following the same treatment as measured by MB staining was not significantly affected based on an analysis of variance. The fluorescence of PpIX decayed significantly during 635 nm light exposure. Exposure to light at 670 nm does not lead to any photodegradation of PpIX. The fluorescence of Ppp was bleached during 670 nm light exposure. Exposure of Ppp at 670 nm gives no PpIX back. Thus, the phototransformation of PpIX to Ppp is probably not a reversible process.     

Photobleaching of radiation induced trapped electrons in neutral and alkaline glasses. Hydrogen atom formation

Photomobilization of trapped electrons in 7 M NaClO₄- and 9 M NaOH-glass gives rise to trapped hydrogen atoms. This is probably due to the reaction e^?_m + H₂O → H + OH^?. Experiments with an electron scavenger indicate that electrons are not precursors to radiolytically produced hydrogen atoms. It seems that the mobile electrons produced during photobleaching are not slowed down to thermal energy before they react to produce hydrogen atoms, since the yield of the latter species is strongly dependent on the wavelength of the bleaching light.