Picosecond fluorescence microscopy for measuring chlorophyll and porphyrin components in conifers and cultured cells.

A synchroscan streak camera was adapted to a microscopic system for fluorescence lifetime measurements. By using this device together with a synchronously pumped dye laser system, a time resolution of 40 ps was attained. Recent applications of this technique include the fluorometric detection of chlorophyll from microscopic parts of spruce needles to measure defects within the photosynthetic system after exposition to environmental pollutants or their photooxidants and fungal infection. It was found that after a combination of continuously high ozone concentration and infection by Rhizosphaera Kalkhoffii, the relative fluorescence intensity of a chlorophyll component with a decay time of 550 ps decreased significantly, whereas a component decaying with 110 ps remained almost constant. This indicates a selective inhibition within the photosystem II. In addition, fluoresence lifetimes of hematoporphyrin derivative - a tumor-selective photosensitizer used for diagnosis and photodynamic therapy of cancer - were measured in the picosecond time range. In comparison with previous nanosecond measurements, a new fluorescent component withh a lifetime of 90 ps was detected from Hpd solutions. This component may be attributed to a dimeric or aggregated species which is monomerized when taken up by malignant or non-malignant cells

Investigation on the Static Fatigue Mechanism and Effect of Specimen Thickness on the Static Fatigue Lifetime in WC–Co Cemented Carbides

The static fatigue mechanism and effect of specimen thickness on static fatigue lifetime for four WC–Co cemented carbides were studied with different binder contents and carbide grain sizes. Static fatigue tests under three-point bend loading were conducted on different sized specimens. The fracture surfaces of rupture specimens were examined by scanning electron microscopy to investigate the static fatigue micromechanisms.Досліджено механізм статичної втоми і вплив товщини зразка на термін служби при статичній втомі для чотирьох твердих сплавів WC–Co з різним вмістом зв’язки і розміром зерен. Випробування на статичну втому при навантаженні за схемою триточкового вигину було проведено на зразках різних розмірів. Поверхні зламів зруйнованих зразків було вивчено c допомогою скануючої електронної мікроскопії з метою дослідження мікромеханізму статичної втоми.Исследованы механизм статической усталости и влияние толщины образца на срок службы при статической усталости для четырех твердых сплавов WC–Co с различным содержанием связующего и размером зерен. Испытания на статическую усталость при нагрузке по схеме трехточечного изгиба были проведены на образцах различных размеров. Поверхности изломов разрушенных образцов были изучены c помощью сканирующей электронной микроскопии с целью исследования микромеханизмов статической усталости