Water assessment using ultra-weak bioluminescence.

In this paper a method to evaluate the presence of microorganisms of the coliform group in water samples using the ultra-weak bioluminescence (UWB) is proposed. A series of UWB measurements and optical density measurements from cultures of both a set of standard E. coli strain samples, and a set of water samples from a river near Curitiba City in Brazil were performed. All samples were previously incubated at 37°C for 11h in nutritive medium before the temporal UWB emission profiles data were acquired for a period of 24h inside a dark chamber of an especially implemented instrumentation capable of doing photon counting measurements. For the optical density measurements, a spectrophotometer was used to acquire the growth kinetics of those cultures for a period of 13h, and the results compared to the UWB profiles. Periodic time-components analysis of the UWB data from both the set of standard E. coli samples and the set of the river's water samples were performed and compared to each other. The results have shown that the UWB temporal profiles resemble in some way the growth kinetics curve and the periodic time-components analysis is an effective way to discriminate between contaminated and non-contaminated samples, therefore the method may be viable for detecting coliforms in water samples in less time than usual methods.

Measurement of composite shrinkage using a fibre optic Bragg grating sensor.

Fibre Bragg grating is used to determine resin-based composite shrinkage. Two composite resins (Freedom from SDI and Z100 from 3M) were tested to determine the polymerization contraction behaviour. Each sample of resin was prepared with an embedded fibre Bragg grating. A LED activation unit with wavelength from 430 nm to 470 nm (Dabi Atlante) was used for resin polymerization. The wavelength position of the peak in the optical reflection spectra of the sensor was measured. The wavelength shift was related to the shrinkage deformation of the samples. Temperature and strain evolution during the curing phase of the material was monitored. The shrinkage in the longitudinal direction was 0.15 +/- 0.02% for resin Z100 (3M) and 0.06+/-0.01% for Freedom (SDI); two-thirds of shrinkage occurred after the first 50 s of illumination.

Spin relaxation of iron in mixed state hemoproteins.

In hemoproteins the relaxation mechanism of iron is Orbach for high spin (HS) and Raman for low spin (LS). We found that in met-hemoglobin and met-myoglobin, under conditions in which the two spin states coexist, both the HS and the LS states relax to the lattice through Orbach-like processes. Alos, very short (approximately 1 ns) and temperature independent transverse relaxation times T2 were estimated. This may result from the unusual electronic structure of mixed states hemoproteins that allows thermal equilibrium and interconversion of the spin states.

High and low spin state mixture in methemoglobin and metmyoglobin.

The mixture of low and high iron spin states is studied by electron spin resonance in methemoglobin and in metmyoglobin between 6K and 100K. The crystals contain iron (Fe3) exclusively in the high spin state, while powdered samples show a mixture of high and low spin iron. We detected, for the first time, the low spin state in metmyoglobin at low temperatures. The ratio of high to low spin concentrations (k-1) varies exponentially with inverse of temperature in both proteins, only the absolute value is greater in myoglobin. The slope of K-1 depends on the cooling rate and on the temperature range. The results are qualitatively explained assuming a temperature dependent distribution of crystical field around the cristal value, delta c.