Compensation of the inherent wave front curvature in digital holographic coherent microscopy for quantitative phase-contrast imaging

An approach is proposed for removing the wavefront curvature introduced by the microscope imaging objective in digital holography, which otherwise hinders the phase contrast imaging at reconstruction planes. The unwanted curvature is compensated by evaluating a correcting wave front at the hologram plane with no need for knowledge of the optial parameters, focal length of the imaging lens, or distances in the setup. Most importantly it is shown that a correction effect can be obtained at all reconstruction planes. Three different methods have been applied to evaluate the correction wave front and the methods are discussed in detail. The proposed approach is demonstrated by applying digital holography as a method of coherent microscopy for imaging amplitude and phase contrast of microstructures.     

A new implemented version of program MIR (MIR II): analysis and identification of mathematical models in enzyme and transport kinetic studies

The computer program MIR previously described (R. Bianchi, G.M. Hanozet and M. Pilone Simonetta, Comput. Prog. Biomed. 16 (1983) 189) that fits trial rate laws to enzyme and transport steady-state kinetic data by the least-squares method has been enhanced. The new version MIR II is an interactive program and it consists of five major routines and a larger number of smaller program elements to perform the linear (three different functional forms) and non-linear (eleven mathematical models) regression analysis of kinetic data from enzyme and transmembrane transport experiments, also in the presence of inhibitors. Other features of the new program include a set of statistics and tests useful for the model building process, for the development of the mathematical model and for its validation and maintenance. An algorithm for fitting a straight line taking into account errors in both x and y is also provided.     

HCB, p,p'-DDE and PCB ontogenetic transfer and magnification in bluefin tuna (Thunnus thynnus) from the Mediterranean Sea

The bluefin tuna, Thunnus thynnus (Linnaeus 1758), is biologically and economically important in the Atlantic--Mediterranean ecosystems. Bluefin tuna feed on diverse food items depending on their age, thus they occupy different trophic levels during their lifespan. Hexachlorobenzene (HCB), p,p'-DDE and polychlorinated biphenyls (PCBs) are well-known persistent organic pollutants (POPs) in the Mediterranean basin. The relationship between stable isotopes of nitrogen (N) and the POP residue levels in tissues has recently increased knowledge on the link between the trophic levels and the contaminant accumulation. Trophic levels were estimated by using 15N/14N ratio (delta15N) and HCB, p,p'-DDE, and forty-three PCBs were quantified in bluefin tuna from the southern Tyrrhenian Sea. Results showed that changes in PCB and p,p'-DDE concentrations were a function of size and trophic level, while no correlations were observed for HCB. Apart from HCB and PCB nos. 101, 207, 95, 158, and 60 + 56, which did not show any significant increase per trophic level, the other PCBs and the p,p'-DDE increased significantly. The ontogenetic magnification factor of PCBs was 6.6 +/- 0.5, which was significantly (12 times) higher (p < 0.05) than the values found for p,p'-DDE (1.4) and HCB (1.4).     

Hydraulic conductivity changes in compacted clayey barriers due to temperature variations in landfill top covers

Bulletin of Engineering Geology and the Environment - In landfills, due to their low hydraulic conductivity, compacted clays (CC) are commonly used in multilayered structures as base liners and...     

A method to assess genomic DNA methylation using high-performance liquid chromatography/electrospray ionization mass spectrometry

Eukaryotic DNA is methylated at some cytosine residues, and this epigenetic feature performs critical functions. We developed a method for quantitative determination of 5-methyl-2'-deoxycytidine in human DNA using liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The DNA was enzymatically hydrolyzed by sequential digestion with three enzymes. DNA hydrolyzates were subsequently separated by reversed-phase high-performance liquid chromatography in isocratic mode. The four major DNA bases and 5-methyl-2'-deoxycytidine were resolved and eluted in 13 min. Identification of 2'-deoxycytidine and 5-methyl-2'-deoxycytidine was obtained by combined diode array UV spectra analysis and mass spectra of chromatographic peaks. The isotopomers [15N3]-2'-deoxycytidine and (methyl-d3,ring-6-d1)-5-methyl-2'-deoxycytidine were used as internal standards. Ions of m/z 126 and 130 were used to detect 5-methyl-2'-deoxycytidine and its isotopomer, and ions of m/z 112 and 115 were used to detect 2'-deoxycytidine and its stable isotopomer, respectively. The DNA methylation status was calculated on the basis of the amount of 5-methyl-2'-deoxycytidine per microgram of DNA with percent relative standard deviations (%RSD) for a method precision of 7.1 (within-day) and 5.7 (day-to-day). This method also allows the measurement of 5-methyl-2'-deoxycytidine expressed as a percentage of total deoxycytidine residues in genomic DNA with %RSD for method precision of 1.9 (within-day) and 1.7 (day-to-day). This LC/MS method for quantitative determination of genomic DNA methylation status is rapid, sensitive, selective, and precise.