The effect of circular bridge piers with different inclination angles toward downstream on scour

A fundamental principle in the safe design of bridge piers is to estimate maximum scour depth. As such, many researchers devoted their efforts to study the phenomenon of scour around bridge piers and to present relationships to estimate maximum scour depth. In the current research, scour around circular bridge piers with two different diameters and different inclination angles toward downstream has been investigated experimentally under clear water and different discharges. The obtained results revealed that increase in the inclination angle leads to a significant decrease in the scour depth, dimensions of sediment ridge and scour hole. Moreover, by comparing the data obtained from vertical bridge pier and well-known relationships, a relationship having the most agreement with the results was selected and modified to estimate equilibrium scour depth around inclined piers.     

A line-scanning semi-confocal multi-photon fluorescence microscope with a simultaneous broadband spectral acquisition and its application to the study of the thylakoid membrane of a cyanobacterium Anabaena PCC7120

We describe the construction and characterization of a laser‐line‐scanning microscope capable of detection of broad fluorescence spectra with a resolution of 1 nm. A near‐infrared femtosecond pulse train at 800 nm was illuminated on a line (one lateral axis, denoted as X axis) in a specimen by a resonant scanning mirror oscillating at 7.9 kHz, and total multi‐photon–induced fluorescence from the linear region was focused on the slit of an imaging polychromator. An electron‐multiplying CCD camera was used to resolve fluorescence of different colours at different horizontal pixels and fluorescence of different spatial positions in a specimen at different vertical pixels. Scanning on the other two axes (Y and Z) was achieved by a closed‐loop controlled sample scanning stage and a piezo‐driven objective actuator. The full widths at half maximum of the point‐spread function of the system were estimated to be 0.39–0.40, 0.33 and 0.56–0.59 μm for the X (lateral axis along the line‐scan), Y (the other lateral axis) and Z axes (the axial direction), respectively, at fluorescence wavelengths between 644 and 690 nm. A biological application of this microscope was demonstrated in a study of the sub‐cellular fluorescence spectra of thylakoid membranes in a cyanobacterium, Anabaena PCC7120. It was found that the fluorescence intensity ratio between chlorophyll molecules mainly of photosystem II and phycobilin molecules of phycobilisome (chlorophyll/phycobilin), in the thylakoid membranes, became lower as one probed deeper inside the cells. This was attributable not to position dependence of re‐absorption or scattering effects, but to an intrinsic change in the local physiological state of the thylakoid membrane, with the help of a transmission spectral measurement of sub‐cellular domains. The efficiency of the new line‐scanning spectromicroscope was estimated in comparison with our own point‐by‐point scanning spectromicroscope. Under typical conditions of observing cyanobacterial cells, the total exposure time became shorter by about 50 times for a constant excitation density. The improvement factor was proportional to the length of the line‐scanned region, as expected.     

ULTRAFILTRATION METHOD OF STUDYING BINDING OF LIGANDS TO MACROMOLECULES

The principles and procedures for studying binding of low molecular weight ligands to macromolecules using ultrafiltration are reviewed. Ultrafiltration methods are much faster and theoretically equivalent to equilibrium dialysis, which is the most commonly used subtractive method. An entire binding isotherm and the effect of free species concentration on the binding equilibrium can be determined with a single run of a few hours duration. The calculations and data analysis, which are normally quite complicated, can be easily performed using popular spread-sheet programs such as Lotus 1-2-3® on a personal computer. The experimental protocol, the control experiments to account for nonspecific binding and the calculation procedures are given in detail using a case study of a typical ligand-protein interaction.     

Phototransients in anodic tantalum oxide thin films

Phototransients under radiation of 274 nm have been studied in anodic tantalum oxide thin films. The area under the phototransient curves, the relaxation time end the decay time are found U> decrease with the applied field. For short times ΔI αexp ( ? t/r) with τ decreasing with field, while for longer times thore is a departure from exponential behaviour. These photo transients may be due to the drift of photoexcited electrons under the action of an applied field end their subsequent retrapping.