Synchrotron X-ray diffraction study of the phase transformations in titanium alloys

High-resolution synchrotron X-ray diffraction was used to study the phase transformations in titanium alloys. Three titanium alloys were investigated: Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo-0.08Si and beta21s. Both room and high temperature measurements were performed. The room temperature experiments were performed to study the structure of the alloys after different heat treatments, namely as received (AR), furnace cooling (FC), water quenching (WQ) and water quenching followed by ageing. The alpha, alpha', alpha'' and beta phases were observed in different combinations depending on the heat treatment conditions and the alloy studied. A multicomponent hexagonal close packed (hcp) alpha phase, with different c and the same a lattice parameters, was detected in Ti-6Al-4V after FC. High temperature synchrotron X-ray diffraction was used for 'in situ' study of the transformations on the sample surface at elevated temperatures. The results were used to trace the kinetics of surface oxidation and the concurrent phase transformations taking place under different conditions. The influence of the temperature and oxygen content on the lattice parameters of the alpha phase was derived and new data obtained on the coefficients of thermal expansion in the different directions of the hcp alpha phase, for Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.08Si.

Geometry- and diffraction-independent ionization probabilities in intense laser fields: Probing atomic ionization mechanisms with effective intensity matching

We report an experimental technique for the comparison of ionization processes in ultrafast laser pulses irrespective of pulse ellipticity. Multiple ionization of xenon by 50 fs 790 nm, linearly and circularly polarized laser pulses is observed over the intensity range 10 TW/cm(2) to 10 PW/cm(2) using effective intensity matching (EIM), which is coupled with intensity selective scanning (ISS) to recover the geometry-independent probability of ionization. Such measurements, made possible by quantifying diffraction effects in the laser focus, are compared directly to theoretical predictions of multiphoton, tunnel and field ionization, and a remarkable agreement demonstrated. EIM-ISS allows the straightforward quantification of the probability of recollision ionization in a linearly polarized laser pulse. Furthermore, the probability of ionization is discussed in terms of the Keldysh adiabaticity parameter gamma, and the influence of the precursor ionic states present in recollision ionization is observed.

Geometrical dependence in photoionization of H-2(+) in high-intensity, high-frequency, ultrashort laser pulses

The ionization dynamics of H2 + exposed to high-intensity, high-frequency, ultrashort laser pulses is investigated with two theoretical approaches. The time-dependent Schrödinger equation is solved by a direct numerical method, and a simple two-center interference-diffraction model is studied. The energy and angular distributions of the photoelectron for various internuclear distances and relative orientations between the internuclear axis of the molecule and the polarization of the field are calculated. The main features of the photoelectron spectrum pattern are described well by the interference-diffraction model, and excellent quantitative agreement between the two methods is found. The effect of quantal vibration on the photoelectron spectrum is also calculated. We find that vibrational average produces some broadening of the main features, but that the patterns remain clearly distinguishable.

Protein expression pattern of CDK11(p58) during testicular development in the mouse.

Protein kinases are important signalling molecules critical for normal cell growth and development. CDK11(p58) is a p34(cdc2) related protein kinase, and plays an important role in normal cell cycle progression. In this study, we mainly characterized the protein expression of CDK11(p58) during postnatal development in mouse testes and examined the cellular localization of CDK11(p58) and cyclinD3, which was associated with CDK11(p58) in mammalian cells. Western blot analysis revealed that CDK11(p58) was present in the early stages of development. It gradually increased and reached a peak in adult testes. The protein expression of CDK11(p58) was further analysed by immunohistochemistry due to its developmentally regulated expression. The variable immunostaining patterns of CDK11(p58) were visualized during different developmental periods and, in adult mouse, different stages of seminiferous tubules. CDK11(p58) expression was detected in proliferating germ cells in the early stages of developing testes. In adult testes, the protein was expressed in pachytene primary spermatocytes from stage VII to XI of spermatogenesis and in postmeiotic spermatids in all stages at different levels. The colocalization of CDK11(p58) and cyclinD3 in the adult testis was revealed by immunofluorescence analysis.