Microstructural changes in weld metal during isothermal process. Study of reheat cracking in flux‐cored arc welding stainless steel weld metal (5th report)

The soiling of the slag, spatter and the fume, etc., which come into contact with the steel sheet surface with welding, is cleaned making use of steel sphere shot material of large particle diameter, high projection pressure with strong peening processing (below, called strong peening cleaning). In this research, the cleaning state of the soiling with welding and improvement of fatigue strength of the hot galvanized welded joint was inspected, when the surface of a SM490A welded joint was cleaned with strong peening cleaning.

The following experimental results were obtained:

1. The fatigue limit of smooth base metal which received strong peening cleaning at about 320 MPa was remarkably high in comparison with smooth base metal at about 245 MPa.

2. The fatigue limit of a welded joint which received strong peening cleaning at about 300 MPa was remarkably high in comparison with a welded joint at about 170 MPa.

3. The strong peening cleaning was highly efficient and the cleaning state was satisfactory.

4. The cause of the remarkable rise of the fatigue limit (300 MPa) of the welded joint which received strong peening cleaning was because the fatigue limit (about 170 MPa, 57%) of the welded joint was improved (about 130 MPa, 43%) with peening cleaning. It was considered that improvement effects were: a rise (about 68 MPa, 23%) of hardness of the weld toe; relief (about 43 MPa, 14%) of stress concentration; increase (about 136 MPa, 45%) of compressive residual stress; and the decrease (about ? 96 MPa, ? 32%) by increase of surface roughness.

5. The fatigue strength of the hot galvanized welded joint decreased remarkably. This was thought to be due to the decrease (about HV40) of hardness of the surface, the decrease (about 188 MPa) of the compressive residual stress and the influence of many factors which accompanied hot galvanizing.

     

Sequential exposure of porcine cumulus cells to FSH and/or LH is critical for appropriate expression of steroidogenic and ovulation-related genes that impact oocyte maturation in vivo and in vitro

In this study, we collected follicular fluid, granulosa cells, and cumulus cells from antral follicles at specific time intervals following equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) treatment of gilts. The treatment with eCG increased the production of estrogen coordinately with up-regulated proliferation of granulosa and cumulus cells. eCG also induced the expression of LHCGR and PGR in cumulus cells and progesterone accumulation was detected in follicular fluid prior to the LH/hCG surge. Moreover, progesterone and progesterone receptor (PGR) were critical for FSH-induced LHCGR expression in cumulus cells in culture. The expression of LHCGR mRNA in cumulus cells was associated with the ability of LH to induce prostaglandin production, release of epidermal growth factor (EGF)-like factors, and a disintegrin and metalloprotease with thrombospondin-like repeats 1 expression, promoting cumulus cell oocyte complexes (COCs) expansion and oocyte maturation. Based on the unique expression and regulation of PGR and LHCGR in cumulus cells, we designed a novel porcine COCs culture system in which hormones were added sequentially to mimic changes observed in vivo. Specifically, COCs from small antral follicles were pre-cultured with FSH and estradiol for 10 h at which time progesterone was added for another 10 h. After 20 h, COCs were moved to fresh medium containing LH, EGF, and progesterone. The oocytes matured in this revised COC culture system exhibited greater developmental competence to blastocyst stage. From these results, we conclude that to achieve optimal COC expansion and oocyte maturation in culture the unique gene expression patterns in cumulus cells of each species need to be characterized and used to increase the effectiveness of hormone stimulation.     

A simple screening procedure for heterotrophic nitrifying bacteria with oxygen-tolerant denitrification activity

Various naturally occurring strains of heterotrophic nitrifying bacteria were isolated by enrichment culture using acetamide as the C and N source, and 21 strains were identified as heterotrophic nitrifiers. Using a new simple procedure, these 21 strains were also investigated for the ability to carry out denitrifcation in the presence of oxygen. Several of the nitrifying strains were found to exhibit a distinct activity that allows for denitrifcation via nitrite (NO2-) in the presence of oxygen, indicating that they have an oxygen-tolerant denitrifcation system. A wide variety of bacteria possessing both nitrification and denitrifcation capabilities in the presence of oxygen were isolated and partially characterized by using the simple screening combinatorial procedure described in this paper.     

Visualization of epileptogenic phenomena using cross-correlation analysis: localization of epileptic foci and propagation of epileptiform discharges

The main objectives of the preoperative evaluation of a patient with medically intractable epileptic seizures are localization of the foci and propagation of the epileptiform discharges. Electrocorticographic (ECoG) data of intractable focal epilepsy were analyzed using an AR model, wavelet analysis, and cross-correlation analysis. In order to derive the time-shifts, the cross correlations of the epileptiform discharges were calculated between electrodes for every unit of time. Further analyses were made by means of a set of contour maps of the time-shifts and sequential two- and three-dimensional visualizations of the time-shift maps in order to localize the epileptic foci and study their propagation process. Two types of foci and propagation were revealed in the results. In the first type, epileptiform discharges were generated at localized focal sites and spread quickly to other sites. In the second type, the foci of epileptiform discharges, which appeared soon after the former bursts, were localized at more than one site, and the discharges tended to spread more slowly. The findings suggest that epileptic phenomena can be caused by at least two kinds of mechanisms in one patient: in the former, the propagation might be mediated through synaptic projections, while in the latter, the extracellular diffusion of an excitatory factor might play an important role. In addition, our newly developed visualization technique for the localization of epileptic foci and the propagation of epileptiform discharges should prove useful in the study of epileptogenesis etiology.     

Large graded-index preforms fabricated by high-rate VAD

A large preform for 220 km of fibre was fabricated with the vapour-phase axial deposition (VAD) method. The deposition rate for the core was 1.7 g/min. Optical fibre drawn from a part of the preform had optical attenuation of 0.58 dB/km and bandwidth 500 MHz km0.9 at a wavelength of 1.3 ?m.     

Control of assembly size of poly (methacrylic acid)-<Emphasis Type=Italic>grafted</Emphasis> fullerenes in aqueous solution

We synthesized poly(methacrylic acid)-grafted fullerenes (PMA-C₆₀) with different PMA molecular weights and investigated the assembly size formed by PMA-C₆₀ in aqueous solution. The molecular weight of PMA strongly affects the assembly size: PMA-C₆₀ with a larger molecular weight forms micelles with 20 nm diameters while PMA-C₆₀ with a smaller molecular weight forms monodisperse assemblies with 200 nm hydrodynamic diameters. We succeeded in converting the large monodisperse assembly into micelles by adding either ionic species or ethanol. This result provides insight into controlling the assembly size of fullerene-containing assemblies.     

Chain stiffness and chain conformation of poly(α-methylene-γ-butyrolactone) in dilute solutions

The chain stiffness and local chain conformation of atactic poly(α-methylene-γ-butyrolactone) (PMBL), which is a side chain cyclic structural analog of poly(methyl methacrylate) (PMMA), with a weight-average molecular weight (M_w) ranging from 2.8 × 10³ to 2.6 × 10⁶ in N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) were characterized by size exclusion chromatography with a multi-angle light-scattering detector (SEC-MALS) and synchrotron radiation small-angle X-ray scattering (SAXS). Based on the Kratky-Porod worm-like chain model, the scattering functions and the M_w dependence of z-average root-mean-square radius of gyration <S²>_z^1/2 yielded the Kuhn segment lengths λ⁻¹, the diameter of the PMBL chains d, and the excluded-volume strengths in DMF and GBL. The local conformation of atactic PMBL in DMF and GBL were slightly larger than those of atactic PMMA, due to the presence of the conformationally rigid lactone ring structure.