Thermo-mechanical and diffusion modelling in the process of ceramic–metal friction welding

In this paper a modelling of friction welding of elastic materials with elastic–plastic metals is presented. This model has been practically verified in the process of friction welding of corundum ceramic of 97.5% Al₂O₃ content and aluminium alloy 6061-T6 as well as in the same ceramic and electrolytic copper of 99.9% Cu content. Mechanical strength of the acquired welded joints was around 30 MPa.A simulation of the process was performed by means of the finite element method using two FEM systems, namely ADINA-T and ADINA. The simulations made it possible to observe the temperature distribution and thermo-mechanical fields that take place during the process. The obtained results show that the temperature, pressure and the deformation distribution near the contact surface are non-homogeneous. It causes not even conditions to create the bond and internal stresses generation. The agreement between the numerical geometry prediction and the experimental data proves the validity of the proposed model.The performed calculations and preliminary studies on the influence of the diffusion phenomena on the welding process showed that the diffusion depth is approximately 4 μm and the calculated diffusion coefficient of Al into Al₂O₃ is 1.8 × 10^?13 m²/s.Numerical simulation of the friction welding process allows better understanding of the whole process, final products shape prediction and can be helpful during design of the process using other materials.     

High-risk mitral valve replacement in severe pulmonary hypertension--30 years experience

OBJECTIVE: In the past 30 years, 2316 patients underwent mitral valve replacement (MVR) at our institution; 382 of them had severe pulmonary hypertension (pulmonary artery pressure (PAP) > 50 mmHg; pulmonary vascular resistance (PVR), 690 +/- 46 dyn/s per m2). We reviewed our early and late results in this high-risk subgroup. METHODS: We used 336 mechanical and 46 biological devices for MVR. The follow-up was 95%, with an observation period of 3208 patient-years and a mean of 8.4 +/- 0.2 years per patient. The overall early mortality rate was 10.5% (n = 40) and stayed at about the same level over the years, although patients characteristics have changed to much older patients and more reoperations. To clarify this fact we divided our data in results according to the decades in which the operations were carried out. The clinical preoperative status and results were as follows (*P < 0.05; **P < 0.01 compared with previous decade). In the decades between 1963 and 1973 (I), 1974 and 1983 (11) and 1984 and 1993 (III) we operated on n = 95 (I), n = 185 (II), and n = 102 (III) patients with a mean age of 43 +/- 1 (I), 50 +/- 1** (II), and 58 +/- 1** (III) years. The incidence of reoperations among these patients was 3.2 (I), 4.9 (II), and 22.6%** (III). The early mortalities were 13.7 (I), 8.6* (II) and 10.8% (III); late mortalities lowered from 5.77 (I), over 4.95 (II), and up to 3.39%** (III) patients/year. The mean functional status according to New York Heart Association (NYHA) class improved from preoperatively 3.0 +/- 0.1 (I), 3.2 +/- 0.1 (II) and 3.3 +/- 0.1 (III) to 2.4 +/- 0.2 (I), 2.4 +/- 0.1 (II) and 2.3 +/- 0.1 (III) postoperatively. RESULTS: Compared with routine elective MVR with a mortality rate of 3.6% (P < 0.01), early mortality is high. But once the patient survives the perioperative course, late results show no difference compared with patients without pulmonary hypertension. The functional results as well are not significantly different. In spite of on average 15 years older multimorbid patients with therefore higher complication rates, early results improved slightly, which could be explained by better operative techniques, perioperative treatment and nursing (online monitoring with immediate therapeutic substitution). Surprisingly the increased number of reoperations had no negative impact on patients' outcomes. CONCLUSION: According to our results, we recommend MVR in severe pulmonary hypertension even in the elderly, with a high but acceptable risk and good long-term results.     

Efficient pseudotyping of murine leukemia virus particles with chimeric human foamy virus envelope proteins

Incorporation of human foamy virus (HFV) envelope proteins into murine leukemia virus (MuLV) particles was studied in a transient transfection packaging cell system. We report here that wild-type HFV envelope protein can pseudotype MuLV particles, albeit at low efficiency. Complete or partial removal of the HFV cytoplasmic tail resulted in an abolishment or reduction of HFV-mediated infectivity, implicating a role of the HFV envelope cytoplasmic tail in the pseudotyping of MuLV particles. Mutation of the endoplasmic reticulum retention signal present in the HFV envelope cytoplasmic tail did not result in a higher relative infectivity of pseudotyped retroviral vectors. However, a chimeric envelope protein, containing an unprocessed MuLV envelope cytoplasmic domain fused to a truncated HFV envelope protein, showed an enhanced HFV specific infectivity as a result of an increased incorporation of chimeric envelope proteins into MuLV particles.     

Shot peening on the high-strength wrought magnesium alloy AZ80—Effect of peening media

Influence of shot peening media on fatigue performance of the high-strength wrought magnesium alloy AZ80 has been investigated at Almen intensities ranging from 0.04 to 0.4 mmN. By the use of different peening media (including glass beads, Zirblast B30 and Ce-ZrO₂ (ZrO₂ beads stabilized by Ce)), the improvement of about 60–75% in fatigue strength was achieved at optimum conditions. Peening AZ80 with Ce-ZrO₂ shots resulted in the fewest surface defects, lowest roughness, highest maximum compressive residual stress and highest improvement of fatigue strength. A pronounced overpeening effect was observed when glass beads or Zirblast B30 shots were used as peening media. In contrast, specimens shot-peened by Ce-ZrO₂ shots exhibited an extremely broad process window, i.e. the overpeening effect disappeared.     

An X-ray fluorescence study on the segregation of Cs and I in an inverted organic solar cell

X-ray near-total-reflection fluorescence reveals that in multilayers of the inverted organic solar cell (ITO/CsI/P3HT:PCBM-based) Cs diffuses into the organic layer and iodide diffuses into the ITO. Laser ablation inductively coupled plasma mass spectrometry measurements, which integrate elemental concentration across the whole multilayer structure, indicate that the Cs:I ratio remains 1:1 confirming there is no loss of iodine from the sample. Iodide diffusion to the bulk ITO layer is also found in a similarly prepared ITO/NaI/P3HT:PCBM multilayer structure. Our results are consistent with recent XPS measurements which show that the Cs:I ratio at the ITO/CsI surface exceeds 8:1, and rationalize this observation.     

Effect of dietary ractopamine on tenderness and postmortem protein degradation of pork muscle

Twenty-four finishing pigs with a mean starting weight of 82 kg were assigned to two dietary regimens: (1) a corn–soybean meal basal diet (control; n = 12), and (2) the basal diet supplemented with 20 ppm ractopamine HCl (RAC; n = 12). After 28–30 days on the feeding trial, pigs were slaughtered, and the growth and carcass characteristics were measured. Furthermore, the 3rd–13th rib section of longissimus muscle was excised at 48 h postmortem, sliced into 19-mm thick chops, vacuum packaged, stored at 2 °C, and subjected to Warner–Bratzler shear force (WBSF) and electrophoretic tests after 2, 4, 7, 10, 14, and 21 days (postmortem). RAC feeding increased (P < 0.01) pig carcass weight and percent lean, but it also increased the day-2 muscle WBSF by 20% (P < 0.01). The shear force difference between control and RAC pig muscles gradually decreased and vanished by day 10 (P > 0.05) when both muscle groups became more tender. The muscle from RAC-fed pigs exhibited a slower protein degradation rate than muscle from the control animals, notably for proteins in the 15–45 kDa range. The results suggested that the tenderness difference between ractopamine-treated and control pig muscles was related to the proteolysis rate, and could be diminished with adequate postmortem ageing.     

NaAlH4 confined in ordered mesoporous carbon

In this paper we performed a comprehensive investigation of the structural and sorption properties of a 40 wt. % NaAlH₄ confined in a ordered mesoporous carbon (OMC, i.e. CMK-3) by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), ²³Na{¹H} and ²⁷Al{¹H} solid-state magic angle spinning-nuclear magnetic resonance (MAS-NMR).