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161.
Sofiane Terzi Luc Salvo Michel Suéry Arne K. Dahle Elodie Boller 《Journal of Materials Science》2013,48(21):7422-7434
In conventional melting experiments of pure monocrystalline metals, the phase transformation starts at the sample surface and progresses inwards according to thermal gradients. In solutionized alloys, traces of internal melting are usually observed after reheating and quenching from the semi-solid state. The formation and development of these liquid pockets are not fully understood despite their significance in semi-solid processing, where the formability is greatly influenced by the distribution of liquid within the feedstock material. In situ X-ray microtomography was performed in this study to shed light on this phenomenon. We report in detail the melting and isothermal holding of a model binary alloy where a remarkable number of liquid droplets were observed to develop and coalesce. Various computational tools have been used to study their statistical evolution as well as the local ripening mechanisms involved. We analysed an interesting case of particle coarsening which differs from classical case studies by the fact that the fast-diffusing liquid phase is entrapped within the slow-diffusing solid medium. 相似文献
162.
We observe the effects of a temperature increase on the characteristics of an InGaAs/InP multiple-quantum-well (MQW) saturable absorber (SA) in a microcavity provided by an optical input signal under normal incidence. The temperature increase on the nonlinear mirror (NLM) due to an optical signal depends on the energy time filling factor (FF) of this input signal (analogous to the signal's duty cycle, which is the ratio between the repetition period and the pulse duration) and hence depends on the repetition rate of the signal for a given pulse time width. This increase in temperature is mostly responsible for a shift in the reflectivity spectrum of the device toward higher wavelengths. In this experimental study, we show the shift of the resonance cavity versus the optical input power at high FF, and we evaluate the thermal time constant of an Fe-doped InGaAs/InP MQW NLM. Finally, we report the consequences of such thermal effects and high fluence on the reflectivity and contrast of two different InGaAs/InP NLMs when the input signal FF rises up to 25%, which gets close to telecommunication transmission conditions. 相似文献
163.
Bartschke J. Knappe R. Boller K.-J. Wallenstein R. 《Quantum Electronics, IEEE Journal of》1997,33(12):2295-2300
We report on the investigation of efficient self-frequency doubling Nd:YAl3(BO3)4 (Nd:YAB) lasers. Pumped by 1.6 W of 807 nm diode laser radiation, the Nd:YAB laser generates a green 531-nm output of 225 mW which corresponds to a conversion of pump to visible output power of 14%. Conversion efficiencies as high as 20% could be achieved by using the diffraction-limited beam of a Ti:sapphire laser as pump source. In this case, 2.2 W of 807-nm Ti:sapphire radiation produced a 531-nm output of 450 mW. The experimental performance of these Nd:YAB lasers is in good agreement with the predictions of a numerical analysis based on rate equations adequate for lasers with self-frequency doubling 相似文献
164.
165.
L. Salvo P. Belestin E. Maire M. Jacquesson C. Vecchionacci E. Boller M. Bornert P. Doumalin 《Advanced Engineering Materials》2004,6(6):411-415
Al foam core / Al alloy skins sandwiches have potential for application in light weight structures. Recently, the foaming processes have improved and large, thick and 3D‐shape panels can be produced using the precursor technology. The microstructure of an AFS sandwich is analysed in this paper at a microscale and a mesoscale using X‐ray tomography and conventional SEM analysis. The main deformation mechanism of the core under compression is also studied thanks to in situ test. It is shown that the foam first present plastic buckling and then walls rupture. This is well correlated to the microstructure of the constitutive material of the core. 相似文献
166.
The Δ5-unsaturated polymethylene-interrupted fatty acid (Δ5-UPIFA) contents and profiles of gymnosperm seeds are useful chemometric
data for the taxonomy and phylogeny of that division, and these acids may also have some biomedical or nutritional applications.
We recapitulate here all data available on pine (Pinus; the largest genus in the family Pinaceae) seed fatty acid (SFA) compositions, including 28 unpublished compositions. This
overview encompasses 76 species, subspecies, and varieties, which is approximately one-half of all extant pines officially
recognized at these taxon levels. Qualitatively, the SFA from all pine species analyzed so far are identical. The genus Pinus is coherently united—but this qualitative feature can be extended to the whole family Pinaceae—by the presence of Δ5-UPIFA
with C18 [taxoleic (5,9–18∶2) and pinolenic (5,9,12–18∶3) acids] and C20 chains [5,11–20∶2, and sciadonic (5,11,14–20∶3) acids]. Not a single pine species was found so far with any of these acids
missing. Linoleic acid is almost always, except in a few cases, the prominent SFA, in the range 40–60% of total fatty acids.
The second habitual SFA is oleic acid, from 12 to 30%. Exceptions, however, occur, particularly in the Cembroides subsection, where oleic acid reaches ca. 45%, a value higher than that of linoleic acid. α-Linolenic acid, on the other hand, is a minor constituent of pine SFA,
almost always less than 1%, but that would reach 2.7% in one species (P. merkusii). The sum of saturated acids [16∶0 (major) and 18∶0 (minor) acids principally] is most often less than 10% of total SFA,
and anteiso-17∶0 acid is present in all species in amounts up to 0.3%. Regarding C18 Δ5-UPIFA, taxoleic acid reaches a maximum of 4.5% of total SFA, whereas pinolenic acid varies from 0.1 to 25.3%. The very
minor coniferonic (5,9,12,15–18∶4) acid is less than 0.2% in all species. The C20 elongation product of pinolenic acid, bishomo-pinolenic (7,11,14–20∶3) acid, is a frequent though minor SFA constituent (maximum,
0.7%). When considering C20 Δ5-UPIFA, a difference is noted between the subgenera Strobus and Pinus. In the former subgenus, 5,11–20∶2 and sciadonic acids are ≤0.3 and ≤1.9%, respectively, whereas in the latter subgenus,
they are most often ≥0.3 and ≥2.0%, respectively. The highest values for 5,11–20∶2 and sciadonic acids are 0.5% (many species)
and 7.0% (P. pinaster). The 5,11,14,17–20∶4 (juniperonic) acid is present occasionally in trace amounts. The highest level of total Δ5-UPIFA is
30–31% (P. sylvestris), and the lowest level is 0.6% (P. monophylla). Uniting as well as discriminating features that may complement the knowledge about the taxonomy and phylogeny of pines
are emphasized. 相似文献
167.
G.C. Requena Dr. H.P. Degischer E.D. Marks E. Boller 《Materialwissenschaft und Werkstofftechnik》2007,38(11):885-893
Developing connectivity of the phases in a short fibre reinforced aluminium piston alloy subjected to creep The evolution of the micro‐structure during creep of an AlSi12CuMgNi piston alloy with 15 vol% of Al2O3 short fibres is investigated by means of synchrotron micro‐tomography. The results reveal a 3D morphology of the rigid phases in the composite: the eutectic‐Si, the short fibres and the Fe‐ and Ni‐rich intermetallic particles, which form an interconnected hybrid reinforcement. The connectivity of these phases increases during creep exposure at 300 °C due to the diffusion induced ripening of Si and of the intermetallic particles. The hybrid reinforcement reaches almost complete percolation after 6400 h of creep exposure. The fibre orientation analysed by three‐dimensional Fast Fourier Transformation does not indicate any reorientation of the fibres along the load direction. The formerly observed strengthening effect during creep exposure is attributed to the increasing load carrying capacity of the interconnected hybrid reinforcement. The analysis of creep damage during secondary creep stage shows the increase of the void volume fraction by a factor of 2 with respect to the void content from processing, while the number of voids per volume remains practically constant. The voids are located at interfaces of the rigid phases and not within the α‐aluminium matrix. 相似文献
168.
Moreau-Guigon E Motelay-Massei A Harner T Pozo K Diamond M Chevreuil M Blanchoud H 《Environmental science & technology》2007,41(7):2172-2177
From May to September 2005, five passive air samples were deployed over five, 1-month periods at five elevations on the CN Tower in Toronto, Canada, to investigate the vertical distribution, seasonality, and sources of organochlorine pesticides. A strong seasonality was observed between spring and the end of summer. Vertical profiles differed for different pesticide classes. For instance, alpha- and gamma-hexachlorocyclohexane exhibited higher concentrations (60-80 pg m(-3), respectively) near the ground during the spring and early summer, suggesting that surface-air exchange within the city or nearby Lake Ontario may be important sources. The vertical profile for chlordane isomers was variable, suggesting that both advective and local inputs are important. For dieldrin, no obvious trend with elevation was observed, suggesting that concentrations could reflect a regional air mass contamination. Strongest seasonality was observed for the endosulfans, a widely used pesticide in North America, that reached peak concentrations of 750-850 pg m(-3) during June/July. Advective inputs of endosulfan from regional or more distant agricultural regions can explain the relatively uniform concentrations with elevation throughout the study period. The approach used in this study demonstrates that monthly average vertical concentration profiles differ between pesticide groups and reflect their use as well as the relative magnitude of input from local versus regional sources. 相似文献
169.
Voitoux E Lafarge V Collette C Lombard B 《International journal of food microbiology》2002,77(3):213-221
According to the draft standard method, EN ISO 16654 for the detection of Escherichia coli O157 in foods, samples of milk products inoculated with E. coli O157 were cultured in modified Tryptone Soya Broth supplemented with novobiocin. After immuno-magnetic separation (IMS) of the micro-organisms with magnetic beads coated with an antibody against E. coli O157 (Dynabeads anti E. coli O157, Dynal), the enrichment broth was subcultured onto both Cefixim Tellurite Sorbitol MacConkey agar and CHROMagar O157. IMS alone appeared not to be very specific to E. coli O157; however, IMS combined with CT-SMAC plating enabled a greater exclusivity. The method displayed a low limit of detection (1-2 cfu/25 g) of E. coli O157 strains in milk products after only 6 h of incubation of the enrichment broth. However, the detection was affected by storage of the inoculum at 4 degrees C, and another 12 to 18 h of incubation was necessary to recover potentially stressed cells. 相似文献
170.
Chlo Borde Clmentine Dillard Aurore LHonor Frdrique Quignon Marion Hamon Christophe H. Marchand Roberta Soares Faccion Maurício G. S. Costa Elodie Pramil Annette K. Larsen Michle Sabbah Stphane D. Lemaire Vincent Marchal Alexandre E. Escargueil 《International journal of molecular sciences》2022,23(14)
Energy metabolism reprogramming was recently listed as a hallmark of cancer. In this process, the switch from pyruvate kinase isoenzyme type M1 to pyruvate kinase isoenzyme type M2 (PKM2) is believed to play a crucial role. Interestingly, the activity of the active form of PKM2 can efficiently be inhibited by the high-mobility group box 1 (HMGB1) protein, leading to a rapid blockage of glucose-dependent aerobic respiration and cancer cell death. HMGB1 is a member of the HMG protein family. It contains two DNA-binding HMG-box domains and an acidic C-terminal tail capable of positively or negatively modulating its biological properties. In this work, we report that the deletion of the C-terminal tail of HMGB1 increases its activity towards a large panel of cancer cells without affecting the viability of normal immortalized fibroblasts. Moreover, in silico analysis suggests that the truncated form of HMGB1 retains the capacity of the full-length protein to interact with PKM2. However, based on the capacity of the cells to circumvent oxidative phosphorylation inhibition, we were able to identify either a cytotoxic or cytostatic effect of the proteins. Together, our study provides new insights in the characterization of the anticancer activity of HMGB1. 相似文献