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61.
J. Frenzel E.P. George A. Dlouhy Ch. Somsen M.F.-X. Wagner G. Eggeler 《Acta Materialia》2010,58(9):3444-3458
High-precision data on phase transformation temperatures in NiTi, including numerical expressions for the effect of Ni on MS, MF, AS, AF and T0, are obtained, and the reasons for the large experimental scatter observed in previous studies are discussed. Clear experimental evidence is provided confirming the predictions of Tang et al. 1999 [19] regarding deviations from a linear relation between the thermodynamic equilibrium temperature and Ni concentration. In addition to affecting the phase transition temperatures, increasing Ni contents are found to decrease the width of thermal hysteresis and the heat of transformation. These findings are rationalized on the basis of the crystallographic data of Prokoshkin et al. 2004 [68] and the theory of Ball and James [25]. The results show that it is important to document carefully the details of the arc-melting procedure used to make shape memory alloys and that, if the effects of processing are properly accounted for, precise values for the Ni concentration of the NiTi matrix can be obtained. 相似文献
62.
Petko N. Denev Christo G. Kratchanov Milan Ciz Antonin Lojek Maria G. Kratchanova 《Comprehensive Reviews in Food Science and Food Safety》2012,11(5):471-489
Abstract: Black chokeberry (Aronia melanocarpa) is a distinctive berry with a high content of polyphenol compounds and possesses one of the highest in vitro antioxidant activities among fruits. The bioavailability of aronia polyphenols seems to be low, but there is ample evidence for chokeberry health benefits including antidiabetic, cardioprotective, hepatoprotective, antimutagenic, and anticarcinogenic effects. This review presents the available information for the bioavailability and antioxidant activity of chokeberry polyphenols and explains the possible mechanisms of action in vivo in the prevention and treatment of oxidative stress‐related diseases. The review shows the available data for chokeberry antioxidant activity in vitro, in isolated cells and cell lines, and in vivo, in both human subjects and animals. It is evident that in vivo antioxidant action of chokeberry extends far beyond radical scavenging and includes suppression of reactive oxygen and nitrogen species formation, inhibition of prooxidant enzymes, restoration of antioxidant enzymes, and probably cellular signaling to regulate the level of antioxidant compounds and enzymes. The original contribution of this work is that it compiles the available information up to date and outlines the gaps and future directions in the assessment of chokeberry antioxidant action in vivo. 相似文献
63.
Of 52 antibiotic-resistant Bordetella bronchiseptica isolates from cats, ten carried plasmids. Only two of these plasmids, pLV1400 and pLV1401, were self-transmissible to Escherichia coli K12; both plasmids encoded resistance to ampicillin, tetracycline, sulphonamides, streptomycin and mercuric chloride, and were of incompatibility group P (IncP). Transferable tetracycline resistance has not been reported in B. bronchiseptica previously. The plasmids were identical in size (c.51 kb), restriction endonuclease digestion pattern and gene sequences (trfA and korA) within the IncP replicon. The trfA and korA sequences differed from those of the archetypal IncP plasmids RP4 and R751. Although the two B. bronchiseptica isolates were from epidemiologically and geographically separated cats, pulsed-field gel electrophoresis of their XbaI- or DraI-digested chromosomal DNA indicated that they were genotypically identical. The plasmid-encoded ampicillin resistance was mediated by a penicillinase of molecular weight 49,000, and pI 8.45 which was inhibited by clavulanate (IC50 = 0.1 mg/L) and tazobactam (IC50 = 0.42 mg/L) but not by parachloromercuribenzoate or EDTA. The high-level tetracycline resistance was mediated by a class C efflux mechanism that has not been described previously in this genus. The presence of transferable multi-drug resistance on a promiscuous plasmid may limit options for therapy of respiratory tract infection in companion and farm animals. 相似文献
64.
A. Kostka G. Mälzer G. Eggeler A. Dlouhy S. Reese T. Mack 《Journal of Materials Science》2007,42(11):3951-3957
In the present study, we investigate dislocation processes in a Ni-base single crystal superalloy (LEK94) after high temperature
and low stress creep. Specimens were creep deformed at 240 MPa and 980 °C to a strain of 20%. We use diffraction contrast
transmission electron microscopy (TEM) to show that two γ-channel dislocations with different Burgers vectors combine and
form a super dislocation that shears the γ′-particle. This type of cutting event has now been observed for three single crystal
superalloys with different alloy chemistry (CMSX-4, CMSX-6 and LEK94 in the present work) and we therefore conclude that it
represents a generic elementary dislocation process which governs high temperature (around 1000 °C) and low stress (around
240 MPa) creep. The present paper provides microstructural evidence for this type of cutting processes and discusses the results
in the light of previous work published in the literature. 相似文献
65.
F Negoita C Borcea F Carstoiu M Lewitowicz MG Saint-Laurent R Anne D Bazin JM Corre P Roussel-Chomaz V Borrel D Guillemaud-Mueller H Keller AC Mueller F Pougheon O Sorlin S Lukyanov Y Penionzhkevich A Fomichev N Skobelev O Tarasov Z Dlouhy A Kordyasz 《Canadian Metallurgical Quarterly》1996,54(4):1787-1797
66.
Matthias Frotscher Sangni Wu Tobias Simon Christoph Somsen Antonin Dlouhy Gunther Eggeler 《Advanced Engineering Materials》2011,13(5):B181-B186
In the present study, we investigate the fatigue behavior of Nickel Titanium (NiTi) microstents at 22 °C (room temperature) and 37 °C up to 30 × 106 load cycles. We briefly describe our test procedure, which applies displacement‐controlled pull–pull fatigue cycling between displacements corresponding to apparent strains of 5 and 7.5%. The response of the microstents to mechanical loading indicates cyclic softening during 30 × 104 cycles. Subsequently, the maximum load remains constant throughout the remainder of the test. We use transmission electron microscopy (TEM) to clarify the microstructural reasons for cyclic softening. A focused ion beam (FIB) technique is used to take out thin foil specimens from critical microstent locations. Our TEM results show that the dislocation density increases during cycling. We also find that microstructural regions with stabilized stress‐induced B19′ martensite can be detected. 相似文献
67.
Marie Kalbacova Antonin Broz Alexander Kromka Oleg Babchenko Martin Kalbac 《Carbon》2011,49(9):2926-2934
The effects of oxidative treatment of single-walled carbon nanotubes (SWCNTs) on the adhesion and proliferation of human osteoblasts (SAOS-2) were investigated. The surface properties of SWCNTs after oxygen plasma treatment were characterized by contact angle measurement, scanning electron microscopy and Raman spectroscopy. The immunofluorescent staining of vinculin, actin filaments and nuclei was used to probe cell adhesion and growth on SWCNT films. Our results show that adhesion and proliferation of human osteoblasts cultivated on SWCNT films indeed depends on the degree of an oxidative treatment. As an optimal procedure was found the treatment with oxygen plasma for 5 min. In the latter case the osteoblasts form a confluent layer with pronounced focal adhesions throughout the entire cell body. The optimal conditions compromise the effect of hydrophilic character of SWCNT films and the level of damage of SWCNT surface. 相似文献
68.
Hermann Antonin Kouassi Emma Fernande Assemand Olivier Gibert Isabelle Maraval Julien Ricci Deless Edmond Fulgence Thiemele Christophe Bugaud 《International Journal of Food Science & Technology》2021,56(3):1160-1170
Boiled pulp is a major form of consumption for plantain. We assessed instrumental (puncture test and texture profile analysis) and sensory texture attributes of 13 plantain cultivars, two cooking hybrids and one dessert banana at different stages of ripeness after cooking in boiling water. Firmness, chewiness, stickiness, mealiness, sweetness and moistness described sensory variability, which was greater between stages of ripeness than between types of cultivars. Firmness and chewiness were well-predicted by instrumental force and hardness (r2 > 0.72), and by soluble solid and dry matter content (r2 > 0.85). Complementary sensitivity analysis revealed that a pulp puncture force or a hardness of at least 2.1 N or of 0.3 N/mm2 was needed before a difference in firmness or chewiness could be perceived; a Brix of 3.7 was required to ensure a detectable difference in sweetness. Rheological and biochemical predictors can be useful for breeders for high-throughput phenotyping. 相似文献
69.
S. Manchuraju A. Kroeger C. Somsen A. Dlouhy G. Eggeler P.M. Sarosi P.M. Anderson M.J. Mills 《Acta Materialia》2012,60(6-7):2770-2777
The stress-induced B2–B19′ transformation in aged 51 at.% NiTi was investigated using in situ straining transmission electron microscopy (TEM). Increased applied strain along [1 1 0]B2 transforms B2 into plates containing B19′ variants that are related by a (1 1 0)B2 compound twin plane. This atypical twin plane is explained by relaxing the invariant plane constraint in the crystallographic theory of martensite (CTM) to an invariant line constraint. The relaxation is rationalized from the thin foil geometry. The relaxed CTM approach, coupled with conditions to maximize transformation strain along the loading axis and minimize elastic energy, predicts the observed twin interface, diffraction patterns, and interface with the B2 austenite. These results demonstrate subtleties in interpreting thin foil TEM results regarding martensitic transformations, and translating those results to bulk response. 相似文献
70.
Antonin Durand Laurent Mazliak 《Centaurus; international magazine of the history of science and medicine》2011,53(4):306-332
In this paper, we revisit the origins of Emile Borel's developing interest in probability around 1905. This resulted from new findings in his research on continued fraction, but it also cannot be separated from the discovery of new applications for the mathematics of randomness (such as biology or economics) and of their importance as a life‐changing tool for the citizen. In particular, we underline the role of a paper published by Vito Volterra in Borel's Revue du Mois. 相似文献