The impact of micro-alloying on tensile behavior at strain rates in various ranges is examined using five types of extruded Mg-0.3 at. pct Mn–0.1 at. pct X ternary alloys, where X is selected as a common element, Al, Li, Sn, Y or Zn. Microstructural observations reveal that the average grain size of these extruded alloys is between 1 and 3 μm, and these micro-alloying elements segregate at grain boundaries. In room temperature tensile and compression tests, these results show that the mechanical properties and deformation behavior are influenced by the micro-alloying element, even as a small addition of 0.1 at. pct. Mg–Mn–Y and Mg–Mn-Zn alloys show higher strength and smaller strain rate sensitivity (m-value) among the present alloys, owing to the rate-controlling mechanism as dislocation slip. On the other hand, the Mg–Mn–Li alloy exhibits the largest elongation to failure in tension and the highest strain rate sensitivity, associated with high contribution of grain boundary sliding to deformation. These differences are due to the grain boundary segregation of the micro-alloying elements. Compared to the common Mg alloys, the present ternary alloys also show a trade-off relationship between strength and ductility, which is similar to that of the well-known Mg alloys; however, these properties of the Mg–Mn system ternary alloys could be controlled via the type of micro-alloying elements with a chemical content of 0.1 at. pct.
In order to investigate the effects of bile acid feeding on hepatic microsomal deoxycholate 7α-hydroxylase activity, three
different bile acids were administered (0.2% w/w in chow) to hamsters for two weeks. Deoxycholate 7α-hydroxylase activity
was increased markedly by feeding of cholic acid (CA) and slightly by deoxycholic acid (DCA) Chenodeoxycholic acid (CDCA)
had little effect on the enzyme activity. Feeding each of the bile acids significantly inhibited the activity of cholesterol
7α-hydroxylase in the order CDCA≥ DCA>CA. There was no correlation between deoxycholate 7α-hydroxylase activity and cholesterol
7α-hydroxylase activity. It is concluded that the activity of deoxycholate 7α-hydroxylase is up-regulated by feeding DCA and
CA and that the mechanism seems to be different from that of cholesterol 7α-hydroxylase. The increased activity of hepatic
deoxycholate 7α-hydroxylase by CA and DCA should be beneficial in minimizing the toxic effects of DCA in the hamster. 相似文献
For the purpose of synthesizing standards to be used in the quantification of TAG hydroperoxides, three TAG (1,2-dioleoyl-3-palmitoylglycerol,
1-oleoyl-2-linoleoyl-3-palmitoylglycerol, and triolein) monohydroperoxides were chemically synthesized as authentic specimens.
TAG were prepared by using a simple condensation in pyridine of glycerol and the corresponding acid chlorides. These TAG were
then converted into monohydroperoxides by a photosensitized peroxidation. The synthesized monohydroperoxides were analyzed
by normal-phase and RP-HPLC. The results of normal-phase HPLC analysis showed that monohydroperoxides from a corresponding
TAG were a mixture of regioisomers. In RP-HPLC, however, the regioisomers of monohydroperoxides were not separated and gave
a single peak, which may improve the sensitivity for the detection of TAG monohydroperoxides. In this study TAG monohydroperoxide
standards were synthesized; these will be useful for the study of yet unknown biological and pathological roles of TAG hydroperoxides. 相似文献
The evaporation drain of sulfite pulp spent liquor contains few volatile fatty acids, most of which is acetic acid. The main objective of this study is to recover acetic acid as the concentrated solution (about 4%), which could be used as a culture medium of the yeast. As acetic acid can easily pass through the cellulose acetate membrane, SP drains neutralized by NaOH, NH4OH and Ca(OH)2 were used as the feed solutions. In all cases, concentration by reverse osmosis was successfully carried out provided the appropriate pretreatment was employed. The recovery of acetic acid was 95.6, 90.5 and 98.2% for Na-, NH4-, and Ca-drain, respectively. In addition, the recovered (permeated) water may be used as an industrial one. 相似文献
Molecular properties of polymorphic forms of gondoic acid [cis-C20:1Δ11ω9 (GOA)] have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical microscopy, and
Raman scattering, in comparison to those of six principal unsaturated fatty acids: oleic acid [cis-C18:1Δ9ω9 (OA)], erucic acid [cis-C22:1Δ13ω9 (ERA)], petroselinic acid [cis-C18:1Δ6ω12 (PSA)], asclepic acid [cis-C18:1Δ11ω7 (APA)], palmitoleic acid [cis-C16:1Δ9ω7 (POA)], and elaidic acid [trans-C18:1Δ9ω9 (ELA)]. In addition, phase behavior of binary mixtures of GOA and APA and OA was examined by XRD and DSC. The polymorphic
structures of GOA are quite similar to those of APA, ERA, POA, and partly to OA. In particular, DSC and Raman scattering studies
have shown that gondoic acid exhibits conformational disordering on heating at the ω-chain, a chain segment between the double
bond and CH3 group, as a transition from all-trans (γ form) to gauche-rich (α form) conformations. A miscible mixing phase was observed in the mixture of GOA and APA, yet eutectic phases were
observed in the GOA and OA mixtures. This is a remarkable contrast because the binary mixture systems of varying combinations
of cis-unsaturated fatty acids examined so far exhibited either eutectic nature or molecular compound formation. It is expected
that specific molecular interactions between GOA and APA that originate from the equivalence of the length of the Δ-chain,
the chain segment between the cis-double bond and COOH group, and also from the presence of the γ-α order-disorder transformation would be operating to form
the miscible mixing phase. 相似文献
The purpose of this study was to investigate the physiological and subjective responses of the European, Japanese (JPN) and US firefighters' helmet, gloves and boots for international standardisation. Three experimental conditions were evaluated (clothing mass: 9.4, 8.2 and 10.1 kg for the three conditions, respectively) at the air temperature of 32°C and 60% relative humidity. The results showed that there was no significant difference among the three conditions in oxygen consumption, heart rate, total sweat rate, rectal temperature and mean skin temperature, whereas peripheral temperatures and subjective perceptions were lower in the JPN condition than in the other conditions (P < 0.05). These results indicate that a 0.5-kg reduction in helmet mass and a 1.1-kg reduction in boot mass during exercise resulted in a significant decrease in head and leg temperatures and subjective perceptions, while a 1.9-kg reduction in total clothing mass had insignificant influences on the metabolic burden and overall body temperature. 相似文献
To determine the region of human tumor necrosis factor-alpha(TNF-), essential for cytotoxic activity against mouse L-M cells,single amino-acid-substituted TNF- mutant proteins (muteins)were produced in Escherichia coli by protein engineering techniques.An expression plasmid for TNF- was mutagenized by passage throughan E.coli mutD5 mutator strain and by oligonucleotide-directedmutagenesis. Approximately 100 single amino-acid-substitutedTNF- muteins were produced and assayed for cytotoxic activity.The cytotoxic activities of purified TNF- muteins, e.g. TNF-31T,-32Y, -82D, -85H, -115L, -141Y, -144K and -146E, were < 1%of that of parent TNF-. These results indicate that the integrityof at least four distinct regions of the TNF- molecule is requiredfor full biological activity. These regions are designated asfollows: region I, from position 30 to 32; region II, from position82 to 89; region III, from position 115 to 117; region FV, fromposition 141 to 146. In addition, TNF-141Y could not completelycompete with parent TNF- for binding to the receptor. This demonstratesthat region IV, and at least aspartk acid at position 141, mustbe involved in the TNF receptor binding site. 相似文献
This study was undertaken to estimate the effect of dietary high oleic acid oil (OA) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone
(NNK)-induced lung tumorigenesis in mice. Diet containing 10% oil was fed to mice through experimental periods. On day 30
after NNK injection (100 mg/kg body weight, i.p.), the treatment increased the level of prostaglandin E2 (PGE2) as well as proliferating cell nuclear antigen, a marker of cell proliferation in a high linoleic acid oil (LA)-fed group
but not in an OA-fed group. The NNK treatment also induced the activation of an extracellular signal-regulated kinase (Erk)
cascade (Erk, Mek and Raf-1) in an LA-fed group. On the other hand, OA feeding abolished the NNK-induced activation of the
Erk cascade. In conjugation with these events, OA feeding reduced lung tumor incidence and tumor multiplicity (percentage
of mice with tumors) in mice compared with LA feeding at the 20th experimental week. These results suggest that OA suppresses
lung tumorigenesis and that this suppression is correlated with the inhibition of PGE2 production and inactivation of the Erk cascade. 相似文献
The synthesis of super-microporous aluminosilicate with a pore diameter of 14.6 Å has been achieved, by means of synthesis under specified conditions with a skeletal material comprising TMOS and a small quantity of sodium aluminate, and a conventional alkyl-trimethylammonium halide (C10TMABr) as a template. This super-microporous aluminosilicate has an adsorption capacity of 0.2 ml/g at a relative water vapor pressure of 0.2, and thus is promising as an adsorbent for an adsorption heat-pump. 相似文献