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471.
Glezer A 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1940):1476-1494
Aerodynamic flow control effected by interactions of surface-mounted synthetic (zero net mass flux) jet actuators with a local cross flow is reviewed. These jets are formed by the advection and interactions of trains of discrete vortical structures that are formed entirely from the fluid of the embedding flow system, and thus transfer momentum to the cross flow without net mass injection across the flow boundary. Traditional approaches to active flow control have focused, to a large extent, on control of separation on stalled aerofoils by means of quasi-steady actuation within two distinct regimes that are characterized by the actuation time scales. When the characteristic actuation period is commensurate with the time scale of the inherent instabilities of the base flow, the jets can effect significant quasi-steady global modifications on spatial scales that are one to two orders of magnitude larger than the scale of the jets. However, when the actuation frequency is sufficiently high to be decoupled from global instabilities of the base flow, changes in the aerodynamic forces are attained by leveraging the generation and regulation of 'trapped' vorticity concentrations near the surface to alter its aerodynamic shape. Some examples of the utility of this approach for aerodynamic flow control of separated flows on bluff bodies and fully attached flows on lifting surfaces are also discussed. 相似文献
472.
Mustonen Ulla; Huurre Taina; Kiviruusu Olli; Haukkala Ari; Aro Hillevi 《Canadian Metallurgical Quarterly》2011,25(4):615
The purpose of this 16-year prospective follow-up study was to investigate the association between parental divorce in childhood and intimate relationship quality in adulthood. The mediating role of psychosocial resources (parent-child relationships at 16 years, self-esteem and social support at 32 years) in this association was also studied. All 16 year olds of one Finnish city completed questionnaires at school and were followed up by postal questionnaires at 32 years of age (n = 1,471). Results showed that women and men from divorced families were more often divorced or separated at the age of 32 years than those from nondivorced families. However, parental divorce was associated with poorer intimate relationship quality only among women. Women from divorced families also had poorer relationships with their father and mother in adolescence, and they had lower self-esteem and satisfaction with social support in adulthood than women from intact families. No such associations were found among men. The impact of parental divorce on intimate relationship quality among women was partially mediated by mother-daughter relationship, self-esteem, and satisfaction with social support. The mediating role of mother-daughter relationship was not direct, however, but was mediated via self-esteem and satisfaction with social support. Our findings indicate that parental divorce affects daughters more than sons. In the context of parental divorce, the mother-daughter relationship in adolescence is important for the development of later psychosocial resources and, via them, for intimate relationship quality. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
473.
474.
The ion exchange properties of sodium iron titanates, namely, NaFeTiO(4), Na(2)Fe(2)Ti(6)O(16) and iron-doped sodium nonatitanate were investigated. Conventional solid state and sol-gel methods were used in the synthesis of the sodium iron titanates. Structural characterization of the materials was performed with powder X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) and with inductively coupled plasma optical emission spectrometry (ICP-OES). Based on TG analyses, the novel iron-doped sodium nonatitanate was proven to be a member of the layered titanate family. The different sodium iron titanates were compared based on the efficiency in separating Ni from aqueous streams by conducting batch experiments with a batch factor of 1000 ml/g. Iron-doped sodium nonatitanate exhibited the best ion exchange performance compared to the other sodium iron titanates studied. It was found to be selective for nickel over potassium and showed 99% removal efficiency for Ni. 相似文献
475.
Electrical sintering of nanoparticle structures 总被引:1,自引:0,他引:1
Allen ML Aronniemi M Mattila T Alastalo A Ojanperä K Suhonen M Seppä H 《Nanotechnology》2008,19(17):175201
A method for sintering nanoparticles by applying voltage is presented. This electrical sintering method is demonstrated using silver nanoparticle structures ink-jet-printed onto temperature-sensitive photopaper. The conductivity of the printed nanoparticle layer increases by more than five orders of magnitude during the sintering process, with the final conductivity reaching 3.7 × 10(7)?S?m(-1) at best. Due to a strong positive feedback induced by the voltage boundary condition, the process is very rapid-the major transition occurs within 2?μs. The best obtained conductivity is two orders of magnitude better than for the equivalent structures oven-sintered at the maximum tolerable temperature of the substrate. Additional key advantages of the method include the feasibility for patterning, systematic control of the final conductivity and in situ process monitoring. The method offers a generic tool for electrical functionalization of nanoparticle structures. 相似文献
476.
Stark S Julkunen-Tiitto R Holappa E Mikkola K Nikula A 《Journal of chemical ecology》2008,34(11):1382-1391
We investigated latitudinal and regional variations in the composition and concentrations of foliar flavonoids and condensed
tannins in wild populations of white birch (Betula pubescens EHRH) in a large climatic transect in Finland. Concentrations of quercetin derivatives were correlated positively with latitude.
By contrast, the concentrations of apigenin and naringenin derivatives were correlated negatively with latitude. These compound-specific
latitudinal gradients compensated each other, resulting in no changes in the concentration of total flavonoids. Our results
thus demonstrate a qualitative, but not quantitative, latitude-associated gradient in the foliar flavonoids in white birch.
Due to higher antioxidant capacity of the quercetin derivatives in relation to other flavonoids, the qualitative change can
reflect higher adaptation to light in the north than south. An investigation on a regional scale in the northern boreal zone
showed that the temperature sum was correlated positively and soil P concentration was correlated negatively with the concentrations
of foliar flavonoid, while the concentration of condensed tannins was correlated with slope. The variation in concentrations
of flavonoids at large-scale geographical patterns is in line with the conjecture that foliar flavonoids are synthesized for
protection against photooxidative stress. 相似文献
477.
Ayla Kaya Betul Demirci Suleyman Doğu Muhittin Dinç 《International Journal of Food Properties》2017,20(11):2639-2644
The genus Stachys L. one of the largest genera of Lamiaceae and Stachys species are used by many people for the therapeutic value of their essential oils. In this study, water-distilled essential oil of three species of Stachys was analysed. The analysis was performed by using gas chromatography-flame ionisation detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) systems simultaneously. The major components found were hexadecanoic acid (23.7%), dodecanoic acid (11.3%), and caryophyllene oxide (10.7%) for S. sericantha P.H. Davis (endemic); α-pinene (53%), β-pinene (8.2%) for S. gaziantepensis M. Dinc and S. Do?u (endemic); Menthyl acetate (15.3%), isomenthone (15.0%), pulegone (10%), spathulenol (7.0%), and caryophyllene oxide (6.7%) for S. mardinensis (Post) R. Mill. 相似文献
478.
Animals have been slaughtered by humans since time immemorial. Over the last few generations attention has been focused on minimizing the animal's pain and suffering during slaughter. Based on the assumption that loss of consciousness due to electrical stunning combined with exsanguination is a humane technique of slaughter, this procedure has become one of the most widely employed methods in commercial meat production, being used in almost all species. In recent years, some shortcomings with this method of minimizing the animal's suffering have been noted. Electrical stunning is probably more akin to human electro-convulsive therapy (ECT) than to epilepsy, and some of the negative aspects of unmodified ECT may be present during electrical stunning, further questioning the use of electrical stunning in the slaughter of animals. 相似文献
479.
A number of techniques exist for microbiological sampling of food processing environments in food industries. In the present study the efficacies of nine sampling procedures for the recovery of Listeria monocytogenes from food contact surfaces, including a new sampling device consisting of a miniroller, were evaluated and compared. A stainless steel table was inoculated with L. monocytogenes strain 935 (serovar 4b, human origin) and L. monocytogenes strain 437/07 (serovar 1/2b, food origin), at 10(5) CFU/100 cm(2). L. monocytogenes strain 935 was best recovered with the minirollers (recovery of up to 6.27%), while poor recoveries (<0.30%) were obtained with the towel (one-ply composite tissue), alginate swab, metallic swab, and Petrifilm methods. In the case of L. monocytogenes strain 437/07 the replicate organism detection and counting (RODAC) ALOA contact plates yielded the best recoveries (4.15%), followed by the minirollers (up to 1.52%). Overall, recovery percentages with the minirollers were higher with stomacher homogenization than with Vibromatic agitation. The recovery percentages obtained for the Listeria strain of human origin were higher than those obtained with the food strain for all sampling procedures except Petrifilm and RODAC ALOA. With the miniroller device coated with wool fiber, the recovery of L. monocytogenes can be improved from 2 to 17 times over recoveries obtained with the sponge and cotton swab. This is the first report of a miniroller device for microbiological sampling in the available literature. The novel sampling procedure is convenient to apply on surfaces, is cost-effective, and results in better recovery of L. monocytogenes than do the conventional methods. 相似文献
480.
Meat texture and some biochemical characteristics that could influence meat tenderness were studied in rabbit loins. Rabbits from three synthetic lines were compared, lines V and A selected for litter size at weaning and line R selected for growth rate between weaning and slaughter time. The activities of cathepsins, collagen content and textural properties measured by Warner-Bratzler (WB) shear device and by the texture profile analyses (TPA) test were measured. Line R was more tender than line V and line A had an intermediate tenderness, Rabbit meat from line R had higher activity of cathepsins B and B + L, lower total collagen content and lower cohesiveness, springiness and chewiness, shear force and total work (area under the curve obtained with WB device) than line V. Line A had an intermediate texture between lines R and V. Our results show evidence of genetic variation between lines in rabbit meat tenderness. 相似文献