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101.
Self-assembled organic monolayers on gold nanoparticles: A study by sum-frequency generation combined with UV-vis spectroscopy 总被引:2,自引:0,他引:2
We use sum-frequency generation spectroscopy (SFG) in the infrared 2800-3000 cm−1 spectral range and UV-vis spectroscopy (transmission) in the 450-650 nm spectral range in order to characterize vibrational and electronic properties of various interfaces composed of organic monolayers adsorbed on gold nanoparticles (AuNPs) with 19 nm average diameter. SFG signal is observed for AuNPs films deposited on glass substrates using the following silane intermediates: 3-(aminopropyl) triethoxysilane and 3-(mercaptopropyl) trimethoxysilane. The density of AuNPs and their aggregates are measured with a scanning electron microscope. For the samples showing a strong well-defined surface plasmon resonance (SPR), we also observe an enhancement of their non-linear optical properties. Furthermore, the SFG measurements show that 1-dodecanethiol films are rather well ordered on specific AuNPs substrates. In this way, the presence of the SFG signal, which comes from both the bulk electronic s-d interband transition and the vibrational states of the adsorbed molecules, depends on a SPR process. This phenomenon is evidenced on the AuNPs by the incident visible beam located at 532 nm, i.e. near the SPR energy maximum of these interfaces. These results open the door to experiments involving macromolecular and biological materials networks deposited on ultrathin metal electrodes in a controlled electrochemical environment. 相似文献
102.
The shield that never was: Societies with single-peaked preferences are more open to manipulation and control 总被引:1,自引:0,他引:1
Much work has been devoted, during the past 20 years, to using complexity to protect elections from manipulation and control. Many “complexity shield” results have been obtained—results showing that the attacker’s task can be made NP-hard. Recently there has been much focus on whether such worst-case hardness protections can be bypassed by frequently correct heuristics or by approximations. This paper takes a very different approach: We argue that when electorates follow the canonical political science model of societal preferences the complexity shield never existed in the first place. In particular, we show that for electorates having single-peaked preferences, many existing NP-hardness results on manipulation and control evaporate. 相似文献
103.
104.
Brand Serge; Gerber Markus; Pühse Uwe; Holsboer-Trachsler Edith 《Canadian Metallurgical Quarterly》2010,17(2):114
A cognitive mediation model was examined to find out how stress, depression, and hypomania precipitate the occurrence of dysfunctional sleep-related cognitions, which in turn lead to insomnia. A total of 862 participants (639 women, 223 men; M age: 24.67 years, SD = 5.91) completed a series of self-report questionnaires assessing perceived stress, depression, hypomania, dysfunctional sleep-related cognitions, and insomnia. Compared to men, women reported higher levels of stress, depression, and insomnia. Women also suffered from more dysfunctional sleep-related cognitions. All variables were intercorrelated. Structural equation analyses showed that the relationship between stress and insomnia was largely mediated by dysfunctional sleep-related cognitions. Links between depression and insomnia were found to be weak when controlled for stress and dysfunctional sleep-related cognitions. The findings support a cognitive model of insomnia. Stress must be seen as a precipitating factor in the onset and maintenance of insomnia. Consequently, competencies to deal with dysfunctional sleep-related cognitions should be fostered in stress management programs. In turn, stress management should be a primary focus in the treatment of insomnia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
Fama Rosemary; Sullivan Edith V.; Shear Paula K.; Cahn-Weiner Deborah A.; Marsh Laura; Lim Kelvin O.; Yesavage Jerome A.; Tinklenberg Jared R.; Pfefferbaum Adolf 《Canadian Metallurgical Quarterly》2000,14(1):29
This study examined the relationships between regional brain volumes and semantic, phonological, and nonverbal fluency in 32 participants with Alzheimer's disease (AD). Object but not animal semantic fluency correlated with frontal and temporal gray matter volumes. Phonological fluency was not significantly associated with any brain volume examined. Nonverbal fluency was selectively associated with bilateral frontal gray matter volumes. Hippocampal volumes, although markedly reduced in these patients, were not related to any of the fluency measures. Results lend evidence to the importance of the frontal lobes in the directed generation of nonverbal and verbal exemplars by AD patients. Furthermore, both left and right-hemisphere regions contribute to the generation of verbal and nonverbal exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
Cerebellar volume decline in normal aging, alcoholism, and Korsakoff's syndrome: Relation to ataxia.
Sullivan Edith V.; Deshmukh Anjali; Desmond John E.; Lim Kelvin O.; Pfefferbaum Adolf 《Canadian Metallurgical Quarterly》2000,14(3):341
The authors used magnetic resonance imaging to measure gray and white matter volumes in cerebellar hemispheres and 4 vermian regions in 61 normal control (NC) men aged 23–72 years, 25 men with uncomplicated alcoholism (ALC), and 8 men and 1 woman with alcoholic Korsakoff's syndrome (KS). NC and ALC took quantitative gait and balance tests. Gray but not white matter volume declined with normal age in both hemispheres and anterior–superior vermis. ALC had gray but not white matter cerebellar hemisphere volume deficits, whereas KS had deficits in both tissue types. ALC and KS had gray and white matter volume deficits in anterior superior but not posterior inferior vermis. ALC had a 1 SD ataxia deficit, significantly and selectively correlated with white matter volume in anterior superior vermis. Regional distribution but not severity of cerebellar volume deficits is similar in alcoholic individuals whether or not complicated by KS and relates to ataxia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Fundamental study on the effect of hydrostatic pressure treatment on the bread-making performance of oat flour 总被引:2,自引:2,他引:0
Edith K. Hüttner Fabio Dal Bello Elke K. Arendt 《European Food Research and Technology》2010,230(6):827-835
The use of sourdough in wheat and rye breads has been extensively studied; however, little is known about its potential effect
when baking oat bread. Consequently, the impact of sourdough on oat bread quality was investigated. Two different sourdoughs
were prepared from wholegrain oat flour without the addition of starter cultures, by continuous propagation at 28 (SD 28)
or 37 °C (SD 37) until the composition of the lactic acid bacteria remained stable. The dominant LAB were identified by sequence
analysis of the 16S rDNA isolated from pure cultures. LAB from SD 28 belonged to the species Leuconostoc argentinum, Pedicoccus pentosaceus and Weissella cibaria, while Lactobacillus coryniformis dominated SD 37. The isolated LAB were further used as starter cultures for the production of oat sourdoughs. Fundamental
rheology revealed softening of the sourdoughs compared to non-acidified and chemically acidified controls, which could not
be attributed to proteolytic activity. Incorporation of oat sourdough into an oat bread recipe resulted in significantly increased
loaf-specific volume as well as improved texture, independent of addition level or sourdough type. Overall, the results of
this study show that sourdoughs containing lactic acid bacteria isolated from oats have the potential to enhance oat bread
quality. 相似文献
108.
Anyamanee Chaiprasongsuk Zorica Janjetovic Tae-Kang Kim Cynthia J. Schwartz Robert C. Tuckey Edith K. Y. Tang Chander Raman Uraiwan Panich Andrzej T. Slominski 《International journal of molecular sciences》2020,21(24)
Lumisterol (L3) is a stereoisomer of 7-dehydrocholesterol and is produced through the photochemical transformation of 7-dehydrocholesteol induced by high doses of UVB. L3 is enzymatically hydroxylated by CYP11A1, producing 20(OH)L3, 22(OH)L3, 20,22(OH)2L3, and 24(OH)L3. Hydroxylumisterols function as reverse agonists of the retinoic acid-related orphan receptors α and γ (RORα/γ) and can interact with the non-genomic binding site of the vitamin D receptor (VDR). These intracellular receptors are mediators of photoprotection and anti-inflammatory activity. In this study, we show that L3-hydroxyderivatives significantly increase the expression of VDR at the mRNA and protein levels in keratinocytes, both non-irradiated and after UVB irradiation. L3-hydroxyderivatives also altered mRNA and protein levels for RORα/γ in non-irradiated cells, while the expression was significantly decreased in UVB-irradiated cells. In UVB-irradiated keratinocytes, L3-hydroxyderivatives inhibited nuclear translocation of NFκB p65 by enhancing levels of IκBα in the cytosol. This anti-inflammatory activity mediated by L3-hydroxyderivatives through suppression of NFκB signaling resulted in the inhibition of the expression of UVB-induced inflammatory cytokines, including IL-17, IFN-γ, and TNF-α. The L3-hydroxyderivatives promoted differentiation of UVB-irradiated keratinocytes as determined from upregulation of the expression at the mRNA of involucrin (IVL), filaggrine (FLG), and keratin 14 (KRT14), downregulation of transglutaminase 1 (TGM1), keratins including KRT1, and KRT10, and stimulation of ILV expression at the protein level. We conclude that CYP11A1-derived hydroxylumisterols are promising photoprotective agents capable of suppressing UVB-induced inflammatory responses and restoring epidermal function through targeting the VDR and RORs. 相似文献
109.
Aouni El-Hajje Elizabeth C. Kolos Jun Kit Wang Saeed Maleksaeedi Zeming He Florencia Edith Wiria Cleo Choong Andrew J. Ruys 《Journal of materials science. Materials in medicine》2014,25(11):2471-2480
The elastic modulus of metallic orthopaedic implants is typically 6–12 times greater than cortical bone, causing stress shielding: over time, bone atrophies through decreased mechanical strain, which can lead to fracture at the implantation site. Introducing pores into an implant will lower the modulus significantly. Three dimensional printing (3DP) is capable of producing parts with dual porosity features: micropores by process (residual pores from binder burnout) and macropores by design via a computer aided design model. Titanium was chosen due to its excellent biocompatibility, superior corrosion resistance, durability, osteointegration capability, relatively low elastic modulus, and high strength to weight ratio. The mechanical and physical properties of 3DP titanium were studied and compared to the properties of bone. The mechanical and physical properties were tailored by varying the binder (polyvinyl alcohol) content and the sintering temperature of the titanium samples. The fabricated titanium samples had a porosity of 32.2–53.4 % and a compressive modulus of 0.86–2.48 GPa, within the range of cancellous bone modulus. Other physical and mechanical properties were investigated including fracture strength, density, fracture toughness, hardness and surface roughness. The correlation between the porous 3DP titanium-bulk modulus ratio and porosity was also quantified. 相似文献
110.
Luz M. Ramos-Ponce Mireille Vega Georgina C. Sandoval-Fabián Edith Colunga-Urbina Nagamani Balagurusamy Francisco J. Rodriguez-Gonzalez Juan Carlos Contreras-Esquivel 《Food science and biotechnology》2010,19(3):683-689
A colorimetric method for quantitative measurement of free amino groups of water soluble chitin derivatives is described.
The method utilizes genipin as a natural and specific reagent for determining the concentration of free amino groups in samples
of water soluble chitin derivatives. The blue color adduct (complex) formed during genipin reaction with free amino groups
was measured at about 589 nm and Beer-Lambert’s law obeyed over the concentration range of 50 to 300 mg/L. Parameters of analytical
conditions were considered and kept constant during the experimental procedure. Highly acetylated water soluble chitin derivatives
can be differentiated from water soluble chitosan using this genipin method. The colorimetric method with genipin was proved
to be a rapid and efficient technique to determine the free amino groups in water soluble chitin derivatives. This method
can also be applied for the detection of the enzymatic activity of chitindeacetylase. 相似文献