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71.
Decision makers often have to learn from experience. In these situations, people must use the available feedback to select the appropriate decision strategy. How does the ability to select decision strategies on the basis of experience change with age? We examined younger and older adults' strategy selection learning in a probabilistic inference task using a computational model of strategy selection learning. Older adults showed poorer decision performance compared with younger adults. In particular, older adults performed poorly in an environment favoring the use of a more cognitively demanding strategy. The results suggest that the impact of cognitive aging on strategy selection learning depends on the structure of the decision environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
Joydeep?Ray William?MacNaughtan Peng?Siong?Chong Josélio?Vieira Bettina?WolfEmail author 《Journal of the American Oil Chemists' Society》2012,89(3):437-445
The formulation of reduced fat chocolate has been of interest to the confectionery industry for a considerable time. It presents
a challenge, as fat reduction strategies are often accompanied by poor quality of the formulated product due to an increased
viscosity of the molten chocolate. This causes difficulties during processing and poor sensory properties of the final product.
The addition of limonene to chocolates leads to fat reduced chocolates that are less hard and have a lower melt viscosity.
This study was undertaken to shed light on the changes produced by the addition of limonene on the crystallization and microstructure
of cocoa butter. Based on evidence obtained by X-ray diffraction, differential scanning calorimetry and polarized light microscopy,
it is proposed that the presence of limonene enhances the production of lower polymorphic forms on cooling but accelerates
the transformation to more stable polymorphic forms. This is demonstrated in the transformation of the α and β′IV forms in cocoa butter to form βV at early storage times (t = 0–1 week), and the transformation to form βVI at times >2–3 weeks at 20 °C. There is a complex but marked effect on crystal size, mainly at early storage times. 相似文献
73.
Bettina?C?mmererEmail author Katharina?Chodakowski Claudia?Gienapp Laura?Wohak Andrea?Hartwig Lothar?W.?Kroh 《European Food Research and Technology》2012,234(4):663-670
High molecular weight Maillard reaction products (melanoidins) are described to possess metal-chelating properties. Whereas
in food systems, this ability contributes to antioxidant properties, the consequences on biological systems are not quite
clear. The study was aimed to evaluate the implication of metal complexation by melanoidins on DNA damage. Melanoidins prepared
with d-glucose and different l-amino acids under water-free reaction conditions were charged with cupric ions. The effect on isolated DNA was investigated
by the PM2 assay and on cellular systems in the human colon carcinoma cell line HCT-116 by alkaline unwinding. Independent
of the amino acid composition, pure melanoidins (MW >14 kDa) did not cause significant DNA damage. By charging melanoidins
with Cu2+ ions, a considerable DNA strand breaking activity was detectable, which was again amplified in an oxidative milieu (addition
of hydrogen peroxide). Since Cu2+ normally does not provoke the formation of reactive oxygen species (ROS) via Fenton-type reaction, the results obtained have
to be attributed to reducing properties of melanoidins. Thus, in melanoidin–copper complexes redox cycling may take place
leading to Cu+ which subsequently undergoes Fenton-type and Haber–Weiss reactions. As a consequence, ROS are formed, which may explain the
generation of DNA strand breaks. 相似文献
74.
Dietary exposure to benzoxazinoids enhances bacteria‐induced monokine responses by peripheral blood mononuclear cells
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75.
The total antioxidant activity of coffee beverages was measured with stabilized radical EPR spectroscopy. Depending on which stabilized radical is used, Fremy's salt (potassium nitrosodisulphonate) or 2,2,6,6-tetramethyl-1-piperidin-1-oxyl (TEMPO) values can differ significantly. For the determination of antioxidant activity of Maillard reaction products in coffee, TEMPO appears to be the better radical marker. Thus the contribution of both main antioxidant active compounds (polyphenols, melanoidins) whose ratio varies with roasting conditions could be estimated. During storage experiments of coffees brews changes in antioxidant action are found to be time dependent. The content of chlorogenic acids increased significantly at higher storage temperatures, probably caused by a release from polymer structures. Additional antioxidant capacity of coffee melanoidins seems to be strongly influenced by atmospheric oxygen. The higher roasted sample is less vulnerable than medium or light roasted coffee. Investigations with model systems showed that among all coffee constituents the carbohydrates are mainly responsible for the formation of oxygen scavenging substances. 相似文献
76.
Brock NL Tudzynski B Dickschat JS 《Chembiochem : a European journal of chemical biology》2011,12(17):2667-2676
The fungus Fusarium fujikuroi IMI58289 emits a complex pattern of volatile terpenoids including two major compounds, the sesquiterpene alcohol α-acorenol and the diterpene ent-kaurene. ent-Kaurene is the precursor for the phytohormone gibberellic acid (GA(3)) and is produced from geranylgeranyl diphosphate (GGPP) via ent-copalyl diphosphate by the bifunctional ent-copalyl diphosphate/ent-kaurene synthase (CPS/KS). Several structurally related diterpenes were identified as side products of the CPS/KS. Deletion of the cps/ks gene or the whole GA(3) biosynthetic gene cluster resulted in completely abolished diterpene production. Mutants with deletions of the cytochrome P450 monooxygenase gene P450-4, which is responsible for the three oxidation steps from ent-kaurene to ent-kaurenoic acid en route to GA(3), accumulate diterpene hydrocarbons. Feeding with [6,6,6-(2) H(3)] mevalonolactone gave insights into the stereochemistry of the GGPP cyclisation, which operates with a chair-chair-"antipodal" fold. A rational biosynthetic scheme for all identified sesquiterpenes demonstrated their formation from farnesyl diphosphate (FPP) via three alternative initial cyclisations. Genome sequencing revealed the presence of five putative sesquiterpene synthase genes in the F. fujikuroi genome. The structures of several trace compounds from other classes have been identified as new natural products; these were delineated from their mass spectra and unambiguously assigned by comparison to synthetic references. 相似文献
77.
In this review, synthetic strategies and the development of environmentally benign methods for the production of economically important vitamins, carotenoids, and nutraceuticals used as food and feed supplements are illustrated by selected examples. The application of efficient catalytic transformations in multi-step chemical syntheses of such natural products enables technically feasible and cost-effective processes. For the preparation of fat-soluble (isoprenoid) vitamins A and E and the water-soluble vitamin (+)-biotin, homogeneous metal catalysis, including enantioselective transformations, heterogeneous and enzymatic catalysis serve as key methodologies. In the area of carotenoids, general building concepts and coupling methods for the total synthesis of beta-carotene and astaxanthin are discussed. Biotechnological methods and isolation from natural sources are also employed successfully, as exemplified for the xanthophyll lutein and the antioxidant (-)-epigallocatechin gallate. Lastly, key steps of the chemical synthesis of the polyphenol resveratrol are highlighted. 相似文献
78.
79.
Strain analysis of solid wood and glued laminated timber members by close range photogrammetry. The assumption of critical fracture mechanics parameters for the evaluation of the load‐bearing safety of structural units of full and board laminated timber in loaded areas and disturbance ranges the use of fracture mechanics is required. Realistic parameters can be gained only from experimental investigations that are transferred to the determination of the crack opening and the crack length with subsequent FE‐simulation. Due to the insufficient appropriation of measured data gained by tactile position encoders in conventional measuring procedures it is advisable to investigate crack growth with the help of the photogrammetry. Using the developed measuring system it is now possible to measure the crack geometry exactly for the determination of fracture mechanics parameters. Additionally a complete picture of the local deformations and the validity of a test can be improved considerably by the possibility of the varying number of discrete measuring points. 相似文献
80.
Frederik J. Hansen Zhiyuan Wu Paul David Anke Mittelstdt Anne Jacobsen Malgorzata J. Podolska Kenia Ubieta Maximilian Brunner Dina Kouhestani Izabela Swierzy Lotta Roßdeutsch Bettina Klsch Isabella Kutschick Susanne Merkel Axel Denz Klaus Weber Carol Geppert Robert Grützmann Alan Bnard Georg F. Weber 《International journal of molecular sciences》2022,23(9)
Immunotherapy has become increasingly important in the treatment of colorectal cancer (CRC). Currently, CD73, also known as ecto-5′-nucleotidase (NT5E), has gained considerable interest as a potential therapeutic target. CD73 is one of the key enzymes catalyzing the conversion of extracellular ATP into adenosine, which in turn exerts potent immune suppressive effects. However, the role of CD73 expression on various cell types within the CRC tumor microenvironment remains unresolved. The expression of CD73 on various cell types has been described recently, but the role of CD73 on B-cells in CRC remains unclear. Therefore, we analyzed CD73 on B-cells, especially on tumor-infiltrating B-cells, in paired tumor and adjacent normal tissue samples from 62 eligible CRC patients. The highest expression of CD73 on tumor-infiltrating B-cells was identified on class-switched memory B-cells, followed by naive B-cells, whereas no CD73 expression was observed on plasmablasts. Clinicopathological correlation analysis revealed that higher CD73+ B-cells infiltration in the CRC tumors was associated with better overall survival. Moreover, metastasized patients showed a significantly decreased number of tumor-infiltrating CD73+ B-cells. Finally, neoadjuvant therapy correlated with reduced CD73+ B-cell numbers and CD73 expression on B-cells in the CRC tumors. As promising new immune therapies are being developed, the role of CD73+ B-cells and their subsets in the development of colorectal cancer should be further explored to find new therapeutic options. 相似文献