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851.
Tamara Bakuradze Roman Lang Thomas Hofmann Herbert Stiebitz Gerhard Bytof Ingo Lantz Matthias Baum Gerhard Eisenbrand Christine Janzowski 《Molecular nutrition & food research》2010,54(12):1734-1743
Scope: Epidemiological studies suggest that coffee can reduce the risk of degenerative diseases such as diabetes type 2, cardiovascular disease and cancer. These beneficial effects have partly been attributed to the antioxidant activity of coffee. We determined composition and antioxidant potential of differentially roasted coffee extracts and investigated the impact of selected original constituents and roast products. Methods and results: Parameters studied were direct antioxidant activity (trolox equivalent antioxidant capacity/oxygen radical absorbing capacity), cellular reactive oxygen species (ROS) level, DNA damage and protein expression of NAD(P)H: quinone oxidoreductase, γ‐glutamylcysteine ligase and glutathione reductase in HT‐29/Caco‐2 cells at 24‐h incubation. All extracts showed distinct direct antioxidant activity: medium roasts>light roast AB1 (caffeoylquinic acid (CQA)‐rich Arabica Brazil extract); dark roast AB2 (N‐methylpyridinium (NMP)‐rich Arabica Brazil extract), and diminished t‐butylhydroperoxide‐induced ROS level in HT‐29 cells (AB2>medium roasts>AB1). NAD(P)H:quinone oxidoreductase 1 expression and γ‐glutamylcysteine ligase expression were distinctly induced by AB1 and 5‐CQA, but not by AB2 and NMP. 5‐CQA and caffeic acid exhibited highest trolox equivalent antioxidant capacity/oxygen radical absorbing capacity values (5‐CQA: 1.3/3.5 mM and caffeic acid: 1.3/3.9 mM trolox); ROS level was distinctly diminished by 5‐CQA (≥3 μM), catechol (30 μM) and trigonelline (≥30 μM), whereas menadione‐induced DNA damage in Caco‐2 cells was reduced by NMP compounds (1–30 μM). Conclusion: The results emphasize that both original constituents and roast products contribute to the cellular antioxidant effectiveness of coffee. 相似文献
852.
Laser Beam Build-Up Welding: Precision in Repair,Surface Cladding,and Direct 3D Metal Deposition 总被引:2,自引:0,他引:2
Steffen Nowotny Siegfried Scharek Eckhard Beyer Karl-Hermann Richter 《Journal of Thermal Spray Technology》2007,16(3):344-348
Surface coating, repair, and rapid design changes of high-value components and tools are demanding challenges of modern manufacturing
technology. In this field, advanced laser-based techniques are of outstanding importance for the related applications in mould
and tool, aircraft and aerospace, as well as automotive industry. Many laser cladding solutions have been transferred into
industrial series production within the last years. The motivations for the raising interest are given by the typical features
of the technology: on the base of closed CAD/CAM chains, a quick and comprehensive treatment even of complex shaped and highly
stressed components is possible. The heat input into the workpiece is less compared to TIG or PTA welding, although a metallurgical
bonding to the substrate is guaranteed. Furthermore, the precise material deposition even at small partial areas is an advantageous
characteristic. The coating materials include metal alloys (Co, Ni, Cu basis, Titanium, and steel), hard metals (e.g., WC/Co,
TiC, and VC with metallic binders), and oxide ceramics (Al2O3/TiO2). Typical base materials are steel, cast iron, and lightweight metal alloys based on Aluminum, Titanium, and Magnesium. The
accuracy of the produced 3D structures in the range of 0.1 mm is the highest possible in the group of welding techniques.
On the other hand, the available system technology (lasers, powder feeders and nozzles, CAD/CAM systems) permits a very easy
and successful integration of the laser technology into manufacturing systems. Examples of application are the surface protection
of lightweight automotive motor components, repair and quick modifications of metal forming tools as well as the complete
restoration of damaged blades and disks of aero engines and gas turbines. 相似文献
853.
854.
Adsorption of dissolved organic matter onto activated carbon--the influence of temperature, absorption wavelength, and molecular size 总被引:2,自引:0,他引:2
In this study, batch and column adsorption experiments with granular activated carbon (GAC) were carried out for removing dissolved organic matter (DOM) of a pond water at different water temperatures (5, 20, and 35 °C). The water was characterized before and after the adsorption step using UV/VIS spectroscopy and size-exclusion chromatography (SEC) combined with diode array detection (DAD). DOM breakthrough of GAC filters has been found to be slower at higher water temperatures, the DOM removal being most effective at 35 °C. UV/VIS spectra and SEC chromatograms of water samples treated at different water temperatures indicate that an increase in temperature especially supports the adsorption of small DOM molecules as well as molecules absorbing at higher wavelengths, specifying aromatic structures of DOM. SEC-DAD has been demonstrated to be an efficient method for characterizing DOM of natural waters and for detecting relative changes of DOM during the water treatment process. 相似文献
855.
Alternating current mode scanning electrochemical microscopy (AC-SECM) enables local detection of electrochemical surface activity without any redox mediator present in solution. Z-approach curves toward the substrate result in a negative feedback curve of the ac signal for insulating samples. On conducting samples, however, the shape of the feedback curve was found to be dependent on the ac perturbation frequency. Approach curves over a wide range of frequencies were performed, and the results were applied to interpret laterally resolved frequency-dependent measurements obtained with combined atomic force microscopy-AC-SECM (AFM-AC-SECM). For the first time, this frequency dependence of the signal was utilized to fine-tune the electrochemical contrast in lateral imaging in AC-SECM. An array of gold microelectrodes embedded in silicon nitride displaying significant changes in electrochemical activity as well as in topography was investigated using a bifunctional AFM-SECM tip with an integrated recessed ring microelectrode. Due to the unique geometrical conditions the electrochemical contrast between the conducting gold spots and the insulating SixNy is reversed, crosses zero, and inverts as a function of the applied ac frequency. 相似文献
856.
Thermodynamic analysis of a liquid-flooded Ericsson cycle cooler 总被引:1,自引:0,他引:1
Jason Hugenroth James Braun Eckhard Groll Galen King 《International Journal of Refrigeration》2007,30(7):1176-1186
A novel approach to implementing a gas Ericsson cycle heat pump was developed. The concept, termed a liquid-flooded Ericsson cooler (LFEC), uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. Analytical models of liquid-flooded compression and expansion processes were developed using ideal gas, constant specific heat, and incompressible liquid assumptions. Special considerations for use of positive displacement compressors with fixed volume ratios are detailed. The unique behavior of a liquid-flooded compressor was explored, including the discovery of an optimum liquid flooding rate that minimizes compression power. A computer model of the LFEC cycle was developed using ideal gas, incompressible liquid, and constant specific heat assumptions. The model was used for a thorough parametric study. The purpose of the study was to explore the feasibility of the concept, identify the optimum operating parameters, and to provide a basis for the design of an experimental system. 相似文献
857.
The impact of evaporator fouling and filtration on the performance of packaged air conditioners 总被引:1,自引:1,他引:0
The goal of the study presented in this paper was to evaluate the impact of different filter types on the performance of three typical packaged air conditioners under both clean and fouled conditions. In a companion paper, combinations of six different levels of filtration and four different coils were tested under clean and fouled conditions. From the tests, it was found that fouling has a relatively small impact on air-side effective heat transfer coefficient, but can have a large impact on coil pressure drop. Data from the experimental study were used in developing simulation models for the three packaged air conditioners. Simulations show that the equipment cooling capacity is reduced with fouling primarily because of a decrease in air flow due to the increased pressure drop. In most cases, EER (energy efficiency ratio) was reduced with fouling primarily due to increased fan power. However, the changes in EER were relatively small, in the range of 1–10%. Equipment having low efficiency filters had higher EER after fouling than equipment with high efficiency filters, because high efficiency filters result in significantly higher pressure drops than low efficiency filters. The impact of the evaporator side fan efficiency was found to be significant. The energy penalty associated with high efficiency filters was reduced greatly when fan efficiency increased. Although high efficiency filters cause higher energy penalties they provide considerably better air quality. The quantity of dust passing through the coil with an MERV14 filter was approximately 30 times less than the dust passing the coil with an MERV4 filter. This difference was doubled when the MERV14 filter was compared to a case with no filter in place. 相似文献
858.
Breakthrough behavior of granular ferric hydroxide (GFH) fixed-bed adsorption filters: modeling and experimental approaches 总被引:1,自引:0,他引:1
Breakthrough curves (BTC) for the adsorption of arsenate and salicylic acid onto granulated ferric hydroxide (GFH) in fixed-bed adsorbers were experimentally determined and modeled using the homogeneous surface diffusion model (HSDM). The input parameters for the HSDM, the Freundlich isotherm constants and mass transfer coefficients for film and surface diffusion, were experimentally determined. The BTC for salicylic acid revealed a shape typical for trace organic compound adsorption onto activated carbon, and model results agreed well with the experimental curves. Unlike salicylic acid, arsenate BTCs showed a non-ideal shape with a leveling off at c/c0 approximately 0.6. Model results based on the experimentally derived parameters over-predicted the point of arsenic breakthrough for all simulated curves, lab-scale or full-scale, and were unable to catch the shape of the curve. The use of a much lower surface diffusion coefficient D(S) for modeling led to an improved fit of the later stages of the BTC shape, pointing on a time-dependent D(S). The mechanism for this time dependence is still unknown. Surface precipitation was discussed as one possible removal mechanism for arsenate besides pure adsorption interfering the determination of Freundlich constants and D(S). Rapid small-scale column tests (RSSCT) proved to be a powerful experimental alternative to the modeling procedure for arsenic. 相似文献
859.
Ursula Palm Christiane Askari Uwe Hener Eckhard Jakob Claudia Mandler Martin Geßner Armin Mosandl Wilfried A. König Petra Evers und Ralph Krebber 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1991,192(3):209-213
Zusammenfassung 5-Alkyl-substituierte-Lactone finden sich als aromarelevante Substanzen in tierischen Fetten, aber auch in einigen Früchten. Vor kurzem gelang die erste direkte gaschromatographische Stereodifferenzierung einiger-Lactone an der chiralen Phase Oktakis(3-O-butyryl-2,6-di-O-pentyl)--cyclodextrin [4]. Es wird nun die Enantiomerentrennung der-Lactone bis zu den langkettigen Verbindungen-Trideca-(-C13-)- und-Tetradeca-(-C14-)-lacton aufgezeigt. Über optisch reine Referenzsubstanzen konnte die Elutionsfolge S(I), R(II) der drei wichtigsten aromarelevanten Vertreter dieser-Lactonklasse bestimmt werden. Die Enantiomerenverteilung der C8-, C10-, C12--Lactone im Wasserdampfdestillat verschiedener Milchprodukte (Milch, Sahne, Butter), in Margarine sowie im Kokosnußfleisch wurde exemplarisch mit Hilfe der HRGC, auch unter Einsatz der multidimensionalen Gaschromatographie (MDGC), untersucht. Es zeigten sich charakteristische, substratspezifische Enantiomerenverteilungen. Die Verteilungsmuster der untersuchten Spiegelbildisomeren aus Kokosnüssen unterschieden sich wesentlich von denen der Milchprodukte.
Stereoisomeric flavour compoundsXLVII. Direct chirospecific HRGC-analysis of natural -lactones
Summary 5-Alkylated-lactones are well known flavour compounds in animal fats and also some special kinds of fruit. Recently, the first direct stereo-differentiation of chiral-lactones was reported using Oktakis(3-O-butyryl-2,6-di-O-pentyl)--cyclodextrin as the chiral stationary phase [4]. The enantiomeric separation of-lactones up to the long-chain compounds-trideca-(-C13–) and-tetradeca-(-C14–)-lactone is demonstrated. By means of optically pure references, the order of elution S(I), R(II) was determined for the important flavour compounds-octa-,-deca-, and-dodecalactone. Analysis of the steam distillate of some dairy products (milk, cream, butter), of margarine and of coconut has been carried out, in order to yield the enantiomeric distribution of C8-, C10- and C12--lactones by HRGC and multidimensional gas chromatography. Characteristic and product-specific ratios of-lactone enantiomers are detected. The pattern of enantiomeric composition of-octa-,-deca-,-dodecalactone in coconuts differs completely from that found in the dairy products.相似文献
860.
Groebner AE Rubio-Aliaga I Schulke K Reichenbach HD Daniel H Wolf E Meyer HH Ulbrich SE 《Reproduction (Cambridge, England)》2011,141(5):685-695
Amino acids (AAs) are crucial for the developing conceptus prior to implantation. To provide insights into the requirements of the bovine embryo, we determined the AA composition of the uterine fluid. At days 12, 15, and 18 post-estrus, the uteri of synchronized pregnant and non-pregnant Simmental heifers were flushed for the analysis of 41 AAs and their derivatives by liquid chromatography-tandem mass spectrometry. The ipsilateral endometrium was sampled for quantitative PCR. In addition to a pregnancy-dependent increase of the essential AAs (P<0.01), we detected elevated concentrations for most non-essential proteinogenic AAs. Histidine (His) and the expression of the His/peptide transporter solute carrier 15A3 (SLC15A3) were significantly increased at day 18 of pregnancy in vivo. In addition, SLC15A3 was predominantly stimulated by trophoblast-derived interferon-τ in stroma cells of an in vitro co-culture model of endometrial cells. Our results show an increased concentration of AAs most likely to optimally provide the elongating pre-attachment conceptus with nutrients. 相似文献