Zoekresultaten

Chromatographic behavior of petanin in reversed-phase HPLC in mobile phases with a wide range of pH

The chromatographic behavior of petanin, petunidin-3-O-[6-O-(4-O-(E)-para-coumaroyl-O-α-rhamnopyranosyl)-β-glucopyranoside]-5-O-β-glucopyranoside, is studied for the first time under conditions of reversed-phase high performance liquid chromatography in mobile phases with different pH values. The relationship between chromatographic behavior (retention time and peak efficiency) and transitions between different forms of anthocyanins is discussed. Analysis of the data obtained in the 2 to 6.5 range of mobile pH phases, the absorption spectra of petanin, and the results from studying the effect of adding tetrabutylammonium bromide to the mobile phase shows that increasing the pH results in the formation of uncharged and anionic forms, in addition to the pseudobase form.

Photovoltaic efficiency of anthocyanins in dye-sensitized solar cells (DSSCs)

Experimental analysis of radially resolved dynamic inflow effects due to pitch steps

The dynamic inflow effect denotes the unsteady aerodynamic response to fast changes in rotor loading due to a gradual adaption of the wake. This does lead to load overshoots. The objective of the paper was to increase the understanding of that effect based on pitch step experiments on a 1.8 m diameter model wind turbine, which are performed in the large open jet wind tunnel of ForWind – University of Oldenburg. The flow in the rotor plane is measured with a 2D laser Doppler anemometer, and the dynamic wake induction factor transients in axial and tangential direction are extracted. Further, integral load measurements with strain gauges and hot-wire measurements in the near and close far wake are performed. The results show a clear gradual decay of the axial induction factors after a pitch step, giving the first direct experimental evidence of dynamic inflow due to pitch steps. Two engineering models are fitted to the induction factor transients to further investigate the relevant time constants of the dynamic inflow process. The radial dependency of the axial induction time constants as well as the dependency on the pitch direction is discussed. It is confirmed that the nature of the dynamic inflow decay is better described by two rather than only one time constant. The dynamic changes in wake radius are connected to the radial dependency of the axial induction transients. In conclusion, the comparative discussion of inductions, wake deployment and loads facilitate an improved physical understanding of the dynamic inflow process for wind turbines. Furthermore, these measurements provide a new detailed validation case for dynamic inflow models and other types of simulations.

Building Biomimicry Bridges - a toolbox for biomimicry practitioners

Few people I know act likea magnet in the way Laura does. If you hear her speak, see her move, enjoy her smile - you can't help but want to be a part of what makes her heart beat faster. She radiates passion for her dream topic biomimicry and before you know it you're caught in that dream. From the day I met her, I was captivated by her enthusiasm and knowledge about this topic. In fact, meeting Laura made me decide to join the university as I thought: if people like Laura work at THUAS, I want to be a part of this organization'. Over the years I have seen her finish the Msc in biomimicry at Arizona State University followed by a PhD at TUDelft. And all that next to her full time job as a teacher. It's only a miracle that she still found the time to go outdoors and be in Nature. But luckily, she did as this is what nourishes her - and that nourishment is brought into the classroom affecting generations of students. I am very proud of how she builds her tribe just like Nature does; grassroots from the bottom up, not supported but also not inhibited by formal structures. In that way she truly acts as a bridge helping others to tap into Nature's wisdom. This morning I harvested the remaining vegetables from my garden and turned them into lunch. It's the second year I grow vegetables and it feels like I am only at the beginning of learning to collaborate with Nature. In Spring and Summer, Ihave witnessed in awe how seeds become seedlings which then grow into mature plants carrying fruit. The sheer wonder of Nature never ceases to amaze me, and my garden is only an attempt to be more aware of seasonal rhythms. It's Autumn right now, a time of year that invites us to go inside, reflect and let go of old baggage that no longer serves us. We'll be approaching the stage of wintering soon in which our inner journey will benefit from the darkness of wintertime introspection, along with the space to process the old, integrate learnings, and then germinate the new. Over the course of her career, Laura has gone through these seasonal cycles - reinventing herself in the past decade as a teacher, researcher and regenerative leader. One of Laura's many qualities is that she embodies three leadership characteristics derived from Nature. First, she acknowledges the importance of interconnection. Many times, we think of Nature as being separate from us, but in reality we humans are Nature. Connection with Nature enables us to think within systems and understand that we can't direct the system, but instead we're all part of multiple systems. Second, sensing the system and our part in it builds resilience. Even if things don't go as we expected or imagined, rather than reacting, we can step back and engage with more insight. Laura's adaptability to a system's needs while spotting opportunities to crack it open, is admirable. As the system is always in evolution, so is she - remarkably receptive to change even in the final stages of her career. Third, Laura creates space for people to develop and thrive, acting as multipliers of her vision and love for the natural world. In her leadership she embodies the ideal elder while being able to perceive the world through the eyes of a child - with continuous wonder for how life unfolds. This book is a bricolage of Laura's post-doc research conducted the past two years. In it you will find an array of fascinating reads and tools that help you deepen your practice as a biomimicry professional. The book is a community effort integrating tools Laura has co-created with her ecosystem as well as more in-depth readings written by some of the talents she has nourished over time. I wish for you to enjoy this careful curation of both practical as well as more conceptual contributions. May it inspire your own thriving in bringing Nature based wisdom to the core of our daily lives.

Oxidative Modifications of Proteins and Lipids of Dried Semen, Urine, and Saliva Stains as a Function of Age in Forensic Context

Knowledge of the time of deposition is pivotal in forensic investigations. Recent studies show that changes in intrinsic fluorescence over time can be used to estimate the age of body fluids. These changes have been attributed to oxidative modifications caused by protein–lipid interactions. This pilot study aims to explore the impact of these modifications on body fluid fluorescence, enhancing the protein–lipid model system for age estimation. Lipid and protein oxidation markers, including protein carbonyls, dityrosine, advanced glycation end-products (AGEs), malondialdehyde (MDA), and 4-hydroxynonenal (HNE), were studied in aging semen, urine, and saliva over 21 days. Surface plasmon resonance imaging (SPRi), enzyme-linked immunosorbent assay (ELISA), and fluorescence spectroscopy were applied. Successful detection of AGE, dityrosine, MDA, and HNE occurred in semen and saliva via SPRi, while only dityrosine was detected in urine. Protein carbonyls were measured in all body fluids, but only in saliva was a significant increase observed over time. Additionally, protein fluorescence loss and fluorescent oxidation product formation were assessed, showing significant decreases in semen and saliva, but not in urine. Although optimization is needed for accurate quantification, this study reveals detectable markers for protein and lipid oxidation in aging body fluids, warranting further investigation.

Current status and grand challenges for small wind turbine technology

While modern wind turbines have become by far the largest rotating machines on Earth with further upscaling planned for the future, a renewed interest in small wind turbines (SWTs) is fostering energy transition and smart grid development. Small machines have traditionally not received the same level of aerodynamic refinement as their larger counterparts, resulting in lower efficiency, lower capacity factors, and therefore a higher cost of energy. In an effort to reduce this gap, research programs are developing worldwide. With this background, the scope of the present study is 2-fold. In the first part of this paper, an overview of the current status of the technology is presented in terms of technical maturity, diffusion, and cost. The second part of the study proposes five grand challenges that are thought to be key to fostering the development of small wind turbine technology in the near future, i.e. (1) improving energy conversion of modern SWTs through better design and control, especially in the case of turbulent wind; (2) better predicting long-term turbine performance with limited resource measurements and proving reliability; (3) improving the economic viability of small wind energy; (4) facilitating the contribution of SWTs to the energy demand and electrical system integration; (5) fostering engagement, social acceptance, and deployment for global distributed wind markets. To tackle these challenges, a series of unknowns and gaps are first identified and discussed. Based on them, improvement areas are suggested, for which 10 key enabling actions are finally proposed.