Monitoring Lactic Acid Fermentation in Media Containing Dandelion (Taraxacum officinale) by FTIR Spectroscopy

Fourier-transform infrared (FTIR) spectroscopy is considered to be a comprehensive and sensitive method for detection of molecular changes in cells and media. In the present study, FTIR spectroscopy was employed as an easy, rapid and reliable technique to evaluate the lactic fermentation of Lactobacillus casei on a model de Man, Rogosa and Sharpe (MRS) medium with or without the addition of dandelion extract (DE). Dandelion, due to its high content in fructans, can be used as an additional carbon source in lactic fermentation. Lactic fermentation in a dandelion extract, using the FTIR fingerprint as a qualitative and semi-quantitative assay for lactic acid production was monitored. Specific bands of carbohydrates in the fingerprint region (1200-900 cm-1) and their shifts indicated the hydrolysis and metabolism during fermentation. The band at 1336 cm-1 may be considered a sensitive marker for the identification of L. casei during fermentation, while the dandelion extract showed a unique characteristic peak at 1436 cm-1. The results proved that the species were detectable and that significant spectral differences existed between fermented samples in media with or without dandelion addition. Representative peaks of bacteria and dandelion appeared in the spectra of a mixture of bacteria and dandelion. The peaks were evident in the samples taken using the model MRS media from the beginning of fermentation as opposed to at the end of fermentation

CO adsorption on neutral iridium clusters

The adsorption of carbon monoxide on neutral iridium clusters in the size range of n = 3 to 21 atoms is investigated with infrared multiple photon dissociation spectroscopy. For each cluster size only a single v(CO) band is present with frequencies in the range between 1962 cm-1 (n = 8) and 1985 cm-1 (n = 18) which can be attributed to an atop binding geometry. This behaviour is compared to the CO binding geometries on clusters of other group 9 and 10 transition metals as well as to that on extended surfaces. The preference of Ir for atop binding is rationalized by relativistic effects on the electronic structure of the later 5d metals

3Rs in Education.

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Dynamic and wear study of an extremely bidisperse magnetorheological fluid

Acceso a la versión publicada en Smart Mater. Struct. 24(12) 127001 (http://iopscience.iop.org/0964-1726/24/12/127001)"This is an author-created, un-copyedited version of an article accepted for publication/published in Smart Materials and Structures. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0964-1726/24/12/127001."In this work the friction and wear properties of five magnetorheologicalfluids (MRFs)with varying compositions are investigated. Considering that many of the proposed applications for these fluids involve lubricated contact between mobile metal –metal or polymer– metal parts, the relationship between MR response and wear behavior appears to be of fundamental importance. One of the fluids(MR#1)contains only the iron microparticles and base oil; the second and third ones(MR#2 and MR#3) contain an anti-wear additive as well. The fourth one(MR#4)is a well known commercial MRF. Finally, MR#5 is stabilized by dispersing the iron particles in a magnetite ferrofluid. The MR response of the latter fluid is better(higher yield stress and post-yield viscosity)than that of the others. More importantly, it remains(and even improves)after the wear test: the pressure applied in the four-ball apparatus produces a compaction of the magnetite layer around the iron microparticles. Additionally, the friction coefficient is larger, which seems paradoxical in principle, but can be explained by considering the stability of MR#5 in comparison to the other four MRs, which appear to undergo partial phase separation during the test. In fact, electron and optical microscope observations confirm a milder wear effect of MR#5, with almost complete absence of scars from the steel test spheres and homogeneous and shallow grooves on them. Comparatively, MR#2, MR#3 and, particularly, MR#1 produce a much more significant wear.MINECO Ramón y Cajal Programme (RYC-2014-16901)MINECO FIS 2013-07666-C3-1-RCEI Biotic BS27.2015Junta de Andalucía, PE2012-FQM-069

Ultrafast interfacial carrier dynamics

Charge carrier dynamics at interfaces is of fundamental interest for a broad range of applications such as photovoltaics and optoelectronics. The interface between different materials can behave as a charge separating boundary but also control the recombination of electron hole pairs. The impact on the specific application can be completely contrastive and interfacial engineering is often necessary to develop the materials towards their typical designation. Femtosecond real time measurements provide relevant information of the ultrafast processes occurring at interfaces in inorganic or organic compounds and help to enhance the performance of the specific interface when incorporated into a functional device. ZnO is a promising semiconductor material intended for use as a charge transport electrode in low cost nano composite solar cells and may eventually replace the widely used colloidal TiO2 in such devices in the future [1]. Electrodes can be perpared as amp; 956;m thick films consisting of ordered crystalline ZnO nanorods [2] with a mean diameter much larger than their colloidal counterparts and thus allowing for a cross sectional potential field gradient [3]. This and also the absence of grain boundaries in nanorod layers is expected to improve the carrier transport properties in comparison to colloidal semiconductor films. However, ZnO based solar cells have not yet met the long standing efficiency values obtained with dye sensitized solar cells on the basis of TiO2. Charge separation at the heterogeneous dye ZnO interface is still poorly understood and interfacial carrier dynamics at TiO2 and ZnO nmstructured electrodes differ considerably in the femtosecond time window Fig. 1,2 . Perylene was used as a model sensitizer chromophore adsorbed to the semiconductor surface via a propionic or acrylic acid group where the latter acts as a spacer binding group. Fs transient absorption fs TA, Fig. 1 and time resolved two photon photoemission TR 2PPE Fig. 2 spectroscopy was applied for monitoring interfacial charge transfer using 20 fs laser pulses supplied by novel type low power NOPAs operating at 150KHz repetition rate. 40