SnO2 “Russian Doll” Octahedra Prepared by Metalorganic Synthesis: A New Structure for Sub‐ppm CO Detection

Micrometer‐sized hierarchical Sn₃O₂(OH)₂ octahedra, which are self‐assembled one inside the other, resembling “Russian doll” organization, have been obtained by a metalorganic approach. This synthesis is based on the controlled hydrolysis of [Sn(NMe₂)₂]₂ in the presence of an alkylamine ligand in an organic solvent (THF). The water content of the medium proved to be a key parameter for the formation of these multi‐walled octahedra. The resultant structures have been used as gas‐sensitive layers on micromachined silicon devices. During in situ heating, Sn₃O₂(OH)₂ is oxidized to SnO₂ while retaining the initial morphology. The sensors present outstanding dynamic responses at very low CO concentrations (7 % and 67 % resistance variation to 0.25 and 20 ppm CO, respectively, at an operating temperature of 500 °C). This superior gas‐sensing performance is closely related to the unique microstructure of the SnO₂ multi‐walled octahedra.     

A Combined Crystallographic and Theoretical Study Explains the Capability of Carboxylic Acids to Adopt Multiple Binding Modes in the Active Site of Carbonic Anhydrases

Carboxylates are the least investigated class of inhibitors of carbonic anhydrases (CAs). Here we explain the versatility of binding of these molecules to CAs by examining a new adduct of hCA II with N‐carboxymethyl‐saccharin.     

Fully reversible procedure for silver staining improves densitometry of complex mixtures of biopolymers resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis

Due to its high sensitivity, silver staining is a widely popular method for the revelation of biopolymers separated by both native and denaturing electrophoresis. A step-by-step method for the destaining and restaining of overdeveloped/overloaded silver-stained bands is described that is applicable to both proteins and nucleic acids. The procedure significantly improves densitometric analysis of gels that have been silver stained with either commercial kits or solutions made in-house. The method permits reproducible densitometry of silver-stained gels and allows quantification of both main and minor components in complex mixture of molecules resolved on the same gel slab. All steps may be interrupted and are readily reversible, allowing for facile densitometric analyses and photographic recording under optimized conditions. Furthermore, common artifacts such as differential staining of the two gel surfaces, localized uneven yellow-ochre background, and the presence of fold marks and fingerprints can be easily removed.     

Advanced pulse calibration techniques for the quantitative analysis of TG–FTIR data

Two different pulse calibration techniques to estimate the total quantities of evolved gaseous substances formed in thermogravimetric (TG)–FTIR runs were compared and assessed. A gas-pulse calibration method was based on the use of a specific device able of sending a known quantity of a gaseous compound of interest to the FTIR analyzer. A second calibration method was based on the vaporization in the TG analyzer of liquid solutions of the compound of interest. Data obtained by these techniques were compared to those from conventional concentration-based calibration. The results confirmed the reliability of pulse calibration techniques to obtain quantitative data on evolved gaseous products in TG–FTIR applications. Moreover, both the gas-pulse and the vaporization-based calibration techniques proved to have several advantages with respect to conventional techniques. Among these are the need of a more limited number of standards and no need for online gas dilution systems.     

Optically pure beta-substituted beta-hydroxy aspartates as glutamate transporter blockers

A short asymmetric synthesis of optically pure beta-substituted beta-hydroxy aspartates is described. The key step is an aldol reaction between a glycine enolate derived from an oxazinone intermediate used as chiral auxiliary and various alpha-keto esters. Excellent diastereomeric excesses are obtained.     

New flavonol tetraglycosides from Astragalus caprinus

A new flavonol tetraglycoside, together with four acylated derivatives, were isolated from the leaves of Astragalus caprinus. Their structures were elucidated by spectroscopic methods, mainly 2D NMR, as kaempferol-3-O-[[beta-D-xylopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->6)][alpha-L-rhamnopyranosyl(1-->2)]]-beta-D-galactopyranoside (1), its 3(Gal)-p-coumaric (2) and 3(Gal)-ferulic (3) esters, and its 4(Gal)-p-coumaric (4) and 4(Gal)-ferulic (5) esters.     

FT-IR spectral imaging of blood vessels reveals protein secondary structure deviations induced by tumor growth

Vascular basement membrane remodeling is involved in tumor angiogenesis to enable tumor invasion and growth. FT-IR spectral imaging was used to determine changes in tumor blood vessels to reveal protein secondary structure in Rag-gamma immuno-deficient mice sacrificed 14 and 21 days after subcutaneous glioma implantation. For the oldest blood capillaries (diameter >20 microns), tumor growth induced a decrease in triple-helix content (1638 cm(-1); -7.3%; P < 0.05) and an increase in beta turns (1666 and 1615 cm(-1); +4%; P < 0.01). These protein-structure alterations, mainly from type IV collagen, reflected the high angiogenic stress of growing tumors. We propose to use these molecular markers of vascular basement membrane protein alterations for gradation of solid tumors by FT-IR spectral imaging.     

Comprehensive two-dimensional liquid chromatography-based quali-quantitative screening of aqueous phases from pyrolysis bio-oils

Pyrolysis processes are an alternative to minimize the environmental problem associated to agrifood industrial wastes. The main product resulting from these processes is a high-value liquid product, called bio-oil. Recently, the use of comprehensive two-dimensional liquid chromatography (LC × LC) has been demonstrated as a useful tool to improve the characterization of the water-soluble phases of bio-oils, considering their complexity and high water content. However, the precise composition of bio-oils from different agrifood byproducts is still unknown. In the present study, the qualitative and quantitative screening of eight aqueous phases from different biomasses, not yet reported in the literature, using LC × LC is presented. The two-dimensional approach was based on the use of two reverse phase separations. An amide column in the first dimension together with a C18 column in the second dimension were employed. Thanks to the use of diode array and mass spectrometry detection, 28 compounds were identified and quantified in the aqueous phase samples with good figures of merit. Samples showed a distinct quali-quantitative composition and a great predominance of compounds belonging to aldehydes, ketones and phenols, most of them with high polarity.     

Forced and unforced unsteadiness in an axial turbomachine

Different sources of unsteadiness in low-speed axial turbomachinery are identified and classified in this paper. From the classical picture segregating non-periodic mechanisms (turbulence) from periodic phenomena (unsteadiness), a further decomposition is outlined to distinguish between forced (deterministic periodicities) and unforced (non-deterministic) unsteadiness. Raw velocity traces, measured for several test conditions in a typical industrial fan with hot-wire anemometry, are ensemble-averaged to obtain time-resolved fluctuations. Then, a frequency-based filtering procedure is employed to isolate non-deterministic, but also non-chaotic, disturbances from the remaining turbulent fluctuations, resulting in the so-called unforced unsteadiness. This term reveals coherent flow structures that involve “large-scale” unsteadiness with other periodic features different to the blade rotation scales (BPF). As a starting point, the kinetic energy associated to the total unsteadiness (in terms of a percentage of the kinetic energy of the time-averaged flow) is analyzed as a function of the operating conditions. Next, the different components contributing to the total unsteadiness of the flow are also observed, in order to determine their particular significance on the global unsteady scenario. It is shown that the turbulent kinetic energy reaches up to approximately a 50–60% of the total unsteady energy, while both forced and unforced components contribute equally to the rest of the energy. In addition, it is observed that higher levels of unforced unsteadiness are concentrated towards the endwall boundary layers where forced unsteadiness is notably reduced due to the loss of the wake–core structure. Conversely, forced unsteadiness is more evident at inner regions of the rotor passage. Furthermore, unforced unsteadiness is especially intense in the tip regions where large-scales associated to the tip leakage vortex are established. It is demonstrated that the estimation of the unforced unsteadiness constitutes an accurate indicator of the presence of tip leakage flows for low-speed axial turbomachinery. Moreover, this is confirmed through the representation of the degree of anisotropy, where typical anisotropic structures are revealed. Finally, with the introduction of power spectrum densities for the unforced components, it is possible to identify typical eddy sizes of these large fluctuations.