Identification of hydrolysis products of AlCl(3)*6H(2)O in the presence of sulfate by electrospray ionization time-of-flight mass spectrometry and computational methods

ElectroSpray Ionization-Mass Spectrometry (ESI-MS) and computational methods (DFT, MP2, and COSMO) were used to investigate the hydrolysis products of aluminium chloride as a function of sulfate concentration at pH 3.7. With the aid of computational chemistry, structural information was deduced from the chemical compositions observed with ESI-MS. Many novel types of hydrolysis products were noted, revealing that our present understanding of aluminium speciation is too simple. The role of counterions was found to be critical: the speciation of aluminium changed markedly as a function of sulfate concentration. Ab initio calculations were used to reveal the energetically most favoured structures of aluminium sulfate anions and cations selected from the ESI-MS results. Several interesting observations were made. Most importantly, the bonding behaviour of the sulfate group changed as the number of aqua ligands increased. The accompanying structural rearrangement of the clusters revealed the highly active role of sulfate as a ligand. The gas phase calculations were expanded to the aquatic environment using a conductor-like screening model. As expected, the bonding behaviour of the sulfate group in the minimum energy structures was distinctly different in the aquatic environment compared to the gas phase. Together, these methods open a new window for research in the solution chemistry of aluminium species.     

Preprocessing Strategies for Sparse Infrared Spectroscopy: A Case Study on Cartilage Diagnostics

The aim of the study was to optimize preprocessing of sparse infrared spectral data. The sparse data were obtained by reducing broadband Fourier transform infrared attenuated total reflectance spectra of bovine and human cartilage, as well as of simulated spectral data, comprising several thousand spectral variables into datasets comprising only seven spectral variables. Different preprocessing approaches were compared, including simple baseline correction and normalization procedures, and model-based preprocessing, such as multiplicative signal correction (MSC). The optimal preprocessing was selected based on the quality of classification models established by partial least squares discriminant analysis for discriminating healthy and damaged cartilage samples. The best results for the sparse data were obtained by preprocessing using a baseline offset correction at 1800 cm⁻¹, followed by peak normalization at 850 cm⁻¹ and preprocessing by MSC.     

Withaferin A—A Promising Phytochemical Compound with Multiple Results in Dermatological Diseases

Withaferin A (WFA) was identified as the most active phytocompound of the plant Withania somnifera (WS) and as having multiple therapeutic/ameliorating properties (anticancer, antiangiogenic, anti-invasive, anti-inflammatory, proapoptotic, etc.) in case of various diseases. In drug chemistry, WFA in silico approaches have identified favorite biological targets, stimulating and accelerating research to evaluate its pharmacological activity—numerous anticancer effects manifested in various organs (breast, pancreas, skin, colon, etc.), antivirals, anti-infective, etc., which are not yet sufficiently explored. This paper is a synthesis of the most relevant specialized papers in the field that are focused on the use of WFA in dermatological diseases, describing its mechanism of action while providing, at the same time, details about the results of its testing in in vitro/in vivo studies.     

Undecidability in matrices over Laurent polynomials

We show that it is undecidable for finite sets S of upper triangular (4×4)-matrices over Z[x,x⁻¹] whether or not all elements in the semigroup generated by S have a nonzero constant term in some of the Laurent polynomials of the first row. This result follows from a representations of the integer weighted finite automata by matrices over Laurent polynomials.     

Evaluation of Meldola Blue‐Carbon Nanotube‐Sol‐Gel Composite for Electrochemical NADH Sensors and Their Application for Lactate Dehydrogenase‐Based Biosensors

A novel MB‐SWNT‐sol‐gel nanocomposite material was prepared by the sol‐gel process incorporating a redox mediator and carbon nanotubes. The electrocatalytic properties of the nanomaterial based sensor toward NADH oxidation were studied by electrochemical measurements. Significant enhancement of oxidation current is obtained at electrodes modified by MB‐SWNT‐sol‐gel in comparison with the analogous carbon black and/or graphite composite modified electrode. The usefulness of the nanocomposite material as a matrix for immobilizing enzymes is also demonstrated. Analytical parameters of D ‐lactate biosensors with and without SWNT in the hybrid film were compared demonstrating that performance of the biosensor was significantly improved when introducing SWNT.     

Analysis of chemical warfare agents in water by solid phase extraction and two-channel capillary gas chromatography

Solid phase extraction with commercial C-18 cartridges has been applied to the analysis of some well known chemical warfare agents in water samples. Different sample pretreatment and cartridge conditioning procedures, and different extraction solvents were tested to study the optimum conditions for efficient extraction and recovery of the compounds of interest. The eluates were analyzed with a two-channel gas chromatograph equipped with an autosampler and a retention index monitoring system. The suitability of this technique for real samples is discussed: the rapid hydrolysis of many of the compounds studied and the poor recoveries of the polar degradation products are practical limitations of the method.     

Electron impact induced fragmentation of dihydro-1,4-dithiines. 2,3-Substituted 5,6-dihydro-l,4-dithiines

In the electron impact induced fragmentation of 2,3-disubstituted 5,6-dihydro-1,4-dithiines, the most important cleavage of the heterocyclic ring occurs via the retro-Diels-Alder type of reaction. The further fragmentation of the resulting radical cation gives rise to substitutes thiocarbonyl cations. This fragmentation favours formations of ions in which the electron-deficient carbon-sulphur triple bond is stabilized by an electron-releasing group. The ring fragmentation was observed to be dependent on the nature of the 3- and 2-substituents of the ring when a series of 3- and 2-substituted 5,6-dihydro-l,4-dithiines was investigated. The fragmentation of dihydro-l,4-dithiines partly resembles the fragmentation of the corresponding dihydro-l,4-oxathiines. The presence of the two sulphur atoms in dihydro-l,4-dithiines give rise to more stable molecular ions than observed in the case of the dihydro-1,4-oxathiine analogues. Fragmentations of dihydro-l,4-dithiines can also involve extrusions of alkylradicals or HS-radical from the heterocyclic rings of molecular ions.     

Acoustical analysis and model-based sound synthesis of the kantele

The five-string Finnish kantele is a traditional folk music instrument that has unique structural features, resulting in a sound of bright and reverberant timbre. This article presents an analysis of the sound generation principles in the kantele, based on measurements and analytical formulation. The most characteristic features of the unique timbre are caused by the bridgeless string termination around a tuning pin at one end and the knotted termination around a supporting bar at the other end. These result in prominent second-order nonlinearity and strong beating of harmonics, respectively. A computational model of the instrument is also formulated and the algorithm is made efficient for real-time synthesis to simulate these features of the instrument timbre.     

Midazolam sedation increases fluctuation and synchrony of the resting brain BOLD signal

The blood oxygen level-dependent (BOLD) magnetic resonance signal of functional brain cortices is dominated by very low frequency (VLF) fluctuations in anesthetized child patients. The temporal synchrony of the BOLD signal is also higher in anesthetized children compared with awake adults. The origin of the synchronous fluctuations can be related to maturation, pathological status or the anesthesia used in the imaging. Two of the three confounding variables (maturation and pathology) were controlled in this study. The effect of midazolam (4+/-0.8 mg) sedation on the BOLD signal was assessed in 12 healthy adults (aged 24+/-1.5 years) at 1.5 T. The VLF fluctuation power and temporal synchrony of the BOLD signal increased significantly after the sedation in the auditory and visual cortices. The fast Fourier transformation power spectral baseline fit parameters of the BOLD signal were also found to change significantly after sedation. It is concluded that the VLF fluctuation and temporal synchrony of the BOLD signal become increased after sedation in functional brain regions.