Molecular momentum distributions and compton profiles. Effects of bonding on some small molecules

Electronic momentum distributions and Compton profiles have been calculated from minimum basis set SCF wavefunctions for H₂O, H₂O₂, CO, CO₂ and H₂CO. Radial distributions and profiles have also been estimated for these molecules from localized molecular orbitals. The results suggest that (a) the height of the Compton peak, <p^?1>, may be as sensitive to the effects of chemical bonding as the kinetic energy, <p²>/2, and that (b) the virial theorem may provide a more useful criterion than energy minimization in assessing the accuracy of calculated bonding effects and Compton profiles.     

Modelling of Glow Discharge Optical Emission Spectroscopy depth profiles of metal (Cr,Ti) multilayer coatings

The broadening effects found in the depth profiles of abrupt periodic multilayers obtained by Glow Discharge Optical Emission Spectroscopy (GDOES) have been modelled by assuming that the resulting absolute concentration profiles can be described by Gaussian functions of constant area (equal to that of the cross section of the individual layers) and decreasing amplitude. The full width at half maximum (FWHM) of these functions has been assumed to increase with depth z according to a power law of the type: FWHM (z) = a + bz^c, using for a and c, values estimated from previous works. In this model, the parameter b, defining the broadening and degradation of the layer interfaces, is obtained by fitting the experimental profiles with the theoretical spectra. We have found a correlation between b and the erosion rate of the material layers. In general, the model properly describes the depth profiles of multilayer structures made of alternating Ti and Cr layers in the nanometre range, and can be an useful tool to explain the profiles of more complex systems.     

Differential Flavonoid and Other Phenolic Accumulations and Antioxidant Activities of Nymphaea lotus L. Populations throughout Thailand

Nymphaea lotus L. is a potential plant in the Nymphaeaceae family that is well-recognized as an economic and traditional medicinal plant in Thailand and other countries. Its pharmacological and medicinal effects have been confirmed. However, there is no study going deeper into the population level to examine the phytochemical variation and biological activity of each population that benefits phytopharmaceutical and medical applications using this plant as raw material. This study was intensely conducted to complete this important research gap to investigate the flavonoid profiles from its floral parts, the stamen and perianth, as well as the antioxidant potential of the 13 populations collected from every floristic region by (1) analyzing their flavonoid profiles, including the HPLC analysis, and (2) investigating the antioxidant capacity of these populations using three assays to observe different antioxidant mechanisms. The results indicated that the northeastern and northern regions are the most abundant floristic regions, and flavonoids are the main phytochemical class of both stamen and perianth extracts from N. lotus. The stamen offers higher flavonoids and richer antioxidant potential compared with the perianth. This finding is also the first completed report at the population level to describe the significant correlation between the phytochemical profiles in floral parts extracts and the main antioxidant activity, which is mediated by the electron transfer mechanism. The results from the Pearson correlation coefficients between several phytochemicals and different antioxidant assessments highlighted that the antioxidant capability of these extracts is the result of complex phytochemical combinations. The frontier knowledge from these current findings helps to open up doors for phytopharmaceutical industries to discover their preferred populations and floral parts that fit with their targeted products.     

The Impact of Nitrile-Specifier Proteins on Indolic Carbinol and Nitrile Formation in Homogenates of Arabidopsis thaliana

Glucosinolates, specialized metabolites of the Brassicales including Brassica crops and Arabidopsis thaliana, have attracted considerable interest as chemical defenses and health-promoting compounds. Their biological activities are mostly due to breakdown products formed upon mixing with co-occurring myrosinases and specifier proteins, which can result in multiple products with differing properties, even from a single glucosinolate. Whereas product profiles of aliphatic glucosinolates have frequently been reported, indole glucosinolate breakdown may result in complex mixtures, the analysis of which challenging. The aim of this study was to assess the breakdown of indole glucosinolates in A. thaliana root and rosette homogenates and to test the impact of nitrile-specifier proteins (NSPs) on product profiles. To develop a GC-MS-method for quantification of carbinols and nitriles derived from three prominent indole glucosinolates, we synthesized standards, established derivatization conditions, determined relative response factors and evaluated applicability of the method to plant homogenates. We show that carbinols are more dominant among the detected products in rosette than in root homogenates of wild-type and NSP1- or NSP3-deficient mutants. NSP1 is solely responsible for nitrile formation in rosette homogenates and is the major NSP for indolic nitrile formation in root homogenates, with no contribution from NSP3. These results will contribute to the understanding of the roles of NSPs in plants.     

Study of reaction processes by in-line near-infrared spectroscopy in combination with multivariate curve resolution: Esterification of myristic acid with isopropanol

The acid-catalysed esterification of myristic acid with isopropanol was studied by using near-infrared spectroscopy (NIR) in combination with soft-modeling curve resolution (MCR) methodology with a view to establishing the effect of experimental variables on the reaction kinetics. The reaction was conducted at temperatures above the boiling point of the alcohol, with continuous addition of an isopropanol/water mixture to the reactor. Spectral and concentration profiles were determined by applying soft-modeling curve resolution methodology to a column-wise augmented data matrix containing the spectra for the pure components. MCR profiles were compared with reference values and found to depart from then by less than 3% as %RSE for concentrations and to exhibit correlation above 0.999 for spectra.The reaction kinetics as estimated from the concentration profiles was found to be pseudo-first-order. Also, the pseudo-first-order rate constant was found to depend on the flow-rate of the isopropanol/water mixture and its water content; although the constant decreased with increase in the proportion of water, a content of ca. 15% could be used without important retarding effects on the kinetics. The proposed NIR-MCR method allows the rate constant and the influence of the initial water content to be determined with a view to minimizing consumption of the raw materials and optimizing the experimental conditions.     

The effect of afforestation on the soil organic carbon (SOC) of a peaty gley soil using on-line thermally assisted hydrolysis and methylation (THM) in the presence of 13C-labelled tetramethylammonium hydroxide (TMAH)

In Britain substantial areas of both deep and shallow peatland have been afforested with conifers since the 1950s. However, information about the effects of afforestation on the properties of soil organic carbon (SOC) is lacking. Investigating the geochemical changes that take place when lignin- and tannin-derived phenols are degraded and incorporated into SOC will provide us with an insight into soil carbon dynamics at the molecular level. Here we compare the phenolic distributions in two different peaty gley soil profiles using on-line thermally assisted hydrolysis and methylation (THM) in the presence of both unlabelled and ¹³C-labelled tetramethylammonium hydroxide (TMAH). The two soil profiles were beneath respectively an unforested moorland (ML) and a second rotation Sitka spruce (Picea sitchensis) afforested moorland (SS), from Harwood (Northumberland, northeast England, UK). THM of these soils in the presence of ¹³C-labelled TMAH enabled us to assess the relative contributions of lignin, demethylated lignin, and non-lignin phenolics. The lignin phenolic distributions differed in both soil profiles reflecting changing source and decay dynamics within and between the sites. A progressive degradation of syringyl (S) and guaiacyl (G) phenolics was observed in the ML soil, compared with an increase of such components in the organic/mineral horizons of the SS soil. A significant tannin input was observed, particularly in the upper horizons of the SS soil. The S/G ratio gradually decreased with increasing burial in the ML soil, whilst a change in vegetation input and land preparation was recorded by this ratio in the SS soil. Overall, this suggests that afforestation influences the phenolic compositional profiles in these peaty gley soils as a result of one or more of the following processes: changing vegetation input, horizon inversion prior to planting, root input or leaching. This highlights the potential of using lignin and tannins as molecular indicators to assess the effects of afforestation on SOC.     

Experimental and theoretical compton profiles of CIS and trans-2-butene

The Compton profiles of the geometric isomers cis and trans-2-butne (C₄H₈) have been measured in the gas phase using 59.54 keV gamma rays. The measured profiles are compared with profiles derived from SCF and LMO models. No significant differences between the measured profiles are observed. However, comparison with the theoretical profiles shows that in both cases the measured profiles are broader, having J(0) values between 1 and 5% lower than those predicted by theory.     

Studies of molecular motions and vibrational relaxation VII. Rotational diffusion model to investigate the band shapes of the ν5 and ν8 ban

Reorientational correlation functions G_rot^(l)(t)) for the degenerate (E) bands of liquid acetonitrile (CH₃CN) have been computed us NMR spin-lattice relaxation data (for CD₃CN) and gas phase Raman band profiles, assuming that the rotational diffusion model is valid. The effects both anisotropic rotational motion and of Coriolis coupling are included. The predicted correlation functions along with those calculated using ther cl “free” rotor equations, have been compared with those obtained from the υ_s (Raman) and υ_s (IR and Raman) experimental band profiles. It shown that, despite the simplicity of the model and obvious (understandable) discrepancies at short times, sensible conclusions may be drawn. This work a starting point for the testing of more complicated models for reorientational motion in dense phases.     

Laser excited atomic fluorescence for studies of enhancement effects in the direct current plasma

This paper reports a preliminary use of laser excited atomic fluorescence spectrometry (LEAFS) to study analyte population enhancement caused by easily ionized elements (EIEs) in the direct current plasma (DCP). Spatial atom density profiles in the DCP were obtained using resonance fluorescence at the calcium atom line at 422.7 nm, with and without the addition of an EIE. Variations in atom density caused by an EIE were found to be far too small to account for the marked enhancements of atomic emission signals which are caused by EIEs.Direct line fluorescence of the barium ion, excited at 614 nm and detected at 455 nm, was used to probe the effect of an EIE on excited state populations. Measurements in the analytical region of the plasma close to the core revealed that enhancements of fluorescence signals at low laser powers disappeared at laser powers which were sufficient to saturate the atomic transitions. While this result does not clarify any of the mechanisms of excitation in the DCP, it does lend support to two of the fundamental postulates of a recent model of the spectrochemical excitation processes in the DCP. These are first, that the analytical region of the DCP is not in local thermodynamic equilibrium (LTE) and second, that EIE enhancement proceeds by modulating the rates of power distribution among various plasma zones.In the outer zone of the analytical region of the DCP, depressive interferences occurred. These did not disappear upon saturation which indicates that they were not rate effects but effects that resulted from atom density changes.     

Electron correlation and the compton profile of atomic neon

The radial momentum distribution I_o(p) and the Compton profile J_o(q) are determined for atomic neon from several restrictid Hartree-Fock (RHF) wavefunctions and two configuration interaction (CI) wavefunctions. The CI functions are the well correlated (full“second-order”) function of Viers, Schaeffer and Harris, and the Ahlrichs-Hinze multi-configuration Hartree-Fock (MCHF) function which includes only L-shell correlation. It is found for this completely closed shell system that the effects of electron correlation are quite small. This contrasts with the results for systems such as Be(²S) and B(²P) where the semi-internal and internal correlation effects were responsible for significant discrepancies between the RHF and CI results. These results indicate that a wavefunction which carefully includes the semi-internal, orbital polarization, and internal correlations beyond the RHF wavefunction (i.e., a “first-order” or “charge-density” function), should account for the principal correlation effects on the Compton profiles and momentum distributions.     

Photodegradation and weathering effects on timber surface moisture profiles as studied using dynamic vapour sorption

The moisture sorption kinetic profiles of Scots pine (Pinus sylvestris) earlywood and latewood were studied using a Dynamic Vapour Sorption apparatus and the equilibrium isotherms determined. The samples were chosen to give an insight to the effects that photodegradation and weathering have on the moisture behaviour of the surface layers of timber. Samples were subjected to indoor and outdoor exposure regimes. Significant differences were found between the sorption isotherms of exposed and unexposed wood, as well as with the sorption kinetics profiles. The reasons for these differences are discussed.     

Test ofBΣ-interaction potentials in Na 3P-rare gas systems from light scattering

The spectral dependences in Na-rare gas optical collisions $$Na3S + X + hv \to Na3P_J + X$$ have been used to study the long range interaction in Na 3P _J -X systems. For a test of available potentials the fine structure (fs) population ratio and theJ = 3/2 alignment were measured under single collision conditions by analyzing the fluorescence emitted after selective excitation of the molecularBΣ orAΠ states as function of the laser frequencyv. A comparison was made with quantum coupled channels (CC) calculations of thermally averaged spectral profiles using the potential data to be tested as input. In addition, model calculations were performed for a qualitative understanding of the role of the various nonadiabatic couplings involved and the trends in the spectral profiles by the corresponding molecular potentials. In NaAr and NaKr theBΣ-fs wings are seen to depend sensitively on the parameters of the potentials, in particular on the well depth? _ΣII of theBΣ-AΠ difference potentials which is comparable to the spin orbit interaction in these systems; the experimental profiles show, that the actual? _ΣII values are much smaller than those predicted by the model potentials of Düren. In NaKr also theBΣ-alignment wing depends sensitively on? _ΣII caused by a long-range parity dependent rotational coupling, as follows from the CC-analysis. The comparison with the experimental alignment confirms the result from theBΣ-fs wing regarding the actual? _ΣII value.     

Additivity of statistical moments in the exponentially modified Gaussian model of chromatography

A homologous series of saturated fatty acids ranging from C₁₀ to C₂₂ was separated by reversed-phase capillary liquid chromatography. The resultant zone profiles were found to be fit best by an exponentially modified Gaussian (EMG) function. To compare the EMG function and statistical moments for the analysis of the experimental zone profiles, a series of simulated profiles was generated by using fixed values for retention time and different values for the symmetrical (σ) and asymmetrical (τ) contributions to the variance. The simulated profiles were modified with respect to the integration limits, the number of points, and the signal-to-noise ratio. After modification, each profile was analyzed by using statistical moments and an iteratively fit EMG equation. These data indicate that the statistical moment method is much more susceptible to error when the degree of asymmetry is large, when the integration limits are inappropriately chosen, when the number of points is small, and when the signal-to-noise ratio is small. The experimental zone profiles were then analyzed by using the statistical moment and EMG methods. Although care was taken to minimize the sources of error discussed above, significant differences were found between the two methods. The differences in the second moment suggest that the symmetrical and asymmetrical contributions to broadening in the experimental zone profiles are not independent. As a consequence, the second moment is not equal to the sum of σ² and τ², as is commonly assumed. This observation has important implications for the elucidation of thermodynamic and kinetic information from chromatographic zone profiles.     

Quasi-stationary detection of transient absorption of a dissociating molecule

Using the forth harmonic of a Nd-YAG laser at 266 nm TlI was dissociated and the dissociation was observed by a transient absorption due to a transition from the repulsive potential, which correlates to T1 (6p ² P _3/2) and I, to the repulsive potential with the asymptote T1 (7s) and I. The experiment is performed with quasi-stationary spectroscopy in the nanosecond time domain, but detects transients effects by asymmetric absorption profiles in the frequency domain. Simulations applying Bloch equations with time dependent molecular energies are able to reproduce the observations and give information on the difference potential between the two molecular states involved and the transition dipole moment. The results are also in good agreement with fs experiments from other authors.     

Extraction of climatic signals from fossil organic compounds in marine sediments up to 11.7 Ma old (IODP-U1318)

This study focuses on the extraction of climate signals and processes using a combined approach which includes the analysis of a high number of lipid molecules in marine sediments, and the chemometric analysis of the acquired data. Neutral and acidic fractions of marine sediments from site IODP-U1318 (south-west of the UK, Porcupine Seabight) were quantified by GC–MS. The alkenone unsaturation index, U^k′₃₇, was estimated from the composition of C₃₇ alkenones and it was then used for the estimation of sea surface temperatures (SST) for reference. Principal component analysis (PCA), explained 77.45% of the total data variance, and differentiated neutral fraction GC–MS total ion current (TIC) profiles according to SST values of the different sediment sections. GC–MS TIC chromatograms were correlated to sea surface temperatures (SST) by partial least squares regression (PLSR). The compounds more robustly in line with SST values at each sediment section explained 93% of the SST variance and they were identified using the variable importance in projection (VIP) scores method. The proposed approach enables an objective identification of organic compounds sensitive to SST variability throughout complete chromatographic profiles. As a result of this multivariate unbiased approach, lipid composition of sediments was differentiated between compounds of marine (long chain n-alkanes, long chain n-alkan-1-ols) and terrestrial (short chain n-alkan1-ols, alkenols, cholesterol, squalene) origin, whose concentrations were directly and inversely correlated to SST, respectively.     

Synthesis and Evaluation of Chalcone-Quinoline Based Molecular Hybrids as Potential Anti-Malarial Agents

Molecular hybridization is a drug discovery strategy that involves the rational design of new chemical entities by the fusion (usually via a covalent linker) of two or more drugs, both active compounds and/or pharmacophoric units recognized and derived from known bioactive molecules. The expected outcome of this chemical modification is to produce a new hybrid compound with improved affinity and efficacy compared to the parent drugs. Additionally, this strategy can result in compounds presenting modified selectivity profiles, different and/or dual modes of action, reduced undesired side effects and ultimately lead to new therapies. In this study, molecular hybridization was used to generate new molecular hybrids which were tested against the chloroquine sensitive (NF54) strain of P. falciparum. To prepare the new molecular hybrids, the quinoline nucleus, one of the privileged scaffolds, was coupled with various chalcone derivatives via an appropriate linker to produce a total of twenty-two molecular hybrids in 11%–96% yield. The synthesized compounds displayed good antiplasmodial activity with IC₅₀ values ranging at 0.10–4.45 μM.     

Self-Tuning GMV Control of Glucose Concentration in Fed-Batch Baker’s Yeast Production

A detailed system identification procedure and self-tuning generalized minimum variance (STGMV) control of glucose concentration during the aerobic fed-batch yeast growth were realized. In order to determine the best values of the forgetting factor (λ), initial value of the covariance matrix (α), and order of the Auto-Regressive Moving Average with eXogenous (ARMAX) model (n _a, n _b), transient response data obtained from the real process wereutilized. Glucose flow rate was adjusted according to the STGMV control algorithm coded in Visual Basic in an online computer connected to the system. Conventional PID algorithm was also implemented for the control of the glucose concentration in aerobic fed-batch yeast cultivation. Controller performances were examined by evaluating the integrals of squared errors (ISEs) at constant and random set point profiles. Also, batch cultivation was performed, and microorganism concentration at the end of the batch run was compared with the fed-batch cultivation case. From the system identification step, the best parameter estimation was accomplished with the values λ?=?0.9, α?=?1,000 and n _a?=?3, n _b?=?2. Theoretical control studies show that the STGMV control system was successful at both constant and random glucose concentration set profiles. In addition, random effects given to the set point, STGMV control algorithm were performed successfully in experimental study.     

Kinetic modeling of two-step RAFT process for the production of novel fluorosilicone triblock copolymers

Well-defined poly(dimethylsiloxane)-b-poly(2,2,3,3,4,4,4-heptafluorobutylmethacryl-ate-b-poly(styrene) (PDMS-b-PHFBMA-b-PS) triblock copolymers were prepared by two-step reversible addition-fragmentation chain transfer (RAFT) polymerization. A comprehensive mathematical model for the two-step RAFT polymerization in a batch reactor was presented using the method of moments. The model described molecular weight, monomer conversion and polydispersity index as a function of polymerization time. Good agreements in the polymerization kinetics were achieved for fitting the kinetic profiles with the suggested model. In addition, the model was used to predict the effects of initiator concentration, chain transfer agent concentration and monomer concentration on the two-step RAFT polymerization kinetics. The simulated results showed that for the two-step RAFT polymerizations, the effects initiator concentration, chain transfer agent concentration and monomer concentration are identical and the influence degrees are different yet.     

Investigation of the effects of 24 bio-matrices on the LC-MS/MS analysis of morinidazole

This study compares and evaluates the effect of various matrices on liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) analysis. Permanent post-column infusion (PCI) was used to quantify matrix effects. In this way, the suppressed or enhanced signal of the target material resulting from different co-eluting matrix components could be assessed. Twenty-four biological samples from in vivo and in vitro experiments were selected for this study. In addition, 7 sample components were further analyzed after sample preparation by protein precipitation. Multiple regression analysis was used to investigate the collinear relationship between matrix effects and co-eluted components at different time intervals. We found that salt was the dominant factor which impacted changes in signal detection. In order to eliminate it, we used ammonium formate as a modifier of the mobile phase which resulted in charge-state redistribution profiles so that a homogeneous matrix formed. By employing pulse gradient chromatography in the presence of 5 mM ammonium formate, favorable improvements of enhanced signal intensity and reduced matrix effects were obtained. These experiments also indicated the feasibility of using analogue IS during bio-analysis which contributed to an overall faster assay that would be suitable for drug discovery and development purposes.