On Sectional Paths in a Category of Complexes of Fixed Size

We show how to build the Auslander-Reiten quiver of the category C _n (proj Λ) of complexes of size n ≥ 2, for any artin algebra Λ. We also give conditions over the complexes in C _n (proj Λ) under which the composition of irreducible morphisms in sectional paths vanishes.     

Characterization of Phenolics in Lavandula angustifolia

ABSTRACT

The lavender flowers and their essential oil are widely used in therapy in Romania and the European Community. Since the European Pharmacopoeia only allows the use of Lavandula sp flowers for medicinal purposes, the objective of this study was to investigate the chemical composition of Lavandula angustifolia extracts obtained by ultrasound-assisted extraction, rapid pressurized extraction at 6.7?bar, and subcritical fluid extraction. The solvents used for the first two methods were mixtures of water and alcohol, glycerin, and propylene glycol. These extracts were analyzed by high-performance thin-layer chromatography, infrared spectroscopy with attenuated total reflectance, and Raman spectroscopy. The total phenolics were evaluated using a modified Folin–Ciocalteu method. The primary phenolics were chlorogenic acid, gallic acid, umbelliferone, luteolin 7-O-glucoside, vitexin, and isoquercitroside. The extracts were variable in composition, with the highest yield by subcritical fluid extraction, followed by extraction at 6.7?bar. The infrared and Raman spectroscopy results confirmed the chromatography measurements.     

Conjugates between minor groove binders and Zn(II)-tach complexes: Synthesis,characterization, and interaction with plasmid DNA

A new family of conjugates between a Zn(II)-tach complex and (indole)₂ or benzofuran-indole amide minor groove binders connected through alkyl or oxyethyl linkers of different lengths has been prepared. The conjugates bind strongly to DNA. However, the complexation to DNA to promote the Zn(II) catalyzed hydrolytic cleavage of the DNA results instead in its inhibition. This inhibition effect has been confirmed also using Cu(II). Modeling studies suggest that in the most stable complex conformation, the minor groove binder and the linker lie in the minor groove hampering the interaction between the metal complex and the phosphate backbone of DNA. Therefore, the linear arrangement of minor groove binder-linker-metal complex appears to be effective to ensure tight binding but unproductive from a hydrolytic point of view.     

Comparison of HILIC columns for residue analysis of dithiocarbamate fungicides

Selective determination of dithiocarbamate (DTC) fungicides is mainly performed by hydrophilic interaction liquid chromatography (HILIC). According to Crnogorac and Schwack, DTC analyses by HILIC only lead to meaningful results with a zwitterionic polymer-based hydrophilic interaction liquid chromatography (ZIC-pHILIC) column. Considering the limited availability of this special type of column and the importance of DTC residue analysis, several new HILIC columns were evaluated as alternatives to the ZIC-pHILIC column. Detection was carried out by ultraviolet light and by mass spectrometry (MS) on a single quadrupole mass spectrometer coupled to an electrospray ionization interface operating in negative mode. On nearly all tested columns, separation of dimethyldithiocarbamates, ethylenebis(dithiocarbamates), and propylenebis(dithiocarbamates) was achieved with ammonium acetate eluents (pH 6.8). However, due to ion suppression by the buffer and the limited alkaline pH stability, the tested silica-based columns were not suitable for the sensitive analysis of DTCs. The polymer-based iHILIC-Fusion was the only alternative that offered high MS sensitivity, when a buffer containing 15?mM aqueous ammonium hydroxide and 7.5?mM ammonium hydrogen carbonate (pH 9.8) was used, but the separation of the three DTC subclasses was poor. Thus, considering both selectivity and sensitivity, the originally proposed polymer-based ZIC-pHILIC column still outperformed all the tested newly available alternative HILIC columns.     

Alleviation of the Fermion-sign problem by optimization of many-body wave functions

We present a simple, robust, and highly efficient method for optimizing all parameters of many-body wave functions in quantum Monte Carlo calculations, applicable to continuum systems and lattice models. Based on a strong zero-variance principle, diagonalization of the Hamiltonian matrix in the space spanned by the wave function and its derivatives determines the optimal parameters. It systematically reduces the fixed-node error, as demonstrated by the calculation of the binding energy of the small but challenging C(2) molecule to the experimental accuracy of 0.02 eV.     

Supramolecular organization of toluidine blue dye in solid amorphous phases

Toluidine blue (TB) dye molecules are intensively utilized for large-area photophysics applications such as carcinoma detection, photoinactivation of bacteria, biosensors, and photovoltaic cells. Understanding the nature of the TB aggregation state becomes an essential point of the research process in order to know the structure-function relationship and to foresee technological applications of this class of metachromatic-dye molecules. However, no structural information on toluidine blue is available in the literature, maybe because of the poor crystalline character of the aggregate. Here, we present the first structural determination of TB organic molecules using the energy dispersive X-ray diffraction technique. The investigation highlights dimeric arrangements of stacked molecules in antiparallel fashion, forming a superstructure of two dimers in a transverse arrangement. The behavior of the TB higher aggregates indicates that these dye molecules, in spite of repulsion due to similar charge (cationic dyes), undergo self-aggregation to form helical conformations.     

Site-selective depurination by a periodate-dependent deoxyribozyme

A deoxyribozyme is identified that mediates the site-selective depurination of its 5'-terminal guanosine nucleotide using periodate (IO(4)-) as an obligatory cofactor.     

How can immunochemical methods contribute to the implementation of the Water Framework Directive?

Immunochemical methods (in particular immunoassays) have been applied to spring and surface water samples, respectively, which were set-up as reference materials (RM) within two proficiency testing campaigns. For the first set of proficiency tests (PTs) described here (which were actually the second round of PTs organized, spring 2005), three ELISAs (enzyme-linked immunosorbent assays) were employed in the enzyme tracer format for isoproturon, diuron, and atrazine, respectively. Results were evaluated in comparison with conventional reference methods (LC, GC). Based on their Z-score laboratory performances, the results for isoproturon and diuron were satisfactory, both for fortified spring water and for the blind solution. The results for atrazine were strongly influenced by other triazines present and needed detailed interpretation. For the second set of PTs described here (which were actually the third round of PTs organized, spring 2006), two ELISAs in the coating antigen format were used for isoproturon and diuron, and the result was included with the results obtained by conventional methods during the PTs. The results (the Z-scores) for isoproturon were again classified as satisfactory, in both fortified surface water and blind solution. The results for diuron in ELISA showed an influence of the water matrix, while the analysis of the blind solution was satisfactory. In addition, an ELISA in the enzyme tracer format was applied to analyze isoproturon, diuron, and atrazine in surface water samples, which had been set-up and spiked during a field trial (tank experiment) at the Maas River at Eijsden, The Netherlands. The immunoassay results were compared with those from an in-house on-line SPE LC/MS–MS used as reference. Although the immunochemical results were sometimes higher than those determined in the reference analysis, the general concentration trends in the samples were similar. The contribution of immunochemical methods to the implementation of the European Water Framework Directive is also discussed.     

Perceptual thresholds for detecting modifications applied to the acoustical properties of a violin

This study is the first step in the psychoacoustic exploration of perceptual differences between the sounds of different violins. A method was used which enabled the same performance to be replayed on different "virtual violins," so that the relationships between acoustical characteristics of violins and perceived qualities could be explored. Recordings of real performances were made using a bridge-mounted force transducer, giving an accurate representation of the signal from the violin string. These were then played through filters corresponding to the admittance curves of different violins. Initially, limits of listener performance in detecting changes in acoustical characteristics were characterized. These consisted of shifts in frequency or increases in amplitude of single modes or frequency bands that have been proposed previously to be significant in the perception of violin sound quality. Thresholds were significantly lower for musically trained than for nontrained subjects but were not significantly affected by the violin used as a baseline. Thresholds for the musicians typically ranged from 3 to 6 dB for amplitude changes and 1.5%-20% for frequency changes. Interpretation of the results using excitation patterns showed that thresholds for the best subjects were quite well predicted by a multichannel model based on optimal processing.