Existence of Asymptotic Values for Nonexpansive Stochastic Control Systems

We consider an optimal stochastic control problem for which the payoff is the average of a given cost function. In a non ergodic setting, but under a suitable nonexpansivity condition, we obtain the existence of the limit value when the averaging parameter converges (namely the discount factor tends to zero for Abel mean or the horizon tends to infinity for the Cesàro mean). The main novelty of our result lies on the fact that this limit may depend on initial conditions of the control system (in contrast to what is usually obtained by other approaches). We also prove that the limit does not depend of the chosen average (Abel or Cesàro mean).     

Double isotope dilution surface-enhanced Raman scattering as a reference procedure for the quantification of biomarkers in human serum

Double isotope dilution surface-enhanced Raman scattering (double IDSERS) is qualified as a method for accurate and precise determination of biomarkers in human blood serum. Providing a full evaluation of the measurement uncertainty as well as traceability to a reference material sets the procedure in line with the requirements of a primary ratio method. Data evaluation is based on a partial least squares (PLS) model, whose prediction ability is validated from quantifying the uric acid concentration in both an artificial reference solution and a real human blood serum sample. With the proposed approach, the uric acid serum concentration can be determined with an uncertainty of 1.6% at a confidence level of 95%.     

Chemical alterations to murine brain tissue induced by formalin fixation: implications for biospectroscopic imaging and mapping studies of disease pathogenesis

Understanding biochemical mechanisms and changes associated with disease conditions and, therefore, development of improved clinical treatments, is relying increasingly on various biochemical mapping and imaging techniques on tissue sections. However, it is essential to be able to ascertain whether the sampling used provides the full biochemical information relevant to the disease and is free from artefacts. A multi-modal micro-spectroscopic approach, including FTIR imaging and PIXE elemental mapping, has been used to study the molecular and elemental profile within cryofixed and formalin-fixed murine brain tissue sections. The results provide strong evidence that amino acids, carbohydrates, lipids, phosphates, proteins and ions, such as Cl(-) and K(+), leach from tissue sections into the aqueous fixative medium during formalin fixation of the sections. Large changes in the concentrations and distributions of most of these components are also observed by washing in PBS even for short periods. The most likely source of the chemical species lost during fixation is the extra-cellular and intra-cellular fluid of tissues. The results highlight that, at best, analysis of formalin-fixed tissues gives only part of the complete biochemical "picture" of a tissue sample. Further, this investigation has highlighted that significant lipid peroxidation/oxidation may occur during formalin fixation and that the use of standard histological fixation reagents can result in significant and differential metal contamination of different regions of tissue sections. While a consistent and reproducible fixation method may be suitable for diagnostic purposes, the findings of this study strongly question the use of formalin fixation prior to spectroscopic studies of the molecular and elemental composition of biological samples, if the primary purpose is mechanistic studies of disease pathogenesis.     

Simultaneous Determination of 12 Sulfonylurea Herbicides in Drinking Water after SPE by LC-DAD

A liquid chromatographic method (LC) with diode array detection (DAD) for the routine screening and quantification of highly applicated polar herbicides in drinking water samples was developed. The investigated herbicides consisted of 12 sulfonylurea herbicides (amidosulfuron, flazasulfuron, foramsulfuron, iodosulfuron-methyl Na, mesosulfuron-methyl, metsulfuron-methyl, nicosulfuron, prosulfuron, thifensulfuron-methyl, triasulfuron and tritosulfuron) together with 6 polar pesticides of relevance (atrazine, desethylatrazine, desisopropylatrazine, chlortoluron, diuron, fluoxypyr). The herbicides were extracted and concentrated by off-line solid-phase extraction and subsequently eluates were analyzed by LC-DAD. Recoveries obtained from fortified water samples at 100 ng L^?1 were in the range of 84–107% with RSD’s <20%. The limit of detection varied from 2 to 16 ng L^?1.     

Numerically exact, time-dependent treatment of vibrationally coupled electron transport in single-molecule junctions

The multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) theory within second quantization representation of the Fock space, a novel numerically exact methodology to treat many-body quantum dynamics for systems containing identical particles, is applied to study the effect of vibrational motion on electron transport in a generic model for single-molecule junctions. The results demonstrate the importance of electronic-vibrational coupling for the transport characteristics. For situations where the energy of the bridge state is located close to the Fermi energy, the simulations show the time-dependent formation of a polaron state that results in a pronounced suppression of the current corresponding to the phenomenon of phonon blockade. We show that this phenomenon cannot be explained solely by the polaron shift of the energy but requires methods that incorporate the dynamical effect of the vibrations on the transport. The accurate results obtained with the ML-MCTDH in this parameter regime are compared to results of nonequilibrium Green's function theory.     

Electron-vibron coupling in halogenated acenaphthenequinone upon O K-edge soft x-ray absorption

We present high resolution oxygen K near-edge x-ray absorption spectra of the acenaphthenequinone (ANQ) derivative 3,8-dibromo-5,6-dichloro-ANQ (Br(2)Cl(2)-ANQ). The spectral features exhibit an almost identical vibronic fine structure compared to that shown by ANQ. The unequal distances of the vibronic levels as derived from the least-squares fit analysis of the vibronic progressions allows us to determine the anharmonicity of the excited state potentials involved. We conclude that a single vibrational progression couples to the resonant excitation of O 1s core electrons preferentially. Comparison of the two ANQ derivatives gives a clear indication that the vibronic mode corresponds to a C=O stretching mode, rather than coupling to a C-H mode as suggested previously. These conclusions are supported by density functional theory calculations.     

Microstructure and performance of AZO thin films prepared by sol–gel processing

Al-doped zinc oxide (AZO) films were prepared by a wet-chemical coating technique, their microstructure and crystal growth were characterized as a function of the single layer thickness. When similar final thicknesses are attained by more multiple subsequent coating-firing cycles, film porosity is reduced from over 14 to 2 %. Simultaneously the AZO crystallite size is increased from approximately 23 to 60 nm, a preferential c-axis oriented growth is observed. Different substrates (soda-lime glass, soda-lime glass with a SiO₂ barrier coating, borosilicate glass and alkali-free display glass) were used and the resulting AZO films were compared. It is found that the substrate composition primarily affects grain growth and subsequently the electrical performance of the AZO films.     

Flux through Trehalose Synthase Flows from Trehalose to the Alpha Anomer of Maltose in Mycobacteria

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Highlights? Flux through trehalose synthase (TreS) in mycobacteria is from trehalose to maltose ? The appropriate α anomer is formed by TreS for maltose kinase of the GlgE pathway ? The specificity of TreS for α-maltose is retained with deoxyfluoro analogs ? TreS supports cytosolic/capsular α-glucan but not trehalose mycolate biosynthesis     

Electron Transfer and Collision Induced Dissociation of Non-Derivatized and Derivatized Desmosine and Isodesmosine

Electron transfer dissociation (ETD) has attracted increasing interest due to its complementarity to collision-induced dissociation (CID). ETD allows the direct localization of labile post-translational modifications, which is of main interest in proteomics where differences and similarities between ETD and CID have been widely studied. However, due to the fact that ETD requires precursor ions to carry at least two charges, little is known about differences in ETD and CID of small molecules such as metabolites. In this work, ETD and CID of desmosine (DES) and isodesmosine (IDS), two isomers that due to the presence of a pyridinium group can carry two charges after protonation, are studied and compared. In addition, the influence of DES/IDS derivatization with propionic anhydride and polyethyleneglycol (PEG) reagents on ETD and CID was studied, since this is a common strategy to increase sensitivity and to facilitate the analysis by reversed-phase chromatography. Clear differences between ETD and CID of non-derivatized and derivatized-DES/IDS were observed. While CID is mainly attributable to charge-directed fragmentation, ETD is initiated by the generation of a hydrogen atom at the initial protonation site and its subsequent transfer to the pyridinium ring of DES/IDS. These differences are reflected in the generation of complex CID spectra dominated by the loss of small, noninformative molecules (NH₃, CO, H₂O), while ETD spectra are simpler and dominated by characteristic side-chain losses. This constitutes a potential advantage of ETD in comparison to CID when employed for the targeted analysis of DES/IDS in biological samples.