Quantum sum formulae for the collision-induced spectroscopies: Molecular systems as H2-H2

Quantum expressions for the second moment of collision-induced spectra are developed in the low-density limit. Previous work by Moraldi is extended to account for the rotational structure of colliding linear molecules; isotropic interaction is assumed. Computations of the lowest three moments are presented for the case of infrared absorption and Raman scattering of molecular hydrogen pairs at temperatures from 77 to 300 K. The radial distribution functions of pairs, mean energy and angular momentum, which are required for that purpose, are obtained for the case of H₂ molecules interacting with H₂, and compared with their classical counterparts. The simple classical approximations with lowest-order Wigner-Kirkwood quantum corrections serve as an accurate representation of the quantum expressions at large separations and may be sufficient for massive systems at high temperatures.     

Mikrobestimmung von Spuren von Saponinglykosiden in ”nicht-saponinführendem“ Pflanzenmaterial

Zusammenfassung Eine Methode zur densitometrischen Mikrobestimmung von Standardsaponinen (Digitonin und Aescin) nach dem HämolySciest auf Dünnschichtplatten wurde beschrieben. Diese Methode wurde zum Nachweis und zur Bestimmung unbekannter Saponine in Pflanzenextrakten herangezogen. Eichkurven für den HämolySciest und auch für die HClO_4– und Anisaldehydteste wurden angegeben. Im Bereich von 6 bis 25g Saponin im Chromatogrammfleck wurde ein Umrechnungsfaktor für 10g Saponin benutzt. Wegen der Spezifität und der hohen Empfindlichkeit des HämolySciestes nach der chromatographischen Trennung von Begleitstoffen eignet sich das densitometrische Verfahren vorzüglich zur eindeutigen Feststellung und serienmäßigen Bestimmung von Saponinen in Extrakten von Pflanzenmaterial, das in der Fachliteratur als nichtsaponinfuhrend gilt.

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Microdetermination of traces of saponin glycosides in plant material not containing saponin

Summary A method of densitometric microdetermination of standard saponins (digitonin and aescin) according to the hemolysis test on thin-layer plates was described. This method was used to demonstrate and determine unknown saponins in plant extracts. Calibration curves were given for the hemolysis test and also for the HClO_4– and anisaldehyde tests. In the region from 6 to 25g saponin in the chromatogram spot, a conversion factor for 10g saponin was used. Because of the specificity and the high sensitivity of the hemolysis test, after the chromatographic separation of concomitant substances the densitometric method is eminently suitable for unequivocal detection and determination of saponins in series of extracts of plant material which as previously been regarded in the specialist literature as not containing saponin.

     

Nature of versatile chemisorption on TiC(111) and TiN(111) surfaces

Density-functional calculations on the polar TiX(111) (X = C, N) surfaces show (i) for clean surfaces, strong Ti3d-derived surface resonances (SR’s) at the Fermi level and X2p-derived SR’s deep in the upper valence band and (ii) for adatoms in periods 1-3, pyramidic trends in atomic adsorption energies, peaking at oxygen (9 eV). A concerted-coupling model, where adatom states couple to both kinds of SR’s in a concerted way, describes the adsorption. The chemisorption versatility and the general nature of the model indicate ramifications and predictive abilities in, e.g., growth and catalysis.     

About Some Boundary Value Problems for Fractional PDE and their Numerical Solution

A transmission initial-boundary-value problem in disjoint intervals for fractional in time diffusion equation is studied. Its well posedness in the corresponding Sobolev-like spaces is proved. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Attachment of Single-Stranded DNA to Certain SERS-Active Gold and Silver Substrates: Selected Practical Tips

Layers formed from single-stranded DNA on nanostructured plasmonic metals can be applied as “working elements” in surface–enhanced Raman scattering (SERS) sensors used to sensitively and accurately identify specific DNA fragments in various biological samples (for example, in samples of blood). Therefore, the proper formation of the desired DNA layers on SERS substrates is of great practical importance, and many research groups are working to improve the process in forming such structures. In this work, we propose two modifications of a standard method used for depositing DNA with an attached linking thiol moiety on certain SERS-active structures; the modifications yield DNA layers that generate a stronger SERS signal. We propose: (i) freezing the sample when forming DNA layers on the nanoparticles, and (ii) when forming DNA layers on SERS-active macroscopic silver substrates, using ω-substituted alkanethiols with very short alkane chains (such as cysteamine or mercaptopropionic acid) to backfill the empty spaces on the metal surface unoccupied by DNA. When 6-mercapto-1-hexanol is used to fill the unoccupied places on a silver surface (as in experiments on standard gold substrates), a quick detachment of chemisorbed DNA from the silver surface is observed. Whereas, using ω-substituted alkanethiols with a shorter alkane chain makes it possible to easily form mixed DNA/backfilling thiol monolayers. Probably, the significantly lower desorption rate of the thiolated DNA induced by alkanethiols with shorter chains is due to the lower stabilization energy in monolayers formed from such compounds.     

Protein microarrays and quantum dot probes for early cancer detection

We describe here a novel approach for detection of cancer markers using quantum dot protein microarrays. Both relatively new technologies; quantum dots and protein microarrays, offer very unique features that together allow detection of cancer markers in biological specimens (serum, plasma, body fluids) at pg/ml concentration. Quantum dots offer remarkable photostability and brightness. They do not exhibit photobleaching common to organic fluorophores. Moreover, the high emission amplitude for QDs results in a marked improvement in the signal to noise ratio of the final image. Protein microarrays allow highly parallel quantitation of specific proteins in a rapid, low-cost and low sample volume format. Furthermore the multiplexed assay enables detection of many proteins at once in one sample, making it a powerful tool for biomarker analysis and early cancer diagnostics.

In a series of multiplexing experiments we investigated ability of the platform to detect six different cytokines in protein solution. We were able to detect TNF-, IL-8, IL-6, MIP-1β, IL-13 and IL-1β down to picomolar concentration, demonstrating high sensitivity of the investigated detection system.

We have also constructed and investigated two different models of quantum dot probes. One by conjugation of nanocrystals to antibody specific to the selected marker—IL-10, and the second by use of streptavidin coated quantum dots and biotinylated detector antibody. Comparison of those two models showed better performance of streptavidin QD–biotinylated detector antibody model. Data quantitated using custom designed computer program (CDAS) show that proposed methodology allows monitoring of changes in biomarker concentration in physiological range.     

Layer-by-layer deposition of rhenium-containing hyperbranched polymers and fabrication of photovoltaic cells

Multilayer thin films were prepared by the layer-by-layer (LBL) deposition method using a rhenium-containing hyperbranched polymer and poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS). The radii of gyration of the hyperbranched polymer in solutions with different salt concentrations were measured by laser light scattering. A significant decrease in molecular size was observed when sodium trifluoromethanesulfonate was used as the electrolyte. The conditions of preparing the multilayer thin films by LBL deposition were studied. The growth of the multilayer films was monitored by absorption spectroscopy and spectroscopic ellipsometry, and the surface morphologies of the resulting films were studied by atomic force microscopy. When the pH of a PTEBS solution was kept at 6 and in the presence of salt, polymer films with maximum thickness were obtained. The multilayer films were also fabricated into photovoltaic cells and their photocurrent responses were measured upon irradiation with simulated air mass (AM) 1.5 solar light. The open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency of the devices were 1.2 V, 27.1 mu A cm(-2), 0.19, and 6.1x10(-3) %, respectively. The high open-circuit voltage was attributed to the difference in the HOMO level of the PTEBS donor and the LUMO level of the hyperbranched polymer acceptor. A plot of incident photon-to-electron conversion efficiency versus wavelength also suggests that the PTEBS/hyperbranched polymer junction is involved in the photosensitization process, in which a maximum was observed at approximately 420 nm. The relatively high capacitance, determined from the measured photocurrent rise and decay profiles, can be attributed to the presence of large counter anions in the polymer film.     

Chemiluminescent reductive acridinium triggering (CRAT)--mechanism and applications

Acridinium esters traditionally are triggered using basic hydrogen peroxide. By serendipity, we have found that acridinium esters can also be triggered with emission of chemiluminescence by reductive triggering, e.g., by zinc metal or reduced forms of ferric and cupric salts. Furthermore, organic reducing compounds like dithiothreitol, tricarboxyethylphosphine or glutathione could be used in combination with organic oxidants like quinones or inorganic ferric or cupric salts. Mechanisms are proposed which involve the intermediacy of superoxide. Two forms of reactive oxygen species (i.e., hydrogen peroxide and superoxide) could be discriminated based on differences in kinetics. Some applications (improved detection of acridinium ester, use of acridinium ester as redox probes) are discussed.