A simple and effective method for smoothing DSC curves

All known procedures of smoothing are limited by the beginning of falsification of the signals. We suggest a simple modification of the moving average of the polynomial smoothing procedure. The signal curve is smoothed to the best degree and independently of the special problem within an interval calculated from then-th multiple of the standard deviation of the noise.

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Zusammenfassung In einigen Fällen (Bildung von Ableitungen, Entschmierungsrechnungen, Auswertung schwacher Effecte) ist auch bei der DSC-Technik eine Glättung des primären Signals angebracht. Alle bekannten Verfahren beinhalten immer einen Kompromiß zwischen erreichter Glättung und beginnender, nicht mehr zu vernachlässigender Verfälschung der Analysenergebnisse. Zudem erfordert jedes Problem seine eigenen optimalen Glättungsparameter. Wir schlagen eine einfache und universell anwendbare Modifikation des Verfahrens mit gleitender Mittelwertsbildung bzw. unter Verwendung der Golay-Sawitzky-Filter vor. In einem Streifen, der aus einem vorgebbaren Vielfachen der Standardabweichung des Rauschens gebildet wird, erhält man so eine optimale Glättung.

     

A simple and effective method for phosphoryl transfer using TiCl(4) catalysis

[reaction: see text] A number of Lewis acids have been evaluated as catalysts for the phosphoryl transfer, the most efficient being TiCl(4). Application of this methodology to the phosphorylation of a number of representative target alcohols is presented     

A modular flow reactor for performing Curtius rearrangements as a continuous flow process

The use of a mesofluidic flow reactor is described for performing Curtius rearrangement reactions of carboxylic acids in the presence of diphenylphosphoryl azide and trapping of the intermediate isocyanates with various nucleophiles.     

A simple method for the microdetermination of carbon and hydrogen using nitrogen as a transport gas

Summary A simple and quick method for the microdetermination of carbon and hydrogen is described. The substance is oxidized by copper oxide and the combustion gases are transported by nitrogen. Nitrogen oxides are removed by reduced copper. Sulphur-containing compounds are combusted over manganese oxide-silver oxide catalyst. With one filling more than 300 analyses can be performed.

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Zusammenfassung Eine einfache und schnelle Methode zur Mikrobestimmung von Kohlenstoff und Wasserstoff wurde beschrieben. Die Substanz wird mit Kupferoxid oxydiert, als Transportgas dient Stickstoff. Stickstoffoxide werden mit reduziertem Kupfer entfernt. Schwefelhältige Verbindungen werden über einem Manganoxid-Silberoxid-Katalysator verbrannt. Eine Rohrfüllung reicht für mehr als 300 Analysen.

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Résumé On décrit une méthode simple et rapide pour le microdosage du carbone et de l'hydrogène. On oxyde la substance par l'oxyde de cuivre et l'on utilise l'azote comme gaz vecteur pour les gaz de combustion. On élimine les oxydes de l'azote par le cuivre réduit. On brûle les composés contenant du soufre sur catalyseur manganèse-oxyde d'argent. Un seul remplissage permet de réaliser plus de 300 analyses.

     

A simple and effective boundary model in nonequilibrium molecular dynamics method

We propose a simple and effective boundary model in a nonequilibrium molecular dynamics (NEMD) simulation to study the out-of-equilibrium dynamics of polymer fluids. The present boundary model can effectively weaken the depletion effect and the slip effect near the boundary, and remove the unwanted heat instantly. The validity of the boundary model is checked by investigating the flow behavior of dilute polymer solution driven by an external force. Reasonable density distributions of both polymer and solvent particles, velocity profiles of the solvent and temperature profiles of the system are obtained. Furthermore, the studied polymer chain shows a cross-streaming migration towards center of the tube, which is consistent with that predicted in previous literatures. These numerical results give powerful evidences for the validity of the present boundary model. Besides, the boundary model can also be used in other flows in addition to the Poiseuille flow.     

A simple method for epoxidation of olefins using sodium chlorite as an oxidant without a catalyst

[Reaction: see text]. Sodium chlorite has been demonstrated to be capable of epoxidizing a variety of olefins at 55-65 degrees C (oil bath). Chlorine dioxide is believed to be the pivotal epoxidizing agent in the reaction on the basis of the mechanistic studies.     

Dynamic method as a simple approach for wide range pH measurements using optodes

In this paper, a flow system equipped with an optode has been suggested for wide range pH measurements. Triacetyl cellulose was used as the optode membrane in which different pH indicators were immobilized. For extending the pH range, the dynamic response rather than the steady-state response of the optode was measured. Since diffusion is the main process governing the system response, different parameters having influence on diffusion of the analyte into the membrane were optimized. Under the optimum conditions, wide range pH determination (up to 11 pH units) is simply achieved regardless of the pK_a of the pH indicator immobilized in the membrane. To validate the application of the method different indicators with different structures and pK_a values were tested and the results were all confirming the precision and accuracy of the method. The suggested method also has combined advantages of flow systems together with inherent advantages of kinetic systems.     

A general method for designing combinatorial peptide libraries decodable by amino acid analysis

Herein we describe an algorithm for designing combinatorial peptide libraries for split-and-mix synthesis on solid support that are decodable by amino acid analysis (AAA) of the beads. AAA is a standard service analysis available in most biochemical laboratories, and it allows one to control the quality of the peptide on each bead, an important feature that is missing from most library decoding protocols. In the algorithm, each AA is assigned to two variable positions in the sequence grouped in a "unique pair". This arrangement limits sequence design because both the number of unique pairs U (setting the maximum number of variable AA) and the maximum number S of different AA per variable position depend on the peptide length N (U=N(N-1)/2), S=N-1). The method is therefore only suitable for focused libraries. An application example is shown for the selection of peptides with N-terminal proline or hydroxyproline catalyzing an aldol reaction from a combinatorial library of 65536 octapeptides. A simple enumeration program is available to help design combinatorial libraries decodable by amino acid analysis. The method applies to linear and cyclic peptides, can be used for nonnatural building blocks, including beta-amino acids, and should help to explore the vast chemistry of linear and cyclic peptide for catalysis and bioactivity.     

A simple and effective method for the purification of californium from other elements

The distribution coefficients of californium and other elements between an anion exchange resin and alcohol solutions of nitric acid of different concentrations have been determined. An effective method is suggested for the purification of californium from other elements which are slightly adsorbed when Cf is concentrated on an anion exchanger from 0.5–1.0N solutions of nitric acid containing 95–90% alcohol; Cf is subsequently eluted with a 0.5N HNO₃ solution in 85% CH₃OH and simultaneously separated from the elements which are strongly adsorbed on the anion exchange resin. Under the chosen conditions the coefficients of californium purification were determined for a number of elements; the values are 5.4·10²–1.8·10³ for Al, Ca, Fe and ∼10³–10⁵ for Am, Pm, Nd, Ce, Pb, Bi and Na, for one cycle.     

A simple method for a determination

The a term is a primary parameter that is used to indicate the deviation of the epithermal neutron distribution in the k ₀-standardization method of neutron activation analysis, k ₀-NAA. The calculation of a using a mathematical procedure is a challenge for some researchers. The calculation of a by the "bare-triple monitor" method is possible using the dedicated commercial software KAYZERO^®/SOLCOI^®. However, when this software is not available in the laboratory it is possible to carry out the calculation of a applying a simple iterative linear regression using any spreadsheets. This approach is described in this paper. The experimental data used in the example were obtained by the irradiation of a set of suitable monitors in the NAA #1 irradiation channel of the HANARO research reactor (KAERI, Korea). The results obtained by this iterative linear regression method agree well with the results calculated by the validated mathematical method.     

Cyclic peptide nanocapsule as ion carrier for halides: a theoretical survey

In this work, the encapsulations of halide ions including F^?, Cl^?, and Br^? by cyclic peptide nanocapsule as ion carrier (F^?, Cl^?, and Br^? @(Ala4...Ala4)) were investigated using the dispersion corrected density functional theory (DFT) employing CAM-B3LYP functional and the 6–311?+?G (d, p) basis set in the gas phase. The electronic binding energy (E_bind), binding enthalpy (H_bind), and binding Gibbs free energy (G_bind) for each anion were calculated and showed that the stability order of the complexes based on their calculated E_bind is F^??>?Cl^??>?Br^? @(Ala4...Ala4). The calculated value of G_bind for F^? @(Ala4...Ala4) was ??29.77 kcal/mol showing the formation of this complex is thermodynamically favorable while the formation of Br^? @(Ala4...Ala4) is 14.35 kcal/mol which shows that the encapsulation of Br^? is not possible. The calculated value of G_bind for Cl^? @(Ala4...Ala4) was ??0.57 kcal/mol which shows that Cl^? ion can be reversibly stored inside the nanocapsule. The NBO analysis was also performed to investigate the charge transfer between two cyclic peptides in the complexes and also between the anion and the nanocapsule. The NBO analysis showed that the strongest hydrogen bonds between two cyclic peptides are in the complex.     

A catalytic method for the determination of trace osmium in continuous flow and flow injection systems

A procedure has been developed for the determining osmium using a catalytic indicator reaction of arsenic(III) oxidation with potassium bromate and neutral red in continuous flow and flow injection systems. The possibilities of the flow systems have been compared on an example of the proposed reaction, and the regularities of this reaction conducted in different flow systems have been revealed. Recommendations on the choice of the optimal variant of the flow system are given. The accuracy of the procedure has been confirmed by the results of determining osmium in a State Reference Sample.     

Injectable solid peptide hydrogel as a cell carrier: effects of shear flow on hydrogels and cell payload

β-hairpin peptide-based hydrogels are a class of injectable solid hydrogels that can deliver encapsulated cells or molecular therapies to a target site via syringe or catheter injection as a carrier material. These physical hydrogels can shear-thin and consequently flow as a low-viscosity material under a sufficient shear stress but immediately recover back into a solid upon removal of the stress, allowing them to be injected as preformed gel solids. Hydrogel behavior during flow was studied in a cylindrical capillary geometry that mimicked the actual situation of injection through a syringe needle in order to quantify effects of shear-thin injection delivery on hydrogel flow behavior and encapsulated cell payloads. It was observed that all β-hairpin peptide hydrogels investigated displayed a promising flow profile for injectable cell delivery: a central wide plug flow region where gel material and cell payloads experienced little or no shear rate, and a narrow shear zone close to the capillary wall where gel and cells were subject to shear deformation. The width of the plug flow region was found to be weakly dependent on hydrogel rigidity and flow rate. Live-dead assays were performed on encapsulated MG63 cells 3 h after injection flow and revealed that shear-thin delivery through the capillary had little impact on cell viability and the spatial distribution of encapsulated cell payloads. These observations help us to fundamentally understand how the gels flow during injection through a thin catheter and how they immediately restore mechanically and morphologically relative to preflow, static gels.     

Screening of inhibitors for influenza A virus using high-performance affinity chromatography and combinatorial peptide libraries

The affinity inhibitor of fusion peptide of influenza A virus has been studied using a combination of high-performance affinity chromatography (HPAC) and combinatorial peptide libraries. Fusion peptide (FP) (1-11) of influenza A virus was used as the affinity ligand and immobilized onto the poly(glycidyl methacrylate) (PGMA) beads. Positional scanning peptide libraries based on antisense peptide strategy and extended peptide libraries were designed and synthesized. The screening was carried out at acidic pH (5.5) in order to imitate the environment of virus fusion. A hendecapeptide FHRKKGRGKHK was identified to have a strong affinity to the FP (1-11). The dissociation constant of the complex of the hendecapeptide and the FP (1-11) is 3.10 x 10(-6) mol l(-1) in a physiological buffer condition. The polypeptide has a fairly inhibitory effect on three different strains of influenza A virus H1N1 subtype.     

A method for determining argon isotopes in a continuous helium flow for K/Ar geochronology

A new method for the measurement of the argon isotope composition in a continuous helium flow using isotope mass spectrometers is described for potassium-argon geochronology. Argon was extracted from the samples in a chamber with a multiple-sample holder by successively heating the samples with a continuous infrared laser. Argon extracted in the chamber was preconcentrated in a capillary, separated on a chromatographic capillary column in a helium flow, and then injected into the ion source of a mass spectrometer through an open splitter. Measurements of the ³⁶Ar, ³⁸Ar, and ⁴⁰Ar isotopes were carried out on isotope mass spectrometers in a dynamic mode using a triple-collector ion detector and three electrometric amplifiers. Preliminary experiments on the developed device for measuring argon isotopes in a continuous helium flow have shown that the proposed method can be used for the determination of radiogenic argon in an amount of n × 10^?12 g with the accuracy satisfying the solution of many geochronological problems. In sensitivity and reproducibility, the proposed method is highly competitive to the isotope dilution method for measuring argon and simpler than the conventional methods for measuring radiogenic argon.     

A simple continuous titration method for the investigation of flame atomization processes

For detailed investigations of the interactions between sample components in flames, devices were designed to attain either a quasi-linear or an exponential AAS titration process. When applying these instruments the concentration of one of the solute components remains constant during titration, while the other component varies according to the functions mentioned. The signal of the component with constant concentration is followed continuously with a strip-chart recorder. The operation with these inexpensive devices is simple and they can be regarded as effective tools in studying analytical interference effects and flame reactions.     

Seeded polymerization as a method for producing hollow monodisperse microspheres

Crosslinked hollow monodisperse microspheres with diameters of 1.9–5.9 μm and one- or two-layer shells, with the layers being based on polymers of different natures, are produced by one- and two-stage seeded copolymerization of styrene and/or methyl methacrylate with ethylene glycol dimethacrylate or allyl methacrylate as crosslinking agents. Factors determining the morphology and dispersity of the microspheres are revealed. It is shown that, when, at the final stage of the synthesis, the content of a crosslinking agent in the reaction mixture is at least 50 wt %, the produced microspheres retain their size and morphology after exposure in toluene and dimethylformamide.     

Ion exchange as a simple and effective tool for screening possible cation conductors

Although kinetics of the low-temperature cation exchange in mixed oxide materials (aluminates, gallates, titanates, niobates, tantalates, antimonates, phosphates etc.) cannot provide quantitative information on self-diffusion and ionic conductivity in the starting material due to the mixed cation effect, it is the most direct and simple qualitative indication of the cation mobility in the solid state. It does not need using ceramics and single crystals and thus represents a useful tool for rapid selection of prospective cation conductors for subsequent detailed studies of dense samples with electrical methods. Examples of solid electrolytes discovered owing to their ion-exchange properties are reviewed, and rational principles of the ion-exchange testing are discussed. Laws of ion-exchange equilibria are based on ionic size compliance and the principle of hard and soft acids and bases. The former is most important for alkali/alkali exchange and the latter for exchanging cations of similar size but having different electronic structures: those of the rare-gas type and those having 18- or 18 + 2-electron shells, like Na⁺ and Ag⁺ or K⁺ and Tl⁺. Ion-exchange testing is especially useful for structures with non-intersecting conduction paths. It is shown that the resistivity of crystals with non-parallel and non-intersecting conduction paths cannot be described by the classical tensor formalism. Significant differences between isotope exchange, chemical ion exchange and ion conduction, quasi-one-dimensional and true one-dimensional conductors and single- and multiple-barrelled non-intersecting channels are disclosed and discussed.