New Insights on Modern Age Coins by Calibration-Free Laser-Induced Breakdown Spectroscopy Method and Chemometric Approaches

Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown...     

A solution of the DGLAP equation for gluon at low x

We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate εF ₂(x,Q)²/ε In Q ² using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data.     

A modified apparatus for determination of carbon in metals by the low pressure method

The low pressure method of determination of carbon in metals and alloys was modified to include certain new techniques. An isopentane slush bath dispensed with the use of liquid oxygen and the usual McLeod gauge was replaced by a differential oil manometer, which increased the sensitivity. As little as 5 μg of carbon in CaCO₃-quartz standards could be determined with a coefficient of variation of 16.0% which improved to 3.3% at the 100-μg level. The apparatus was used for the determination of carbon in metals such as uranium, zirconium and iron and in steels and cupronickel alloy.     

Parallel synthesis of PNA-peptide conjugate libraries

An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies.     

A simple autonull-type servo-controlled electronic balance for thermogravimetric applications

A simple electronic autonull-type recording balance using a helical quartz spring is described. Deviation from the null position is detected by a pair of photoemissive cells. The error signal generated across the cells as a result of weight change is processed by a servo-system which, in turn, produces an electric current in the balancing coil proportional to the force required to restore the null position. This current, recorded as the potential drop across a standard resistor, is a direct measure of the weight change.The balance has good linear response and can record weight changes up to 150 mg. The performance of the balance was tested in a thermogravimetric set-up, by studying the decomposition in air of the oxalates of copper, nickel and magnesium. The decomposition of nickel oxalate was also studied in flowing hydrogen. The weighing accuracy of the balance, compared against a Mettler model H-15 single-pan balance, was found to be within±1.5%.

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Zusammenfassung Eine einfache elektronische registrierende Quartz-Spiralfeder Kompensationswaage wird beschrieben. Die Abweichung von der Nullposition wird durch zwei Photoemissionszellen angezeigt. Das infolge der Gewichtsänderung durch die Zellen erzeugte Fehlersignal wird durch ein Servosystem empfangen, das seinerseits in der Ausgleichsspirale einen elektrischen Strom erzeugt, der proportional zur für die Wiederherstellung der Null-position benötigten Kraft ist. Dieser Strom, der als Spannungsgefälle in einem Standardwiderstand registriert wird, ist eine direkte Maßzahl der Gewichtsänderung.Die Waage zeigt ein gutes lineares Verhalten und kann Gewichtsänderungen bis zu 150 mg registrieren. Die Leistung der Waage wurde in einer thermogravimetrischen Vorrichtung durch Untersuchungen der Zersetzung der Oxalate von Kupfer, Nickel und Magnesium in Luft geprüft. Die Zersetzung von Nickeloxalat wurde auch in strömendem Stickstoff untersucht. Die Meßgenauigkeit der Waage, vergleichen mit der Einschalenwaage Mettler H-15 wurde im Bereich von±1.5% gefunden.

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Résumé On décrit une balance électronique enregistreuse simple du type auto-zéro, à hélice de quartz. La déviation de la position zéro est décelée par une paire de cellules photoémissives. Le signal de déséquilibre décelé par les photocellules et résultant d'un changement de poids, est reçu par un système asservi qui, à son tour, produit un courant électrique dans la bobine de la balance, proportionnel à la force nécessaire pour rétablir la position zéro. Ce courant, enregistré comme chute de potentiel dans une résistance étalon, est une mesure directe du changement de poids.La balance donne une bonne réponse linéaire et peut enregistrer des changements de poids allant jusqu'à 150 mg. Ses caractéristiques ont été examinées dans un montage thermogravimétrique, en étudiant la décomposition dans l'air des oxalates de cuivre, nickel et magnésium. La décomposition de l'oxalate de nickel a aussi été étudiée sous courant d'hydrogène. L'exactitude de la balance, comparée à celle d'un modèle Mettler monoplateau (type H-15), coïncide à±1.5%.

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The authors wish to express their thanks to Mr. S. P. Sen, Manager. Catalyst Development and Production Department of Fertilizer (Planning and Development) India Limited, for his keen interest and valuable suggestions.     

Polymerization initiated by ylide: Polymerization of ethyl methacrylate with the use of 4-picolinium p-chloro phenacylide as initiator

The ylide 4-picolinium, p-chloro phenacylide-initiated thermal polymerization of ethyl methacrylate (EMA) was studied. 4-Picolinium p-chloro phenacylide induces the thermal polymerization of ethyl methacrylate at 65°C. The rate of polymerization (R_p) rose as the initiator concentration increased from 2 × 10^?3 to 4 × 10^?3 M and the initiating exponent was computed as 1.9. The R_p decreased as the concentration of ylide increased from 6 × 10^?2 to 1M. The greater initiator concentration also affected the molecular weight inversely. The polymerization was carried out at different temperatures and the overall activation energy was computed as 4.08 Kcal/mol. Polymerization was inhibited in the presence of hydroquinone as a radical scavenger. Kinetic studies and other data show that the overall polymerization takes place in a radical mechanism. The various kinetic parameters, such as the rate and average degree of polymerization, molecular weight, and energy of activation of the present system, were evaluated.     

Kinetics of the Ru(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The rate of oxidation of formaldehyde is directly proportional to [Fe(CN) _3– ⁶ ] while that of acetaldehyde is proportional tok[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]}, wherek, k andk are rate constants. The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0. The rate of reaction is proportional to [Ru(III)] _T in each case. A suitable mechanism is proposed and discussed.

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Die Kinetik der Ru(III)-katalysierten Oxidation von Formaldehyd und Acetaldehyd mittels alkalischem Hexacyanoferrat(III)

Zusammenfassung Die Untersuchung der Kinetik erfolgte spektrophotometrisch. Die Geschwindigkeitskonstante der Oxidation von Formaldehyd ist direkt proportional zu [Fe(CN) _3– ⁶ ], währenddessen die entsprechende Konstante für Acetaldehyd proportional zuk[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]} ist, wobeik,k undk Geschwindigkeitskonstanten sind. Die Reaktionsordnung für Acetaldehyd ist eine erste, die für Formaldehyd fällt von erster bis zu nullter Ordnung. Die Geschwindigkeitskonstante ist in jedem Fall proportional zu [Ru(III)] _T . Es wird ein passender Mechanismus vorgeschlagen.

     

Reatarding effect of nitrogen ylide for the polymerization of N-vinyl pyrrolidone

-Picolinium-p-chlorophenacylide (-PCFY) acts as a retarder for polymerization of N-vinyl pyrrolidone. The polymerization runs were carried out at 60°C using benzene as an inert solvent. The kinetic equation for the present system may be written asR _p [-PCPY]^–1.0 [AIBN]^0.66[N-VP]^1.0. The value of overall energy of activation for polymerization in presence and absence of-PCPY was computed as 44.0 and 42.3 kJ mol^–1, respectively. The inverse relationship ofR _p and¯M _v with-PCPY suggests that-PCPY acts as a polymerization retarder. The retarding effect is also evidenced by higher initiator exponent value and higher value of energy of activation in presence of ylide. A mechanism is also proposed in which polymer propagating chain combines with one ylide component to give resonance stabilized radical.     

Ethylenically unsaturated polycarbosiloxanes for novel silicone hydrogels: synthesis,end‐group analysis,contact lens formulations,and structure–property correlations

A series of novel mono‐ethylenically unsaturated polycarbosiloxanes macromonomers as compatibilizer materials for soft silicon hydrogels were prepared from the anionic ring‐opening polymerization (AROP) of 2,2,5,5‐tetramethyl‐2,5‐disila‐1‐oxacyclopentane followed by methacrylation. The characterization was performed by end‐group analysis and included the determination of molecular weight, molecular weight distributions, end‐group functionality, and impurity profiles using gas chromatography‐mass spectrometry, gel permeation chromatography, nuclear magnetic resonance, and matrix‐assisted laser desorption/ionization time of flight mass spectrometry. The synthetic procedure was optimized to minimize the formation of any dimer that would have the potential to act as a low molecular weight cross linker. In addition, the novel di‐ethylenically unsaturated polycarbosiloxanes were synthesized by cationic polymerization. Use of these silicone derivatives was explored in the formulation of contact lenses, and the structure–property relationship was examined. When copoymerized with hydrophilic monomers, these were able to give transparent and wettable films with desired properties, particularly a low moduli for contact lenses. Contact lens with high modulus is often shown to impart a higher degree discomfort when worn upon the eye. It was clear from the structure–property relationship that the modulus and the tensile strength of the formulated material depend on the nature and length of the polycarbosiloxane used and may be tuned for the purpose as needed. Copyright © 2013 John Wiley & Sons, Ltd.