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.     

252Cf plasma desorption mass spectrometric study of interactions of steroid glycosides with amino acids

252Cf Plasma desorption with time-of-flight mass spectrometry (TOF-PDMS) has been applied to comparative studies of the interactions of steroid glycosides (SGs) of the spirostan series with amino acids. SGs can interact with amino acids to form heteroclusters of the type [SG + aminoacid + H](+) and [SG + aminoacid + K](+). It is shown how the affinity of SGs for amino acids depends on the structures of both the SG carbohydrate chain and the SG aglycone, and on the nature of the amino acid side chain. Copyright 2000 John Wiley & Sons, Ltd.     

Thermal decomposition of furostanol glycoside-tomatoside

The thermal degradation of furostanol glycoside, tomatoside has been investigated by thermal analysis (TA), thin-layer chromatography (TLC) and IR-spectroscopy. The thermal curves of tomatoside were obtained under various conditions. The structures of the main intermediates were elucidated. It has been established that on heating above 150 furostanol glycoside is converted into the spirostanol one. Simultaneously the stepped splitting of the carbohydrate fraction at C-3 of the aglycone takes place. The steroid part of the glycoside is destructed at a temperature above 270. The process is identical both in air and nitrogen atmospheres.

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Zusammenfassung Mittels Thermoanalyse (TA), Dünnschichtchromatographie (TLC) und IR-Spektroskopie (IR) wurde die thermische Zersetzung von Furostanolglycosid (Tomatosid) untersucht. Die thermoanalytischen Kurven von Tomatosid wurden unter verschiedenen Bedingungen erstellt und die Struktur der wichtigsten Zwischenprodukte ermittelt. Es wurde festgestellt, da\ Furostanolglycosid beim Erhitzen über 150 in das Spirostanolglycosid übergeht. Gleichzeitig erfolgt ein schrittweises Aufspalten der Kohlenwasserstofffraktion bei Aglycon C-3. Der Steroidteil des Glycosides wird bei Temperaturen oberhalb 270 abgebaut. Die beschriebenen VorgÄnge verlaufen in Luft bzw. in Stickstoff gleicherma\en.

     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Overtone spectroscopy of some benzaldehyde derivatives

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm⁻¹ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted benzenes it is only 80% of the para-substituted shift.     

Characterisation of different polymorphs of tris(8-hydroxyquinolinato)aluminium(III) using solid-state NMR and DFT calculations

Background  

Organic light emitting devices (OLED) are becoming important and characterisation of them, in terms of structure, charge distribution, and intermolecular interactions, is important. Tris(8-hydroxyquinolinato)-aluminium(III), known as Alq₃, an organomettalic complex has become a reference material of great importance in OLED. It is important to elucidate the structural details of Alq₃ in its various isomeric and solvated forms. Solid-state nuclear magnetic resonance (NMR) is a useful tool for this which can also complement the information obtained with X-ray diffraction studies.     

Measurement of στ product of solid state laser materials by an alternative method: Application to Nd3+ doped YVO4 crystal for 4 F 3/2→4 I 11/2 transition

In this paper an alternative approach for measurement of στ product for ⁴ F _3/2→⁴ I _11/2 transition of Nd³⁺ doped YVO₄ crystal is reported. In this method a microchip laser is formed by keeping a small piece of the sample in plane-plane resonator and a diode laser (808 nm) is used for pumping. The pump power induced thermal lensing effect is used to make the cavity stable. The cavity mode area is estimated by measuring the thermal lens focal length at the threshold and the average pump area is measured by Gaussian fit to the intensity profiles of the pump beam. The value of στ product of Nd:YVO₄ crystal obtained by this method is within 10% of the reported values. The advantage of this method is that it is a simple method for direct measurement of στ product of laser crystals.