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.     

Effect of Fe addition on the crystallization behaviour and Curie temperature of CoCrSiB-based amorphous alloys

The crystallization behaviour and Curie temperature of melt-spun Co_{71? x} Fe _x Cr₇Si₈B₁₄ (x?=?0, 2, 3.2, 4, 6, 8 and 12?at.%) amorphous alloys have been studied. Differential scanning calorimetry (DSC) showed two stages of crystallization. The first stage of crystallization (T _X1) in the alloy with 6?at.%?Fe was the highest and it had the highest activation energy. X-ray diffraction studies revealed that the primary crystalline phase is hcp-(CoCr)₂Si for Fe-free alloy, whereas (CoFeCr)₂Si and (CoFeCr)₃Si phases were formed with the addition of Fe. hcp-Co was also formed along with these phases. The secondary crystalline phases were fcc-Co and various boron-rich phases. The Curie temperature of the alloys also changed with the addition of Fe to the system. Like the primary crystallization temperature, the Curie temperature of the alloys did not vary systematically with the Fe content. The addition of Fe to the Co-based system changes the nearest-neighbour interaction. This changes the exchange interaction between the transition metal elements. Due to the asymmetry in the Bethe–Slater curve, a systematic variation with Fe addition was not observed in the Curie temperature measurement.     

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.     

Estimation of the film thickness from the cohesive pressure at the air water interface

Summary The pressure-area curves for neutral monolayers of butyric, valeric, caproic and caprylic acids at the airwater interface were obtained from the surface tension concentration data. Similar curves for the charged monolayers of sodium octanoate and sodium lauryl sulphate in the presence and absence of excess neutral salts were constructed on the basis of the results on surface tension. From the comparison of the pressure area curves of each of these monolayers at air-water and oil-water interfaces under identical conditions, the cohesive pressures of the monolayer at the air-water interface were calculated for different areas per adsorbed molecule using the equation ofDavies. The cohesive pressure was observed to vary linearly with the square of the reciprocal area per adsorbed molecule or ion. From the slope of such linear plot, magnitude of the two-dimensionalvan der Waals constant in each case was estimated. The thickness of the interfacial film was estimated from the comparison of the values of two- and three-dimensionalvan der Waals constants. This is, however, found to be considerably greater than the length of the stretched molecules adsorbed at the interface. When correction for entropy, as suggested byGershfeld is introduced, the film thickness becomes identical with the length of the molecule. Based in part upon the thesis submitted byA. K. Chatterjee for the Ph. D. degree of the Jadavpur University (1966).     

Adsorption der organischen zweibasischen Säuren an flüssigen Grenzflächen. I. Neutrale Einzelschichten der nichtionisierten Säuren

Ohne Zusammenfassung     

Stability and electrokinetic potential of thorium oxide sol (Part II)

Summary The electrokinetic potential of an impure thorium oxide sol (sol-II) dialysed for three weeks only, has been measured both by endomosis and by electrophoresis and the data obtained have been compared with those obtained in the case of the well-dialysed sol (sol-I). For slow rates of coagulation, the true ζ-potential of sol-II obtained by electro-osmosis and electrophoresis are found to be nearly identical. The difference between the true ζ-potentials for slow and rapid rates of coagulation is small, thus indicating the existance of critical zone of ζ-potential for coagulation. The values of true ζ-potentials for sol-II are, however, found to be slightly less than the corresponding values obtained for purified sol-I. This difference has been explained to be due to the considerable change in the coagulating concentrations of electrolytes and also to the change in composition and properties of thorium oxide sol by the change in the time of dialysis.

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Zusammenfassung Das elektrokinetische Potential eines unreinen Thoriumoxyd-Sols (Sol II) wurde nur drei Wochen dialysiert, auf beide Arten, mit Endosmose und Elektrophorese untersucht und die erhaltenen Daten wurden mit dem Fall des gut dialysierten Soles (Sol I) verglichen. Bei langsamen Koagulationsgeschwindigkeiten ist das wahre Zeta-Potential von Sol II mit Elektroosmose und Elektrophorese gemessen nahezu identisch. Die Differenz zwischen wahren Zeta-Potentialen für langsame und rasche Koagulation ist gering. Die Werte des wahren Zeta-Potentials für Sol II liegen jedoch etwas niedriger als die entsprechenden Werte für das gereinigte Sol I. Dieser Unterschied wird den betr?chtlichen Abweichungen in der Konzentration der Elektrolyte und auch den ?nderungen in der Zusammensetzung und den Eigenschaften des Thoriumoxyd-Sols bei ver?nderter Dialysezeit zugeschrieben.

     

Universal additive effect of temperature on the rheology of amorphous solids

Extensive measurements of macroscopic stress in a 2D Lennard-Jones glass, over a broad range of temperatures (T) and strain rates (γ), demonstrate a very significant decrease of the flowing stress with T, even much below the glass transition. A detailed analysis of the interplay between loading, thermal activation, and mechanical noise leads us to propose that over a broad (γ, T) region, the effect of temperature amounts to a mere lowering of the strains at which plastic events occur, while the athermal avalanche dynamics remains essentially unperturbed. Up to the vicinity of the glass transition, temperature is then shown to correct the athermal stress by a (negative) additive contribution which presents a universal form, thus bringing support to and extending an expression proposed by Johnson and Samwer [Phys. Rev. Lett. 95, 195501 (2005)].     

Multiple ionization of argon in coincidence with projectile ions in 60–120 MeV Si q+-Ar collisions

A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer processes in collisions of 60–120 MeV Si ^q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization, electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated. The data reported on the present collision system result from a direct measurement in the considered impact energy for the first time. The total ionization cross-sections for the recoil ions are shown to scale as q ^1.7/E _p ^0.5 , where E _p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j ² upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing cross-sections σ _qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow our data for different ionization processes is reviewed and discussed.