Production of pulsed ultraslow muons and first μSR experiments on thin metallic and magnetic films

Standard muon spin rotation (μSR) spectroscopy implants 4 MeV spin-polarized positive muons to investigate the bulk properties of matter. Success in producing epithermal muons opens interesting possibilities for studying ultrathin films, interfaces, and even surfaces. At the ISIS Facility, Rutherford Appleton Laboratory (Chilton, UK), we have produced a pulsed ultraslow muon beam (E< 20 eV) and have performed the first μSR experiments. Due to the pulsed feature, the implantation time is automatically determined and, by adjusting the final muon energy between about 8 and 20 eV, depth slicing experiments are possible down to monolayers distances. We describe slicing experiments across a 20 nm copper film on quartz substrate with evidence for a 2 nm copper oxide surface layer. A preliminary experiment on a hexagonal cobalt film suggests the existence of muon precession in the local magnetic field. The results are discussed in relation to the morphological features of the film.     

Application of particle induced gamma-ray emission for non-destructive determination of fluorine in barium borosilicate glass samples

Barium borosilicate glass (BaBSG) is proposed as a potential candidate for vitrification of nuclear waste generated from thoria based nuclear reactors. Along with fission products, activation products and many inactive chemicals, like fluorine in the form of HF are expected to be present in the dissolver solution with nuclear waste. As vitrification occurs at high temperature, it is important to quantify fluorine in BaBSG. Due to its complex matrix, most of the wet chemical and nuclear analytical methods encounter problems in the estimation of fluorine. Particle induced γ-ray emission (PIGE) method has been standardized for non-destructive determination of fluorine contents in BaBSG samples utilizing measurement of prompt gamma-rays from ¹⁹F (p, p’γ) ¹⁹F reaction. Experiments have been carried out with thick pellet targets prepared in cellulose matrix using 4 MeV proton beam from the folded tandem ion accelerator at BARC, Mumbai. For obtaining current normalized count rate of interest, beam current variation was monitored by the Rutherford backscattering spectrometry (RBS) method as well as by the in situ approach using an externally added element sensitive to PIGE. In this paper standardization of PIGE methods for F determination, validation of methods using synthetic samples, and application to BaBSG samples are reported.     

Thin-film flow over a nonlinear stretching sheet

A thin viscous liquid film flow is developed over a stretching sheet under different nonlinear stretching velocities. An evolution equation for the film thickness, is derived using long-wave approximation of thin liquid film and is solved numerically by using the Newton–Kantorovich method. A comparison is made with the analytic solution obtained in [B. S. Dandapat, A. Kitamura, B. Santra, “Transient film profile of thin liquid film flow on a stretching surface”, ZAMP, 57, 623-635 (2006)]. It is observed that all types of stretching produce film thinning but non-monotonic stretching produces faster thinning at small distance from the origin. The velocity u along the stretching direction strongly depends on the distance along the stretching direction and the Froude number.     

Effects of gamma irradiation on long-storage seeds of Oryza sativa (cv. 2233) and their surface infecting fungal diversity

We have reported an effective ⁶⁰Co gamma irradiation method for the removal and long-time prevention of contaminating fungi of Oryza sativa cv-2233, without the losses of seed viabilities. The fungal growth and their population on gamma treated seeds was found to decrease significantly (p<0.05) with the increasing irradiation dose and storage time. Immediately after irradiation, the depletion of fungal population on rice seed was noticed (>50%) at 2 kGy, whereas total inhibition was noticed at 3 kGy after 1.5 month.     

Coupling of o and/or m-substituted arylamines with the ortho-C–H function of the pendant aryl ring in coordinated arylazopyrimidinepalladium(II) complexes. Spectral and electrochemical characterisation of the products

2-(Arylazo)pyrimidines (aapm) are N,N-chelators which form palladium(II) complexes, Pd(aapm)Cl₂ (1). The reaction of Pd(aapm)Cl₂ (1) with arylamines (ArNH₂) yields Pd(aapm-N-Ar)Cl, (2)–(7), complexes of the tridentate N,N,N-donor system in which arylamines are fused to the ortho C–H function of the pendant aryl ring in the coordinated 2-(arylazo)pyrimidine, leading to the C–N coupled product. Pd(aapm-N-Ar)Cl, complexes (2)–(7), exhibit a broad intense absorption band in n.i.r. region (870–920 nm), while the parent complex, Pd(aapm)Cl₂, shows an intense absorption at 425 nm. Cyclic voltammograms of (2)–(7) exhibit an oxidation couple at positive potential to s.c.e. together with three reductions at negative side. The oxidation may involve conversion of the chelated azoarylamine to semibenzoquinone azoarylamine fragment. The reduction is due to the accommodation of electrons in the azoimine function. The absorption spectra in the n.i.r. region may be regarded as HOMO LUMO intravalence charge transfer (i.v.c.t.) transitions.     

Anisotropic cosmological models and generalized scalar tensor theory

In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely, axially symmetric Bianchi-I, Bianchi-III and Kortowski-Sachs space-time. For bulk viscous fluid, both exponential and power-law solutions have been studied and some assumptions among the physical parameters and solutions have been discussed.     

Size distribution of different types of sites in Abelian sandpile avalanches

The avalanches in the Abelian sandpile model have a compact structure and consist of shells. The different shells consist solely of sites that have toppled a fixed number of times. For the outermost shell the number is one and increases successively by one from an outer shell to the next inner shell. In this paper, we determine the size-distribution exponents of various categories of sites: sites that have toppled at least once, at least twice, at least thrice, only once and only twice. A particular subclass of avalanches is identified which have no shell structure and consist solely of sites which have toppled only once. The size distribution exponent of this type of clusters is determined.     

Facile synthesis of aliphatic hyperbranched polyesters based on diethyl malonate and their irreversible molecular encapsulation

Synthesis of diethyl malonate based wholly aliphatic hyperbranched polyesters having suitable polar matrix for irreversible molecular encapsulation is carried out for the first time.