A Conversation with Shoutir Kishore Chatterjee

Shoutir Kishore Chatterjee was born in Ranchi, a small hill station in India, on November 6, 1934. He received his B.Sc. in statistics from the Presidency College, Calcutta, in 1954, and M.Sc. and Ph.D. degrees in statistics from the University of Calcutta in 1956 and 1962, respectively. He was appointed a lecturer in the Department of Statistics, University of Calcutta, in 1960 and was a member of its faculty until his retirement as a professor in 1997. Indeed, from the 1970s he steered the teaching and research activities of the department for the next three decades. Professor Chatterjee was the National Lecturer in Statistics (1985--1986) of the University Grants Commission, India, the President of the Section of Statistics of the Indian Science Congress (1989) and an Emeritus Scientist (1997--2000) of the Council of Scientific and Industrial Research, India. Professor Chatterjee, affectionately known as SKC to his students and admirers, is a truly exceptional person who embodies the spirit of eternal India. He firmly believes that ``fulfillment in man's life does not come from amassing a lot of money, after the threshold of what is required for achieving a decent living is crossed. It does not come even from peer recognition for intellectual achievements. Of course, one has to work and toil a lot before one realizes these facts.''Comment: Published in at http://dx.doi.org/10.1214/088342306000000565 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Statistics of the inverse-cascade regime in two-dimensional magnetohydrodynamic turbulence

We present a detailed direct numerical simulation of statistically steady, homogeneous, isotropic, two-dimensional magnetohydrodynamic (2D MHD) turbulence. Our study concentrates on the inverse cascade of the magnetic vector potential. We examine the dependence of the statistical properties of such turbulence on dissipation and friction coefficients. We extend earlier work sig- nificantly by calculating fluid and magnetic spectra, probability distribution functions (PDFs) of the velocity, magnetic, vorticity, current, stream-function, and magnetic-vector-potential fields and their increments. We quantify the deviations of these PDFs from Gaussian ones by computing their flatnesses and hyperflatnesses. We also present PDFs of the Okubo-Weiss parameter, which distin- guishes between vortical and extensional flow regions, and its magnetic analog. We show that the hyperflatnesses of PDFs of the increments of the stream-function and the magnetic vector potential exhibit significant scale dependence and we examine the implication of this for the multiscaling of structure functions. We compare our results with those of earlier studies

Identification of molecular mechanisms of resistance to transgenic maize producing the Cry1Fa protein in different \u3ci\u3eSpodoptera frugiperda\u3c/i\u3e populations

The use of transgenic maize event TC1507 producing the Cry1Fa insecticidal protein from the bacterium Bacillus thuringiensis has been very useful to control the target lepidopteran insect pest Spodoptera frugiperda. The extensive use of this transgenic maize event resulted in high selection pressure for development of Cry1Fa resistance in field insects in multiple locations, including Brazil, Puerto Rico and the southeastern USA. Resistance developed in Puerto Rico was characterized in the 456LS3 strain originated from that island as monogenic, autosomal recessive and associated with reduced expression of a membrane bound alkaline phosphatase (SfmALP2). Currently, we focused on identifying the allele responsible for resistance in the 456LS3 and in alternative Cry1Fa-resistant strains from Florida (FL39) and North Carolina (NCBt13). Linkage tests between resistance to TC1507 and reduced levels of SfmALP2 in 456LS3 supported absence of a genetic linkage. We identified an allele of an ATP-binding cassette subfamily C2 (SfABCC2) gene resulting in a premature stop codon and truncated protein. We tested linkage of this allele (SfABCC2mut) with resistance to TC1507 and found it cosegregated with resistance to Cry1Fa maize. The SfABCC2mut allele was also detected in field populations of S. frugiperda from Puerto Rico. Additional SfABCC2 mutant alleles were identified from S. frugiperda surviving on TC1507 plants in Puerto Rico. Characterization of a TC1507- resistant strain of S. frugiperda originated from Florida (FL39), suggested a shared resistance locus with 456LS3. We found lack of linkage between reduced SfmALP2 levels and resistance to TC1507 in FL39, and detected another variant of the SfABCC2 gene (SfABCC2mut3) that showed strong linkage with Cry1Fa maize resistance. An additional mutant allele of SfABCC2 resulting in a truncated protein was detected in the NCBt13 resistant strain from North Carolina. Our findings support linkage of different alleles of a single gene (SfABCC2) with resistance to Cry1Fa maize that evolved in diverse locations in North America. This information and the genotyping methods developed in this work are relevant to monitor and understand dispersal of resistance, and to guide refinement of current resistance management practices to extend the sustainable use of transgenic maize producing Cry insecticidal proteins

Transport, multifractality, and the breakdown of single-parameter scaling at the localization transition in quasiperiodic systems

There has been a revival of interest in localization phenomena in quasiperiodic systems with a view to examining how they differ fundamentally from such phenomena in random systems. Mo- tivated by this, we study transport in the quasiperiodic, one-dimentional (1d) Aubry-Andre model and its generalizations to 2d and 3d. We study the conductance of open systems, connected to leads, as well as the Thouless conductance, which measures the response of a closed system to boundary perturbations. We find that these conductances show signatures of a metal-insulator transition from an insulator, with localized states, to a metal, with extended states having (a) ballistic transport (1d), (b) superdiffusive transport (2d), or (c) diffusive transport (3d); precisely at the transition, the system displays sub-diffusive critical states. We calculate the beta function $\beta(g) = dln(g)/dln(L)$ and show that, in 1d and 2d, single-parameter scaling is unable to describe the transition. Further- more, the conductances show strong non-monotonic variations with L and an intricate structure of resonant peaks and subpeaks. In 1d the positions of these peaks can be related precisely to the prop- erties of the number that characterizes the quasiperiodicity of the potential; and the L-dependence of the Thouless conductance is multifractal. We find that, as d increases, this non-monotonic de- pendence of g on L decreases and, in 3d, our results for $\beta(g)$ are reasonably well approximated by single-parameter scaling.Comment: 13 pages, 6 figure

Multiscaling in Hall-Magnetohydrodynamic Turbulence: Insights from a Shell Model

We show that a shell-model version of the three-dimensional Hall-magnetohydrodynamic (3D Hall-MHD) equations provides a natural theoretical model for investigating the multiscaling behaviors of velocity and magnetic structure functions. We carry out extensive numerical studies of this shell model, obtain the scaling exponents for its structure functions, in both the low-$k$ and high-$k$ power-law ranges of 3D Hall-MHD, and find that the extended-self-similarity (ESS) procedure is helpful in extracting the multiscaling nature of structure functions in the high-$k$ regime, which otherwise appears to display simple scaling. Our results shed light on intriguing solar-wind measurements.Comment: 7 pages, 6 figure

Two-dimensional magnetohydrodynamic turbulence with large and small energy-injection length scales

Two-dimensional magnetohydrodynamics (2D MHD), forced at (a) large length scales or (b) small length scales, displays turbulent, but statistically steady, states with widely different statistical properties. We present a systematic, comparative study of these two cases (a) and (b) by using direct numerical simulations (DNSs). We find that, in case (a), there is energy equipartition between the magnetic and velocity fields, whereas, in case (b), such equipartition does not exist. By computing various probability distribution functions (PDFs), we show that case (a) displays extreme events that are much less common in case (b)

Optimal factorial designs for cDNA microarray experiments

We consider cDNA microarray experiments when the cell populations have a factorial structure, and investigate the problem of their optimal designing under a baseline parametrization where the objects of interest differ from those under the more common orthogonal parametrization. First, analytical results are given for the $2\times 2$ factorial. Since practical applications often involve a more complex factorial structure, we next explore general factorials and obtain a collection of optimal designs in the saturated, that is, most economic, case. This, in turn, is seen to yield an approach for finding optimal or efficient designs in the practically more important nearly saturated cases. Thereafter, the findings are extended to the more intricate situation where the underlying model incorporates dye-coloring effects, and the role of dye-swapping is critically examined.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS144 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org