<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

(SoNS) School of Natural Sciences

Background. Stem cell factor (SCF) receptor c-Kit is recognized as a key signaling molecule, which transduces signals for the proliferation, differentiation and survival of stem cells. Binding of SCF to its receptor triggers transactivation, leading to the recruitment of kinases and phosphatases to the docking platforms of c-Kit catalytic domain. Tyrosine phosphatase-1 (Shp-1) deactivates/attenuates 'Kit' kinase activity. Whereas, Asp816Val mutation in the Kit activation loop transforms kinase domain to a constitutively activated state (switch off-to-on state), in a ligand-independent manner. This phenomenon completely abrogates negative regulation of Shp-1. To predict the possible molecular basis of interaction between c-Kit and Shp-1, we have performed an in silico protein-protein docking study between crystal structure of activated c-Kit (phosphorylated c-Kit) and full length crystal structure of Shp-2, a close structural counterpart of Shp-1. Findings. Study revealed a stretch of conserved amino acids (Lys818 to Ser821) in the Kit activation domain, which makes decisive H-bonds with N-sh2 and phosphotyrosine binding pocket residues of the phosphatase. These H-bonds may impose an inhibitory steric hindrance to the catalytic domain of c-Kit, there by blocking further interaction of the activation loop molecules with incoming kinases. We have also predicted a phosphotyrosine binding pocket in SH2 domains of Shp-1, which is found to be predominantly closer to a catalytic groove like structure in c-Kit kinase domain. Conclusions. This study predicts that crucial hydrogen bonding between N-sh2 domain of Shp-1 and Kit activation loop can modulate the negative regulation of c-Kit kinase by Shp-1. Thus, this finding is expected to play a significant role in designing suitable gain-of-function c-Kit mutants for inducing conditional proliferation of hematopoietic stem cells. © 2010 Mukhopadhyay et al; licensee BioMed Central Ltd.

Life Sciences

World University root node

Fulltext

BMC Research Notes

The structural insights of stem cell factor receptor (c-Kit) interaction with tyrosine phosphatase-2 (Shp-2): An in silico analysis

Hyperactivation of phosphatidylinositol-3 kinase (PI3K) can occur as a result of somatic mutations in PIK3CA, the gene encoding the p110α subunit of PI3K. The HER2 oncogene is amplified in 25% of all breast cancers and some of these tumors also harbor PIK3CA mutations. We examined mechanisms by which mutant PI3K can enhance transformation and confer resistance to HER2-directed therapies. We introduced the PI3K mutations E545K and H1047R in MCF10A human mammary epithelial cells that also overexpress HER2. Both mutants conferred a gain of function to MCF10A/HER2 cells. Expression of H1047R PI3K, but not E545K PI3K, markedly upregulated the HER3/HER4 ligand heregulin (HRG). HRG siRNA inhibited growth of H1047R but not E545K-expressing cells and synergized with the HER2 inhibitors trastuzumab and lapatinib. The PI3K inhibitor BEZ235 markedly inhibited HRG and pAKT levels and, in combination with lapatinib, completely inhibited growth of cells expressing H1047R PI3K. These observations suggest that PI3K mutants enhance HER2-mediated transformation by amplifying the ligand-induced signaling output of the ErbB network. This also counteracts the full effect of therapeutic inhibitors of HER2. These data also suggest that mammary tumors that contain both HER2 gene amplification and PIK3CA mutations should be treated with a combination of HER2 and PI3K inhibitors. © 2010 Macmillan Publishers Limited All rights reserved.

Oncogene

H1047R phosphatidylinositol 3-kinase mutant enhances HER2-mediated transformation by heregulin production and activation of HER3

Very low frequency (VLF) hiss emissions were observed for the first time at the Indian Antarctic Station, Maitri (geographic lat. 70°46′S, long. 11°50′E, geomagnetic lat. 66°.03′S, long. 53°.21′E) with the modulating intensity variations. Various spectrograms of modulating VLF hiss emissions clearly show band limited spectra regularly modulating its intensity with almost equal period of the order of few seconds in the frequency range of 9-12.8 kHz. To explain these modulating characteristics of VLF hiss, we propose that the hiss emissions are generated through Doppler-shifted cyclotron interactions near the geomagnetic equator and propagate towards the Earth in the whistlermode. Further, the micropulsations propagating along the geomagnetic field lines could modulate the growth rate of the wave. The growth rates of the waves are also computed.

Current Science

Characteristics of modulating VLF hiss observed at Indian Antarctic Station, Maitri (L = 4.5)

A copolymer comprising 1,4-diketopyrrolo[3,4-c]pyrrole (DPP) and thieno[3,2-b]thiophene moieties, PDBT-co-TT, shows high hole mobility of up to 0.94 cm2 V-1 s-1 in organic thin-film transistors. The strong intermolecular interactions originated from π-π stacking and donor-acceptor interaction lead to the formation of interconnected polymer networks having an ordered lamellar structure, which have established highly efficient pathways for charge carrier transport. © 2010 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Physics

Advanced Materials

A high mobility P-type DPP-thieno[3,2-b]thiophene copolymer for organic thin-film transistors

Random matrix model for the Nakagami-q (Hoyt) fading in multiple-input multiple-output (MIMO) communication channels with arbitrary number of transmitting and receiving antennas is considered. The joint probability density for the eigenvalues of H† H† (or {H H†), where H† is the channel matrix, is shown to correspond to the Laguerre crossover ensemble of random matrices and is given in terms of a Pfaffian. Exact expression for the marginal density of eigenvalues is obtained as a series consisting of associated Laguerre polynomials. This is used to study the effect of fading on the Shannon channel capacity. Exact expressions for higher order density correlation functions are also given which can be used to study the distribution of channel capacity. © 2010 IEEE.}, author_keywords={Channel capacity; Fading distributions; Hoyt distribution; Laguerre crossover ensemble; Multiple-input multiple-output (MIMO) channels; Nakagami-q distribution; Random matrices}, keywords={Hoyt distribution; Laguerre; Multiple-input multiple-output channels; Nakagami; Nakagami-q distribution; Random matrices, Distribution functions; Eigenvalues and eigenfunctions; Fading channels; Probability density function; Receiving antennas, Channel capacity}, funding_details={Council of Scientific and Industrial Research, IndiaCouncil of Scientific and Industrial Research, India, CSIR}, funding_text_1={Manuscript received August 03, 2009; revised December 08, 2009. Current version published April 21, 2010. S. Kumar was supported by CSIR India through a fellowship. The authors are with the School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India (e-mail: skumar.physics@gmail.com; ap0700@mail.jnu.ac.in). Communicated by A. L. Moustakas, Associate Editor for Communications. Digital Object Identifier 10.1109/TIT.2010.2044060}, references={Simon, M.K., Alouini, M.-S., (2000) Digital Communication Over Fading Channels: A Unified Approach to Performance Analysis, , Hoboken, NJ: Wiley; Simon, M.K., Alouini, M.-S., A unified approach to the performance analysis of digital communication over generalized fading channels (1998) Proc. IEEE, 86 (9), pp. 1860-1877. , Sep; Foschini, G.J., Gans, M.J., On limits of wireless communications in a fading environment when using multiple antennas (1998) Wireless Pers. Commun., 6 (2), pp. 311-335. , Mar; Telatar, I.E., Capacity of multi-antenna Gaussian channels (1999) Eur. Trans. Telecommun., 10 (6), pp. 585-596. , Nov; Wang, Z., Giannakis, G.B., Outage mutual information of spacetime MIMO channels (2004) IEEE Trans. Inf. Theory, 50 (4), pp. 657-662. , Apr; Verdú, S., Shamai, S., Spectral efficiency of CDMA with random spreading (1999) IEEE Trans. Inf. Theory, 45 (2-3 PT), pp. 622-640. , Mar; Rapajic, P.B., Popescu, D., Information capacity of a random signature multiple-input multiple-output channel (2000) IEEE Trans. Commun., 48 (8), pp. 1245-1248. , Aug; Shin, H., Lee, J.H., Closed form formulas for ergodic capacity of MIMO Rayleigh fading channels (2003) Proc. IEEE Int. Conf. Communications, pp. 2996-3000. , May; Cottatellucci, L., Debbah, M., On the capacity of MIMO rice channels (2004) Presented at the 42nd Annu. Allerton Conf. Communication, , Oct; Jayaweera, S.K., Poor, H.V., On the capacity of multiple-antenna systems in Rician fading (2005) IEEE Trans. Wireless Commun., 4 (3), pp. 1102-1111. , May; Kang, M., Alouini, M.-S., Capacity of MIMO Rician channels (2006) IEEE Trans. Wireless Commun., 5 (1), pp. 112-122. , Jan; Müller, R.R., A random matrix model of communication via antenna arrays (2002) IEEE Trans. Inf. Theory, 48 (9), pp. 2495-2506. , Sep; Smith, P.J., Roy, S., Shafi, M., Capacity of MIMO systems with semicorrelated flat fading (2003) IEEE Trans. Inf. Theory, 49 (10), pp. 2781-2788. , Oct; Chiani, M., Win, M.Z., Zanella, A., On the capacity of spatially correlated MIMO Rayleigh-fading channels (2003) IEEE Trans. Inf. Theory, 49 (10), pp. 2363-2371. , Oct; Simon, S.H., Moustakas, A.L., Eigenvalue density of correlated complex random Wishart matrices (2004) Phys. Rev. E, 69. , R, Jun, 065101; Simon, S.H., Moustakas, A.L., Marinelli, L., Capacity and character expansions: Moment-generating function and other exact results for MIMO correlated channels (2006) IEEE Trans. Inf. Theory, 52 (12), pp. 5336-5351. , Dec; Ghaderipoor, A., Tellambura, C., Noori, M., On the eigenvalue distribution of correlated MIMO channels by character expansion of groups (2008) Proc. IEEE Global Telecommunications Conf, pp. 1-5. , Dec; Marques, P.M., Abrantes, S.A., On the derivation of the exact, closed-form capacity formulas for receiver-sided correlated MIMO channels (2008) IEEE Trans. Inf. Theory, 54 (3), pp. 1139-1161. , Mar; Kang, M., Alouini, M.-S., Quadratic forms in complex Gaussian matrices and performance analysis of MIMO systems with co-channel interference (2004) IEEE Trans. Wireless Commun., 3 (2), pp. 418-431. , Mar; Ordôñez, L.G., Palomar, D.P., Fonollosa, J.R., Ordered eigenvalues of a general class of Hermitian random matrices and performance analysis of MIMO systems (2008) Proc. IEEE Conf. Communications, pp. 3846-3852. , May; Nakagami, M., The m-distribution-A general formula of intensity distribution of rapid fading (1960) Statistical Methods in Radio Wave Propagation, pp. 3-36. , New York: Pergamon; Müller, A., Speidel, J., Ergodic capacity and information outage probability of MIMO Nakagami-m keyhole channels with general branch parameters (2007) Proc. Wireless Communications and Networking Conf, pp. 2184-2189. , Mar; Fraidenraich, G., Lévêque, O., Cioffi, J.M., On the MIMO channel capacity for the Nakagami-m channel (2008) IEEE Trans. Inf. Theory, 54 (8), pp. 3752-3757. , Aug; Sagias, N.C., Karagiannidis, G.K., Gaussian class multivariate Weibull distributions: Theory and applications in fading channels (2005) IEEE Trans. Inf. Theory, 51 (10), pp. 3608-3619. , Oct; Hoyt, R.S., Probability functions for the modulus and angle of the normal complex variate (1947) Bell Syst. Tech. J., 26, pp. 318-359. , Apr; Fraidenraich, G., Lévêque, O., Cioffi, J.M., On the MIMO channel capacity for the dual and asymptotic cases over Hoyt channels (2007) IEEE Commun. Lett., 11 (1), pp. 31-33. , Jan; Chytil, B., The distribution of amplitude scintillation and the conversion of scintillation indices (1967) J. Atmos. Terr. Phys., 29, pp. 1175-1177. , Sep; Annamalai, A., Tellambura, C., Bhargava, V.K., Simple and accurate methods for the outage analysis in cellular mobile radio systems: A unified approach (2001) IEEE Trans. Commun., 49 (2), pp. 303-316. , Feb; Youssef, N., Wang, C.-X., Pätzold, M., A study on the second order statistics of Nakagami-Hoyt mobile fading channels (2005) IEEE Trans. Veh. Technol, 54 (7), pp. 1259-1265. , Jul; Smith, P.J., Shafi, M., On a Gaussian approximation to the capacity of wireless MIMOsystems (2002) Proc. IEEE Int. Conf. Communications, 1, pp. 406-410; Ge, H., Wong, K.D., Barton, M., Liberti, J.C., Statistical characterization of MIMO channel capacity (2002) Proc. IEEE Wireless Communications and Networking Conf, 2, pp. 789-793. , Mar; Kamath, M.A., Hughes, B.L., Yu, X., Gaussian approximations for the capacity of MIMO Rayleigh fading channels (2002) Proc. 36th Asilomar Conf. Signals, Systems and Computers, 1, pp. 614-618. , Nov; Zhao, Y., Zhao, M., Xiao, L., Wang, J., Analytical expression for the MIMO channel capacity (2006) Tsinghua Sci. Technol., 11 (3), pp. 271-277. , Jun; Chizhik, D., Foschini, G., Gans, M., Valenzela, R., Keyholes, correlations, and capacities of multielement transmit and receive antennas (2002) IEEE Trans. Wireless Commun., 1 (2), pp. 361-368. , Apr; Shin, H., Lee, J.H., Capacity of multiple-antenna fading channels: Spatial fading correlation, double scattering, and keyholes (2003) IEEE Trans. Inf. Theory, 49 (10), pp. 2636-2647. , Oct; Wishart, J.B., (1928), 20 A, pp. 32-52; Wilks, S.M., (1963) Mathematical Statistics, , Hoboken, NJ: Wiley; Edelman, A., (1989) Eigenvalues and Condition Numbers of Random Matrices, , Ph. D. dissertation, Dept. Math., Massachusetts Inst. Technol., Cambridge, MA; Mehta, M.L., (2004) Random Matrices, , New York: Academic; Pandey, A., Ghosh, S., Skew-orthogonal polynomials and universality of energy-level correlations (2001) Phys. Rev. Lett., 87 (2), p. 02410214. , Jun; Ghosh, S., Pandey, A., Skew-orthogonal polynomials and randommatrix ensembles (2002) Phys. Rev. E, 65 (1-21), p. 046221. , Apr; Dyson, F.J., Distribution of eigenvalues for a class of real symmetric matrices (1971) Rev. Mex. Fis., 20, pp. 231-237; Brody, T.A., Flores, J., French, J.B., Mello, P.A., Pandey, A., Wong, S.S.M., Random-matrix physics: Spectrum and strength fluctuations (1981) Rev. Mod. Phys., 53 (3), pp. 385-479; Kumar, S., Pandey, A., Universal spectral correlations in orthogonal-unitary and symplectic-unitary crossover ensembles of random matrices (2009) Phys. Rev. E, 79, p. 02621114. , Feb; Kumar, S., Pandey, A., Jacobi crossover ensembles of random matrices and statistics of transmission eigenvalues (2010) J. Math. Phys. A: Math. Theor., 43 (1-22), p. 085001. , Feb; Pandey, A., Brownian motion model of discrete spectra (1995) Chaos, Solitons, Fractals, 5 (7), pp. 1275-1285. , Jul; Marčenko, V.A., Pastur, L.A., Distribution of eigenvalues for some set of random matrices (1967) Math. USSR-Sbornik, 1, pp. 457-483; Bai, Z.D., Methodologies in spectral analysis of large dimensional random matrices (1999) Statist. Sinica, 9, pp. 611-677; Risken, H., (1989) The Fokker-Planck Equation: Methods of Solutions and Applications, , 2nd ed. New York: Springer-Verlag; Szego, G., (1975) Orthogonal Polynomials, , Providence, RI: AMS; Widom, H., On the relation between orthogonal, symplectic and unitary matrix ensembles (1999) J. Statist. Phys., 94 (3-4), pp. 347-363. , Feb}, correspondence_address1={Kumar, S.; School of Physical Sciences, , New Delhi 110067, India; email: skumar.physics@gmail.com}, issn={00189448}, coden={IETTA}, language={English}, abbrev_source_title={IEEE Trans. Inf. Theory}, document_type={Article}, source={Scopus},

IEEE Transactions on Information Theory

Random matrix model for nakagamihoyt fading

Flash lamp annealing induced rapid melting of a near surface Ge enriched Si wafer and the subsequent formation of SiGe layers were demonstrated. The formation of an undesirable facetted liquid/solid interface, well known for pulse melting in the millisecond time regime, was found to decrease significantly due to the increasing melting temperature of Si with reducing Ge concentration at the SiGe/Si interface. A dislocation network and the existence of strain, which were evidenced by transmission electron microscopy and μ-Raman measurements, respectively, are expected to play an important role to form thin SiGe layers. © 2010 Elsevier B.V. All rights reserved.

Current Applied Physics

Subsecond melt processing for achieving SiGe layers

We report on effects of Fe implantation dopinginduced changes in structural, optical, morphological, and vibrational properties of cadmium sulfide thin films. Films were implanted with 90 keV Fe+ ions at room temperature for a wide range of fluences from 0.1 × 1016 to 3.6 × 1016 ions cm-2 (corresponding to 0.38-12.03 at.% of Fe). Glancing angle X-ray diffraction analysis revealed that the implanted Fe atoms tend to supersaturate by occupying the substitutional cationic sites rather than forming metallic clusters or secondary phase precipitates. In addition, Fe doping does not lead to any structural phase transformation although it induces structural disorder and lattice contraction. Optical absorption studies show a reduction in the optical band gap from 2.39 to 2.17 eV with increasing Fe concentration. This is attributed to disorder-induced band tailing in semiconductors and ion-beam-induced grain growth. The strain associated with a lattice contraction is deduced from micro-Raman scattering measurements and is found that size and shape fluctuations of grains, at higher fluences, give rise to inhomogeneity in strain. © Springer-Verlag 2010.

Applied Physics A: Materials Science and Processing

Effect of Fe-ion implantation doping on structural and optical properties of CdS thin films

The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er 3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC- Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature. © 2010 American Institute of Physics.

Journal of Applied Physics

Comparison of the room temperature 1.53 μm Er photoluminescence from flash lamp and furnace annealed Er-doped Ge-rich SiO2 layers

Charge transport in copper phthalocyanine (CuPc), partially fluorinated CuPc(F4CuPc), and fluorinated CuPc(F16CuPc) based organic thin film transistors is studied using dual SiO2/ polymethylmethacrylate gate dielectrics. We demonstrate the strong influence of air/moisture induced electron traps on electron transport when the lowest unoccupied molecular orbital is close to the vacuum irrespective of hydroxyl-free dielectrics used in the devices. © 2010 American Institute of Physics.