Observation of a centrality-dependent dijet asymmetry in lead-lead collisions at sqrt[S(NN)] =2.76 TeV with the ATLAS detector at the LHC

By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.     

Computation of triple differential cross-sections with the inclusion of exchange effects in atomic K-shell ionization by relativistic electrons for symmetric geometry

The triple differential cross-section for K-shell ionization of silver and copper atoms by relativistic electrons have been computed in the coplanar symmetric geometry with the inclusion of exchange effects following the multiple scattering theory of Das and Seal [1] multiplied by suitable spinors. Present computed results are marginally improved in some cases from the previous computed results [2]. Present results are compared with measured values [3] and with previous computation results [2]. Some other theoretical computational results are also presented here for comparison.      

Spectrum analysis of seismic surface waves and its applications in seismic landmine detection

In geophysics, spectrum analysis of surface waves (SASW) refers to a noninvasive method for soil characterization. However, the term spectrum analysis can be used in a wider sense to mean a method for determining and identifying various modes of seismic surface waves and their properties such as velocity, polarization, etc. Surface waves travel along the free boundary of a medium and can be easily detected with a transducer placed on the free surface of the boundary. A new method based on vector processing of space-time data obtained from an array of triaxial sensors is proposed to produce high-resolution, multimodal spectra from surface waves. Then individual modes can be identified in the spectrum and reconstructed in the space-time domain; also, reflected waves can be separated easily from forward waves in the spectrum domain. This new SASW method can be used for detecting and locating landmines by analyzing the reflected waves for resonance. Processing examples are presented for numerically generated data, experimental data collected in a laboratory setting, and field data.     

The role of matching thickness on the wideband electromagnetic wave suppresser using single layer doped barium ferrite

The effect of Mg²⁺, Co²⁺and Ti⁴⁺ substitution on microwave absorption has been studied for BaMg_0.5Co_0.5Ti_1.0Fe₁₀O₁₉ ferrite-acrylic resin composite in frequency range from 13 to 20 GHz. X-ray diffraction (XRD), scanning electron microscopy (SEM), vector network analysis and vibrating sample magnetometry (VSM) were employed to analyze structure, electromagnetic and microwave absorption properties of prepared ferrite. The obtained results of reflectivity demonstrate that by varying matching thickness along with weight percentage of ferrite to acrylic resin, the bandwidth coupled with reflection loss values of prepared composites can be easily tuned. Based on microwave measurement on reflectivity, it is found that BaMg_0.5Co_0.5Ti_1.0Fe₁₀O₁₉ is a good candidate for wideband electromagnetic compatibility and other practical applications at high frequency.     

Effect of ferrofluid concentration on electrical and magnetic properties of the Fe3O4/PANI nanocomposites

Magnetic nanocomposites can be controlled and tailored to provide the desired mechanical, physical, chemical, and biomedical properties depending on the final applications. The coating of ferrite nanoparticles with polymers affords the possibility of minimizing agglomeration in large-scale commercial synthesis of nanocomposite materials. The process of coating not only provides effective encapsulation of individual nanoparticles, but also controls the growth in size, thus, yielding a better overall size distribution. In this paper, in-situ polymerization of aniline was carried out in different concentration of the ferrofluid with the aim to obtain agglomerate free nanocomposites. The role of the ferrite concentration was investigated by the spectral, morphological, conductivity, and magnetic properties of Fe₃O₄/polyaniline (PANI) nanocomposites. XRD revealed the presence of spinel phase of Fe₃O₄ and the particle size was calculated to be 14.3 nm. Spectral analysis confirmed the formation of PANI encapsulated Fe₃O₄ nanocomposite. Conductivity of the nanocomposites was found to be in the range of 0.001–0.003 S/cm. Higher saturation magnetization of 3.2 emu/g was observed at 300 K, revealing a super paramagnetic behavior of this nanocomposite.