Development of electromagnetic shielding materials from the conductive blends of polyaniline and polyaniline-clay nanocomposite-EVA: Preparation and properties

Electromagnetic interference shielding composite materials were developed from the conductive blends of nanostructured polyaniline (PANI) and polyaniline-clay nanocomposite (PANICN) with ethylene vinyl acetate (EVA) as host matrix. Electrically conducting nanostructured PANI and PANICNs were prepared using amphiphilic dopants, 3-pentadecyl phenol 4-sulphonic acid (3-PDPSA) derived from cashew nut shell liquid, a low cost renewable resource based product and dodecyl benzene sulfonic acid (DBSA). Effects of type and quantity of conductive fillers on the electrical conductivity, mechanical properties, thermal stability, morphology and electromagnetic shielding efficiency were investigated. The presence of exfoliated nanoclay and interaction between the conductive filler–host matrix in conductive films containing PANICNs manifested from the measurement on rheological property. Films with conductive filler (～15% loading) showed a shielding effectiveness of ～40–80 dB at 8 GHz which makes these conducting composites potential candidate for the encapsulation as EMI shielding materials for electronic devices.     

Residual U-Network for Breast Tumor Segmentation from Magnetic Resonance Images

Breast cancer positions as the most well-known threat and the main source of malignant growth-related morbidity and mortality throughout the world. It is apical of all new cancer incidences analyzed among females. Two features substantially influence the classification accuracy of malignancy and benignity in automated cancer diagnostics. These are the precision of tumor segmentation and appropriateness of extracted attributes required for the diagnosis. In this research, the authors have proposed a ResU-Net (Residual U-Network) model for breast tumor segmentation. The proposed methodology renders augmented, and precise identification of tumor regions and produces accurate breast tumor segmentation in contrast-enhanced MR images. Furthermore, the proposed framework also encompasses the residual network technique, which subsequently enhances the performance and displays the improved training process. Over and above, the performance of ResU-Net has experimentally been analyzed with conventional U-Net, FCN8, FCN32. Algorithm performance is evaluated in the form of dice coefficient and MIoU (Mean Intersection of Union), accuracy, loss, sensitivity, specificity, F1score. Experimental results show that ResU-Net achieved validation accuracy & dice coefficient value of 73.22% & 85.32% respectively on the Rider Breast MRI dataset and outperformed as compared to the other algorithms used in experimentation.     

Effect of Ni Doping at Pd Site in Nb<Subscript>2</Subscript>PdS<Subscript>5</Subscript> Superconductor

The superconducting properties of Nb₂PdS₅ superconductor have been investigated with Ni doping at Pd site All the bulk polycrystalline Nb₂Pd_1?xNi_x S ₅ (0 = x ≤ 0.10) samples are crystallized in singlephase monoclinic structure. The electrical resistivity and magnetic measurements of Nb₂Pd_1?xNi_x S ₅ (0 = x ≤ 0.15) were carried out to study the variation of superconducting critical parameters with Ni doping. Superconductivity in Nb₂PdS₅ sample completely disappears for x ≥ 0.15. We observed that the ratio of upper critical field to transition temperature decreases with increasing Ni concentration. Also, the magnetization study of Nb₂Pd_1?xNi_x S ₅ (0 = x ≤ 0.15) samples shows similar superconducting behaviour. In summary, the superconductivity in Nb₂PdS₅ sample is slightly varying with partial doping of Ni at Pd site in Nb₂PdS₅ superconductor.     

Influence of Processing Variables on Dynamic Mechanical Response of Laser-Sintered Glass-Filled Polyamide

For establishing selective laser sintering in manufacturing technology, a wide knowledge about the influence of processing variables on the quality of sintered part is mandatory. In this regard, this article addresses the influence of key process parameters (i.e., bed temperature, laser power, beam speed, hatch distance, hatch length) on the dynamic mechanical properties of laser-sintered glass-filled polyamide specimens to enhance their service life. A face-centered central composite design of response surface methodology was employed to gather data, and mathematical models were developed to investigate the effects and interactions of selected input processing variables on the different performance characteristics. Experiments revealed that dynamic mechanical properties reduced with decrease in bed temperature. This was due to nonuniform fusion of powder particles and increased porosity. Specimens fabricated at high energy density (ED) were strong, solid, and isotropic but become weak, porous, and anisotropic, as the ED decreased. Poor material integrity and weak interparticle bonding were the main reasons of low dynamic mechanical strength. In addition, microstructural analysis was also performed to examine the surface morphology of sintered specimens. Further, optimum working conditions for producing parts with maximum dynamic mechanical response were determined.     

Electronic and vibrational excitations in layered highT c superconductors

In the series of the layered highT _c superconductors (A)_1,2 B₂Ca _n−1Cu _n O_2n+3,4 (A=Tl or Bi;B=Ba or Sr), withn=number of consecutive Cu-O layers, the electron energy states of some of the Tl-based systems have been investigated. The electron and phonon dispersion curves have been obtained. The electronic states near the Fermi level are dominated by the hybridized Cu(d) and the O(p) orbitals. The dispersion curves are highly two-dimensional with very small dispersion alongc-axis. The number of bands is enhanced with increase in the number of the consecutive Cu-O planes (n). The present results agree with those obtained earlier for other superconducting phases. The phonons are overall dominated by the vibrations of the light mass oxygen atom modes both lying in or outside the Cu-O planes. The low-frequency phonons involve the motions of the heavier Tl, Ba atoms etc.     

Wideband circularly polarized square dielectric resonator antenna for WLAN/WiMAX applications

In the present article, a novel single fed square dielectric resonator antenna (SDRA) is presented and two orthogonal modes ( ${\mathrm{TE}}_{111}^{\mathrm{x}}\text{and}{\mathrm{TE}}_{111}^{\mathrm{y}}$) of SDRA are utilized to produce the wideband circular polarization. To generate circular polarization over a broad frequency band, a new technique known as hybrid DRA has been proposed in this article. In this technique, the feeding circuit act as a radiator and also provides feeding to the dielectric resonator which enhances the impedance and axial ratio bandwidth. A 3‐dB axial ratio bandwidth of 26.66% is achieved by the SDRA excited through a rectangular patch united with 50 Ω microstrip line. In order to further increase the axial ratio bandwidth from 26.66% to 48%, a notch is truncated from the rectangular patch. The design antenna prototype has been fabricated and experimentally tested. Experimental results illustrate that the proposed structure has broad impedance and axial ratio bandwidth of 75.86% and 43.75%, respectively, and the entire axial ratio bandwidth fully matched with the impedance bandwidth. The proposed antenna produces a right handed circularly polarized (RHCP) field. By taking the mirror image of the proposed microstrip feeding, the RHCP field is converted into left handed circularly polarized (LHCP) field. This antenna is preferred for wireless applications such as indoors communication, remote sensing, wireless sensor systems and WLAN/WiMAX applications.     

Performance testing of a linear fresnel reflector

Results of optical and thermal performance evaluation tests conducted on a prototype linear Fresnel reflector system fabricated using locally available material are presented in this paper.     

The Effect of Oxidized Dopamine on the Structure and Molecular Chaperone Function of the Small Heat-Shock Proteins, αB-Crystallin and Hsp27

Oxidation of the neurotransmitter, dopamine (DA), is a pathological hallmark of Parkinson’s disease (PD). Oxidized DA forms adducts with proteins which can alter their functionality. αB-crystallin and Hsp27 are intracellular, small heat-shock molecular chaperone proteins (sHsps) which form the first line of defense to prevent protein aggregation under conditions of cellular stress. In vitro, the effects of oxidized DA on the structure and function of αB-crystallin and Hsp27 were investigated. Oxidized DA promoted the cross-linking of αB-crystallin and Hsp27 to form well-defined dimer, trimer, tetramer, etc., species, as monitored by SDS-PAGE. Lysine residues were involved in the cross-links. The secondary structure of the sHsps was not altered significantly upon cross-linking with oxidized DA but their oligomeric size was increased. When modified with a molar equivalent of DA, sHsp chaperone functionality was largely retained in preventing both amorphous and amyloid fibrillar aggregation, including fibril formation of mutant (A53T) α-synuclein, a protein whose aggregation is associated with autosomal PD. In the main, higher levels of sHsp modification with DA led to a reduction in chaperone effectiveness. In vivo, DA is sequestered into acidic vesicles to prevent its oxidation and, intracellularly, oxidation is minimized by mM levels of the antioxidant, glutathione. In vitro, acidic pH and glutathione prevented the formation of oxidized DA-induced cross-linking of the sHsps. Oxidized DA-modified αB-crystallin and Hsp27 were not cytotoxic. In a cellular context, retention of significant chaperone functionality by mildly oxidized DA-modified sHsps would contribute to proteostasis by preventing protein aggregation (particularly of α-synuclein) that is associated with PD.     

Crosslinking reaction of epoxy resin (diglycidyl ether of bisphenol A) by anionically polymerized polycaprolactam: I. Mechanism and optimization

Different ratios of epoxy resin, diglycidyl ether of bisphenol A (DGEBA) and ?‐caprolactam (starting from 10:90 DGEBA and vice versa), were used to synthesize reactive DGEBA and polycaprolactam blends by the anionic polymerization of ?‐caprolactam at 140°C. Anionic polymerization was conducted with a strong base such as sodium hydride as a catalyst along with a cocatalyst such as N‐acetyl caprolactam. The reaction mechanism, possible cure reactions, and reaction conditions of the reactive blends were studied with Fourier transform infrared spectroscopy and differential scanning calorimetry. The experiments were carried to study the optimization ratio and the effect of the composition on properties such as hardness and tensile strength of the reactive blends. The DGEBA was crosslinked by polycaprolactam through the reaction of the oxirane group with the amide nitrogen, and the reaction was very fast. A ratio of 80:20 (DGEBA:?‐caprolactam) was optimum, and the resulting blend showed the highest tensile strength and hardness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3237–3247, 2003