Synthesis of pyrochlore free PMN-PT powder by partial oxalate process route

Pyrochlore phase free PMN-PT powder of morphotrophic phase boundary (MPB) composition has been prepared using the partial oxalate method. The synthesis process has been optimized by thorough characterization of the intermediate compounds such as columbite and (Mg_1/3Nb_2/3)_0.675 Ti_0.325)O₂ by XRD analysis, particle size analysis, surface area measurement and morphological studies. Lead oxalate produced by in situ precipitation in a suspension of (Mg_1/3Nb_2/3)_0.675Ti_0.325)O₂ powder expected to coat on the particle surface, which improved the homogeneity of the precursors and resulted in the formation of pure PMN-PT phase during calcination at 750 °C. The PMN-PT powder contains more than 95% submicron particle with D₅₀ 0.4 μm. The process eliminates the formation of detrimental pyrochlore phase from the PMN-PT powder.     

Electrospun polyurethane patch in combination with cedarwood and cobalt nitrate for cardiac applications

The growth in nanotechnology led to the fabrication of scaffold at a low cost with high productivity and high surface area. The present research aims to fabricate a novel cardiac scaffold utilizing polyurethane (PU) added with cedarwood (CW) and cobalt nitrate (CoNO₃) nanofibers. Morphological analysis showed that the mean fiber diameter of the PU nanofibers was reduced owing to the incorporation of CW and CoNO₃. Infrared and thermal analysis revealed the interaction of PU with CW and CoNO₃. Contact angle studies showed that the electrospun PU/CW displayed hydrophobic nature while PU/CW/CoNO₃ showed hydrophilic behavior compared to the pristine PU. The tensile strength of PU nanofibers increased with CW and CoNO₃ addition. Atomic force microscopy analysis depicted that the PU/CW was rougher while the PU/CW/CoNO₃ as smoother surfaces than the pristine PU. According to the coagulation assay data, the blood compatibility of the electrospun composites was enhanced compared to the pristine PU. In addition, PU and its composite nanofibers exhibited non-toxic to human dermal fibroblast cells and improved cell proliferation rates compared to the control plates. To conclude, the improved physicochemical and biological response of the electrospun composites would be putative for cardiac tissue engineering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48226.     

Bio-functionalized PCL nanofibrous scaffolds for nerve tissue engineering

Surface properties of scaffolds such as hydrophilicity and the presence of functional groups on the surface of scaffolds play a key role in cell adhesion, proliferation and migration. Different modification methods for hydrophilicity improvement and introduction of functional groups on the surface of scaffolds have been carried out on synthetic biodegradable polymers, for tissue engineering applications. In this study, alkaline hydrolysis of poly (ε-caprolactone) (PCL) nanofibrous scaffolds was carried out for different time periods (1 h, 4 h and 12 h) to increase the hydrophilicity of the scaffolds. The formation of reactive groups resulting from alkaline hydrolysis provides opportunities for further surface functionalization of PCL nanofibrous scaffolds. Matrigel was attached covalently on the surface of an optimized 4 h hydrolyzed PCL nanofibrous scaffolds and additionally the fabrication of blended PCL/matrigel nanofibrous scaffolds was carried out. Chemical and mechanical characterization of nanofibrous scaffolds were evaluated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle, scanning electron microscopy (SEM) and tensile measurement. In vitro cell adhesion and proliferation study was carried out after seeding nerve precursor cells (NPCs) on different scaffolds. Results of cell proliferation assay and SEM studies showed that the covalently functionalized PCL/matrigel nanofibrous scaffolds promote the proliferation and neurite outgrowth of NPCs compared to PCL and hydrolyzed PCL nanofibrous scaffolds, providing suitable substrates for nerve tissue engineering.     

Properties of DU-10 wt% Mo alloys subjected to various post-rolling heat treatments

Studies were completed to obtain mechanical properties of depleted uranium-molybdenum (U-Mo) alloys subjected to different post-processing treatments using microhardness, quasi-static tensile tests, and scanning electron microscopy failure analysis. U-Mo alloy foils are currently under investigation for potential fuel conversion of high power research reactors to low enriched uranium fuel. Although mechanical properties take on a secondary effect during irradiation, an understanding of the alloy behavior during fabrication and the effects of irradiation on the integrity of the fuel are essential. In general, the microhardness was insensitive to annealing temperature but decreased with annealing duration. Yield strength, Young's modulus, and ultimate tensile strength were affected in varying manners with both increasing annealing temperature and duration, and subjecting the alloy to rolling. The failure mode was insensitive to annealing conditions, but was significantly controlled by the impurity concentration of the alloy, especially carbon. Values obtained from literature are also provided with reasonable agreement based on extrapolation of annealing duration, even though processing conditions and applications were quite different in some instances.     

Effect of hydrolysed aluminium treatment on rheological characteristics of α-alumina slurries

This paper describes the process for the hydrolysed aluminium treatment (HA) on alumina surface and its influence on the rheological characteristics of alumina slurries. Three different commercial grade aluminas were provided with the surface treatment with hydrolysed aluminium using aluminium nitrate and hexamethylenetetramine (HMTA) under controlled conditions. The HA treatment increased the concentration of Al-OH surface sites resulting in higher H⁺ adsorption on the alumina surface. A highly concentrated (>55 vol%) electrostatically stabilized alumina slurry was prepared from HA treated alumina powders. The rheology of such slurry was studied and the results on the viscosity and yield stress are presented. The alumina slurries followed the Casson Model flow behaviour. The wet and flow behaviour of the alumina with and without HA treatment was also studied and the results are compared. The surface treatment showed the advantage of maintaining low viscosity and yield stress of alumina slurries even at higher solids loading (>55 vol%) that are prepared in the acidic aqueous medium. The results on viscosity and yield stress were compared with that of the polyelectrolyte dispersed system.     

Application-Layer Protocol for Collaborative Multimedia Presentations

Many multimedia presentation applications involve retrieval of objects from more than one collaborating server. Presentations of objects from different collaborating servers might be interdependent. For instance, we can consider distributed video servers where blocks of movies are distributed over a set of servers. Here, blocks of a movie from different video servers have to be retrieved and presented continuously without any gaps in the presentation. Such applications first need an estimate of the available network resources to each of the collaborating server in order to identify a schedule for retrieving the objects composing the presentation. A collaborating server can suggest modifications of the retrieval schedule depending on its load. These modifications can potentially affect the retrieval schedule for other collaborating applications. Hence, a sequence of negotiations have to be carried out with the collaborating servers in order to commit for a retrieval schedule of the objects composing the multimedia presentation. In this paper, we propose an application sub-layer protocol, Resource Lock Commit Protocol (RLCP), for handling the negotiation and commitment of the resources required for a collaborative multimedia presentation application.     

End-to-end QoS framework for heterogeneous wired-cum-wireless networks

With information access becoming more and more ubiquitous, there is a need for providing QoS support for communication that spans wired and wireless networks. For the wired side, RSVP/SBM has been widely accepted as a flow reservation scheme in IEEE 802 style LANs. Thus, it would be desirable to investigate the integration of RSVP and a flow reservation scheme in wireless LANs, as an end-to-end solution for QoS guarantee in wired-cum-wireless networks. For this purpose, we propose WRESV, a lightweight RSVP-like flow reservation and admission control scheme for IEEE 802.11 wireless LANs. Using WRESV, wired/wireless integration can be easily implemented by cross-layer interaction at the Access Point. Main components of the integration are RSVP-WRESV parameter mapping and the initiation of new reservation messages, depending on where senders/receivers are located. In addition, to support smooth roaming of mobile users among different basic service sets (BSS), we devise an efficient handoff scheme that considers both the flow rate demand and network resource availability for continuous QoS support. Furthermore, various optimizations for supporting multicast session and QoS re-negotiation are proposed for better performance improvement. Extensive simulation results show that the proposed scheme is promising in enriching the QoS support of multimedia applications in heterogeneous wired-cum-wireless networks. Ming Li received his B.S. and M.S. in Engineering from Shanghai Jiao Tong University, China, in 1995 and 1998, respectively. He is currently a Ph.D. candidate in department of Computer Science, University of Texas at Dallas, where he received M.S. degree in Computer Science in Dec. 2001. His research interest includes QoSschemes for mobile ad-hoc networks and multimedia over wireless networks. Hua Zhu received the Ph.D. degree in Electrical Engineering from the University of Texas at Dallas, Texas. Since 2005, he has been working for San Diego Research Center, Inc., San Diego, CA, as a Research Engineer. His research interests include all layers of wireless communication systems. His particular interest is in L2/3 air interface design, performance analysis, and optimization for ad hoc and sensor networks. Imrich Chlamtac is the President of CREATE-NET and the Bruno Kessler Professor at the University of Trento, Italy. He has held various honorary and chaired professorships in USA and Europe including the Distinguished Chair in Telecommunications Professorship at the University of Texas at Dallas, Sackler Professroship at Tel Aviv University and has been on faculty at Technion, and UMass. Dr. Imrich Chlamtac has made significant contribution to various networking technologies as scientist, educator and entrepreneur. Dr. Chlamtac is the recipient of multiple awards and recognitions including Fellow of the IEEE, Fellow of the ACM, Fulbright Scholar, the ACM Award for Outstanding Contributions to Research on Mobility and the IEEE Award for Outstanding Technical Contributions to Wireless Personal Communications. Dr. Chlamtac published over three hundred and fifty refereed journal, book, and conference articles and is the co-author of four books. Dr. Chlamtac has widely contributed to the scientific community as founder and Chair of ACM Sigmobile, founder and steering committee chair of some of the lead conferences in networking including Mobicom, OptiComm, Mobiquitous, Broadnets, Securecomm. Dr. Chlamtac also serves as the founding Editor in Chief of the ACM/URSI/Springer Wireless Networks (WINET), the ACM/Springer Journal on Special Topics in Mobile Networks and Applications (MONET). B. Prahbakaran is with the faculty of Computer Science Department, University of Texas at Dallas. He has been working in the area of multimedia systems: animation & multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. Dr. Prabhakaran received the prestigious National Science Foundation (NSF) CAREER Award in 2003 for his proposal on Animation Databases. He has published several research papers in various refereed conferences and journals in this area. He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

Naked-eye cadmium sensor: using chromoionophore arrays of Langmuir-Blodgett molecular assemblies

This study demonstrates the possibility of a reversible naked-eye detection method for submicromolar levels of cadmium(II) using the Langmuir-Blodgett (L-B) technique. Molecular assemblies of 4-n-dodecyl-6-(2-thiazolylazo)resorcinol are transferred on precleaned microscopic glass slides, to act as a sensing probe. Isotherm (pi-A) measurements were performed to ensure the films' structural rigidity and homogeneity during sensor fabrication. The sensor surface morphology was characterized using atomic force microscopy and scanning electron microscopy. The probe membrane exhibits visual color transition, forming a series of reddish-orange to pinkish-purple complexes with cadmium, over a wide concentration range (0.04-44.5 microM). Cadmium response kinetics and the changes in the sensors' intrinsic optical properties were monitored using absorption spectroscopy and further confirmed using X-ray photoelectron spectroscopy. A hybrid L-B film composite of poly(vinyl stearate) and poly(vinyl-N-octadecylcarbamate) were investigated for enhancing sensor performance. The sensor was tested for its practical approach to prove its cadmium selectivity and sensitivity amid common matrix constituents using synthetic mixtures and real water samples. Using the sensor strips, the respective lower limits of cadmium detection and quantification are 0.039 and 0.050 microM, as estimated from a normalized linear calibration plot.     

Structure–Property Relationship in Mn-Doped (Pb0.94Sr0.06)(Zr0.53Ti0.47)O3

Hard piezoelectrics based on PZT with a composition near the morphotropic phase boundary (Pb_0.94Sr_0.06)(Zr_0.53Ti_0.47)O₃ [PSZT] have been synthesized by the sol–gel method. The influence of B site aliovalent dopant Mn³⁺ on the crystal structure and electrical properties has been investigated. Mn³⁺ions ( d ⁴) are found to change the crystal structure from tetragonal to rhombohedral as a result of Jahn–Teller distortion of the MnO₆ octahedra and are therefore found to impart donor characteristics to PSZT.     

Measurement of wear of carbon coated sliders using atomic force microscopy and Raman spectroscopy

Wear of carbon coated sub-ambient pressure “pico” sliders is investigated during sweep testing as a function of interference height, slider design and sliding distance using atomic force microscopy. The wear results from atomic force microscopy measurements are compared with wear measurements of the carbon overcoat using Raman spectroscopy. The effect of interference on wear and disk burnishing is studied using acoustic emission measurements and atomic force microscopy. The results show that wear of a slider is higher for larger interference height and higher stiffness of the air-bearing.