Fatigue and retention properties of Bi3.25La0.75Ti3O12 films using LaNiO3 bottom electrodes

Fatigue-free Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films were grown on LaNiO₃ bottom electrodes grown in a microwave furnace at 700 °C for 10 min from the polymeric precursor method. It was found that LaNiO₃ (LNO) bottom electrode with pseudocubic structure strongly promote the formation of (00l) texture of BLT films. The remanent polarization (P_r) and the drive voltage (V_c) were 11 μC/cm² and 1.3 V respectively, and are better than the values found in the literature. The polarization of the Au/BLT/LNO/SiO₂/Si (100) capacitors with a thickness of 280 nm exhibited no degradation after 1 × 10¹⁰ switching cycles at an applied voltage of 5 V with a frequency of 1 MHz. After several tests the capacitors retain 77% of its polarization upon a retention time of 10⁴ s.     

Modification of porous copolymers network based on acrylonitrile

Summary The preparation of a chelating ion-exchange network based on acrylonitrile was carried out by chemical modification with hydroxylamine. The beads of resin were synthesized by aqueous suspension copolymerization of acrylonitrile (AN), styrene (STY) and divinylbenzene (DVB). The influence of diluent used in the suspension polymerization on the structure of the resulting copolymers was evaluated. The diluents employed were heptane (HEP), toluene (TOL) and anisole (ANI). It was found that the AN incorporation into copolymer structure was dependent on the diluent used. Conversion of nitrile groups into the amidoxime was conducted by treatment with hydroxylamine under alkaline solution. The resins were characterized by apparent density, surface area, average pore diameter, elemental analysis (CHN), FTIR and optical microscopy. Based on the results obtained, it was possible to control the porosity by diluent employed in the synthesis and to modify chemically a resin containing nitrile groups by hydroxylamine reaction. Received: 6 October 2001/Revised version: 2 April 2002/ Accepted: 11 April 2002     

Spatial data warehouses and spatial OLAP come towards the cloud: design and performance

Cloud computing systems handle large volumes of data by using almost unlimited computational resources, while spatial data warehouses (SDWs) are multidimensional databases that store huge volumes of both spatial data and conventional data. Cloud computing environments have been considered adequate to host voluminous databases, process analytical workloads and deliver database as a service, while spatial online analytical processing (spatial OLAP) queries issued over SDWs are intrinsically analytical. However, hosting a SDW in the cloud and processing spatial OLAP queries over such database impose novel obstacles. In this article, we introduce novel concepts as cloud SDW and spatial OLAP as a service, and afterwards detail the design of novel schemas for cloud SDW and spatial OLAP query processing over cloud SDW. Furthermore, we evaluate the performance to process spatial OLAP queries in cloud SDWs using our own query processor aided by a cloud spatial index. Moreover, we describe the cloud spatial bitmap index to improve the performance to process spatial OLAP queries in cloud SDWs, and assess it through an experimental evaluation. Results derived from our experiments revealed that such index was capable to reduce the query response time from 58.20 up to 98.89 %.     

Structure-Induced Stability in Sinuous Black Silicon for Enhanced Hydrogen Evolution Reaction Performance

Clean energy infrastructures of the future depend on efficient, low-cost, long-lasting systems for the conversion and storage of solar energy. This is currently limited by the durability and economic viability of today's solar energy systems. These limitations arise from a variety of technical challenges; primarily, a need remains for the development of stable solar absorber–catalyst interfaces and improved understanding of their mechanisms. Although thin film oxides formed via atomic layer deposition have been widely employed between the solar absorber–catalyst interfaces to improve the stability of photoelectrochemical devices, few stabilization strategies have focused on improving the intrinsic durability of the semiconductor. Here, a sinuous black silicon photocathode (s-bSi) with intrinsically improved stability owing to the twisted nanostructure is demonstrated. Unlike columnar black silicon with rapidly decaying photocurrent density, s-bSi shows profound stability in strong acid, neutral, and harsh alkaline conditions during a 24-h electrolysis. Furthermore, scanning transmission electron microscopy studies prior to and post electrolysis demonstrate limited silicon oxide growth inside the walls of s-bSi. To the authors’ knowledge, this is the first time structure-induced stability has been reported for enhancing the stability of a photoelectrode/catalyst interface for solar energy conversion.     

Palatal mucoepidermoid carcinoma in a child

OBJECTIVE: To examine whether the pharmacokinetics of quinaprilat, an active metabolite, change during repeated treatment with quinapril, an ACE inhibitor, in elderly subjects. METHODS: Quinapril (10 mg) was given once daily for 8 days in eight elderly hypertensive subjects (76 years old). Blood samples were obtained for a 24-h period after the first and eighth doses. RESULTS: Plasma concentrations of quinaprilat after the eighth dose significantly higher than those after the first dose. The maximum plasma concentration (Cmax) tended to be greater, and the area under the plasma concentration-time curve (AUC) was significantly greater after the eighth dose. CONCLUSIONS: The study showed an increase in quinaprilat concentrations and subsequent increase in AUC, during repeated treatment with quinapril in elderly subjects. However, the differences observed were very small and of no clinical significance.     

Agglutination of Plasmodium falciparum-infected erythrocytes from east and west African isolates by human sera from distant geographic regions

Plasmodium falciparum-infected erythrocytes (PfE) were collected from acutely infected children in The Gambia and Tanzania and cultured for more than 30 hr until the parasites were mature trophozoites. Sera collected from these countries, other African countries, Asia, and South America were used in the PfE microagglutination test to determine whether PfE from East and West Africa share surface antigens. From the patterns of agglutination reactivity, we identified extensive antigenic diversity in surface antigens, but obtained no evidence for greater differences between isolates from East or West Africa and those within one region. The majority of sera from immune adults from The Gambia, Tanzania, Sudan, Nigeria, or Ghana were pan-agglutinating, and agglutinated all PfE isolates from The Gambia and Tanzania. Some sera from immune adults of Irian Jaya also agglutinated each of the seven African isolates, while others agglutinated many but not all of the isolates, similar to sera from immune adults of Flores, Indonesia. In contrast, sera from nonimmune adults from Colombia agglutinated few of the African isolates. It was remarkable, however, that sera from nonimmune Colombians agglutinated any African isolates. Our results are consistent with the following conclusions: some PfE surface antigen(s) are very diverse; this diversity is a feature of the parasite worldwide; the repertoire of isolate-specific surface antigens, although large, includes antigens that are either identical or antigenically cross-reactive in geographically very distant parasite populations; and African adults have pan-agglutinating antibodies that may contribute to protective immunity. Such pan-agglutinating antibodies could reflect the accumulation of a large repertoire of isolate-specific antibodies. The contribution of antibody against any shared PfE surface antigen to the pan-agglutinating reactivities is unknown and awaits development of the appropriate reagents.     

Closed-form low frequency solutions for electromagnetic waves through a frequency selective surface

A simple closed-form approximate solution is given to the problem of transmission of a low-frequency electromagnetic wave through a frequency selective surface (FSS). FSS are periodic metal plates (or their complimentary apertures) sandwiched between dielectric slabs. At low frequencies, the induced currents on the metal plates may be approximated by a known function with a constant coefficient to be determined by the boundary conditions. Based on such a "one-mode" approximation, we derive a closed-form solution for the scattered field for FSS with multiple narrow rectangular slots, with a single wide rectangular aperture, and a circular aperture. When compared with the available exact solutions, we find that the one-mode approximation is valid when the periodaof the FSS is such thata/lambdais small enough that no grating lobe appears, e.g.,a < lambdafor normal incidence.     

Energy-efficient node position identification through payoff matrix and variability analysis

This paper investigates the use of punctured recursive systematic convolutional codes for turbo coding in a 2-user binary adder channel (2-BAC) in the presence of additive white Gaussian noise, aiming to achieve a higher transmission sum rate with reduced decoding complexity. The encoders for the 2-BAC are assumed to be block synchronized and to employ identical puncturing patterns. Iterative decoding combining the Bahl Cocke Jelinek Raviv algorithm and a two-user punctured trellis is employed. For each user and for a fixed puncturing pattern, random interleavers of length 256 bits or 1024 bits, respectively, are simulated and corresponding curves relating bit error rate versus signal to noise ratio are presented for performance comparison purposes. Computer simulation indicates that the loss in performance of a punctured turbo code can be negligible when longer interleavers are used for both users, similarly to the single user case.