Electrical Properties of Stoichiometric BiFeO3 Prepared by Mechanosynthesis with Either Conventional or Spark Plasma Sintering

Phase‐pure powders of stoichiometric BiFeO₃ have been prepared by mechanosynthesis. Ceramics sintered by either conventional heating in air or spark plasma sintering (SPS) followed by oxidative anneal in air are highly insulating at room temperature with resistivity, extrapolated from the Arrhenius plots, of ~10¹⁶ Ωcm and activation energy 1.15(2) eV, comparable with those of a good‐quality BiFeO₃ single crystal. By contrast, the as‐prepared SPS sample without the postsinter anneal shows lower resistivity, e.g., ~10¹⁰ Ωcm at 25°C and activation energy 0.67(3) eV, indicating some reduction in the sample by the SPS process. The reason for the high conductivity reported for some ceramic samples in the literature remains unclear at present.     

Rapid Assessment of Quality Parameters in Cocoa Butter Using ATR-MIR Spectroscopy and Multivariate Analysis

The development of sensitive and robust screening tool(s) for assuring the quality of incoming raw materials would supplement the assurances provided by food manufacturer vendor auditing programs. Our aim was to evaluate the ability of attenuated total reflectance mid‐infrared (ATR‐MIR) spectroscopy in combination with multivariate analysis as a screening tool for the diverse cocoa butter supply. Forty different cocoa butter samples encompassing an acceptable range of compositional variability for the chocolate industry were included. Cocoa butters were characterized for their melt characteristics (melting heat), triacylglycerol content and fatty acid composition (GC‐FAME). Soft independent modeling of class analogy (SIMCA) and partial least squares regression (PLSR) were used for classification and quantification analysis. SIMCA classified all cocoa butters in distinct clusters in a 3‐dimensional space but no sample clustering patterns were associated with melt characteristics. Spectral differences responsible for the separation of classes were attributed to stretching vibrations of the ester (–C=O) linkage (1,660–1,720 cm^?1). PLSR models showed correlation coefficients >0.93 and prediction errors (SECV) of 1.5 units for melt characteristics, 0.2–0.3 and 0.4–0.8 % for major fatty acids and triacylglycerols, respectively. ATR‐MIR spectroscopy combined with pattern recognition analysis provides robust models for characterization and determination of cocoa butter composition.     

Activity of NiCuAl catalyst in methane decomposition studied using a thermobalance and the structural changes in the Ni and the deposited carbon

Activity measurements of a NiCuAl catalyst for the thermal decomposition of methane have been carried out in a thermobalance at different operating temperatures and partial pressures of methane and hydrogen. The thermobalance allows, by gravimetry, a continuous record of the evolution of the deposited carbon during and at the end of the test and the extraction of a sufficient amount of homogenous sample to study the involved structural changes in Ni and the structural properties of the deposited carbon by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of the operating temperature, mainly derived from thermal sintering, on Ni particles and on the deposited carbon is highly significant. The effect of methane as a reactant and hydrogen as a reaction product is mostly derived from its influence on the reaction rate. Additionally, methane and hydrogen reduce the effect of thermal sintering on Ni lowering the surface energy by chemisorption. The study also shows that the deposited carbon on the Ni leading face probably diffuses to the Ni trailing face superficially, and not through bulk Ni as assumed by the present kinetic models.     

European CO2 prices and carbon capture investments

We assess the option to install a carbon capture and storage (CCS) unit in a coal-fired power plant operating in a carbon-constrained environment. We consider two sources of risk, namely the price of emission allowance and the price of the electricity output. First we analyse the performance of the EU market for CO₂ emission allowances. Specifically, we focus on the contracts maturing in the Kyoto Protocol's first commitment period (2008 to 2012) and calibrate the underlying parameters of the allowance price process. Then we refer to the Spanish wholesale electricity market and calibrate the parameters of the electricity price process.We use a two-dimensional binomial lattice to derive the optimal investment rule. In particular, we obtain the trigger allowance prices above which it is optimal to install the capture unit immediately. We further analyse the effect of changes in several variables on these critical prices, among them allowance price volatility and a hypothetical government subsidy.We conclude that, at current permit prices, immediate installation does not seem justified from a financial point of view. This need not be the case, though, if carbon market parameters change dramatically, carbon capture technology undergoes significant improvements, and/or a specific governmental policy to promote these units is adopted.     

Performance and antioxidant activity of phenol/phosphite antioxidants in synergistic blends in the thermal and photooxidation of high‐density polyethylene (HDPE) film: Influence of zinc stearate

The influence of zinc stearate (ZnSt) on the thermal and photochemical stabilities of phenolic antioxidant/phosphite combinations has been determined in HDPE by using FTIR analysis. The results show that while under thermal aging the effects are generally antagonistic, under photooxidation the effects are synergistic. The interactions appear to be dominated by the role of complex formation between the phosphites and ZnSt. Such interactions would remove the hydroperoxide effectiveness of the phosphite in thermal oxidation, while under light they could cause stabilization. Derivative UV and FTIR analysis on pre‐melt blends of the additives in solution shows evidence for strong complexation for the phosphite antioxidants. Other acid scavengers such as hydrotalcite and calcium stearate also appear to influence the behavior of phenolic antioxidants in thermal oxidation. The antagonistic effect of zinc stearate was also confirmed following a single pass in an extruder, where for all formulations there was a greater reduction in MFI associated with crosslinking.     

Atomistic modeling of the effects of dose and implant temperature on dopant diffusion and amorphization in Si

We discuss atomistic simulations of ion implantation and annealing of Si over a wide range of ion dose and substrate temperatures. The DADOS Monte Carlo model has been extended to include the formation of amorphous regions, and this allows simulations of dopant diffusion at high doses. As the dose of ions increases, the amorphous regions formed by cascades eventually overlap, and a continuous amorphous layer is formed. In that case, most of the excess interstitials generated by the implantation are swept to the surface as the amorphous layer regrows, and do not diffuse in the crystalline region. This process reduces the amount of transient enhanced diffusion (TED) during annealing. This model also reproduces the dynamic annealing during high temperature implants. In this case, the local amorphous regions regrow as the implant proceeds, without the formation of a continuous amorphous layer. For sufficiently high temperatures, each cascade is annealed out independently; interstitials and vacancies can escape from the cascade and thus increase dopant diffusion.     

The Adaptive Immune Landscape of the Colorectal Adenoma–Carcinoma Sequence

Background. The tumor immune microenvironment exerts a pivotal influence in tumor initiation and progression. The aim of this study was to analyze the immune context of sporadic and familial adenomatous polyposis (FAP) lesions along the colorectal adenoma–carcinoma sequence (ACS). Methods. We analyzed immune cell counts (CD3+, CD4+, CD8+, Foxp3+, and CD57+), tumor mutation burden (TMB), MHC-I expression and PD-L1 expression of 59 FAP and 74 sporadic colorectal lesions, encompassing adenomas with low-grade dysplasia (LGD) (30 FAP; 30 sporadic), adenomas with high-grade dysplasia (22 FAP; 30 sporadic), and invasive adenocarcinomas (7 FAP; 14 sporadic). Results. The sporadic colorectal ACS was characterized by (1) a stepwise decrease in immune cell counts, (2) an increase in TMB and MHC-I expression, and (3) a lower PD-L1 expression. In FAP lesions, we observed the same patterns, except for an increase in TMB along the ACS. FAP LGD lesions harbored lower Foxp3+ T cell counts than sporadic LGD lesions. A decrease in PD-L1 expression occurred earlier in FAP lesions compared to sporadic ones. Conclusions. The colorectal ACS is characterized by a progressive loss of adaptive immune infiltrate and by the establishment of a progressively immune cold microenvironment. These changes do not appear to be related with the loss of immunogenicity of tumor cells, or to the onset of an immunosuppressive tumor microenvironment.     

Word-based grouping affects the prime-task effect on semantic priming.

Semantic priming between words is reduced or eliminated if a low-level task such as letter search is performed on the prime word (the prime task effect), a finding used to question the automaticity of semantic processing of words. This idea is critically examined in 3 experiments with a new design that allows the search target to occur both inside and outside the prime word. The new design produces the prime task effect (Experiment 1) but shows semantic negative priming when the target letter occurs outside the prime word (Experiments 2 and 3). It is proposed that semantic activation and priming are dissociable and that inhibition and word-based grouping are responsible for reduction of semantic priming in the prime task effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control mechanisms to improve the robustness of mpeg-2 based communications over ATM networks

Audio-visual and other multimedia services are seen as an important source of traffic for ATM networks. Due to the statistical multiplexing schemes used by ATM networks, cells are exposed to delays, jitters and losses. These phenomena affect the quality of the service provided to the video-based applications. In this paper, we introduce a set of control mechanisms at different levels of the protocol architecture. These mechanisms have been particularly tailored to better support MPEG-2-based video communications applications using ATM networks as their underlying transmission mechanism. We show that the use of errorconcealment mechanisms prove more effective when supplemented by a structured set of protocol mechanisms. We study the impact of cell losses on the quality of MPEG-2 video sequences and provide an evaluation of the quality of the decoded video as perceived by the end user. Our results demonstrate the effectiveness of the proposed protocol architecture in improving the quality of service provided to the video application.     

On the testing,characterization, and evaluation of PV inverters and dynamic MPPT performance under real varying operating conditions

The increasing number of photovoltaic inverters that are coming on to the PV market stresses the need to carry out a dynamic characterization of these elements and their maximum power point tracking (MPPT) algorithms under real operating conditions. In order to make these conditions repeatable at the laboratory, PV array simulators are used. However, actual simulators, including the commercial simulators, recreate only a single or small set of PV array characteristic curves in which quite commonly theoretical calculations are included in order to simulate irradiance and temperature artificial variations. This is far from being a recreation of the real and long dynamic behavior of a PV array or generator. The testing and evaluation of the performance of PV inverters and MPPT algorithms has to be carried out when the PV system moves dynamically according to real operating conditions, including processes such as rapidly changing atmospheric conditions, partial shadows, dawn, and nightfall. This paper tries to contribute to the analysis of this problem by means of an electronic system that both measures the real evolution of the characteristic curves of PV arrays at outdoor operation and then recreates them at the laboratory to test PV inverters. This way the equipment can highlight the different performances of PV inverters and MPPT techniques when they operate under real operating conditions. As an example, two commercial inverters are tested and analyzed under the recreated behavior of a PV generator during 2 singular days that include processes of partial shading and fast irradiance variations. Copyright © 2007 John Wiley & Sons, Ltd.