Study of the mechanism of nanocrystalline Pb(Zr0.52Ti0.48)O-3 prepared by accelerated sol-gel process

Nanocrystalline Pb(Zr0.52Ti0.48)O-3 was prepared from lead acetate, zirconium oxynitrate and titanium tetra-n-butoxide by a sol-gel method. It is found that both the crystallization temperature of precursor PZT and PZT product size were increased with increase of V(C3H8O2)/V(H2O) ratio in solution used. At V(C3H8O2)/V(H2O) = 4.47 the gel was formed moderately quick, and the nanocrystalline PZT with uniform granularity and low crystallizing temperature could be obtained. The diameter of the final nanocrystalline was ranged 60similar to70 nm as measured by atomic force microscopy (AFM). The crystallizing temperature of the precursor PZT was 443degreesC and the crystallization reaction was completed at 500degreesC by DTA and TG. The sol-gel reaction process was monitored by FT-IR and XRD.

Three Cuts for Accelerated Interval Propagation

This paper addresses the problem of nonlinear multivariate root finding. In an earlier paper we described a system called Newton which finds roots of systems of nonlinear equations using refinements of interval methods. The refinements are inspired by AI constraint propagation techniques. Newton is competative with continuation methods on most benchmarks and can handle a variety of cases that are infeasible for continuation methods. This paper presents three "cuts" which we believe capture the essential theoretical ideas behind the success of Newton. This paper describes the cuts in a concise and abstract manner which, we believe, makes the theoretical content of our work more apparent. Any implementation will need to adopt some heuristic control mechanism. Heuristic control of the cuts is only briefly discussed here.

An Accelerated Chow and Liu Algorithm: Fitting Tree Distributions to High Dimensional Sparse Data

Chow and Liu introduced an algorithm for fitting a multivariate distribution with a tree (i.e. a density model that assumes that there are only pairwise dependencies between variables) and that the graph of these dependencies is a spanning tree. The original algorithm is quadratic in the dimesion of the domain, and linear in the number of data points that define the target distribution $P$. This paper shows that for sparse, discrete data, fitting a tree distribution can be done in time and memory that is jointly subquadratic in the number of variables and the size of the data set. The new algorithm, called the acCL algorithm, takes advantage of the sparsity of the data to accelerate the computation of pairwise marginals and the sorting of the resulting mutual informations, achieving speed ups of up to 2-3 orders of magnitude in the experiments.

Accelerated partial irradiation for breast cancer: Systematic review and meta-analysis of 8653 women in eight randomized trials

Background and purpose: Accelerated partial breast irradiation (APBI) is the strategy that allows adjuvant treatment delivery in a shorter period of time in smaller volumes. This study was undertaken to assess the effectiveness and outcomes of APBI in breast cancer compared with whole-breast irradiation (WBI). Material and methods: Systematic review and meta-analysis of randomized controlled trials of WBI versus APBI. Two authors independently selected and assessed the studies regarding eligibility criteria. Results: Eight studies were selected. A total of 8653 patients were randomly assigned for WBI versus APBI. Six studies reported local recurrence outcomes. Two studies were matched in 5 years and only one study for different time of follow-up. Meta-analysis of two trials assessing 1407 participants showed significant difference in the WBI versus APBI group regarding the 5-year local recurrence rate (HR = 4.54, 95% CI: 1.78-11.61, p = 0.002). Significant difference in favor of WBI for different follow-up times was also found. No differences in nodal recurrence, systemic recurrence, overall survival and mortality rates were observed. Conclusions: APBI is associated with higher local recurrence compared to WBI without compromising other clinical outcomes. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

Application of accelerated carbonation with a combination of Na2CO3 and CO2 in cement-based solidification/stabilization of heavy metal-bearing sediment

The efficient remediation of heavy metal-bearing sediment has been one of top priorities of ecosystem protection. Cement-based solidification/stabilization (s/s) is an option for reducing the mobility of heavy metals in the sediment and the subsequent hazard for human beings and animals. This work uses sodium carbonate as an internal carbon source of accelerated carbonation and gaseous CO2 as an external carbon source to overcome deleterious effects of heavy metals on strength development and improve the effectiveness of s/s of heavy metal-bearing sediment. In addition to the compressive strength and porosity measurements, leaching tests followed the Chinese solid waste extraction procedure for leaching toxicity - sulfuric acid and nitric acid method (HJ/T299-2007), German leaching procedure (DIN38414-S4) and US toxicity characteristic leaching procedures (TCLP) have been conducted. The experimental results indicated that the solidified sediment by accelerated carbonation was capable of reaching all performance criteria for the disposal at a Portland cement dosage of 10 wt.% and a solid/water ratio of 1: 1. The concentrations of mercury and other heavy metals in the leachates were below 0.10 mg/L and 5 mg/L, respectively, complying with Chinese regulatory level (GB5085-2007). Compared to the hydration, accelerated carbonation improved the compressive strength of the solidified sediment by more than 100% and reduced leaching concentrations of heavy metals significantly. It is considered that accelerated carbonation technology with a combination of Na2CO3 and CO2 may practically apply to cement-based s/s of heavy metal-bearing sediment. (C) 2008 Elsevier B.V. All rights reserved.

Accelerated carbonation treatment of industrial wastes

The disposal of industrial waste presents major logistical, financial and environmental issues. Technologies that can reduce the hazardous properties of wastes are urgently required. In the present work, a number of industrial wastes arising from the cement, metallurgical, paper, waste disposal and energy industries were treated with accelerated carbonation. In this process carbonation was effected by exposing the waste to pure carbon dioxide gas. The paper and cement wastes chemically combined with up to 25% by weight of gas. The reactivity of the wastes to carbon dioxide was controlled by their constituent minerals, and not by their elemental composition, as previously postulated. Similarly, microstructural alteration upon carbonation was primarily influenced by mineralogy. Many of the thermal wastes tested were classified as hazardous, based upon regulated metal content and pH. Treatment by accelerated carbonation reduced the leaching of certain metals, aiding the disposal of many as stable non-reactive wastes. Significant volumes of carbon dioxide were sequestrated into the accelerated carbonated treated wastes.

Comparison of properties of traditional and accelerated carbonated solidified/stabilized contaminated soils

The investigation of the long-term performance of solidified/stabilized (S/S) contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties (e.g., degree of carbonation (DOC), pH, electrical conductivity (EC)) and physical properties (e.g., moisture content (MC), liquid limit (LL), plastic limit (PL), plasticity index (PI)) of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology (ACT), and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e.g., treatment with ordinary portland cement (OPC) or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order: the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.

Current status and perspectives of accelerated carbonation processes on municipal waste combustion residues

The increasing volumes of municipal solid waste produced worldwide are encouraging the development of processes to reduce the environmental impact of this waste stream. Combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash, and fly ash/APC residues. The disposal or reuse of these residues is however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation has been shown to have a potential for improving the chemical stability and leaching behaviour of both bottom ash and fly ash/APC residues. However, the efficacy of carbonation depends on whether the method of gas application is direct or indirect. Also important are the mineralogy, chemistry and physical properties of the fresh ash, the carbonation reaction conditions such as temperature, contact time, CO2 partial pressure and relative humidity. This paper reviews the main issues pertaining to the application of accelerated carbonation to municipal waste combustion residues to elucidate the potential benefits on the stabilization of such residues and for reducing CO2 emissions. In particular, the modification of ash properties that occur upon carbonation and the CO2 sequestration potential possible under different conditions are discussed. Although accelerated carbonation is a developing technology, it could be introduced in new incinerator facilities as a "finishing step" for both ash treatment and reduction of CO2 emissions.

Degradation of poly-L-lactide. Part2 : increased temperature accelerated degradation

Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioresorbable. The degradation of PLLA proceeds through hydrolysis of the ester linkages in the polymer's backbone; however, the time for the complete resorption of orthopaedic devices manufactured from PLLA is known to be in excess of five years in a normal physiological environment. To evaluate the degradation of PLLA in an accelerated time period, PLLA pellets were processed by compression moulding into tensile test specimens, prior to being sterilized by ethylene oxide gas (EtO) and degraded in a phosphate-buffered solution (PBS) at both 50°C and 70°C. On retrieval, at predetermined time intervals, procedures were used to evaluate the material's molecular weight, crystallinity, mechanical strength, and thermal properties. The results from this study suggest that at both 50°C and 70°C, degradation proceeds by a very similar mechanism to that observed at 37°C in vitro and in vivo. The degradation models developed also confirmed the dependence of mass loss, melting temperature, and glass transition temperature (Tg) on the polymer's molecular weight throughout degradation. Although increased temperature appears to be a suitable method for accelerating the degradation of PLLA, relative to its physiological degradation rate, concerns still remain over the validity of testing above the polymer's Tg and the significance of autocatalysis at increased temperatures.