Characteristics of nanoclay and calcined nanoclay-cement nanocomposites

The influence of nanoclay (NC) and calcined nanoclay (CNC) on the mechanical and thermal properties of cement nano-composites presented. Calcined nanoclay is prepared by heating nanoclay (Cloisite 30B) at 900 °C for 2 h. Characterisation of microstructure is investigated using Quantitative X-ray Diffraction Analysis (QXDA) and High Resolution Transmission Electron Microscopy (HRTEM). Estimation of Ca(OH)<inf>2</inf> content in the cement nanocomposite is studied by the combination of QXDA and thermogravimetry analysis (TGA) techniques. Results showed that the mechanical and thermal properties of the cement nanocomposites are improved as a result of NC and CNC addition. An optimum replacement of ordinary Portland cement with 1 wt% CNC is observed through reduced porosity and water absorption as well as increased density, compressive strength, flexural strength, fracture toughness, impact strength, hardness and thermal stability of cement nanocomposites. The microstructural analyses from QXRA and SEM indicate that the CNC acted not only as a filler to improve the microstructure, but also as the activator to support the pozzolanic reaction. Cost-benefit analysis indicates that nanoparticles are expensive but from economic point of view nanoclay is used in very small amount (i.e. 1 wt. %) in cementitious materials. As a result nanoclay does not add any significant cost but improves the mechanical properties significantly

Modeling Infiltration Kinetics Of Liquids Into Porous Alumina Preforms

MODELING INFILTRATION KINETICS OF LIQUIDS INTO POROUS ALUMINA PREFORMS. Alpha-alumina preform was infiltrated with different infiltrant and pressure for studying the infiltration kinetic. Effects of pre-sintering temperature, type of infiltrant, pressure and multiple infiltrations on the rate of infiltration into porous alumina preforms were described. The pore radius of alumina preform is calculated based on the preform water system by using Washburn model. The pore radius from this model, r of 0.0147 μm is good agreement to the average pore radius found by using mercury porosity measurement, r of 0.0170 μm. The pore radius of 0.0147 μm is used to calculate the rate of infiltration, k. The k factors are 64.83 x 10-5 ms½ and 27.11 x 10-5 ms½ for water and TiCl3 respectively without involving pressure in the calculation. On the other hand, by using pressure, the k factors are 75.14 x 10-5 ms½ and 31.40 x 10-5 ms½ for water and TiCl3 respectively. Other formulas were also included as comparisons. The kinetic of water and titanium trichloride alumina preform system is parabolic in time or linier in square root of time

High temperature diffraction study of in-situ crystallization of nanostructured TiO2 photocatalysts

The in-situ crystallization of anatase and rutile on chemically-treated Ti-foils in the temperature range 20-900ºC has been investigated using synchrotron radiation diffraction and x-ray diffraction. The processing methodology has a profound influence on the morphology, crystallite size and growth rate of nanostructured TiO2. The anatase formed was metastable and transformed to rutile at ~800ºC. Increasing the temperature from 400 to 900ºC caused the sharpening of anatase (101) peaks and resulted in a concomitant coarsening in crystallite size. The surface of annealed samples exhibited TiO2 nanorods, nanowires or nanotubes depending on the processing method. Ion-beam analysis has indicated the existence of composition gradation within the annealed TiO2 samples at the near-surface

A comparative study of x-ray shielding capability in ion-implanted acrylic and glass

Samples of acrylic and glass were implanted with tungsten (W) and lead (Pb) to investigate their X-ray attenuation characteristics. The near-surface composition depth profiles of ion-implanted acrylic and glass samples were studied using ion-beam analysis (Rutherford backscattering spectroscopy—RBS). The effect of implanted ions on the X-ray attenuation ability was studied using a conventional laboratory X-ray machine with X-ray tube voltages ranging from 40 to 100 kV at constant exposure 10 mAs. The results were compared with previous work on ion-implanted epoxy. As predicted, the RBS results and X-ray attenuation for both ion-implanted acrylic and glass increase with the type of implanted ions when compared to the controls. However, since the glass is denser than epoxy or acrylic, it has provided the higher X-ray attenuation property and higher RBS ion concentration implanted with a shorter range of the ion depth profile when compared to epoxy and acrylic. A prolonged time is necessary for implanting acrylic with a very high nominal dose to minimize a high possibility of acrylic to melt during the process

In situ neutron diffraction study on the effect of aluminium fluoride on phase transformation of mullite from alumina/clay

The effect of aluminium fluoride (AIF3) on the phase transformation sequence of mullite (3AI2032Si02) from two different types of kaolin (kaolinite and halloysite) (AI2Si20s(OH)4-2H20) within an alumina (A1203) matrix for a temperature range of 20 - 1500 C was investigated using in situ neutron diffraction. Samples containing a mixture of A1F3 (0 - 5 wt%), AI203 and kaolin were heated up to 1500 C and then furnace cooled. During the heating procedure, one hour neutron diffraction scans were conducted at 600, 900, 1100, 1200, 1300 and 1400 C, followed by six consecutive one hour scans at 1500 C and finally a one hour scan at room temperature upon cooling. The diffraction patterns collected between 1100 and 1500 C were analyzed by Rietveld analysis. The observed phase transformations exhibited a typical sequence found inclay/alumina ceramics. Corundum, mullite and cristobalite were observed. A common feature among the specimens containing different amounts of AIF3 and kaolin was that the content of corundum decreased as the amount of mullite increased, whilst the cristobalite content tended to peak near the temperature where the amounts of corundum and mullite were approximately equal. The mullitization temperature was reduced as the AIF3 content increased for both kaolinite and halloysite. The presence of AIF3 appeared to reduce the onset temperature for mullite nucleation, which is at a much lower temperature compared to that of grain growth. However, AIF3 also seemed to lower densification. Likewise mechanical properties of the resulting specimens were determined

Characteristics of x-ray attenuation in electrospun bismuth oxide/polylactic acid nanofibre mats

The characteristics of the X-ray attenuation in electrospun nano(n)- and micro(m)-Bi2O3/polylactic acid (PLA) nanofibre mats with different Bi2O3 loadings were compared as a function of energy using mammography (i.e. tube voltages of 22–49 kV) and X-ray absorption spectroscopy (XAS) (7–20 keV). Results indicate that X-ray attenuation by electrospun n-Bi2O3/PLA nanofibre mats is distinctly higher than that of m-Bi2O3/PLA nanofibre mats at all energies investigated. In addition, with increasing filler loading (n-Bi2O3 or m-Bi2O3), the porosity of the nanofibre mats decreased, thus increasing the X-ray attenuation, except for the sample containing 38 wt% Bi2O3 (the highest loading in the present study). The latter showed higher porosity, with some beads formed, thus resulting in a sudden decrease in the X-ray attenuation

Using fahp-vikor for operation selection in the flexible job-shop scheduling problem: A case study in textile industry

Scheduling of Flexible Job Shop Systems is a combinatorial problem which has been addressed by several heuristics and meta-heuristics. Nevertheless, the operation selection rules of both methods are limited to an ordered variant wherein priority-dispatching rules are not simultaneously deemed in the reported literature. Therefore, this paper presents the application of dispatching algorithm with operation selection based on Fuzzy Analytic Hierarchy Process (FAHP) and VIKOR methods while considering setup times and transfer batches. Dispatching, FAHP, and VIKOR algorithms are first defined. Second, a multi-criteria decision-making model is designed for operation prioritization. Then, FAHP is applied to calculate the criteria weights and overcome the uncertainty of human judgments. Afterwards, VIKOR is used to select the operation with the highest priority. A case study in the textile industry is shown to validate this approach. The results evidenced, compared to the company solution, a reduction of 61.05% in average delay

Recruitment and retention of women in a large randomized control trial to reduce repeat preterm births: the Philadelphia Collaborative Preterm Prevention Project

<p>Abstract</p> <p>Background</p> <p>Recruitment and retention of patients for randomized control trial (RCT) studies can provide formidable challenges, particularly with minority and underserved populations. Data are reported for the Philadelphia Collaborative Preterm Prevention Project (PCPPP), a large RCT targeting risk factors for repeat preterm births among women who previously delivered premature (< 35 weeks gestation) infants.</p> <p>Methods</p> <p>Design of the PCPPP incorporated strategies to maximize recruitment and retention. These included an advanced database system tracking follow-up status and assessment completion rates; cultural sensitivity training for staff; communication to the community and eligible women of the benefits of participation; financial incentives; assistance with transportation and supervised childcare services; and reminder calls for convenient, flexibly scheduled appointments. Analyses reported here: 1) compare recruitment projections to actual enrollment 2) explore recruitment bias; 3) validate the randomization process 4) document the extent to which contact was maintained and complete assessments achieved 5) determine if follow-up was conditioned upon socio-economic status, race/ethnicity, or other factors.</p> <p>Results</p> <p>Of eligible women approached, 1,126 (77.7%) agreed to participate fully. Of the 324 not agreeing, 118 (36.4%) completed a short survey. Consenting women were disproportionately from minority and low SES backgrounds: 71.5% consenting were African American, versus 38.8% not consenting. Consenting women were also more likely to report homelessness during their lifetime (14.6% vs. 0.87%) and to be unmarried at the time of delivery (81.6% versus 47.9%). First one-month postpartum assessment was completed for 83.5% (n = 472) of the intervention group (n = 565) and 76% (426) of the control group. Higher assessment completion rates were observed for the intervention group throughout the follow-up. Second, third, fourth and fifth postpartum assessments were 67.6% vs. 57.5%, 60.0% vs. 48.9%, 54.2% vs. 46.3% and 47.3% vs. 40.8%, for the intervention and control group women, respectively. There were no differences in follow-up rates according to race/ethnicity, SES or other factors. Greater retention of the intervention group may reflect the highly-valued nature of the medical and behavior services constituting the intervention arms of the Project.</p> <p>Conclusion</p> <p>Findings challenge beliefs that low income and minority women are averse to enrolling and continuing in clinical trials or community studies.</p

Transcriptional Regulator PerA Influences Biofilm-Associated, Platelet Binding, and Metabolic Gene Expression in Enterococcus faecalis

Enterococcus faecalis is an opportunistic pathogen and a leading cause of nosocomial infections, traits facilitated by the ability to quickly acquire and transfer virulence determinants. A 150 kb pathogenicity island (PAI) comprised of genes contributing to virulence is found in many enterococcal isolates and is known to undergo horizontal transfer. We have shown that the PAI-encoded transcriptional regulator PerA contributes to pathogenicity in the mouse peritonitis infection model. In this study, we used whole-genome microarrays to determine the PerA regulon. The PerA regulon is extensive, as transcriptional analysis showed 151 differentially regulated genes. Our findings reveal that PerA coordinately regulates genes important for metabolism, amino acid degradation, and pathogenicity. Further transcriptional analysis revealed that PerA is influenced by bicarbonate. Additionally, PerA influences the ability of E. faecalis to bind to human platelets. Our results suggest that PerA is a global transcriptional regulator that coordinately regulates genes responsible for enterococcal pathogenicity

The Transcriptome of the Nosocomial Pathogen Enterococcus faecalis V583 Reveals Adaptive Responses to Growth in Blood

gains access to the bloodstream and establishes a persistent infection is not well understood.. infections