Creep and fatigue behavior of a novel 2-component paste-like formulation of acrylic bone cements.

PubMed

Köster, Ulrike; Jaeger, Raimund; Bardts, Mareike; Wahnes, Christian; Büchner, Hubert; Kühn, Klaus-Dieter; Vogt, Sebastian

2013-06-01

The fatigue and creep performance of two novel acrylic bone cement formulations (one bone cement without antibiotics, one with antibiotics) was compared to the performance of clinically used bone cements (Osteopal V, Palacos R, Simplex P, SmartSet GHV, Palacos R+G and CMW1 with Gentamicin). The preparation of the novel bone cement formulations involves the mixing of two paste-like substances in a static mixer integrated into the cartridge which is used to apply the bone cement. The fatigue performance of the two novel bone cement formulations is comparable to the performance of the reference bone cements. The creep compliance of the bone cements is significantly influenced by the effects of physical ageing. The model parameters of Struik's creep law are used to compare the creep behavior of different bone cements. The novel 2-component paste-like bone cement formulations are in the group of bone cements which exhibit a higher creep resistance.

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

PubMed Central

Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

2016-01-01

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns. PMID:27023532

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate.

PubMed

Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

2016-03-25

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

Thermophysical and Mechanical Properties of Hardened Cement Paste with Microencapsulated Phase Change Materials for Energy Storage.

PubMed

Cui, Hongzhi; Liao, Wenyu; Memon, Shazim Ali; Dong, Biqin; Tang, Waiching

2014-12-16

In this research, structural-functional integrated cement-based materials were prepared by employing cement paste and a microencapsulated phase change material (MPCM) manufactured using urea-formaldehyde resin as the shell and paraffin as the core material. The encapsulation ratio of the MPCM could reach up to 91.21 wt%. Thermal energy storage cement pastes (TESCPs) incorporated with different MPCM contents (5%, 10%, 15%, 20% and 25% by weight of cement) were developed, and their thermal and mechanical properties were studied. The results showed that the total energy storage capacity of the hardened cement specimens with MPCM increased by up to 3.9-times compared with that of the control cement paste. The thermal conductivity at different temperature levels (35-36 °C, 55-56 °C and 72-74 °C) decreased with the increase of MPCM content, and the decrease was the highest when the temperature level was 55-56 °C. Moreover, the compressive strength, flexural strength and density of hardened cement paste decreased with the increase in MPCM content linearly. Among the evaluated properties, the compressive strength of TESCPs had a larger and faster degradation with the increase of MPCM content.

Influence of Carbon Nanotube Clustering on Mechanical and Electrical Properties of Cement Pastes

PubMed Central

Jang, Sung-Hwan; Kawashima, Shiho; Yin, Huiming

2016-01-01

Given the continued challenge of dispersion, for practical purposes, it is of interest to evaluate the impact of multi-walled carbon nanotubes (MWCNTs) at different states of clustering on the eventual performance properties of cement paste. This study evaluated the clustering of MWCNTs and the resultant effect on the mechanical and electrical properties when incorporated into cement paste. Cement pastes containing different concentrations of MWCNTs (up to 0.5% by mass of cement) with/without surfactant were characterized. MWCNT clustering was assessed qualitatively in an aqueous solution through visual observation, and quantitatively in cement matrices using a scanning electron microscopy technique. Additionally, the corresponding 28-day compressive strength, tensile strength, and electrical conductivity were measured. Results showed that the use of surfactant led to a downward shift in the MWCNT clustering size distribution in the matrices of MWCNT/cement paste, indicating improved dispersion of MWCNTs. The compressive strength, tensile strength, and electrical conductivity of the composites with surfactant increased with MWCNT concentration and were higher than those without surfactant at all concentrations. PMID:28773348

Reactivity of NO2 and CO2 with hardened cement paste containing activated carbon

NASA Astrophysics Data System (ADS)

Horgnies, M.; Dubois-Brugger, I.; Krou, N. J.; Batonneau-Gener, I.; Belin, T.; Mignard, S.

2015-07-01

The development of building materials to reduce the concentration of NO2 is growing interest in a world where the air quality in urban areas is affected by the car traffic. The main binder in concrete is the cement paste that is partly composed of calcium hydroxide. This alkaline hydrate composing the hardened cement paste shows a high BET surface area (close to 100 m2.g-1) and can absorb low-concentrations of NO2. However, the presence of CO2 in the atmosphere limits the de-polluting effect of reference cement paste, mainly due to carbonation of the alkaline hydrates (reaction leading to the formation of calcium carbonate). The results established in this paper demonstrate that the addition of activated carbon in the cement paste, because of its very high BET surface area (close to 800 m2.g-1) and its specific reactivity with NO2, can significantly improve and prolong the de-polluting effect in presence of CO2 and even after complete carbonation of the surface of the cement paste.

Influence of carbonation on the acid neutralization capacity of cements and cement-solidified/stabilized electroplating sludge.

PubMed

Chen, Quanyuan; Zhang, Lina; Ke, Yujuan; Hills, Colin; Kang, Yanming

2009-02-01

Portland cement (PC) and blended cements containing pulverized fuel ash (PFA) or granulated blast-furnace slag (GGBS) were used to solidify/stabilize an electroplating sludge in this work. The acid neutralization capacity (ANC) of the hydrated pastes increased in the order of PC > PC/GGBS > PC/PFA. The GGBS or PFA replacement (80 wt%) reduced the ANC of the hydrated pastes by 30-50%. The ANC of the blended cement-solidified electroplating sludge (cement/sludge 1:2) was 20-30% higher than that of the hydrated blended cement pastes. Upon carbonation, there was little difference in the ANC of the three cement pastes, but the presence of electroplating sludge (cement/sludge 1:2) increased the ANC by 20%. Blended cements were more effective binders for immobilization of Ni, Cr and Cu, compared with PC, whereas Zn was encapsulated more effectively in the latter. Accelerated carbonation improved the immobilization of Cr, Cu and Zn, but not Ni. The geochemical code PHREEQC, with the edited database from EQ3/6 and HATCHES, was used to calculate the saturation index and solubility of likely heavy metal precipitates in cement-based solidification/stabilization systems. The release of heavy metals could be related to the disruption of cement matrices and the remarkable variation of solubility of heavy metal precipitates at different pH values.

Natural Cellulose Nanofibers As Sustainable Enhancers in Construction Cement

PubMed Central

Jiao, Li; Su, Ming; Chen, Liao; Wang, Yuangang; Zhu, Hongli; Dai, Hongqi

2016-01-01

Cement is one of the mostly used construction materials due to its high durability and low cost, but it suffers from brittle fracture and facile crack initiation. This article describes the use of naturally-derived renewable cellulose nanofibers (CNFs) to reinforce cement. The effects of CNFs on the mechanical properties, degree of hydration (DOH), and microstructure of cement pastes have been studied. It is found that an addition of 0.15% by weight of CNFs leads to a 15% and 20% increase in the flexural and compressive strengths of cement paste. The enhancement in mechanical strength is attributed to high DOH and dense microstructure of cement pastes after adding CNFs. PMID:28005917

Damage identification in cement paste amended with carbon nanotubes

NASA Astrophysics Data System (ADS)

Soltangharaei, Vafa; Anay, Rafal; Assi, Lateef; Ziehl, Paul; Matta, Fabio

2018-04-01

Cement-based composites have been used as reliable materials in building and civil engineering infrastructure for many decades. Although there are several advantages, some drawbacks such as premature cracking may be problematic for sensitive applications such as those found in nuclear power plants or associated waste storage facilities. In this study, acoustic emission monitoring was employed to detect stress waves associated with damage progression during uniaxial compressive loading. Acoustic emission data resulting from loading of plain cement paste prisms and cement paste prisms amended with carbon nanotubes are compared. Unsupervised pattern recognition is employed to categorize the data. Results indicate that increased acoustic emission activity was recorded for the plain cement paste prisms when compared to prisms amended with carbon nanotubes.

Molecular architecture requirements for polymer-grafted lignin superplasticizers.

PubMed

Gupta, Chetali; Sverdlove, Madeline J; Washburn, Newell R

2015-04-07

Superplasticizers are a class of anionic polymer dispersants used to inhibit aggregation in hydraulic cement, lowering the yield stress of cement pastes to improve workability and reduce water requirements. The plant-derived biopolymer lignin is commonly used as a low-cost/low-performance plasticizer, but attempts to improve its effects on cement rheology through copolymerization with synthetic monomers have not led to significant improvements. Here we demonstrate that kraft lignin can form the basis for high-performance superplasticizers in hydraulic cement, but the molecular architecture must be based on a lignin core with a synthetic-polymer corona that can be produced via controlled radical polymerization. Using slump tests of ordinary Portland cement pastes, we show that polyacrylamide-grafted lignin prepared via reversible addition-fragmentation chain transfer polymerization can reduce the yield stress of cement paste to similar levels as a leading commercial polycarboxylate ether superplasticizer at concentrations ten-fold lower, although the lignin material produced via controlled radical polymerization does not appear to reduce the dynamic viscosity of cement paste as effectively as the polycarboxylate superplasticizer, despite having a similar affinity for the individual mineral components of ordinary Portland cement. In contrast, polyacrylamide copolymerized with a methacrylated kraft lignin via conventional free radical polymerization having a similar overall composition did not reduce the yield stress or the viscosity of cement pastes. While further work is required to elucidate the mechanism of this effect, these results indicate that controlling the architecture of polymer-grafted lignin can significantly enhance its performance as a superplasticizer for cement.

Using cement paste rheology to predict concrete mix design problems : technical report.

DOT National Transportation Integrated Search

2009-07-01

The complex interaction between cement and chemical/mineral admixtures in concrete mixture sometimes leads to : unpredictable concrete performance in the field, which is generally defined as concrete incompatibilities. Cement paste : rheology measure...

The effect of fly ash and coconut fibre ash as cement replacement materials on cement paste strength

NASA Astrophysics Data System (ADS)

Bayuaji, R.; Kurniawan, R. W.; Yasin, A. K.; Fatoni, H. AT; Lutfi, F. M. A.

2016-04-01

Concrete is the backbone material in the construction field. The main concept of the concrete material is composed of a binder and filler. Cement, concrete main binder highlighted by environmentalists as one of the industry are not environmentally friendly because of the burning of cement raw materials in the kiln requires energy up to a temperature of 1450° C and the output air waste CO2. On the other hand, the compound content of cement that can be utilized in innovation is Calcium Hydroxide (CaOH), this compound will react with pozzolan material and produces additional strength and durability of concrete, Calcium Silicate Hydrates (CSH). The objective of this research is to explore coconut fibers ash and fly ash. This material was used as cement replacement materials on cement paste. Experimental method was used in this study. SNI-03-1974-1990 is standard used to clarify the compressive strength of cement paste at the age of 7 days. The result of this study that the optimum composition of coconut fiber ash and fly ash to substitute 30% of cement with 25% and 5% for coconut fibers ash and fly ash with similar strength if to be compared normal cement paste.

Thermophysical and Mechanical Properties of Hardened Cement Paste with Microencapsulated Phase Change Materials for Energy Storage

PubMed Central

Cui, Hongzhi; Liao, Wenyu; Memon, Shazim Ali; Dong, Biqin; Tang, Waiching

2014-01-01

In this research, structural-functional integrated cement-based materials were prepared by employing cement paste and a microencapsulated phase change material (MPCM) manufactured using urea-formaldehyde resin as the shell and paraffin as the core material. The encapsulation ratio of the MPCM could reach up to 91.21 wt%. Thermal energy storage cement pastes (TESCPs) incorporated with different MPCM contents (5%, 10%, 15%, 20% and 25% by weight of cement) were developed, and their thermal and mechanical properties were studied. The results showed that the total energy storage capacity of the hardened cement specimens with MPCM increased by up to 3.9-times compared with that of the control cement paste. The thermal conductivity at different temperature levels (35–36 °C, 55–56 °C and 72–74 °C) decreased with the increase of MPCM content, and the decrease was the highest when the temperature level was 55–56 °C. Moreover, the compressive strength, flexural strength and density of hardened cement paste decreased with the increase in MPCM content linearly. Among the evaluated properties, the compressive strength of TESCPs had a larger and faster degradation with the increase of MPCM content. PMID:28788291

Effect of various superplasticizers on rheological properties of cement paste and mortars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masood, I.; Agarwal, S.K.

The effect of eight commercial superplasticizers including one developed from Cashew Nut Shell Liquid (CNSL) at CBRI on the rheological properties viz. viscosity and flow of cement paste and mortars have been investigated. The viscosity measurements have been made at various shear rates (5--100 rpm). It is found that at higher rates (100 rpm) even with the low concentration of superplasticizers (0.1), the viscosity of the cement paste is more or less the same as that obtained with 0.6 % dosages of SPs at lesser shear rates. The effect of split addition (delayed addition) of superplasticizers on viscosity of cementmore » paste and 1:3 cement sand mortar have also been studied. A decrease in viscosity due to split addition has been observed in the cement paste and there is an increase of 15--20 % in flow of mortars.« less

Influence of MWCNT/surfactant dispersions on the mechanical properties of Portland cement pastes

NASA Astrophysics Data System (ADS)

Rodríguez, B.; Quintero, J. H.; Arias, Y. P.; Mendoza-Reales, O. A.; Ochoa-Botero, J. C.; Toledo-Filho, R. D.

2017-12-01

This work studies the reinforcing effect of Multi Walled Carbon Nanotubes (MWCNT) on cement pastes. A 0.35% solid concentration of MWCNT in powder was dispersed in deionized water with sodium dodecyl sulfate (cationic surfactant), cetylpyridinium chloride (anionic surfactant) and triton X-100 (amphoteric surfactant) using an ultrasonic tip processor. Three concentrations of each surfactant (1mM, 10mM and 100mM) were tested, and all samples were sonicated until an adequate dispersion degree was obtained. Cement pastes with additions of carbon nanotubes of 0.15% by mass of cement were produced in two steps; first the dispersions of MWCNT were combined with the mixing water using an ultrasonic tip processor to guarantee homogeneity, and then cement was added and mixed until a homogeneous paste was obtained. Direct tensile strength, apparent density and open porosity of the pastes were measured after 7 days of curing. It was found that the MWCNT/surfactants dispersions decrease the mechanical properties of the cement based matrix due to an increased porosity caused by the presence of surfactants.

Cement-based materials' characterization using ultrasonic attenuation

NASA Astrophysics Data System (ADS)

Punurai, Wonsiri

The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.

Stability of GO Modified by Different Dispersants in Cement Paste and Its Related Mechanism.

PubMed

Long, Wu-Jian; Fang, Changle; Wei, Jingjie; Li, Haodao

2018-05-18

Graphene oxide (GO) is a potential material to be used as a nano-reinforcement in cement matrix. However, a prerequisite for GO to fulfill its function in the cement matrix is homogeneous dispersion. In this study, the effects of three different dispersing agents (DAs), including polycarboxylate-based high range water reducer (P-HRWR), naphthalene-based high range water reducer (N-HRWR), and air entraining agent (AEA) on the dispersion of GO in aqueous solution, simulated concrete pore solution (SCPS), and suspension of cement pastes were sequentially investigated. Results showed that the dispersion effect of GO in aqueous solutions was improved with different DAs. However, the homogeneous dispersion of GO in aqueous solution re-agglomerated in SCPS and suspension of cement pastes. It was concluded that as the cement content and pH of aqueous solutions increased, GOs re-agglomerated and precipitated in an alkaline solution. A possible mechanism was proposed in this study and it was believed that electrostatic interactions and steric hindrance provided by the P-HRWR further made GOs stable in aqueous solutions. The ions and pH of cement pastes increased with the increasing amount of cement, which caused the separation of P-HRWR from GOs. Therefore, GOs were re-agglomerated and absorbed on the surface of the cement particles, resulting in GOs sedimentation.

ESEM analysis of polymeric film in EVA-modified cement paste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, D.A.; Monteiro, P.J.M.

2005-10-01

Portland cement pastes modified by 20% weight (polymer/cement ratio) of poly(ethylene-co-vinyl acetate) (EVA) were prepared, cured, and immersed in water for 11 days. The effects of water saturation and drying on the EVA polymeric film formed in cement pastes were observed using environmental scanning electron microscopy (ESEM). This technique allowed the imaging of the EVA film even in saturated samples. The decrease of the relative humidity inside the ESEM chamber did not cause any visual modification of the polymeric film during its drying.

Water dynamics in hardened ordinary Portland cement paste or concrete: from quasielastic neutron scattering.

PubMed

Bordallo, Heloisa N; Aldridge, Laurence P; Desmedt, Arnaud

2006-09-14

Portland cement reacts with water to form an amorphous paste through a chemical reaction called hydration. In concrete the formation of pastes causes the mix to harden and gain strength to form a rock-like mass. Within this process lies the key to a remarkable peculiarity of concrete: it is plastic and soft when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways, houses, and dams. The character of the concrete is determined by the quality of the paste. Creep and shrinkage of concrete specimens occur during the loss and gain of water from cement paste. To better understand the role of water in mature concrete, a series of quasielastic neutron scattering (QENS) experiments were carried out on cement pastes with water/cement ratio varying between 0.32 and 0.6. The samples were cured for about 28 days in sealed containers so that the initial water content would not change. These experiments were carried out with an actual sample of Portland cement rather than with the components of cement studied by other workers. The QENS spectra differentiated between three different water interactions: water that was chemically bound into the cement paste, the physically bound or "glassy water" that interacted with the surface of the gel pores in the paste, and unbound water molecules that are confined within the larger capillary pores of cement paste. The dynamics of the "glassy" and "unboud" water in an extended time scale, from a hundred picoseconds to a few nanoseconds, could be clearly differentiated from the data. While the observed motions on the picosecond time scale are mainly stochastic reorientations of the water molecules, the dynamics observed on the nanosecond range can be attributed to long-range diffusion. Diffusive motion was characterized by diffusion constants in the range of (0.6-2) 10(-9) m(2)/s, with significant reduction compared to the rate of diffusion for bulk water. This reduction of the water diffusion is discussed in terms of the interaction of the water with the calcium silicate gel and the ions present in the pore water.

Preferential adsorption of polycarboxylate superplasticizers on cement and silica fume in ultra-high performance concrete (UHPC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroefl, Ch.; Gruber, M.; Plank, J., E-mail: sekretariat@bauchemie.ch.tum.de

2012-11-15

UHPC is fluidized particularly well when a blend of MPEG- and APEG-type PCEs is applied. Here, the mechanism for this behavior was investigated. Testing individual cement and micro silica pastes revealed that the MPEG-PCE disperses cement better than silica whereas the APEG-PCE fluidizes silica particularly well. This behavior is explained by preferential adsorption of APEG-PCE on silica while MPEG-PCEs exhibit a more balanced affinity to both cement and silica. Adsorption data obtained from individual cement and micro silica pastes were compared with those found for the fully formulated UHPC containing a cement/silica blend. In the UHPC formulation, both PCEs stillmore » exhibit preferential and selective adsorption similar as was observed for individual cement and silica pastes. Preferential adsorption of PCEs is explained by their different stereochemistry whereby the carboxylate groups have to match with the steric position of calcium ions/atoms situated at the surfaces of cement hydrates or silica.« less

Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroefl, Christof, E-mail: christof.schroefl@tu-dresden.de; Mechtcherine, Viktor; Vontobel, Peter

2015-09-15

Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. Inmore » the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1.« less

Carbonation-induced weathering effect on cesium retention of cement paste

NASA Astrophysics Data System (ADS)

Park, S. M.; Jang, J. G.

2018-07-01

Carbonation is inevitable for cement and concrete in repositories over an extended period of time. This study investigated the carbonation-induced weathering effect on cesium retention of cement. Cement paste samples were exposed to accelerated carbonation for different durations to simulate the extent of weathering among samples. The extent of carbonation in cement was characterized by XRD, TG and NMR spectroscopy, while the retention capacity for cesium was investigated by zeta potential measurement and batch adsorption tests. Though carbonation led to decalcification from the binder gel, it negatively charged the surface of cement hydrates and enhanced their cesium adsorption capacity.

Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

PubMed Central

Kirgiz, Mehmet Serkan

2014-01-01

Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement. PMID:24587737

Influence of viscosity modifying admixtures on the rheological behavior of cement and mortar pastes

NASA Astrophysics Data System (ADS)

Bouras, R.; Kaci, A.; Chaouche, M.

2012-03-01

The influence of Viscosity-modifying admixtures (VMA) dosage rate on the steady state rheological properties, including the yield stress, fluid consistency index and flow behaviour index, of cementitious materials is considered experimentally. The investigation is undertaken both at cement paste and mortar scales. It is found that the rheological behaviour of the material is in general dependent upon shear-rate interval considered. At sufficiently low shear-rates the materials exhibit shear-thinning. This behaviour is attributed to flow-induced defloculation of the solid particles and VMA polymer disentanglement and alignment. At relatively high shear-rates the pastes becomes shear-thickening, due to repulsive interactions among the solid particles. There is a qualitative difference between the influence of VMA dosage at cement and mortar scales: at cement scale we obtain a monotonic increase of the yield stress, while at mortar scale there exists an optimum VMA dosage for which the yield stress is a minimum. The flow behaviour index exhibit a maximum in the case of cement pastes and monotonically decreases in the case of mortars. On the other hand, the fluid consistency index presents a minimum for both cement pastes and mortars.

Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load

PubMed Central

2017-01-01

The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS—sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete. PMID:28891976

Properties of cement based composites modified using diatomaceous earth

NASA Astrophysics Data System (ADS)

Pokorný, Jaroslav; Pavlíková, Milena; Záleská, Martina; Pavlík, Zbyšek

2017-07-01

Diatomite belongs among natural materials rich on amorphous silica (a-SiO2). When finely milled, it can potentially substitute part of cement binder and positively support formation of more dense composite structure. In this connection, two types of diatomaceous earth applied as a partial substitution of 5, 10, 15, and 20 mass% of Portland cement in the composition of cement paste were studied. In the tested mixtures with cement blends, the amount of batch water remained same, with water/binder ratio 0.5. For fresh paste mixtures, initial and final setting times were measured. First, hardened pastes cured 28 days in water were characterized by their physical properties such as bulk density, matrix density and open porosity. Then, their mechanical and thermophysical parameters were assessed. Obtained results gave clear evidence of setting time shortening for pastes with diatomite what brought negative effect with respect to the impaired workability of fresh mixtures. On the other hand, there was observed strength improvement for mixtures containing diatomite with higher amount of SiO2. Here, the increase in mechanical resistivity was distinct up to 15 mass% of cement replacement. Higher cement substitution by diatomite resulted in an increase in porosity and thus improvement of thermal insulation properties.

Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load.

PubMed

Szeląg, Maciej

2017-09-11

The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS-sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete.

A speciation solver for cement paste modeling and the semismooth Newton method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Georget, Fabien, E-mail: fabieng@princeton.edu; Prévost, Jean H., E-mail: prevost@princeton.edu; Vanderbei, Robert J., E-mail: rvdb@princeton.edu

2015-02-15

The mineral assemblage of a cement paste may vary considerably with its environment. In addition, the water content of a cement paste is relatively low and the ionic strength of the interstitial solution is often high. These conditions are extreme conditions with respect to the common assumptions made in speciation problem. Furthermore the common trial and error algorithm to find the phase assemblage does not provide any guarantee of convergence. We propose a speciation solver based on a semismooth Newton method adapted to the thermodynamic modeling of cement paste. The strong theoretical properties associated with these methods offer practical advantages.more » Results of numerical experiments indicate that the algorithm is reliable, robust, and efficient.« less

α-TCP cements prepared by syringe-foaming: Influence of Na2HPO4 and surfactant concentration.

PubMed

Vásquez, A F; Domínguez, S; Loureiro Dos Santos, L A

2017-12-01

The lack of intrinsic open porosity in calcium phosphate cements slows down the resorption rate and bone ingrowth when implanted In Vivo. In this study, macroporous structures were obtained by mixing α-TCP cement with a foamed liquid phase containing different concentrations of sodium hydrogen phosphate and a nonionic surfactant. The cement paste was prepared by hand mixing in a novel system of two syringes connected by a tube. Two different liquid to powder (L/P) ratios were used to prepare the cement paste. The cement samples showed open macropores with diameters>100μm. The specimens prepared with lower L/P ratio showed smaller porosity, macroporosity and pore size distribution. The cohesion of the cement paste in liquid solutions was assessed by adding 2wt% sodium alginate to the liquid phase. This study suggests that the final macrostructure of the foamed cements can be controlled by varying the phosphate and surfactant concentrations in the liquid phase and the L/P ratio. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrical Properties of Cement-Based Composites with Carbon Nanotubes, Graphene, and Graphite Nanofibers.

PubMed

Yoo, Doo-Yeol; You, Ilhwan; Lee, Seung-Jung

2017-05-08

This study was conducted to evaluate the effect of the carbon-based nanomaterial type on the electrical properties of cement paste. Three different nanomaterials, multi-walled carbon nanotubes (MWCNTs), graphite nanofibers (GNFs), and graphene (G), were incorporated into the cement paste at a volume fraction of 1%. The self-sensing capacity of the cement composites was also investigated by comparing the compressive stress/strain behaviors by evaluating the fractional change of resistivity (FCR). The electrical resistivity of the plain cement paste was slightly reduced by adding 1 vol % GNFs and G, whereas a significant decrease of the resistivity was achieved by adding 1 vol % MWCNTs. At an identical volume fraction of 1%, the composites with MWCNTs provided the best self-sensing capacity with insignificant noise, followed by the composites containing GNFs and G. Therefore, the addition of MWCNTs was considered to be the most effective to improve the self-sensing capacity of the cement paste. Finally, the composites with 1 vol % MWCNTs exhibited a gauge factor of 113.2, which is much higher than commercially available strain gauges.

Electrical Properties of Cement-Based Composites with Carbon Nanotubes, Graphene, and Graphite Nanofibers

PubMed Central

Yoo, Doo-Yeol; You, Ilhwan; Lee, Seung-Jung

2017-01-01

This study was conducted to evaluate the effect of the carbon-based nanomaterial type on the electrical properties of cement paste. Three different nanomaterials, multi-walled carbon nanotubes (MWCNTs), graphite nanofibers (GNFs), and graphene (G), were incorporated into the cement paste at a volume fraction of 1%. The self-sensing capacity of the cement composites was also investigated by comparing the compressive stress/strain behaviors by evaluating the fractional change of resistivity (FCR). The electrical resistivity of the plain cement paste was slightly reduced by adding 1 vol % GNFs and G, whereas a significant decrease of the resistivity was achieved by adding 1 vol % MWCNTs. At an identical volume fraction of 1%, the composites with MWCNTs provided the best self-sensing capacity with insignificant noise, followed by the composites containing GNFs and G. Therefore, the addition of MWCNTs was considered to be the most effective to improve the self-sensing capacity of the cement paste. Finally, the composites with 1 vol % MWCNTs exhibited a gauge factor of 113.2, which is much higher than commercially available strain gauges. PMID:28481296

Influence of increasing amount of recycled concrete powder on mechanical properties of cement paste

NASA Astrophysics Data System (ADS)

Topič, Jaroslav; Prošek, Zdeněk; Plachý, Tomáš

2017-09-01

This paper deals with using fine recycled concrete powder in cement composites as micro-filler and partial cement replacement. Binder properties of recycled concrete powder are given by exposed non-hydrated cement grains, which can hydrate again and in small amount replace cement or improve some mechanical properties. Concrete powder used in the experiments was obtained from old railway sleepers. Infrastructure offer more sources of old concrete and they can be recycled directly on building site and used again. Experimental part of this paper focuses on influence of increasing amount of concrete powder on mechanical properties of cement paste. Bulk density, shrinkage, dynamic Young’s modulus, compression and flexural strength are observed during research. This will help to determine limiting amount of concrete powder when decrease of mechanical properties outweighs the benefits of cement replacement. The shrinkage, dynamic Young’s modulus and flexural strength of samples with 20 to 30 wt. % of concrete powder are comparable with reference cement paste or even better. Negative effect of concrete powder mainly influenced the compression strength. Only a 10 % cement replacement reduced compression strength by about 25 % and further decrease was almost linear.

Effect of blast furnace slag on self-healing of microcracks in cementitious materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Haoliang, E-mail: haoliang.huang@tudelft.nl; Ye, Guang; Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University

The physico-chemical process of self-healing in blast furnace slag cement paste was investigated in this paper. With a high slag content i.e., 66% in cement paste and saturated Ca(OH)₂ solution as activator, it was found that the reaction products formed in cracks are composed of C-S-H, ettringite, hydrogarnet and OH–hydrotalcite. The fraction of C-S-H in the reaction products is much larger than the other minerals. Large amount of ettringite formed in cracks indicates the leaching of SO₄⁻² ions from the bulk paste and consequently the recrystallization. Self-healing proceeds fast within 50 h and then slows down. According to thermodynamic modeling,more » when the newly formed reaction products are carbonated, the filling fraction of crack increases first and then decreases. Low soluble minerals such as silica gel, gibbsite and calcite are formed. Compared to Portland cement paste, the potential of self-healing in slag cement paste is higher when the percentage of slag is high. Highlights: • Self-healing reaction products in slag cement paste were characterized. • Self-healing reaction products formed in time were quantified with image analysis. • Self-healing in slag cement paste was simulated with a reactive transport model. • Effect of carbonation on self-healing was investigated by thermodynamic modeling. • Effect of slag on self-healing was discussed based on experiments and simulation.« less

XRD Analysis of Cement Paste Samples Exposed to the Simulated Environment of a Deep Repository - 12239

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreira, Eduardo G.A.; Marumo, Julio T.; Vicente, Roberto

2012-07-01

Portland cement materials are widely used as engineered barriers in repositories for radioactive waste. The capacity of such barriers to avoid the disposed of radionuclides to entering the biosphere in the long-term depends on the service life of those materials. Thus, the performance assessment of structural materials under a series of environmental conditions prevailing at the environs of repositories is a matter of interest. The durability of cement paste foreseen as backfill in a deep borehole for disposal of disused sealed radioactive sources is investigated in the development of the repository concept. Results are intended to be part of themore » body of evidence in the safety case of the proposed disposal technology. This paper presents the results of X-Ray Diffraction (XRD) Analysis of cement paste exposed to varying temperatures and simulated groundwater after samples received the radiation dose that the cement paste will accumulate until complete decay of the radioactive sources. The XRD analysis of cement paste samples realized in this work allowed observing some differences in the results of cement paste specimens that were submitted to different treatments. The cluster analysis of results was able to group tested samples according to the applied treatments. Mineralogical differences, however, are tenuous and, apart from ettringite, are hardly observed. The absence of ettringite in all the seven specimens that were kept in dry storage at high temperature had hardly occurred by natural variations in the composition of hydrated cement paste because ettringite is observed in all tested except the seven specimens. Therefore this absence is certainly the result of the treatments and could be explained by the decomposition of ettringite. Although the temperature of decomposition is about 110-120 deg. C, it may be initially decomposed to meta-ettringite, an amorphous compound, above 50 deg. C in the absence of water. Influence of irradiation on the mineralogical composition was not observed when the treatment was analyzed individually or when analyzed under the possible synergic effect with other treatments. However, the radiation dose to which specimens were exposed is only a fraction of the accumulated dose in cement paste until complete decay of some sources. Therefore, in the short term, the conditions deemed to prevail in the repository environment may not influence the properties of cement paste at detectable levels. Under the conditions presented in this work, it is not possible to predict the long term evolution of these properties. (authors)« less

Damage of Wood-Concrete Composite subjected to variable hygrometric conditions

NASA Astrophysics Data System (ADS)

Loulou, L.; Caré, S.; Le Roy, R.; Bornert, M.

2010-06-01

This paper discusses the factors influencing the durability of glued assemblies of wood and cementitious material under variable hygrometric conditions. The composite specimens are composed of cement paste connected to plywood using epoxy glue. The cement paste is subjected to autogeneous shrinkage and the wood is subjected to imbibition test. Plywood is used so that the swelling deformations due to the imbibition process are parallel to the connection plane. Swelling strains in wood are related to the water content measured by gammadensimetry technique. Global strains above and below the glue interface have been measured and have been compared to the free strains. We showed that there are restrained deformations at the glue interface and that the cement paste is damaged. Local strains have been characterized by means of the digital image correlation technique. We showed in particular that the deformations in wood are related to the microstructure of the layers of plywood and that the restrained deformations at the glue interface lead to a bending of the cement paste. In the case of strong adhesion properties, this bending induces cracking in cement paste.

Cement paste surface roughness analysis using coherence scanning interferometry and confocal microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apedo, K.L., E-mail: apedo@unistra.fr; Munzer, C.; He, H.

2015-02-15

Scanning electron microscopy and scanning probe microscopy have been used for several decades to better understand the microstructure of cementitious materials. Very limited work has been performed to date to study the roughness of cementitious materials by optical microscopy such as coherence scanning interferometry (CSI) and chromatic confocal sensing (CCS). The objective of this paper is to better understand how CSI can be used as a tool to analyze surface roughness and topography of cement pastes. Observations from a series of images acquired using this technique on both polished and unpolished samples are described. The results from CSI are comparedmore » with those from a STIL confocal microscopy technique (SCM). Comparison between both optical techniques demonstrates the ability of CSI to measure both polished and unpolished cement pastes. - Highlights: • Coherence scanning interferometry (CSI) was used to analyze cement paste surfaces. • The results from the CSI were compared with those from a confocal microscopy. • 3D roughness parameters were obtained using the window resizing method. • Polished and unpolished cement pastes were studied.« less

Measurement of tritium penetration through concrete material covered by various paints coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edao, Y.; Kawamura, Y.; Kurata, R.

The present study aims at obtaining fundamental data on tritium migration in porous materials, which include soaking effect, interaction between tritium and cement paste coated with paints and transient tritium sorption in porous cement. The amounts of tritium penetrated into or released from cement paste with epoxy and urethane paint coatings were measured. The tritium penetration amounts were increased with the HTO (tritiated water) exposure time. Time to achieve a saturated value of tritium sorption was more than 60 days for cement paste coated with epoxy paint and with urethane paint, while that for cement paste without any paint coatingmore » took 2 days to achieve it. The effect of tritium permeation reduction by the epoxy paint was higher than that of the urethane. Although their paint coatings were effective for reduction of tritium penetration through the cement paste which was exposed to HTO for a short period, it was found that the amount of tritium trapped in the paints became large for a long period. Tritium penetration rates were estimated by an analysis of one-dimensional diffusion in the axial direction of a thickness of a sample. Obtained data were helpful for evaluation of tritium contamination and decontamination. (authors)« less

Production, characterization, and mechanical behavior of cementitious materials incorporating carbon nanofibers

NASA Astrophysics Data System (ADS)

Yazdanbakhsh, Ardavan

Carbon nanotubes (CNTs) and carbon nanofirbers (CNFs) have excellent properties (mechanical, electrical, magnetic, etc.), which can make them effective nanoreinforcements for improving the properties of materials. The incorporation of CNT/Fs in a wide variety of materials has been researched extensively in the past decade. However, the past study on the reinforcement of cementitious materials with these nanofilaments has been limited. The findings from those studies indicate that CNT/Fs did not significantly improve the mechanical properties of cementitious materials. Two major parameters influence the effectiveness of any discrete inclusion in composite material: The dispersion quality of the inclusions and the interfacial bond between the inclusions and matrix. The main focus of this dissertation is on the dispersion factor, and consists of three main tasks: First a novel thermodynamic-based method for dispersion quantification was developed. Second, a new method, incorporating the utilization of silica fume, was devised to improve and stabilize the dispersion of CNFs in cement paste. And third, the dispersion quantification method and mechanical testing were employed to measure, compare, and correlate the dispersion and mechanical properties of CNF-incorporated cement paste produced with the conventional and new methods. Finally, the main benefits, including the increase in strength and resistance to shrinkage cracking, obtained from the utilization of CNFs in cement paste will be presented. The investigations and the corresponding results show that the novel dispersion quantification method can be implemented easily to perform a wide variety of tasks ranging from measuring dispersion of nanofilaments in composites using their optical/SEM micrographs as input, to measuring the effect of cement particle/clump size on the dispersion of nano inclusions in cement paste. It was found that cement particles do not affect the dispersion of nano inclusions in cement paste significantly while the dispersion of nano inclusions can notably degenerates if the cement particles are agglomerated. The novel dispersion quantification method shows that, the dispersion of CNFs in cement paste significantly improves by utilizing silica fume. However, it was found that the dispersion of silica fume particles is an important parameter and poorly dispersed silica fume cannot enhance the overall dispersion of nano inclusions in cementitious materials. Finally, the mechanical testing and experimentations showed that CNFs, in absence of moist curing, even if poorly dispersed, can provide important benefits in terms of strength and crack resistance.

Critical review: Injectability of calcium phosphate pastes and cements.

PubMed

O'Neill, R; McCarthy, H O; Montufar, E B; Ginebra, M-P; Wilson, D I; Lennon, A; Dunne, N

2017-03-01

Calcium phosphate cements (CPC) have seen clinical success in many dental and orthopaedic applications in recent years. The properties of CPC essential for clinical success are reviewed in this article, which includes properties of the set cement (e.g. bioresorbability, biocompatibility, porosity and mechanical properties) and unset cement (e.g. setting time, cohesion, flow properties and ease of delivery to the surgical site). Emphasis is on the delivery of calcium phosphate (CaP) pastes and CPC, in particular the occurrence of separation of the liquid and solid components of the pastes and cements during injection; and established methods to reduce this phase separation. In addition a review of phase separation mechanisms observed during the extrusion of other biphasic paste systems and the theoretical models used to describe these mechanisms are discussed. Occurrence of phase separation of calcium phosphate pastes and cements during injection limits their full exploitation as a bone substitute in minimally invasive surgical applications. Due to lack of theoretical understanding of the phase separation mechanism(s), optimisation of an injectable CPC that satisfies clinical requirements has proven difficult. However, phase separation of pastes during delivery has been the focus across several research fields. Therefore in addition to a review of methods to reduce phase separation of CPC and the associated constraints, a review of phase separation mechanisms observed during extrusion of other pastes and the theoretical models used to describe these mechanisms is presented. It is anticipated this review will benefit future attempts to develop injectable calcium phosphate based systems. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Novel Injectable Calcium Phosphate Bone Cement from Wet Chemical Precipitation Method

NASA Astrophysics Data System (ADS)

Hablee, S.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.; Singh, R.

2017-06-01

Calcium phosphate cement has been prepared via chemical precipitation method for injectable bone filling materials. Calcium hydroxide, Ca(OH)2, and diammonium hydrogen phosphate, (NH4)2HPO4, were used as calcium and phosphorus precursors respectively. The synthesized powder was mixed with water at different powder-to-liquid (P/L) ratios, which was adjusted at 0.8, 0.9, 1.0, 1.1 and 1.2. The influence of P/L ratio on the injectability, setting time and mechanical strength of calcium phosphate cement paste has been evaluated. The synthesized powder appeared as purely hydroxyapatite with nanosized and agglomerated spherical particles. All cement pastes show excellent injectability except for the paste with P/L ratio 1.2. Calcium phosphate cement with P/L ratio 1.1 shows the ideal cement for bone filler application with good injectability, the initial and final setting times of 30 min and 160 min, and the compression strength of 2.47 MPa. The result indicated that the newly developed calcium phosphate cement is physically suitable for bone filler application. This paper presents our investigation on the effect of P/L ratio on the handling and mechanical properties of calcium phosphate cement prepared via wet chemical precipitation method.

The influence of silanized nano-SiO{sub 2} on the hydration of cement paste: NMR investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bede, A., E-mail: Andrea.Bede@phys.utcluj.ro; Pop, A.; Ardelean, I.

2015-12-23

It is known that by adding a small amount of nanoparticles to the cement-based materials a strong influence on the workability, strength and durability is obtained. These characteristics of the material are fundamentally determined by the hydration process taking place after mixing the cement grains with water. In the present study the influence introduced by the addition of nano-silica with silanized surfaces on the hydration process was investigated using low-field nuclear magnetic resonance (NMR) relaxometry. The cement samples were prepared using gray cement at a water-to-cement ratio of 0.4 and a 5% addition of nanosilica. The surface of the nanoparticlesmore » was modified using a coating of Silane A174. The cement pastes were monitored during their standard curing time of 28 days. It was established that, by using unmodified nanosilica particles, an acceleration of the hydration process takes place as compared with the pure cement paste. On the other side, by adding silanized nanoparticles, the dormancy stage significantly extends and the hydration process is slower. This slowing down process could enhance the mechanical strength of cement based materials as a result of a better compaction of the hydrated samples.« less

Application of Bacillus subtilis 168 as a multifunctional agent for improvement of the durability of cement mortar.

PubMed

Park, Sung-Jin; Park, Jong-Myong; Kim, Wha-Jung; Ghim, Sa-Youl

2012-11-01

Microbiological calcium carbonate precipitation (MCCP) has been investigated for its ability to improve the durability of cement mortar. However, very few strains have been applied to crack remediation and strengthening of cementitious materials. In this study, we report the biodeposition of Bacillus subtilis 168 and its ability to enhance the durability of cement material. B. subtilis 168 was applied to the surface of cement specimens. The results showed a new layer of deposited organic-inorganic composites on the surface of the cement paste. In addition, the water permeability of the cement paste treated with B. subtilis 168 was lower than that of non-treated specimens. Furthermore, artificial cracks in the cement paste were completely remediated by the biodeposition of B. subtilis 168. The compressive strength of cement mortar treated with B. subtilis 168 increased by about 19.5% when compared with samples completed with only B4 medium. Taken together, these findings suggest that the biodeposition of B. subtilis 168 could be used as a sealing and coating agent to improve the strength and water resistance of concrete. This is the first paper to report the application of Bacillus subtilis 168 for its ability to improve the durability of cement mortar through calcium carbonate precipitation.

Effect of Nano-SiO₂ on the Hydration and Microstructure of Portland Cement.

PubMed

Wang, Liguo; Zheng, Dapeng; Zhang, Shupeng; Cui, Hongzhi; Li, Dongxu

2016-12-15

This paper systematically studied the modification of cement-based materials by nano-SiO₂ particles with an average diameter of about 20 nm. In order to obtain the effect of nano-SiO₂ particles on the mechanical properties, hydration, and pore structure of cement-based materials, adding 1%, 3%, and 5% content of nano-SiO₂ in cement paste, respectively. The results showed that the reaction of nano-SiO₂ particles with Ca(OH)₂ (crystal powder) started within 1 h, and formed C-S-H gel. The reaction speed was faster after aging for three days. The mechanical properties of cement-based materials were improved with the addition of 3% nano-SiO₂, and the early strength enhancement of test pieces was obvious. Three-day compressive strength increased 33.2%, and 28-day compressive strength increased 18.5%. The exothermic peak of hydration heat of cement increased significantly after the addition of nano-SiO₂. Appearance time of the exothermic peak was advanced and the total heat release increased. Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis showed that nano-SiO₂ promoted the formation of C-S-H gel. The results of mercury intrusion porosimetry (MIP) showed that the total porosity of cement paste with 3% nano-SiO₂ was reduced by 5.51% and 5.4% at three days and 28 days, respectively, compared with the pure cement paste. At the same time, the pore structure of cement paste was optimized, and much-detrimental pores and detrimental pores decreased, while less harmful pores and innocuous pores increased.

Smoking cessation interventions from health care providers before and after the national smoke-free law in France.

PubMed

Kennedy, Ryan David; Behm, Ilan; Craig, Lorraine; Thompson, Mary E; Fong, Geoffrey T; Guignard, Romain; Beck, Francois

2012-02-01

Smoking cessation advice from health care providers (HCP) is well-known to be associated with increased quitting. This study sought to understand the extent to which smokers in France who visited a HCP around the time of the implementation of the national ban on smoking received encouragement to quit from a HCP and what kinds of intervention were provided. HCP may have a unique opportunity during the implementation phase of smoke-free laws to address their patients' smoking behaviours to increase the likelihood of success at a time when smokers' readiness and interest in quitting may be higher. Telephone interviews were conducted among adult smokers (n = 1067) before and after the two-phase (2007 and 2008) national ban on indoor smoking as part of the International Tobacco Control (ITC) France Survey. In the survey, smokers were asked whether they had visited a HCP in the past 6 months and, if so, whether they had received cessation encouragement, and/or other interventions to support quitting such as prescriptions for stop-smoking medication. Most smokers (61%) reported visiting a HCP in the 6 months prior to the first phase of the national smoke-free ban, and 58% after the time of the hospitality ban. Of these, most reported they did not receive any assistance from a HCP before (54%) or after (64%) the smoke-free law. Among those who reported an intervention, the most common were only encouragement to quit (58% in Wave 1 and 49% in Wave 2), or receiving both encouragement and a pamphlet (31% in both Wave 1 and 2). The combination of prescriptions for stop-smoking medicine and encouragement to quit increased from 8% in 2007 to 22% in 2008. The smokers who received an intervention were more likely (OR 1.9, 95% CI: 1.2-2.9) to report that they were thinking about quitting. This study demonstrates that HCP in France are well positioned to provide smoking cessation encouragement and other interventions to a majority of smokers and thus the importance of taking measures to increase their involvement, particularly when population-level tobacco control policies, such as smoke-free laws, are being implemented.

Investigation on the potential of waste cooking oil as a grinding aid in Portland cement.

PubMed

Li, Haoxin; Zhao, Jianfeng; Huang, Yuyan; Jiang, Zhengwu; Yang, Xiaojie; Yang, Zhenghong; Chen, Qing

2016-12-15

Although there are several methods for managing waste cooking oil (WCO), a significant result has not been achieved in China. A new method is required for safe WCO management that minimizes the environmental threat. In this context, this work was developed in which cement clinker and gypsum were interground with various WCOs, and their properties, such as grindability, water-cement ratio required to achieve a normal consistency, setting times, compressive strength, contents of calcium hydroxide and ettringite in the hardened paste, microstructure and economic and environmental considerations, were addressed in detail. The results show that, overall, WCO favorably improves cement grinding. WCO prolonged the cement setting times and resulted in longer setting times. Additionally, more remarkable effects were found in cements in which WCO contained more unsaturated fatty acid. WCOs increased the cement strength. However, this enhancement was rated with respect to the WCO contents and components. WCOs decreased the CH and AFt contents in the cement hardened paste. Even the AFt content at later ages was reduced when WCO was used. WCO also densify microstructure of the hardened cement paste. It is economically and environmentally feasible to use WCOs as grinding aids in the cement grinding process. These results contribute to the application of WCOs as grinding aids and to the safe management of WCO. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physician Weight Recommendations for Overweight and Obese Firefighters, United States, 2011–2012

PubMed Central

Wilkinson, Michelle Lynn; Brown, Austin Lane; Poston, Walker Seward Carlos; Haddock, Christopher Keith; Jahnke, Sara Anne

2014-01-01

Introduction National guidelines state that health care professionals (HCPs) should advise patients on the importance of maintaining a healthy weight. Firefighters have high rates of obesity, and cardiovascular events are the leading cause of line-of-duty deaths in firefighters. This study assessed the association of age and body mass index (BMI) with HCP weight recommendations among male firefighters. Methods We used data on self-reported HCP weight recommendations and measured BMI from a 2011–2012 national sample of male firefighters (N = 1,002). HCP recommendations were recorded as no advice, maintain, gain, or lose weight, and BMI was categorized as normal (<25.0 kg/m2), overweight (25.0–29.9 kg/m2), class I obese (30.0–34.9 kg/m2), and class II or III obese (≥35.0 kg/m2). We used multinomial logistic regression to estimate the odds of receiving weight advice by age and BMI categories. Results Most firefighters (96%) reported visiting an HCP in the past year. Most (69%) firefighters and 48% of class I to III obese firefighters reported receiving no weight advice. Higher BMI predicted HCP advice to lose weight (odds ratio class I obese vs normal weight: 12.98; 95% confidence interval: 5.38–31.34). Younger firefighters were less likely to receive weight loss advice than older firefighters, except among those who were class II or III obese. Conclusions HCPs are important sources of health information for firefighters. Overweight and obese firefighters, particularly those who are younger, do not consistently receive HCP advice to lose weight. This marks a missed opportunity to prevent further weight gain and reduce obesity-related health outcomes. PMID:25010998

The influence of cellulose nanocrystals on the microstructure of cement paste

Treesearch

Yizheng Cao; Nannan Tian; David Bahr; Pablo D. Zavattieri; Jeffrey Youngblood; Robert J. Moon; Jason Weiss

2016-01-01

This paper reports the influence of raw and sonicated cellulose nanocrystals (CNCs) on the micro-structure of cement paste. A novel centrifugation method is designed to measure the concentrations of the adsorbed CNCs (aCNCs) on the cement surface, and the free CNCs (fCNCs) which are mobile in water. It is found that, the majority of the CNCs (>94%) are aCNCs....

Strength and durability of concrete: Effects of cement paste-aggregate interfaces. Part 2: Significance of transition zones on physical and mechanical properties of portland cement mortar; Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, T.F.F.; Cohen, M.D.; Chen, W.F.

1998-08-01

The research was based on a two-part basic research investigation studying the effects of cement paste-aggregate interfaces (or interfacial transition zones-ITZ) on strength and durability of concrete. Part 1 dealt with the theoretical study and Part 2 dealt with the experimental.

Non-autoclaved aerated concrete with mineral additives

NASA Astrophysics Data System (ADS)

Il'ina, L. V.; Rakov, M. A.

2016-01-01

We investigated the effect of joint grinding of Portland cement clinker, silica and carbonate components and mineral additives to specific surface of 280 - 300 m2/kg on the properties (strength, average density and thermal conductivity) of non-autoclaved aerated concrete, and the porosity of the hardened cement paste produced from Portland cement clinker with mineral additives. The joint grinding of the Portland cement clinker with silica and carbonate components and mineral additives reduces the energy consumption of non-autoclaved aerated concrete production. The efficiency of mineral additives (diopside, wollastonite) is due to the closeness the composition, the type of chemical bonds, physical and chemical characteristics (specific enthalpy of formation, specific entropy) to anhydrous clinker minerals and their hydration products. Considering the influence of these additions on hydration of clinker minerals and formation of hardened cement paste structure, dispersed wollastonite and diopside should be used as mineral additives. The hardness and, consequently, the elastic modulus of diopside are higher than that of hardened cement paste. As a result, there is a redistribution of stresses in the hardened cement paste interporous partitions and hardening, both the partitions and aerated concrete on the whole. The mineral additives introduction allowed to obtain the non-autoclaved aerated concrete with average density 580 kg/m3, compressive strength of 3.3 MPa and thermal conductivity of 0.131 W/(m.°C).

Development of high-viscosity, two-paste bioactive bone cements.

PubMed

Deb, S; Aiyathurai, L; Roether, J A; Luklinska, Z B

2005-06-01

Self-curing two-paste bone cements have been developed using methacrylate monomers with a view to formulate cements with low polymerization exotherm, low shrinkage, better mechanical properties, and improved adhesion to bone and implant surfaces. The monomers include bis-phenol A glycidyl dimethacrylate (bis-GMA), urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) as a viscosity modifier. Two-paste systems were formulated containing 60% by weight of a bioactive ceramic, hydroxyapatite. A methacroyloxy silane (A174) was used as a coupling agent due to its higher water stability in comparison to other aminosilanes to silanate the hydroxyapatite particles prior to composite formulation. A comparison of the FT-infrared spectrum of hydroxyapatite and silanated hydroxyapatite showed the presence of the carbonyl groups ( approximately 1720 cm(-1)), -C=C-( approximately 1630 cm(-1)) and Si-O- (1300-1250 cm(-1)) which indicated the availability of silane groups on the filler surface. Two methods of mixing were effected to form the bone cement: firstly by mixing in an open bowl and secondly by extruding the two pastes by an auto-mixing tip using a gun to dispense the pastes. Both types of cements yielded low polymerization exotherms with good mechanical properties; however, the lower viscosity of UDMA allowed better extrusion and handling properties. A biologically active apatite layer formed on the bone cement surface within a short period after its immersion in simulated body fluid, demonstrating in vitro bioactivity of the composite. This preliminary data thus suggests that UDMA is a viable alternative to bis-GMA as a polymerizable matrix in the formation of bone cements.

Utilization of municipal sewage sludge as additives for the production of eco-cement.

PubMed

Lin, Yiming; Zhou, Shaoqi; Li, Fuzhen; Lin, Yixiao

2012-04-30

The effects of using dried sewage sludge as additive on cement property in the process of clinker burning were investigated in this paper. The eco-cement samples were prepared by adding 0.50-15.0% of dried sewage sludge to unit raw meal, and then the mixtures were burned at 1450 °C for 2 h. The results indicated that the major components in the eco-cement clinkers were similar to those in ordinary Portland cement. Although the C(2)S phase formation increased with the increase of sewage sludge content, it was also found that the microstructure of the mixture containing 15.0% sewage sludge in raw meal was significantly different and that a larger amount of pores were distributed in the clinker. Moreover, all the eco-cement pastes had a longer initial setting time and final setting time than those of plain cement paste, which increased as the sewage sludge content in the raw meal increased. All the eco-cement pastes had lower early flexural strengths, which increased as the sewage sludge content increased, while the compressive strengths decreased slightly. However, this had no significant effect on all the strengths at later stages. Furthermore, the leaching concentrations of all the types of eco-cement clinkers met the standard of Chinese current regulatory thresholds. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of Nano-SiO2 on the Hydration and Microstructure of Portland Cement

PubMed Central

Wang, Liguo; Zheng, Dapeng; Zhang, Shupeng; Cui, Hongzhi; Li, Dongxu

2016-01-01

This paper systematically studied the modification of cement-based materials by nano-SiO2 particles with an average diameter of about 20 nm. In order to obtain the effect of nano-SiO2 particles on the mechanical properties, hydration, and pore structure of cement-based materials, adding 1%, 3%, and 5% content of nano-SiO2 in cement paste, respectively. The results showed that the reaction of nano-SiO2 particles with Ca(OH)2 (crystal powder) started within 1 h, and formed C–S–H gel. The reaction speed was faster after aging for three days. The mechanical properties of cement-based materials were improved with the addition of 3% nano-SiO2, and the early strength enhancement of test pieces was obvious. Three-day compressive strength increased 33.2%, and 28-day compressive strength increased 18.5%. The exothermic peak of hydration heat of cement increased significantly after the addition of nano-SiO2. Appearance time of the exothermic peak was advanced and the total heat release increased. Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis showed that nano-SiO2 promoted the formation of C–S–H gel. The results of mercury intrusion porosimetry (MIP) showed that the total porosity of cement paste with 3% nano-SiO2 was reduced by 5.51% and 5.4% at three days and 28 days, respectively, compared with the pure cement paste. At the same time, the pore structure of cement paste was optimized, and much-detrimental pores and detrimental pores decreased, while less harmful pores and innocuous pores increased. PMID:28335369

Photoactive glazed polymer-cement composite

NASA Astrophysics Data System (ADS)

Baltes, Liana; Patachia, Silvia; Tierean, Mircea; Ekincioglu, Ozgur; Ozkul, Hulusi M.

2018-04-01

Macro defect free cements (MDF), a kind of polymer-cement composites, are characterized by remarkably high mechanical properties. Their flexural strengths are 20-30 times higher than those of conventional cement pastes, nearly equal to that of an ordinary steel. The main drawback of MDF cements is their sensitivity to water. This paper presents a method to both diminish the negative impact of water on MDF cements mechanical properties and to enlarge their application by conferring photoactivity. These tasks were solved by glazing MDF cement with an ecological glaze containing nano-particles of TiO2. Efficiency of photocatalytic activity of this material was tested against methylene blue aqueous solution (4.4 mg/L). Influence of the photocatalyst concentration in the glaze paste and of the contact time on the photocatalysis process (efficiency and kinetic) was studied. The best obtained photocatalysis yield was of 97.35%, after 8 h of exposure to 254 nm UV radiation when used an MDF glazed with 10% TiO2 in the enamel paste. Surface of glazed material was characterized by optic microscopy, scratch test, SEM, XRD, and EDS. All these properties were correlated with the aesthetic aspect of the glazed surface aiming to propose using of this material for sustainable construction development.

Experimental Investigation of Multi-mode Fiber Laser Cutting of Cement Mortar.

PubMed

Lee, Dongkyoung; Pyo, Sukhoon

2018-02-10

This study successfully applied multi-mode laser cutting with the variation of the laser cutting speed to cement mortar for the first time. The effects of the amount of silica sand in the cement mortar on laser cutting are tested and analyzed. The kerf width and penetration depth of the specimens after laser cutting are investigated. As the laser cutting speed increases, the penetration depth decreases for both cement paste and cement mortar, whereas the kerf width becomes saturated and increases, respectively, for cement paste and cement mortar. Cross sections of the specimens are compared with illustrations. Top-view images of the cement mortar with indicators of the physical characteristics, such as re-solidification, burning, and cracks are examined, and the possible causes of these characteristics are explained. The optical absorption rates of cement-based materials are quantified at wide ranges of wavelength to compare the absorption rates in accordance with the materials compositions. The chemical composition variation before and after laser cutting is also compared by EDX (Energy Dispersive X-Ray) analysis. In addition to these observations, material removal mechanisms for cement mortar are proposed.

Experimental Investigation of Multi-mode Fiber Laser Cutting of Cement Mortar

PubMed Central

2018-01-01

This study successfully applied multi-mode laser cutting with the variation of the laser cutting speed to cement mortar for the first time. The effects of the amount of silica sand in the cement mortar on laser cutting are tested and analyzed. The kerf width and penetration depth of the specimens after laser cutting are investigated. As the laser cutting speed increases, the penetration depth decreases for both cement paste and cement mortar, whereas the kerf width becomes saturated and increases, respectively, for cement paste and cement mortar. Cross sections of the specimens are compared with illustrations. Top-view images of the cement mortar with indicators of the physical characteristics, such as re-solidification, burning, and cracks are examined, and the possible causes of these characteristics are explained. The optical absorption rates of cement-based materials are quantified at wide ranges of wavelength to compare the absorption rates in accordance with the materials compositions. The chemical composition variation before and after laser cutting is also compared by EDX (Energy Dispersive X-Ray) analysis. In addition to these observations, material removal mechanisms for cement mortar are proposed. PMID:29439431

Influence of various amount of diatomaceous earth used as cement substitute on mechanical properties of cement paste

NASA Astrophysics Data System (ADS)

Pokorný, Jaroslav; Pavlíková, Milena; Medved, Igor; Pavlík, Zbyšek; Zahálková, Jana; Rovnaníková, Pavla; Černý, Robert

2016-06-01

Active silica containing materials in the sub-micrometer size range are commonly used for modification of strength parameters and durability of cement based composites. In addition, these materials also assist to accelerate cement hydration. In this paper, two types of diatomaceous earths are used as partial cement replacement in composition of cement paste mixtures. For raw binders, basic physical and chemical properties are studied. The chemical composition of tested materials is determined using classical chemical analysis combined with XRD method that allowed assessment of SiO2 amorphous phase content. For all tested mixtures, initial and final setting times are measured. Basic physical and mechanical properties are measured on hardened paste samples cured 28 days in water. Here, bulk density, matrix density, total open porosity, compressive and flexural strength, are measured. Relationship between compressive strength and total open porosity is studied using several empirical models. The obtained results give evidence of high pozzolanic activity of tested diatomite earths. Their application leads to the increase of both initial and final setting times, decrease of compressive strength, and increase of flexural strength.

Temperature influence on water transport in hardened cement pastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drouet, Emeline; Poyet, Stéphane, E-mail: stephane.poyet@cea.fr; Torrenti, Jean-Michel

2015-10-15

Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

Effects of Curing Temperature and Pressure on the Chemical, Physical, and Mechanical Properties of Portland Cement

NASA Astrophysics Data System (ADS)

Pang, Xueyu

This dissertation mainly focuses on studying the fundamental hydration kinetics and mechanisms of Portland cement as well as the effects of curing temperature and pressure on its various properties. An innovative test apparatus has been developed in this study to cure and test cement paste specimens under in-situ conditions, such as down-hole in oil wells with high temperature and high pressure. Two series of tests were performed using cement pastes prepared with four different classes of oilwell cement (namely Class A, C, G, and H cements). Specimens in groups of four were cured at temperatures ranging from ambient to 60 °C and pressures ranging from 0.69 to 51.7 MPa for a period of 48 or 72 hours. The density and w/c ratio of the specimens at the time of casting as well as at the end of the curing period were recorded. Total chemical shrinkage of the cement paste was measured continuously during the entire hydration period while tensile strength was obtained at the end of the curing period using both water pressure and splitting tension test methods. Due to capacity limitations of the test equipment, in-situ tensile strength was obtained for only one test series with a highest curing pressure of 13.1 MPa. Specimens from the other test series were depressurized before the tensile strength tests. Chemical shrinkage test is an important method of measuring cement hydration kinetics in that the normalized total chemical shrinkage is approximately equal to the degree of cement hydration. By studying the correlations between the chemical shrinkage and the non-evaporable water content of cement during hydration, a multi-linear model is first proposed to estimate the normalization factors for different types of cement under different curing conditions. Based on the hydration kinetics data obtained from chemical shrinkage test results, a new approach of modeling the effect of curing temperature and pressure on cement hydration kinetics is proposed. It is found that when a hydration kinetics curve is represented by an unknown function, the effect of curing condition on the curve can be modeled by incorporating a simple scale factor in this function. The relationship between this scale factor and curing condition is described by chemical kinetics laws. While the proposed new approach of modeling cement hydration kinetics has the advantage of being widely applicable to different types of cement, it only explains one influence factor of cement hydration (i.e. the curing condition). In order to take into account other influence factors and to further understand the fundamental mechanisms of cement hydration, a more complex particle-based numerical hydration model is developed by combining the two well-known cement hydration mechanisms, namely the nucleation and growth controlled mechanism and the diffusion controlled mechanism. The model is applied to experimental data of both C3S hydration in dilute suspensions and Class H cement paste hydration. Excellent agreement is observed between experimental and modeled results. Three rate-controlling parameters with clear physical meanings can be identified from the proposed model. Fitted model parameters are found to be in reasonable agreement with experimental observation. The dependencies of these parameters on particle size, cement composition, w/c ratio, and curing condition are also investigated. Finally, the importance of cement hydration kinetics is illustrated by showing their close correlations with the physical and mechanical properties. The various influence factors, including the curing temperature and pressure, of physical and mechanical property test results (particularly density and tensile strength) are evaluated. Potential damage mechanisms of cement paste specimens during depressurization are studied by analyzing the deformation behavior of the entire system consisting of the cement paste and pressurizing water.

Combined Effects of Temperature and Irradiation on Concrete Damage

DOE PAGES

Le Pape, Yann; Giorla, Alain; Sanahuja, Julien

2016-01-01

Aggregate radiation-induced volumetric expansion (RIVE) is a predominant mechanism in the formation of mechanical damage in the hardened cement paste (hcp) of irradiated concrete under fast-neutron flux (Giorla et al. 2015). Among the operating conditions difference between test reactors and light water reactors (LWRs), the difference of irradiation flux and temperature is significant. While a temperature increase is quite generally associated with a direct, or indirect (e.g., by dehydration) loss of mechanical properties (Maruyama et al. 2014), we found that it causes a partial annealing of irradiation amorphization of α-quartz, hence, reducing RIVE rate. Based on data collected by Bykovmore » et al. (1981), an incremental RIVE model coupling neutron fluence and temperature is developed. The elastic properties and coefficient of thermal expansion (CTE) of irradiated polycrystalline quartz are interpreted through analytical homogenization of experimental data on irradiated α-quartz published by Mayer and Lecomte (1960). Moreover, the proposed model, implemented in the meso-scale simulation code AMIE, is compared to experimental data obtained on ordinary concrete made of quartz/quartzite aggregate (Dubrovskii et al. 1967). Substantial discrepancy, in terms of damage and volumetric expansion developments, is found when comparing irradiation scenarios assuming constant flux and temperature, as opposed to more realistic test reactor operation conditions.« less

Solidification of ion exchange resins saturated with Na+ ions: Comparison of matrices based on Portland and blast furnace slag cement

NASA Astrophysics Data System (ADS)

Lafond, E.; Cau dit Coumes, C.; Gauffinet, S.; Chartier, D.; Stefan, L.; Le Bescop, P.

2017-01-01

This work is devoted to the conditioning of ion exchange resins used to decontaminate radioactive effluents. Calcium silicate cements may have a good potential to encapsulate spent resins. However, certain combinations of cement and resins produce a strong expansion of the final product, possibly leading to its full disintegration. The focus is placed on the understanding of the behaviour of cationic resins in the Na+ form in Portland or blast furnace slag (CEM III/C) cement pastes. During hydration of the Portland cement paste, the pore solution exhibits a decrease in its osmotic pressure, which causes a transient expansion of small magnitude of the resins. At 20 °C, this expansion takes place just after setting in a poorly consolidated material and is sufficient to induce cracks. In the CEM III/C paste, swelling of the resins also occurs, but before the end of setting, and induces limited stress in the matrix which is still plastic.

Evaluation of the suitability of tin slag in cementitious materials: Mechanical properties and Leaching behaviour

NASA Astrophysics Data System (ADS)

Rustandi, Andi; Wafa' Nawawi, Fuad; Pratesa, Yudha; Cahyadi, Agung

2018-01-01

Tin slag, a by-product of tin production has been used in cementitious application. The present investigation focuses on the suitability of tin slag as primary component in cement and as component that substitute some amount of Portland Cement. The tin slags studied were taken from Bangka, Indonesia. The main contents of the tin slag are SiO2, Al2O3, and Fe2O3 according to the XRF investigation. The aim of this article was to study the mechanical behaviour (compressive strength), microstructure and leaching behaviour of tin slag blended cement. This study used air-cooled tin slag that had been passed through 400# sieve to replace Portland Cement with ratio 0, 10, 20, 30, 40 by weight. Cement pastes and tin slag blended cement pastes were prepared by using water/cement ratio (W/C) of 0.40 by weight and hydrated for various curing ages of 3, 7, 14 days The microstructure of the raw tin slag was investigated using Scanning Electron Microscope (SEM). The phase composition of each cement paste was investigated using X-ray Diffraction (XRD). The aim of the leachability test was to investigate the environmental impacts of tin slag blended cement product in the range 4-8 pH by using static pH-dependent leaching test. The result show that the increase of the tin slag content decreasing the mortar compressive strength at early ages. The use of tin slag in cement provide economic benefits for all related industries.

Impact of drying on pore structures in ettringite-rich cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galan, I., E-mail: isabelgalan@abdn.ac.uk; Beltagui, H.; García-Maté, M.

Drying techniques affect the properties of cement pastes to varying extents. The effect of different drying techniques on calcium sulfoaluminate-based (C$A) cements and their constituent phases is reported for a range of simulated and commercial C$A pastes which are benchmarked against an OPC paste. The recommended methodologies used to dry samples were identified from the literature and include D-drying and solvent exchange. These methods were used in conjunction with mercury intrusion porosimetry (MIP) and X-ray powder diffraction (XRPD) measurements to assess the changes in pore structure and the damage to crystalline phases, respectively. D-drying and isopropanol exchange are the mostmore » satisfactory and least damaging methods for drying C$A based pastes.« less

Upscaling Cement Paste Microstructure to Obtain the Fracture, Shear, and Elastic Concrete Mechanical LDPM Parameters.

PubMed

Sherzer, Gili; Gao, Peng; Schlangen, Erik; Ye, Guang; Gal, Erez

2017-02-28

Modeling the complex behavior of concrete for a specific mixture is a challenging task, as it requires bridging the cement scale and the concrete scale. We describe a multiscale analysis procedure for the modeling of concrete structures, in which material properties at the macro scale are evaluated based on lower scales. Concrete may be viewed over a range of scale sizes, from the atomic scale (10 -10 m), which is characterized by the behavior of crystalline particles of hydrated Portland cement, to the macroscopic scale (10 m). The proposed multiscale framework is based on several models, including chemical analysis at the cement paste scale, a mechanical lattice model at the cement and mortar scales, geometrical aggregate distribution models at the mortar scale, and the Lattice Discrete Particle Model (LDPM) at the concrete scale. The analysis procedure starts from a known chemical and mechanical set of parameters of the cement paste, which are then used to evaluate the mechanical properties of the LDPM concrete parameters for the fracture, shear, and elastic responses of the concrete. Although a macroscopic validation study of this procedure is presented, future research should include a comparison to additional experiments in each scale.

Upscaling Cement Paste Microstructure to Obtain the Fracture, Shear, and Elastic Concrete Mechanical LDPM Parameters

PubMed Central

Sherzer, Gili; Gao, Peng; Schlangen, Erik; Ye, Guang; Gal, Erez

2017-01-01

Modeling the complex behavior of concrete for a specific mixture is a challenging task, as it requires bridging the cement scale and the concrete scale. We describe a multiscale analysis procedure for the modeling of concrete structures, in which material properties at the macro scale are evaluated based on lower scales. Concrete may be viewed over a range of scale sizes, from the atomic scale (10−10 m), which is characterized by the behavior of crystalline particles of hydrated Portland cement, to the macroscopic scale (10 m). The proposed multiscale framework is based on several models, including chemical analysis at the cement paste scale, a mechanical lattice model at the cement and mortar scales, geometrical aggregate distribution models at the mortar scale, and the Lattice Discrete Particle Model (LDPM) at the concrete scale. The analysis procedure starts from a known chemical and mechanical set of parameters of the cement paste, which are then used to evaluate the mechanical properties of the LDPM concrete parameters for the fracture, shear, and elastic responses of the concrete. Although a macroscopic validation study of this procedure is presented, future research should include a comparison to additional experiments in each scale. PMID:28772605

Development of fluorapatite cement for dental enamel defects repair.

PubMed

Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

2011-06-01

In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

Thermal Properties of Cement-Based Composites for Geothermal Energy Applications.

PubMed

Bao, Xiaohua; Memon, Shazim Ali; Yang, Haibin; Dong, Zhijun; Cui, Hongzhi

2017-04-27

Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural-functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs). Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles.

Thermal Properties of Cement-Based Composites for Geothermal Energy Applications

PubMed Central

Bao, Xiaohua; Memon, Shazim Ali; Yang, Haibin; Dong, Zhijun; Cui, Hongzhi

2017-01-01

Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural–functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs). Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles. PMID:28772823

The influence of pozzolanic materials on the mechanical stability of aluminous cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collepardi, M.; Monosi, S.; Piccioli, P.

1995-07-01

High alumina cement is particularly suitable for manufacturing sulphate resistant concretes and in particular cement mixes which are able resist the sear water aggression. High alumina cement paste, in the presence of silica fume, shows an increasing strength trend even at 20 C and 40 C, since this pozzolan causes the formation of gehlenite hydrate (C{sub 2}ASH{sub 8}) and therefore strongly reduces the transformation of hexagonal aluminate hydrates (CAH{sub 10}, C{sub 2}AH{sub 8}) into the cubic hydrate (C{sub 3}AH{sub 6}) which is responsible for the strength loss of high-alumina cement mixes at higher temperatures (>20 C). On the contrary, flymore » ash is not suitable for reducing the transformation of hexagonal hydrates into the cubic phase. Consequently, the strength at 20 C and 40 C of the fly ash-high alumina cement mixes decrease as well as the high alumina cement pastes in the absence of pozzolan.« less

The Portland cement aggregate bond : influence of surface area of the coarse aggregate as a function of lithology.

DOT National Transportation Integrated Search

1972-01-01

Presented is a direct tensile test for measuring the bond of rock or mineral surfaces to portland cement paste, or for measuring the tensile strength of neat paste or of mortar specimens, devised using commercially available gripping devices and prep...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bossa, Nathan; Chaurand, Perrine; Levard, Clément

Nanomaterials are increasingly being used to improve the properties and functions of common building materials. A new type of self-cleaning cement incorporating TiO 2 nanomaterials (TiO 2-NMs) with photocatalytic properties is now marketed. This promising cement might provide air pollution-reducing properties but its environmental impact must be validated. During cement use and aging, an altered surface layer is formed that exhibits increased porosity. The surface layer thickness alteration and porosity increase with the cement degradation rate. The hardened cement paste leaching behavior has been fully documented, but the fate of incorporated TiO 2-NMs and their state during/after potential release ismore » currently unknown. In this study, photocatalytic cement pastes with increasing initial porosity were leached at a lab-scale to produce a range of degradation rates concerning the altered layer porosity and thickness. No dissolved Ti was released during leaching, only particulate TiO 2-NM release was detected. The extent of release from this batch test simulating accelerated worst-case scenario was limited and ranged from 18.7 ± 2.1 to 33.5 ± 5.1 mg of Ti/m 2 of cement after 168 h of leaching. TiO 2-NMs released into neutral aquatic media (simulate pH of surface water) were not associated or coated by cement minerals. The TiO 2-NM release mechanism is suspected to start from freeing of TiO 2-NMs in the altered layer pore network due to partial cement paste dissolution followed by diffusion into the bulk pore solution to the surface. The extent of TiO 2-NM release was not solely related to the cement degradation rate.« less

[Effect of ceramic thickness and resin cement shades on final color of heat-pressed ceramic veneers].

PubMed

Ren, D F; Zhan, K R; Chen, X D; Xing, W Z

2017-02-09

Objective: To analyze the effect of ceramic materials thickness and resin cement shades on the final color of ceramic veneers in the discolored teeth, and to investigate the color agreement of try-in pastes to the corresponding resin cements. Methods: Sixty artificial maxillary central incisor teeth (C2 shade) were used to simulate the natural discolored teeth and prepared according to veneer tooth preparation protocol. Veneers of different thickness in the body region (0.50 and 0.75 mm) were fabricated using ceramic materials (LT A2 shade, IPS e.max Press). The ceramic veneer specimens were bonded to the artificial teeth using the 6 shades of resin cements (Variolink Veneer: shades of LV-3, LV-2, HV+3; RelyX™ Veneer: shades of TR, A3, WO) ( n= 5). A clinical spectrophotometer was used to measure the color parameters of ceramic veneers at the cervical, body and incisal regions. Color changes of veneers before and after cementation were calculated and registered as ΔE1, and the changes between try-in paste and the corresponding resin cements were registered as ΔE2. Results: Three-way ANOVA indicated that ΔE1 and ΔE2 values were significantly affected by the ceramic thickness, resin cement shades and measuring regions ( P< 0.05). The ΔE1 values of six shades ranged from 0.59-8.27. The ΔE1 values were more than 2.72 when the ceramic veneers were cemented with resin cements in shades of HV+3 and WO. The ΔE2 values of six shades ranged from 0.60-2.56. The shades of HV+3, WO and A3 resin cements were more than 1.60. Conclusions: Different thickness of ceramic materials, resin cement shades and measuring regions could affect the final color of ceramic veneers. The color differences of some resin cements and corresponding try-in pastes might be observed in clinical practice.

HIV testing among sexually active Hispanic/Latino MSM in Miami-Dade County and New York City: opportunities for increasing acceptance and frequency of testing.

PubMed

Joseph, Heather A; Belcher, Lisa; O'Donnell, Lydia; Fernandez, M Isabel; Spikes, Pilgrim S; Flores, Stephen A

2014-11-01

HIV testing behavior is important in understanding the high rates of undiagnosed infection among Hispanic/Latino men who have sex with men (MSM). Correlates of repeat/recent testing (within the past year and ≥5 tests during lifetime) and test avoidance (never or >5 years earlier) were examined among 608 sexually active Hispanic/Latino MSM (Miami-Dade County and New York City). Those who reported repeat/recent testing were more likely to have incomes over $30,000, speak English predominately, and have visited and disclosed same-sex behavior to a health care provider (HCP) in the past year. Those who were classified as test avoiders were less likely to have incomes over $10,000 and to have seen an HCP in the past year. The main reason for not testing (in both groups) was fear of HIV positivity; however, twice as many test avoiders considered this their main reason, and more test avoiders had confidentiality concerns. Results suggest that messages to encourage testing among Hispanic/Latino MSM may be most effective if past testing patterns and reasons for not testing are considered. HCPs can play an important role by consistently offering HIV tests to MSM and tailoring messages based on prior testing histories. © 2014 Society for Public Health Education.

Influence of nano-dispersive modified additive on cement activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sazonova, Natalya, E-mail: n.a.sazonova@mail.ru; Badenikov, Artem, E-mail: rector@agta.ru; Ivanova, Elizaveta, E-mail: lisik-iva@mail.ru

2016-01-15

In the work the influence of single-walled carbon nanotubes (SWCNT) on the cement activity and the processes of structure formation of the hardened cement paste in different periods of hydration are studied. The changes in the kinetic curves of the sample strength growth modified with SWCNT in amount of 0.01 and 0.0005 % are stipulated by the results of differential scanning colorimetry, scanning electronic and ionic microscopy, X-ray-phase analysis. It was found that the nano-modified additive may increase in the axis compressive strength of the system by 1.4–6.3 fold relatively to the reference samples and may reach 179.6 MPa. It maymore » intensify the hydration process of calcium silicates as well as influence on the matrix of hardened cement paste. The studies are conducted on the structural changes in the hardened cement paste, the time periods of increase and decrease of the compressive strength of the samples, the amount of the calcium hydroxide and tobermorite-like gel as well as the degree of hydration C{sub 3}S and β-C{sub 2}S.« less

Modeling Framework for Fracture in Multiscale Cement-Based Material Structures

PubMed Central

Qian, Zhiwei; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

2017-01-01

Multiscale modeling for cement-based materials, such as concrete, is a relatively young subject, but there are already a number of different approaches to study different aspects of these classical materials. In this paper, the parameter-passing multiscale modeling scheme is established and applied to address the multiscale modeling problem for the integrated system of cement paste, mortar, and concrete. The block-by-block technique is employed to solve the length scale overlap challenge between the mortar level (0.1–10 mm) and the concrete level (1–40 mm). The microstructures of cement paste are simulated by the HYMOSTRUC3D model, and the material structures of mortar and concrete are simulated by the Anm material model. Afterwards the 3D lattice fracture model is used to evaluate their mechanical performance by simulating a uniaxial tensile test. The simulated output properties at a lower scale are passed to the next higher scale to serve as input local properties. A three-level multiscale lattice fracture analysis is demonstrated, including cement paste at the micrometer scale, mortar at the millimeter scale, and concrete at centimeter scale. PMID:28772948

Bone Repair and Military Readiness

DTIC Science & Technology

2015-10-01

Even though commercial bone cements have not significantly changed in the past 50 years and have been used throughout the world, there are...generation. In addition, it appears that this new bone cement is actually supportive of new bone formation. A cement that can achieve true integration...problem. As the proposed bone cement prototype polymerizes at a much lower temperature, antibiotics that are sensitive to heat can be added to the cement

Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cwirzen, Andrzej; Penttala, Vesa

2005-04-01

The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing andmore » thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ.« less

Elaborating the History of Our Cementing Societies: An in-Use Stock Perspective.

PubMed

Cao, Zhi; Shen, Lei; Løvik, Amund N; Müller, Daniel B; Liu, Gang

2017-10-03

Modern cities and societies are built fundamentally based on cement and concrete. The global cement production has risen sharply in the past decades due largely to urbanization and construction. Here we deployed a top-down dynamic material flow analysis (MFA) model to quantify the historical development of cement in-use stocks in residential, nonresidential, and civil engineering sectors of all world countries. We found that global cement production spreads unevenly among 184 countries, with China dominating the global production and consumption after the 1990s. Nearly all countries have shown an increasing trend of per capita cement in-use stock in the past century. The present per capita cement in-use stocks vary from 10 to 40 tonnes in major industrialized and transiting countries and are below 10 tonnes in developing countries. Evolutionary modes identified from historical patterns suggest that per capita in-use cement stock growth generally complies with an S-shape curve and relates closely to affluence and urbanization of a country, but more in-depth and bottom-up investigations are needed to better understand socioeconomic drivers behind stock growth. These identified in-use stock patterns can help us better estimate future demand of cement, explore strategies for emissions reduction in the cement industry, and inform CO 2 uptake potentials of cement based products and infrastructure in service.

Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration

NASA Astrophysics Data System (ADS)

Wei, Jie; Wang, Jiecheng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

2011-06-01

Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H 3PO 4) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3 wt% after self-hardening for 2 days. The solubility of fs-AC in Tris-HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.

Interactions between chloride and cement-paste materials.

PubMed

Barberon, Fabien; Baroghel-Bouny, Véronique; Zanni, Hélène; Bresson, Bruno; d'Espinose de la Caillerie, Jean-Baptiste; Malosse, Lucie; Gan, Zehong

2005-02-01

The durability of cement-based materials with respect to exterior aggressions is one of the current priorities in civil engineering. Depending on their use, the cement-based materials can be exposed to different types of aggressive environments. For instance, damages to concrete structures in contact with a saline environment (sea water on bridges, deicing salts on roads, etc.) are of utmost importance. Upon exposure to saline water, Cl- ions penetrate into the structures and subsequently lead to reinforcement corrosion. Chloride attack is often combined with other aggressive influences such as temperature (e.g., freezing) or the ingress of other ions (e.g., sulfates in sea water). We therefore aim to explore the effect of sodium chloride (NaCl) on the structural chemistry of cement paste. Existing studies about reinforcement corrosion by chloride have focused on the penetration of Cl- ions and the comparison between "free" ions (water-soluble ions) and bound ones. However, little is known about the fixation mechanisms, the localization of Cl in the cement matrix and the structural interaction between Cl and the silicate and aluminate hydrate phases present in cement paste. We present here results of a multinuclear nuclear magnetic resonance study on the fixation of chloride in the hydration products and the characterization of new phases potentially appearing due to chloride ingress.

Improving patient outcomes by pooling resources (the Texas Heart Care Partnership experience).

PubMed

Hillert, B; Remonte, S; Rodgers, G; Yancy, C W; Kaul, A F

2000-02-10

The morbidity and mortality associated with cardiovascular disease presents an enormous humanistic and economic burden in the United States. In Texas, cardiovascular disease has been the leading cause of death since 1950. Risk-factor modification has been targeted in the secondary prevention of cardiovascular disease, including lipid management, smoking cessation, improved control of blood pressure, physical activity, weight management, the use of antiplatelet agents/anticoagulants, angiotensin-converting enzyme (ACE) inhibitors in congestive heart failure, beta blockers after myocardial infarction, and estrogen replacement therapy. The Heart Care Partnership (HCP) is a multifaceted interactive program designed to improve risk-factor management in the secondary prevention of cardiovascular disease through physician education, participation, and consensus development in addition to practice improvement processes and patient education. Development and implementation of the Texas HCP was a joint effort of the Texas Medical Association, the Texas Affiliate of the American Heart Association, and Merck & Co. This program helps hospitals improve the quality of care and outcomes for patients with heart disease. Program resources include educational workshops, quality improvement processes, and patient educational materials. HCP workshops address the treatment gap, define optimal care, and help define institution-specific plans for treating heart disease. Quality-improvement processes provide hospitals with baseline data and tools to improve and measure outcomes over time. The HCP workshops are provided as a combination of lectures, interactive discussions, and small group planning sessions designed to encourage audience participation. Upon completing the HCP program, participants are able to (1) describe the evidence-based medicine supporting secondary prevention of cardiovascular disease; (2) identify and prioritize cardiovascular disease risk factors for secondary prevention; (3) identify barriers to and solutions for implementing secondary prevention; and (4) develop site-based plans for cardiovascular risk-factor modification with definite time lines for implementation ("care maps"). The HCP's initial audit of medical practices indicates that Texas appears to share the same deficiencies in the secondary prevention of cardiovascular disease as the rest of the country. However, improvements can be demonstrated in both the hospital and physician office settings through the HCP. The HCP facilitated the cooperation of the medical community in the state of Texas to work together in a synchronized, communicative manner to decrease coronary events. This partnership represents a watershed event in the history of Texas medicine. It is the first time that such a statewide team approach to address a public health issue has been initiated. In the past, medical organizations within the state have had disparate goals and multiple strategies for achieving them.

Changes of strength characteristics of pervious concrete due to variations in water to cement ratio

NASA Astrophysics Data System (ADS)

Kovac, M.; Sicakova, A.

2017-10-01

Pervious concrete is considered to be a sustainable pavement material due to high water permeability. The experiment presented in this paper was aimed at study the influence of water to cement ratio on both the compressive and splitting tensile strength of pervious concrete. Typically, less water content in concrete mixture leads to less porosity of cement paste and thus it provides desirable mechanical properties. In case of conventional dense concrete, the lower is the water to cement ratio, the higher or better is the strength, density and durability of concrete. This behaviour is not quite clear in case of pervious concrete because of low amount of cement paste present. Results of compressive and splitting tensile strength of pervious concrete are discussed in the paper while taking into account values measured after 2 and 28 days of hardening and variations in water to cement ratio. The results showed that changes of water to cement ratio from 0.25 to 0.35 caused only slight differences in strength characteristics, and this applied to both types of tested strength.

Failure of cement hydrates: freeze-thaw and fracture

NASA Astrophysics Data System (ADS)

Ioannidou, Katerina; Del Gado, Emanuela; Ulm, Franz-Josef; Pellenq, Roland

Mechanical and viscoelastic behavior of concrete crucially depends on cement hydrates, the ``glue'' of cement. Even more than the atomistic structure, the mesoscale amorphous texture of cement hydrates over hundreds of nanometers plays a crucial role for material properties. We use simulations that combine information of the nano-scale building units of cement hydrates and on their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles.Our mesoscale model was able to reconcile different experimental results ranging from small-angle neutron scattering, SEM, adsorption/desorption of N2, and water to nanoindentation and gain the new fundamental insights into the microscopic origin of the properties measured. Our results suggest that heterogeneities developed during the early stages of hydration persist in the structure of C-S-H, impacting the rheological and mechanical performance of the hardened cement paste. In this talk I discuss recent investigation on failure mechanism at the mesoscale of hardened cement paste such as freeze-thaw and fracture. Using correlations between local volume fractions and local stress we provide a link between structural and mechanical heterogeneities during the failure mechanisms.

Assessment the potential of using Carbon nanotubes reinforcements for improving the tensile/flexural strength and fracture toughness of Portland cement paste for damage resistant concrete transportation infrastructures.

DOT National Transportation Integrated Search

2010-09-01

The focus of this study was on exploring the use of nanotechnology-based nano-filaments, such as carbon : nanotubes (CNTs) and nanofibers (CNFs), as reinforcement in improving the mechanical properties of Portland : cement paste as a construction mat...

A New Biphasic Dicalcium Silicate Bone Cement Implant.

PubMed

Zuleta, Fausto; Murciano, Angel; Gehrke, Sergio A; Maté-Sánchez de Val, José E; Calvo-Guirado, José L; De Aza, Piedad N

2017-07-06

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C₂S) cement. Biphasic α´ L + β-C₂S ss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C₂S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement's surface after soaking in SBF. The cell attachment test showed that α´ L + β-C₂S ss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

Characterization and modeling of the rheology of cement paste: With applications toward self-flowing materials

NASA Astrophysics Data System (ADS)

Saak, Aaron Wilbur

The objective of this research is to better understand the important mechanisms that control the rheology of cement paste. In order to understand these mechanisms, new experimental techniques are developed. The insights gained through these studies are then applied toward designing self-flowing materials, particularly self-compacting concrete (SCC). A new testing program is developed where both the peak and equilibrium stress flow curves of cement paste are obtained by testing only one sample. Additionally, the influence of wall slip on yield stress and viscoelastic measurements is determined using a vane. The results indicate that a slip layer develops when the shear stress approaches the yield point. A three-dimensional model relating slump to yield stress is derived as a function of cone geometry. The results indicate that the model fits experimental data for cylindrical slumps over a wide range of yield stress values for a variety of materials. When compared to other published models, the results suggest that a fundamental relationship exists between yield stress and slump that is material independent and largely independent of cone geometry. The affect of various mixing techniques on the rheology of cement paste is investigated using a rheometer as a highly controlled mixer. The results suggest that there is a characteristic shear rate where the viscosity of cement paste is minimized. The influence of particle packing density, morphology and surface area on the viscosity of cement paste is quantified. The data suggest that even though packing density increases with the addition of fine particles, the benefits are largely overshadowed by a dramatic increase in surface area. Finally, a new methodology is introduced for designing self-compacting concrete. This approach incorporates a "self-flow zone" where the rheology of the paste matrix provides high workability, yet segregation resistance. The flow properties of fresh concrete are measured using a U-tube apparatus to test the general applicability of the proposed methodology. Using the new design approach, concrete with a slump of 29 cm (11 inches) and slump flow diameter of 60.9 cm (24 inches) is produced.

Retardation effect of different alcohols on the cement coagulation in polycarboxylate- and naphthalene-based cement admixtures

NASA Astrophysics Data System (ADS)

Huang, S. M.; Zhou, F. L.

2017-12-01

Alcohol has great potential to delay the coagulation of cement. The effects of alcohol on paste fluidity and normal consistency coagulation time have been studied for polycarboxylate superplasticizer and naphthene cement admixture. Seven alcohols were combined with polycarboxylate superplasticizer and naphthene at a concentration of 0.01-0.09%, respectively, including n-propanol, methanol, sorbitol, ethylene glycol, glycerol, ethanol, and mannitol. The fluidity and normal consistency coagulation time of each cement admixture were measured. The performance of both polycarboxylate superplasticizer and naphthene cement admixtures were compared to develop cement admixture with delayed coagulation.

Characterizing the Nano and Micro Structure of Concrete toImprove its Durability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, P.J.M.; Kirchheim, A.P.; Chae, S.

2009-01-13

New and advanced methodologies have been developed to characterize the nano and microstructure of cement paste and concrete exposed to aggressive environments. High resolution full-field soft X-ray imaging in the water window is providing new insight on the nano scale of the cement hydration process, which leads to a nano-optimization of cement-based systems. Hard X-ray microtomography images of ice inside cement paste and cracking caused by the alkali?silica reaction (ASR) enables three-dimensional structural identification. The potential of neutron diffraction to determine reactive aggregates by measuring their residual strains and preferred orientation is studied. Results of experiments using these tools aremore » shown on this paper.« less

Characterizing the nano and micro structure of concrete to improve its durability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, P.J.M.; Kirchheim, A.P.; Chae, S.

2008-10-22

New and advanced methodologies have been developed to characterize the nano and microstructure of cement paste and concrete exposed to aggressive environments. High resolution full-field soft X-ray imaging in the water window is providing new insight on the nano scale of the cement hydration process, which leads to a nano-optimization of cement-based systems. Hard X-ray microtomography images on ice inside cement paste and cracking caused by the alkali-silica reaction (ASR) enables three-dimensional structural identification. The potential of neutron diffraction to determine reactive aggregates by measuring their residual strains and preferred orientation is studied. Results of experiments using these tools willmore » be shown on this paper.« less

The effects of different types of nano-silicon dioxide additives on the properties of sludge ash mortar.

PubMed

Luo, Huan-Lin; Chang, Wei-Che; Lin, Deng-Fong

2009-04-01

To improve the drawbacks caused by the sludge ash replacement in mortar, the previous studies have shown that the early strength and durability of sludge ash/cement mortar are improved by adding nano-silicon dioxide (nano-SiO2) to mortar. In this article, three types of nano-SiO2--SS, HS, and SP (manufacturer code names)--were applied to sludge ash/cement mixture to make paste or mortar specimens. The object is to further extend the recycle of the sludge ash by determining the better type of nano-SiO2 additive to improve properties of sludge ash/ cement paste or mortar. The cement was replaced by 0, 10, 20, and 30% of sludge ash, and 0 and 2% of nano-SiO2 additives were added to the sludge ash paste or mortar specimens. Tests such as setting time, compressive strength, scanning electron microscopy, X-ray diffraction, nuclear magnetic resonance, and thermogravimetric analysis/differential thermal analysis were performed in this study. Test results show that nano-SiO2 additives can not only effectively increase the hydration product (calcium silicate hydrate [C-S-H] gel), but also make the crystal structure denser. Among the three types of nano-SiO2 additive, the SS type can best improve the properties of sludge ash/cement paste or mortar, followed by the SP and HS types.

Microstructural Properties of Cement Paste and Mortar Modified by Low Cost Nanoplatelets Sourced from Natural Materials.

PubMed

Huang, Piao; Lv, Liming; Liao, Wei; Lu, Chunhua; Xu, Zhongzi

2018-05-11

Nanomaterials have been widely used in cement-based materials. Graphene has excellent properties for improving the durability of cement-based materials. Given its high production budget, it has limited its wide potential for application in the field of engineering. Hence, it is very meaningful to obtain low cost nanoplatelets from natural materials that can replace graphene nanoplatelets (GNPs) The purpose of this paper is to improve the resistance to chloride ion penetration by optimizing the pore structure of cement-based materials, and another point is to reduce investment costs. The results illustrated that low cost CaCO₃ nanoplatelets (CCNPs) were successfully obtained under alkali treatment of seashell powder, and the chloride ion permeability of cement-based materials significantly decreased by 15.7% compared to that of the control samples when CCNPs were incorporated. Furthermore, the compressive strength of cement pastes at the age of 28 days increased by 37.9% than that of the plain sample. Improvement of performance of cement-based materials can be partly attributed to the refinement of the pore structure. In addition, AFM was employed to characterize the nanoplatelet thickness of CCNPs and the pore structures of the cement-based composites were analyzed by MIP, respectively. CCNPs composite cement best performance could lay the foundation for further study of the durability of cement-based materials and the application of decontaminated seashells.

Microstructural Properties of Cement Paste and Mortar Modified by Low Cost Nanoplatelets Sourced from Natural Materials

PubMed Central

Lv, Liming; Liao, Wei; Lu, Chunhua; Xu, Zhongzi

2018-01-01

Nanomaterials have been widely used in cement-based materials. Graphene has excellent properties for improving the durability of cement-based materials. Given its high production budget, it has limited its wide potential for application in the field of engineering. Hence, it is very meaningful to obtain low cost nanoplatelets from natural materials that can replace graphene nanoplatelets (GNPs) The purpose of this paper is to improve the resistance to chloride ion penetration by optimizing the pore structure of cement-based materials, and another point is to reduce investment costs. The results illustrated that low cost CaCO3 nanoplatelets (CCNPs) were successfully obtained under alkali treatment of seashell powder, and the chloride ion permeability of cement-based materials significantly decreased by 15.7% compared to that of the control samples when CCNPs were incorporated. Furthermore, the compressive strength of cement pastes at the age of 28 days increased by 37.9% than that of the plain sample. Improvement of performance of cement-based materials can be partly attributed to the refinement of the pore structure. In addition, AFM was employed to characterize the nanoplatelet thickness of CCNPs and the pore structures of the cement-based composites were analyzed by MIP, respectively. CCNPs composite cement best performance could lay the foundation for further study of the durability of cement-based materials and the application of decontaminated seashells. PMID:29751666

Comparative Epidemiology of Human Infections with Middle East Respiratory Syndrome and Severe Acute Respiratory Syndrome Coronaviruses among Healthcare Personnel

PubMed Central

Chu, Yu-Tseng; Wu, Joseph Tsung-Shu; Geng, Xingyi; Zhao, Na; Cheng, Wei; Chen, Enfu; King, Chwan-Chuen

2016-01-01

The largest nosocomial outbreak of Middle East respiratory syndrome (MERS) occurred in South Korea in 2015. Health Care Personnel (HCP) are at high risk of acquiring MERS-Coronavirus (MERS-CoV) infections, similar to the severe acute respiratory syndrome (SARS)-Coronavirus (SARS-CoV) infections first identified in 2003. This study described the similarities and differences in epidemiological and clinical characteristics of 183 confirmed global MERS cases and 98 SARS cases in Taiwan associated with HCP. The epidemiological findings showed that the mean age of MERS-HCP and total MERS cases were 40 (24~74) and 49 (2~90) years, respectively, much older than those in SARS [SARS-HCP: 35 (21~68) years, p = 0.006; total SARS: 42 (0~94) years, p = 0.0002]. The case fatality rates (CFR) was much lower in MERS-HCP [7.03% (9/128)] or SARS-HCP [12.24% (12/98)] than the MERS-non-HCP [36.96% (34/92), p<0.001] or SARS-non-HCP [24.50% (61/249), p<0.001], however, no difference was found between MERS-HCP and SARS-HCP [p = 0.181]. In terms of clinical period, the days from onset to death [13 (4~17) vs 14.5 (0~52), p = 0.045] and to discharge [11 (5~24) vs 24 (0~74), p = 0.010] and be hospitalized days [9.5 (3~22) vs 22 (0~69), p = 0.040] were much shorter in MERS-HCP than SARS-HCP. Similarly, days from onset to confirmation were shorter in MERS-HCP than MERS-non-HCP [6 (1~14) vs 10 (1~21), p = 0.044]. In conclusion, the severity of MERS-HCP and SARS-HCP was lower than that of MERS-non-HCP and SARS-non-HCP due to younger age and early confirmation in HCP groups. However, no statistical difference was found in MERS-HCP and SARS-HCP. Thus, prevention of nosocomial infections involving both novel Coronavirus is crucially important to protect HCP. PMID:26930074

Factors associated with the intention of health care personnel to respond to a disaster.

PubMed

Connor, Susan B

2014-12-01

Over the past decade, numerous groups of researchers have studied the willingness of health care personnel (HCP) to respond when a disaster threatens the health of a community. Not one of those studies reported that 100% of HCP were willing to work during a public-health event (PHE). The objective of this study was to explore factors associated with the intent of HCP to respond to a future PHE. The theory of planned behavior (TPB) framed this cross-sectional study. Data were obtained via a web-based survey from 305 HCP. Linear associations between the TPB-based predictor and outcome variables were examined using Pearson's correlations. Differences between two groups of HCP were calculated using independent t tests. A model-generating approach was used to develop and assess a series of TBP-based observed variable structural equation models for prediction of intent to respond to a future PHE and to explore moderating and mediating effects. The beginning patterns of relationships identified by the correlation matrix and t tests were evident in the final structural equation model, even though the patterns of prediction differed from those posited by the theory. Outcome beliefs had both a significant, direct effect on intention and an indirect effect on intention that was mediated by perceived behavioral control. Control beliefs appeared to influence intention through perceived behavioral control, as posited by the TPB, and unexpectedly through subjective norm. Subjective norm not only mediated the relationship between control beliefs and intention, but also the relationship between referent beliefs and intention. Additionally, professional affiliation seemed to have a moderating effect on intention. The intention to respond was influenced primarily by normative and control factors. The intent of nurses to respond to a future PHE was influenced most by the control factors, whereas the intent of other HCP was shaped more by the normative factors. Health care educators can bolster the normative and control factors through education by focusing on team building and knowledge related to accessing supplies and support needed to respond when a disaster occurs.

Early-age monitoring of cement structures using FBG sensors

NASA Astrophysics Data System (ADS)

Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

2006-03-01

With more and more broad applications of the cement-based structures such as neat cement paste, cement mortar and concrete in civil engineering, people hope to find out what their performances should like. The in-service performances of cement-based structures are highly affected by their hardening process during the early-age. But it is still a big problem for traditional sensors to be used to monitor the early curing of cement-based structures due to such disadvantages as difficulties to install sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave and so on. In this paper, according to the sensing properties of the Fiber Bragg Grating sensors and self-characters of the cement-based structures, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete structures and negative concrete, respectively. Three types of FBG-based sensors have been developed to monitor the cement-based structures. Besides, the installation techniques and the embedding requirements of FBG sensors in cement-based structures are also discussed. Moreover, such kind of technique has been used in practical structure, 3rd Nanjing Yangtze Bridge, and the results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and so on inside different cement-based structures. This technique provides us a new useful measuring method on early curing monitoring of cement-based structures and greater understanding of details of their hardening process.

SCM Paste Samples Exposed To Aggressive Solutions. Cementitious Barriers Partnership

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foster, T.

This report summarizes experimental work performed by SIMCO Technologies Inc. (SIMCO) as part of the Cementitious Barriers Partnership (CBP) project. The test series followed an experimental program dedicated to the study of ordinary Portland cement (OPC) hydrated cement pastes exposed to aggressive solutions. In the present study, the scope is extended to hydrated cement pastes incorporating supplementary cementitious materials (SCM) such as fly ash and ground granulated blast furnace slag (GGBFS). Also, the range of aggressive contact solutions was expanded. The experimental program aimed at testing aggressive contact solutions that more closely mimic the chemical composition of saltstone pore solution.more » Five different solutions, some of which incorporated high levels of carbonate and nitrate, were placed in contact with four different hydrated cement paste mixes. In all solutions, 150 mmol/L of SO 4 2– (14 400 ppm) were present. The solutions included different pH conditions and different sodium content. Two paste mixes were equivalent to Vault 1/4 and Vault 2 concrete mixes used at SRS in storage structures. Two additional paste mixes, cast at the same water-to-cement ratio and using the same cements but without SCMs, were also tested. The damage evolution in samples was monitored using ultrasonic pulse velocity (UPV) and mass measurements. After three and twelve months of exposure conditions, samples were taken out of solution containers and analyzed to perform migration tests and porosity measurements. Globally, results were in line with the previous study and confirmed that high pH may limit the formation of some deleterious phases like gypsum. In this case, ettringite may form but is not necessarily associated with damage. However, the high concentration of sodium may be associated with the formation of an AFm-like mineral called U-phase. The most significant evidences of damage were all associated with the Vault 2 paste analog. This material proved very sensitive to high pH. All measurement techniques used to monitor and evaluate damage to samples indicated significant alterations to this mix when immersed in contact solutions containing sodium hydroxide. It was hypothesized that the low cement content, combined with high silica content coming from silica fume, fly ash and GGBFS led to the presence unreacted silica. It is possible that the pozzolanic reaction of these SCMs could not be activated due to the low alkali content, a direct consequence of low cement content. In this scenario, the material end up having a lot of silica available to react upon contact with sodium hydroxide, possibly forming a gel that may be similar to the gel formed in alkali-silica reactions. This scenario needs further experimental confirmation, but it may well explain the poor behavior of mix PV2 in presence of NaOH.« less

A New Biphasic Dicalcium Silicate Bone Cement Implant

PubMed Central

Murciano, Angel; Maté-Sánchez de Val, José E.

2017-01-01

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C2S) cement. Biphasic α´L + β-C2Sss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C2S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement’s surface after soaking in SBF. The cell attachment test showed that α´L + β-C2Sss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration. PMID:28773119

Effect of Admixtures on the Yield Stresses of Cement Pastes under High Hydrostatic Pressures

PubMed Central

Yim, Hong Jae; Kim, Jae Hong; Kwon, Seung Hee

2016-01-01

When cement-based materials are transported at a construction site, they undergo high pressures during the pumping process. The rheological properties of the materials under such high pressures are unknown, and estimating the workability of the materials after pumping is a complex problem. Among various influential factors on the rheology of concrete, this study investigated the effect of mineral and chemical admixtures on the high-pressure rheology. A rheometer was fabricated that could measure the rheological properties while maintaining a high pressure to simulate the pumping process. The effects of superplasticizer, silica fume, nanoclay, fly ash, or ground granulated blast furnace slag were investigated when mixed with two control cement pastes. The water-to-cement ratios were 0.35 and 0.50. PMID:28773273

Temperature dependence of autogenous shrinkage of silica fume cement pastes with a very low water–binder ratio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maruyama, I., E-mail: ippei@dali.nuac.nagoya-u.ac.jp; Teramoto, A.

Ultra-high-strength concrete with a large unit cement content undergoes considerable temperature increase inside members due to hydration heat, leading to a higher risk of internal cracking. Hence, the temperature dependence of autogenous shrinkage of cement pastes made with silica fume premixed cement with a water–binder ratio of 0.15 was studied extensively. Development of autogenous shrinkage showed different behaviors before and after the inflection point, and dependence on the temperature after mixing and subsequent temperature histories. The difference in autogenous shrinkage behavior poses problems for winter construction because autogenous shrinkage may increase with decrease in temperature after mixing before the inflectionmore » point and with increase in temperature inside concrete members with large cross sections.« less

Assessment of Pb-slag, MSWI bottom ash and boiler and fly ash for using as a fine aggregate in cement mortar.

PubMed

Saikia, Nabajyoti; Cornelis, Geert; Mertens, Gilles; Elsen, Jan; Van Balen, Koenraad; Van Gerven, Tom; Vandecasteele, Carlo

2008-06-15

Three types of wastes, metallurgical slag from Pb production (SLG), the sand-sized (0.1-2 mm) fraction of MSWI bottom ash from a grate furnace (SF), and boiler and fly ash from a fluidised bed incinerator (BFA), were characterized and used to replace the fine aggregate during preparation of cement mortar. The chemical and mineralogical behaviour of these wastes along with the reactivities of the wastes with lime and the hydration behaviour of ordinary Portland cement paste with and without these wastes added were evaluated by various chemical and instrumental techniques. The compressive strengths of the cement mortars containing waste as a partial substitution of fine aggregates were also assessed. Finally, leaching studies of the wastes and waste containing cement mortars were conducted. SLG addition does not show any adverse affect during the hydration of cement, or on the compressive strengths behaviours of mortars. Formation of expansive products like ettringite, aluminium hydroxide and H2 gas due to the reaction of some constituents of BFA and SF with alkali creates some cracks in the paste as well as in the cement mortars, which lower the compressive strength of the cement mortars. However, utilization of all materials in cement-based application significantly improves the leaching behaviour of the majority of the toxic elements compared to the waste as such.

Spectroscopic investigation of Ni speciation in hardened cement paste.

PubMed

Vespa, M; Dähn, R; Grolimund, D; Wieland, E; Scheidegger, A M

2006-04-01

Cement-based materials play an important role in multi-barrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. Cement is used to condition and stabilize the waste materials and to construct the engineered barrier systems (container, backfill, and liner materials) of repositories for radioactive waste. In this study, Ni uptake by hardened cement paste has been investigated with the aim of improving our understanding of the immobilization process of heavy metals in cement on the molecular level. X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance spectroscopy (DRS) techniques were used to determine the local environment of Ni in cement systems. The Ni-doped samples were prepared at two different water/cement ratios (0.4, 1.3) and different hydration times (1 hour to 1 year) using a sulfate-resisting Portland cement. The metal loadings and the metal salts added to the system were varied (50 up to 5000 mg/kg; NO3(-), SO4(2-), Cl-). The XAS study showed that for all investigated systems Ni(ll) is predominantly immobilized in a layered double hydroxide (LDH) phase, which was corroborated by DRS measurements. Only a minor extent of Ni(ll) precipitates as Ni-hydroxides (alpha-Ni(OH)2 and beta-Ni(OH)2). This finding suggests that Ni-Al LDH, rather than Ni-hydroxides, is the solubility-limiting phase in the Ni-doped cement system.

The effect of ageing and heat treatment on microstructure evolution of a commercial cement paste

NASA Astrophysics Data System (ADS)

Sabeur, Hassen; Platret, Gérard; Vincent, Julien

2017-08-01

This paper reports the microstructural changes on a 2 year-old cement paste, unprotected from contact with air, heated to various temperature regimes up to 1000 °C in steps of 100 °C for a constant period of 6 h. This work has been carried out using a thermal analysis technique and XRD. The parameter involved in this study is the state of the samples: powdered samples and blocks of paste. As a result, it is possible to monitor the major features of the experiments, i.e. the phase's existence domains and their growing of hydrated calcium silicate, portlandite, calcite as well as their decaying: alite, belite and lime. The result shows higher amounts of portlandite and carbonate calcium for the aged cement paste compared to fresh OPC. The carbonation is more marked for the blocks of paste while the crystallinity degree is higher for the powdered cement paste samples. The new portlandite formed during cooling continues to exist until the 1000 °C temperature plateau. Nevertheless, this portlandite is less crystalline than the original one, and its temperature of thermal decomposition gets lower. An increase in the total weight loss and in the crystallinity at 900 and 1000 °C, compared to 800 °C is also noted. The CSH dehydration to β-C2S and C3S become significant above 600 °C and the corresponding rate increases with increasing temperature.

Polymeric additives to enhance the functional properties of calcium phosphate cements

PubMed Central

Perez, Roman A; Kim, Hae-Won

2012-01-01

The vast majority of materials used in bone tissue engineering and regenerative medicine are based on calcium phosphates due to their similarity with the mineral phase of natural bone. Among them, calcium phosphate cements, which are composed of a powder and a liquid that are mixed to obtain a moldable paste, are widely used. These calcium phosphate cement pastes can be injected using minimally invasive surgery and adapt to the shape of the defect, resulting in an entangled network of calcium phosphate crystals. Adding an organic phase to the calcium phosphate cement formulation is a very powerful strategy to enhance some of the properties of these materials. Adding some water-soluble biocompatible polymers in the calcium phosphate cement liquid or powder phase improves physicochemical and mechanical properties, such as injectability, cohesion, and toughness. Moreover, adding specific polymers can enhance the biological response and the resorption rate of the material. The goal of this study is to overview the most relevant advances in this field, focusing on the different types of polymers that have been used to enhance specific calcium phosphate cement properties. PMID:22511991

Study of the Microstructure Evolution of Low-pH Cements Based on Ordinary Portland Cement (OPC) by Mid- and Near-Infrared Spectroscopy, and Their Influence on Corrosion of Steel Reinforcement.

PubMed

García Calvo, José Luis; Sánchez Moreno, Mercedes; Alonso Alonso, María Cruz; Hidalgo López, Ana; García Olmo, Juan

2013-06-18

Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC), high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure evolution of low-pH cement pastes based on OPC plus silica fume and/or fly ashes, using Mid-Infrared and Near-Infrared spectroscopy to detect cement pastes mainly composed of high polymerized C-A-S-H gels with low C/S ratios. In addition, the lower pore solution pH of these special cementitious materials have been monitored with embedded metallic sensors. Besides, as the use of reinforced concrete can be required in underground repositories, the influence of low-pH cementitious materials on steel reinforcement corrosion was analysed. Due to their lower pore solution pH and their different pore solution chemical composition a clear influence on steel reinforcement corrosion was detected.

Strength and durability of concrete: Effects of cement paste-aggregate interfaces. Part 1: Theoretical study on influence of interfacial transition zone on properties of concrete materials; Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y.; Chen, W.F.

1998-08-01

This research was based on a two-part basic research investigation studying the effects of cement paste-aggregate interfaces (or interfacial transition zones-ITZ) on strength and durability of concrete. Part 1 dealt with the theoretical study and Part 2 dealt with the experimental.

Investigating the Influence of Waste Basalt Powder on Selected Properties of Cement Paste and Mortar

NASA Astrophysics Data System (ADS)

Dobiszewska, Magdalena; Beycioğlu, Ahmet

2017-10-01

Concrete is the most widely used man-made construction material in civil engineering applications. The consumption of cement and thus concrete, increases day by day along with the growth of urbanization and industrialization and due to new developments in construction technologies, population growing, increasing of living standard. Concrete production consumes much energy and large amounts of natural resources. It causes environmental, energy and economic losses. The most important material in concrete production is cement. Cement industry contributes to production of about 7% of all CO2 generated in the world. Every ton of cement production releases nearly one ton of CO2 to atmosphere. Thus the concrete and cement industry changes the environment appearance and influences it very much. Therefore, it has become very important for construction industry to focus on minimizing the environmental impact, reducing energy consumption and limiting CO2 emission. The need to meet these challenges has spurred an interest in the development of a blended Portland cement in which the amount of clinker is reduced and partially replaced with mineral additives - supplementary cementitious materials (SCMs). Many researchers have studied the possibility of using another mineral powder in mortar and concrete production. The addition of marble dust, basalt powder, granite or limestone powder positively affects some properties of cement mortar and concrete. This paper presents an experimental study on the properties of cement paste and mortar containing basalt powder. The basalt powder is a waste emerged from the preparation of aggregate used in asphalt mixture production. Previous studies have shown that analysed waste used as a fine aggregate replacement, has a beneficial effect on some properties of mortar and concrete, i.e. compressive strength, flexural strength and freeze resistance also. The present study shows the results of the research concerning the modification of cement paste and mortar with basalt powder. The modification consists in that the powder waste was added as partial replacement of cement. Four types of common cement were examined, i.e. CEM I, CEM II/A-S, CEM II/A-V and CEM II/B-V. The percentages of basalt powder in this research are 0%, 1%, 2%, 3%, 4%, 6%, 8% and 10% by mass. Results showed that the addition of basalt powder improved the strength of cement mortar. The use of mineral powder as the partial substitution of cement allows the effective management of industrial waste and improves some properties of cement mortar.

Hydrated Ordinary Portland Cement as a Carbonic Cement: The Mechanisms, Dynamics, and Implications of Self-Sealing and CO 2 Resistance in Wellbore Cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guthrie, George Drake Jr.; Pawar, Rajesh J.; Carey, James William

2017-07-28

This report analyzes the dynamics and mechanisms of the interactions of carbonated brine with hydrated Portland cement. The analysis is based on a recent set of comprehensive reactive-transport simulations, and it relies heavily on the synthesis of the body of work on wellbore integrity that we have conducted for the Carbon Storage Program over the past decade.

Formation of magnesium silicate hydrate (M-S-H) cement pastes using sodium hexametaphosphate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Tingting; Department of Materials, Centre for Advanced Structural Ceramics, Imperial College London, South Kensington Campus, London SW7 2AZ; Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ

2014-11-15

Magnesium silicate hydrate (M-S-H) gel is formed by the reaction of brucite with amorphous silica during sulphate attack in concrete and M-S-H is therefore regarded as having limited cementing properties. The aim of this work was to form M-S-H pastes, characterise the hydration reactions and assess the resulting properties. It is shown that M-S-H pastes can be prepared by reacting magnesium oxide (MgO) and silica fume (SF) at low water to solid ratio using sodium hexametaphosphate (NaHMP) as a dispersant. Characterisation of the hydration reactions by x-ray diffraction and thermogravimetric analysis shows that brucite and M-S-H gel are formed andmore » that for samples containing 60 wt.% SF and 40 wt.% MgO all of the brucites react with SF to form M-S-H gel. These M-S-H cement pastes were found to have compressive strengths in excess of 70 MPa.« less

Relating the Electrical Resistance of Fresh Concrete to Mixture Proportions.

PubMed

Obla, K; Hong, R; Sherman, S; Bentz, D P; Jones, S Z

2018-01-01

Characterization of fresh concrete is critical for assuring the quality of our nation's constructed infrastructure. While fresh concrete arriving at a job site in a ready-mixed concrete truck is typically characterized by measuring temperature, slump, unit weight, and air content, here the measurement of the electrical resistance of a freshly cast cylinder of concrete is investigated as a means of assessing mixture proportions, specifically cement and water contents. Both cement and water contents influence the measured electrical resistance of a sample of fresh concrete: the cement by producing ions (chiefly K + , Na + , and OH - ) that are the main source of electrical conduction; and the water by providing the main conductive pathways through which the current travels. Relating the measured electrical resistance to attributes of the mixture proportions, such as water-cement ratio by mass ( w/c ), is explored for a set of eleven different concrete mixtures prepared in the laboratory. In these mixtures, w/c , paste content, air content, fly ash content, high range water reducer dosage, and cement alkali content are all varied. Additionally, concrete electrical resistance data is supplemented by measuring the resistivity of its component pore solution obtained from 5 laboratory-prepared cement pastes with the same proportions as their corresponding concrete mixtures. Only measuring the concrete electrical resistance can provide a prediction of the mixture's paste content or the product w*c ; conversely, when pore solution resistivity is also available, w/c and water content of the concrete mixture can be reasonably assessed.

Relating the Electrical Resistance of Fresh Concrete to Mixture Proportions

PubMed Central

Obla, K.; Hong, R.; Sherman, S.; Bentz, D.P.; Jones, S.Z.

2018-01-01

Characterization of fresh concrete is critical for assuring the quality of our nation’s constructed infrastructure. While fresh concrete arriving at a job site in a ready-mixed concrete truck is typically characterized by measuring temperature, slump, unit weight, and air content, here the measurement of the electrical resistance of a freshly cast cylinder of concrete is investigated as a means of assessing mixture proportions, specifically cement and water contents. Both cement and water contents influence the measured electrical resistance of a sample of fresh concrete: the cement by producing ions (chiefly K+, Na+, and OH-) that are the main source of electrical conduction; and the water by providing the main conductive pathways through which the current travels. Relating the measured electrical resistance to attributes of the mixture proportions, such as water-cement ratio by mass (w/c), is explored for a set of eleven different concrete mixtures prepared in the laboratory. In these mixtures, w/c, paste content, air content, fly ash content, high range water reducer dosage, and cement alkali content are all varied. Additionally, concrete electrical resistance data is supplemented by measuring the resistivity of its component pore solution obtained from 5 laboratory-prepared cement pastes with the same proportions as their corresponding concrete mixtures. Only measuring the concrete electrical resistance can provide a prediction of the mixture’s paste content or the product w*c; conversely, when pore solution resistivity is also available, w/c and water content of the concrete mixture can be reasonably assessed. PMID:29882546

Analysis of Cement-Based Pastes Mixed with Waste Tire Rubber

NASA Astrophysics Data System (ADS)

Sola, O. C.; Ozyazgan, C.; Sayin, B.

2017-03-01

Using the methods of thermal gravimetry, differential thermal analysis, Furier transform infrared analysis, and capillary absorption, the properties of a cement composite produced by introducing waste tyre rubber into a cement mixture were investigated. It was found that the composite filled with the rubber had a much lower water absorption ability than the unfilled one.

Human parvovirus B19 nosocomial outbreak in healthcare personnel in a paediatric ward at a national tertiary referral centre in Thailand.

PubMed

Sungkate, S; Phongsamart, W; Rungmaitree, S; Lapphra, K; Wittawatmongkol, O; Pumsuwan, V; Wiruchkul, N; Assanasen, S; Rongrungruang, Y; Onlamoon, N; Horthongkham, N; Lermankul, W; Kongstan, N; Chokephaibulkit, K

2017-06-01

Nosocomial outbreaks of parvovirus B19 (pB19) have been reported, but they rarely occur among healthcare personnel (HCP). Susceptibility among pregnant HCP was the major concern. An outbreak of pB19 among HCP is described in a paediatric ward with a cross-sectional serologic study in all HCP and patients exposed to the outbreak. Acute infection was diagnosed by polymerase chain reaction or positive anti-parvovirus B19 IgM. Among 48 HCP (three pregnant) and 22 patients included in the outbreak serologic study, 11 (23%) HCP and two (9%) patients had acute infection. Of these, six HCP and no patients were symptomatic. Clinical manifestations included itchy rash (100%) and joint pain following resolution of rash (67%), with median rash duration of four days. Forty percent of HCP and 50% of patients had positive anti-parvovirus IgG, indicating previously immune status. HCP with acute infection and HCP who were susceptible without infection were younger than HCP with previous immunity (mean age 32.2 vs 40.5 years, respectively; P = 0.003). The attack rate was 38% among HCP and 18% among patients who were susceptible, respectively. The outbreak ended within two weeks following strict droplet precaution and segregation of symptomatic HCP. Parvovirus B19 infection may cause nosocomial outbreak with high attack rate among HCP. Outbreak control with droplet precaution was highly effective. Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Cements of doped calcium phosphates for bone implantation =

NASA Astrophysics Data System (ADS)

Pina, Sandra Cristina de Almeida

The main objective of this study was the development of cements based on calcium phosphates doped with Mg, Sr and Zn, for clinical applications. Powder synthesis was obtained through precipitation reactions, followed by heat treatment in order to obtain appropriate phases, alpha and beta-TCP. The cements were prepared through mixing the powders with different liquids, using citric acid as setting accelerator, and polyethyleneglycol and hydroxyl propylmethylcellulose as gelling agents. Brushite was the end product of the hydration reaction. Injectability and setting behaviour were accessed through rheological measurements, extrusion, calorimetric analysis, Vicat and Gilmore needles. Phase quantification and the structural refinement of powders and cements were determined through X-ray diffraction with Rietveld refinement, as well as, BET specific surface area and particle size analysis. Mechanical strengths of wet hardened cements were evaluated. The results obtained showed that the incorporation of ions into cements led to a significant improvement of their overall properties. Initial setting time increased in the presence of rheological modifiers due to their specific roles at the solid/liquid interface and with increasing L/P ratio. Acceptable workability pastes were obtained for L/P ratios in the range of 0.30-0.34 mL g-1. The cement pastes presented good injectability even under a maximum applied force of 100 N. Filter pressing effects were absent, and all cement pastes could be fully injected for LPR > 0.36 mL g-1. Isothermal calorimetry revealed that hydration reactions produce exothermic effects due to: (i) dissolution of the starting powders and formation of intermediate phases; and (ii) nucleation and growth of brushite crystals. The intensity of the exothermic effects depended on doping element, being stronger in the case of Sr. Wet compressive strength of the cement specimens (after immersion in PBS solution for 48 h) was in the range of values reported for trabecular bone (10-30 MPa). Cell cultures used to evaluate citotoxicity, bioactivity and biocompatibility of cements revealed no toxic effects. The biocompatibility in vivo and cements resorption were evaluated using a pig model through histological and histomorphometric studies of decalcified sections. The results show that the implanted cements are biocompatible and osteoconductive, without foreign body reaction. These properties make them good candidates for applications as bone substitutes. None

Post-irradiation hardening of dual-cured and light-cured resin cements through machinable ceramics.

PubMed

Yoshida, Keiichi; Atsuta, Mitsuru

2006-10-01

To evaluate the surface hardness (Knoop Hardness Number) of the thin layer in three light-cured and dual-cured resin cements irradiated through or not through 2.0 mm thick machinable ceramics. A piece of adhesive polyethylene tape with a circular hole was positioned on the surface of the ceramic plate to control the cement layer (approximately 50 microm). The cement paste was placed on the ceramic surface within the circle. The ceramic plate with resin cement paste was placed on a clear micro cover glass over a zirconia ceramic block to obtain a flat surface, and the material was polymerized using a visible-light-curing unit. The surface hardness was recorded at a series of time intervals up to 5 days, starting from the end of a light-irradiation period. The hardness steadily increased with post-irradiation time and tended towards a maximum, usually reached after 1 or 2 days. In all cases, the increase in hardness was relatively rapid over the first 30 minutes and continued at a lower rate thereafter. The dual-cured resin cement for each material showed a significantly higher hardness value than the light-cured resin cement irradiated either through or not through ceramics at all post-irradiation times. The resin cements cured through ceramic for each material were significantly less hard compared with those cured not through ceramics at all post-irradiation times.

Radon exhalation of hardening concrete: monitoring cement hydration and prediction of radon concentration in construction site.

PubMed

Kovler, Konstantin

2006-01-01

The unique properties of radon as a noble gas are used for monitoring cement hydration and microstructural transformations in cementitious system. It is found that the radon concentration curve for hydrating cement paste enclosed in the chamber increases from zero (more accurately - background) concentrations, similar to unhydrated cement. However, radon concentrations developed within 3 days in the test chamber containing cement paste were approximately 20 times higher than those of unhydrated cement. This fact proves the importance of microstructural transformations taking place in the process of cement hydration, in comparison with cement grain, which is a time-stable material. It is concluded that monitoring cement hydration by means of radon exhalation method makes it possible to distinguish between three main stages, which are readily seen in the time dependence of radon concentration: stage I (dormant period), stage II (setting and intensive microstructural transformations) and stage III (densification of the structure and drying). The information presented improves our understanding of the main physical mechanisms resulting in the characteristic behavior of radon exhalation in the course of cement hydration. The maximum value of radon exhalation rate observed, when cement sets, can reach 0.6 mBq kg(-1) s(-1) and sometimes exceeds 1.0 mBq kg(-1) s(-1). These values exceed significantly to those known before for cementitious materials. At the same time, the minimum ventilation rate accepted in the design practice (0.5 h(-1)), guarantees that the concentrations in most of the cases will not exceed the action level and that they are not of any radiological concern for construction workers employed in concreting in closed spaces.

Study of deformation of resin cements used in fixing of root posts through fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Pulido, C. A.; Franco, A. P. G. O.; Karam, L. Z.; Kalinowski, H. J.; Gomes, O. M. M.

2014-05-01

The aim of the study was to evaluate the polymerization shrinkage "in situ" in resin cements inside the root canal during the fixation of glass fiber posts. For cementation teeth were randomly divided into 2 groups according to the resin cement used: Group1 - resin cement dual Relyx ARC (3M/ESPE), and Group 2 - resin cement dual Relyx U200 (3M/ESPE). Before inserting the resin cement into the root canal, two Bragg grating sensors were recorded and pasted in the region without contact with the canal, one at the apical and other at the coronal thirds of the post. The sensors measured the deformation of the resin cements in coronal and apical root thirds to obtain the values in micro-strain (μɛ).

Can patients be 'attached' to healthcare providers? An observational study to measure attachment phenomena in patient-provider relationships.

PubMed

Maunder, Robert G; Hunter, Jonathan J

2016-05-13

To develop and assess the validity of measures of patients' attachment-related perceptions of experiences with healthcare providers (HCPs). Online survey. 181 people provided consent and 119 completed the survey (66%). Most participants were women (80%). Questions were developed to assess possible attachment functions served by an HCP and patients' attachment-related attitudes towards an HCP. Scales were constructed based on exploratory factor analysis. Measures of adult attachment, therapeutic alliance, perceived HCP characteristics and health utilisation were used to validate scales. Possible safe haven and secure base functions served by HCPs were strongly endorsed. A model with good fit (root mean square error of approximation=0.056) yielded 3 factors: 'HCP experienced as supportive and safe' (SUPPORT, α=0.94), 'HCP experienced as aversive' (AVERSE, α=0.86) and 'more and closer contact wanted with HCP' (WANT, α=0.85). SUPPORT was correlated with positive HCP characteristics and not with attachment insecurity. AVERSE was inversely correlated with positive HCP attributes and correlated with attachment insecurity. WANT was unrelated to positive HCP attributes, but correlated with attachment insecurity. Frequency of HCP contact was related to WANT (Kruskal-Wallis=21.9, p<0.001) and SUPPORT (Kruskal-Wallis=13.2, p=0.02), but not to AVERSE (Kruskal-Wallis=1.7, p=0.89). Patients attribute attachment functions of secure base and safe haven to HCPs. SUPPORT is related to positive appraisal of HCP characteristics; AVERSE is associated with discomfort in the HCP relationship that is related with perceived HCP characteristics and patients' insecure attachment; WANT is associated with unmet needs for connection with an HCP related to insecure attachment, but not to perceived HCP characteristics. These scales may be useful in studying the application of attachment theory to the HCP-patient relationship. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

The influence of shrinkage-cracking on the drying behaviour of White Portland cement using Single-Point Imaging (SPI).

PubMed

Beyea, S D; Balcom, B J; Bremner, T W; Prado, P J; Cross, A R; Armstrong, R L; Grattan-Bellew, P E

1998-11-01

The removal of water from pores in hardened cement paste smaller than 50 nm results in cracking of the cement matrix due to the tensile stresses induced by drying shrinkage. Cracks in the matrix fundamentally alter the permeability of the material, and therefore directly affect the drying behaviour. Using Single-Point Imaging (SPI), we obtain one-dimensional moisture profiles of hydrated White Portland cement cylinders as a function of drying time. The drying behaviour of White Portland cement, is distinctly different from the drying behaviour of related concrete materials containing aggregates.

Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tailby, Jonathan, E-mail: jmtailby@hotmail.co; MacKenzie, Kenneth J.D.

2010-05-15

The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C{sub 3}S, beta-C{sub 2}S, C{sub 3}A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, {sup 29}Si and {sup 27}Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poormore » strength development is suggested to be due to the retarded development of C-S-H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC-geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC-geopolymer composite stronger than hydrated OPC paste alone.« less

In Vivo Osteogenic Potential of Biomimetic Hydroxyapatite/Collagen Microspheres: Comparison with Injectable Cement Pastes

PubMed Central

Manzanares, Maria-Cristina; Ginebra, Maria-Pau; Franch, Jordi

2015-01-01

The osteogenic capacity of biomimetic calcium deficient hydroxyapatite microspheres with and without collagen obtained by emulsification of a calcium phosphate cement paste has been evaluated in an in vivo model, and compared with an injectable calcium phosphate cement with the same composition. The materials were implanted into a 5 mm defect in the femur condyle of rabbits, and bone formation was assessed after 1 and 3 months. The histological analysis revealed that the cements presented cellular activity only in the margins of the material, whereas each one of the individual microspheres was covered with osteogenic cells. Consequently, bone ingrowth was enhanced by the microspheres, with a tenfold increase compared to the cement, which was associated to the higher accessibility for the cells provided by the macroporous network between the microspheres, and the larger surface area available for osteoconduction. No significant differences were found in terms of bone formation associated with the presence of collagen in the materials, although a more extensive erosion of the collagen-containing microspheres was observed. PMID:26132468

Crystal structure of secretory protein Hcp3 from Pseudomonas aeruginosa.

PubMed

Osipiuk, Jerzy; Xu, Xiaohui; Cui, Hong; Savchenko, Alexei; Edwards, Aled; Joachimiak, Andrzej

2011-03-01

The Type VI secretion pathway transports proteins across the cell envelope of Gram-negative bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterial pathogen infecting humans, uses the type VI secretion pathway to export specific effector proteins crucial for its pathogenesis. The HSI-I virulence locus encodes for several proteins that has been proposed to participate in protein transport including the Hcp1 protein, which forms hexameric rings that assemble into nanotubes in vitro. Two Hcp1 paralogues have been identified in the P. aeruginosa genome, Hsp2 and Hcp3. Here, we present the structure of the Hcp3 protein from P. aeruginosa. The overall structure of the monomer resembles Hcp1 despite the lack of amino-acid sequence similarity between the two proteins. The monomers assemble into hexamers similar to Hcp1. However, instead of forming nanotubes in head-to-tail mode like Hcp1, Hcp3 stacks its rings in head-to-head mode forming double-ring structures.

Application of antifungal CFB to increase the durability of cement mortar.

PubMed

Park, Jong-Myong; Park, Sung-Jin; Kim, Wha-Jung; Ghim, Sa-Youl

2012-07-01

Antifungal cement mortar or microbiological calcium carbonate precipitation on cement surface has been investigated as functional concrete research. However, these research concepts have never been fused with each other. In this study, we introduced the antifungal calciteforming bacteria (CFB) Bacillus aryabhattai KNUC205, isolated from an urban tunnel (Daegu, South Korea). The major fungal deteriogens in urban tunnel, Cladosporium sphaerospermum KNUC253, was used as a sensitive fungal strain. B. aryabhattai KNUC205 showed CaCO3 precipitation on B4 medium. Cracked cement mortar pastes were made and neutralized by modified methods. Subsequently, the mixture of B. aryabhattai KNUC205, conidiospore of C. sphaerospermum KNUC253, and B4 agar was applied to cement cracks and incubated at 18 degrees C for 16 days. B. aryabhattai KNUC205 showed fungal growth inhibition against C. sphaerospermum. Furthermore, B. aryabhattai KNUC205 showed crack remediation ability and water permeability reduction of cement mortar pastes. Taken together, these results suggest that the CaCO3 precipitation and antifungal properties of B. aryabhattai KNUC205 could be used as an effective sealing or coating material that can also prevent deteriorative fungal growth. This study is the first application and evaluation research that incorporates calcite formation with antifungal capabilities of microorganisms for an environment-friendly and more effective protection of cement materials. In this research, the conception of microbial construction materials was expanded.

Portland cement concrete pavement best practices summary report.

DOT National Transportation Integrated Search

2010-08-01

This report summarizes the work and findings from WA-RD 744. This work consisted of four separate efforts related to best practices for portland cement concrete (PCC) pavement design and construction: (1) a review of past and current PCC pavement, (2...

Incorporation mode effect of Nano-silica on the rheological and mechanical properties of cementitious pastes and cement mortars

NASA Astrophysics Data System (ADS)

Safi, B.; Aknouche, H.; Mechakra, H.; Aboutaleb, D.; Bouali, K.

2018-04-01

Previous research indicates that the inclusion of nanosilica (NS) modifies the properties of the fresh and hardened state, compared to the traditional mineral additions. NS decreases the setting times of the cement mortar compared to silica fume (SF) and reduce of required water while improving the cohesion of the mixtures in the fresh state. Some authors estimate that the appropriate percentage of Nano-silica should be small (1 to 5% by weight) because of difficulties caused by agglomeration to particles during mixing, while others indicate that 10% by weight, if adjustments are made to the formulation to avoid an excess of self-drying and micro cracks that could impede strength. For this purpose, the present work aim to see the effect of the introduction mode of the nanosilica on the rheological and physic mechanical properties of cement mortars. In this study, NS was used either powdered with cement or in solution with the superplasticizer (Superplasticizer doped in nanosilica). Results show that the use of nanosilica powder (replacing cement on the one hand) has a negative influence on the rheological parameters and the rheological behavior of cementitious pastes. However, the introduction of nanosilica in solution in the superplasticizer (SP) was significantly improved the rheological parameters and the rheological behavior of cementitious pastes. Indeed, more the dosage of NS-doped SP increases more the shear stress and viscosities of the cementitious pastes become more fluid and manageable. A significant reduction of shear stress and plastic viscosity were observed that due to the increase in superplasticizer. A dosage of 1.5% NS-doped SP gave adequate fluidity and the shear rate was lower.

Investigation on the Rheological Behavior of Fly Ash Cement Composites at Paste and Concrete Level

NASA Astrophysics Data System (ADS)

Thiyagarajan, Hemalatha; Mapa, Maitri; Kushwaha, Rakhi

2018-06-01

Towards developing sustainable concrete, nowadays, high volume replacement of cement with fly ash (FA) is more common. Though the replacement of fly ash at 20-30% is widely accepted due to its advantages at both fresh and hardened states, applicability and acceptability of high volume fly ash (HVFA) is not so popular due to some adverse effects on concrete properties. Nowadays to suit various applications, flowing concretes such as self compacting concrete is often used. In such cases, implications of usage of HVFA on fresh properties are required to be investigated. Further, when FA replacement is beyond 40% in cement, it results in the reduction of strength and in order to overcome this drawback, additions such as nano calcium carbonate (CC), lime sludge (LS), carbon nano tubes (CNT) etc. are often incorporated to HVFA concrete. Hence, in this study, firstly, the influence of replacement level of 20-80% FA on rheological property is studied for both cement and concrete. Secondly, the influence of additions such as LS, CC and CNT on rheological parameters are discussed. It is found that the increased FA content improved the flowability in paste as well as in concrete. In paste, the physical properties such as size and shape of fly ash is the reason for increased flowability whereas in concrete, the paste volume contributes dominantly for the flowability rather than the effect due to individual FA particle. Reduced density of FA increases the paste volume in FA concrete thus reducing the interparticle friction by completely coating the coarse aggregate.

Lunar cement and lunar concrete

NASA Technical Reports Server (NTRS)

Lin, T. D.

1991-01-01

Results of a study to investigate methods of producing cements from lunar materials are presented. A chemical process and a differential volatilization process to enrich lime content in selected lunar materials were identified. One new cement made from lime and anorthite developed compressive strengths of 39 Mpa (5500 psi) for 1 inch paste cubes. The second, a hypothetical composition based on differential volatilization of basalt, formed a mineral glass which was activated with an alkaline additive. The 1 inch paste cubes, cured at 100C and 100 percent humidity, developed compressive strengths in excess of 49 Mpa (7100 psi). Also discussed are tests made with Apollo 16 lunar soil and an ongoing investigation of a proposed dry mix/steam injection procedure for casting concrete on the Moon.

Can patients be ‘attached’ to healthcare providers? An observational study to measure attachment phenomena in patient–provider relationships

PubMed Central

Maunder, Robert G; Hunter, Jonathan J

2016-01-01

Objectives To develop and assess the validity of measures of patients' attachment-related perceptions of experiences with healthcare providers (HCPs). Setting Online survey. Participants 181 people provided consent and 119 completed the survey (66%). Most participants were women (80%). Primary and secondary outcome measures Questions were developed to assess possible attachment functions served by an HCP and patients' attachment-related attitudes towards an HCP. Scales were constructed based on exploratory factor analysis. Measures of adult attachment, therapeutic alliance, perceived HCP characteristics and health utilisation were used to validate scales. Results Possible safe haven and secure base functions served by HCPs were strongly endorsed. A model with good fit (root mean square error of approximation=0.056) yielded 3 factors: ‘HCP experienced as supportive and safe’ (SUPPORT, α=0.94), ‘HCP experienced as aversive’ (AVERSE, α=0.86) and ‘more and closer contact wanted with HCP’ (WANT, α=0.85). SUPPORT was correlated with positive HCP characteristics and not with attachment insecurity. AVERSE was inversely correlated with positive HCP attributes and correlated with attachment insecurity. WANT was unrelated to positive HCP attributes, but correlated with attachment insecurity. Frequency of HCP contact was related to WANT (Kruskal-Wallis=21.9, p<0.001) and SUPPORT (Kruskal-Wallis=13.2, p=0.02), but not to AVERSE (Kruskal-Wallis=1.7, p=0.89). Conclusions Patients attribute attachment functions of secure base and safe haven to HCPs. SUPPORT is related to positive appraisal of HCP characteristics; AVERSE is associated with discomfort in the HCP relationship that is related with perceived HCP characteristics and patients' insecure attachment; WANT is associated with unmet needs for connection with an HCP related to insecure attachment, but not to perceived HCP characteristics. These scales may be useful in studying the application of attachment theory to the HCP–patient relationship. PMID:27178976

Fundamental investigations related to the mitigation of volume changes in cement-based materials at early ages

NASA Astrophysics Data System (ADS)

Sant, Gaurav Niteen

The increased use of high-performance, low water-to-cement (w/c) ratio concretes has led to increased occurrences of early-age shrinkage cracking in civil engineering structures. To reduce the magnitude of early-age shrinkage and the potential for cracking, mitigation strategies using shrinkage reducing admixtures (SRAs), saturated lightweight aggregates, expansive cements and extended moist curing durations in construction have been recommended. However, to appropriately utilize these strategies, it is important to have a complete understanding of the driving forces of early-age volume change and how these methods work from a materials perspective to reduce shrinkage. This dissertation uses a first-principles approach to understand the mechanism of shrinkage reducing admixtures (SRAs) to generate an expansion and mitigate shrinkage at early-ages, quantify the influence of a CaO-based expansive additive in reducing unrestrained shrinkage, residual stress development and the cracking potential at early-ages and quantify the influence of shrinkage reducing admixtures (SRAs) and cement hydration (pore structure refinement) on the reduction induced in the fluid transport properties of the material. The effects of shrinkage reducing admixtures (SRAs) are described in terms of inducing autogenous expansions in cement pastes at early ages. An evaluation comprising measurements of autogenous deformation, x-ray diffraction (Rietveld analysis), pore solution and thermogravimetric analysis and electron microscopy is performed to understand the chemical nature and physical effects of the expansion. Thermodynamic calculations performed on the measured liquid-phase compositions indicate the SRA produces elevated Portlandite super-saturations in the pore solution which results in crystallization stress driven expansions. The thermodynamic calculations are supported by deformation measurements performed on cement pastes mixed in solutions saturated with Portlandite or containing additional Sodium Hydroxide. Further, to quantify the influence of temperature on volume changes in SRA containing materials, deformation measurements are performed at different temperatures. The results indicate maturity transformations are incapable of simulating volume changes over any temperature regime due to the influence of temperature on salt solubility and pore solution composition, crystallization stresses and self-desiccation. The performance of a CaO-based expansive additive is evaluated over a range of additive concentrations and curing conditions to quantify the reduction in restrained and unrestrained volume changes effected in low w/c cement pastes. The results suggest, under unrestrained sealed conditions the additive generates an expansion and reduces the magnitude of total shrinkage experienced by the material. However, the extent of drying shrinkage developed is noted to be similar in all systems and independent of the additive dosage. Under restrained sealed conditions, the additive induces a significant compressive stress which delays tensile stress development in the system. However, a critical additive concentration (around four percent) needs to be exceeded to appreciably reduce the risk of cracking at early-ages. The influence of shrinkage reducing admixtures (SRAs) is quantified in terms of the effects of SRA addition on fluid transport in cement-based materials. The change in the cement paste's pore solution properties, i.e., the surface tension and fluid-viscosity, induced by the addition of a SRA is observed to depress the fluid-sorption and wetting moisture diffusion coefficients, with the depression being a function of the SRA concentration. The experimental results are compared to analytical descriptions of water sorption and a good correlation is observed. These results allow for the change in pore-solution and fluid-transport properties to be incorporated from a fundamental perspective in models which aim to describe the service-life of structures. Several experimental techniques such as chemical shrinkage, low temperature calorimetry and electrical impedance spectroscopy are evaluated in terms of their suitability to identify capillary porosity depercolation in cement pastes. The evidence provided by the experiments is: (1) that there exists a capillary porosity depercolation threshold around 20% capillary porosity in cement pastes and (2) low temperature calorimetry is not suitable to detect porosity depercolation in cement pastes containing SRAs. Finally, the influence of porosity depercolation is demonstrated in terms of the reduction effected in the transport properties (i.e., the fluid-sorption coefficient) of the material as quantified using x-ray attenuation measurements. The study relates the connectivity of the pore structure to the fluid transport response providing insights related to the development of curing technologies and the specification of wet curing regimes during construction.

Modeling Nanomechanical Behavior of Calcium-Silicate-Hydrate

DTIC Science & Technology

2012-08-01

applicability to hardened pastes of tricalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag , metakaolin, or silica...Hydrated Nanocomposites: Concrete, Bone, and Shale. J. Am. Ceram . Soc., 90(9): 2677-2692. Wu, Jianzhong. and John M. Prausnitz. 2002. Generalizations for

Optimum mixture proportions for concretes containing fly ash and silica fume.

DOT National Transportation Integrated Search

1991-01-01

Concretes with equal water/cement ratios and equal paste volumes of various combinations of cement, fly ash, and silica fume were tested to establish parameters for strength and chloride permeability. Comparative specimens with Type II and Type III c...

Experimental Study on Comprehensive Performance of Full Tailings Paste Filling in Jiaojia Gold Mine.

NASA Astrophysics Data System (ADS)

Zhang, Z. H.; Zou, Q. B.; Wang, P. Z.

2017-11-01

Filling mining method is the main method of modern underground mining. High concentration cementation is carried out using coarse tailing of +37 μm, and the mine has maturely used classified tailings paste filling technology. The gold mine studied on the performance of full tailings paste filling in order to maximize the use of tailings, reduce -37 μm fine tailings discharged into the tailing pond, reduce mining cost and eliminate security risks. The results show that: comprehensive index of full tailings paste filling is higher than that of classified tailings high concentration cementation filling, and the full tailings paste filling of 76% mass concentration has the best comprehensive index of slump, expansibility, yield stress and viscosity to meet the mining method requirements, which can effectively reduce the mining loss rate and dilution rate.

Adsorption of superplasticizer admixtures on alkali-activated slag pastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palacios, M.; Houst, Y.F.; Bowen, P.

2009-08-15

Alkali-activated slag (AAS) binders are obtained by a manufacturing process less energy-intensive than ordinary Portland cement (OPC) and involves lower greenhouse gasses emission. These alkaline cements allow the production of high mechanical strength and durable concretes. In the present work, the adsorption of different superplasticizer admixtures (naphthalene-based, melamine-based and a vinyl copolymer) on the slag particles in AAS pastes using alkaline solutions with different pH values have been studied in detail. The effect of the superplasticizers on the yield stress and plastic viscosity of the AAS and OPC pastes have been also evaluated. The results obtained allowed us to concludemore » that the adsorption of the superplasticizers on AAS pastes is independent of the pH of the alkaline solutions used and lower than on OPC pastes. However, the effect of the admixtures on the rheological parameters depends directly on the type and dosage of the superplasticizer as well as of the binder used and, in the case of the AAS, on the pH of the alkaline activator solution. In 11.7-pH NaOH-AAS pastes the dosages of the superplasticizers required to attain similar reduction in the yield stress are ten-fold lower than for Portland cement. In this case the superplasticizers studied show a fluidizing effect considerably higher in 11.7-pH NaOH-AAS pastes than in OPC pastes. In 13.6-pH NaOH-AAS pastes, the only admixture observed to affect the rheological parameters is the naphthalene-based admixture due to its higher chemical stability in such extremely alkaline media.« less

Modification of Wood Fiber for Use in Cement Board

NASA Astrophysics Data System (ADS)

Han, F. Q.; Tan, X.; Zhao, F. Q.

2017-12-01

When ordinary Portland cement is used for wood fiber cement (WFC) board, the setting time is too long, even hard to solidify. Three methods can be used for wood fiber modification, i.e., soaking in water, treated with alkali solution and coated with some substances on the fiber surface. The results show that the proper water-cement ratio of WFC paste is 1:1.3 in the case of wood cement ratio being 1:1. The WFC board from modified wood fiber and cement is better than the control samples, in which the combined treatment, i.e. soaking in hot water and then coating with alkali-BFS-EVA slurry, behaves best. It is proved that ordinary Portland cement can be used to produce WFC board, with the modified wood fiber, which can greatly reduce production costs.

Radiation effects in concrete for nuclear power plants, Part II: Perspective from micromechanical modeling

DOE PAGES

Le Pape, Yann; Field, Kevin G.; Remec, Igor

2014-11-15

The need to understand and characterize the effects of neutron irradiation on concrete has become urgent because of the possible extension of service life of many nuclear power generating stations. Current knowledge is primarily based on a collection of data obtained in test reactors. These results are inherently difficult to interpret because materials and testing conditions are inconsistent. A micromechanical approach based on the Hashin composite sphere model is presented to derive a first-order separation of the effects of radiation on cement paste and aggregate, and, also, on their interaction. Although the scarcity of available data limits the validation ofmore » the model, it appears that, without negating a possible gamma-ray induced effect, the neutron-induced damage and swelling of aggregate plays a predominant role on the overall concrete expansion and the damage of the cement paste. Finally, the radiation-induced volumetric expansion (RIVE) effects can also be aided by temperature elevation and shrinkage in the cement paste.« less

Impact of the flu mask regulation on health care personnel influenza vaccine acceptance rates.

PubMed

Edwards, Frances; Masick, Kevin D; Armellino, Donna

2016-10-01

Achieving high vaccination rates of health care personnel (HCP) is critical in preventing influenza transmission from HCP to patients and from patients to HCP; however, acceptance rates remain low. In 2013, New York State adopted the flu mask regulation, requiring unvaccinated HCP to wear a mask when in areas where patients are present. The purpose of this study assessed the impact of the flu mask regulation on the HCP influenza vaccination rate. A 13-question survey was distributed electronically and manually to the HCP to examine their knowledge of influenza transmission and the influenza vaccine and their personal vaccine acceptance history and perception about the use of the mask while working if not vaccinated. There were 1,905 respondents; 87% accepted the influenza vaccine, and 63% were first-time recipients who agreed the regulation influenced their vaccination decision. Of the respondents who declined the vaccine, 72% acknowledge HCP are at risk for transmitting influenza to patients, and 56% reported they did not receive enough information to make an educated decision. The flu mask protocol may have influenced HCP's choice to be vaccinated versus wearing a mask. The study findings supported that HCP may not have adequate knowledge on the morbidity and mortality associated with influenza. Regulatory agencies need to consider an alternative approach to increase HCP vaccination, such as mandating the influenza vaccine for HCP. Copyright © 2016 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Basic properties of calcium phosphate cement containing atelocollagen in its liquid or powder phases.

PubMed

Miyamoto, Y; Ishikawa, K; Takechi, M; Toh, T; Yuasa, T; Nagayama, M; Suzuki, K

1998-01-01

The basic properties of calcium phosphate cement (CPC) containing atelocollagen, the main component of the organic substrate in bone, were studied in an initial evaluation for the fabrication of modified CPC. The setting time of conventional CPC (c-CPC) was prolonged to over 100 min when c-CPC contained 1% or more atelocollagen. The diametral tensile strength (DTS) of c-CPC decreased linearly with the collagen content, descending to below the detection limit when the c-CPC contained 3% or more atelocollagen. Therefore, use of c-CPC as the base cement seems inappropriate for the fabrication of atelocollagen-containing CPC. In contrast, the cement set at 9-34 min when fast-setting CPC (FSCPC) was used as the base cement and contained 1-5% atelocollagen, respectively. Although addition of atelocollagen resulted in the decrease of DTS of the set mass, the DTS was approximately the same, 6-8 MPa, at contents of atelocollagen between 1% and 5%. When atelocollagen was added to FSCPC, the handling property was improved significantly. The paste also became more adhesive with increase in atelocollagen content. These properties are desirable for its use in surgical procedures since, for example, bony defects can be filled easily and without a space interposed between the bone and cement paste. Although there are some disadvantages for the addition of atelocollagen to CPC, it can be accepted as long as FSCPC was used as the base cement. We conclude that further evaluations of the effects of atelocollagen, such as biocompatibility, bone synthesis, and bone replacement behaviour should be done, using FSCPC as the base cement.

Hispanic Women's Health Care Provider Control Expectations: The Influence of Fatalism and Acculturation

PubMed Central

Roncancio, Angelica M.; Ward, Kristy K.; Berenson, Abbey B.

2011-01-01

In order to understand how culture influences Hispanic women's views about their health care provider (HCP), we examined the relationship between acculturation and fatalism in the HCP control expectations of Hispanic women. (A HCP control expectation is the extent to which an individual believes that her HCP has control over her health.) We predicted that acculturation would be negatively associated with HCP control expectations and fatalism would be positively associated with HCP control expectations. A group of 1,027 young Hispanic women (mean age 21.24 years; SD = 2.46) who were University of Texas Medical Branch clinic patients completed a comprehensive survey. Structural equation modeling was employed and as predicted, acculturation was negatively associated with HCP control expectations (p < .001) and fatalism was positively associated (p < .001). Understanding fatalism, acculturation, and their influence on HCP control expectations will help us understand this population's perceptions of their HCPs. This knowledge will assist HCPs in providing culturally competent care which will increase adherence to medical treatment and screening guidelines. PMID:21551928

Hispanic women's health care provider control expectations: the influence of fatalism and acculturation.

PubMed

Roncancio, Angelica M; Ward, Kristy K; Berenson, Abbey B

2011-05-01

In order to understand how culture influences Hispanic women's views about their health care provider (HCP), we examined the relationship between acculturation and fatalism in the HCP control expectations of Hispanic women. (A HCP control expectation is the extent to which an individual believes that her HCP has control over her health.) We predicted that acculturation would be negatively associated with HCP control expectations, and fatalism would be positively associated with HCP control expectations. A group of 1,027 young Hispanic women (mean age 21.24 years; SD=2.46) who were University of Texas Medical Branch clinic patients completed a comprehensive survey. Structural equation modeling was employed and, as predicted, acculturation was negatively associated with HCP control expectations (p<.001) and fatalism was positively associated (p<.001). Understanding fatalism, acculturation, and their influence on HCP control expectations will help us understand this population's perceptions of their HCPs. This knowledge will assist HCPs in providing culturally competent care which will increase adherence to medical treatment and screening guidelines.

Preventive Effects of Houttuynia cordata Extract for Oral Infectious Diseases

PubMed Central

Sekita, Yasuko; Murakami, Keiji; Amoh, Takashi; Ogata, Shohei; Matsuo, Takashi; Miyake, Yoichiro; Kashiwada, Yoshiki

2016-01-01

Houttuynia cordata (HC) (Saururaceae) has been used internally and externally as a traditional medicine and as an herbal tea for healthcare in Japan. Our recent survey showed that HC poultice (HCP) prepared from smothering fresh leaves of HC had been frequently used for the treatment of purulent skin diseases with high effectiveness. Our experimental study also demonstrated that ethanol extract of HCP (eHCP) has antibacterial, antibiofilm, and anti-inflammatory effects against S. aureus which caused purulent skin diseases. In this study, we focused on novel effects of HCP against oral infectious diseases, such as periodontal disease and dental caries. We determined the antimicrobial and antibiofilm effects of water solution of HCP ethanol extract (wHCP) against important oral pathogens and investigated its cytotoxicity and anti-inflammatory effects on human oral epithelial cells. wHCP had moderate antimicrobial effects against some oral microorganisms and profound antibiofilm effects against Fusobacterium nucleatum, Streptococcus mutans, and Candida albicans. In addition, wHCP had no cytotoxic effects and could inhibit interleukin-8 and CCL20 productions by Porphyromonas gingivalis lipopolysaccharide-stimulated human oral keratinocytes. Our findings suggested that wHCP may be clinically useful for preventing oral infectious diseases as a mouthwash for oral care. PMID:27413739

Preventive Effects of Houttuynia cordata Extract for Oral Infectious Diseases.

PubMed

Sekita, Yasuko; Murakami, Keiji; Yumoto, Hiromichi; Amoh, Takashi; Fujiwara, Natsumi; Ogata, Shohei; Matsuo, Takashi; Miyake, Yoichiro; Kashiwada, Yoshiki

2016-01-01

Houttuynia cordata (HC) (Saururaceae) has been used internally and externally as a traditional medicine and as an herbal tea for healthcare in Japan. Our recent survey showed that HC poultice (HCP) prepared from smothering fresh leaves of HC had been frequently used for the treatment of purulent skin diseases with high effectiveness. Our experimental study also demonstrated that ethanol extract of HCP (eHCP) has antibacterial, antibiofilm, and anti-inflammatory effects against S. aureus which caused purulent skin diseases. In this study, we focused on novel effects of HCP against oral infectious diseases, such as periodontal disease and dental caries. We determined the antimicrobial and antibiofilm effects of water solution of HCP ethanol extract (wHCP) against important oral pathogens and investigated its cytotoxicity and anti-inflammatory effects on human oral epithelial cells. wHCP had moderate antimicrobial effects against some oral microorganisms and profound antibiofilm effects against Fusobacterium nucleatum, Streptococcus mutans, and Candida albicans. In addition, wHCP had no cytotoxic effects and could inhibit interleukin-8 and CCL20 productions by Porphyromonas gingivalis lipopolysaccharide-stimulated human oral keratinocytes. Our findings suggested that wHCP may be clinically useful for preventing oral infectious diseases as a mouthwash for oral care.

Properties of injectable ready-to-use calcium phosphate cement based on water-immiscible liquid.

PubMed

Heinemann, S; Rössler, S; Lemm, M; Ruhnow, M; Nies, B

2013-04-01

Calcium phosphate cements (CPCs) are highly valuable materials for filling bone defects and bone augmentation by minimal invasive application via percutaneous injection. In the present study some key features were significantly improved by developing a novel injectable ready-to-use calcium phosphate cement based on water-immiscible carrier liquids. A combination of two surfactants was identified to facilitate the targeted discontinuous exchange of the liquid for water after contact with aqueous solutions, enabling the setting reaction to take place at distinct ratios of cement components to water. This prolonged the shelf life of the pre-mixed paste and enhanced reproducibility during application and setting reactions. The developed paste technology is applicable for different CPC formulations. Evaluations were performed for the formulation of an α-TCP-based CPC as a representative example for the preparation of injectable pastes with a powder-to-carrier liquid ratio of up to 85:15. We demonstrate that the resulting material retains the desirable properties of conventional CPC counterparts for fast setting, mechanical strength and biocompatibility, shows improved cohesion and will most probably show a similar degree of resorbability due to identical mineral structure of the set products. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effects of TEA·HCl hardening accelerator on the workability of cement-based materials

NASA Astrophysics Data System (ADS)

Pan, Wenhao; Ding, Zhaoyang; Chen, Yanwen

2017-03-01

The aim of the test is to research the influence rules of TEA·HCl on the workability of cement paste and concrete. Based on the features of the new hardening accelerator, an experimental analysis system were established through different dosages of hardening accelerator, and the feasibility of such accelerator to satisfy the need of practical engineering was verified. The results show that adding of the hardening accelerator can accelerate the cement hydration, and what’s more, when the dosage was 0.04%, the setting time was the shortest while the initial setting time and final setting time were 130 min and 180 min, respectively. The initial fluidity of cement paste of adding accelerator was roughly equivalent compared with that of blank. After 30 min, fluidity loss would decrease with the dosage increasing, but fluidity may increase. The application of the hardening accelerator can make the early workability of concrete enhance, especially the slump loss of 30 min can improve more significantly. The bleeding rate of concrete significantly decreases after adding TEA·HCl. The conclusion is that the new hardening accelerator can meet the need of the workability of cement-based materials in the optimum dosage range.

Evaluation of the phase properties of hydrating cement composite using simulated nanoindentation technique

NASA Astrophysics Data System (ADS)

Gautham, S.; Sindu, B. S.; Sasmal, Saptarshi

2017-10-01

Properties and distribution of the products formed during the hydration of cementitious composite at the microlevel are investigated using a nanoindentation technique. First, numerical nanoindentation using nonlinear contact mechanics is carried out on three different phase compositions of cement paste, viz. mono-phase Tri-calcium Silicate (C3S), Di-calcium Silicate (C2S) and Calcium-Silicate-Hydrate (CSH) individually), bi-phase (C3S-CSH, C2S-CSH) and multi-phase (more than 10 individual phases including water pores). To reflect the multi-phase characteristics of hydrating cement composite, a discretized multi-phase microstructural model of cement composite during the progression of hydration is developed. Further, a grid indentation technique for simulated nanoindentation is established, and employed to evaluate the mechanical characteristics of the hydrated multi-phase cement paste. The properties obtained from the numerical studies are compared with those obtained from experimental grid nanoindentation. The influence of composition and distribution of individual phase properties on the properties obtained from indentation are closely investigated. The study paves the way to establishing the procedure for simulated grid nanoindentation to evaluate the mechanical properties of heterogeneous composites, and facilitates the design of experimental nanoindentation.

Retention of metal-ceramic crowns with contemporary dental cements.

PubMed

Johnson, Glen H; Lepe, Xavier; Zhang, Hai; Wataha, John C

2009-09-01

New types of crown and bridge cement are in use by practitioners, and independent studies are needed to assess their effectiveness. The authors conducted a study in three parts (study A, study B, and study C) and to determine how well these new cements retain metal-ceramic crowns. The authors prepared teeth with a 20-degree taper and a 4-millimeter length. They cast high-noble metal-ceramic copings, then fitted and cemented them with a force of 196 newtons. The types of cements they used were zinc phosphate, resin-modified glass ionomer, conventional resin and self-adhesive modified resin. They thermally cycled the cemented copings, then removed them. They recorded the removal force and calculated the stress of dislodgment by using the surface area of each preparation. They used a single-factor analysis of variance to analyze the data (alpha = .05). The mean stresses necessary to remove crowns, in megapascals, were 8.0 for RelyX Luting (3M ESPE, St. Paul, Minn.), 7.3 for RelyX Unicem (3M ESPE), 5.7 for Panavia F (Kuraray America, New York) and 4.0 for Fuji Plus (GC America, Alsip, Ill.) in study A; 8.1 for RelyX Luting, 2.6 for RelyX Luting Plus (3M ESPE) and 2.8 for Fuji CEM (GC America) in study B; and 4.9 for Maxcem (Kerr, Orange, Calif.), 4.0 for BisCem (Bisco, Schaumburg, Ill.), 3.7 for RelyX Unicem Clicker (3M ESPE), 2.9 for iCEM (Heraeus Kulzer, Armonk, N.Y.) and 2.3 for Fleck's Zinc Cement (Keystone Industries, Cherry Hill, N.J.) in study C. Powder-liquid versions of new cements were significantly more retentive than were paste-paste versions of the same cements. The mean value of crown removal stress for the new self-adhesive modified-resin cements varied appreciably among the four cements tested. All cements retained castings as well as or better than did zinc phosphate cement. Powder-liquid versions of cements, although less convenient to mix, may be a better clinical choice when crown retention is an issue. All cements tested will retain castings adequately on ideal preparations because the corresponding removal stresses are comparable with or higher than those associated with zinc phosphate. Powder-liquid resin-modified glass ionomer cement, selected self-adhesive modified-resin cements and conventional resin cements provide additional retention when desired.

Magnitude assessment of free and hydrated limes present in RPCC aggregates : research implementation plan.

DOT National Transportation Integrated Search

2005-10-11

Aggregates obtained from recycled reinforced Portland cement concrete (RPCC) pavement used as base or : subbase may produce tufa in the underdrain outlet pipes. The most likely source of the tufa is related to the : fine aggregate and cement paste. I...

Expert Guidance: Healthcare Personnel Attire in Non-Operating Room Settings

PubMed Central

Bearman, Gonzalo; Bryant, Kristina; Leekha, Surbhi; Mayer, Jeanmarie; Munoz-Price, L. Silvia; Murthy, Rekha; Palmore, Tara; Rupp, Mark E.; White, Joshua

2016-01-01

Healthcare personnel (HCP) attire is an aspect of the medical profession steeped in culture and tradition. The role of attire in cross-transmission remains poorly established and until more definitive information exists, priority should be placed on evidence-based measures to prevent hospital acquired infections (HAI). This paper aims to provide a general guidance to the medical community regarding HCP attire outside the operating room. In addition to the initial guidance statement, the manuscript has three major components: 1. A review and interpretation of the medical literature regarding a) perceptions of HCP attire (from both HCP and patients) and b) evidence for contamination of attire and its potential contribution to cross-transmission; 2. A review of hospital policies related to HCP attire, as submitted by members of the SHEA Guidelines Committee; 3. A survey of SHEA and SHEA Research Network members, which assessed both institutional HCP attire policies and perceptions of HCP attire in the cross-transmission of pathogens. Recommendations for HCP attire should attempt to balance professional appearance, comfort, and practicality with the potential role of apparel in the cross-transmission of pathogens. Although the optimal choice of HCP attire for inpatient care remains undefined, we provide recommendations on the use of white coats, neck ties, footwear, the bare-below-the-elbows strategy, and laundering. Institutions considering these optional measures should introduce them with a well-organized communication and education effort directed at both HCP and patients. Appropriately designed studies are needed to better define the relationship between HCP attire and HAIs. PMID:24442071

Healthcare personnel attire in non-operating-room settings.

PubMed

Bearman, Gonzalo; Bryant, Kristina; Leekha, Surbhi; Mayer, Jeanmarie; Munoz-Price, L Silvia; Murthy, Rekha; Palmore, Tara; Rupp, Mark E; White, Joshua

2014-02-01

Healthcare personnel (HCP) attire is an aspect of the medical profession steeped in culture and tradition. The role of attire in cross-transmission remains poorly established, and until more definitive information exists priority should be placed on evidence-based measures to prevent healthcare-associated infections (HAIs). This article aims to provide general guidance to the medical community regarding HCP attire outside the operating room. In addition to the initial guidance statement, the article has 3 major components: (1) a review and interpretation of the medical literature regarding (a) perceptions of HCP attire (from both HCP and patients) and (b) evidence for contamination of attire and its potential contribution to cross-transmission; (2) a review of hospital policies related to HCP attire, as submitted by members of the Society for Healthcare Epidemiology of America (SHEA) Guidelines Committee; and (3) a survey of SHEA and SHEA Research Network members that assessed both institutional HCP attire policies and perceptions of HCP attire in the cross-transmission of pathogens. Recommendations for HCP attire should attempt to balance professional appearance, comfort, and practicality with the potential role of apparel in the cross-transmission of pathogens. Although the optimal choice of HCP attire for inpatient care remains undefined, we provide recommendations on the use of white coats, neckties, footwear, the bare-below-the-elbows strategy, and laundering. Institutions considering these optional measures should introduce them with a well-organized communication and education effort directed at both HCP and patients. Appropriately designed studies are needed to better define the relationship between HCP attire and HAIs.

Imaging Wellbore Cement Degradation by Carbon Dioxide under Geologic Sequestration Conditions Using X-ray Computed Microtomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Hun Bok; Jansik, Danielle; Um, Wooyong

2013-01-02

ABSTRACT: X-ray microtomography (XMT), a nondestructive three-dimensional imaging technique, was applied to demonstrate its capability to visualize the mineralogical alteration and microstructure changes in hydrated Portland cement exposed to carbon dioxide under geologic sequestration conditions. Steel coupons and basalt fragments were added to the cement paste in order to simulate cement-steel and cement-rock interfaces. XMT image analysis showed the changes of material density and porosity in the degradation front (density: 1.98 g/cm3, porosity: 40%) and the carbonated zone (density: 2.27 g/cm3, porosity: 23%) after reaction with CO2- saturated water for 5 months compared to unaltered cement (density: 2.15 g/cm3, porosity:more » 30%). Three-dimensional XMT imaging was capable of displaying spatially heterogeneous alteration in cement pores, calcium carbonate precipitation in cement cracks, and preferential cement alteration along the cement-steel and cement-rock interfaces. This result also indicates that the interface between cement and host rock or steel casing is likely more vulnerable to a CO2 attack than the cement matrix in a wellbore environment. It is shown here that XMT imaging can potentially provide a new insight into the physical and chemical degradation of wellbore cement by CO2 leakage.« less

Bond-orientational analysis of hard-disk and hard-sphere structures.

PubMed

Senthil Kumar, V; Kumaran, V

2006-05-28

We report the bond-orientational analysis results for the thermodynamic, random, and homogeneously sheared inelastic structures of hard-disks and hard-spheres. The thermodynamic structures show a sharp rise in the order across the freezing transition. The random structures show the absence of crystallization. The homogeneously sheared structures get ordered at a packing fraction higher than the thermodynamic freezing packing fraction, due to the suppression of crystal nucleation. On shear ordering, strings of close-packed hard-disks in two dimensions and close-packed layers of hard-spheres in three dimensions, oriented along the velocity direction, slide past each other. Such a flow creates a considerable amount of fourfold order in two dimensions and body-centered-tetragonal (bct) structure in three dimensions. These transitions are the flow analogs of the martensitic transformations occurring in metals due to the stresses induced by a rapid quench. In hard-disk structures, using the bond-orientational analysis we show the presence of fourfold order. In sheared inelastic hard-sphere structures, even though the global bond-orientational analysis shows that the system is highly ordered, a third-order rotational invariant analysis shows that only about 40% of the spheres have face-centered-cubic (fcc) order, even in the dense and near-elastic limits, clearly indicating the coexistence of multiple crystalline orders. When layers of close-packed spheres slide past each other, in addition to the bct structure, the hexagonal-close-packed (hcp) structure is formed due to the random stacking faults. Using the Honeycutt-Andersen pair analysis and an analysis based on the 14-faceted polyhedra having six quadrilateral and eight hexagonal faces, we show the presence of bct and hcp signatures in shear ordered inelastic hard-spheres. Thus, our analysis shows that the dense sheared inelastic hard-spheres have a mixture of fcc, bct, and hcp structures.

[Apoptosis inducing effect of Hechanpian on human lung adenocarcinoma A549 cells].

PubMed

Xiong, Shao-Quan; Zhou, Dai-Han; Lin, Li-Zhu

2010-06-01

To study the apoptosis inducing effects of Hechanpian (HCP) on human lung adenocarcinoma A549 cells. HCP containing rat serum was prepared and applied on A549 cells. The cell growth inhibition rate was tested by MTT assay; the effect of HCP on cell apoptosis was observed with Propidium iodide (PI) staining and flow cytometry analysis; the mRNA expression of epidermal growth factor receptor (EGFR) was detected through RT-PCR. The growth of A549 cells was obviously inhibited after being treated by HCP containing serum, and the cells presented an apoptotic change. The cell apoptosis rate after treated by serum containing 10% and 20% HCP was 20.5% and 33.2%, respectively, significantly higher than that in the control (6.1% in cells didn't treated with HCP, P < 0.05). Compared with control, EGFR mRNA expression in HCP treated cells was significantly lower (P < 0.05). HCP has apoptosis inducing effect on A549 cell, and its molecular mechanism is probably correlated with the inhibition of EGFR gene transcription.

Effect of the fcc-hcp martensitic transition on the equation of state of solid krypton up to 140 GPa

NASA Astrophysics Data System (ADS)

Rosa, A. D.; Garbarino, G.; Briggs, R.; Svitlyk, V.; Morard, G.; Bouhifd, M. A.; Jacobs, J.; Irifune, T.; Mathon, O.; Pascarelli, S.

2018-03-01

Solid krypton (Kr) undergoes a pressure-induced martensitic phase transition from a face-centered cubic (fcc) to a hexagonal close-packed (hcp) structure. These two phases coexist in a very wide pressure domain inducing important modifications of the bulk properties of the resulting mixed phase system. Here, we report a detailed in situ x-ray diffraction and absorption study of the influence of the fcc-hcp phase transition on the compression behavior of solid krypton in an extended pressure domain up to 140 GPa. The onset of the hcp-fcc transformation was observed in this study at around 2.7 GPa and the coexistence of these two phases up to 140 GPa, the maximum investigated pressure. The appearance of the hcp phase is also evidenced by the pressure-induced broadening and splitting of the first peak in the XANES spectra. We demonstrate that the transition is driven by a continuous nucleation and intergrowth of nanometric hcp stacking faults that evolve in the fcc phase. These hcp stacking faults are unaffected by high-temperature annealing, suggesting that plastic deformation is not at their origin. The apparent small Gibbs free-energy differences between the two structures that decrease upon compression may explain the nucleation of hcp stacking faults and the large coexistence domain of fcc and hcp krypton. We observe a clear anomaly in the equation of state of the fcc solid at ˜20 GPa when the proportion of the hcp form reaches ˜20 % . We demonstrate that this anomaly is related to the difference in stiffness between the fcc and hcp phases and propose two distinct equation of states for the low and high-pressure regimes.

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes.

PubMed

Novais, Veridiana Resende; Raposo, Luís Henrique Araújo; Miranda, Rafael Resende de; Lopes, Camila de Carvalho Almança; Simamoto, Paulo Cézar; Soares, Carlos José

2017-01-01

The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC) and one light-cured (Variolink Veneer). The dual-cured resin cements were tested by using the dual activation mode (base and catalyst) and light-activation mode (base paste only). For degree of conversion (DC) (n=5), a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR). For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05). Scanning electron microscopy (SEM) was used for classifying the failure modes. Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

The Effect of a Federal Controlled Substance Act Schedule Change on Hydrocodone Combination Products Claims in a Medicaid Population.

PubMed

Tran, Stephanie; Lavitas, Pavel; Stevens, Karen; Greenwood, Bonnie C; Clements, Karen; Alper, Caroline J; Lenz, Kimberly; Price, Mylissa; Hydery, Tasmina; Arnold, Jennifer L; Takeshita, Mito; Bacon, Rachel; Peristere, Justin P; Jeffrey, Paul L

2017-05-01

In 2012, hydrocodone combination products (HCPs) were the most prescribed medications in the United States. Under the Controlled Substance Act of 1970, hydrocodone alone was classified as a Schedule II drug, while HCPs were classified as Schedule III, indicating a lower risk for abuse and misuse. However, according to a Drug Enforcement Agency analysis, the addition of nonopioids has not been shown to diminish abuse potential of hydrocodone. In response to concerns for drug abuse and overdose, the Drug Enforcement Agency rescheduled HCPs to Schedule II in October 2014, with the intent of limiting overprescribing and increasing awareness of their abuse potential. However, it is unknown whether this has affected the overall claims for HCPs in a Medicaid population. To (a) compare the trend in HCP prescription claims with select non-HCP (opioid and nonopioid) analgesic claims before and after the HCP schedule change in the Massachusetts Medicaid fee-for-service/Primary Care Clinician plan population and (b) identify if there was a change in HCP new start member and claim characteristics before and after the HCP schedule change. This quasi-experimental, retrospective study used enrollment and pharmacy claims data to evaluate all members in the study population 1 year before and after the HCP schedule change. The number of claims for HCPs and select non-HCP analgesics was reported as the monthly rate per total population, and an interrupted time series analysis compared the change in the monthly rate of claims across groups. Members with 1 or more pharmacy claims for a new HCP prescription during a 5-month period before or after the HCP schedule change were analyzed to determine member demographics (age, gender, and number of claims) and claim characteristics (average daily dose, average quantity per claim, and days supply). The rate of HCP claims increased before and decreased after the HCP schedule change. Controlling for the trend during the period before the HCP schedule change, the rate of HCP claims per 1,000 members per month decreased at a greater rate than non-HCP analgesics in the period after the HCP schedule change (P < 0.001). The percentage of HCP claims for new start members decreased after the HCP schedule change (44.9% vs. 34.1% of all HCP claims pre- to post-schedule change; P < 0.001). In the group of new starts, there was not a significant difference in the average daily dose (26.3 mg vs. 26.4 mg; P = 0.69), while there was a decrease in average number of tablets dispensed per claim (from 37.1 to 20.3 tablets; P < 0.001) and an increase in the percentage of claims for a shorter days supply (from 57.7% to 81.6%; P < 0.001). The findings of this study suggest that the HCP schedule change may have contributed to the decrease in claims for HCPs in a Medicaid population. After the HCP schedule change, there was a trend towards decreased HCP use among new starts. No outside funding supported this study. The authors have nothing to disclose. Study concept and design were contributed by all authors except for Arnold and Clements. Tran, Arnold, and Clements took the lead in data collection, along with Peristere, and data interpretation was performed by all the authors, except Arnold. The manuscript was written primarily by Tran, along with Lavitas, Stevens, and Greenwood, and revised by all the authors except Arnold and Peristere. A poster of this research project was presented at the Academy of Managed Care Pharmacy's 2016 Annual Meeting in San Francisco, California, April 2016.

Rheology and Extrusion of Cement-Fly Ashes Pastes

NASA Astrophysics Data System (ADS)

Micaelli, F.; Lanos, C.; Levita, G.

2008-07-01

The addition of fly ashes in cement pastes is tested to optimize the forming of cement based material by extrusion. Two sizes of fly ashes grains are examinated. The rheology of concentrated suspensions of ashes mixes is studied with a parallel plates rheometer. In stationary flow state, tested suspensions viscosities are satisfactorily described by the Krieger-Dougherty model. An "overlapped grain" suspensions model able to describe the bimodal suspensions behaviour is proposed. For higher values of solid volume fraction, Bingham viscoplastic behaviour is identified. Results showed that the plastic viscosity and plastic yield values present minimal values for the same optimal formulation of bimodal mixes. The rheological study is extended to more concentrated systems using an extruder. Finally it is observed that the addition of 30% vol. of optimized ashes mix determined a significant reduction of required extrusion load.

Study on temperature and damage sensing capability of Portland cement paste through the thermoelectric measurements

NASA Astrophysics Data System (ADS)

Hou, Tsung-Chin; Tai, Ko-Hung; Su, Yu-Min

2017-04-01

This study attempted to investigate the self-sensing capability of Portland cement composites in sensing temperature and detecting damages through the measurements of materials' thermoelectric properties. Specimens were made of Ordinary Portland Cement (OPC) with the water to cement ratio of 0.4. Temperature sensing property was characterized at various ages of the specimens from 28 to 49 days and at dried/moisturized conditions. It was found there exists an approximately linear relationship between temperature differences (ΔT) and the measured thermoelectric potentials, which is known as the Seebeck effect. This linearity was observed to be varied but able to be characterized for cement pastes at different ages and water saturation conditions. Mechanical loading that introduced different types and degrees of damages also translated into the variations of thermoelectric properties. Specifically, different types of compressive loads were tested for comparison. The study results have shown that Seebeck coefficient dropped with introduced damages, and restored with the subsequent re-curing as well as the continued cement hydration. Mild and moderate damages can be partially or fully restored, while severe damages that have resulted in significant drop of the Seebeck coefficients would restrain the self-restoration. Determination of the damage threshold was not yet revealed in this study, while it was shown obviously there existed one. Our investigation results indicated that characterizing the self-sensing capability of Portland cement composites is achievable through the measurements of thermoelectric properties. This study, in particular, has showcased the temperature sensing and damage detection capability.

Influence of triethanolamine on the hydration product of portlandite in cement paste and the mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan-Rong, Zhang; School of Civil Engineering, Beijing Key Laboratory of Track Engineering, Beijing Jiaotong University, Beijing 100044; Xiang-Ming, Kong

The influences of triethanolamine (TEA) on the portlandite in hardened cement pastes (HCPs) were systematically investigated. Results show that the addition of TEA in cement pastes leads to a visible reduction of Ca(OH){sub 2} (CH) content and considerably alters the morphology of CH crystals from large and parallel-stacked lamellar shape to smaller and distorted actinomorphic one. For the first time, the CH micro-crystals and even non-crystalline CH in HCPs were observed in the presence of TEA. Due to integration of CH micro-crystals in C–S–H phase, remarkable higher Ca/Si ratio of C–S–H phase was found. The formation of TEA-Ca{sup 2+} complexmore » via the interaction between Ca{sup 2+} and the oxygen atoms in TEA molecule was evidenced by the results of NMR and UV. It is believed that TEA can be introduced into the crystallization process of portlandite and thus significantly alters the morphology of CH crystals and even the content of the crystalline CH phase.« less

The impact of sulphate and magnesium on chloride binding in Portland cement paste

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Weerdt, K., E-mail: klaartje.d.weerdt@ntnu.no; SINTEF Building and Infrastructure, Trondheim; Orsáková, D.

2014-11-15

The effect of magnesium and sulphate present in sea water on chloride binding in Portland cement paste was investigated. Ground well hydrated cement paste was exposed to MgCl{sub 2}, NaCl, NaCl + MgCl{sub 2}, MgSO{sub 4} + MgCl{sub 2} and artificial sea water solutions with a range of concentrations at 20 °C. Chloride binding isotherms are determined and pH of the solutions were measured. A selection of samples was examined by SEM-EDS to identify phase changes upon exposure. The experimental data were compared with calculations of a thermodynamic model. Chloride binding from sea water was similar to chloride binding formore » NaCl solutions. The magnesium content in the sea water lead to a slight decrease in pH, but this did not result in a notable increase in chloride binding. The sulphate present in sea water reduces both chloride binding in C–S–H and AFm phases, as the C–S–H incorporates more sulphates instead of chlorides, and part of the AFm phases converts to ettringite.« less

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation.

PubMed

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-05-22

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures.

Micro- and nano-X-ray computed-tomography: A step forward in the characterization of the pore network of a leached cement paste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bossa, Nathan, E-mail: bossanathan@gmail.com; INERIS, Parc Technologique Alata, BP2, 60550 Verneuil-en-Halatte; iCEINT, CNRS, Duke Univ. International Consortium for the Environmental Implications of Nanotechnology, Aix-en-Provence

2015-01-15

Pore structure of leached cement pastes (w/c = 0.5) was studied for the first time from micro-scale down to the nano-scale by combining micro- and nano-X-ray computed tomography (micro- and nano-CT). This allowed assessing the 3D heterogeneity of the pore network along the cement profile (from the core to the altered layer) of almost the entire range of cement pore size, i.e. from capillary to gel pores. We successfully quantified an increase of porosity in the altered layer at both resolutions. Porosity is increasing from 1.8 to 6.1% and from 18 to 58% at the micro-(voxel = 1.81 μm) andmore » nano-scale (voxel = 63.5 nm) respectively. The combination of both CT allowed to circumvent weaknesses inherent of both investigation scales. In addition the connectivity and the channel size of the pore network were also evaluated to obtain a complete 3D pore network characterization at both scales.« less

Separability studies of construction and demolition waste recycled sand.

PubMed

Ulsen, Carina; Kahn, Henrique; Hawlitschek, Gustav; Masini, Eldon A; Angulo, Sérgio C

2013-03-01

The quality of recycled aggregates from construction and demolition waste (CDW) is strictly related to the content of porous and low strength phases, and specifically to the patches of cement that remain attached to the surface of natural aggregates. This phase increases water absorption and compromises the consistency and strength of concrete made from recycled aggregates. Mineral processing has been applied to CDW recycling to remove the patches of adhered cement paste on coarse recycled aggregates. The recycled fine fraction is usually disregarded due to its high content of porous phases despite representing around 50% of the total waste. This paper focus on laboratory mineral separability studies for removing particles with a high content of cement paste from natural fine aggregate particles (quartz/feldspars). The procedure achieved processing of CDW by tertiary impact crushing to produce sand, followed by sieving and density and magnetic separability studies. The attained results confirmed that both methods were effective in reducing cement paste content and producing significant mass recovery (80% for density concentration and 60% for magnetic separation). The production of recycled sand contributes to the sustainability of the construction environment by reducing both the consumption of raw materials and disposal of CDW, particularly in large Brazilian centers with a low quantity of sand and increasing costs of this material due to long transportation distances. Copyright © 2012 Elsevier Ltd. All rights reserved.

Magnesium-phosphate-glass cements with ceramic-type properties

DOEpatents

Sugama, T.; Kukacka, L.E.

1982-09-23

Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate, exhibits rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

Magnesium phosphate glass cements with ceramic-type properties

DOEpatents

Sugama, Toshifumi; Kukacka, Lawrence E.

1984-03-13

Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate exhibiting rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

Development of multi-walled carbon nanotubes reinforced monetite bionanocomposite cements for orthopedic applications.

PubMed

Boroujeni, Nariman Mansoori; Zhou, Huan; Luchini, Timothy J F; Bhaduri, Sarit B

2013-10-01

In this study, we present results of our research on biodegradable monetite (DCPA, CaHPO4) cement with surface-modified multi-walled carbon nanotubes (mMWCNTs) as potential bone defect repair material. The cement pastes showed desirable handling properties and possessed a suitable setting time for use in surgical setting. The incorporation of mMWCNTs shortened the setting time of DCPA and increased the compressive strength of DCPA cement from 11.09±1.85 MPa to 21.56±2.47 MPa. The cytocompatibility of the materials was investigated in vitro using the preosteoblast cell line MC3T3-E1. An increase of cell numbers was observed on both DCPA and DCPA-mMWCNTs. Scanning electron microscopy (SEM) results also revealed an obvious cell growth on the surface of the cements. Based on these results, DCPA-mMWCNTs composite cements can be considered as potential bone defect repair materials. © 2013.

Determining the slag fraction, water/binder ratio and degree of hydration in hardened cement pastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yio, M.H.N., E-mail: marcus.yio11@imperial.ac.uk; Phelan, J.C.; Wong, H.S.

2014-02-15

A method for determining the original mix composition of hardened slag-blended cement-based materials based on analysis of backscattered electron images combined with loss on ignition measurements is presented. The method does not require comparison to reference standards or prior knowledge of the composition of the binders used. Therefore, it is well-suited for application to real structures. The method is also able to calculate the degrees of reaction of slag and cement. Results obtained from an experimental study involving sixty samples with a wide range of water/binder (w/b) ratios (0.30 to 0.50), slag/binder ratios (0 to 0.6) and curing ages (3more » days to 1 year) show that the method is very promising. The mean absolute errors for the estimated slag, water and cement contents (kg/m{sup 3}), w/b and s/b ratios were 9.1%, 1.5%, 2.5%, 4.7% and 8.7%, respectively. 91% of the estimated w/b ratios were within 0.036 of the actual values. -- Highlights: •A new method for estimating w/b ratio and slag content in cement pastes is proposed. •The method is also able to calculate the degrees of reaction of slag and cement. •Reference standards or prior knowledge of the binder composition are not required. •The method was tested on samples with varying w/b ratios and slag content.« less

Corrosion of aluminium metal in OPC- and CAC-based cement matrices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinoshita, Hajime, E-mail: h.kinoshita@sheffield.ac.uk; Swift, Paul; Utton, Claire

Corrosion of aluminium metal in ordinary Portland cement (OPC) based pastes produces hydrogen gas and expansive reaction products causing problems for the encapsulation of aluminium containing nuclear wastes. Although corrosion of aluminium in cements has been long known, the extent of aluminium corrosion in the cement matrices and effects of such reaction on the cement phases are not well established. The present study investigates the corrosion reaction of aluminium in OPC, OPC-blast furnace slag (BFS) and calcium aluminate cement (CAC) based systems. The total amount of aluminium able to corrode in an OPC and 4:1 BFS:OPC system was determined, andmore » the correlation between the amount of calcium hydroxide in the system and the reaction of aluminium obtained. It was also shown that a CAC-based system could offer a potential matrix to incorporate aluminium metal with a further reduction of pH by introduction of phosphate, producing a calcium phosphate cement.« less

Reinforcement Strategies for Load-Bearing Calcium Phosphate Biocements

PubMed Central

Geffers, Martha; Groll, Jürgen; Gbureck, Uwe

2015-01-01

Calcium phosphate biocements based on calcium phosphate chemistry are well-established biomaterials for the repair of non-load bearing bone defects due to the brittle nature and low flexural strength of such cements. This article features reinforcement strategies of biocements based on various intrinsic or extrinsic material modifications to improve their strength and toughness. Altering particle size distribution in conjunction with using liquefiers reduces the amount of cement liquid necessary for cement paste preparation. This in turn decreases cement porosity and increases the mechanical performance, but does not change the brittle nature of the cements. The use of fibers may lead to a reinforcement of the matrix with a toughness increase of up to two orders of magnitude, but restricts at the same time cement injection for minimal invasive application techniques. A novel promising approach is the concept of dual-setting cements, in which a second hydrogel phase is simultaneously formed during setting, leading to more ductile cement–hydrogel composites with largely unaffected application properties.

Optimization and characterization of a cemented ultimate-storage product

NASA Astrophysics Data System (ADS)

Brunner, H.

1981-12-01

The U- and Pu-containing packaging wastes can be homogeneously cemented after a washing and fragmentation process. Both finely crushed and coarsely fragmented raw wastes yield products with sufficient mechanical stability. The processability limit of the coarsely fragmented raw waste using cement paste or mortar is largely determined by the cellulose content, which is not to exceed 1.3% by weight in the end waste. Of 9 binders studied, the most corrosion-resistant products were obtained with blast-furnace slag cement, whereas poured concrete and Maxit are much less resistant in five-component brine. In the cemented product, hydrolysis of plasticizers (DOP) from plastics (PVC) occurs, leading to release of 2-ethyl-hexanol. This reaction occurs to a much lower degree with blast-furnace slag cement than with all other binders studied. The binder chosen for further tests consists of blast-furnace slag cement, concrete fluidizer and a stabilizer, and is processed at a W/C ratio of 0.43.

Current advance care planning practice in the Australian community: an online survey of home care package case managers and service managers.

PubMed

Sellars, Marcus; Detering, Karen M; Silvester, William

2015-04-23

Advance care planning (ACP) is the process of planning for future healthcare that is facilitated by a trained healthcare professional, whereby a person's values, beliefs and treatment preferences are made known to guide clinical decision-making at a future time when they cannot communicate their decisions. Despite the potential benefits of ACP for community aged care clients the availability of ACP is unknown, but likely to be low. In Australia many of these clients receive services through Home Care Package (HCP) programs. This study aimed to explore current attitudes, knowledge and practice of advance care planning among HCP service managers and case managers. An invitation to take part in a cross-sectional online survey was distributed by email to all HCP services across Australia in November 2012. Descriptive analyses were used to examine overall patterns of responses to each survey item in the full sample. 120 (response rate 25%) service managers and 178 (response rate 18%) case managers completed the survey. Only 34% of services had written ACP policies and procedures in place and 48% of case managers had previously completed any ACP training. In addition, although most case managers (70%) had initiated an ACP discussion in the past 12 months and viewed ACP as part of their role, the majority of the conversations (80%) did not result in documentation of the client's wishes and most (85%) of the case managers who responded did not believe ACP was done well within their service. This survey shows low organisational ACP systems and support for case managers and a lack of a normative approach to ACP across Australian HCP services. As HCPs become more prevalent it is essential that a model of ACP is developed and evaluated in this setting, so that clients have the opportunity to discuss and document their future healthcare wishes if they choose to.

Promotion of health-enhancing physical activity in rheumatoid arthritis: a comparative study on healthcare providers in Italy, The Netherlands and Sweden.

PubMed

Brodin, Nina; Hurkmans, Emalie; DiMatteo, Luigi; Nava, Tiziana; Vliet Vlieland, Thea; Opava, Christina H

2015-10-01

The objectives of this study were to compare attitudes, practice of advice, perceived competencies and educational needs related to health-enhancing physical activity (HEPA) in rheumatoid arthritis (RA) among Dutch, Italian and Swedish healthcare providers (HCP) and to explore associations between these factors and age, gender and HEPA levels of HCP. Questionnaires were sent to 2939 HCP, members of their national rheumatology organizations. HEPA was assessed with the Short Questionnaire to Assess Health-Enhancing Physical Activity or the International Physical Activity Questionnaire; attitudes, practice of advice, perceived competencies and educational needs with a 23-item questionnaire. Overall response rate was 33 %. Ninety-five percent of HCP agreed that HEPA is an important health goal in RA. More Swedish HCP had positive attitudes to the attainability and safety of HEPA in RA. There were no differences between countries in practice of advice on HEPA to patients with RA in general or to those with recent onset disease, but more Italian HCP were reluctant to advise HEPA to patients with established disease. Of the total HCP, 36 to 60 % used public health guidelines to advise on HEPA, with Dutch HCP taking less advantage. Still they estimated a higher proportion of patients with RA to follow such advice. Italian HCP perceived their competencies the highest, but were also more interested in education to promote HEPA. Gender, age and HEPA performance had no association with attitudes toward HEPA, while a number of associations were found between these factors and practice of advice and perceived competencies. The differences found between HCP in the three countries might indicate the need for educational initiatives to improve HEPA promotion.

Improving the Accuracy of a Heliocentric Potential (HCP) Prediction Model for the Aviation Radiation Dose

NASA Astrophysics Data System (ADS)

Hwang, Junga; Yoon, Kyoung-Won; Jo, Gyeongbok; Noh, Sung-Jun

2016-12-01

The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs), flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP) prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA). However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015). In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1) real-time daily sunspot assessments, (2) predictions of the daily HCP by our prediction algorithm, and (3) calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

Hcp Family Proteins Secreted via the Type VI Secretion System Coordinately Regulate Escherichia coli K1 Interaction with Human Brain Microvascular Endothelial Cells

PubMed Central

Zhou, Yan; Tao, Jing; Yu, Hao; Ni, Jinjing; Zeng, Lingbing; Teng, Qihui; Kim, Kwang Sik; Zhao, Guo-Ping

2012-01-01

Type VI secretion systems (T6SSs) are involved in the pathogenicity of several Gram-negative bacteria. Based on sequence analysis, we found that a cluster of Escherichia coli virulence factors (EVF) encoding a putative T6SS exists in the genome of the meningitis-causing E. coli K1 strain RS218. The T6SS-associated deletion mutants exhibited significant defects in binding to and invasion of human brain microvascular endothelial cells (HBMEC) compared with the parent strain. Hcp family proteins (the hallmark of T6SS), including Hcp1 and Hcp2, were localized in the bacterial outer membrane, but the involvements of Hcp1 and Hcp2 have been shown to differ in E. coli-HBMEC interaction. The deletion mutant of hcp2 showed defects in the bacterial binding to and invasion of HBMEC, while Hcp1 was secreted in a T6SS-dependent manner and induced actin cytoskeleton rearrangement, apoptosis, and the release of interleukin-6 (IL-6) and IL-8 in HBMEC. These findings demonstrate that the T6SS is functional in E. coli K1, and two Hcp family proteins participate in different steps of E. coli interaction with HBMEC in a coordinate manner, e.g., binding to and invasion of HBMEC, the cytokine and chemokine release followed by cytoskeleton rearrangement, and apoptosis in HBMEC. This is the first demonstration of the role of T6SS in meningitis-causing E. coli K1, and T6SS-associated Hcp family proteins are likely to contribute to the pathogenesis of E. coli meningitis. PMID:22184413

Hcp family proteins secreted via the type VI secretion system coordinately regulate Escherichia coli K1 interaction with human brain microvascular endothelial cells.

PubMed

Zhou, Yan; Tao, Jing; Yu, Hao; Ni, Jinjing; Zeng, Lingbing; Teng, Qihui; Kim, Kwang Sik; Zhao, Guo-Ping; Guo, Xiaokui; Yao, Yufeng

2012-03-01

Type VI secretion systems (T6SSs) are involved in the pathogenicity of several gram-negative bacteria. Based on sequence analysis, we found that a cluster of Escherichia coli virulence factors (EVF) encoding a putative T6SS exists in the genome of the meningitis-causing E. coli K1 strain RS218. The T6SS-associated deletion mutants exhibited significant defects in binding to and invasion of human brain microvascular endothelial cells (HBMEC) compared with the parent strain. Hcp family proteins (the hallmark of T6SS), including Hcp1 and Hcp2, were localized in the bacterial outer membrane, but the involvements of Hcp1 and Hcp2 have been shown to differ in E. coli-HBMEC interaction. The deletion mutant of hcp2 showed defects in the bacterial binding to and invasion of HBMEC, while Hcp1 was secreted in a T6SS-dependent manner and induced actin cytoskeleton rearrangement, apoptosis, and the release of interleukin-6 (IL-6) and IL-8 in HBMEC. These findings demonstrate that the T6SS is functional in E. coli K1, and two Hcp family proteins participate in different steps of E. coli interaction with HBMEC in a coordinate manner, e.g., binding to and invasion of HBMEC, the cytokine and chemokine release followed by cytoskeleton rearrangement, and apoptosis in HBMEC. This is the first demonstration of the role of T6SS in meningitis-causing E. coli K1, and T6SS-associated Hcp family proteins are likely to contribute to the pathogenesis of E. coli meningitis.

Protecting Healthcare Personnel in Outpatient Settings: The Influence of Mandatory Versus Nonmandatory Influenza Vaccination Policies on Workplace Absenteeism During Multiple Respiratory Virus Seasons.

PubMed

Frederick, John; Brown, Alexandria C; Cummings, Derek A; Gaydos, Charlotte A; Gibert, Cynthia L; Gorse, Geoffrey J; Los, Jenna G; Nyquist, Ann-Christine; Perl, Trish M; Price, Connie S; Radonovich, Lewis J; Reich, Nicholas G; Rodriguez-Barradas, Maria C; Bessesen, Mary T; Simberkoff, Michael S

2018-04-01

OBJECTIVE To determine the effect of mandatory and nonmandatory influenza vaccination policies on vaccination rates and symptomatic absenteeism among healthcare personnel (HCP). DESIGN Retrospective observational cohort study. SETTING This study took place at 3 university medical centers with mandatory influenza vaccination policies and 4 Veterans Affairs (VA) healthcare systems with nonmandatory influenza vaccination policies. PARTICIPANTS The study included 2,304 outpatient HCP at mandatory vaccination sites and 1,759 outpatient HCP at nonmandatory vaccination sites. METHODS To determine the incidence and duration of absenteeism in outpatient settings, HCP participating in the Respiratory Protection Effectiveness Clinical Trial at both mandatory and nonmandatory vaccination sites over 3 viral respiratory illness (VRI) seasons (2012-2015) reported their influenza vaccination status and symptomatic days absent from work weekly throughout a 12-week period during the peak VRI season each year. The adjusted effects of vaccination and other modulating factors on absenteeism rates were estimated using multivariable regression models. RESULTS The proportion of participants who received influenza vaccination was lower each year at nonmandatory than at mandatory vaccination sites (odds ratio [OR], 0.09; 95% confidence interval [CI], 0.07-0.11). Among HCP who reported at least 1 sick day, vaccinated HCP had lower symptomatic days absent compared to unvaccinated HCP (OR for 2012-2013 and 2013-2014, 0.82; 95% CI, 0.72-0.93; OR for 2014-2015, 0.81; 95% CI, 0.69-0.95). CONCLUSIONS These data suggest that mandatory HCP influenza vaccination policies increase influenza vaccination rates and that HCP symptomatic absenteeism diminishes as rates of influenza vaccination increase. These findings should be considered in formulating HCP influenza vaccination policies. Infect Control Hosp Epidemiol 2018;39:452-461.

Research on curing behavior of concrete with anti-frost admixtures at subzero temperature

NASA Astrophysics Data System (ADS)

Ionov, Yulian; Kramar, Ludmila; Kirsanova, Alena; Kolegova, Irina

2017-01-01

The purpose of this paper is research on curing behavior of cold-weather concrete with anti-frost admixtures. During the study derivative thermal and X-ray phase analyses were performed and tests were carried out according to the standard GOST technique. The research results obtained reveal the peculiarities of cement hydration and concrete curing at subzero temperatures. The influence of subzero temperatures and anti-frost admixtures on hydrated phases of hardened cement paste and concrete strength formation was studied. It is found that cold-weather concrete does not cure at subzero temperatures, but when defrosting it attains 80 to 85% of its grade strength by the 28th day. Concrete achieves its grade strength when curing in normal conditions in 60 days only. Freezing concrete with anti-frost admixtures results in increase of calcium hydroxide content in hardened cement paste immediately when produced and has increased tendency of concrete to carbonation.

Ternary blends containing demercurated lighting phosphor and MSWI fly ash as high-performance binders for stabilizing and recycling electroplating sludge.

PubMed

Huang, Wu-Jang; Wu, Chia-Teng; Wu, Chang-En; Hsieh, Lin-Huey; Li, Chang-Chien; Lain, Chi-Yuan; Chu, Wei

2008-08-15

This paper describes the solidification and stabilization of electroplating sludge treated with a high-performance binder made from portland type-I cement, municipal solid waste incineration fly ash, and lighting phosphor powder (called as cement-fly ash-phosphor binder, CFP). The highest 28-day unconfined compressive strength of the CFP-treated paste was 816 kg/cm(2) at a ratio of cement to fly ash to lighting phosphor powder of 90:5:5; the strength of this composition also fulfilled the requirement of a high-strength concrete (>460 kg/cm(2) at 28 days). The CFP-stabilized sludge paste samples passed the Taiwanese EPA toxicity characteristic leaching procedure test and, therefore, could be used either as a building material or as a controlled low-strength material, depending on the sludge-to-CFP binder ratio.

Predictors of health care provider anticipatory guidance provision for older drivers.

PubMed

Huseth-Zosel, Andrea L; Sanders, Gregory; O'Connor, Melissa

2016-11-16

The objective of this study was to determine the frequency of health care provider (HCP) driving safety/cessation-related anticipatory guidance provision and predictors of driving safety-related anticipatory guidance provision by HCPs. HCPs in several central/upper Midwest states were surveyed about frequency of anticipatory guidance provision (n = 265). More than half of HCPs stated that they frequently or always provide driving safety/cessation-related anticipatory guidance to patients aged 85 or older, 38.7% provided this guidance to patients aged 75 to 84, and 13.7% to patients aged 65 to 74. Predictors of driving safety/cessation-related anticipatory guidance provision differed by patient age. For patients aged 65-74, HCP personal experience with a motor vehicle crash (either the HCP themselves or a friend/family member) was significant in predicting anticipatory guidance provision. However, for patients aged 75 and older, significant predictors included HCP rural practice, HCP age, and percentage of HCP patients who were older adults. HCP counseling provision related to driving issues differs by patient age and several HCP characteristics, including HCP rurality, age, and personal experience with motor vehicle crashes. Because aging results in physical and mental changes that affect driving and can be identified by HCPs, HCPs are in a position to counsel patients on the potential impacts of aging on the act of driving. Future research should examine the reasons for the differences in anticipatory guidance provision found in this study.

HcpR of Porphyromonas gingivalis Is Required for Growth under Nitrosative Stress and Survival within Host Cells

PubMed Central

Yanamandra, Sai S.; Anaya-Bergman, Cecilia

2012-01-01

Although the Gram-negative, anaerobic periodontopathogen Porphyromonas gingivalis must withstand nitrosative stress, which is particularly high in the oral cavity, the mechanisms allowing for protection against such stress are not known in this organism. In this study, microarray analysis of P. gingivalis transcriptional response to nitrite and nitric oxide showed drastic upregulation of the PG0893 gene coding for hybrid cluster protein (Hcp), which is a putative hydroxylamine reductase. Although regulation of hcp has been shown to be OxyR dependent in Escherichia coli, here we show that in P. gingivalis its expression is dependent on the Fnr-like regulator designated HcpR. Growth of the isogenic mutant V2807, containing an ermF-ermAM insertion within the hcpR (PG1053) gene, was significantly reduced in the presence of nitrite (P < 0.002) and nitric oxide-generating nitrosoglutathione (GSNO) (P < 0.001), compared to that of the wild-type W83 strain. Furthermore, the upregulation of PG0893 (hcp) was abrogated in V2807 exposed to nitrosative stress. In addition, recombinant HcpR bound DNA containing the hcp promoter sequence, and the binding was hemin dependent. Finally, V2807 was not able to survive with host cells, demonstrating that HcpR plays an important role in P. gingivalis virulence. This work gives insight into the molecular mechanisms of protection against nitrosative stress in P. gingivalis and shows that the regulatory mechanisms differ from those in E. coli. PMID:22778102

The relative energy of fcc and hcp foams

NASA Astrophysics Data System (ADS)

Whyte, D.; Weaire, D.; Drenckhan, W.; Hutzler, S.

2015-06-01

The energies of face-centred cubic (fcc) and hexagonal close-packed (hcp) monodisperse foams, associated with their total surface area, are equal in the wet and dry limits, in the usual model. We prove that for all intermediate values of liquid fraction, hcp has lower energy. Energy considerations are thus not sufficient to explain the observed preference for crystallization into fcc over hcp in experiments using monodisperse bubbles.

Limestone and Silica Powder Replacements for Cement: Early-Age Performance.

PubMed

Bentz, Dale P; Ferraris, Chiara F; Jones, Scott Z; Lootens, Didier; Zunino, Franco

2017-04-01

Developing functional concrete mixtures with less ordinary portland cement (OPC) has been one of the key objectives of the 21 st century sustainability movement. While the supplies of many alternatives to OPC (such as fly ash or slag) may be limited, those of limestone and silica powders produced by crushing rocks seem virtually endless. The present study examines the chemical and physical influences of these powders on the rheology, hydration, and setting of cement-based materials via experiments and three-dimensional microstructural modeling. It is shown that both limestone and silica particle surfaces are active templates (sites) for the nucleation and growth of cement hydration products, while the limestone itself is also somewhat soluble, leading to the formation of carboaluminate hydration products. Because the filler particles are incorporated as active members of the percolated backbone that constitutes initial setting of a cement-based system, replacements of up to 50 % of the OPC by either of these powders on a volumetric basis have minimal impact on the initial setting time, and even a paste with only 5 % OPC and 95 % limestone powder by volume achieves initial set within 24 h. While their influence on setting is similar, the limestone and silica powders produce pastes with quite different rheological properties, when substituted at the same volume level. When proceeding from setting to later age strength development, one must also consider the dilution of the system due to cement removal, along with the solubility/reactivity of the filler. However, for applications where controlled (prompt) setting is more critical than developing high strengths, such as mortar tile adhesives, grouts, and renderings, significant levels of these powder replacements for cement can serve as sustainable, functional alternatives to the oft-employed 100 % OPC products.

Hydration-dependent dynamics of water in calcium-silicate-hydrate: A QENS study by global model.

PubMed

Le, Peisi; Fratini, Emiliano; Chen, Sow-Hsin

2018-02-02

In a saturated cement paste, there are three different types of water: the structural water chemically reacted with cement, the constrained water absorbed to the surface of the pores, and the free water in the center of the pores. Each type has different physicochemical state and unique relation to cement porosity. The different water types have different dynamics which can be detected using quasi-elastic neutron scattering (QENS). Since the porosity of a hardened cement paste is impacted strongly by the water to cement ratio (w/c), it should be possible to extract the hydration dependence of the pores by exploiting the dynamical parameters of the confined water. Three C-S-H samples with different water levels, 8%, 17% and 30% were measured using QENS. The measurements were carried out in the scattering vector, Q, range from 0.5 Å -1 to 1.3 Å -1 , and in the temperature interval from 230 K to 280 K. The data were analyzed using a novel global model developed for cement QENS spectra. The results show that while increasing the water content, the structural water index (SWI) decreases and the confining radius, a, increases. Both SWI and a have a linear relationship with the water content. The Arrhenius plot of the translational relaxation time shows that the constrained water dominates the non-structural water at water contents lower than 17%. The rotational activation energy is smaller for lower water content. The analysis demonstrated that our newly proposed global model is practical and useful for analyzing cement QENS data. Copyright © 2018 Elsevier B.V. All rights reserved.

Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets.

PubMed

Lu, Liulei; Ouyang, Dong

2017-07-20

In this work, the effect of graphene oxide nanosheet (GONS) additives on the properties of cement mortar and ultra-high strength concrete (UHSC) is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0-0.03% by weight of cement). Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study.

Heavyweight cement concrete with high stability of strength parameters

NASA Astrophysics Data System (ADS)

Kudyakov, Konstantin; Nevsky, Andrey; Danke, Ilia; Kudyakov, Aleksandr; Kudyakov, Vitaly

2016-01-01

The present paper establishes regularities of basalt fibers distribution in movable cement concrete mixes under different conditions of their preparation and their selective introduction into mixer during the mixing process. The optimum content of basalt fibers was defined as 0.5% of the cement weight, which provides a uniform distribution of fibers in the concrete volume. It allows increasing compressive strength up to 51.2% and increasing tensile strength up to 28.8%. Micro-structural analysis identified new formations on the surface of basalt fibers, which indicates the good adhesion of hardened cement paste to the fibers. Stability of concrete strength parameters has significantly increased with introduction of basalt fibers into concrete mix.

Evaluation of super-water reducers for highway applications

NASA Astrophysics Data System (ADS)

Whiting, D.

1981-03-01

Super-water reducers were characterized and evaluated as potential candidates for production of low water to cement ratio, high strength concretes for highway construction applications. Admixtures were composed of either naphthalene or melamine sulfonated formaldehyde condensates. A mini-slump procedure was used to assess dosage requirements and behavior of workability with time of cement pastes. Required dosage was found to be a function of tricalcium aluminate content, alkali content, and fineness of the cement. Concretes exhibited high rates of slump loss when super-water reducers were used. The most promising area of application of these products appears to be in production of dense, high cement content concrete using mobile concrete mixer/transporters.

Effect of sodium monofluorophosphate treatment on microstructure and frost salt scaling durability of slag cement paste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Copuroglu, O.; Fraaij, A.L.A.; Bijen, J.M.J.M.

2006-08-15

Sodium-monofluorophosphate (Na-MFP) is currently in use as a surface applied corrosion inhibitor in the concrete industry. Its basic mechanism is to protect the passive layer of the reinforcement steel against disruption due to carbonation. Carbonation is known as the most detrimental environmental effect on blast furnace slag cement (BFSC) concrete with respect to frost salt scaling. In this paper the effect of Na-MFP on the microstructure and frost salt scaling resistance of carbonated BFSC paste is presented. The results of electron microscopy, mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD) are discussed. It is found that the treatment modifies themore » microstructure and improves the resistance of carbonated BFSC paste against frost salt attack.« less

Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report A : evaluation of HVFA cementitious paste and concrete mixtures.

DOT National Transportation Integrated Search

2012-10-01

In the Paste Screening Study, 25 combinations of five Type I/II portland cements : and five Class C fly ashes commonly used in Missouri were tested in paste form with no : chemical or powder additives. Testing procedures included semi-adiabatic calor...

Postexposure management of healthcare personnel to infectious diseases.

PubMed

Bader, Mazen S; Brooks, Annie A; Srigley, Jocelyn A

2015-01-01

Healthcare personnel (HCP) are at risk of exposure to various pathogens through their daily tasks and may serve as a reservoir for ongoing disease transmission in the healthcare setting. Management of HCP exposed to infectious agents can be disruptive to patient care, time-consuming, and costly. Exposure of HCP to an infectious source should be considered an urgent medical concern to ensure timely management and administration of postexposure prophylaxis, if available and indicated. Infection control and occupational health departments should be notified for management of exposed HCP, identification of all contacts of the index case, and application of immediate infection control measures for the index case and exposed HCP, if indicated. This article reviews the main principles of postexposure management of HCP to infectious diseases, in general, and to certain common infections, in particular, categorized by their route of transmission, in addition to primary prevention of these infections.

Prevaccination antibody screening and immunization program for healthcare personnel against measles, mumps, rubella, and varicella in a Japanese tertiary care hospital.

PubMed

Kanamori, Hajime; Tokuda, Koichi; Ikeda, Shinobu; Endo, Shiro; Ishizawa, Chiyuki; Hirai, Yukari; Takahashi, Masami; Aoyagi, Tetsuji; Hatta, Masumitsu; Gu, Yoshiaki; Yano, Hisakazu; Weber, David J; Kaku, Mitsuo

2014-10-01

Susceptible healthcare personnel (HCP) are at high risk for acquiring and transmitting measles, mumps, rubella, and varicella (MMRV). Presumptive evidence of immunity to MMRV is recommended for HCP. The aim of this investigation was to examine the seroprevalence of MMRV in Japanese HCP and the association with history or vaccination in terms of occupational safety. To improve infection control at our hospital, we also assessed their immune status by implementing prevaccination antibody screening and an immunization program with postvaccination serological testing. We implemented seroprevalence surveys on MMRV antibodies among 243 newly and 2,664 previously hired HCP in a Japanese tertiary care hospital. Self-administered questionnaires about history of MMRV and vaccination with or without written documentation were completed for newly hired HCP. Prevaccination and postvaccination serological tests were performed using virus-specific IgG enzyme-linked immunosorbent assays. Indeed, only a few HCP accurately remembered or had written records of their disease or vaccination history. After our immunization program was implemented, the seropositivity rate reached levels as high as ~98% for measles, rubella, and varicella, and increased to ~80% for mumps. Our program was cost-effective, and no severe adverse reactions were reported. The prevaccination antibody screening for HCP would be helpful, given the lack of written vaccination records or documented disease history, and is also useful for the prevention of adverse reactions associated with unnecessary vaccination. It is important for infection control practitioners to comprehend the immune status of HCP against MMRV, and then provide an appropriate immunization program for susceptible HCP.

Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties.

PubMed

Sun, Hongfang; Li, Zishanshan; Bai, Jing; Memon, Shazim Ali; Dong, Biqin; Fang, Yuan; Xu, Weiting; Xing, Feng

2015-02-13

Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)₂, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

Healthcare personnel perceptions of hand hygiene monitoring technology.

PubMed

Ellingson, Katherine; Polgreen, Philip M; Schneider, Amy; Shinkunas, Laura; Kaldjian, Lauris C; Wright, Donald; Thomas, Geb W; Segre, Alberto M; Herman, Ted; McDonald, L Clifford; Sinkowitz-Cochran, Ronda

2011-11-01

To assess healthcare personnel (HCP) perceptions regarding implementation of sensor-based electronic systems for automated hand hygiene adherence monitoring. Using a mixed-methods approach, structured focus groups were designed to elicit quantitative and qualitative responses on familiarity, comfort level, and perceived impact of sensor-based hand hygiene adherence monitoring. A university hospital, a Veterans Affairs hospital, and a community hospital in the Midwest. Focus groups were homogenous by HCP type, with separate groups held for leadership, midlevel management, and frontline personnel at each hospital. Overall, 89 HCP participated in 10 focus groups. Levels of familiarity and comfort with electronic oversight technology varied by HCP type; when compared with frontline HCP, those in leadership positions were significantly more familiar with ([Formula: see text]) and more comfortable with ([Formula: see text]) the technology. The most common concerns cited by participants across groups included lack of accuracy in the data produced, such as the inability of the technology to assess the situational context of hand hygiene opportunities, and the potential punitive use of data produced. Across groups, HCP had decreased tolerance for electronic collection of spatial-temporal data, describing such oversight as Big Brother. While substantial concerns were expressed by all types of HCP, participants' recommendations for effective implementation of electronic oversight technologies for hand hygiene monitoring included addressing accuracy issues before implementation and transparent communication with frontline HCP about the intended use of the data.

Deciphering mineralogical changes and carbonation development during hydration and ageing of a consolidated ternary blended cement paste

PubMed Central

Grangeon, Sylvain; De Nolf, Wout; Harker, Nicholas; Boulahya, Faiza; Bourbon, Xavier

2018-01-01

To understand the main properties of cement, a ubiquitous material, a sound description of its chemistry and mineralogy, including its reactivity in aggressive environments and its mechanical properties, is vital. In particular, the porosity distribution and associated sample carbonation, both of which affect cement’s properties and durability, should be quantified accurately, and their kinetics and mechanisms of formation known both in detail and in situ. However, traditional methods of cement mineralogy analysis (e.g. chemical mapping) involve sample preparation (e.g. slicing) that can be destructive and/or expose cement to the atmosphere, leading to preparation artefacts (e.g. dehydration). In addition, the kinetics of mineralogical development during hydration, and associated porosity development, cannot be examined. To circumvent these issues, X-ray diffraction computed tomography (XRD-CT) has been used. This allowed the mineralogy of ternary blended cement composed of clinker, fly ash and blast furnace slag to be deciphered. Consistent with previous results obtained for both powdered samples and dilute systems, it was possible, using a consolidated cement paste (with a water-to-solid ratio akin to that used in civil engineering), to determine that the mineralogy consists of alite (only detected in the in situ hydration experiment), calcite, calcium silicate hydrates (C-S-H), ettringite, mullite, portlandite, and an amorphous fraction of unreacted slag and fly ash. Mineralogical evolution during the first hydration steps indicated fast ferrite reactivity. Insights were also gained into how the cement porosity evolves over time and into associated spatially and time-resolved carbonation mechanisms. It was observed that macroporosity developed in less than 30 h of hydration, with pore sizes reaching about 100–150 µm in width. Carbonation was not observed for this time scale, but was found to affect the first 100 µm of cement located around macropores in a sample cured for six months. Regarding this carbonation, the only mineral detected was calcite. PMID:29765604

The effects of the mechanical–chemical stabilization process for municipal solid waste incinerator fly ash on the chemical reactions in cement paste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Cheng-Gang; Sun, Chang-Jung, E-mail: sun.3409@hotmail.com; Gau, Sue-Huai

2013-04-15

Highlights: ► Milling extracted MSWI fly ash. ► Increasing specific surface area, destruction of the crystalline texture, and increasing the amount of amorphous materials. ► Increasing heavy metal stability. ► Inducing pozzolanic reactions and increasing the early and later strength of the cement paste. - Abstract: A water extraction process can remove the soluble salts present in municipal solid waste incinerator (MSWI) fly ash, which will help to increase the stability of the synthetic materials produced from the MSWI fly ash. A milling process can be used to stabilize the heavy metals found in the extracted MSWI fly ash (EA)more » leading to the formation of a non-hazardous material. This milled extracted MSWI fly ash (MEA) was added to an ordinary Portland cement (OPC) paste to induce pozzolanic reactions. The experimental parameters included the milling time (96 h), water to binder ratios (0.38, 0.45, and 0.55), and curing time (1, 3, 7 and 28 days). The analysis procedures included inductively coupled plasma atomic emission spectroscopy (ICP/AES), BET, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) imaging. The results of the analyses indicate that the milling process helped to stabilize the heavy metals in the MEA, with an increase in the specific surface area of about 50 times over that of OPC. The addition of the MEA to the OPC paste decreased the amount of Ca(OH){sub 2} and led to the generation of calcium–silicate–hydrates (C–S–H) which in turned increased the amount of gel pores and middle sized pores in the cement. Furthermore, a comparison shows an increase in the early and later strength over that of OPC paste without the addition of the milled extracted ash. In other words, the milling process could stabilize the heavy metals in the MEA and had an activating effect on the MEA, allowing it to partly substitute OPC in OPC paste.« less

Polished sample preparing and backscattered electron imaging and of fly ash-cement paste

NASA Astrophysics Data System (ADS)

Feng, Shuxia; Li, Yanqi

2018-03-01

In recent decades, the technology of backscattered electron imaging and image analysis was applied in more and more study of mixed cement paste because of its special advantages. Test accuracy of this technology is affected by polished sample preparation and image acquisition. In our work, effects of two factors in polished sample preparing and backscattered electron imaging were investigated. The results showed that increasing smoothing pressure could improve the flatness of polished surface and then help to eliminate interference of morphology on grey level distribution of backscattered electron images; increasing accelerating voltage was beneficial to increase gray difference among different phases in backscattered electron images.

Weight loss of endodontic sealers, cements and pastes in water.

PubMed

Orstavik, D

1983-08-01

A solubility test based on weight loss in water, as proposed for standard testing programs (ADA & ISO), was adapted for assessing the solubility of 10 root canal sealers, cements and pastes. The weight loss of the set materials during 24 hr in distilled water at 37 degrees C ranged from -0.84 (AH26) to 22.71 (Kloroperka N-O) weight per cent. The results were reproducible, and the test was considered suitable for routine testing of weight loss in water of endodontic materials. However, the test may not provide information which is directly related to the clinical behavior of the materials.

Active mineral additives of sapropel ashes

NASA Astrophysics Data System (ADS)

Khomich, V. A.; Danilina, E. V.; Krivonos, O. I.; Plaksin, G. V.

2015-01-01

The goal of the presented research is to establish a scientific rational for the possibility of sapropel ashes usage as an active mineral additive. The research included the study of producing active mineral additives from sapropels by their thermal treatment at 850900 °C and afterpowdering, the investigation of the properties of paste matrix with an ash additive, and the study of the ash influence on the cement bonding agent. Thermogravimetric analysis and X-ray investigations allowed us to establish that while burning, organic substances are removed, clay minerals are dehydrated and their structure is broken. Sapropel ashes chemical composition was determined. An amorphous ash constituent is mainly formed from silica of the mineral sapropel part and alumosilicagels resulted from clay minerals decomposition. Properties of PC 400 and PC 500A0 sparopel ash additives were studied. Adding ashes containing Glenium plasticizer to the cement increases paste matrix strength and considerably reduces its water absorption. X-ray phase analysis data shows changes in the phase composition of the paste matrix with an ash additive. Ash additives produce a pozzolanic effect on the cement bonding agent. Besides, an ash additive due to the alumosilicagels content causes transformation from unstable calcium aluminate forms to the stable ones.

A probabilistic mechanical model for prediction of aggregates’ size distribution effect on concrete compressive strength

NASA Astrophysics Data System (ADS)

Miled, Karim; Limam, Oualid; Sab, Karam

2012-06-01

To predict aggregates' size distribution effect on the concrete compressive strength, a probabilistic mechanical model is proposed. Within this model, a Voronoi tessellation of a set of non-overlapping and rigid spherical aggregates is used to describe the concrete microstructure. Moreover, aggregates' diameters are defined as statistical variables and their size distribution function is identified to the experimental sieve curve. Then, an inter-aggregate failure criterion is proposed to describe the compressive-shear crushing of the hardened cement paste when concrete is subjected to uniaxial compression. Using a homogenization approach based on statistical homogenization and on geometrical simplifications, an analytical formula predicting the concrete compressive strength is obtained. This formula highlights the effects of cement paste strength and aggregates' size distribution and volume fraction on the concrete compressive strength. According to the proposed model, increasing the concrete strength for the same cement paste and the same aggregates' volume fraction is obtained by decreasing both aggregates' maximum size and the percentage of coarse aggregates. Finally, the validity of the model has been discussed through a comparison with experimental results (15 concrete compressive strengths ranging between 46 and 106 MPa) taken from literature and showing a good agreement with the model predictions.

Embedded NMR Sensor to Monitor Compressive Strength Development and Pore Size Distribution in Hydrating Concrete

PubMed Central

Díaz-Díaz, Floriberto; de J. Cano-Barrita, Prisciliano F.; Balcom, Bruce J.; Solís-Nájera, Sergio E.; Rodríguez, Alfredo O.

2013-01-01

In cement-based materials porosity plays an important role in determining their mechanical and transport properties. This paper describes an improved low–cost embeddable miniature NMR sensor capable of non-destructively measuring evaporable water loss and porosity refinement in low and high water-to-cement ratio cement-based materials. The sensor consists of two NdFeB magnets having their North and South poles facing each other, separated by 7 mm to allow space for a Faraday cage containing a Teflon tube and an ellipsoidal RF coil. To account for magnetic field changes due to temperature variations, and/or the presence of steel rebars, or frequency variation due to sample impedance, an external tuning circuit was employed. The sensor performance was evaluated by analyzing the transverse magnetization decay obtained with a CPMG measurement from different materials, such as a polymer phantom, fresh white and grey cement pastes with different w/c ratios and concrete with low (0.30) and high (0.6) w/c ratios. The results indicated that the sensor is capable of detecting changes in water content in fresh cement pastes and porosity refinement caused by cement hydration in hardened materials, even if they are prepared with a low w/c ratio (w/c = 0.30). The short lifetime component of the transverse relaxation rate is directly proportional to the compressive strength of concrete determined by destructive testing. The r2 (0.97) from the linear relationship observed is similar to that obtained using T2 data from a commercial Oxford Instruments 12.9 MHz spectrometer.

Lattice preferred orientation of hcp-iron induced by shear deformation

NASA Astrophysics Data System (ADS)

Nishihara, Y.; Ohuchi, T.; Kawazoe, T.; Maruyama, G.; Higo, Y.; Funakoshi, K. I.; Seto, Y.

2015-12-01

Many hypotheses have been proposed for origin of seismic anisotropy in the Earth's inner core which consists of solid metal. Plastic deformation of constituent material (most probably hexagonal-close-packed (hcp) iron) is one of the candidate processes to form the inner core anisotropy. Thus knowledge of deformation-induced lattice preferred orientation (LPO) of hcp-iron is important for understanding of nature of the inner core. In this study, we have carried out shear deformation experiments on hcp-iron and determined its deformation induced LPO. Since it is impossible to recover hcp-iron to ambient condition, both deformation and measurement of LPO have to be done at high-pressure conditions. Shear deformation experiments of hcp-iron were carried out using a deformation-DIA apparatus at high-pressure and high-temperature condition where hcp-iron is stable (9-18 GPa, 723 K). Development of LPO in the deforming sample was observed in-situ based on two-dimensional X-ray diffraction using an imaging plate detector and monochromatized synchrotron X-ray. In shear deformation of hcp-iron, <0001> and <112‾0> axes gradually aligned to be sub-parallel to shear plane normal and shear direction, respectively, from initial random orientation. The <0001> and <112‾0> axes are back-rotated from shear direction by 30°. The above results suggest basal slip <112‾0>{0001} is the dominant slip system under the studied deformation conditions. It has been shown that Earth's inner core has an axisymmetric anisotropy with P-wave traveling 3% faster along polar paths than along equatorial directions. Although elastic anisotropy of hcp-iron at the inner core conditions is still controversial, recent theoretical studies consistently shows that P-wave velocity of hcp-iron is fastest along <0001> direction at least at low-temperatures. Our experimental results could be suggesting that most part of the inner core deforms with shear plane sub-parallel to equatorial plane.

Thermal equation of state of hcp-iron: Constraint on the density deficit of Earth's solid inner core: THERMAL EQUATION OF STATE OF HCP-IRON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fei, Yingwei; Murphy, Caitlin; Shibazaki, Yuki

We conducted high-pressure experiments on hexagonal close packed iron (hcp-Fe) in MgO, NaCl, and Ne pressure-transmitting media and found general agreement among the experimental data at 300 K that yield the best fitted values of the bulk modulus K 0 = 172.7(±1.4) GPa and its pressure derivative K 0'= 4.79(±0.05) for hcp-Fe, using the third-order Birch-Murnaghan equation of state. Using the derived thermal pressures for hcp-Fe up to 100 GPa and 1800 K and previous shockwave Hugoniot data, we developed a thermal equation of state of hcp-Fe. The thermal equation of state of hcp-Fe is further used to calculate themore » densities of iron along adiabatic geotherms to define the density deficit of the inner core, which serves as the basis for developing quantitative composition models of the Earth's inner core. We determine the density deficit at the inner core boundary to be 3.6%, assuming an inner core boundary temperature of 6000 K.« less

Reconstructive structural phase transitions in dense Mg

NASA Astrophysics Data System (ADS)

Yao, Yansun; Klug, Dennis D.

2012-07-01

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied.

Reconstructive structural phase transitions in dense Mg.

PubMed

Yao, Yansun; Klug, Dennis D

2012-07-04

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied.

ToF-SIMS images and spectra of biomimetic calcium silicate-based cements after storage in solutions simulating the effects of human biological fluids

NASA Astrophysics Data System (ADS)

Torrisi, A.; Torrisi, V.; Tuccitto, N.; Gandolfi, M. G.; Prati, C.; Licciardello, A.

2010-01-01

ToF-SIMS images were obtained from a section of a tooth, obturated by means of a new calcium-silicate based cement (wTCF) after storage for 1 month in a saline solutions (DPBS), in order to simulate the body fluid effects on the obturation. Afterwards, ToF-SIMS spectra were obtained from model samples, prepared by using the same cement paste, after storage for 1 month and 8 months in two different saline solutions (DPBS and HBSS). ToF-SIMS spectra were also obtained from fluorine-free cement (wTC) samples after storage in HBSS for 1 month and 8 months and used for comparison. It was found that the composition of both the saline solution and the cement influenced the composition of the surface of disks and that longer is the storage greater are the differences. Segregation phenomena occur both on the cement obturation of the tooth and on the surface of the disks prepared by using the same cement. Indirect evidences of formation of new crystalline phases are supplied.

Analysis of risk factors to predict communicating hydrocephalus following gamma knife radiosurgery for intracranial schwannoma.

PubMed

Lee, Seunghoon; Seo, Seong-Wook; Hwang, Juyoung; Seol, Ho Jun; Nam, Do-Hyun; Lee, Jung-Il; Kong, Doo-Sik

2016-12-01

Communicating hydrocephalus (HCP) in vestibular schwannomas (VS) after gamma knife radiosurgery (GKRS) has been reported in the literature. However, little information about its incidence and risk factors after GKRS for intracranial schwannomas is yet available. The objective of this study was to identify the incidence and risk factors for developing communicating HCP after GKRS for intracranial schwannomas. We retrospectively reviewed a total of 702 patients with intracranial schwannomas who were treated with GKRS between January 2002 and December 2015. We investigated patients' age, gender, tumor origin, previous surgery history, tumor volume, marginal radiation dose, and presence of tumor control to identify associations with communicating HCP following GKRS. To make predictive models of communicating HCP, we performed Cox regression analyses and constructed a decision tree for risk factors. In total, 29 of the 702 patients (4.1%) developed communicating HCP following GKRS, which required ventriculo-peritoneal (VP) shunt surgery. Multivariate analyses indicated that age (P = 0.0011), tumor origin (P = 0.0438), and tumor volume (P < 0.0001) were significant predictors of communicating HCP in patients with intracranial schwannoma after GKRS. Using machine-learning methods, we fit an optimal predictive model. We found that developing communicating HCP following GKRS was most likely if the tumor was vestibular origin and had a volume ≥13.65 cm 3 . Communicating HCP is not a rare complication of GKRS for intracranial schwannomas. Under specific conditions, communicating HCP following GKRS is warranted for this patient group, and this patient group should be closely followed up. © 2016 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Constraints on Earth’s inner core composition inferred from measurements of the sound velocity of hcp-iron in extreme conditions

PubMed Central

Sakamaki, Tatsuya; Ohtani, Eiji; Fukui, Hiroshi; Kamada, Seiji; Takahashi, Suguru; Sakairi, Takanori; Takahata, Akihiro; Sakai, Takeshi; Tsutsui, Satoshi; Ishikawa, Daisuke; Shiraishi, Rei; Seto, Yusuke; Tsuchiya, Taku; Baron, Alfred Q. R.

2016-01-01

Hexagonal close-packed iron (hcp-Fe) is a main component of Earth’s inner core. The difference in density between hcp-Fe and the inner core in the Preliminary Reference Earth Model (PREM) shows a density deficit, which implies an existence of light elements in the core. Sound velocities then provide an important constraint on the amount and kind of light elements in the core. Although seismological observations provide density–sound velocity data of Earth’s core, there are few measurements in controlled laboratory conditions for comparison. We report the compressional sound velocity (VP) of hcp-Fe up to 163 GPa and 3000 K using inelastic x-ray scattering from a laser-heated sample in a diamond anvil cell. We propose a new high-temperature Birch’s law for hcp-Fe, which gives us the VP of pure hcp-Fe up to core conditions. We find that Earth’s inner core has a 4 to 5% smaller density and a 4 to 10% smaller VP than hcp-Fe. Our results demonstrate that components other than Fe in Earth’s core are required to explain Earth’s core density and velocity deficits compared to hcp-Fe. Assuming that the temperature effects on iron alloys are the same as those on hcp-Fe, we narrow down light elements in the inner core in terms of the velocity deficit. Hydrogen is a good candidate; thus, Earth’s core may be a hidden hydrogen reservoir. Silicon and sulfur are also possible candidates and could show good agreement with PREM if we consider the presence of some melt in the inner core, anelasticity, and/or a premelting effect. PMID:26933678

Sustainable Blended Cements-Influences of Packing Density on Cement Paste Chemical Efficiency.

PubMed

Knop, Yaniv; Peled, Alva

2018-04-18

This paper addresses the development of blended cements with reduced clinker amount by partial replacement of the clinker with more environmentally-friendly material (e.g., limestone powders). This development can lead to more sustainable cements with reduced greenhouse gas emission and energy consumption during their production. The reduced clicker content was based on improved particle packing density and surface area of the cement powder by using three different limestone particle diameters: smaller (7 µm, 3 µm) or larger (70 µm, 53 µm) than the clinker particles, or having a similar size (23 µm). The effects of the different limestone particle sizes on the chemical reactivity of the blended cement were studied by X-ray diffraction (XRD), thermogravimetry and differential thermogravimetry (TG/DTG), loss on ignition (LOI), isothermal calorimetry, and the water demand for reaching normal consistency. It was found that by blending the original cement with limestone, the hydration process and the reactivity of the limestone itself were increased by the increased surface area of the limestone particles. However, the carbonation reaction was decreased with the increased packing density of the blended cement with limestone, having various sizes.

Waste-Based Pervious Concrete for Climate-Resilient Pavements.

PubMed

Ho, Hsin-Lung; Huang, Ran; Hwang, Lih-Chuan; Lin, Wei-Ting; Hsu, Hui-Mi

2018-05-27

For the sake of environmental protection and circular economy, cement reduction and cement substitutes have become popular research topics, and the application of green materials has become an important issue in the development of building materials. This study developed green pervious concrete using water-quenched blast-furnace slag (BFS) and co-fired fly ash (CFFA) to replace cement. The objectives of this study were to gauge the feasibility of using a non-cement binder in pervious concrete and identify the optimal binder mix design in terms of compressive strength, permeability, and durability. For filled percentage of voids by cement paste (FPVs) of 70%, 80%, and 90%, which mixed with CFFA and BFS as the binder (40 + 60%, 50 + 50%, and 60 + 40%) to create pervious concrete with no cement. The results indicate that the complete (100%) replacement of cement with CFFA and BFS with no alkaline activator could induce hydration, setting, and hardening. After a curing period of 28 days, the compressive strength with different FPVs could reach approximately 90% that of the control cement specimens. The cementless pervious concrete specimens with BFS:CFFA = 7:3 and FPV = 90% presented better engineering properties and permeability.

Pressure-induced fcc to hcp phase transition in Ni-based high entropy solid solution alloys

DOE PAGES

Zhang, Fuxiang; Zhao, Shijun; Jin, Ke; ...

2017-01-04

In this research, pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure wasfound in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~ 40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fccmore » and the hcp phases for the three alloys are very small, but they are sensitive to temperature. Finally, the critical transition pressure in NiCoCrFe varies from 1 GPa at room temperature to 6 GPa at 500 K.« less

Pressure-induced fcc to hcp phase transition in Ni-based high entropy solid solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, F. X.; Zhao, Shijun; Jin, Ke

2017-01-04

A pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure was found in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fcc and themore » hcp phases for the three alloys are very small, but they are sensitive to temperature. The critical transition pressure in NiCoCrFe varies from ~1 GPa at room temperature to ~6 GPa at 500 K.« less

Hypothermic manipulation of bone cement can extend the handling time during vertebroplasty.

PubMed

Lai, Po-Liang; Tai, Ching-Lung; Chu, I-Ming; Fu, Tsai-Sheng; Chen, Lih-Huei; Chen, Wen-Jer

2012-10-16

Polymethylmethacrylate (PMMA) is commonly used for clinical applications. However, the short handling time increases the probability of a surgeon missing the crucial period in which the cement maintains its ideal viscosity for a successful injection. The aim of this article was to illustrate the effects a reduction in temperature would have on the cement handling time during percutaneous vertebroplasty. The injectability of bone cement was assessed using a cement compressor. By twisting the compressor, the piston transmits its axial load to the plunger, which then pumps the bone cement out. The experiments were categorized based on the different types of hypothermic manipulation that were used. In group I (room temperature, sham group), the syringes were kept at 22°C after mixing the bone cement. In group 2 (precooling the bone cement and the container), the PMMA powder and liquid, as well as the beaker, spatula, and syringe, were stored in the refrigerator (4°C) overnight before mixing. In group 3 (ice bath cooling), the syringes were immediately submerged in ice water after mixing the bone cement at room temperature. The average liquid time, paste time, and handling time were 5.1 ± 0.7, 3.4 ± 0.3, and 8.5 ± 0.8 min, respectively, for group 1; 9.4 ± 1.1, 5.8 ± 0.5, and 15.2 ± 1.2 min, respectively, for group 2; and 83.8 ± 5.2, 28.8 ± 6.9, and 112.5 ± 11.3 min, respectively, for group 3. The liquid and paste times could be increased through different cooling methods. In addition, the liquid time (i.e. waiting time) for ice bath cooling was longer than for that of the precooling method (p < 0.05). Both precooling (i.e. lowering the initial temperature) and ice bath cooling (i.e. lowering the surrounding temperature) can effectively slow polymerization. Precooling is easy for clinical applications, while ice bath cooling might be more suitable for multiple-level vertebroplasty. Clinicians can take advantage of the improved injectability without any increased cost.

Hypothermic manipulation of bone cement can extend the handling time during vertebroplasty

PubMed Central

2012-01-01

Background Polymethylmethacrylate (PMMA) is commonly used for clinical applications. However, the short handling time increases the probability of a surgeon missing the crucial period in which the cement maintains its ideal viscosity for a successful injection. The aim of this article was to illustrate the effects a reduction in temperature would have on the cement handling time during percutaneous vertebroplasty. Methods The injectability of bone cement was assessed using a cement compressor. By twisting the compressor, the piston transmits its axial load to the plunger, which then pumps the bone cement out. The experiments were categorized based on the different types of hypothermic manipulation that were used. In group I (room temperature, sham group), the syringes were kept at 22°C after mixing the bone cement. In group 2 (precooling the bone cement and the container), the PMMA powder and liquid, as well as the beaker, spatula, and syringe, were stored in the refrigerator (4°C) overnight before mixing. In group 3 (ice bath cooling), the syringes were immediately submerged in ice water after mixing the bone cement at room temperature. Results The average liquid time, paste time, and handling time were 5.1 ± 0.7, 3.4 ± 0.3, and 8.5 ± 0.8 min, respectively, for group 1; 9.4 ± 1.1, 5.8 ± 0.5, and 15.2 ± 1.2 min, respectively, for group 2; and 83.8 ± 5.2, 28.8 ± 6.9, and 112.5 ± 11.3 min, respectively, for group 3. The liquid and paste times could be increased through different cooling methods. In addition, the liquid time (i.e. waiting time) for ice bath cooling was longer than for that of the precooling method (p < 0.05). Conclusions Both precooling (i.e. lowering the initial temperature) and ice bath cooling (i.e. lowering the surrounding temperature) can effectively slow polymerization. Precooling is easy for clinical applications, while ice bath cooling might be more suitable for multiple-level vertebroplasty. Clinicians can take advantage of the improved injectability without any increased cost. PMID:23072273

Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets

PubMed Central

Ouyang, Dong

2017-01-01

In this work, the effect of graphene oxide nanosheet (GONS) additives on the properties of cement mortar and ultra-high strength concrete (UHSC) is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0–0.03% by weight of cement). Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study. PMID:28726750

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K

NASA Astrophysics Data System (ADS)

Dorogokupets, P. I.; Dymshits, A. M.; Litasov, K. D.; Sokolova, T. S.

2017-03-01

The equations of state for solid (with bcc, fcc, and hcp structures) and liquid phases of Fe were defined via simultaneous optimization of the heat capacity, bulk moduli, thermal expansion, and volume at room and higher temperatures. The calculated triple points at the phase diagram have the following parameters: bcc-fcc-hcp is located at 7.3 GPa and 820 K, bcc-fcc-liquid at 5.2 GPa and 1998 K, and fcc-hcp-liquid at 106.5 GPa and 3787 K. At conditions near the fcc-hcp-liquid triple point, the Clapeyron slope of the fcc-liquid curve is dT/dP = 12.8 K/GPa while the slope of the hcp-liquid curve is higher (dT/dP = 13.7 K/GPa). Therefore, the hcp-liquid curve overlaps the metastable fcc-liquid curve at pressures of about 160 GPa. At high-pressure conditions, the metastable bcc-hcp curve is located inside the fcc-Fe or liquid stability field. The density, adiabatic bulk modulus and P-wave velocity of liquid Fe calculated up to 328.9 GPa at adiabatic temperature conditions started from 5882 K (outer/inner core boundary) were compared to the PREM seismological model. We determined the density deficit of hcp-Fe at the inner core boundary (T = 5882 K and P = 328.9 GPa) to be 4.4%.

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K.

PubMed

Dorogokupets, P I; Dymshits, A M; Litasov, K D; Sokolova, T S

2017-03-06

The equations of state for solid (with bcc, fcc, and hcp structures) and liquid phases of Fe were defined via simultaneous optimization of the heat capacity, bulk moduli, thermal expansion, and volume at room and higher temperatures. The calculated triple points at the phase diagram have the following parameters: bcc-fcc-hcp is located at 7.3 GPa and 820 K, bcc-fcc-liquid at 5.2 GPa and 1998 K, and fcc-hcp-liquid at 106.5 GPa and 3787 K. At conditions near the fcc-hcp-liquid triple point, the Clapeyron slope of the fcc-liquid curve is dT/dP = 12.8 K/GPa while the slope of the hcp-liquid curve is higher (dT/dP = 13.7 K/GPa). Therefore, the hcp-liquid curve overlaps the metastable fcc-liquid curve at pressures of about 160 GPa. At high-pressure conditions, the metastable bcc-hcp curve is located inside the fcc-Fe or liquid stability field. The density, adiabatic bulk modulus and P-wave velocity of liquid Fe calculated up to 328.9 GPa at adiabatic temperature conditions started from 5882 K (outer/inner core boundary) were compared to the PREM seismological model. We determined the density deficit of hcp-Fe at the inner core boundary (T = 5882 K and P = 328.9 GPa) to be 4.4%.

The influence of alkalinity of portland cement on the absorption characteristics of superabsorbent polymers (SAP) for use in internally cured concrete

NASA Astrophysics Data System (ADS)

Tabares Tamayo, Juan D.

The concrete industry increasingly emphasizes advances in novel materials that promote construction of more resilient infrastructure. Due to its potential to improve concrete durability, internal curing (IC) of concrete by means of superabsorbent polymers (SAP) has been identified as one of the most promising technologies of the 21st century. The addition of superabsorbent polymers into a cementitious system promotes further hydration of cement by providing internal moisture during the hardening and strength development periods, and thus limits self-desiccation, shrinkage, and cracking. This thesis presents the work performed on the series of cement pastes with varying alkalinity of their pore solutions to provide a better understanding of: (1) the influence of the chemistry of the pore solution (i.e. its level of alkalinity and the type of ionic species present) on the absorption capacity of SAP, and (2) the effectiveness of SAP with different absorption capacities as an internal curing agent. This research work was divided into three stages: (a) materials characterization, (b) measurement of absorption capacity of SAP in synthetic pore solutions, and (c) evaluation of the internal curing effectiveness of SAP. During the first stage (Materials Characterization), pore solutions were extracted from the fresh (5 minutes old) cement pastes prepared using cements with three different levels of alkalinity. The pH values of the extracted solutions were determined (using the pH meter) and their chemical analysis was performed by means of titration (concentration of hydroxyl), ion chromatography (sulfates and chlorides), atomic absorption (AA) and inductively coupled plasma optical emission spectrometry (ICP) (sodium, potassium and calcium). The commercial SAP adopted for this study was used with "as-supplied" gradation and with the finer gradation obtained by grinding the original polymer in the 6850 Cryomilling Freezer/Mill. The physical properties of these SAP's, such as the shape and size of the particles, were determined by optical microscopy combined with image analysis. The second stage, the absorption capacity of SAP's, involved determination of the swelling behavior and the absorption capacity of polymers exposed to artificial pore solutions with different levels of alkalinity. The swelling behavior was followed using the optical microscope while the absorption capacity was characterized using the tea bag method. It was found that changes in the chemical compositions of the pore solutions influence the adsorption kinetics and result in different absorption isotherms. In the third stage, the internal curing effects of inclusion of SAP in cement pastes were evaluated. Mixture proportions of pastes used in this stage of the study were selected based on the absorption capacity of the SAP determined in stage two. The testing of the pastes involved determination of their set times, heat of hydration, and autogenous shrinkage.

Micromechanical performance of interfacial transition zone in fiber-reinforced cement matrix

NASA Astrophysics Data System (ADS)

Zacharda, V.; Němeček, J.; Štemberk, P.

2017-09-01

The paper investigates microstructure, chemical composition and micromechanical behavior of an interfacial transition zone (ITZ) in steel fiber reinforced cement matrix. For this goal, a combination of scanning electron microscopy (SEM), nanoindentation and elastic homogenization theory are used. The investigated sample of cement paste with dispersed reinforcement consists of cement CEM I 42,5R and a steel fiber TriTreg 50 mm. The microscopy revealed smaller portion of clinkers and larger porosity in the ITZ. Nanoindentation delivered decreased elastic modulus in comparison with cement bulk (67%) and the width of ITZ (∼ 40 μm). The measured properties served as input parameters for a simple two-scale model for elastic properties of the composite. Although, no major influence of ITZ properties on the composite elastic behavior was found, the findings about the ITZ reduced properties and its size can serve as input to other microstructural fracture based models.

Immediate impact on the rim zone of cement based materials due to chemical attack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwotzer, M., E-mail: matthias.schwotzer@kit.edu; Scherer, T.; Gerdes, A.

2015-01-15

Cement based materials are in their widespread application fields exposed to various aqueous environments. This can lead to serious chemical changes affecting the durability of the materials. In particular in the context of service life prediction a detailed knowledge of the reaction mechanisms is a necessary base for the evaluation of the aggressivity of an aqueous medium and this is deduced commonly from long term investigations. However, these processes start immediately at the material/water-interface, when a cementitious system comes into contact with an aqueous solution, altering here the chemical composition and microstructure. This rim zone represents the first hurdle thatmore » has to be overcome by an attacking aqueous solution. Therefore, the properties of the surface near area should be closely associated with the further course of deterioration processes by reactive transport. In this context short term exposure experiments with hardened cement paste over 4 and 48 h have been carried out with demineralized water, hard tap water and different sulfate solutions. In order to investigate immediate changes in the near-surface region, depth profile cuts have been performed on the cement paste samples by means of focused ion beam preparation techniques. A scanning beam of Gallium ions is applied to cut a sharp edge in the cement paste surface, providing insights into the composition and microstructure of the upper ten to hundred microns. Electron microscopic investigations on such a section of the rim zone, together with surface sensitive X-ray diffraction accompanied by a detailed characterization of the bulk composition confirm that the properties of the material/water interface are of relevance for the durability of cement based systems in contact with aqueous solutions. In this manner, focused ion beam investigations constitute auspicious tools to contribute to a more sophisticated understanding of the reaction mechanisms. - Highlights: • The chemical stability is related to the properties of material/water interface. • Properties of the rim zone readjust quickly, triggered by hydrochemical conditions. • Durability research can be improved by combining FIB techniques and common analytics.« less

Assessing Past Fracture Connectivity in Geothermal Reservoirs Using Clumped Isotopes: Proof of Concept in the Blue Mountain Geothermal Field, Nevada USA

NASA Astrophysics Data System (ADS)

Huntington, K. W.; Sumner, K. K.; Camp, E. R.; Cladouhos, T. T.; Uddenberg, M.; Swyer, M.; Garrison, G. H.

2015-12-01

Subsurface fluid flow is strongly influenced by faults and fractures, yet the transmissivity of faults and fractures changes through time due to deformation and cement precipitation, making flow paths difficult to predict. Here we assess past fracture connectivity in an active hydrothermal system in the Basin and Range, Nevada, USA, using clumped isotope geochemistry and cold cathodoluminescence (CL) analysis of fracture filling cements from the Blue Mountain geothermal field. Calcite cements were sampled from drill cuttings and two cores at varying distances from faults. CL microscopy of some of the cements shows banding parallel to the fracture walls as well as brecciation, indicating that the cements record variations in the composition and source of fluids that moved through the fractures as they opened episodically. CL microscopy, δ13C and δ18O values were used to screen homogeneous samples for clumped isotope analysis. Clumped isotope thermometry of most samples indicates paleofluid temperatures of around 150°C, with several wells peaking at above 200°C. We suggest that the consistency of these temperatures is related to upwelling of fluids in the convective hydrothermal system, and interpret the similarity of the clumped isotope temperatures to modern geothermal fluid temperatures of ~160-180°C as evidence that average reservoir temperatures have changed little since precipitation of the calcite cements. In contrast, two samples, one of which was associated with fault gauge observed in drill logs, record significantly cooler temperatures of 19 and 73°C and anomalous δ13C and δ18Owater values, which point to fault-controlled pathways for downwelling meteoric fluid. Finally, we interpret correspondence of paleofluid temperatures and δ18Owater values constrained by clumped isotope thermometry of calcite from different wells to suggest past connectivity of fractures among wells within the geothermal field. Results show the ability of clumped isotope geothermometry to assess fracture connectivity and geothermal reservoir characteristics in the past—with the potential to help optimize resource production and injection programs and better understand structural controls on mass and heat transfer in the subsurface.

Multiscale characterization of chemical–mechanical interactions between polymer fibers and cementitious matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernández-Cruz, Daniel; Hargis, Craig W.; Bae, Sungchul

2014-04-01

Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (lCT). Experimental results showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowedmore » visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars.« less

Effect of heavy metals and water content on the strength of magnesium phosphate cements.

PubMed

Buj, Irene; Torras, Josep; Casellas, Daniel; Rovira, Miquel; de Pablo, Joan

2009-10-15

In this paper the mechanical properties of magnesium potassium phosphate cements used for the Stabilization/Solidification (S/S) of galvanic wastes were investigated. Surrogate wastes (metal nitrate dissolutions) were employed containing Cd, Cr(III), Cu, Ni, Pb or Zn at a concentration of 25 g dm(-3) and different water-to-solid (W/S) ratios (0.3, 0.4, 0.5 and 0.6 dm(3)kg(-1)) have been employed. Cements were prepared by mixing hard burned magnesia of about 70% purity with potassium dihydrogen phosphate. Compressive strength and tensile strength of specimens were determined. In addition the volume of permeable voids was measured. It was found that when comparing pastes that the volume of permeable voids increases and mechanical strength decreases with the increase of water-to-solid ratio (W/S). Nevertheless pastes with the same material proportions containing different metals show different mechanical strength values. The hydration products were analyzed by XRD. With the increase of water content not previously reported hydration compound was detected: bobierrite.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tracy, Cameron L.; Park, Sulgiye; Rittman, Dylan R.

High pressure x-ray diffraction measurements reveal that the face-centered cubic (fcc) high-entropy alloy CrMnFeCoNi transforms martensitically to a hexagonal close-packed (hcp) phase at ~14 GPa. We attribute this to suppression of the local magnetic moments, destabilizing the fcc phase. Similar to fcc-to-hcp transformations in Al and the noble gases, this transformation is sluggish, occurring over a range of >40 GPa. But, the behavior of CrMnFeCoNi is unique in that the hcp phase is retained following decompression to ambient pressure, yielding metastable fcc-hcp mixtures.

Vanderbilt University Gamma Irradiation of Nano-modified Concrete (2017 Milestone Report)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deichert, Geoffrey G.; Linton, Kory D.; Terrani, Kurt A.

This document outlines the irradiation of concrete specimens in the Gamma Irradiation Facility in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). Two gamma irradiation runs were performed in July of 2017 on 18 reference mortar bar specimens, 26 reference cement paste bar specimens, and 28 reference cement paste tab specimens to determine the dose and temperature response of the specimens in the gamma irradiation environment. Specimens from the first two gamma irradiations were surveyed and released to Vanderbilt University. The temperature and dose information obtained informs the test parameters of the final two gamma irradiationsmore » of nano-modified concrete planned for FY 2018.« less

Improved microstructure of cement-based composites through the addition of rock wool particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Wei-Ting; Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan 32546, Taiwan; Cheng, An, E-mail: ancheng@niu.edu.tw

2013-10-15

Rock wool is an inorganic fibrous substance produced by steam blasting and cooling molten glass. As with other industrial by-products, rock wool particles can be used as cementitious materials or ultra fine fillers in cement-based composites. This study investigated the microstructure of mortar specimens produced with cement-based composites that include various forms of rock wool particles. It conducted compressive strength testing, rapid chloride penetration tests, X-ray diffraction analysis, thermo-gravimetric analysis, and scanning electronic microscopy to evaluate the macro- and micro-properties of the cement-based composites. Test results indicate that inclusion of rock wool particles in composites improved compressive strength and reducedmore » chloride ion penetration at the age of 91 days due to the reduction of calcium hydroxide content. Microscopic analysis confirms that the use of rock wool particles contributed to the formation of a denser, more compact microstructure within the hardened paste. In addition, X-ray diffraction analysis shows few changes in formation of pozzolanic reaction products and no new hydrations are formed with incorporating rock wool particles. - Highlights: • We report the microstructural characterization of cement-based composites. • Different mixes produced with various rock wool particles have been tested. • The influence of different mixes on macro and micro properties has been discussed. • The macro properties are included compressive strength and permeability. • XRD and SEM observations confirm the pozzolanic reaction in the resulting pastes.« less

Patient versus health care provider perspectives on spirituality and spiritual care: the potential to miss the moment.

PubMed

Selby, Debbie; Seccaraccia, Dori; Huth, Jim; Kurppa, Kristin; Fitch, Margaret

2017-04-01

Spirituality and spiritual care are well recognized as important facets of patient care, particularly in the palliative care population. Challenges remain, however, in the provision of such care. This study sought to compare patient and health care professional (HCP) views on spirituality/spiritual care, originally with a view to exploring a simple question(s) HCP's could use to identify spiritual distress, but evolved further to a comparison of how patients and HCPs were both concordant and discordant in their thoughts, and how this could lead to HCP's 'missing' opportunities to both identify spirituality/spiritual distress and to providing meaningful spiritual care. Patients (n=16) with advanced illnesses and HCP's (n=21) with experience providing care to those with advanced disease were interviewed using a semi-structured interview guide. Qualitative analysis distress and spiritual care, and screening for spiritual distress). Within each category there were areas of both concordance and discordance. Most notably, HCP's struggled to articulate definitions of spirituality whereas patients generally spoke with much more ease, giving rich examples. Equally, HCP's had difficulty relating stories of patients who had experienced spiritual distress while patients gave ready responses. Key areas where HCP's and patients differed were identified and set up the strong possibility for an HCP to 'miss the moment' in providing spiritual care. These key misses include the perception that spiritual care is simply not something they can provide, the challenge in defining/ recognizing spirituality (as HCP and patient definitions were often very different), and the focus on spiritual care, even for those interested in providing, as 'task oriented' often with emphasis on meaning making or finding purpose, whereas patients much more commonly described spiritual care as listening deeply, being present and helping them live in the moment. Several discrepancies in perception of spirituality, spiritual distress and spiritual care may hinder the ability of HCP's to effectively offer meaningful spiritual care. A focus on active listening, being led by the patient, and by providing presence may help limit the risk of a disconnect, or a 'miss', in the provision of spiritual care.

A new method to analyze copolymer based superplasticizer traces in cement leachates.

PubMed

Guérandel, Cyril; Vernex-Loset, Lionel; Krier, Gabriel; De Lanève, Michel; Guillot, Xavier; Pierre, Christian; Muller, Jean François

2011-03-15

Enhancing the flowing properties of fresh concrete is a crucial step for cement based materials users. This is done by adding polymeric admixtures. Such additives have enabled to improve final mechanicals properties and the development of new materials like high performance or self compacting concrete. Like this, the superplasticizers are used in almost cement based materials, in particular for concrete structures that can have a potential interaction with drinking water. It is then essential to have suitable detection techniques to assess whether these organic compounds are dissolved in water after a leaching process or not. The main constituent of the last generation superplasticizer is a PolyCarboxylate-Ester copolymer (PCE), in addition this organic admixture contains polyethylene oxide (free PEO) which constitutes a synthesis residue. Numerous analytical methods are available to characterize superplasticizer content. Although these techniques work well, they do not bring suitable detection threshold to analyze superplasticizer traces in solution with high mineral content such as leachates of hardened cement based materials formulated with superplasticizers. Moreover those techniques do not enable to distinguish free PEO from PCE in the superplasticizer. Here we discuss two highly sensitive analytical methods based on mass spectrometry suitable to perform a rapid detection of superplasticizer compounds traces in CEM I cement paste leachates: MALDI-TOF mass spectrometry, is used to determine the free PEO content in the leachate. However, industrial copolymers (such as PCE) are characterized by high molecular weight and polymolecular index. These two parameters lead to limitation concerning analysis of copolymers by MALDI-TOFMS. In this study, we demonstrate how pyrolysis and a Thermally assisted Hydrolysis/Methylation coupled with a triple-quadrupole mass spectrometer, provides good results for the detection of PCE copolymer traces in CEM I cement paste leachates. Copyright © 2011 Elsevier B.V. All rights reserved.

Fragile Reefs of the Eastern Pacific: Does low Cementation Provide a Model for Reefs in a High CO2 World?

NASA Astrophysics Data System (ADS)

Manzello, D.; Kleypas, J.; Eakin, M.; Budd, D.

2007-05-01

Around the world, reefs will experience high pCO2, low pH, low carbonate concentrations, and low aragonite saturation state as atmospheric CO2 rises. Ocean carbon chemistry measurements show that eastern Pacific waters already exist at high pCO2 and low carbonate concentrations due to natural upwelling in the region. Because of the upwelling, this region may serve as a model for coral reef development under enhanced atmospheric CO2 and oceanic pCO2; that is, low coral growth, low secondary cementation, and high physical, chemical, and biological erosion. Reefs in the eastern Pacific Ocean are characterized by low biological diversity and relatively small size. Both past coring and recent analysis reveal that, while many reefs in the eastern Pacific are several thousand years old, they are fragile and lack significant cementation, even in the innermost, oldest structures. They are also extremely porous with high water throughflow. Without secondary cementation, branching coral frameworks are held together only by organically produced calcium carbonate (e.g. coralline algae), sponges, and other reef infauna, and contain a high proportion of loose sediments. The result is reef frameworks that are more susceptible to destruction from mechanical or biological erosion. The poorly cemented nature of eastern Pacific reefs is thus hypothesized to have been a factor in the severe bioerosion that occurred on these reefs after past bleaching events (1982-3, 1997-8). We will present data that indicate low rates of cementation and high rates of erosion on eastern Pacific coral reefs and will compare current carbonate chemistry in the eastern Pacific to model predictions of what reefs around the globe may experience in coming decades.

Select host cell proteins coelute with monoclonal antibodies in protein A chromatography.

PubMed

Nogal, Bartek; Chhiba, Krishan; Emery, Jefferson C

2012-01-01

The most significant factor contributing to the presence of host cell protein (HCP) impurities in Protein A chromatography eluates is their association with the product monoclonal antibodies (mAbs) has been reported previously, and it has been suggested that more efficacious column washes may be developed by targeting the disruption of the mAbs-HCP interaction. However, characterization of this interaction is not straight forward as it is likely to involve multiple proteins and/or types of interaction. This work is an attempt to begin to understand the contribution of HCP subpopulations and/or mAb interaction propensity to the variability in HCP levels in the Protein A eluate. We performed a flowthrough (FT) recycling study with product respiking using two antibody molecules of apparently different HCP interaction propensities. In each case, the ELISA assay showed depletion of select subpopulations of HCP in Protein A eluates in subsequent column runs, while the feedstock HCP in the FTs remained unchanged from its native harvested cell culture fluid (HCCF) levels. In a separate study, the final FT from each molecule's recycling study was cross-spiked with various mAbs. In this case, Protein A eluate levels remained low for all but two molecules which were known as having high apparent HCP interaction propensity. The results of these studies suggest that mAbs may preferentially bind to select subsets of HCPs, and the degree of interaction and/or identity of the associated HCPs may vary depending on the mAb. Copyright © 2012 American Institute of Chemical Engineers (AIChE).

77 FR 46511 - Endangered and Threatened Wildlife and Plants; Receipt of Application for Incidental Take Permit...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-03

...: Written comments on the ITP application and HCP should be sent to the South Florida Ecological Services.... mail: Trish Adams, HCP Coordinator, South Florida Ecological Services Field Office, Attn: Permit number... INFORMATION CONTACT: Ms. Trish Adams, HCP Coordinator, South Florida Ecological Services Office, Vero Beach...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way.

PubMed

Chang, Honglei; Mu, Song

2017-11-21

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

Irradiated recycled plastic as a concrete additive for improved chemo-mechanical properties and lower carbon footprint.

PubMed

Schaefer, Carolyn E; Kupwade-Patil, Kunal; Ortega, Michael; Soriano, Carmen; Büyüköztürk, Oral; White, Anne E; Short, Michael P

2018-01-01

Concrete production contributes heavily to greenhouse gas emissions, thus a need exists for the development of durable and sustainable concrete with a lower carbon footprint. This can be achieved when cement is partially replaced with another material, such as waste plastic, though normally with a tradeoff in compressive strength. This study discusses progress toward a high/medium strength concrete with a dense, cementitious matrix that contains an irradiated plastic additive, recovering the compressive strength while displacing concrete with waste materials to reduce greenhouse gas generation. Compressive strength tests showed that the addition of high dose (100kGy) irradiated plastic in multiple concretes resulted in increased compressive strength as compared to samples containing regular, non-irradiated plastic. This suggests that irradiating plastic at a high dose is a viable potential solution for regaining some of the strength that is lost when plastic is added to cement paste. X-ray Diffraction (XRD), Backscattered Electron Microscopy (BSE), and X-ray microtomography explain the mechanisms for strength retention when using irradiated plastic as a filler for cement paste. By partially replacing Portland cement with a recycled waste plastic, this design may have a potential to contribute to reduced carbon emissions when scaled to the level of mass concrete production. Copyright © 2017 Elsevier Ltd. All rights reserved.

Engagement with Health Care Providers Affects Self- Efficacy, Self-Esteem, Medication Adherence and Quality of Life in People Living with HIV.

PubMed

Chen, Wei-Ti; Wantland, Dean; Reid, Paula; Corless, Inge B; Eller, Lucille S; Iipinge, Scholastika; Holzemer, William L; Nokes, Kathleen; Sefcik, Elizbeth; Rivero-Mendez, Marta; Voss, Joachim; Nicholas, Patrice; Phillips, J Craig; Brion, John M; Rose, Caro Dawson; Portillo, Carmen J; Kirksey, Kenn; Sullivan, Kathleen M; Johnson, Mallory O; Tyer-Viola, Lynda; Webel, Allison R

2013-11-01

The engagement of patients with their health care providers (HCP) improves patients' quality of life (QOL), adherence to antiretroviral therapy, and life satisfaction. Engagement with HCP includes access to HCP as needed, information sharing, involvement of client in decision making and self-care activities, respect and support of the HCP for the client's choices, and management of client concerns. This study compares country-level differences in patients' engagement with HCP and assesses statistical associations relative to adherence rates, self-efficacy, self-esteem, QOL, and symptom self-reporting by people living with HIV (PLHIV). A convenience sample of 2,182 PLHIV was enrolled in the United States, Canada, Puerto Rico, Namibia, and China. Cross-sectional data were collected between September 2009 and January 2011. Inclusion criteria were being at least 18 years of age, diagnosed with HIV, able to provide informed consent, and able to communicate in the local language with site researchers. In the HCP scale, a low score indicated greater provider engagement. Country comparisons showed that PLHIV in Namibia had the most HCP engagement (OR 2.80, p < 0.001) and that PLHIV in China had the least engagement (OR -7.03, p < 0.0001) compared to the PLHIV in the Western countries. Individuals having better HCP engagement showed better self-efficacy for adherence (t = -5.22, p < 0.0001), missed fewer medication doses (t = 1.92, p ≤ 0.05), had lower self-esteem ratings (t = 2.67, p < 0.01), fewer self-reported symptoms (t = 3.25, p < 0.0001), and better overall QOL physical condition (t = -3.39, p < 0.001). This study suggests that promoting engagement with the HCP is necessary to facilitate skills that help PLHIV manage their HIV. To improve ART adherence, HCPs should work on strategies to enhance self-efficacy and self-esteem, therefore, exhibiting fewer HIV-related symptoms and missing less medication doses to achieve better QOL.

The expected emotional benefits of influenza vaccination strongly affect pre-season intentions and subsequent vaccination among healthcare personnel.

PubMed

Thompson, Mark G; Gaglani, Manjusha J; Naleway, Allison; Ball, Sarah; Henkle, Emily M; Sokolow, Leslie Z; Brennan, Beth; Zhou, Hong; Foster, Lydia; Black, Carla; Kennedy, Erin D; Bozeman, Sam; Grohskopf, Lisa A; Shay, David K

2012-05-21

The relative importance of different attitudes in predicting vaccination among healthcare personnel (HCP) is unclear. We hypothesized that HCP who feel at risk without vaccination or say they would regret not getting vaccinated would be more likely to get vaccinated than HCP who do not expect these emotional benefits. A prospective cohort of 1544 HCP with direct patient care was enrolled from September 18 to December 18, 2010 at Scott & White Healthcare in Texas and Kaiser Permanente Northwest in Oregon and Washington. An Internet-based questionnaire assessed pre-season intention to be vaccinated and included 12 questions on attitudes about vaccination: single-item measures of perceived susceptibility and vaccine effectiveness, 5 items that were summed to form a concerns about vaccine scale, and 5 items summed to form an emotional benefits of vaccination scale. Influenza vaccination status for the 2010-2011 season and for 5 prior seasons was confirmed by medical record extraction. There were significant differences between vaccinated and unvaccinated HCP on all attitude items; 72% of vaccinated HCP agreed that they "worry less about getting the flu" if vaccinated, compared to only 26% of the unvaccinated (odds ratio=7.4, 95% confidence interval=5.8-9.5). In a multivariate model, the emotional benefits scale was the strongest predictor of 2010-2011 seasonal influenza vaccination, after adjusting for other attitude measures, prior vaccination history, and pre-season intention to be vaccinated. The predictive value of the emotional benefits scale was strongest for HCP with low pre-season intention to be vaccinated, where HCP vaccine receipt was 15% versus 83% for those with low versus high scores on the emotional benefits scale. The expected emotional benefits of vaccination strongly affect seasonal influenza vaccination among HCP, even after taking into account other attitudes, pre-season intentions, and prior vaccination history. These attitudes are promising targets for future vaccination campaigns. Published by Elsevier Ltd.

Investigating the job satisfaction of healthcare providers at primary healthcare centres in Lebanon: A national cross-sectional study.

PubMed

Alameddine, Mohamad; Baroud, Maysa; Kharroubi, Samer; Hamadeh, Randa; Ammar, Walid; Shoaib, Hikma; Khodr, Hiba

2017-11-01

Low job satisfaction is linked to higher staff turnover and intensified shortages in healthcare providers (HCP). This study investigates the level of, and factors associated with, HCP job satisfaction in the national primary healthcare (PHC) network in Lebanon. The study adopts a cross-sectional design to survey HCP at 99 PHC centres distributed across the country between October 2013 and May 2014. The study questionnaire consisted of four sections: socio-demographics/professional background, employment characteristics, level of job satisfaction (Measure of Job Satisfaction scale) and level of professional burnout (Maslach Burnout Inventory-HSS scale). A total of 1,000 providers completed the questionnaire (75.8% response rate). Bivariate and multivariate regression analyses were used to identify factors significantly associated with job satisfaction. Findings of the study highlight an overall mean job satisfaction score of 3.59 (SD 0.54) indicating that HCP are partially satisfied. Upon further examination, HCP were least satisfied with pay, training and job prospects. Gender, age, career plans, salary, exposure to violence, and level of burnout were significantly associated with the overall level of job satisfaction which was also associated with increased likelihood to quit. Overall, the study highlights how compensation, development and protection of PHC HCP can influence their job satisfaction. Recommendations include the necessity of developing a nationally representative committee, led by the Ministry of Public Health, to examine the policies and remuneration scales within the PHC sector and suggest mechanisms to bridge the pay differential with other sectors. The effective engagement of key stakeholders with the development, organisation and evaluation of professional development programmes offered to HCP in the PHC sector remains crucial. Concerned stakeholders should assess and formulate initiatives and programmes that enrich the physical, psychological and professional well-being of their HCP. The aforementioned suggestions are necessary to strengthen and sustain PHC HCP and support the provision of universal health coverage to the Lebanese population. © 2017 John Wiley & Sons Ltd.

Engagement with Health Care Providers Affects Self- Efficacy, Self-Esteem, Medication Adherence and Quality of Life in People Living with HIV

PubMed Central

Chen, Wei-Ti; Wantland, Dean; Reid, Paula; Corless, Inge B; Eller, Lucille S.; Iipinge, Scholastika; Holzemer, William L; Nokes, Kathleen; Sefcik, Elizbeth; Rivero-Mendez, Marta; Voss, Joachim; Nicholas, Patrice; Phillips, J. Craig; Brion, John M.; Rose, Caro Dawson; Portillo, Carmen J; Kirksey, Kenn; Sullivan, Kathleen M; Johnson, Mallory O; Tyer-Viola, Lynda; Webel, Allison R

2014-01-01

The engagement of patients with their health care providers (HCP) improves patients’ quality of life (QOL), adherence to antiretroviral therapy, and life satisfaction. Engagement with HCP includes access to HCP as needed, information sharing, involvement of client in decision making and self-care activities, respect and support of the HCP for the client’s choices, and management of client concerns. This study compares country-level differences in patients’ engagement with HCP and assesses statistical associations relative to adherence rates, self-efficacy, self-esteem, QOL, and symptom self-reporting by people living with HIV (PLHIV). A convenience sample of 2,182 PLHIV was enrolled in the United States, Canada, Puerto Rico, Namibia, and China. Cross-sectional data were collected between September 2009 and January 2011. Inclusion criteria were being at least 18 years of age, diagnosed with HIV, able to provide informed consent, and able to communicate in the local language with site researchers. In the HCP scale, a low score indicated greater provider engagement. Country comparisons showed that PLHIV in Namibia had the most HCP engagement (OR 2.80, p < 0.001) and that PLHIV in China had the least engagement (OR −7.03, p < 0.0001) compared to the PLHIV in the Western countries. Individuals having better HCP engagement showed better self-efficacy for adherence (t = −5.22, p < 0.0001), missed fewer medication doses (t = 1.92, p ≤ 0.05), had lower self-esteem ratings (t = 2.67, p < 0.01), fewer self-reported symptoms (t = 3.25, p < 0.0001), and better overall QOL physical condition (t = −3.39, p < 0.001). This study suggests that promoting engagement with the HCP is necessary to facilitate skills that help PLHIV manage their HIV. To improve ART adherence, HCPs should work on strategies to enhance self-efficacy and self-esteem, therefore, exhibiting fewer HIV-related symptoms and missing less medication doses to achieve better QOL. PMID:24575329

Critical temperature of the Ising ferromagnet on the fcc, hcp, and dhcp lattices

NASA Astrophysics Data System (ADS)

Yu, Unjong

2015-02-01

By an extensive Monte-Carlo calculation together with the finite-size-scaling and the multiple histogram method, the critical coupling constant (Kc = J /kBTc) of the Ising ferromagnet on the fcc, hcp, and double hcp (dhcp) lattices were obtained with unprecedented precision: Kcfcc= 0.1020707(2) , Kchcp= 0.1020702(1) , and Kcdhcp= 0.1020706(2) . The critical temperature Tc of the hcp lattice is found to be higher than those of the fcc and the dhcp lattice. The dhcp lattice seems to have higher Tc than the fcc lattice, but the difference is within error bars.

The sensitive and selective adsorption of aromatic compounds with highly crosslinked polymer nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Shuqin; Chen, Darui; Zheng, Juan; Zeng, Lewei; Jiang, Jijun; Jiang, Ruifeng; Zhu, Fang; Shen, Yong; Wu, Dingcai; Ouyang, Gangfeng

2015-10-01

This study presents the preparation and characterization of a nanoscale Davankov-type hyper-crosslinked-polymer (HCP) as an adsorbent of benzene-ring-containing dyes and organic pollutants. HCP nanoparticles post-crosslinked from a poly(DVB-co-VBC) precursor were synthesized in this study, possessing ultrahigh surface area, hydrophobicity and stability. The as-synthesized Davankov-type HCP exhibited a rapid and selective adsorption ability towards the benzene-ring-containing dyes due to its highly conjugated structure. Besides, for the first time, the prepared HCP nanoparticles were adopted for the adsorption of nonpolar organic pollutants by means of solid-phase microextraction (SPME). Owing to its high hydrophobicity, diverse pore size distribution and highly conjugated structure, a 10 μm HCP coating exhibited excellent adsorption abilities towards benzene-ring-containing polycyclic aromatic hydrocarbons (PAHs) and benzene series compounds (benzene, toluene, ethylbenzene and o-xylene; abbreviated to BTEX) and to highly hydrophobic long-chain n-alkanes. Finally, the HCP-nanoparticles-coated SPME fiber was applied to the simultaneous analysis of five PAHs in environmental water samples and satisfactory recoveries were achieved. The findings could provide a new benchmark for the exploitation of superb HCPs as effective adsorbents for SPME or other adsorption applications.This study presents the preparation and characterization of a nanoscale Davankov-type hyper-crosslinked-polymer (HCP) as an adsorbent of benzene-ring-containing dyes and organic pollutants. HCP nanoparticles post-crosslinked from a poly(DVB-co-VBC) precursor were synthesized in this study, possessing ultrahigh surface area, hydrophobicity and stability. The as-synthesized Davankov-type HCP exhibited a rapid and selective adsorption ability towards the benzene-ring-containing dyes due to its highly conjugated structure. Besides, for the first time, the prepared HCP nanoparticles were adopted for the adsorption of nonpolar organic pollutants by means of solid-phase microextraction (SPME). Owing to its high hydrophobicity, diverse pore size distribution and highly conjugated structure, a 10 μm HCP coating exhibited excellent adsorption abilities towards benzene-ring-containing polycyclic aromatic hydrocarbons (PAHs) and benzene series compounds (benzene, toluene, ethylbenzene and o-xylene; abbreviated to BTEX) and to highly hydrophobic long-chain n-alkanes. Finally, the HCP-nanoparticles-coated SPME fiber was applied to the simultaneous analysis of five PAHs in environmental water samples and satisfactory recoveries were achieved. The findings could provide a new benchmark for the exploitation of superb HCPs as effective adsorbents for SPME or other adsorption applications. Electronic supplementary information (ESI) available: Fig. S1-S8, details of optimization of the SPME condition, Tables S1-S5. See DOI: 10.1039/c5nr04624f

A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

PubMed Central

Jo, Byung-Wan; Chakraborty, Sumit

2015-01-01

To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite. PMID:25592665

On the mechanism of polypropylene fibres in preventing fire spalling in self-compacting and high-performance cement paste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X.; Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University, Technologiepark-Zwijnaarde 904 B-9052, Ghent; Ye, G.

2008-04-15

With the increasing application of self-compacting concrete (SCC) in construction and infrastructure, the fire spalling behavior of SCC has been attracting due attention. In high performance concrete (HPC), addition of polypropylene fibers (PP fibers) is widely used as an effective method to prevent explosive spalling. Hence, it would be useful to investigate whether the PP fibers are also efficient in SCC to avoid explosive spalling. However, no universal agreement exists concerning the fundamental mechanism of reducing the spalling risk by adding PP fiber. For SCC, the reduction of flowability should be considered when adding a significant amount of fibres. Inmore » this investigation, both the micro-level and macro-level properties of pastes with different fiber contents were studied in order to investigate the role of PP fiber at elevated temperature in self-compacting cement paste samples. The micro properties were studied by backscattering electron microscopy (BSE) and mercury intrusion porosimetry (MIP) tests. The modification of the pore structure at elevated temperature was investigated as well as the morphology of the PP fibers. Some macro properties were measured, such as the gas permeability of self-compacting cement paste after heating at different temperatures. The factors influencing gas permeability were analyzed. It is shown that with the melting of PP fiber, no significant increase in total pore volume is obtained. However, the connectivity of isolated pores increases, leading to an increase of gas permeability. With the increase of temperature, the addition of PP fibers reduces the damage of cement pastes, as seen from the total pore volume and the threshold pore diameter changes. From this investigation, it is concluded that the connectivity of pores as well as the creation of micro cracks are the major factors which determine the gas permeability after exposure to high temperatures. Furthermore, the connectivity of the pores acts as a dominant factor for temperatures below 300 deg. C. For higher temperatures micro cracks are becoming the major factor which influences the gas permeability.« less

Comparison of the magnetic properties of metastable hexagonal close-packed Ni nanoparticles with those of the stable face-centered cubic Ni nanoparticles.

PubMed

Jeon, Yoon Tae; Moon, Je Yong; Lee, Gang Ho; Park, Jeunghee; Chang, Yongmin

2006-01-26

We report the first magnetic study of pure and metastable hexagonal close-packed (hcp) Ni nanoparticles (sample 1). We also produced stable face-centered cubic (fcc) Ni nanoparticles, as mixtures with the hcp Ni nanoparticles (samples 2 and 3). We compared the magnetic properties of the hcp Ni nanoparticles with those of the fcc Ni nanoparticles by observing the evolution of magnetic properties from those of the hcp Ni nanoparticles to those of the fcc Ni nanoparticles as the number of fcc Ni nanoparticles increased from sample 1 to sample 3. The blocking temperature (T(B)) of the hcp Ni nanoparticles is approximately 12 K for particle diameters ranging between 8.5 and 18 nm, whereas those of the fcc Ni nanoparticles are 250 and 270 K for average particle diameters of 18 and 26 nm, respectively. The hcp Ni nanoparticles seem to be antiferromagnetic for T < T(B) and paramagnetic for T > T(B). This is very different from the fcc Ni nanoparticles, which are ferromagnetic for T < T(B) and superparamagnetic for T > T(B). This unusual magnetic state of the metastable hcp Ni nanoparticles is likely related to their increased bond distance (2.665 angstroms), compared to that (2.499 angstroms) of the stable fcc Ni nanoparticles.

Lost in translation? How adults living with Cystic Fibrosis understand treatment recommendations from their healthcare providers, and the impact on adherence to therapy.

PubMed

Pakhale, S; Baron, J; Armstrong, M; Tasca, G; Gaudet, E; Aaron, S D; Cameron, W; Balfour, L

2016-08-01

This study builds on the limited research documenting Cystic Fibrosis (CF) patients' understanding of treatment recommendations and how this may impact adherence to therapy. We surveyed adults with CF and their healthcare professional (HCP) to capture treatment recommendations provided by the HCP, and patients' knowledge, and frequency of performance, of these recommendations. We classified CF participants' understanding of treatment recommendations (correct/incorrect) as compared to the actual recommendations made by the HCP. We computed CF participants' adherence in relation to HCP treatment recommendations and to their own understanding of treatment recommendations (adherent/non-adherent). Complete HCP and patient data were available for 42 participants. The recommended treatment frequency was correctly understood by 0%-87.8% of CF participants. Adherence to HCP treatment recommendations ranged from 0 to 68.3% (mean 45.4%±21.5), and rates were low (<33%) for acapella, percussion/postural drainage, tobramycin nebulization and insulin. Participants' adherence was greater when calculated in relation to participants' understanding of treatment recommendations (62.4%±25.1) than when calculated in relation to actual HCP treatment recommendations (45.4%±21.5%) (p=0.009). Adults with CF misunderstand treatment recommendations; this likely affects treatment adherence. Interventions to ensure HCPs use effective communication strategies are needed. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Reduced prefrontal cortical gray matter volume in young adults exposed to harsh corporal punishment.

PubMed

Tomoda, Akemi; Suzuki, Hanako; Rabi, Keren; Sheu, Yi-Shin; Polcari, Ann; Teicher, Martin H

2009-08-01

Harsh corporal punishment (HCP) during childhood is a chronic, developmental stressor associated with depression, aggression and addictive behaviors. Exposure to traumatic stressors, such as sexual abuse, is associated with alteration in brain structure, but nothing is known about the potential neurobiological consequences of HCP. The aim of this study was to investigate whether HCP was associated with discernible alterations in gray matter volume (GMV) using voxel-based morphometry (VBM). 1455 young adults (18-25 years) were screened to identify 23 with exposure to HCP (minimum 3 years duration, 12 episodes per year, frequently involving objects) and 22 healthy controls. High-resolution T1-weighted MRI datasets were obtained using Siemens 3 T trio scanner. GMV was reduced by 19.1% in the right medial frontal gyrus (medial prefrontal cortex; MPFC, BA10) (P=0.037, corrected cluster level), by 14.5% in the left medial frontal gyrus (dorsolateral prefrontal cortex; DLPFC, BA9) (P=0.015, uncorrected cluster level) and by 16.9% in the right anterior cingulate gyrus (BA24) (P<0.001, uncorrected cluster level) of HCP subjects. There were significant correlations between GMV in these identified regions and performance IQ on the WAIS-III. Exposing children to harsh HCP may have detrimental effects on trajectories of brain development. However, it is also conceivable that differences in prefrontal cortical development may increase risk of exposure to HCP.

Recycling of porcelain tile polishing residue in portland cement: hydration efficiency.

PubMed

Pelisser, Fernando; Steiner, Luiz Renato; Bernardin, Adriano Michael

2012-02-21

Ceramic tiles are widely used by the construction industry, and the manufacturing process of ceramic tiles generates as a major residue mud derived from the polishing step. This residue is too impure to be reused in the ceramic process and is usually discarded as waste in landfills. But the analysis of the particle size and concentration of silica of this residue shows a potential use in the manufacture of building materials based on portland cement. Tests were conducted on cement pastes and mortars using the addition of 10% and 20% (mass) of the residue. The results of compressive strength in mortars made up to 56 days showed a significant increase in compressive strength greater than 50%. The result of thermogravimetry shows that portlandite is consumed by the cement formed by the silica present in the residue in order to form calcium silicate hydrate and featuring a pozzolanic reaction. This effect improves the performance of cement, contributes to research and application of supplementary cementitious materials, and optimizes the use of portland cement, reducing the environmental impacts of carbon dioxide emissions from its production.

Glass ionomer cements functionalised with a concentrated paste of chlorhexidine hexametaphosphate provides dose-dependent chlorhexidine release over at least 14 months.

PubMed

Bellis, Candice A; Nobbs, Angela H; O'Sullivan, Dominic J; Holder, James A; Barbour, Michele E

2016-02-01

The aim of this study was to create prototype glass ionomer cements (GICs) incorporating a concentrated paste of chlorhexidine-hexametaphosphate (CHX-HMP), and to investigate the long-term release of soluble chlorhexidine and the mechanical properties of the cements. The purpose is the design of a glass ionomer with sustained anticaries efficacy. CHX-HMP paste was prepared by mixing equimolar solutions of chlorhexidine digluconate and sodium hexametaphosphate, adjusting ionic strength, decanting and centrifuging. CHX-HMP paste was incorporated into a commercial GIC in substitution for glass powder at 0.00, 0.17, 0.34, 0.85 and 1.70% by mass CHX-HMP. Soluble chlorhexidine release into artificial saliva was observed over 436 days using absorbance at 255nm. Diametral tensile and compressive strength were measured after 7 days' setting (37°C, 100% humidity) and tensile strength after 436 days' aging in artificial saliva. 0.34% CHX-HMP GICs were tested for their ability to inhibit growth of Streptococcus mutans in vitro. GICs supplemented with CHX-HMP exhibited a sustained dose-dependent release of soluble chlorhexidine. Diametral tensile strength of new specimens was unaffected up to and including 0.85% CHX-HMP, and individual values of tensile strength were unaffected by aging, but the proportion of CHX-HMP required to adversely affect tensile strength was lower after aging, at 0.34%. Compressive strength was adversely affected by CHX-HMP at substitutions of 0.85% CHX-HMP and above. Supplementing a GIC with CHX-HMP paste resulted in a cement which released soluble chlorhexidine for over 14 months in a dose dependent manner. 0.17% and 0.34% CHX-HMP did not adversely affect strength at baseline, and 0.17% CHX-HMP did not affect strength after aging. 0.34% CHX-HMP GICs inhibited growth of S. mutans at a mean distance of 2.34mm from the specimen, whereas control (0%) GICs did not inhibit bacterial growth. Although GICs release fluoride in vivo, there is inconclusive evidence regarding any clinical anticaries effect. In this study, GICs supplemented with a paste of chlorhexidine-hexametaphosphate (CHX-HMP) exhibited a sustained release of chlorhexidine over at least 14 months, and small additions of CHX-HMP did not adversely affect strength. Copyright © 2016 Elsevier Ltd. All rights reserved.

Standing Posture at Work Does Not Increase the Risk of Varicose Veins among Health Care Providers in Taiwan

PubMed Central

Huang, Hsin-Kai; Weng, Shih-Feng; Su, Shih-Bin; Wang, Jhi-Joung; Guo, How-Ran; Hsu, Chien-Chin; Huang, Chien-Cheng; Lin, Hung-Jung

2017-01-01

Objective This study compared the risk of varicose veins (VV) among physicians, nonphysician health care providers (HCP), and the general population. Subjects and Methods The Taiwan National Health Insurance Research Database was used to identify 28,844 physicians and 26,099 nonphysician HCP and an identical number of age- and sex-matched patients from the general population. Using logistic regression analyses, VV risks between physicians and the general population, nonphysician HCP and the general population, and physicians and nonphysician HCP, and among physician specialists were compared by tracing their medical histories between 2007 and 2011. Results Physicians and nonphysician HCP had cumulative VV incidences of 0.12% (34/28,844) and 0.13% (33/26,099), respectively, during the 5-year period, compared to that of the general population within the same 5-year period. Physicians and nonphysician HCP did not have a higher VV risk than the general population after adjusting for deep vein thrombosis (DVT) history (adjusted odds ratio [AOR] 0.86; 95% confidence interval [CI] 0.53–1.40, and AOR 1.43; 95% CI 0.82–2.50, respectively). Physicians did not a have higher VV risk than nonphysician HCP (AOR 0.80; 95% CI 0.43–1.51) after adjusting for age, sex, and DVT history. Surgery had the highest incidence (0.22%) while pediatrics and emergency medicine had the lowest incidence (0%) of VV risk among physician specialists; however, the difference was not significant (all p values >0.05). Conclusion In this study, VV risk did not differ among physicians, nonphysician HCP, and the general population. PMID:28249260

Genetically encoded photochemical covalent crosslinking within the Hcp-1 self-assembling bacterial secretion machinery.

PubMed

Antonczak, Alicja K; Milholland, Kedric; Tippmann, Eric M

2018-05-01

The target protein, Hcp1, was first described as part of the bacterial Type VI secretion system from Pseudomonas aeruginosa. The protein first self-assembles into a hexamer and then the hexamers further stack into a nanotubular structure. Hcp1 monomers were targeted for mutagenesis with two widely used photoactivatable amino acids: para-benzoyl phenylalanine or para-azidophenylalanine. The ability of these amino acids to form covalent adducts within the Hcp1 self-assembled system was investigated. Multiple residues, putatively of equal distance between the monomer-monomer interface were targeted. The efficiency of each amino acid to covalently link self-assembled hexamers was determined. The results demonstrate the choice and role of genetically encoded tools applied to complicated biological processes such as self-assembly and also suggested some structural dynamics of the Hcp-1 protein not obvious from crystallographic structures.

Prevalence of use of advance directives, health care proxy, legal guardian, and living will in 512 patients hospitalized in a cardiac care unit/intensive care unit in 2 community hospitals.

PubMed

Kumar, Anil; Aronow, Wilbert S; Alexa, Margelusa; Gothwal, Ritu; Jesmajian, Stephen; Bhushan, Bharat; Gaba, Praveen; Catevenis, James

2010-04-30

The prevalence of use of any advance directives was 26% in 112 patients hospitalized in a cardiac care unit (CCU)/intensive care unit (ICU) in an academic medical center. We investigated in 2 community hospitals the prevalence of use of advance directives (AD), health care proxy (HCP), legal guardian (LG), and living will (LW) in 512 patients hospitalized in a CCU/ ICU approached for AD and HCP. The use of AD was 22%, of HCP was 19%, of LG was 16%, and of LW was 5%. The use of AD was 22%, of HCP was 19%, of LG was 16%, and of LW was 5% in patients hospitalized in a CCU/ICU. Educational programs on use of AD and of HCP need to be part of cardiovascular training programs and of cardiovascular continuing medical education.

Probing the defect nanostructure of helium and proton tracks in LiF:Mg,Ti using optical absorption: Implications to track structure theory calculations of heavy charged particle relative efficiency

NASA Astrophysics Data System (ADS)

Eliyahu, I.; Horowitz, Y. S.; Oster, L.; Weissman, L.; Kreisel, A.; Girshevitz, O.; Marino, S.; Druzhyna, S.; Biderman, S.; Mardor, I.

2015-04-01

A major objective of track structure theory (TST) is the calculation of heavy charged particle (HCP) induced effects. Previous calculations have been based exclusively on the radiation action/dose response of the released secondary electrons during the HCP slowing down. The validity of this presumption is investigated herein using optical absorption (OA) measurements on LiF:Mg,Ti (TLD-100) samples following irradiation with 1.4 MeV protons and 4 MeV He ions at levels of fluence from 1010 cm-2 to 2 × 1014 cm-2. The major bands in the OA spectrum are the 5.08 eV (F band), 4.77 eV, 5.45 eV and the 4.0 eV band (associated with the trapping structure leading to composite peak 5 in the thermoluminescence (TL) glow curve). The maximum intensity of composite peak 5 occurs at a temperature of ∼200 °C in the glow curve and is the glow peak used for most dosimetric applications. The TST calculations use experimentally measured OA dose response following low ionization density (LID) 60Co photon irradiation over the dose-range 10-105 Gy for the simulation of the radiation action of the HCP induced secondary electron spectrum. Following proton and He irradiation the saturation levels of concentration for the F band and the 4.77 eV band are approximately one order of magnitude greater than following LID irradiation indicating enhanced HCP creation of the relevant defects. Relative HCP OA efficiencies, ηHCP, are calculated by TST and are compared with experimentally measured values, ηm, at levels of fluence from 1010 cm-2 to 1011 cm-2 where the response is linear due to negligible track overlap. For the F band, values of ηm/ηHCP = 2.0 and 2.6 for the He ions and protons respectively arise from the neglect of enhanced Fluorine vacancy/F center creation by the HCPs in the TST calculations. It is demonstrated that kinetic analysis simulating LID F band dose response with enhanced Fluorine vacancy creation, and incorporated into the TST calculation, can lead to values of ηm = ηHCP. On the other hand, the values of ηm/ηHCP for the 4.0 eV band are much less than unity at 0.18 for the protons and <0.12 for the He ions. These very low values suggest that the 4.0 eV trapping structure is either destroyed or de-populated, perhaps by local heating/thermal spike/Coulomb explosion, during the HCP slowing down. These HCP induced processes are believed to be absent or greatly reduced during LID irradiation. The large deviations of ηm/ηHCP from unity for both the F band and especially the 4.0 eV band demonstrate that conventional TST which attempts to predict HCP induced radiation effects from the exclusive action of the released secondary electrons is woefully inadequate.

Predicting the Mineralogy of the HEDs and Vesta Using Both Meteoritic and Synthetic Samples

NASA Astrophysics Data System (ADS)

Mayne, R. G.; Lehman, K.

2012-12-01

Sample return missions are often viewed as the holy grail for planetary science. They enable us to directly correlate samples from the surface of their parent body with spacecraft data, greatly advancing our understanding of the relationship between the petrology and mineralogy of extraterrestrial materials and their corresponding spectra. The link between the Howardite-Eucrite-Diogenite (HED) group of meteorites and the asteroid Vesta provides us with one of the best opportunities for joint petrologic and spectral studies of an airless body. The HEDs can be seen as examples of many "natural" sample return missions. Terrestrial based studies of the HEDs can lead to improved data return from the Dawn mission, currently orbiting and analyzing Vesta. Pyroxenes dominate the HED spectra in the VISNIR region and, consequently, are the primary mineral that will be detected by the VIR instrument aboard Dawn. Previous studies have shown the importance of the high-Ca to low-Ca pyroxene ratio in spectral studies of asteroids, HCP/(HCP+LCP), hereafter referred to as HCP:LCP (Sunshine et al., 2004). This ratio is one of the few petrologic factors that can be predicted from VISNIR spectra and it can be used to indicate the amount of igneous differentiation that the measured surface or sample has undergone (Sunshine et al., 2004). The Modified Gaussian Model (Sunshine et al., 1990) allows to predict the HCP:LCP from spectra. The initial calibrations have been shown in several studies to predict the amount of HCP relative to LCP to within ±5-10 % (Sunshine and Pieters, 1993; Kanner et al., 2007), but for the eucrites this value was ±17 % (Mayne et al., 2010). This is likely because the current calibration for HCP:LCP was calculated using terrestrial composition pyroxene mixtures. The aim of this study is to improve current HCP:LCP calibrations for the HEDs and Vesta by using more Fe-rich, HED-like pyroxene compositions. Two eucrite composition end-member pyroxenes were synthesized by Donald Lindsley at SUNY-Stonybrook using the methods described in Turnock et al. (1973). The composition of the low- and high-Ca synthesized pyroxenes were Wo3.3En35.3Fs61.4 and Wo37.6En29.4Fs33.0 respectively. The pyroxenes were ground in an agate mortar and pestle and <45 μm powders were produced. These powders will be combined to produce a series of known mixtures: 100HCP; 75HCP:25LPC; 50HCP:50LCP; 25HCP:75LCP; 100LCP. The VISNIR (0.32-2.55 μm) spectra of each of these mixtures will be measured using the bidirectional reflectance spectrometer at the NASA/Keck Reflectance Equipment Laboratory (RELAB) at Brown University. The mixture spectra will be analyzed using MGM, with an aim of producing a calibration that allows the HCP:LCP to be accurately predicted for HED meteorites and Vesta. This calibration will be tested on eucrite spectra with a known HCP:LCP ratio from Mayne et al. (2010).

Using of borosilicate glass waste as a cement additive

NASA Astrophysics Data System (ADS)

Han, Weiwei; Sun, Tao; Li, Xinping; Sun, Mian; Lu, Yani

2016-08-01

Borosilicate glass waste is investigated as a cement additive in this paper to improve the properties of cement and concrete, such as setting time, compressive strength and radiation shielding. The results demonstrate that borosilicate glass is an effective additive, which not only improves the radiation shielding properties of cement paste, but also shows the irradiation effect on the mechanical and optical properties: borosilicate glass can increase the compressive strength and at the same time it makes a minor impact on the setting time and main mineralogical compositions of hydrated cement mixtures; and when the natural river sand in the mortar is replaced by borosilicate glass sand (in amounts from 0% to 22.2%), the compressive strength and the linear attenuation coefficient firstly increase and then decrease. When the glass waste content is 14.8%, the compressive strength is 43.2 MPa after 28 d and the linear attenuation coefficient is 0.2457 cm-1 after 28 d, which is beneficial for the preparation of radiation shielding concrete with high performances.

Physico-chemical mechanisms involved in the acceleration of the hydration of calcium sulfoaluminate cement by lithium ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cau Dit Coumes, Céline, E-mail: celine.cau-dit-coumes@cea.fr; Dhoury, Mélanie; Champenois, Jean-Baptiste

This work investigates the influence of lithium ions on the hydration at 25 °C of two calcium sulfoaluminate (CSA) cements comprising 0 or 10% gypsum. Small concentrations of lithium salts (LiOH, LiNO{sub 3}) accelerate the early hydration of both CSA cements either in paste or in diluted and stirred suspension. The effect of the lithium cation is much stronger than its counter-ion. Hydration is accelerated by an increase in the lithium concentration up to 30 μmol Li/g of the used CSA cement (with a high ye'elimite content), and then levels off. The postulated mechanism relies on a fast precipitation ofmore » amorphous Li-containing Al(OH){sub 3}, which acts as seeds for accelerating the precipitation of amorphous Al(OH){sub 3} that speeds up the whole hydration process. This process seems to be closely related to the one involved in the acceleration of the hydration of calcium aluminate cement by lithium ions.« less

High pressure synthesis of a hexagonal close-packed phase of the high-entropy alloy CrMnFeCoNi

DOE PAGES

Tracy, Cameron L.; Park, Sulgiye; Rittman, Dylan R.; ...

2017-05-25

High pressure x-ray diffraction measurements reveal that the face-centered cubic (fcc) high-entropy alloy CrMnFeCoNi transforms martensitically to a hexagonal close-packed (hcp) phase at ~14 GPa. We attribute this to suppression of the local magnetic moments, destabilizing the fcc phase. Similar to fcc-to-hcp transformations in Al and the noble gases, this transformation is sluggish, occurring over a range of >40 GPa. But, the behavior of CrMnFeCoNi is unique in that the hcp phase is retained following decompression to ambient pressure, yielding metastable fcc-hcp mixtures.

Metallic phases of cobalt-based catalysts in ethanol steam reforming: The effect of cerium oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Sean S.-Y.; Kim, Do Heui; Ha, Su Y.

2009-02-28

The catalytic activity of cobalt in the production of hydrogen via ethanol steam reforming has been investigated in its relation to the crystalline structure of metallic cobalt. At a reaction temperature of 350 8C, the specific hydrogen production rates show that hexagonal close-packed (hcp) cobalt possesses higher activity than face-centered cubic (fcc) cobalt. However, at typical reaction temperatures (400– 500 8C) for ethanol steam reforming, hcp cobalt is transformed to less active fcc cobalt, as confirmed by in situ X-ray diffractometry (XRD). The addition of CeO2 promoter (10 wt.%) stabilizes the hcp cobalt structure at reforming temperatures up to 600more » 8C. Moreover, during the pre-reduction process, CeO2 promoter prevents sintering during the transformation of Co3O4 to hcp cobalt. Both reforming experiments and in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the surface reactions were modified by CeO2 promoter on 10% Ce–Co (hcp) to give a lower CO selectivity and a higher H2 yield as compared with the unpromoted hcp Co.« less

Preparation of fly ash-granulated blast furnace slag-carbide slag binder and application in total tailings paste backfill

NASA Astrophysics Data System (ADS)

Li, Chao; Hao, Ya-fei; Zhao, Feng-qing

2018-03-01

Based on activation and synergistic effect among various materials, a low-cost mine backfill cementing material, FGC binder, was prepared by using fly ash, granulated blast-furnace slag (GBFS), carbide slag and composite activator. The proper proportioning of FGC binder is obtained by response surface experiment optimization method: fly ash 62 %, GBFS 20 %, carbide slag 8 % and compound activators 10 %. Adjusting the material ratio obtains different cementing material which could satisfy requirements of different mined-out areas. With the mass ratio of cementing material and tailings 1:4∼1:8, the concentration of total solid 70 %, the compressive strength values of total tailings filling body at 28 d reaches 1.64∼4.14 MPa, and the backfilling cost is 20 % lower than using OPC cement.

Microstructure of amorphous aluminum hydroxide in belite-calcium sulfoaluminate cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Fei; Yu, Zhenglei; Yang, Fengling

Belite-calcium sulfoaluminate (BCSA) cement is a promising low-CO{sub 2} alternative to ordinary Portland cement. Herein, aluminum hydroxide (AH{sub 3}), the main amorphous hydration product of BCSA cement, was investigated in detail. The microstructure of AH{sub 3} with various quantities of gypsum was investigated via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The AH{sub 3} with various morphologies were observed and confirmed in the resulting pastes. Particular attention was paid to the fact that AH{sub 3} always contained a small amount of Ca according to the results of EDS analysis. The AH{sub 3} was then characterized via highmore » resolution transmission electron microscopy (HRTEM). The results of HRTEM indicated that Ca arose from nanosized tricalcium aluminate hexahydrate which existed in the AH{sub 3}.« less

Peculiarities of hydration of Portland cement with synthetic nano-silica

NASA Astrophysics Data System (ADS)

Kotsay, Galyna

2017-12-01

Application of nano-materials in cement products significantly, improves their properties. Of course, the effectiveness of the materials depends on their quantity and the way they are introduced into the system. So far, amongst nano-materials used in construction, the most preferred was nano-silica. This research investigated the effect of synthetic precipitated nano-silica on the cement hydration as well as, on the physical and mechanical properties of pastes and mortars. Obtained results showed that admixture of nano-silica enhanced flexural and compressive strength of cement after 2 and 28 days, however, only when admixture made up 0.5% and 1.0%. On the other hand, the use of nano-silica in the amount 2% had some limitations, due to its ability to agglomerate, which resulted in deterioration of the rheological and mechanical properties.

Early containment of high-alkaline solution simulating low-level radioactive waste stream in clay-bearing blended cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruger, A.A.; Olson, R.A.; Tennis, P.D.

1995-04-01

Portland cement blended with fly ash and attapulgite clay was mixed with high-alkaline solution simulating low-level radioactive waste stream at a one-to-one weight ratio. Mixtures were adiabatically and isothermally cured at various temperatures and analyzed for phase composition, total alkalinity, pore solution chemistry, and transport properties as measured by impedance spectroscopy. Total alkalinity is characterized by two main drops. The early one corresponds to a rapid removal of phosphorous, aluminum, sodium, and to a lesser extent potassium solution. The second drop from about 10 h to 3 days is mainly associated with the removal of aluminum, silicon, and sodium. Thereafter,more » the total alkalinity continues descending, but at a lower rate. All pastes display a rapid flow loss that is attributed to an early precipitation of hydrated products. Hemicarbonate appears as early as one hour after mixing and is probably followed by apatite precipitation. However, the former is unstable and decomposes at a rate that is inversely related to the curing temperature. At high temperatures, zeolite appears at about 10 h after mixing. At 30 days, the stabilized crystalline composition Includes zeolite, apatite and other minor amounts of CaCO{sub 3}, quartz, and monosulfate Impedance spectra conform with the chemical and mineralogical data. The normalized conductivity of the pastes shows an early drop, which is followed by a main decrease from about 12 h to three days. At three days, the permeability of the cement-based waste as calculated by Katz-Thompson equation is over three orders of magnitude lower than that of ordinary portland cement paste. However, a further decrease in the calculated permeability is questionable. Chemical stabilization is favorable through incorporation of waste species into apatite and zeolite.« less

Ethnodrama: An Innovative Knowledge Translation Tool in the Management of Lymphedema.

PubMed

Ahmed, Shahid; Quinlan, Elizabeth; McMullen, Linda; Thomas, Roanne; Fichtner, Pam; Block, Janice

2015-01-01

Lymphedema can cause significant physical impairment and quality-of-life issues. Yet there is a gap in knowledge about lymphedema among breast cancer survivors (BCS), and health care professionals (HCP). Ethnodrama is an innovative knowledge translation strategy that uses theatrical performances for dissemination of research results. We evaluated the impact of live ethnodrama on HCP' and BCS' awareness and attitudes in relation to impact of lymphedema on BCS' lives. Ethnodrama performances were developed by script writers and a theatre director in collaboration with the investigators and BCS using data from published research and pre-performances workshops. Six interactive live performances were given to audiences of BCS, HCP, and community members in four cities across Canada. After watching these live performances, members of the audiences were asked to complete a paper-based questionnaire regarding their knowledge of lymphedema, and their attitudes and practices toward lymphedema. Of 238 audience members who participated in the survey, 55 (23%) were BCS and 85 (37.5%) were HCP. Most members rated the performances as very effective in changing their (84%) or other people's (93%) understanding of lymphedema; 96% reported being motivated to seek additional information on lymphedema, and 72% of HCP anticipated changes in their practices related to lymphedema screening. Overall no significant differences were noted in responses to ethnodrama between BCS and HCP. Open-ended responses were supportive of the findings from the closed-ended questions. Our results indicate that ethnodrama performances effectively convey information and positively affecting changes in HCP' and BCS' attitudes toward lymphedema.

Reduced Prefrontal Cortical Gray Matter Volume in Young Adults Exposed to Harsh Corporal Punishment

PubMed Central

Tomoda, Akemi; Suzuki, Hanako; Rabi, Keren; Sheu, Yi-Shin; Polcari, Ann; Teicher, Martin H.

2010-01-01

Objective Harsh corporal punishment (HCP) during childhood is a chronic, developmental stressor associated with depression, aggression and addictive behaviors. Exposure to traumatic stressors, such as sexual abuse, is associated with alteration in brain structure, but nothing is known about the potential neurobiological consequences of HCP. The aim of this study was to investigate whether HCP was associated with discernible alterations in gray matter volume (GMV) using voxel-based morphometry (VBM). Methods 1,455 young adults (18–25 years) were screened to identify 23 with exposure to HCP (minimum 3 years duration, 12 episodes per year, frequently involving objects) and 22 healthy controls. High-resolution T1-weighted MRI datasets were obtained using Siemens 3T trio scanner. Results GMV was reduced by 19.1% in the right medial frontal gyrus (medial prefrontal cortex; MPFC, BA10) (P = 0.037, corrected cluster level), by 14.5% in the left medial frontal gyrus (dorsolateral prefrontal cortex; DLPFC, BA 9) (P = 0.015, uncorrected cluster level) and by 16.9% in the right anterior cingulate gyrus (BA 24) (P < 0.001, uncorrected cluster level) of HCP subjects. There were significant correlations between GMV in these identified regions and performance IQ on the WAIS-III. Conclusions Exposing children to harsh HCP may have detrimental effects on trajectories of brain development. However, it is also conceivable that differences in prefrontal cortical development may increase risk of exposure to HCP. PMID:19285558

Role of calcium on chloride binding in hydrated Portland cement–metakaolin–limestone blends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Zhenguo; Geiker, Mette Rica; De Weerdt, Klaartje

Chloride binding is investigated for Portland cement–metakaolin–limestone pastes exposed to CaCl{sub 2} and NaCl solutions. The phase assemblages and the amount of Friedel's salt are evaluated using TGA, XRD and thermodynamic modeling. A larger amount of Friedel's salt is observed in the metakaolin blends compared to the pure Portland cement. A higher total chloride binding is observed for the pastes exposed to the CaCl{sub 2} solution relative to those in the NaCl solution. This is reflected by the fact that calcium increases the quantity of Friedel's salt in the metakaolin blends by promoting the transformation of strätlingite and/or monocarbonate tomore » Friedel's salt. Calcium increases also the amount of chloride in the diffuse layer of the C-S-H for the pure cement. A linear correlation between the total bound chloride and the uptake of calcium from the CaCl{sub 2} solution is obtained and found to be independent on the type of cement blend.« less

About the choice of Gibbs' potential for modelling of FCC ↔ HCP transformation in FeMnSi-based shape memory alloys

NASA Astrophysics Data System (ADS)

Evard, Margarita E.; Volkov, Aleksandr E.; Belyaev, Fedor S.; Ignatova, Anna D.

2018-05-01

The choice of Gibbs' potential for microstructural modeling of FCC ↔ HCP martensitic transformation in FeMn-based shape memory alloys is discussed. Threefold symmetry of the HCP phase is taken into account on specifying internal variables characterizing volume fractions of martensite variants. Constraints imposed on model constants by thermodynamic equilibrium conditions are formulated.

Nanoparticle-based concretes for the restoration of historical and contemporary buildings: a new way for CO2 reduction in architecture

NASA Astrophysics Data System (ADS)

Greco, Enrico; Ciliberto, Enrico; Verdura, Pietro Damiano; Lo Giudice, Elio; Navarra, Giuseppe

2016-05-01

The production of the cement is a highly energy-intensive process and contributes to the release of pollutants into the atmosphere due to both the chemical reactions occurring in the kiln and, in most cases, the burning of fossil fuels for power production. So, the reduction of the cement content in a concrete would be indirectly useful to decrease the pollutant emissions in the atmosphere. The results of our investigation indicate that the replacement levels of cement by the 4 % of nanoparticles show a positive increasing of many physical and chemical properties allowing a relevant saving of cement content inside a concrete mixture. The compressive strengths, tensile splitting, propagations of ultrasonic pulses and water permeability tests were investigated on different models and realistic structures by the ISO EN rules. The influence of the nanoparticles on physical and mechanical properties was measured at different ripening times. Both silica and iron oxides make cement pastes harder and accelerated hydration processes of the cements. A remarkable decreasing in water permeability was also observed showing that nanoconcretes can be used as innovative restoration systems for cement-based historical and contemporary artefacts in order to avoid carbonation processes. Moreover, a smaller quantity of cement binder inside the mortar causes relevant positive effects on the reduction of carbon dioxide emission in the atmosphere.

Utilization of the waste from the marble industry for application in transport infrastructure: mechanical properties of cement pastes

NASA Astrophysics Data System (ADS)

Prošek, Zdeněk; Trejbal, Jan; Topič, Jaroslav; Plachý, Tomáš; Tesárek, Pavel

2017-09-01

This article is focused on the mechanical testing of cement-based samples containing a micronized waste marble powder used as replacement of standard binders. Tested materials consisted of cement CEM I 42.5 R (Radotín, Czech Republic) and three different amounts of the marbles (25, 50 and 70 wt. %). Standard bending and compressive tests of the prismatic samples having dimensions equal to 40 × 40 × 160 mm were done in order to reveal an influence of marble amount on flexural and compressive strength, respectively. Moreover, the dynamic modulus of elasticity and dynamic shear modulus were examined and compared after 7 and 28 days of mixture curing.

Calcium Orthophosphate Cements and Concretes

PubMed Central

Dorozhkin, Sergey V.

2009-01-01

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone), calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

Effect of various Portland cement paste compositions on early-age strain

NASA Astrophysics Data System (ADS)

Guzzetta, Alana G.

Early-age strain in paste, mortar, and concrete mixtures was investigated using a new method where the specimen shape was a cone frustum. Strain of the specimen from both the horizontal and vertical directions was captured by height change measurement. The volumetric strain was then calculated as a function of the height change and was plotted versus time. A correlation was found between the slopes of the volumetric strain curve resulting from this test method and the initial setting time of the tested material. An initial evaluation of the repeatability of this innovative test method was conducted. The early-age strain effects of aggregate volume, shrinkage reducing admixture, water-cementitious ratio (w/cm), and partial cement replacement with supplementary cementitious materials were tested and individually compared. From these comparisons, it was observed that ambient temperature, bleed water development, and rheological properties had a significant impact on the volumetric strain results. Data showed increased strain as aggregate volume was reduced and as the w/cm was changed from 0.25 up to 0.50. The addition of shrinkage reducing admixture generally caused an increase in the 36-hour volumetric strain value. In most of the mixtures, cement replacement with 20% fly ash or 10% metakaolin reduced the measured volumetric strain when the w/cm was 0.30. Replacement of cement with 10% silica fume caused an insignificant change in volumetric strain results.

Fabrication and cytocompatibility of spherical magnesium ammonium phosphate granules.

PubMed

Christel, Theresa; Geffers, Martha; Klammert, Uwe; Nies, Berthold; Höß, Andreas; Groll, Jürgen; Kübler, Alexander C; Gbureck, Uwe

2014-09-01

Magnesium phosphate compounds, as for example struvite (MgNH4PO4·6H2O), have comparable characteristics to calcium phosphate bone substitutes, but degrade faster under physiological conditions. In the present work, we used a struvite forming calcium doped magnesium phosphate cement with the formulation Ca0.75Mg2.25(PO4)2 and an ammonium phosphate containing aqueous solution to produce round-shaped granules. For the fabrication of spherical granules, the cement paste was dispersed in a lipophilic liquid and stabilized by surfactants. The granules were characterized with respect to morphology, size distribution, phase composition, compressive strength, biocompatibility and solubility. In general, it was seen that small granules can hardly be produced by means of emulsification, when the raw material is a hydraulic paste, because long setting times promote coalescence of initially small unhardened cement droplets. Here, this problem was solved by using an aqueous solution containing both the secondary (NH4)2HPO4 and primary ammonium phosphates NH4H2PO4 to accelerate the setting reaction. This resulted in granules with 97 wt.% having a size in the range between 200 and 1,000 μm. The novel solution composition doubled the compressive strength of the cement to 37 ± 5 MPa without affecting either the conversion to struvite or the cytocompatibility using human fetal osteoblasts. Copyright © 2014 Elsevier B.V. All rights reserved.

Dynamical behaviors of structural, constrained and free water in calcium- and magnesium-silicate-hydrate gels

DOE PAGES

Le, Peisi; Fratini, Emiliano; Ito, Kanae; ...

2016-01-28

We present the hypothesis that the mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. With our experiments we investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. Wemore » measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison. We found that structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.« less

Dynamical behaviors of structural, constrained and free water in calcium- and magnesium-silicate-hydrate gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, Peisi; Fratini, Emiliano; Ito, Kanae

We present the hypothesis that the mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. With our experiments we investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. Wemore » measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison. We found that structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.« less

A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe-Mn-C system exhibiting multicomposition sets.

PubMed

Nakano, Jinichiro

2013-02-01

The thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. The stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T 0 , independent of the composition and temperature when other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T 0 . The driving force for the fcc to hcp transition, defined as a dimensionless value -d G m /( RT ), was determined in the presence of Fe-rich and Mn-rich composition sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the compositions studied. The results obtained revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.

Structural transition with thickness in films of poly-(styrene-b-2vinylpyridine) (PS-b-P2VP) diblock copolymer/homopolymer blends

NASA Astrophysics Data System (ADS)

Mishra, Vindhya; Kramer, Edward; Hur, Su-Mi; Fredrickson, Glenn; Sprung, Michael

2009-03-01

In multilayer thin films of spherical morphology block copolymers, the surface layers prefer hexagonal symmetry while the inner layers prefer BCC. Thin films with spherical morphology of PS-b-P2VP blends with short homopolymer polystyrene (hPS) chains have an HCP structure up to a thickness n* at which there is a transition to a face centered orthorhombic structure. Using grazing incidence small angle X-ray scattering and transmission electron microscopy we show that that n* increases from 5 to 9 with increase in hPS from 0 to 12 vol%. For thicknesses just below n* the HCP and FCO structures coexist, but on long annealing HCP prevails. We hypothesize that the PS segregates to the interstices in the HCP structure reducing the stretching of the PS blocks and the free energy penalty of HCP versus BCC inner layers. Self consistent field theoretic simulations are being carried out to see if this idea is correct.

Iron-Nickel alloy in the Earth's core

NASA Astrophysics Data System (ADS)

Lin, Jung-Fu; Heinz, Dion L.; Campbell, Andrew J.; Devine, James M.; Mao, Wendy L.; Shen, Guoyin

2002-05-01

The phase relations of an Fe10wt%Ni alloy were investigated in a diamond anvil cell up to 86 GPa and 2382 K. Adding nickel into iron stabilizes the fcc phase to higher pressures and lower temperatures compared to pure iron, and a region of two-phase coexistence between fcc and hcp phases is observed. Iron with up to 10 wt% nickel is likely to be in the hcp structure under inner core conditions. The axial ratio (c/a) of hcp-Fe10wt%Ni has a weak pressure dependence, but it increases substantially with increasing temperature. The extrapolated c/a ratio at ~5700 K and ~86 GPa is approximately 1.64, lower than a theoretically predicted value of nearly 1.7 for hcp-Fe at 5700 K and inner-core pressure. A lower c/a ratio should have an effect on the longitudinal anisotropy of the hcp phase, and hence, may influence the interpretation of the seismic wave anisotropy of the inner core.

Anti-bacterial and anti-inflammatory effects of ethanol extract from Houttuynia cordata poultice.

PubMed

Sekita, Yasuko; Murakami, Keiji; Yumoto, Hiromichi; Mizuguchi, Hiroyuki; Amoh, Takashi; Ogino, Satoshi; Matsuo, Takashi; Miyake, Yoichiro; Fukui, Hiroyuki; Kashiwada, Yoshiki

2016-06-01

Houttuynia cordata (HC) has been commonly used as many traditional remedies in local areas of Japan. Although many pharmacological activities of HC have been reported, the mechanism underlying the effect of HC remains unknown. We conducted the interview survey in Japan to verify how HC was actually used. The interview survey revealed that HC poultice (HCP) prepared from smothering fresh leaves of HC was most frequently used for the treatment of purulent skin diseases including furuncle and carbuncle with high effectiveness. Ethanol extract of HCP (eHCP) showed anti-bacterial effects against methicillin-resistant Staphylococcus aureus (MRSA), and showed an anti-biofilm activity against MRSA. eHCP showed dose-dependent inhibition of S. aureus lipoteichoic acid (LTA)-induced interleukin-8 and CCL20 production in human keratinocyte without any cytotoxicity. These results suggest that HCP is effective for skin abscess and its underlying mechanism might be the complicated multiple activities for both bacteria and host cells.

Controlled growth of hexagonal gold nanostructures during thermally induced self-assembling on Ge(001) surface

PubMed Central

Jany, B. R.; Gauquelin, N.; Willhammar, T.; Nikiel, M.; van den Bos, K. H. W.; Janas, A.; Szajna, K.; Verbeeck, J.; Van Aert, S.; Van Tendeloo, G.; Krok, F.

2017-01-01

Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. Gold crystallizes in the face-centered cubic (fcc) phase, and its hexagonal closed packed (hcp) structure is a very unusual and rare phase. Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium. PMID:28195226

Controlled growth of hexagonal gold nanostructures during thermally induced self-assembling on Ge(001) surface

NASA Astrophysics Data System (ADS)

Jany, B. R.; Gauquelin, N.; Willhammar, T.; Nikiel, M.; van den Bos, K. H. W.; Janas, A.; Szajna, K.; Verbeeck, J.; van Aert, S.; van Tendeloo, G.; Krok, F.

2017-02-01

Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. Gold crystallizes in the face-centered cubic (fcc) phase, and its hexagonal closed packed (hcp) structure is a very unusual and rare phase. Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium.

Lattice dynamics and metastability of fcc metals in the hcp structure and the crucial role of spin-orbit coupling in platinum

NASA Astrophysics Data System (ADS)

Schönecker, Stephan; Li, Xiaoqing; Richter, Manuel; Vitos, Levente

2018-06-01

We investigate the lattice dynamical properties of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au in the nonequilibrium hcp structure by means of density-functional simulations, wherein spin-orbit coupling (SOC) was considered for Ir, Pt, and Au. The determined dynamical properties reveal that all eight elements possess a metastable hcp phase at zero temperature and pressure. The hcp Ni, Cu, Rh, Pd, and Au previously observed in nanostructures support this finding. We make evident that the inclusion of SOC is mandatory for an accurate description of the phonon dispersion relations and dynamical stability of hcp Pt. The underlying sensitivity of the interatomic force constants is ascribed to a SOC-induced splitting of degenerate band states accompanied by a pronounced reduction of electronic density of states at the Fermi level. To give further insight into the importance of SOC in Pt, we (i) focus on phase stability and examine a lattice transformation related to optical phonons in the hcp phase and (ii) focus on the generalized stacking fault energy (GSFE) of the fcc phase pertinent to crystal plasticity. We show that the intrinsic stable and unstable fault energies of the GSFE scale as in other common fcc metals, provided that the spin-orbit interaction is taken into account.

Structural characterization and immunomodulatory effect of a polysaccharide HCP-2 from Houttuynia cordata.

PubMed

Cheng, Bao-Hui; Chan, Judy Yuet-Wa; Chan, Ben Chung-Lap; Lin, Huang-Quan; Han, Xiao-Qiang; Zhou, Xuelin; Wan, David Chi-Cheong; Wang, Yi-Fen; Leung, Ping-Chung; Fung, Kwok-Pui; Lau, Clara Bik-San

2014-03-15

Immunomodulation of natural polysaccharides has been the hot topic of research in recent years. In order to explore the immunomodulatory effect of Houttuynia cordata Thunb., the water extract was studied and a polysaccharide HCP-2 with molecular weight of 60,000 Da was isolated by chromatography using DEAE Sepharose CL-6B and Sephacryl S-500 [corrected] HR columns. The structure characterization of HCP-2 was performed by Fourier transform infrared spectroscopy (FTIR), acidic hydrolysis, PMP derivation, HPLC analysis and nuclear magnetic resonance spectra (NMR). HCP-2 was elucidated as a pectic polysaccharide with a linear chain of 1,4-linked α-D-galacturonic acid residues in which part of the 6-carboxyl groups were methyl esterified and part of 2-hydroxyl groups were acetylated. The bioactivity assays showed that HCP-2 could increase the secretions of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), macrophage inhibitory protein-1α (MIP-1α), macrophage inhibitory protein-1β (MIP-1β), and RANTES (regulated on activation, normal T cell expressed and secreted) in human peripheral blood mononuclear cells (PBMCs), which play critical roles in the innate immune system and shape the adaptive immunity. Our results implied that HCP-2 could be an immune enhancer. Copyright © 2013 Elsevier Ltd. All rights reserved.

COMPUTER PREDICTION OF BIOLOGICAL ACTIVITY OF DIMETHYL-N-(BENZOYL)AMIDOPHOSPHATE AND DIMETHYL-N-(PHENYLSULFONYL)AMIDOPHOSPHATE, EVALUATION OF THEIR CYTOTOXIC ACTIVITY AGAINST LEUKEMIC CELLS IN VITRO.

PubMed

Grynyuk, I I; Prylutska, S V; Kariaka, N S; Sliva, T Yu; Moroz, O V; Franskevych, D V; Amirkhanov, V M; Matyshevska, O P; Slobodyanik, M S

2015-01-01

Structural analogues of β-diketones--dimethyl-N-(benzoyl)amidophosphate (HCP) and dimethyl-N-(phenylsulfonyl)amidophosphate (HSP) were synthesized and identified by the methods of IR, 1H and 31P NMR spectroscopy. Screening of biological activity and calculation of physicochemical parameters of HCP and HSP compounds were done with the use of PASS and ACD/Labs computer programs. A wide range of biological activity of synthesized compounds, antitumor activity in particular, has been found. Calculations of the bioavailability criteria indicate that the investigated compounds have no deviations from Lipinski's rules. HCP compound is characterized by a high lipophilicity at physiological pH as compared to HSP. It was found that cytotoxic effect of the studied compounds on the leukemic L1210 cells was of time- and dose-dependent character. HCP is characterized by more pronounced and early cytotoxic effects as compared to HSP. It was shown that 2.5 mM HCP increased ROS production 3 times in the early period of incubation, and decreased cell viability by 40% after 48 h, and by 66%--after 72 h. Based on the computer calculation and undertaken research, HCP was selected for target chemical modifications and enhancement of its antitumor effect.

The C-stem in clinical practice: fifteen-year follow-up of a triple tapered polished cemented stem.

PubMed

Purbach, Bodo; Kay, Peter R; Siney, Paul D; Fleming, Patricia A; Wroblewski, B Michael

2013-09-01

The triple tapered polished cemented stem, C-Stem, introduced in 1993 was based on the original Charnley concept of the "flat back" polished stem. We present our continuing experience with the C-Stem in 621 consecutive primary arthroplasties implanted into 575 patients between 1993 and 1997. Four hundred and eighteen arthroplasties had a clinical and radiological follow-up past 10 years with a mean follow-up of 13 years (10-15). There were no revisions for stem loosening but 2 stems were revised for fracture - both with a defective cement mantle proximally. The stem design and the surgical technique support the original Charnley concept of limited stem subsidence within the cement mantle and the encouraging results continue to stand as a credit to Sir John Charnley's original philosophy. Copyright © 2013 Elsevier Inc. All rights reserved.

Mild hypothermic culture conditions affect residual host cell protein composition post-Protein A chromatography

PubMed Central

Goey, Cher Hui; Bell, David; Kontoravdi, Cleo

2018-01-01

ABSTRACT Host cell proteins (HCPs) are endogenous impurities, and their proteolytic and binding properties can compromise the integrity, and, hence, the stability and efficacy of recombinant therapeutic proteins such as monoclonal antibodies (mAbs). Nonetheless, purification of mAbs currently presents a challenge because they often co-elute with certain HCP species during the capture step of protein A affinity chromatography. A Quality-by-Design (QbD) strategy to overcome this challenge involves identifying residual HCPs and tracing their source to the harvested cell culture fluid (HCCF) and the corresponding cell culture operating parameters. Then, problematic HCPs in HCCF may be reduced by cell engineering or culture process optimization. Here, we present experimental results linking cell culture temperature and post-protein A residual HCP profile. We had previously reported that Chinese hamster ovary cell cultures conducted at standard physiological temperature and with a shift to mild hypothermia on day 5 produced HCCF of comparable product titer and HCP concentration, but with considerably different HCP composition. In this study, we show that differences in HCP variety at harvest cascaded to downstream purification where different residual HCPs were present in the two sets of samples post-protein A purification. To detect low-abundant residual HCPs, we designed a looping liquid chromatography-mass spectrometry method with continuous expansion of a preferred, exclude, and targeted peptide list. Mild hypothermic cultures produced 20% more residual HCP species, especially cell membrane proteins, distinct from the control. Critically, we identified that half of the potentially immunogenic residual HCP species were different between the two sets of samples. PMID:29381421

Ethnodrama: An Innovative Knowledge Translation Tool in the Management of Lymphedema

PubMed Central

Ahmed, Shahid; Quinlan, Elizabeth; McMullen, Linda; Thomas, Roanne; Fichtner, Pam; Block, Janice

2015-01-01

Background: Lymphedema can cause significant physical impairment and quality-of-life issues. Yet there is a gap in knowledge about lymphedema among breast cancer survivors (BCS), and health care professionals (HCP). Ethnodrama is an innovative knowledge translation strategy that uses theatrical performances for dissemination of research results. We evaluated the impact of live ethnodrama on HCP' and BCS' awareness and attitudes in relation to impact of lymphedema on BCS' lives. Methods: Ethnodrama performances were developed by script writers and a theatre director in collaboration with the investigators and BCS using data from published research and pre-performances workshops. Six interactive live performances were given to audiences of BCS, HCP, and community members in four cities across Canada. After watching these live performances, members of the audiences were asked to complete a paper-based questionnaire regarding their knowledge of lymphedema, and their attitudes and practices toward lymphedema. Results: Of 238 audience members who participated in the survey, 55 (23%) were BCS and 85 (37.5%) were HCP. Most members rated the performances as very effective in changing their (84%) or other people's (93%) understanding of lymphedema; 96% reported being motivated to seek additional information on lymphedema, and 72% of HCP anticipated changes in their practices related to lymphedema screening. Overall no significant differences were noted in responses to ethnodrama between BCS and HCP. Open-ended responses were supportive of the findings from the closed-ended questions. Conclusions: Our results indicate that ethnodrama performances effectively convey information and positively affecting changes in HCP' and BCS' attitudes toward lymphedema. PMID:26284137

Mild hypothermic culture conditions affect residual host cell protein composition post-Protein A chromatography.

PubMed

Goey, Cher Hui; Bell, David; Kontoravdi, Cleo

2018-04-01

Host cell proteins (HCPs) are endogenous impurities, and their proteolytic and binding properties can compromise the integrity, and, hence, the stability and efficacy of recombinant therapeutic proteins such as monoclonal antibodies (mAbs). Nonetheless, purification of mAbs currently presents a challenge because they often co-elute with certain HCP species during the capture step of protein A affinity chromatography. A Quality-by-Design (QbD) strategy to overcome this challenge involves identifying residual HCPs and tracing their source to the harvested cell culture fluid (HCCF) and the corresponding cell culture operating parameters. Then, problematic HCPs in HCCF may be reduced by cell engineering or culture process optimization. Here, we present experimental results linking cell culture temperature and post-protein A residual HCP profile. We had previously reported that Chinese hamster ovary cell cultures conducted at standard physiological temperature and with a shift to mild hypothermia on day 5 produced HCCF of comparable product titer and HCP concentration, but with considerably different HCP composition. In this study, we show that differences in HCP variety at harvest cascaded to downstream purification where different residual HCPs were present in the two sets of samples post-protein A purification. To detect low-abundant residual HCPs, we designed a looping liquid chromatography-mass spectrometry method with continuous expansion of a preferred, exclude, and targeted peptide list. Mild hypothermic cultures produced 20% more residual HCP species, especially cell membrane proteins, distinct from the control. Critically, we identified that half of the potentially immunogenic residual HCP species were different between the two sets of samples.

A structural equation model of patient-healthcare provider relationships and HIV-infected patient outcomes in Chinese populations.

PubMed

Chen, Wei-Ti; Shiu, Chengshi; Yang, Joyce P; Chuang, Peing; Zhang, Lin; Bao, Meijuan; Lu, Hongzhou

2018-03-01

Obtaining maximum antiretroviral therapy (ART) adherence is critical for maintaining a high CD4 count and strong immune function in PLWHA. Key factors for achieving optimum adherence include good medication self-efficacy, decreased medication-taking difficulties, and positive patient-healthcare provider (HCP) relationships. Limited studies have analyzed the correlation of these factors and ART adherence in Chinese population. In this paper, structural equation modeling was performed to assess the proposed model of relations between patient-HCP relationships and adherence. Audio Computer-Assisted Self-Interview (ACASI) software was used to collect data on ART adherence and patient variables among 227 PLWHA in Shanghai and Taipei. Participants completed a one-time 60-minute ACASI survey that consisted of standardized measures to assess demographics, recent CD4 counts, self-efficacy, patient-HCP relationship, adherence, and medication-taking difficulties. The data shown the relationship between patient-HCP relationships and adherence was significantly consistent with mediation by medication self-efficacy. However, patient-HCP interaction did not directly influence medication-taking difficulties, and medication-taking difficulties did not significantly affect CD4 counts. Furthermore, patient-HCP interactions did not directly impact CD4 counts; rather, the relation was consistent with mediation (by either better medication self-efficacy or better adherence) or by improved adherence alone. Future interventions should be designed to enhance self-management and provide better patient-HCP communication. This improved communication will enhance medication self-efficacy and decrease medication-taking difficulties. This in turn will improve medication adherence and immune function among PLWHA.

Improving health care proxy documentation using a web-based interview through a patient portal

PubMed Central

Crotty, Bradley H; Kowaloff, Hollis B; Safran, Charles; Slack, Warner V

2016-01-01

Objective Health care proxy (HCP) documentation is suboptimal. To improve rates of proxy selection and documentation, we sought to develop and evaluate a web-based interview to guide patients in their selection, and to capture their choices in their electronic health record (EHR). Methods We developed and implemented a HCP interview within the patient portal of a large academic health system. We analyzed the experience, together with demographic and clinical factors, of the first 200 patients who used the portal to complete the interview. We invited users to comment about their experience and analyzed their comments using established qualitative methods. Results From January 20, 2015 to March 13, 2015, 139 of the 200 patients who completed the interview submitted their HCP information for their clinician to review in the EHR. These patients had a median age of 57 years (Inter Quartile Range (IQR) 45–67) and most were healthy. The 99 patients who did not previously have HCP information in their EHR were more likely to complete and then submit their information than the 101 patients who previously had a proxy in their health record (odds ratio 2.4, P = .005). Qualitative analysis identified several ways in which the portal-based interview reminded, encouraged, and facilitated patients to complete their HCP. Conclusions Patients found our online interview convenient and helpful in facilitating selection and documentation of an HCP. Our study demonstrates that a web-based interview to collect and share a patient’s HCP information is both feasible and useful. PMID:26568608

High-pressure high-temperature stability of hcp-Ir xOs 1-x (x = 0.50 and 0.55) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yusenko, Kirill V.; Bykova, Elena; Bykov, Maxim

2016-12-23

Hcp-Ir 0.55Os 0.45 and hcp-Ir 0.50Os 0.50 alloys were synthesised by thermal decomposition of single-source precursors in hydrogen atmosphere. Both alloys correspond to a miscibility gap in the Ir–Os binary phase diagram and therefore are metastable at ambient conditions. An in situ powder X-ray diffraction has been used for a monitoring a formation of hcp-Ir0.55Os0.45 alloy from (NH 4) 2[Ir 0.55Os 0.45Cl 6] precursor. A crystalline intermediate compound and nanodimentional metallic particles with a large concentration of defects has been found as key intermediates in the thermal decomposition process in hydrogen flow. High-temperature stability of titled hcp-structured alloys has beenmore » investigated upon compression up to 11 GPa using a multi-anvil press and up to 80 GPa using laser-heated diamond-anvil cells to obtain a phase separation into fcc + hcp mixture. Compressibility curves at room temperature as well as thermal expansion at ambient pressure and under compression up to 80 GPa were collected to obtain thermal expansion coefficients and bulk moduli. hcp-Ir 0.55Os 0.45 alloy shows bulk moduli B0 = 395 GPa. Thermal expansion coefficients were estimated as α = 1.6·10 -5 K -1 at ambient pressure and α = 0.3·10 -5 K -1 at 80 GPa. Obtained high-pressure high-temperature data allowed us to construct the first model for pressure-dependent Ir–Os phase diagram.« less

Mechanism and energetics of dislocation cross-slip in hcp metals

NASA Astrophysics Data System (ADS)

Wu, Zhaoxuan; Curtin, W. A.

2016-10-01

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

A vignette study to examine health care professionals' attitudes towards patient involvement in error prevention.

PubMed

Schwappach, David L B; Frank, Olga; Davis, Rachel E

2013-10-01

Various authorities recommend the participation of patients in promoting patient safety, but little is known about health care professionals' (HCPs') attitudes towards patients' involvement in safety-related behaviours. To investigate how HCPs evaluate patients' behaviours and HCP responses to patient involvement in the behaviour, relative to different aspects of the patient, the involved HCP and the potential error. Cross-sectional fractional factorial survey with seven factors embedded in two error scenarios (missed hand hygiene, medication error). Each survey included two randomized vignettes that described the potential error, a patient's reaction to that error and the HCP response to the patient. Twelve hospitals in Switzerland. A total of 1141 HCPs (response rate 45%). Approval of patients' behaviour, HCP response to the patient, anticipated effects on the patient-HCP relationship, HCPs' support for being asked the question, affective response to the vignettes. Outcomes were measured on 7-point scales. Approval of patients' safety-related interventions was generally high and largely affected by patients' behaviour and correct identification of error. Anticipated effects on the patient-HCP relationship were much less positive, little correlated with approval of patients' behaviour and were mainly determined by the HCP response to intervening patients. HCPs expressed more favourable attitudes towards patients intervening about a medication error than about hand sanitation. This study provides the first insights into predictors of HCPs' attitudes towards patient engagement in safety. Future research is however required to assess the generalizability of the findings into practice before training can be designed to address critical issues. © 2012 John Wiley & Sons Ltd.

Piezoresistivity, mechanisms and model of cement-based materials with CNT/NCB composite fillers

NASA Astrophysics Data System (ADS)

Zhang, Liqing; Ding, Siqi; Dong, Sufen; Li, Zhen; Ouyang, Jian; Yu, Xun; Han, Baoguo

2017-12-01

The use of conductive cement-based materials as sensors has attracted intense interest over past decades. In this paper, carbon nanotube (CNT)/nano carbon black (NCB) composite fillers made by electrostatic self-assembly are used to fabricate conductive cement-based materials. Electrical and piezoresistive properties of the fabricated cement-based materials are investigated. Effect of filler content, load amplitudes and rate on piezoresistive property within elastic regime and piezoresistive behaviors during compressive loading to destruction are explored. Finally, a model describing piezoresistive property of cement-based materials with CNT/NCB composite fillers is established based on the effective conductive path and tunneling effect theory. The research results demonstrate that filler content and load amplitudes have obvious effect on piezoresistive property of the composites materials, while load rate has little influence on piezoresistive property. During compressive loading to destruction, the composites also show sensitive piezoresistive property. Therefore, the cement-based composites can be used to monitor the health state of structures during their whole life. The built model can well describe the piezoresistive property of the composites during compressive loading to destruction. The good match between the model and experiment data indicates that tunneling effect actually contributes to piezoresistive phenomenon.

Self-reported dietary adherence, disease-specific symptoms, and quality of life are associated with healthcare provider follow-up in celiac disease.

PubMed

Hughey, Jacob J; Ray, Bonnie K; Lee, Anne R; Voorhees, Kristin N; Kelly, Ciaran P; Schuppan, Detlef

2017-12-11

The only treatment for celiac disease (CeD) is a lifelong gluten-free diet (GFD). The restrictive nature of the GFD makes adherence a challenge. As an integral part of CeD management, multiple professional organizations recommend regular follow-up with a healthcare provider (HCP). Many CeD patients also participate in patient advocacy groups (PAGs) for education and support. Previous work found that follow-up of CeD patients is highly variable. Here we investigated the self-reported factors associated with HCP follow-up among individuals diagnosed with CeD who participate in a PAG. We conducted a survey of members of Beyond Celiac (a PAG), collecting responses from 1832 U.S. adults ages 19-65 who reported having CeD. The survey queried HCP follow-up related to CeD and included validated instruments for dietary adherence (CDAT), disease-specific symptoms (CSI), and quality of life (CD-QOL). Overall, 27% of respondents diagnosed with CeD at least five years ago reported that they had not visited an HCP about CeD in the last five years. The most frequent reason for not visiting an HCP was "doing fine on my own" (47.6%). Using multiple logistic regression, we identified significant associations between whether a respondent reported visiting an HCP about CeD in the last five years and the scores for all three validated instruments. In particular, as disease-specific symptoms and quality of life worsened, the probability of having visited an HCP increased. Conversely, as dietary adherence worsened, the probability decreased. Our results suggest that many individuals with CeD manage their disease without ongoing support from an HCP. Our results thus emphasize the need for greater access to high quality CeD care, and highlight an opportunity for PAGs to bring together patients and HCPs to improve management of CeD.

CDC guidance for evaluating health-care personnel for hepatitis B virus protection and for administering postexposure management.

PubMed

Schillie, Sarah; Murphy, Trudy V; Sawyer, Mark; Ly, Kathleen; Hughes, Elizabeth; Jiles, Ruth; de Perio, Marie A; Reilly, Meredith; Byrd, Kathy; Ward, John W

2013-12-20

This report contains CDC guidance that augments the 2011 recommendations of the Advisory Committee on Immunization Practices (ACIP) for evaluating hepatitis B protection among health-care personnel (HCP) and administering post-exposure prophylaxis. Explicit guidance is provided for persons working, training, or volunteering in health-care settings who have documented hepatitis B (HepB) vaccination years before hire or matriculation (e.g., when HepB vaccination was received as part of routine infant [recommended since 1991] or catch-up adolescent [recommended since 1995] vaccination). In the United States, 2,890 cases of acute hepatitis B were reported to CDC in 2011, and an estimated 18,800 new cases of hepatitis B occurred after accounting for underreporting of cases and asymptomatic infection. Although the rate of acute hepatitis B virus (HBV) infections have declined approximately 89% during 1990-2011, from 8.5 to 0.9 cases per 100,000 population in the United States, the risk for occupationally acquired HBV among HCP persists, largely from exposures to patients with chronic HBV infection. ACIP recommends HepB vaccination for unvaccinated or incompletely vaccinated HCP with reasonably anticipated risk for blood or body fluid exposure. ACIP also recommends that vaccinated HCP receive postvaccination serologic testing (antibody to hepatitis B surface antigen [anti-HBs]) 1-2 months after the final dose of vaccine is administered (CDC. Immunization of health-care personnel: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2011;60 [No. RR-7]). Increasing numbers of HCP have received routine HepB vaccination either as infants (recommended since 1991) or as catch-up vaccination (recommended since 1995) in adolescence. HepB vaccination results in protective anti-HBs responses among approximately 95% of healthy-term infants. Certain institutions test vaccinated HCP by measuring anti-HBs upon hire or matriculation, even when anti-HBs testing occurs greater than 2 months after vaccination. This guidance can assist clinicians, occupational health and student health providers, infection-control specialists, hospital and health-care training program administrators, and others in selection of an approach for assessing HBV protection for vaccinated HCP. This report emphasizes the importance of administering HepB vaccination for all HCP, provides explicit guidance for evaluating hepatitis B protection among previously vaccinated HCP (particularly those who were vaccinated in infancy or adolescence), and clarifies recommendations for postexposure management of HCP exposed to blood or body fluids.

The elastic properties and stability of fcc-Fe and fcc-FeNi alloys at inner-core conditions

NASA Astrophysics Data System (ADS)

Martorell, Benjamí; Brodholt, John; Wood, Ian G.; Vočadlo, Lidunka

2015-07-01

The agreement between shear wave velocities for the Earth's inner core observed from seismology with those derived from mineral physics is considerably worse than for any other region of the Earth. Furthermore, there is still debate as to the phase of iron present in the inner core, particularly when alloying with nickel and light elements is taken into account. To investigate the extent to which the mismatch between seismology and mineral physics is a function of either crystal structure and/or the amount of nickel present, we have used ab initio molecular dynamics simulations to calculate the elastic constants and seismic velocities (Vp and Vs) of face centred cubic (fcc) iron at Earth's inner core pressures (360 GPa) and at temperatures up to ˜7000 K. We find that Vp for fcc iron (fcc-Fe) is very similar to that for hexagonal close packed (hcp) iron at all temperatures. In contrast, Vs for fcc-Fe is significantly higher than in hcp-Fe, with the difference increasing with increasing temperature; the difference between Vs for the core (from seismology) and Vs for fcc-Fe exceeds 40 per cent. These results are consistent with previous work at lower temperatures. We have also investigated the effect of 6.5 and 13 atm% Ni in fcc-Fe. We find that Ni only slightly reduces Vp and Vs (e.g. by 2 per cent in Vs for 13 atm% Ni at 5500 K), and cannot account for the difference between the velocities observed in the core and those of pure fcc-Fe. We also tried to examine pre-melting behaviour in fcc-Fe, as reported in hcp-Fe by extending the study to very high temperatures (at which superheating may occur). However, we find that fcc-Fe spontaneously transforms to other hcp-like structures before melting; two hcp-like structures were found, both of hexagonal symmetry, which may most easily be regarded as being derived from an hcp crystal with stacking faults. That the structure did not transform to a true hcp phase is likely as a consequence of the limited size of the simulation box (108 atoms). At 360 GPa, in pure fcc-Fe, we find that the transition from fcc to the hcp-like structure occurs at 7000 K, whereas in the Ni bearing system, the transition occurs at higher temperature (7250 K). This reinforces previous work showing that fcc-Fe might transform to hcp-Fe just before melting, and that Ni tends to stabilize the fcc structure with respect to hcp.

Development of performance properties of ternary mixtures and concrete pavement mixture design and analysis (MDA) : effect of paste quality on fresh and hardened properties of ternary mixtures.

DOT National Transportation Integrated Search

2012-07-01

The purpose of this study was to investigate the effect of cement paste quality on the concrete performance, particularly fresh properties, : by changing the water-to-cementitious materials ratio (w/cm), type and dosage of supplementary cementitious ...

Original behavior of pore water radiolysis in cement-based materials containing sulfide: Coupling between experiments and simulations

NASA Astrophysics Data System (ADS)

Bouniol, P.; Guillot, W.; Dauvois, V.; Dridi, W.; Le Caër, S.

2018-09-01

Blended cements with high content of blast furnace slag (CEM III/C) can be used for nuclear waste conditioning because of their low hydration heat as compared to ordinary Portland cements (CEM I). They however contain some sulfide, an impurity whose role needs to be investigated. Indeed, they can have an effect on the radiolytic H2 production under irradiation. To study the impact of sulfide species on H2 production, gamma irradiation, at a dose rate of 356 Gy h-1, was performed during 6 months in a closed system without O2 on a cement paste made with CEM III/C. At short time, the radiolytic H2 production rate is higher than that measured using CEM I. On the basis of reaction data collected in the literature on sulfur species, radiolysis simulations performed for both systems confirm this behavior. Moreover, they suggest that the sulfide concentration, initially imposed in pore solution by the slag is of the order of 180 mM, and is responsible for this H2 production. For the first two irradiation months, the following phenomena are then evidenced in CEM III/C: 1) conversion of sulfide into polysulfide anions; 2) pH increase; 3) production of H2 due to the H•+ H2S reaction having a very high rate constant. Nevertheless, in the medium term, the residual sulfide concentration is not sufficient any more for this mechanism to occur. It imposes a reducing environment, leading to a very efficient recombination of H2 in pore solution. The resulting equilibrium state is reinforced by the high liquid saturation level in the cement paste porosity. Therefore, even if the presence of sulfide species in blended cements momentarily increases the H2 production rate, it strongly reduces it at long times.

Solid state NMR and LVSEM studies on the hardening of latex modified tile mortar systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rottstegge, J.; Arnold, M.; Herschke, L.

Construction mortars contain a broad variety of both inorganic and organic additives beside the cement powder. Here we present a study of tile mortar systems based on portland cement, quartz, methyl cellulose and different latex additives. As known, the methyl cellulose stabilizes the freshly prepared cement paste, the latex additive enhances final hydrophobicity, flexibility and adhesion. Measurements were performed by solid state nuclear magnetic resonance (NMR) and low voltage scanning electron microscopy (LVSEM) to probe the influence of the latex additives on the hydration, hardening and the final tile mortar properties. While solid state NMR enables monitoring of the bulkmore » composition, scanning electron microscopy affords visualization of particles and textures with respect to their shape and the distribution of the different phases. Within the alkaline cement paste, the poly(vinyl acetate) (VAc)-based latex dispersions stabilized by poly(vinyl alcohol) (PVA) were found to be relatively stable against hydrolysis. The influence of the combined organic additives methyl cellulose, poly(vinyl alcohol) and latexes stabilized by poly(vinyl alcohol) on the final silicate structure of the cement hydration products is small. But even small amounts of additives result in an increased ratio of ettringite to monosulfate within the final hydrated tile mortar as monitored by {sup 27}Al NMR. The latex was found to be adsorbed to the inorganic surfaces, acting as glue to the inorganic components. For similar latex water interfaces built up by poly(vinyl alcohol), a variation in the latex polymer composition results in modified organic textures. In addition to the networks of the inorganic cement and of the latex, there is a weak network build up by thin polymer fibers, most probably originating from poly(vinyl alcohol). Besides the weak network, polymer fibers form well-ordered textures covering inorganic crystals such as portlandite.« less

Utilization of municipal solid waste incineration (MSWI) fly ash in blended cement Part 1: Processing and characterization of MSWI fly ash.

PubMed

Aubert, J E; Husson, B; Sarramone, N

2006-08-25

This paper is the first of a series of two articles dealing with the processes applied to MSWI fly ash with a view to reusing it safely in cement-based materials. Part 1 presents two stabilization processes and Part 2 deals with the use of the two treated fly ashes (TFA) in mortars. Two types of binder were used: an Ordinary Portland Cement (OPC) containing more than 95% clinker (CEM I 52.5R) and a binary blend cement composed of 70% ground granulated blast furnace slag and 30% clinker (CEM III-B 42.5N). In this first part, two stabilization processes are presented: the conventional process, called "A", based on the washing, phosphation and calcination of the ash, and a modified process, called "B", intended to eliminate metallic aluminum and sulfate contained in the ash. The physical, chemical and mineralogical characteristics of the two TFA were comparable. The main differences observed were those expected, i.e. TFA-B was free of metallic aluminum and sulfate. The mineralogical characterization of the two TFAs highlighted the presence of large amounts of a calcium aluminosilicate phase taking two forms, a crystalline form (gehlenite) and an amorphous form. Hydration studies on pastes containing mixed TFA and calcium hydroxide showed that this phase reacted with calcium hydroxide to form calcium aluminate hydrates. This formation of hydrates was accompanied by a hardening of the pastes. These results are very encouraging for the reuse of such TFA in cement-based materials because they can be considered as pozzolanic additions and could advantageously replace a part of the cement in cement-based materials. Finally, leaching tests were carried out to evaluate the environmental impact of the two TFAs. The elements which were less efficiently stabilized by process A were zinc, cadmium and antimony but, when the results of the leaching tests were compared with the thresholds of the European landfill directive, TFA-A could nevertheless be accepted at landfills for non-hazardous waste. The modifications of the process led to a significant reduction in the stabilization of chromium, selenium and antimony.

Inert-Gas Condensed Co-W Nanoclusters: Formation, Structure and Magnetic Properties

NASA Astrophysics Data System (ADS)

Golkar-Fard, Farhad Reza

Rare-earth permanent magnets are used extensively in numerous technical applications, e.g. wind turbines, audio speakers, and hybrid/electric vehicles. The demand and production of rare-earth permanent magnets in the world has in the past decades increased significantly. However, the decrease in export of rare-earth elements from China in recent time has led to a renewed interest in developing rare-earth free permanent magnets. Elements such as Fe and Co have potential, due to their high magnetization, to be used as hosts in rare-earth free permanent magnets but a major challenge is to increase their magnetocrystalline anisotropy constant, K1, which largely drives the coercivity. Theoretical calculations indicate that dissolving the 5d transition metal W in Fe or Co increases the magnetocrystalline anisotropy. The challenge, though, is in creating a solid solution in hcp Co or bcc Fe, which under equilibrium conditions have negligible solubility. In this dissertation, the formation, structure, and magnetic properties of sub-10 nm Co-W clusters with W content ranging from 4 to 24 atomic percent were studied. Co-W alloy clusters with extended solubility of W in hcp Co were produced by inert gas condensation. The different processing conditions such as the cooling scheme and sputtering power were found to control the structural state of the as-deposited Co-W clusters. For clusters formed in the water-cooled formation chamber, the mean size and the fraction crystalline clusters increased with increasing power, while the fraction of crystalline clusters formed in the liquid nitrogen-cooled formation chamber was not as affected by the sputtering power. For the low W content clusters, the structural characterization revealed clusters predominantly single crystalline hcp Co(W) structure, a significant extension of W solubility when compared to the equilibrium solubility, but fcc Co(W) and Co3W structures were observed in very small and large clusters, respectively. At high W content, clusters with hcp Co(W), fcc Co(W) or Co3W structures were observed. The magnetic measurements at 10 K and 300 K revealed that the coercivity, saturation magnetization and magnetocrystalline anisotropy of the clusters formed in the water-cooled formation chamber were higher than for clusters formed in the liquid nitrogen-cooled formation chamber. The coercivity and magnetocrystalline anisotropy of the clusters increased as long as W was dissolved into the hcp Co structure. With increasing fraction of Co3W and fcc Co(W) clusters, as observed in the high-W content sample, the magnetic properties deteriorated significantly. The highest coercivity and magnetocrystalline anisotropy of 893 Oe and 3.9 x 106 ergs/cm3, respectively, was obtained at 10 K for the 5 at.% W clusters sputtered at 150 W in the water-cooled formation chamber.

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression

PubMed Central

Baeza, F. Javier; Garcés, Pedro

2017-01-01

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material’s strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure. PMID:29186797

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression.

PubMed

Galao, Oscar; Baeza, F Javier; Zornoza, Emilio; Garcés, Pedro

2017-11-24

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material's strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Study on the properties of chromium residue-cement matrices (CRCM) and the influences of superplasticizers on chromium(VI)-immobilising capability of cement matrices.

PubMed

Shi, Hui-Sheng; Kan, Li-Li

2009-03-15

The study of cementitious activity of chromium residue (CR) was carried out to formulate the properties of chromium residue-cement matrices (CRCM) by blending CR with Ordinary Portland Cement (OPC). The particle size distribution, microstructures of CR were investigated by some apparatuses, and physical properties, leaching behavior of hexavalent chromium [Cr(VI)] of CRCM were also determined by some experiments. Three types of commonly used superplasticizers (sulphonated acetone formaldehyde superplasticizer (J1), polycarboxylate-based superplasticizer (J2) and naphthalene superplasticizer (J3)) were chosen to investigate their influences on the physical properties and the Cr(VI)-immobilisation in the leachate of the CRCM hardened pastes. The results show that the CR has a certain cementitious activity. The incorporation of CR improves the pore size distribution of CRCM. The Cr(VI) concentrations in the leachate of CRCM significantly decrease by incorporation of J2. Among three superplasticizers, J2 achieves lowest Cr(VI) leaching ratio. Based on this study, it is likely to develop CR as a potential new additive used in cement-based materials.

Effect of dietary protein concentration on ammonia and greenhouse gas emitting potential of dairy manure.

PubMed

Lee, C; Hristov, A N; Dell, C J; Feyereisen, G W; Kaye, J; Beegle, D

2012-04-01

Two experiments were conducted to investigate the effect of dietary crude protein concentration on ammonia (NH(3)) and greenhouse gas (GHG; nitrous oxide, methane, and carbon dioxide) emissions from fresh dairy cow manure incubated in a controlled environment (experiment 1) and from manure-amended soil (experiment 2). Manure was prepared from feces and urine collected from lactating Holstein cows fed diets with 16.7% (DM basis; HCP) or 14.8% CP (LCP). High-CP manure had higher N content and proportion of NH(3)- and urea-N in total manure N than LCP manure (DM basis: 4.4 vs. 2.8% and 51.4 vs. 30.5%, respectively). In experiment 1, NH(3) emitting potential (EP) was greater for HCP compared with LCP manure (9.20 vs. 4.88 mg/m(2) per min, respectively). The 122-h cumulative NH(3) emission tended to be decreased 47% (P=0.09) using LCP compared with HCP manure. The EP and cumulative emissions of GHG were not different between HCP and LCP manure. In experiment 2, urine and feces from cows fed LCP or HCP diets were mixed and immediately applied to lysimeters (61×61×61 cm; Hagerstown silt loam; fine, mixed, mesic Typic Hapludalf) at 277 kg of N/ha application rate. The average NH(3) EP (1.53 vs. 1.03 mg/m(2) per min, respectively) and the area under the EP curve were greater for lysimeters amended with HCP than with LCP manure. The largest difference in the NH(3) EP occurred approximately 24 h after manure application (approximately 3.5 times greater for HCP than LCP manure). The 100-h cumulative NH(3) emission was 98% greater for HCP compared with LCP manure (7,415 vs. 3,745 mg/m(2), respectively). The EP of methane was increased and that of carbon dioxide tended to be increased by LCP compared with HCP manure. The cumulative methane emission was not different between treatments, whereas the cumulative carbon dioxide emission was increased with manure from the LCP diet. Nitrous oxide emissions were low in this experiment and did not differ between treatments. In the conditions of these experiments, fresh manure from dairy cows fed a LCP diet had substantially lower NH(3) EP, compared with manure from cows fed a HCP diet. The LCP manure increased soil methane EP due to a larger mass of manure added to meet plant N requirements compared with HCP manure. These results represent effects of dietary protein on NH(3) and GHG EP of manure in controlled laboratory conditions and do not account for environmental factors affecting gaseous emissions from manure on the farm. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Beliefs, attitudes, and activities of healthcare personnel about influenza and pneumococcal vaccines.

PubMed

Çiftci, Fatma; Şen, Elif; Demir, Nalan; Çiftci, Orçun; Erol, Serhat; Kayacan, Oya

2018-01-02

Vaccination of healthcare personnel (HCP) is an effective measure for preventing the spread of influenza among at-risk patients. This study was conducted to determine influenza vaccination rates and activities among HCP working at a tertiary healthcare setting. This study included 470 HCP (85 physicians, 134 nurses, 53 healthcare assistants, 44 paramedics, 47 medical secretaries, and 107 auxillary staff members) working at the emergency, cardiology, chest diseases, and internal medicine departments with the largest volume of patients with vaccination indication of two large university hospitals with similar medical practices and work environment. Each participant completed an anonymous questionnaire form. A total of 470 HCP participated in the survey. The compliance rate of the HCP to participate in the survey was 93.6%. Of these, 26.7% had been vaccinated against influenza. Vaccination in the survey year was significantly associated with having regular influenza vaccinations (OR 48.66; 95% CI:[25.09-94.369]; P<.01); having an educational level of college or higher (OR 2.07; 95% CI:[1.03-4.15]; P<.05); being a physician (OR 4.25; 95% CI:[1.28-14.07]; P< .05); and a professional experience of more than 5 years (OR 2.02; 95%CI:[1.13-5.62]; P< .05). Physicians recommended and prescribed the influenza vaccine significantly more frequently than the pneumococcal vaccine (37.6% vs 30.6%, P = .03, 25.9% vs 17.6%, P = .001, respectively). Among all HCP, the reasons for vaccination included having the opinion that the vaccine provides a partial protection against the infection (75.2%), reduces work force loss (48.8%), reduces the rates of death and severe conditions like pneumonia (43.2%), and reduces hospitalization (40.8%). The HCP had been vaccinated to protect family members (81.6%), people around (51.2%), herself/himself (47.2%), and patients (28%) fom infection. The reasons of not getting vaccinated against influenza among HCP included fear of vaccine's adverse effects (31.0%), doubts about its efficacy (28.9%) and safety (22.3%), and lack of adequate knowledge about vaccination (16.2%). Our results indicated that influenza vaccination rates are low in our whole HCP sample, with physicians having a slightly better rate than other HCP. Getting regularly vaccinated, having an educational level of college or higher, being a physician, and having a professional experience of more than 5 years positively affects the rate of future vaccinations. Physicians significantly more commonly recommended and prescribed the influenza vaccine than the pneumococcal vaccine. The most important reasons for getting vaccinated included having the opinion that the vaccine provided partial protection and intending to protect family members from infection. In our whole HCP sample, the reasons of not getting vaccinated against influenza included fear of vaccine's adverse effects and doubts about its efficacy and safety. Training meetings should be held for HCPs to underscore the importance of the influenza vaccine for protection of patients against the influenza.

Antiwashout behavior of calcium phosphate cement incorporated with Poly(ethylene glycol)

NASA Astrophysics Data System (ADS)

Hablee, S.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.

2018-01-01

The effect of powder-to-liquid ratio and addition of poly(ethylene glycol) on the antiwashout behavior of calcium phosphate cement has been investigated. Calcium hydroxide, Ca(OH)2, and diammonium hydrogen phosphate, (NH4)2HPO4, were used as precursors with distilled water as the solvent in the wet chemical precipitation synthesis of hydroxyapatite powder. Cement paste was prepared by mixing the as-synthesized powder with distilled water at certain ratios, varied at 1.0, 1.3, 1.5 and 1.6. Poly(ethylene glycol) was added into distilled water, varied at 1, 2, 3, 4 and 5 wt% using the powder-to-liquid ratio of 1.3. The antiwashout properties of the cement has been investigated by soaking in Ringer’s solution for 3 and 7 days. The evolution of compressive strength of calcium phosphate cement before and after soaking have been determined. After 7 days soaking, the strength of the cement increased by 94.4%, 2.98%, 11.39% and 111.29% for powder-to-liquid ratios 1.0, 1.3, 1.5 and 1.6 respectively. The addition of poly(ethylene glycol) up to 3% shows an increase in strength after 7 days soaking, with 57.75%, 16.4% and 19.97% increase for 1, 2 and 3% poly(ethylene glycol) contents respectively. The calcium phosphate cement produced in this current study shows excellent antiwashout behavior since no cement dissolution happened and the compressive strength of the cement increased with soaking time throughout 7 days soaking in Ringer’s solution.

MicroCT analysis of a retrieved root restored with a bonded fiber-reinforced composite dowel: a pilot study.

PubMed

Lorenzoni, Fabio Cesar; Bonfante, Estevam A; Bonfante, Gerson; Martins, Leandro M; Witek, Lukasz; Silva, Nelson R F A

2013-08-01

This evaluation aimed to (1) validate micro-computed tomography (microCT) findings using scanning electron microscopy (SEM) imaging, and (2) quantify the volume of voids and the bonded surface area resulting from fiber-reinforced composite (FRC) dowel cementation technique using microCT scanning technology/3D reconstructing software. A fiberglass dowel was cemented in a condemned maxillary lateral incisor prior to its extraction. A microCT scan was performed of the extracted tooth creating a large volume of data in DICOM format. This set of images was imported to image-processing software to inspect the internal architecture of structures. The outer surface and the spatial relationship of dentin, FRC dowel, cement layer, and voids were reconstructed. Three-dimensional spatial architecture of structures and volumetric analysis revealed that 9.89% of the resin cement was composed of voids and that the bonded area between root dentin and cement was 60.63% larger than that between cement and FRC dowel. SEM imaging demonstrated the presence of voids similarly observed using microCT technology (aim 1). MicroCT technology was able to nondestructively measure the volume of voids within the cement layer and the bonded surface area at the root/cement/FRC interfaces (aim 2). The interfaces at the root dentin/cement/dowel represent a timely and relevant topic where several efforts have been conducted in the past few years to understand their inherent features. MicroCT technology combined with 3D reconstruction allows for not only inspecting the internal arrangement rendered by fiberglass adhesively bonded to root dentin, but also estimating the volume of voids and contacted bond area between the dentin and cement layer. © 2013 by the American College of Prosthodontists.

Microwave assisted preparation of magnesium phosphate cement (MPC) for orthopedic applications: a novel solution to the exothermicity problem.

PubMed

Zhou, Huan; Agarwal, Anand K; Goel, Vijay K; Bhaduri, Sarit B

2013-10-01

There are two interesting features of this paper. First, we report herein a novel microwave assisted technique to prepare phosphate based orthopedic cements, which do not generate any exothermicity during setting. The exothermic reactions during the setting of phosphate cements can cause tissue damage during the administration of injectable compositions and hence a solution to the problem is sought via microwave processing. This solution through microwave exposure is based on a phenomenon that microwave irradiation can remove all water molecules from the alkaline earth phosphate cement paste to temporarily stop the setting reaction while preserving the active precursor phase in the formulation. The setting reaction can be initiated a second time by adding aqueous medium, but without any exothermicity. Second, a special emphasis is placed on using this technique to synthesize magnesium phosphate cements for orthopedic applications with their enhanced mechanical properties and possible uses as drug and protein delivery vehicles. The as-synthesized cements were evaluated for the occurrences of exothermic reactions, setting times, presence of Mg-phosphate phases, compressive strength levels, microstructural features before and after soaking in (simulated body fluid) SBF, and in vitro cytocompatibility responses. The major results show that exposure to microwaves solves the exothermicity problem, while simultaneously improving the mechanical performance of hardened cements and reducing the setting times. As expected, the cements are also found to be cytocompatible. Finally, it is observed that this process can be applied to calcium phosphate cements system (CPCs) as well. Based on the results, this microwave exposure provides a novel technique for the processing of injectable phosphate bone cement compositions. © 2013.

State law and influenza vaccination of health care personnel.

PubMed

Stewart, Alexandra M; Cox, Marisa A

2013-01-21

Nosocomial influenza outbreaks, attributed to the unvaccinated health care workforce, have contributed to patient complications or death, worker illness and absenteeism, and increased economic costs to the health care system. Since 1981, the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) has recommended that all HCP receive an annual influenza vaccination. Health care employers (HCE) have adopted various strategies to encourage health care personnel (HCP) to voluntarily receive influenza vaccination, including: sponsoring educational and promotional campaigns, increasing access to seasonal influenza vaccine, permitting the use of declination statements, and combining multiple approaches. However, these measures failed to significantly increase uptake among HCP. As a result, beginning in 2004, health care facilities and local health departments began to require certain HCP to receive influenza vaccination as a condition of employment and annually. Today, hundreds of facilities throughout the country have developed and implemented similar policies. Mandatory vaccination programs have been endorsed by professional and non-profit organizations, state health departments, and public health. These programs have been more effective at increasing coverage rates than any voluntary strategy, with some health systems reporting coverage rates up to 99.3%. Several states have enacted laws requiring HCEs to implement vaccination programs for the workforce. These laws present an example of how states will respond to threats to the public's health and constrain personal choice in order to protect vulnerable populations. This study analyzes laws in twenty states that address influenza vaccination requirements for HCP who practice in acute or long-term care facilities in the United States. The laws vary in the extent to which they incorporate the six elements of a mandatory HCP influenza vaccination program. Four of the twenty states have adopted a broad definition of HCP or HCE. While 16/20 of the laws require employers to "provide," "arrange for," "ensure," "require" or "offer" influenza vaccinations to HCP, only four states explicitly require HCEs to cover the cost of vaccination. Fifteen of the twenty laws allow HCP to decline the vaccination due to medical contraindication, religious or philosophical beliefs, or by signing a declination statement. Finally, three states address how to sanction noncompliant HCPs. The analysis also discusses the development of a model legal policy that legislators could use as they draft and revise influenza prevention guidelines in health care settings. Copyright © 2012 Elsevier Ltd. All rights reserved.

The self-setting properties and in vitro bioactivity of tricalcium silicate.

PubMed

Zhao, Wenyuan; Wang, Junying; Zhai, Wanyin; Wang, Zheng; Chang, Jiang

2005-11-01

In this study, tricalcium silicate (Ca(3)SiO(5)), as a new promising injectable bioactive material, was employed to investigate its physical and chemical properties for an injectable bioactive cement filler. The workable Ca(3)SiO(5) pastes with a liquid to powder (L/P) ratio of 0.8--.2 mlg(-1)could be injected for 15--60 min (nozzle diameter 2.0mm). The setting process yielded cellular structures with compressive strength of 6.4--20.2 MPa after 2--28 days. The in vitro bioactivity of Ca(3)SiO(5) paste was investigated by soaking in simulated body fluid (SBF) for various periods. The result showed that the Ca(3)SiO(5) paste could induce hydroxyapatite (HA) formation and dissolve slowly in SBF. The result of indirect cytotoxicity evaluation indicated that Ca(3)SiO(5) paste had a stimulatory effect on cell growth in a certain concentration range. The exothermic process showed that Ca(3)SiO(5) had lower heat evolution rate during the hydration as compared to calcium phosphate cement (CPC). Our results indicated that Ca(3)SiO(5) paste was bioactive and dissolvable, and it is a progressive candidate for further investigation as injectable tissue repairing substitute.

Constraining Phosphorus Chemistry in Carbon- and Oxygen-Rich Circumstellar Envelopes: Observations of PN, HCP, and CP

NASA Astrophysics Data System (ADS)

Milam, S. N.; Halfen, D. T.; Tenenbaum, E. D.; Apponi, A. J.; Woolf, N. J.; Ziurys, L. M.

2008-09-01

Millimeter-wave observations of PN, CP, and HCP have been carried out toward circumstellar envelopes of evolved stars using the Arizona Radio Observatory (ARO). HCP and PN have been identified in the carbon-rich source CRL 2688 via observations at 1 mm using the Submillimeter Telescope (SMT) and 2-3 mm with the Kitt Peak 12 m. An identical set of measurements were carried out toward IRC +10216, as well as observations of CP at 1 mm. PN was also observed toward VY Canis Majoris (VY CMa), an oxygen-rich supergiant star. The PN and HCP line profiles in CRL 2688 and IRC +10216 are roughly flat topped, indicating unresolved, optically thin emission; CP, in contrast, has a distinct "U" shape in IRC +10216. Modeling of the line profiles suggests abundances, relative to H2, of f(PN) ~ (3-5) × 10-9 and f(HCP) ~ 2 × 10-7 in CRL 2688, about an order of magnitude higher than in IRC +10216. In VY CMa, f(PN) is ~4 × 10-8. The data in CRL 2688 and IRC +10216 are consistent with LTE formation of HCP and PN in the inner envelope, as predicted by theoretical calculations, with CP a photodissociation product at larger radii. The observed abundance of PN in VY CMa is a factor of 100 higher than LTE predictions. In IRC +10216, the chemistry of HCP/CP mimics that of HCN/CN and suggests an N2 abundance of f ~ 1 × 10-7. The chemistry of phosphorus appears active in both carbon- and oxygen-rich envelopes of evolved stars.

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals.

PubMed

Wu, Zhaoxuan; Curtin, W A

2016-10-04

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated [Formula: see text] dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of [Formula: see text] dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal [Formula: see text] dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals

PubMed Central

Wu, Zhaoxuan; Curtin, W. A.

2016-01-01

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated 〈c+a〉 dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of 〈c+a〉 dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal 〈c+a〉 dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension–compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals. PMID:27647908

Improving health care proxy documentation using a web-based interview through a patient portal.

PubMed

Bajracharya, Adarsha S; Crotty, Bradley H; Kowaloff, Hollis B; Safran, Charles; Slack, Warner V

2016-05-01

Health care proxy (HCP) documentation is suboptimal. To improve rates of proxy selection and documentation, we sought to develop and evaluate a web-based interview to guide patients in their selection, and to capture their choices in their electronic health record (EHR). We developed and implemented a HCP interview within the patient portal of a large academic health system. We analyzed the experience, together with demographic and clinical factors, of the first 200 patients who used the portal to complete the interview. We invited users to comment about their experience and analyzed their comments using established qualitative methods. From January 20, 2015 to March 13, 2015, 139 of the 200 patients who completed the interview submitted their HCP information for their clinician to review in the EHR. These patients had a median age of 57 years (Inter Quartile Range (IQR) 45-67) and most were healthy. The 99 patients who did not previously have HCP information in their EHR were more likely to complete and then submit their information than the 101 patients who previously had a proxy in their health record (odds ratio 2.4, P = .005). Qualitative analysis identified several ways in which the portal-based interview reminded, encouraged, and facilitated patients to complete their HCP. Patients found our online interview convenient and helpful in facilitating selection and documentation of an HCP. Our study demonstrates that a web-based interview to collect and share a patient's HCP information is both feasible and useful. © The Author 2015. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Houttuynia cordata polysaccharides ameliorate pneumonia severity and intestinal injury in mice with influenza virus infection.

PubMed

Zhu, Haiyan; Lu, Xiaoxiao; Ling, Lijun; Li, Hong; Ou, Yingye; Shi, Xunlong; Lu, Yan; Zhang, Yunyi; Chen, Daofeng

2018-05-23

Hottuynia cordata is an important traditional Chinese medicine for the treatment of respiratory diseases including bacterial and viral infections. Polysaccharides isolated from Houttuynia cordata (HCP), as its main ingredients, have been demonstrated to ameliorate the LPS-induced acute lung injury in mice. The study aimed to determine the protective effects of HCP on multiple organ injury in influenza A virus (IAV) H1N1 infected mice and its primary mechanisms in anti-inflammation and immune regulation. Mice were inoculated with IAV H1N1 and then treated with 20 or 40 mg/kg/d of HCP for survival test and acute lung-gut injury test. The treatment with HCP resulted in an increase in the survival rate of H1N1 infected mice and the protection from lung and intestine injury, accompanied with the reduced virus replication. HCP markedly decreased the concentration of pulmonary proinflammatory cytokines/chemokines and the number of intestinal goblet cells, and strengthened the intestinal physical and immune barrier, according to the increase of sIgA and tight junction protein (ZO-1) in intestine. At the same time, the inhibition of inflammation in lung and gut was related to the suppressing of the expression of TLR4 and p-NFκB p65 in lung. These results indicated that HCP ameliorated lung and intestine injury induced by IAV attack. The mechanisms were associated with inhibition of inflammation, protection of intestinal barrier and regulation of mucosal immunity, which may be related to the regulation of gut-lung axis. As an alternative medicine, HCP may have clinical potential to treat IAV infection in human beings. Copyright © 2018 Elsevier B.V. All rights reserved.

A rapid immunochromatography test based on Hcp1 is a potential point-of-care test for serological diagnosis of melioidosis.

PubMed

Phokrai, Phornpun; Karoonboonyanan, Wisansanee; Thanapattarapairoj, Nida; Promkong, Chidchanok; Dulsuk, Adul; Koosakulnirand, Sirikamon; Canovali, Sasha; Indrawattana, Nitaya; Jutrakul, Yaowaruk; Wuthiekanun, Vanaporn; Limmathurotsakul, Direk; Brett, Paul J; Burtnick, Mary N; Lertmemongkolchai, Ganjana; Chantratita, Narisara

2018-05-30

Melioidosis is a fatal infectious disease caused by the environmental bacterium Burkholderia pseudomallei It is highly endemic in Asia and northern Australia but neglected in many other tropical countries. Melioidosis patients have a wide range of clinical manifestations and definitive diagnosis requires bacterial culture which can be time-consuming. A reliable rapid serological tool is greatly needed for disease surveillance and diagnosis. We previously demonstrated by ELISA that a hemolysin-coregulated protein (Hcp1) is a promising target for serodiagnosis of melioidosis. In this study, we have developed a rapid immunochromatography test (ICT) using Hcp1 as the target antigen (Hcp1-ICT). We evaluated this test for specific antibody detection using serum samples obtained from 4 groups of human subjects including : ( i ) 487 culture-confirmed melioidosis patients from four hospitals in northeast Thailand; ( ii ) 202 healthy donors from northeast Thailand; ( iii ) 90 U.S. healthy donors and ( iv ) 207 patients infected with other organisms. Compared to culture results as a gold standard, the sensitivity of ICT for all hospitals was 88.3 %. The specificities for Thai donors and U.S. donors were 86.1 % and 100 % , respectively and for other infections was 91.8 %. The results of the Hcp1-ICT demonstrated 92.4 % agreement with the Hcp1-ELISA with kappa value of 0.829 and is much improved when compared with the current serological method, indirect hemagglutination assay ( IHA ) ( 69.5 % sensitivity and 67.6 % specificity for Thais ). The Hcp1-ICT represents a potential point-of-care ( POC ) test and may be used to replace the IHA for screening of melioidosis in hospitals as well as resource-limited areas. Copyright © 2018 Phokrai et al.

Structural and magnetic transition in stainless steel Fe-21Cr-6Ni-9Mn up to 250 GPa

NASA Astrophysics Data System (ADS)

Liu, Lei; Hou, Qi-Yue; Zhang, Yi; Jing, Qiu-Min; Wang, Zhi-Gang; Bi, Yan; Xu, Ji-An; Li, Xiao-Dong; Li, Yan-Chun; Liu, Jing

2015-06-01

Stainless steel Fe-21Cr-6Ni-9Mn (SS 21-6-9), with ˜21% Cr, ˜6% Ni, and ˜9% Mn in weight percentage, has wide applications in extensive fields. In the present study, SS 21-6-9 is compressed up to 250 GPa, and its crystal structures and compressive behaviors are investigated simultaneously using the synchrotron angle-dispersive x-ray diffraction technique. The SS 21-6-9 undergoes a structural phase transition from fcc to hcp structure at ˜12.8 GPa with neglectable volume collapse within the determination error under the quasi-hydrostatic environment. The hcp structure remains stable up to the highest pressure of 250 GPa in the present experiments. The antiferromagnetic-to-nonmagnetic state transition of hcp SS 21-6-9 with the changes of inconspicuous density and structure, is discovered at ˜50 GPa, and revealed by the significant change in c/a ratio. The hcp SS-21-6-9 is compressive anisotropic: it is more compressive in the c-axis direction than in the a-axis direction. Both the equations of states (EOSs) of fcc and hcp SS 21-6-9, which are in accordance with those of fcc and hcp pure irons respectively, are also presented. Furthermore, the c/a ratio of hcp SS 21-6-9 at infinite compression, R∞, is consistent with the values of pure iron and Fe-10Ni alloy. Project supported by the National Natural Science Foundation of China (Grant Nos. U1230201, 11274281, and 11304294), the Industrial Technology Development Program, China (Grant No. 9045140509), and the Funds from the Chinese Academy of Sciences (Grant Nos. KJCX2-SW-N03 and KJCX2-SW-N20).

The Hcp proteins fused with diverse extended-toxin domains represent a novel pattern of antibacterial effectors in type VI secretion systems

PubMed Central

Ma, Jiale; Pan, Zihao; Huang, Jinhu; Sun, Min; Lu, Chengping; Yao, Huochun

2017-01-01

ABSTRACT The type VI secretion system (T6SS) is a widespread molecular weapon deployed by many bacterial species to target eukaryotic host cells or rival bacteria. Using a dynamic injection mechanism, diverse effectors can be delivered by T6SS directly into recipient cells. Here, we report a new family of T6SS effectors encoded by extended Hcps carrying diverse toxin domains. Bioinformatic analyses revealed that these Hcps with C-terminal extension toxins, designated as Hcp-ET, exist widely in the Enterobacteriaceae. To verify our findings, Hcp-ET1 was tested for its antibacterial effect, and showed effective inhibition of target cell growth via the predicted HNH-DNase activity by T6SS-dependent delivery. Further studies showed that Hcp-ET2 mediated interbacterial antagonism via a Tle1 phospholipase (encoded by DUF2235 domain) activity. Notably, comprehensive analyses of protein homology and genomic neighborhoods revealed that Hcp-ET3–4 is fused with 2 toxin domains (Pyocin S3 and Colicin-DNase) C-terminally, and its encoding gene is followed 3 duplications of the cognate immunity genes. However, some bacteria encode a separated hcp-et3 and an orphan et4 (et4O1) genes caused by a termination-codon mutation in the fusion region between Pyocin S3 and Colicin-DNase encoding fragments. Our results demonstrated that both of these toxins had antibacterial effects. Further, all duplications of the cognate immunity protein contributed to neutralize the DNase toxicity of Pyocin S3 and Colicin, which has not been reported previously. In conclusion, we propose that Hcp-ET proteins are polymorphic T6SS effectors, and thus present a novel encoding pattern of T6SS effectors. PMID:28060574

Ab initio calculations for the elastic properties of magnesium under pressure

NASA Astrophysics Data System (ADS)

Sin'Ko, G. V.; Smirnov, N. A.

2009-09-01

Results of ab initio calculations of the elastic constants for the hcp, bcc, double hcp (dhcp), and fcc magnesium in a wide range of pressures are presented. The calculated elastic constants are compared with available experimental and theoretical data. We discuss the effect of the electron topological transition that occurs when the hcp structure is compressed on results of calculations and consider possibility of observing the hcp→dhcp transition on the magnesium Hugoniot.

The Fate of Polyol-Made ZnO and CdS Nanoparticles in Seine River Water (Paris, France).

PubMed

da Rocha, Alice; Sivry, Yann; Gelabert, Alexandre; Beji, Zyed; Benedetti, Marc F; Menguy, Nicolas; Brayner, Roberta

2015-05-01

This study aims to characterize nanoparticles with different compositions and structures as well as seeing their evolutions over time in a natural environment such as Seine river water (Paris, France). Face centered cubic (fcc) and hexagonal (hcp) CdS as well as hexagonal (hcp) ZnO nanoparticles were synthesized by the Polyol method. CdS nanoparticles (i) cfc structure: are agglomerated, present 100 nm length with heterogeneous diameter and 10 m2 g(-1) specific surface area (S(g)) from Brunauer Emett and Teller (BET) measurements; (ii) hcp structure: 20 nm and S(g) = 67 m2 g(-1). ZnO hcp nanoparticles presents 50 nm length and 15 nm diameter and S(g) = 54 m2 g(-1). These results are in agreement with X-ray diffraction (XRD), and small angle X-ray scattering (SAXs). After 48 h interaction with Seine river water, cryo-TEM analysis showed that ZnO nanoparticles form spherical agglomerates with 300 nm diameter; CdS nanoparticles (fcc) are agglomerated presenting large diameters (> 500 nm); and CdS nanoparticles (hcp) are not agglomerated and present the same characteristics of the starting material. After 168h of contact with Seine river water, CdS (fcc) presents only 14% of dissolution, CdS (hcp) presents both 60% dissolution and 30% reprecipitation in a cadmium carbonate form and finally almost 90% of ZnO nanoparticles are dissolved.

The Feasibility of Creating Partnerships Between Palliative Care Volunteers and Healthcare Providers to Support Rural Frail Older Adults and Their Families: An Integrative Review.

PubMed

Connell, Braydon; Warner, Grace; Weeks, Lori E

2017-09-01

Background/Question: Volunteers are important in the support of frail older adults requiring palliative care, especially in rural areas. However, there are challenges associated with volunteer supports related to training, management and capacity to work in partnership with healthcare providers (HCP). This review addresses the question: What is the feasibility of a volunteer-HCP partnership to support frail older adults residing in rural areas, as they require palliative care? This integrative review identified ten articles that met the identified search criteria. Articles were appraised using the Critical Appraisal Skills Programme (CASP) checklists, designed for use across a range of quantitative and qualitative studies. Studies were drawn from international sources to understand how volunteer roles vary by culture and organization; the majority of studies were conducted in North America. Studies varied in methodology, including quantitative, qualitative and educational commentary. Identified factors that were crucial to the feasibility of volunteer-HCP partnerships in rural areas included volunteer training dynamics, relationships between volunteers and HCP, and rural environmental factors. Preliminary evidence indicates that a volunteer-HCP palliative partnership is feasible. However, training policies/procedures, volunteer-HCP relationships, and rural specific designs impact the feasibility of this partnership. Additional research is needed to further establish the feasibility of implementing these partnerships in rural settings.

A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe–Mn–C system exhibiting multicomposition sets

PubMed Central

Nakano, Jinichiro

2013-01-01

The thermodynamic properties of the Fe–Mn–C system were investigated by using an analytical model constructed by a CALPHAD approach. The stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T0, independent of the composition and temperature when other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T0. The driving force for the fcc to hcp transition, defined as a dimensionless value –dGm/(RT), was determined in the presence of Fe-rich and Mn-rich composition sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the compositions studied. The results obtained revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed. PMID:27877555

A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe–Mn–C system exhibiting multicomposition sets

DOE PAGES

Nakano, Jinichiro

2013-03-15

Thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. Stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T 0, independent of composition and temperature when the other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T 0. The driving force for the fcc to hcp transition, defined as a dimensionless value –dG m/(RT), was determined in the presence of Fe-rich and Mn-rich compositionmore » sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the studied compositions. The obtained results revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.« less

Metal-Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal-Organic Framework.

PubMed

Cliffe, Matthew J; Castillo-Martínez, Elizabeth; Wu, Yue; Lee, Jeongjae; Forse, Alexander C; Firth, Francesca C N; Moghadam, Peyman Z; Fairen-Jimenez, David; Gaultois, Michael W; Hill, Joshua A; Magdysyuk, Oxana V; Slater, Ben; Goodwin, Andrew L; Grey, Clare P

2017-04-19

We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed "double cluster" (Hf 12 O 8 (OH) 14 ), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal-organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal-organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials.

Grain Refinement and Texture Mitigation in Low Boron Containing TiAl-Alloys

NASA Astrophysics Data System (ADS)

Hecht, Ulrike; Witusiewicz, Victor T.

2017-12-01

Controlling the grain size and texture of lamellar TiAl-alloys is essential for well-balanced creep and fatigue properties. Excellent refinement and texture mitigation are achieved in aluminum lean alloys by low boron additions of 0.2 at.%. This amount is sufficient to promote in situ formation of ultrafine borides during the last stages of body centered cubic (BCC) solidification. The borides subsequently serve as nucleation sites for hexagonal close packed (HCP) during the BCC-HCP phase transformation. Bridgman solidification experiments with alloy Ti-43Al-8Nb-0.2C-0.2B were performed under a different growth velocity, i.e., cooling rate, to evaluate the HCP grain size distribution and texture. For slow-to-moderate cooling rates, about 65% of HCP grains are randomly oriented, despite the pronounced texture of the parent BCC phase resulting from directional solidification. For high cooling rates, obtained by quenching, texture mitigation is less pronounced. Only 28% of the HCP grains are randomly oriented, the majority being crystallographic variants of the Burgers orientation relationship.

First-Principles Study on the Structural and Magnetic Properties of Iron Hydride

NASA Astrophysics Data System (ADS)

Tsumuraya, Takao; Matsuura, Yasuyuki; Shishidou, Tatsuya; Oguchi, Tamio

2012-06-01

The magnetic and structural properties of iron hydride FeH with the double hexagonal close-packed (dhcp) and hexagonal close-packed (hcp) structures are investigated by first-principles density-functional theory calculations with a spin-polarized form of generalized gradient approximation. All the calculations are performed using all-electron full-potential linearized augmented plane wave method. Both dhcp and hcp FeH are ferromagnetic at ambient pressure. The ferromagnetic ordering of the dhcp structure collapses at a pressure of 48 GPa, while that of the hcp structure vanishes gradually from 48 GPa. The modification in the density of states (DOS) due to the applied pressure causes the collapse of the magnetization. The difference in magnetic moment reduction between dhcp and hcp FeH is attributed to their DOS around the Fermi level. The calculated magnetocrystalline anisotropy energies between in-plane and out-of-plane spin orientations are found to be 124 μeV/Fe for the dhcp structure, and 100 μeV/Fe for the hcp structure. The easy axis is in-plane direction for both structures.

Cement As a Waste Form for Nuclear Fission Products: The Case of 90Sr and Its Daughters [Cement As a Container for Nuclear Fission Products: The Case of 90Sr and Its Daughters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dezerald, Lucile; Kohanoff, Jorge J.; Correa, Alfredo A.

One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of 90Sr insertion and decay in C–S–H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold thismore » radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that 90Sr is stable when it substitutes the Ca 2+ ions in C–S–H, and so is its daughter nucleus 90Y after β-decay. Interestingly, 90Zr, daughter of 90Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Furthermore, cement appears as a suitable waste form for 90Sr storage.« less

Cement As a Waste Form for Nuclear Fission Products: The Case of 90Sr and Its Daughters [Cement As a Container for Nuclear Fission Products: The Case of 90Sr and Its Daughters

DOE PAGES

Dezerald, Lucile; Kohanoff, Jorge J.; Correa, Alfredo A.; ...

2015-10-29

One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of 90Sr insertion and decay in C–S–H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold thismore » radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that 90Sr is stable when it substitutes the Ca 2+ ions in C–S–H, and so is its daughter nucleus 90Y after β-decay. Interestingly, 90Zr, daughter of 90Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Furthermore, cement appears as a suitable waste form for 90Sr storage.« less

Diffusion in cementitious materials. 2: Further investigations of chloride and oxygen diffusion in well-cured OPC and OPC/30%PFA pastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ngala, V.T.; Page, C.L.; Parrott, L.J.

1995-05-01

Steady-state diffusion of dissolved oxygen and chloride ions in hydrated OPC and OPC/30%PFA pastes, hydrated for 2 weeks at 20 C and 10 weeks at 38 C, was studied at water/binder (w/s) ratios 0.4, 0.5, 0.6 and 0.7. Total porosity and a simple measure of capillary porosity, the volume fractions of the water lost in specimens from a saturated surface dry condition to a near-constant weight at 90.7% relative humidity, were also determined. The diffusion rate of chloride ions diminished markedly, to very low values, as the capillary porosity approached zero. For a given w/s ratio or capillary porosity themore » chloride ion diffusion coefficient for OPC/30%PFA pastes was about one order of magnitude smaller than that to OPC pastes. The rate of diffusion of dissolved oxygen also diminished as the capillary porosity reduced but it was still significant as the capillary porosity approached zero. For a given capillary porosity the oxygen diffusion coefficient for OPC/30%PFA pastes was about 30% smaller than that for OPC pastes. The results support the view that chloride ion diffusion in pastes of low capillary porosity is retarded by the surface charge of the hydrated cement gel. In contrast, the hydrated cement gel is much more permeable to the similarly-sized, neutral oxygen molecule.« less

Coexistence pressure for a martensitic transformation from theory and experiment: Revisiting the bcc-hcp transition of iron under pressure

DOE PAGES

Zarkevich, N. A.; Johnson, D. D.

2015-05-12

We revisit results from decades of pressure experiments on the bcc ↔ hcp transformations in iron, which are sensitive to non-hydrostatic conditions and sample size. We emphasize the role of martensitic stress in the observed pressure hysteresis and address the large spread in values for onset pressures of the nucleating phase. From electronic-structure calculations, we find a bcc ↔ hcp equilibrium coexistence pressure of 8.4 GPa. Accounting for non-hydrostatic martensitic stress and a stress-dependent transition barrier, we suggest a pressure inequality for better comparison to experiment and observed hysteresis. We construct the equation of state for bcc and hcp phasesmore » under hydrostatic pressure, and compare to experiments and previous calculations.« less

Human Connectome Project Informatics: quality control, database services, and data visualization

PubMed Central

Marcus, Daniel S.; Harms, Michael P.; Snyder, Abraham Z.; Jenkinson, Mark; Wilson, J Anthony; Glasser, Matthew F.; Barch, Deanna M.; Archie, Kevin A.; Burgess, Gregory C.; Ramaratnam, Mohana; Hodge, Michael; Horton, William; Herrick, Rick; Olsen, Timothy; McKay, Michael; House, Matthew; Hileman, Michael; Reid, Erin; Harwell, John; Coalson, Timothy; Schindler, Jon; Elam, Jennifer S.; Curtiss, Sandra W.; Van Essen, David C.

2013-01-01

The Human Connectome Project (HCP) has developed protocols, standard operating and quality control procedures, and a suite of informatics tools to enable high throughput data collection, data sharing, automated data processing and analysis, and data mining and visualization. Quality control procedures include methods to maintain data collection consistency over time, to measure head motion, and to establish quantitative modality-specific overall quality assessments. Database services developed as customizations of the XNAT imaging informatics platform support both internal daily operations and open access data sharing. The Connectome Workbench visualization environment enables user interaction with HCP data and is increasingly integrated with the HCP's database services. Here we describe the current state of these procedures and tools and their application in the ongoing HCP study. PMID:23707591

[Cytogenetic effects in experimental exposure to the heavy charged particles of galactic cosmic radiation on the Kosmos-1129 biosatellite].

PubMed

Nevzgodina, L V; Maksimova, E N

1982-01-01

The experiment was carried out on lattice (Lactuca sativa) seeds flown in a biocontainer equipped with plastic detectors to record heavy charged particles (HCP). The purpose of the experiment was to determine the yield of aberrant cells as a result of irradiation, and to identify this effect as a function of HCP topography in the seed. The cytogenetic examination of flight seedlings revealed a significant difference between the seeds which were hit with HCP and those that remained intact. This indicates a significant contribution of the heavy component of galactic cosmic rediation into the radiobiological effect. The relationship between the radiobiological effect and the HCP topography in the seed was established: zones of the root and stem meristema proved to be most sensitive targets.

Correlates of a lifetime history of sexually transmitted infections among women who have sex with women in Toronto, Canada: results from a cross-sectional internet-based survey.

PubMed

Logie, Carmen H; Navia, Daniela; Loutfy, Mona R

2015-06-01

Structural drivers of sexually transmitted infections (STI) among women who have sex with women (WSW) have been underexplored. The study objective was to understand sociodemographic, individual, structural, and sexual health factors associated with a lifetime history of STI among WSW. A cross-sectional survey was conducted in 2012 to engage a peer-driven recruitment sample of WSW in Toronto, Canada. Data were collected among a convenience sample of 466 WSW using an online structured interview. Approximately one-fifth (n=89, 19.1%) of participants reported an STI diagnosis history. Participants identifying as bisexual were more likely, and lesbians less likely, to report an STI history than those identifying as queer. In multivariate logistic regression analyses adjusted for sociodemographic variables, STI history was associated with intrapersonal (STI knowledge, HIV/STI risk perceptions), interpersonal (male sex partners in past 3 months, number of lifetime sexual partners) and structural (sexual stigma, history of forced sex, belief healthcare provider (HCP) uncomfortable addressing sexual orientation) factors as well as sexual healthcare uptake (ever had STI/HIV test, STI/Pap test in past 2 years). Gender-non-conforming participants were less likely to report an STI history. This research is among the first to examine intrapersonal, interpersonal and structural factors correlated with an STI history among WSW. Findings highlight the importance of STI prevention strategies for WSW to be tailored to sexual identity, with particular attention to bisexual women's needs. Interventions should connect to sexual healthcare, address sexual stigma and train HCP to better meet the needs of WSW. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Potential Cement Phases in Sedimentary Rocks Drilled by Curiosity at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Morris, R. V.; Bish, D. L.; Chipera, S. J.; Ming, D. W.; Blake, D. F.; Vaniman, D. T.; Bristow, T. F.; Cavanagh, P.; Farmer, J. D.;

Research of Cemented Paste Backfill in Offshore Environments

NASA Astrophysics Data System (ADS)

Wang, Kun; Yang, Peng; Lyu, Wensheng; Lin, Zhixiang

2018-01-01

To promote comprehensive utilization of mine waste tailings and control ground pressure, filling mine stopes with cement paste backfill (CPB) is becoming the most widely used and applicable method in contemporary underground mining. However, many urgent new problems have arisen during the exploitation in offshore mines owing to the complex geohydrology conditions. A series of rheological, settling and mechanical tests were carried out to study the influences of bittern ions on CPB properties in offshore mining. The results showed that: (1) the bittern ion compositions and concentrations of backfill water sampled in mine filling station were similar to seawater. Backfill water mixed CPB slurry with its higher viscosity coefficient was adverse to pipeline gravity transporting; (2) Bleeding rate of backfill water mixed slurry was lower than that prepared with tap water at each cement-tailings ratio; (3) The UCS values of backfill water mixed samples were higher at early curing ages (3d, 7d) and then became lower after longer curing time at 14d and 28d. Therefore, for mine production practice, the offshore environments can have adverse effects on the pipeline gravity transporting and have positive effects on stope dewatering process and early-age strength growth.

Observation of exchange of micropore water in cement pastes by two-dimensional T(2)-T(2) nuclear magnetic resonance relaxometry.

PubMed

Monteilhet, L; Korb, J-P; Mitchell, J; McDonald, P J

2006-12-01

The first detailed analysis of the two-dimensional (2D) NMR T(2)-T(2) exchange experiment with a period of magnetization storage between the two T(2) relaxation encoding periods (T(2)-store-T(2)) is presented. It is shown that this experiment has certain advantages over the T(1)-T(2) variant for the quantization of chemical exchange. New T(2)-store-T(2) 2D 1H NMR spectra of the pore water within white cement paste are presented. Based on these spectra, the exchange rate of water between the two smallest porosity reservoirs is estimated for the first time. It is found to be of the order of 5 ms{-1}. Further, a careful estimate of the pore sizes of these reservoirs is made. They are found to be of the order of 1.4 nm and 10-30 nm , respectively. A discussion of the results is developed in terms of possible calcium silicate hydrate products. A water diffusion coefficient inferred from the exchange rate and the cement particle size is found to compare favorably with the results of molecular-dynamics simulations to be found in the literature.

Performances and working mechanism of a novel polycarboxylate superplasticizer synthesized through changing molecular topological structure.

PubMed

Liu, Xiao; Guan, Jianan; Lai, Guanghong; Wang, Ziming; Zhu, Jie; Cui, Suping; Lan, Mingzhang; Li, Huiqun

2017-10-15

A novel star-shaped polycarboxylate superplasticizer (SPCE) was synthesized through a simple two-step method. 1 H Nuclear Magnetic Resonance ( 1 H NMR) and Infrared Spectroscopy (IR) measurements were used for structural characterization. SPCE and comb-shaped polycarboxylate superplasticizer (CPCE) with same molecular weights were designed and synthesized. The cement paste containing SPCE exhibited better fluidity, fluidity retention, water reduction, 25% lower saturated dosage of PCE, 10% longer setting time, lower hydration heat, more delayed hydration heat evolution and lower amount of hydration products at early ages. Furthermore, the adsorption behavior of SPCE and CPCE in cement pastes and the zeta potential were investigated, and then the working mechanism of SPCE was theoretically explained. It is interesting that changing topological structure from comb-shape to star-shape can achieve the optimization of dispersion effect, and further improve the working effectiveness. The aims of this study are to provide a new avenue to synthesize superplasticizer with novel structure achieving the chemical diversity of superplasticizer structure, and to verify the contribution of optimizing molecular shape. This new type of superplasticizer can be used as a rheology modifying agent in fresh cement-based materials. Copyright © 2017 Elsevier Inc. All rights reserved.

Different Effects of NSF and PCE Superplasticizer on Adsorption, Dynamic Yield Stress and Thixotropy of Cement Pastes

PubMed Central

2018-01-01

This study compares the differences and similarities of two types of superplasticizers—NSF (Naphthalene Sulfonate Formaldehyde) and PCE (PolyCarboxylate Ester)—in fresh cement paste systems, in terms of adsorption, dynamic yield stress, and thixotropic index. Results show that with either NSF or PCE addition, the more superplasticizer is added, the more it is adsorbed and the more it remains in the interstitial pore solution. The dynamic yield stress and thixotropic index also decrease with increasing addition the amount of either superplasticizer. However, NSF is less efficient in decreasing the dynamic yield stress than PCE. More importantly, the decreasing patterns of dynamic yield stress and thixotropic index are different with NSF and PCE additions; this is tied to the adsorption and dispersing mechanisms of these two types of superplasticizers. PMID:29710782

United States Air Force Hearing Conservation Program, Annual Report for Calendar Year 2016

DTIC Science & Technology

Program (HCP) section prepares an annual status report on the USAF HCP in accordance with Air Force Instruction 48-127, Occupational Noise and Hearing...Conservation Program, Section 2.9.2.17, and Department of Defense Instruction 6055.12, Hearing Conservation Program. This report covers calendar year...covers information regarding software implementation status, HCP effectiveness metrics, to include an overview of a few standard reports currently available in the DOEHRS-HC DR database, and our recommendations.

Barriers to optimal diabetes care in Trinidad and Tobago: a health care Professionals' perspective.

PubMed

Roopnarinesingh, Nira; Brennan, Nancyellen; Khan, Claude; Ladenson, Paul W; Hill-Briggs, Felicia; Kalyani, Rita Rastogi

2015-09-19

The republic of Trinidad and Tobago (T&T) is a middle income country with a comparatively high prevalence of diabetes mellitus (DM) compared to others in the Caribbean. To date, there have been no studies on health care professionals' (HCP) perspectives regarding the barriers to achieving optimal care of patients with DM in this country and few previous studies in the Caribbean, yet such perspectives are imperative to develop strategies that reduce the global burden of this disease. An electronic invitation was sent to prospective HCP in T&T inviting them to attend a symposium on DM and cardiovascular disease. A total of 198 HCP participants attended of whom approximately 100 participants completed an Audience Response Survey at the completion of the conference. The Audience Response Survey included questions regarding access to resources, need for prevention and education, and coordination of care for to diabetes care in T&T. Responses were analyzed in aggregate. The 198 HCP participants attending the symposium included mostly nurses (40 %) and physicians (43 %). The most common specialty indicated by the 198 HCP participants was Internal and Family Medicine (28 %), followed by Anesthesiology (7 %), Emergency Medicine (6 %), Endocrinology and Diabetes (5 %) and Cardiology (3 %). Among the ~100 HCP who completed the Audience Response Survey, multiple barriers to achieving optimal care of patients with diabetes were reported such as: limited access to blood testing (75 %), ophthalmological evaluations (96 %), ECGs (69 %), and cardiac stress tests (92 %); inadequate time to screen and evaluate DM complications (95 %); poor access to consultants for referral of difficult cases (77 %); and lack of provider education regarding cardiovascular complications of DM (57 %). HCP agreed that nurses could potentially be considered to have a more active role in the care and prevention of cardiovascular disease and diabetes through leading patient education efforts (98 %), screening patients for complications (91 %), coordinating care efforts (99 %) and educating family members (98 %). The HCP in our study reported significant barriers to achieving optimal diabetes care in T&T. In the future, such barriers to care will need to be addressed in order to respond to the projected growth of diabetes in developing countries both within the Caribbean and globally.

Chemical Reactions of Portland Cement with Aqueous CO2 and Their Impacts on Cement's Mechanical Properties under Geologic CO2 Sequestration Conditions.

PubMed

Li, Qingyun; Lim, Yun Mook; Flores, Katharine M; Kranjc, Kelly; Jun, Young-Shin

2015-05-19

To provide information on wellbore cement integrity in the application of geologic CO2 sequestration (GCS), chemical and mechanical alterations were analyzed for cement paste samples reacted for 10 days under GCS conditions. The reactions were at 95 °C and had 100 bar of either N2 (control condition) or CO2 contacting the reaction brine solution with an ionic strength of 0.5 M adjusted by NaCl. Chemical analyses showed that the 3.0 cm × 1.1 cm × 0.3 cm samples were significantly attacked by aqueous CO2 and developed layer structures with a total attacked depth of 1220 μm. Microscale mechanical property analyses showed that the hardness and indentation modulus of the carbonated layer were 2-3 times greater than for the intact cement, but those in the portlandite-dissolved region decreased by ∼50%. The strength and elastic modulus of the bulk cement samples were reduced by 93% and 84%, respectively. The properties of the microscale regions, layer structure, microcracks, and swelling of the outer layers combined to affect the overall mechanical properties. These findings improve understanding of wellbore integrity from both chemical and mechanical viewpoints and can be utilized to improve the safety and efficiency of CO2 storage.

Predicting the Impact of Multiwalled Carbon Nanotubes on the Cement Hydration Products and Durability of Cementitious Matrix Using Artificial Neural Network Modeling Technique

PubMed Central

Fakhim, Babak; Hassani, Abolfazl; Rashidi, Alimorad; Ghodousi, Parviz

2013-01-01

In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHPloss and CHloss. In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt%) of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise. PMID:24489487

Nano-Inclusions Applied in Cement-Matrix Composites: A Review

PubMed Central

Bastos, Guillermo; Patiño-Barbeito, Faustino; Patiño-Cambeiro, Faustino; Armesto, Julia

2016-01-01

Research on cement-based materials is trying to exploit the synergies that nanomaterials can provide. This paper describes the findings reported in the last decade on the improvement of these materials regarding, on the one hand, their mechanical performance and, on the other hand, the new properties they provide. These features are mainly based on the electrical and chemical characteristics of nanomaterials, thus allowing cement-based elements to acquire “smart” functions. In this paper, we provide a quantitative approach to the reinforcements achieved to date. The fundamental concepts of nanoscience are introduced and the need of both sophisticated devices to identify nanostructures and techniques to disperse nanomaterials in the cement paste are also highlighted. Promising results have been obtained, but, in order to turn these advances into commercial products, technical, social and standardisation barriers should be overcome. From the results collected, it can be deduced that nanomaterials are able to reduce the consumption of cement because of their reinforcing effect, as well as to convert cement-based products into electric/thermal sensors or crack repairing materials. The main obstacle to foster the implementation of such applications worldwide is the high cost of their synthesis and dispersion techniques, especially for carbon nanotubes and graphene oxide. PMID:28774135

Cement As a Waste Form for Nuclear Fission Products: The Case of (90)Sr and Its Daughters.

PubMed

Dezerald, Lucile; Kohanoff, Jorge J; Correa, Alfredo A; Caro, Alfredo; Pellenq, Roland J-M; Ulm, Franz J; Saúl, Andrés

2015-11-17

One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of (90)Sr insertion and decay in C-S-H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that (90)Sr is stable when it substitutes the Ca(2+) ions in C-S-H, and so is its daughter nucleus (90)Y after β-decay. Interestingly, (90)Zr, daughter of (90)Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Therefore, cement appears as a suitable waste form for (90)Sr storage.

Influence of magnesia-to-phosphate molar ratio on microstructures, mechanical properties and thermal conductivity of magnesium potassium phosphate cement paste with large water-to-solid ratio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Biwan, E-mail: xubiwan@gmail.com; Ma, Hongyan, E-mail: mhy1103@gmail.com; Li, Zongjin

2015-02-15

This paper describes the influence of the magnesia-to-phosphate (M/P) molar ratios ranging from 4 to 12, on the properties and microstructures of magnesium potassium phosphate cement (MKPC) pastes with a large water-to-solid ratio (w/s) of 0.50. The setting behavior, compressive strength, tensile bonding strength and thermal conductivity of the MKPC pastes, were investigated. The results show that an increase in the M/P ratio can slow down the setting reaction, and clearly degrade the mechanical strengths, but clearly improve the thermal conductivity of MKPC pastes. Furthermore, micro-characterizations including X-ray diffraction, scanning electron microscopy and thermogravimetric analysis, on the MKPC pastes revealmore » that a lower M/P ratio can facilitate better crystallization of the resultant magnesium potassium phosphate hexahydrate (MKP) and a denser microstructure. Moreover, strong linear correlations are found between the mechanical strengths and the MKP-to-space ratio, and between thermal conductivity and the volume ratio of the unreacted magnesia to the MKP. - Highlights: • Increase of M/P molar ratio causes clear mechanical degradations on MKPC pastes. • Thermal conductivity of MKPC pastes is improved with increase of M/P molar ratio. • Lower M/P ratio leads to better MKP crystallization and denser microstructure. • Strengths of MKPC pastes are linearly correlated to the MKP-to-space ratios. • Thermal conductivity is affected by the volume ratio of unreacted magnesia to MKP.« less

The effect of void creation prior to vertebroplasty on intravertebral pressure and cement distribution in cadaveric spines with simulated metastases.

PubMed

Li, Ka; Yan, Jun; Yang, Qiang; Li, Zhenfeng; Li, Jianmin

2015-01-28

For osteoporosis or spinal metastases, percutaneous vertebroplasty is effective in pain relief and improvement of mobility. However, the complication rate (cement extravasation and fat embolisms) is relatively higher in the treatment of spinal metastases. The presence of tumor tissue plays a significant role in intravertebral pressure and cement distribution and thereby affects the occurrence of complications. We investigated the effect of void creation prior to vertebroplasty on intravertebral pressure and cement distribution in spinal metastases. Eighteen vertebrae (T8-L4) from five cadaveric spines were randomly allocated for two groups (group with and without void) of nine vertebrae each. Defect was created by removing a central core of cancellous bone in the vertebral body and then filling it with 30% or 100% fresh muscle paste by volume to simulate void creation or no void creation, respectively. Then, 20% bone cement by volume of the vertebral body was injected into each specimen through a unipedicular approach at a rate of 3 mL/min. The gender of the donor, vertebral body size, bone density, cement volume, and intravertebral pressure were recorded. Then, computed tomography scans and cross sections were taken to evaluate the cement distribution in vertebral bodies. No significant difference was found between the two groups in terms of the gender of the donor, vertebral body size, bone density, or bone cement volume. The average maximum intravertebral pressure in the group with void creation was significantly lower than that in the group without void creation (1.20 versus 5.09 kPa, P = 0.001). Especially during the filling of void, the difference was more pronounced. Void creation prior to vertebroplasty allowed the bone cement to infiltrate into the lytic defect. In vertebroplasty for spinal metastases, void creation produced lower intravertebral pressure and facilitated cement filling. To reduce the occurrence of complication, it may be an alternative to eliminate the tumor tissue to create a void prior to cement injection.

Assessment of bone healing ability of calcium phosphate cements loaded with platelet lysate in rat calvarial defects.

PubMed

Babo, Pedro S; Carvalho, Pedro P; Santo, Vítor E; Faria, Susana; Gomes, Manuela E; Reis, Rui L

2016-11-01

Injectable calcium phosphate cements have been used as a valid alternative to autologous bone grafts for bone augmentation with the additional advantage of enabling minimally invasive implantation procedures and for perfectly fitting the tissue defect. Nevertheless, they have low biodegradability and lack adequate biochemical signaling to promote bone healing and remodeling. In previous in vitro studies, we observed that the incorporation of platelet lysate directly into the cement paste or loaded in hyaluronic acid microspheres allowed to modulate the cement degradation and the in vitro expression of osteogenic markers in seeded human adipose derived stem cells. The present study aimed at investigating the possible effect of this system in new bone formation when implanted in calvarial bilateral defects in rats. Different formulations were assessed, namely plain calcium phosphate cements, calcium phosphate cements loaded with human platelet lysate, hybrid injectable formulations composed of the calcium phosphate cement incorporating hyaluronin acid non-loaded microparticles (20% hyaluronin acid) or with particles loaded with platelet lysate. The degradability and new bone regrowth were evaluated in terms of mineral volume in the defect, measured by micro-computed tomography and histomorphometric analysis upon 4, 8 and 12 weeks of implantation. We observed that the incorporation of hyaluronin acid microspheres induced an overly rapid cement degradation, impairing the osteoconductive properties of the cement composites. Moreover, the incorporation of platelet lysate induced higher bone healing than the materials without platelet lysate, up to four weeks after surgery. Nevertheless, this effect was not found to be significant when compared to the one observed in the sham-treated group. © The Author(s) 2016.

Blooming gelatin: an individual additive for enhancing nanoapatite precipitation, physical properties, and osteoblastic responses of nanostructured macroporous calcium phosphate bone cements

PubMed Central

Orshesh, Ziba; Hesaraki, Saeed; Khanlarkhani, Ali

2017-01-01

In recent years, there has been a great interest in using natural polymers in the composition of calcium phosphate bone cements to enhance their physical, mechanical, and biological performance. Gelatin is a partially hydrolyzed form of collagen, a natural component of bone matrix. In this study, the effect of blooming gelatin on the nanohydroxyapatite precipitation, physical and mechanical properties, and cellular responses of a calcium phosphate bone cement (CPC) was investigated. Various concentrations of blooming gelatin (2, 5, and 8 wt.%) were used as the cement liquid and an equimolar mixture of tetracalcium phosphate and dicalcium phosphate was used as solid phase. The CPC without any gelatin additive was also evaluated as a control group. The results showed that gelatin accelerated hydraulic reactions of the cement paste, in which the reactants were immediately converted into nanostructured apatite precipitates after hardening. Gelatin molecules induced 4%–10% macropores (10–300 μm) into the cement structure, decreased initial setting time by ~190%, and improved mechanical strength of the as-set cement. Variation in the above-mentioned properties was influenced by the gelatin concentration and progressed with increasing the gelatin content. The numbers of the G-292 osteoblastic cells on gelatin-containing CPCs were higher than the control group at entire culture times (1–14 days), meanwhile better alkaline phosphatase (ALP) activity was determined using blooming gelatin additive. The observation of cell morphologies on the cement surfaces revealed an appropriate cell attachment with extended cell membranes on the cements. Overall, adding gelatin to the composition of CPC improved the handling characteristics such as setting time and mechanical properties, enhanced nanoapatite precipitation, and augmented the early cell proliferation rate and ALP activity. PMID:28176961

Blooming gelatin: an individual additive for enhancing nanoapatite precipitation, physical properties, and osteoblastic responses of nanostructured macroporous calcium phosphate bone cements.

PubMed

Orshesh, Ziba; Hesaraki, Saeed; Khanlarkhani, Ali

2017-01-01

In recent years, there has been a great interest in using natural polymers in the composition of calcium phosphate bone cements to enhance their physical, mechanical, and biological performance. Gelatin is a partially hydrolyzed form of collagen, a natural component of bone matrix. In this study, the effect of blooming gelatin on the nanohydroxyapatite precipitation, physical and mechanical properties, and cellular responses of a calcium phosphate bone cement (CPC) was investigated. Various concentrations of blooming gelatin (2, 5, and 8 wt.%) were used as the cement liquid and an equimolar mixture of tetracalcium phosphate and dicalcium phosphate was used as solid phase. The CPC without any gelatin additive was also evaluated as a control group. The results showed that gelatin accelerated hydraulic reactions of the cement paste, in which the reactants were immediately converted into nanostructured apatite precipitates after hardening. Gelatin molecules induced 4%-10% macropores (10-300 μm) into the cement structure, decreased initial setting time by ~190%, and improved mechanical strength of the as-set cement. Variation in the above-mentioned properties was influenced by the gelatin concentration and progressed with increasing the gelatin content. The numbers of the G-292 osteoblastic cells on gelatin-containing CPCs were higher than the control group at entire culture times (1-14 days), meanwhile better alkaline phosphatase (ALP) activity was determined using blooming gelatin additive. The observation of cell morphologies on the cement surfaces revealed an appropriate cell attachment with extended cell membranes on the cements. Overall, adding gelatin to the composition of CPC improved the handling characteristics such as setting time and mechanical properties, enhanced nanoapatite precipitation, and augmented the early cell proliferation rate and ALP activity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Travesset, Alex

An extensive characterization of the low temperature phase diagram of particles interacting with power law or Lennard-Jones potentials is provided from Lattice Dynamical Theory. For power law systems, only two lattice structures are stable for certain values of the exponent (or softness) (A15, body centered cube (bcc)) and two more (face centered cubic (fcc), hexagonal close packed (hcp)) are always stable. Among them, only the fcc and bcc are equilibrium states. For Lennard-Jones systems, the equilibrium states are either hcp or fcc, with a coexistence curve in pressure and temperature that shows reentrant behavior. The hcp solid never coexists withmore » the liquid. In all cases analyzed, for both power law and Lennard-Jones potentials, the fcc crystal has higher entropy than the hcp. The role of anharmonic terms is thoroughly analyzed and a general thermodynamic integration to account for them is proposed.« less

Accurate Monte Carlo simulations on FCC and HCP Lennard-Jones solids at very low temperatures and high reduced densities up to 1.30

NASA Astrophysics Data System (ADS)

Adidharma, Hertanto; Tan, Sugata P.

2016-07-01

Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T∗ ≤ 1.20) and high densities (0.96 ≤ ρ∗ ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe the properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.

Barriers and facilitators to influenza vaccination and vaccine coverage in a cohort of health care personnel.

PubMed

Naleway, Allison L; Henkle, Emily M; Ball, Sarah; Bozeman, Sam; Gaglani, Manjusha J; Kennedy, Erin D; Thompson, Mark G

2014-04-01

Annual influenza vaccination is recommended for health care personnel (HCP). We describe influenza vaccination coverage among HCP during the 2010-2011 season and present reported facilitators of and barriers to vaccination. We enrolled HCP 18 to 65 years of age, working full time, with direct patient contact. Participants completed an Internet-based survey at enrollment and the end of influenza season. In addition to self-reported data, we collected information about the 2010-2011 influenza vaccine from electronic employee health and medical records. Vaccination coverage was 77% (1,307/1,701). Factors associated with higher vaccination coverage include older age, being married or partnered, working as a physician or dentist, prior history of influenza vaccination, more years in patient care, and higher job satisfaction. Personal protection was reported as the most important reason for vaccination followed closely by convenience, protection of patients, and protection of family and friends. Concerns about perceived vaccine safety and effectiveness and low perceived susceptibility to influenza were the most commonly reported barriers to vaccination. About half of the unvaccinated HCP said they would have been vaccinated if required by their employer. Influenza vaccination in this cohort was relatively high but still fell short of the recommended target of 90% coverage for HCP. Addressing concerns about vaccine safety and effectiveness are possible areas for future education or intervention to improve coverage among HCP. Copyright © 2014 Association for Professionals in Infection Control and Epidemiology, Inc. All rights reserved.

High-Pressure Phase Transition of Iron: A Combined Magnetic Remanence and Mössbauer Study

NASA Astrophysics Data System (ADS)

Wei, Qingguo; McCammon, Catherine; Gilder, Stuart Alan

2017-12-01

We measured Mössbauer spectra and the acquisition of saturation isothermal remanent magnetization in alternating steps on the same sample of polycrystalline, multidiron metal powder in a diamond anvil cell across the body centered cubic (bcc) to hexagonal closed packed (hcp) phase transition at room temperature up to 19.2 GPa. Within the bcc stability field indicated by the presence of magnetic hyperfine splitting, saturation remanent magnetization and sextet area were well correlated during compression and decompression. The areas and dips of the outer (first and sixth) and middle (second and fifth) components of the sextet changed in relative proportion as a function of pressure, which was attributed to rotation of the magnetization direction perpendicular to the gamma-ray source. Sextet peaks disappeared above ˜15 GPa, yet magnetic remanence persisted. Magnetic remanence intensity divided by the fractional area of the sextet, taken to represent bcc Fe, attained maxima at pressures near the boundaries of the hysteretic transition, which we attribute to strain-related magnetostriction effects associated with a distorted bcc-hcp phase. Magnetic remanence observed within the hcp stability field, as defined by the absence of sextet peaks, could be due to a previously described, distorted bcc-hcp phase whose hyperfine field was below detection limits of Mössbauer spectroscopy. Our study suggests that distorted bcc-hcp Fe holds magnetic remanence and leaves open the possibility that this phase carries magnetic remanence into the pressure range where only pure hcp Fe is considered stable.

Long-range empirical potential model: extension to hexagonal close-packed metals.

PubMed

Dai, Y; Li, J H; Liu, B X

2009-09-23

An n-body potential is developed and satisfactorily applied to hcp metals, Co, Hf, Mg, Re, Ti, and Zr, in the form of long-range empirical potential. The potential can well reproduce the lattice constants, c/a ratios, cohesive energies, and the bulk modulus for their stable structures (hcp) and metastable structures (bcc or fcc). Meanwhile, the potential can correctly predict the order of structural stability and distinguish the energy differences between their stable hcp structure and other structures. The energies and forces derived by the potential can smoothly go to zero at cutoff radius, thus completely avoiding the unphysical behaviors in the simulations. The developed potential is applied to study the vacancy, surface fault, stacking fault and self-interstitial atom in the hcp metals. The calculated formation energies of vacancy and divacancy and activation energies of self-diffusion by vacancies are in good agreement with the values in experiments and in other works. The calculated surface energies and stacking fault energies are also consistent with the experimental data and those obtained in other theoretical works. The calculated formation energies generally agree with the results in other works, although the stable configurations of self-interstitial atoms predicted in this work somewhat contrast with those predicted by other methods. The proposed potential is shown to be relevant for describing the interaction of bcc, fcc and hcp metal systems, bringing great convenience for researchers in constructing potentials for metal systems constituted by any combination of bcc, fcc and hcp metals.

Metacarpophalangeal pattern profile analysis: useful diagnostic tool for differentiating between dyschondrosteosis, Turner syndrome, and hypochondroplasia.

PubMed

Laurencikas, E; Sävendahl, L; Jorulf, H

2006-06-01

To assess the value of the metacarpophalangeal pattern profile (MCPP) analysis as a diagnostic tool for differentiating between patients with dyschondrosteosis, Turner syndrome, and hypochondroplasia. Radiographic and clinical data from 135 patients between 1 and 51 years of age were collected and analyzed. The study included 25 patients with hypochondroplasia (HCP), 39 with dyschondrosteosis (LWD), and 71 with Turner syndrome (TS). Hand pattern profiles were calculated and compared with those of 110 normal individuals. Pearson correlation coefficient (r) and multivariate discriminant analysis were used for pattern profile analysis. Pattern variability index, a measure of dysmorphogenesis, was calculated for LWD, TS, HCP, and normal controls. Our results demonstrate that patients with LWD, TS, or HCP have distinct pattern profiles that are significantly different from each other and from those of normal controls. Discriminant analysis yielded correct classification of normal versus abnormal individuals in 84% of cases. Classification of the patients into LWD, TS, and HCP groups was successful in 75%. The correct classification rate was higher (85%) when differentiating two pathological groups at a time. Pattern variability index was not helpful for differential diagnosis of LWD, TS, and HCP. Patients with LWD, TS, or HCP have distinct MCPPs and can be successfully differentiated from each other using advanced MCPP analysis. Discriminant analysis is to be preferred over Pearson correlation coefficient because it is a more sensitive and specific technique. MCPP analysis is a helpful tool for differentiating between syndromes with similar clinical and radiological abnormalities.

Effects of temperature and void on the dynamics and microstructure of structural transition in single crystal iron

NASA Astrophysics Data System (ADS)

Shao, Jian-Li; Wang, Pei; Zhang, Feng-Guo; He, An-Min

2018-06-01

With classic molecular dynamics simulations, we investigate the effects of temperature and void on the bcc to hcp/fcc structural transition in single crystal iron driven by 1D ([0 0 1]) and 3D (uniform) compressions. The results show that the pressure threshold does not reduce monotonously with temperature. The pressure threshold firstly increases and then decreases in the range of 60–360 K under 1D compression, while the variation trend is just opposite under 3D compression. As expected, the initial defect may lower the pressure threshold via heterogenous nucleation. This effect is found to be more distinct at lower temperature, and the heterogenous nucleation mainly results in hcp structure. Under the condition of strain constraint, the products of structural transition will respectively form flaky hcp twin structure ((1 0 0) or (0 1 0)) and lamellar structure ({1 1 0}) of mixed phases under 1D and 3D compressions. During the structural transition, we find the shear stress (1D compression) of hcp phase is always lower than that of bcc phase. The cold energy calculations indicate that the hcp phase is the most stable under high pressure. However, we observe the evident metastable state of bcc phase, whose energy will be much higher than both hcp and fcc phases, and then provides the possibility for the occurrence of fcc nucleation.

Settlement at culverts.

DOT National Transportation Integrated Search

1984-05-01

Past construction methods have resulted in the need for leveling : wedges of asphaltic cement concrete or mud jacking at locations where a : reinforced concrete box culvert was replaced with a pipe culvert . : With the restraint of limited funds, mor...

The influence of calcium nitrate on setting and hardening rate of Portland cement concrete at different temperatures

NASA Astrophysics Data System (ADS)

Kičaitė, A.; Pundienė, I.; Skripkiūnas, G.

2017-10-01

Calcium nitrate in mortars and concrete is used as a multifunctional additive: as set accelerator, plasticizer, long term strength enhancer and as antifreeze admixture. Used binding material and the amount of calcium nitrate, affect the characteristics of the concrete mixture and strength of hardened concrete. The setting time of the initial and the final binding at different temperatures of hardening (+ 20 °C and + 5 °C) of the pastes made of different cements (Portland cement CEM I 42.5 R and Portland limestone cement CEM II/A-LL 42.5 R) and various amounts of calcium nitrate from 1 % until 3 % were investigated. The effect of calcium nitrate on technological characteristics of concrete mixture (the consistency of the mixture, the density, and the amount of air in the mixture), on early concrete strength after 2 and 7 days, as well as on standard concrete strength after 28 days at different temperatures (at + 20 °C and + 5 °C) were analysed.

Friedel's salt formation in sulfoaluminate cements: A combined XRD and {sup 27}Al MAS NMR study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, G.; Boccaleri, E., E-mail: enrico.boccaleri@mfn.unipmn.it; Buzzi, L.

Four different binders based on calcium sulfoaluminate cements have been submitted to accelerated chlorination through ionic exchange on hydrated pastes, in order to investigate their ability to chemically bind chloride ions that might reduce chloride penetration. The composition of hydrated cements before and after the treatment was evaluated by means of an X-Ray Diffraction–{sup 27}Al Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy combined study, allowing to take into account even partially amorphous phases and to make quantitative assumption on the relative abundance of the different aluminium-containing phases. It was found that low SO{sub 3} Sulfoaluminate–Portland ternary systems are the mostmore » effective in binding chloride ions and the active role played by different members of the AFm family in chloride uptake was confirmed. Moreover, a peculiar behavior related to the formation of Friedel's salt in different pH conditions was also established for the different cements.« less

Strength and Deformation of Solid Krypton and Xenon to Mbar Pressures

NASA Astrophysics Data System (ADS)

Brugman, B. L.; Lv, M.; Liu, J.; Park, C.; Popov, D.; Prakapenka, V. B.; Dorfman, S.

2017-12-01

Studying phase equilibria and deformation of rare gas solids (RGS) under pressure provides insight into their behavior in planetary bodies. Their simple bonding properties make them useful analogs for materials with similar structures and other van der Waals bonded materials. He, Ne, and Ar are useful as pressure-transmitting media in diamond anvil cell (DAC) experiments due to their low strength and inert chemistry, and Xe has been proposed as a pressure medium as well, but relatively little is known about the strength of Kr and Xe. The strength of heavy RGS may be affected by a martensitic transition from fcc to hcp structure, which is observed at lower pressures with higher Z. The pressure ranges of this transition in Kr and Xe in previous experimental and computational studies vary from 5 to 29 GPa for Xe and as high as 130 GPa for Kr. The transition may be further complicated by kinetics and multiple transition mechanisms. Modeling of phase equilibria and evaluation of Kr and Xe as pressure media may be improved by examination of elastic and plastic properties at extreme pressure. We studied phase transitions and deformation of Kr and Xe using synchrotron x-ray diffraction at Advanced Photon Source beamlines 13-ID-D and 16-BM-D in the DAC at pressures up to 118 GPa. The martensitic fcc-hcp phase transition begins as peak asymmetry and weak peaks in both Kr and Xe at pressures as low as 5 GPa. Intensity of hcp peaks in Xe increases continuously to 118 GPa. Weak hcp peaks were evident in Kr alongside fcc peaks from 5 to 94 GPa, contrary to theoretical predictions that the hcp transition does not begin below 110-130 GPa. Strength and plasticity of Kr and Xe were obtained by complementary lattice strain and peak width analysis of diffraction patterns in both axial and radial geometries as well as observation of pressure gradients by ruby fluorescence. Xe is approximately hydrostatic with strength comparable to common pressure media at pressures up to 10-12 GPa. Differential stress in Xe increases quickly above 12 GPa and then levels off above 30-50 GPa. This apparent reduction in strength coincides with dramatic growth of hcp peaks, suggesting that weakening is associated with the fcc-hcp transition. Strength is systematically higher for higher-Z RGS below the fcc-hcp transition, but transformation to the hcp structure modifies this trend.

Delayed photo-activation and addition of thio-urethane: Impact on polymerization kinetics and stress of dual-cured resin cements.

PubMed

Faria-E-Silva, André L; Pfeifer, Carmem S

2017-10-01

1) to determine the moment during the redox polymerization reaction of dual cure cements at which to photo-activate the material in order to reduce the polymerization stress, and 2) to evaluate possible synergistic effects between adding chain transfer agents and delayed photo-activation. The two pastes of an experimental dual-cure material were mixed, and the polymerization kinetics of the redox phase was followed. The moment when the material reached its maximum rate of redox polymerization (MRRP) of cement was determined. The degree of conversion (DC) and maximum rates of polymerization (Rp max ) were assessed for materials where: the photoactivation immediately followed material mixing, at MRRP, 1min before and 1min after MRRP. Thio-urethane (TU) additives were synthesized and added to the cement (20% wt), which was then cured under the same conditions. The polymerization kinetics was evaluated for both cements photo-activated immediately or at MRRP, followed by measurements of polymerization stress, flexural strength (FS) and elastic modulus (EM). Knoop hardness was measured before and after ethanol storage. Photo-activating the cement at or after MRRP reduced the Rp max and the polymerization stress. Addition of TU promoted additional and more significant reduction, while not affecting the Rp max . Greater hardness loss was observed for cements with TU, but the final hardness was similar for all experimental conditions. Addition of TU slightly reduced the EM and did not affect the FS. Delayed photo-activation and addition of TU significantly reduce the polymerization stress of dual-cured cements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Selected Bibliography on Fiber-Reinforced Cement and Concrete. Supplement Number 4.

DTIC Science & Technology

1982-08-01

Building Industry," L’Industria Italiana del Cemento , Vol 50, No. 12, Dec 1980, pp 1135-1144. 19. Bartos, P., "Pullout Failure of Fibres Embedded in Cement...Vol 43, No. 11, Nov 1977, pp 561-564. 21. Bassan, M., "Model of Behavior of Fiber-Reinforced Concretes Under Impact Stresses," il Cemento , Vol 74, No...Pastes," il Cemento , Vol 75, No. 3, Jul-Sep 1978, pp 277-284. 210. Mills, R. H., "Age-Embrittlement of Glass-Reinforced Concrete Containing Blastfurance

Research on Reasons for Repeated Falling of Tiles in Internal Walls of Construction

NASA Astrophysics Data System (ADS)

Xu, LiBin; Chen, Shangwei; He, Xinzhou; Zhu, Guoliang

2018-03-01

In view of the quality problem of repeated falling of facing tiles in some construction, the essay had a comparative trial in laboratory on cement mortar which is often used to paste tiles, special tile mortar and dry-hang glue, and measured durability of tile adhesive mortar through freezing and thawing tests. The test results indicated that ordinary cement mortar cannot meet standards due to reasons like big shrinkage and low adhesive. In addition, the ten times of freezing and thawing tests indicated that ordinary cement mortar would directly shell and do not have an adhesive force, and moreover, adhesive force of special tile mortar would reduce. Thus, for tiles of large size which are used for walls, dry-hang techniques are recommended to be used.

Musculoskeletal Deterioration and Hemicorporectomy After Spinal Cord Injury

PubMed Central

Dudley-Javoroski, Shauna

2014-01-01

Background and Purpose The long-term management following an hemicorporectomy (HCP) is not well documented in the scientific literature. The purpose of this case report is to describe the 25-year history of a man with a spinal cord injury who experienced severe musculoskeletal deterioration and hemicorporectomy. Case Description The client sustained T10 complete paraplegia at age 18 years, developed severe decubitus ulcers, and required an HCP as a lifesaving measure 13 years later. The authors describe the chronology of several rehabilitation and prosthetic strategies and speculate on factors that may have contributed to their successes and failures. Outcomes The client survived 12 years after the HCP and returned to independent mobility, self-care, and schooling despite complications with continued skin breakdown. Over the 12 years following discharge from the hospital after the spinal cord injury, he spent 749 days in the hospital. During the 12 years he lived after discharge from the hospital following the HCP, he was hospitalized 190 days. Discussion The authors discuss factors contributing to the client’s musculoskeletal deterioration including chronic wounds, postural deviations, and incomplete adherence to pressure-relief recommendations and raise considerations for physical therapists who treat patients after HCP. PMID:12620090

The Minimal Preprocessing Pipelines for the Human Connectome Project

PubMed Central

Glasser, Matthew F.; Sotiropoulos, Stamatios N; Wilson, J Anthony; Coalson, Timothy S; Fischl, Bruce; Andersson, Jesper L; Xu, Junqian; Jbabdi, Saad; Webster, Matthew; Polimeni, Jonathan R; Van Essen, David C; Jenkinson, Mark

2013-01-01

The Human Connectome Project (HCP) faces the challenging task of bringing multiple magnetic resonance imaging (MRI) modalities together in a common automated preprocessing framework across a large cohort of subjects. The MRI data acquired by the HCP differ in many ways from data acquired on conventional 3 Tesla scanners and often require newly developed preprocessing methods. We describe the minimal preprocessing pipelines for structural, functional, and diffusion MRI that were developed by the HCP to accomplish many low level tasks, including spatial artifact/distortion removal, surface generation, cross-modal registration, and alignment to standard space. These pipelines are specially designed to capitalize on the high quality data offered by the HCP. The final standard space makes use of a recently introduced CIFTI file format and the associated grayordinates spatial coordinate system. This allows for combined cortical surface and subcortical volume analyses while reducing the storage and processing requirements for high spatial and temporal resolution data. Here, we provide the minimum image acquisition requirements for the HCP minimal preprocessing pipelines and additional advice for investigators interested in replicating the HCP’s acquisition protocols or using these pipelines. Finally, we discuss some potential future improvements for the pipelines. PMID:23668970

Metal–Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal–Organic Framework

PubMed Central

2017-01-01

We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed “double cluster” (Hf12O8(OH)14), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal–organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal–organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials. PMID:28343394

Aspects of bonding between resin luting cements and glass ceramic materials.

PubMed

Tian, Tian; Tsoi, James Kit-Hon; Matinlinna, Jukka P; Burrow, Michael F

2014-07-01

The bonding interface of glass ceramics and resin luting cements plays an important role in the long-term durability of ceramic restorations. The purpose of this systematic review is to discuss the various factors involved with the bond between glass ceramics and resin luting cements. An electronic Pubmed, Medline and Embase search was conducted to obtain laboratory studies on resin-ceramic bonding published in English and Chinese between 1972 and 2012. Eighty-three articles were included in this review. Various factors that have a possible impact on the bond between glass ceramics and resin cements were discussed, including ceramic type, ceramic crystal structure, resin luting cements, light curing, surface treatments, and laboratory test methodology. Resin-ceramic bonding has been improved substantially in the past few years. Hydrofluoric acid (HF) etching followed by silanizaiton has become the most widely accepted surface treatment for glass ceramics. However, further studies need to be undertaken to improve surface preparations without HF because of its toxicity. Laboratory test methods are also required to better simulate the actual oral environment for more clinically compatible testing. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effects of Repeated Annual Inactivated Influenza Vaccination among Healthcare Personnel on Serum Hemagglutinin Inhibition Antibody Response to A/Perth/16/2009 (H3N2)-like virus during 2010–11

PubMed Central

Thompson, Mark G.; Naleway, Allison; Fry, Alicia M.; Ball, Sarah; Spencer, Sarah M.; Reynolds, Sue; Bozeman, Sam; Levine, Min; Katz, Jacqueline M.; Gaglani, Manjusha

2016-01-01

Background Recently, lower estimates of influenza vaccine effectiveness (VE) against A(H3N2) virus illness among those vaccinated during the previous season or multiple seasons have been reported; however, it is unclear whether these effects are due to differences in immunogenicity. Methods We performed hemagglutination inhibition antibody (HI) assays on serum collected at preseason, ∼30 days post-vaccination, and postseason from a prospective cohort of healthcare personnel (HCP). Eligible participants had medical and vaccination records for at least four years (since July, 2006), including 578 HCP who received 2010–11 trivalent inactivated influenza vaccine [IIV3, containing A/Perth/16/2009-like A(H3N2)] and 209 HCP who declined vaccination. Estimates of the percentage with high titers (≥40 and > 100) and geometric mean fold change ratios (GMRs) to A/Perth/16/2009-like virus by number of prior vaccinations were adjusted for age, sex, race, education, household size, hospital care responsibilities, and study site. Results Post-vaccination GMRs were inversely associated with the number of prior vaccinations, increasing from 2.3 among those with 4 prior vaccinations to 6.2 among HCP with zero prior vaccinations (F[4,567] = 9.97, p < .0005). Thirty-two percent of HCP with 1 prior vaccination achieved titers >100 compared to only 11% of HCP with 4 prior vaccinations (adjusted odds ratio = 6.8, 95% CI = 3.1 – 15.3). Conclusion Our findings point to an exposure-response association between repeated IIV3 vaccination and HI for A(H3N2) and are consistent with recent VE observations. Ultimately, better vaccines and vaccine strategies may be needed in order to optimize immunogenicity and VE for HCP and other repeated vaccinees. PMID:26813801

Effects of Repeated Annual Inactivated Influenza Vaccination among Healthcare Personnel on Serum Hemagglutinin Inhibition Antibody Response to A/Perth/16/2009 (H3N2)-like virus during 2010-11.

PubMed

Thompson, Mark G; Naleway, Allison; Fry, Alicia M; Ball, Sarah; Spencer, Sarah M; Reynolds, Sue; Bozeman, Sam; Levine, Min; Katz, Jacqueline M; Gaglani, Manjusha

2016-02-10

Recently, lower estimates of influenza vaccine effectiveness (VE) against A(H3N2) virus illness among those vaccinated during the previous season or multiple seasons have been reported; however, it is unclear whether these effects are due to differences in immunogenicity. We performed hemagglutination inhibition antibody (HI) assays on serum collected at preseason, ∼ 30 days post-vaccination, and postseason from a prospective cohort of healthcare personnel (HCP). Eligible participants had medical and vaccination records for at least four years (since July, 2006), including 578 HCP who received 2010-11 trivalent inactivated influenza vaccine [IIV3, containing A/Perth/16/2009-like A(H3N2)] and 209 HCP who declined vaccination. Estimates of the percentage with high titers (≥ 40 and>100) and geometric mean fold change ratios (GMRs) to A/Perth/16/2009-like virus by number of prior vaccinations were adjusted for age, sex, race, education, household size, hospital care responsibilities, and study site. Post-vaccination GMRs were inversely associated with the number of prior vaccinations, increasing from 2.3 among those with 4 prior vaccinations to 6.2 among HCP with zero prior vaccinations (F[4,567]=9.97, p<.0005). Thirty-two percent of HCP with 1 prior vaccination achieved titers >100 compared to only 11% of HCP with 4 prior vaccinations (adjusted odds ratio=6.8, 95% CI=3.1 - 15.3). Our findings point to an exposure-response association between repeated IIV3 vaccination and HI for A(H3N2) and are consistent with recent VE observations. Ultimately, better vaccines and vaccine strategies may be needed in order to optimize immunogenicity and VE for HCP and other repeated vaccinees. Published by Elsevier Ltd.

Nanotechnology-based system for damage-resistant concrete pavements.

DOT National Transportation Integrated Search

2012-08-01

The focus of this study was to explore the use of nanotechnology-based nanofilaments, such as carbon nanotubes (CNTs) and nanofibers (CNFs), as reinforcement for improving the mechanical properties of Portland cement paste and creating multifunctiona...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majid, Z.A.; Mahmud, H.; Shaaban, M.G.

Stabilization/solidification of hazardous wastes is used to convert hazardous metal hydroxide waste sludge into a solid mass with better handling properties. This study investigated the pore size development of ordinary portland cement pastes containing metal hydroxide waste sludge and rice husk ash using mercury intrusion porosimetry. The effects of acre and the addition of rice husk ash on pore size development and strength were studied. It was found that the pore structures of mixes changed significantly with curing acre. The pore size shifted from 1,204 to 324 {angstrom} for 3-day old cement paste, and from 956 to 263 {angstrom} formore » a 7-day old sample. A reduction in pore size distribution for different curing ages was also observed in the other mixtures. From this limited study, no conclusion could be made as to any correlation between strength development and porosity. 10 refs., 6 figs., 3 tabs.« less

Experimental collaboration for thick concrete structures with alkali-silica reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ezell, N Dianne Bull; Hayes, Nolan W.; Lenarduzzi, Roberto

Alkali-Silica Reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, non-crystalline silica in aggregates. An expansive gel is formed within the aggregates which results in micro-cracks in aggregates and adjacent cement paste. The reaction requires the presence of water and has been predominantly detected in groundwater-impacted portions of below grade structures, with limited impact to exterior surfaces in above grade structures. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, shear strength, and tensile strength. Since ASR degradation often takes significant amounts of time, developingmore » ASR detection techniques is important to the sustainability and extended operation lifetimes of nuclear power plants (NPPs). The University of Tennessee, Knoxville (UTK) in collaboration with Oak Ridge National Laboratory (ORNL) designed and built an experiment representative of typical NPP structures to study ASR in thick concrete structures.« less

Experimental collaboration for thick concrete structures with alkali-silica reaction

NASA Astrophysics Data System (ADS)

Ezell, N. Dianne Bull; Hayes, Nolan; Lenarduzzi, Roberto; Clayton, Dwight; Ma, Z. John; Le Pape, Sihem; Le Pape, Yann

2018-04-01

Alkali-Silica Reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, non-crystalline silica in aggregates. An expansive gel is formed within the aggregates which results in micro-cracks in aggregates and adjacent cement paste. The reaction requires the presence of water and has been predominantly detected in groundwater-impacted portions of below grade structures, with limited impact to exterior surfaces in above grade structures. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, shear strength, and tensile strength. Since ASR degradation often takes significant amounts of time, developing ASR detection techniques is important to the sustainability and extended operation lifetimes of nuclear power plants (NPPs). The University of Tennessee, Knoxville (UTK) in collaboration with Oak Ridge National Laboratory (ORNL) designed and built an experiment representative of typical NPP structures to study ASR in thick concrete structures.

Role of distortion in the hcp vs fcc competition in rare-gas solids

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2011-05-01

As a prototype of an initial or intermediate structure between hcp and fcc lattices we consider a distorted bcc crystal. We calculate the temperature and pressure dependences of the lattice parameters for the heavier rare gas solids Ar, Kr, Xe in a quasiharmonic approximation with Aziz potentials, and confirm earlier predictions that the hcp structure predominates over fcc in the bulk within wide ranges of P and T. The situation is different for confined clusters with up to 105 atoms, where, owing to the specific surface energetics and terminations, structures with five-fold symmetry made up of fcc fragments are dominant. As a next step we consider the free relaxation of differently distorted bcc clusters, and show that two types (monoclinic and orthorhombic) of initial distortion are a driving force for the final hcp vs fcc configurations. Possible energy relationships between the initial and final structures are obtained and analyzed.

Ab initio study of structural and mechanical property of solid molecular hydrogens

NASA Astrophysics Data System (ADS)

Ye, Yingting; Yang, Li; Yang, Tianle; Nie, Jinlan; Peng, Shuming; Long, Xinggui; Zu, Xiaotao; Du, Jincheng

2015-06-01

Ab initio calculations based on density functional theory (DFT) were performed to investigate the structural and the elastic properties of solid molecular hydrogens (H2). The influence of molecular axes of H2 on structural relative stabilities of hexagonal close-packed (hcp) and face-centered cubic (fcc) structured hydrogen molecular crystals were systematically investigated. Our results indicate that for hcp structures, disordered hydrogen molecule structure is more stable, while for fcc structures, Pa3 hydrogen molecular crystal is most stable. The cohesive energy of fcc H2 crystal was found to be lower than hcp. The mechanical properties of fcc and hcp hydrogen molecular crystals were obtained, with results consistent with previous theoretical calculations. In addition, the effects of zero point energy (ZPE) and van der Waals (vdW) correction on the cohesive energy and the stability of hydrogen molecular crystals were systematically studied and discussed.

Experiences of older people following the introduction of consumer-directed care to home care packages: A qualitative descriptive study.

PubMed

Day, Jenny; Thorington Taylor, Ann C; Hunter, Sharyn; Summons, Peter; van der Riet, Pamela; Harris, Margaret; Maguire, Jane; Dilworth, Sophie; Jeong, Sarah; Bellchambers, Helen; Haydon, Gunilla; Higgins, Isabel

2018-06-12

To explore the experiences of older people receiving home care package (HCP) support following the introduction of consumer-directed care (CDC) by the Australian government on 1 July 2015. Thirty-one older people with existing HCP support from two service providers in regional New South Wales, Australia, participated in a face-to-face interview and/or a qualitative survey. Analysis revealed the theme of Choices: Preferences, constraints, balancing and choosing. Participants described choosing to live at home with HCP support; however, they were constrained by poor communication and information about service changes and options, personal budgets and access to future care. HCP services remained largely unchanged during transition to CDC. Many aspects of the initial implementation of CDC were challenging for older people. Clear, relevant and timely communication and information about CDC and its consequences for consumers appear to be needed to enhance CDC. © 2018 AJA Inc.

Carbon in iron phases under high pressure

NASA Astrophysics Data System (ADS)

Huang, L.; Skorodumova, N. V.; Belonoshko, A. B.; Johansson, B.; Ahuja, R.

2005-11-01

The influence of carbon impurities on the properties of iron phases (bcc, hcp, dhcp, fcc) has been studied using the first-principles projector augmented-wave (PAW) method for a wide pressure range. It is shown that the presence of ~6 at. % of interstitial carbon has a little effect on the calculated structural sequence of the iron phases under high pressure. The bcc -> hcp transition both for pure iron and iron containing carbon takes place around 9 GPa. According to the enthalpies comparison, the solubility of carbon into the iron solid is decreased by high pressure. The coexistence of iron carbide (Fe3C) + pure hcp Fe is most stable phase at high pressure compared with other phases. Based on the analysis of the pressure-density dependences for Fe3C and hcp Fe, we suggest that there might be some fraction of iron carbide present in the core.

Structural Transitions in Elemental Tin at Ultra High Pressures up to 230 GPa

NASA Astrophysics Data System (ADS)

Gavriliuk, A. G.; Troyan, I. A.; Ivanova, A. G.; Aksenov, S. N.; Starchikov, S. S.; Lyubutin, I. S.; Morgenroth, W.; Glazyrin, K. V.; Mezouar, M.

2017-12-01

The crystal structure of elemental Sn was investigated by synchrotron X-ray diffraction at ultra high pressures up to ˜230 GPa creating in diamond anvil cells. Above 70 GPa, a pure bcc structure of Sn was observed, which is stable up to 160GPa, until an occurrence of the hcp phase was revealed. At the onset of the bcc- hcp transition at pressure of about 160GPa, the drop of the unit cell volume is about 1%. A mixture of the bcc- hcp states was observed at least up to 230GPa, and it seems that this state could exist even up to higher pressures. The fractions of the bcc and hcp phases were evaluated in the pressure range of the phase coexistence 160-230 GPa. The difference between static and dynamic compression and its effect on the V- P phase diagram of Sn are discussed.

3D plotting of growth factor loaded calcium phosphate cement scaffolds.

PubMed

Akkineni, Ashwini Rahul; Luo, Yongxiang; Schumacher, Matthias; Nies, Berthold; Lode, Anja; Gelinsky, Michael

2015-11-01

Additive manufacturing allows to widely control the geometrical features of implants. Recently, we described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of a storable CPC paste based on water-immiscible carrier liquid. Plotting and hardening is conducted under mild conditions allowing the (precise and local) integration of biological components. In this study, we have developed a procedure for efficient loading of growth factors in the CPC scaffolds during plotting and demonstrated the feasibility of this approach. Bovine serum albumin (BSA) or vascular endothelial growth factor (VEGF), used as model proteins, were encapsulated in chitosan/dextran sulphate microparticles which could be easily mixed into the CPC paste in freeze-dried state. In order to prevent leaching of the proteins during cement setting, usually carried out by immersion in aqueous solutions, the plotted scaffolds were aged in water-saturated atmosphere (humidity). Setting in humidity avoided early loss of loaded proteins but provided sufficient amount of water to allow cement setting, as indicated by XRD analysis and mechanical testing in comparison to scaffolds set in water. Moreover, humidity-set scaffolds were characterised by altered, even improved properties: no swelling or crack formation was observed and accordingly, surface topography, total porosity and compressive modulus of the humidity-set scaffolds differed from those of the water-set counterparts. Direct cultivation of mesenchymal stem cells on the humidity-set scaffolds over 21days revealed their cytocompatibility. Maintenance of the bioactivity of VEGF during the fabrication procedure was proven in indirect and direct culture experiments with endothelial cells. Additive manufacturing techniques allow the fabrication of implants with defined architecture (inner pore structure and outer shape). Especially printing technologies conducted under mild conditions allow additionally the (spatially controlled) integration of biological components such as drugs or growth factors. That enables the generation of individualized implants which can better meet the requirements of a patient and of tissue engineering constructs. To our knowledge, simultaneous printing of biological components was up to now only described for hydrogel/biopolymer-based materials which suffer from poor mechanical properties. In contrast, we have developed a procedure (based on 3D plotting of a calcium phosphate cement paste) for the fabrication of designed and growth factor loaded calcium-phosphate-based scaffolds applicable for bone regeneration. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Health system and personal barriers resulting in decreased utilization of HIV and STD testing services among at-risk black men who have sex with men in Massachusetts.

PubMed

Mimiaga, Matthew J; Reisner, Sari L; Bland, Sean; Skeer, Margie; Cranston, Kevin; Isenberg, Deborah; Vega, Benny A; Mayer, Kenneth H

2009-10-01

Testing for HIV and other sexually transmitted diseases (STD) remains a cornerstone of public health prevention interventions. This analysis was designed to explore the frequency of testing, as well as health system and personal barriers to testing, among a community-recruited sample of Black men who have sex with men (MSM) at risk for HIV and STDs. Black MSM (n = 197) recruited via modified respondent-driven sampling between January and July 2008 completed an interviewer-administered assessment, with optional voluntary HIV counseling and testing. Logistic regression procedures examined factors associated with not having tested in the 2 years prior to study enrollment for: (1) HIV (among HIV-uninfected participants, n = 145) and (2) STDs (among the entire mixed serostatus sample, n = 197). The odds ratios and their 95% confidence intervals obtained from this analysis were converted to relative risks. (1) HIV: Overall, 33% of HIV-uninfected Black MSM had not been tested for HIV in the 2 years prior to study enrollment. Factors uniquely associated with not having a recent HIV test included: being less educated; engaging in serodiscordant unprotected sex; and never having been HIV tested at a community health clinic, STD clinic, or jail. (2) STDs: Sixty percent had not been tested for STDs in the 2 years prior to study enrollment, and 24% of the sample had never been tested for STDs. Factors uniquely associated with not having a recent STD test included: older age; having had a prior STD; and never having been tested at an emergency department or urgent care clinic. Overlapping factors associated with both not having had a recent HIV or STD test included: substance use during sex; feeling that using a condom during sex is "very difficult"; less frequent contact with other MSM; not visiting a health care provider (HCP) in the past 12 months; having a HCP not recommend HIV or STD testing at their last visit; not having a primary care provider (PCP); current PCP never recommending they get tested for HIV or STDs. In multivariable models adjusting for relevant demographic and behavioral factors, Black MSM who reported that a HCP recommended getting an HIV test (adjusted relative risk [ARR] = 0.26; p = 0.01) or STD test (ARR = 0.11; p = 0.0004) at their last visit in the past 12 months were significantly less likely to have not been tested for HIV or STDs in the past 2 years. Many sexually active Black MSM do not regularly test for HIV or STDs. HCPs play a pivotal role in encouraging testing for Black MSM. Additional provider training is warranted to educate HCPs about the specific health care needs of Black MSM, in order to facilitate access to timely, culturally competent HIV and STD testing and treatment services for this population.

Implementation of pertussis immunization in health-care personnel.

PubMed

Walther, Kathi; Burckhardt, Marie-Anne; Erb, Thomas; Heininger, Ulrich

2015-04-21

Infection with Bordetella pertussis is most severe in young infants who frequently acquire it from adults. Pertussis immunization in adults 25-29 years of age and all adults in close contact with infants <6 months was introduced in Switzerland in 2012. We immediately implemented this new recommendation in our hospital with a vaccination campaign. Between April 2012 and March 2013 we provided information about the campaign to our staff through several channels and offered appointments for counseling and immunization. After checking indications and contraindications of responding health-care personnel (HCP), informed consent for tetanus-diphtheria-acellular pertussis component (Tdap) immunization was obtained. Specific adverse events (AE) were self-assessed by standardized diaries for 7 days. Statistical analyses were performed using a t-test and Mann-Whitney U-tests SPSS (V21). Of 852 HCP eligible for pertussis immunization, 427 (51%) responded. Of these, 72 (17%) had already received Tdap <10 years ago, 304 (71%) received Tdap now, 38 (9%) were scheduled for vaccination and 12 (3%) declined. Diaries were returned by 272 (89%) of 304 vaccinees; 56 HCP reported ≥1 local AE, most frequently local swelling (8%), redness (2%), redness and swelling (7%), and fever (5=2%); no serious AE occurred. Comprehensive efforts were needed to achieve pertussis immunization coverage of ≥49% among all HCP in our institution. Good tolerability of the vaccine and continuous and individual information to HCP about the rationale and benefits of pertussis immunization contributed to this partial success, but increased efforts are needed to mobilize non-responding HCP. Copyright © 2015 Elsevier Ltd. All rights reserved.

Acoustic neuroma: potential risk factors and audiometric surveillance in the aluminium industry

PubMed Central

Taiwo, Oyebode; Galusha, Deron; Tessier-Sherman, Baylah; Kirsche, Sharon; Cantley, Linda; Slade, Martin D; Cullen, Mark R; Donoghue, A Michael

2014-01-01

Objectives To look for an association between acoustic neuroma (AN) and participation in a hearing conservation programme (HCP) and also for an association between AN and possible occupational risk factors in the aluminium industry. Methods We conducted a case–control analysis of a population of US aluminium production workers in 8 smelters and 43 other plants. Using insurance claims data, 97 cases of AN were identified between 1996 and 2009. Each was matched with four controls. Covariates included participation in a HCP, working in an aluminium smelter, working in an electrical job and hearing loss. Results In the bivariate analyses, covariates associated with AN were participation in the HCP (OR=1.72; 95% CI 1.09 to 2.69) and smelter work (OR=1.88; 95% CI 1.06 to 3.36). Electrical work was not significant (OR=1.60; 95% CI 0.65 to 3.94). Owing to high participation in the HCP in smelters, multivariate subanalyses were required. In the multivariate analyses, participation in the HCP was the only statistically significant risk factor for AN. In the multivariate analysis restricted to employees not working in a smelter, the OR was 1.81 (95% CI 1.04 to 3.17). Hearing loss, an indirect measure of in-ear noise dose, was not predictive of AN. Conclusions Our results suggest the incidental detection of previously undiagnosed tumours in workers who participated in the company-sponsored HCP. The increased medical surveillance among this population of workers most likely introduced detection bias, leading to the identification of AN cases that would have otherwise remained undetected. PMID:25015928

Access to care for children and young people diagnosed with localized scleroderma or juvenile SSc in the UK.

PubMed

Hawley, Daniel P; Baildam, Eileen M; Amin, Tania S; Cruikshank, Mary K; Davidson, Joyce E; Dixon, Jennifer; Martin, Neil S; Ohlsson, Victoria; Pilkington, Clarissa; Rangaraj, Satyapal; Riley, Philip; Sundaramoorthy, Chitra; Walsh, Jo; Foster, Helen E

2012-07-01

To describe pathways of care and referral to paediatric rheumatology from onset of first symptom (noticed by the patient or their family) to diagnosis for children and young people diagnosed with localized scleroderma (LS) or juvenile SSc (jSSc). Retrospective case note audit of patients under paediatric rheumatology care who presented during January 2005-January 2010. Data included disease subtype, sex, age at key points in the referral pathway and health care professional (HCP) contact. All patient and HCP data were pseudo-anonymized in accordance with good clinical practice. Data were from eight UK centres that saw 89 cases: 62 females, 26 males; 73 LS, 16 jSSc. Median time from first symptom to first HCP review was 4 (range 0-72) months (LS) and 1 (range 0-50) month (jSSc). Median time from first symptom to paediatric rheumatology review was 15 (range 1-103) months (LS) and 7 (range 0-50) months (jSSc). Median time from first HCP review to first paediatric rheumatology review was 11 (range 0-103) months (LS) and 2 (range 0-10) months. First HCP seen (74%) was usually a general practitioner. The referring HCP to paediatric rheumatology was usually a dermatologist (56%) for LS. Median time from first symptom to diagnosis was 13 (range 1-102) months (LS) and 8 (range 1-50) months (jSSc). A prolonged interval occurs from first symptom to definitive diagnosis, which may adversely affect outcome. There is a need to raise awareness of this rare diagnosis and facilitate earlier recognition.

"BreastfeedingBasics": web-based education that meets current knowledge competencies.

PubMed

Lewin, Linda Orkin; O'Connor, Mary E

2012-08-01

The United States has not met the majority of the Centers for Disease Control and Prevention goals for breastfeeding duration. Studies have shown a lack of knowledge about breastfeeding by health care professionals and students (HCP/S). Web-based education can be a cost-effective manner of education for HCP/S. "BreastfeedingBasics" is an online free educational program available for use. This study compares information in "BreastfeedingBasics" to the breastfeeding knowledge competencies recommended by the US Breastfeeding Committee (USBC). It also evaluates usage of "BreastfeedingBasics" by users and health care professional faculty. Using anonymous information from Web site users, the authors compared mean pre-test and post-test scores of the modules as a measure of the knowledge gained by HCP/S users. They evaluated usage by demographic information and used a Web-based survey to assess benefits of usage of "BreastfeedingBasics" to faculty. Overall, 15 020 HCP/S used the Web site between April 1999 and December 2009. "BreastfeedingBasics" meets 8 of the 11 USBC knowledge competencies. Mean post-test scores increased (P < .001) for all modules. Faculty reported its benefits to be free, broad scope, and the ability to be completed on the students' own time; 84% of the faculty combined the use of "BreastfeedingBasics" with clinical work. Use of "BreastfeedingBasics" can help HCP/S meet the USBC core breastfeeding knowledge competencies and gain knowledge. Faculty are satisfied with its use. Wider use of "BreastfeedingBasics" to help improve the knowledge of HCP/S may help in improving breastfeeding outcomes.

A first-principles study of CO hydrogenation into methane on molybdenum carbides catalysts

NASA Astrophysics Data System (ADS)

Qi, Ke-Zhen; Wang, Gui-Chang; Zheng, Wen-Jun

2013-08-01

The reaction mechanisms for the CO hydrogenation to produce CH4 on both fcc-Mo2C (100) and hcp-Mo2C (101) surfaces are investigated using density functional theory calculations with the periodic slab model. Through systematic calculations for the mechanisms of the CO hydrogenation on the two surfaces, we found that the reaction mechanisms are the same on both fcc and hcp Mo2C catalysts, that is, CO → HCO → H2CO → H2COH → CH2 → CH3 → CH4. The activation energy of the rate-determining step (CH3 + H → CH4) on fcc-Mo2C (100) (0.84 eV) is lower than that on hcp-Mo2C (101) (1.20 eV), and that is why catalytic activity of fcc-Mo2C is higher than hcp-Mo2C for CO hydrogenation. Our calculated results are consistent with the experimental observations. The activity difference of these two surfaces mainly comes from the co-adsorption energy difference between initial state (IS) and transition state (TS), that is, the co-adsorption energy difference between IS and TS is - 0.04 eV on fcc Mo2C (100), while it is as high as 0.68 eV on hcp Mo2C (101), and thus leading to the lower activation barrier for the reaction of CH3 + H → CH4 on fcc-Mo2C (100) compared to that of hcp-Mo2C (101).

Supplier selection in supply chain management using analytical network process for Indonesian cement industry

NASA Astrophysics Data System (ADS)

Ismail, A. H.; Mahardika, R. Z. Z.

2017-12-01

Supply chain management has increased more significance with the impact of globalization. In the present worldwide market, well-managed supply chain is a standout amongst the most vital requirement to be more competitive in the market. For any organization incorporate cement industry, the most critical decision in initial process of supply chain management is to buy products, materials or services from suppliers. So the role of suppliers is irrefutable important in the global aggressive markets. Appropriate decision of supplier selection can lead to reducing cost in supply chain management. However, it is becoming more complex because of existing various criteria and involving the suitable experts in the company to make valid decision in accordance with its criteria. In this study, the supplier selection of an Indonesia’s leading cement company is analyzed by using one of the popular multi-criteria decision making method, Saaty’s analytical network process (ANP). It is employed for the selection of the best alternative among three suppliers of pasted bag. Supplier with the highest rank comes from several major steps from building the relationship between various criteria to rating the alternatives with the help of experts from the company. The results show that, Communication capability, Flexible payment terms, Ability to meet delivery quantities are the most important criteria in the pasted bag supplier selection in Indonesian cement industry with 0.155, 0.110 and 0.1 ANP coefficient respectively. And based on the ANP coefficient values in limit supermatrix, the A2 or supplier 2 had the highest score with 64.7% or 0.13 ANP coefficient.

OPC Paste Samples Exposed To Aggressive Solutions. Cementitious Barriers Partnership

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langton, C.

2014-11-01

The study presented in this report focused on a low-activity wasteform containing a high-pH pore solution with a significant level of sulfate. The purpose of the study was to improve understanding of the complex concrete/wasteform reactive transport problem, in particular, the role of pH in sulfate attack. Paste samples prepared at three different water-to-cement ratios were tested. The mixtures were prepared with ASTM Type I cement, without additional admixtures. The samples were exposed to two different sodium sulfate contact solutions. The first solution was prepared at 0.15M Na 2SO 4. The second solution also incorporated 0.5M NaOH, to mimic themore » high pH conditions found in Saltstone. The data collected indicated that, in Na 2SO 4 solution, damage occurs to the pastes. In the case of the high-pH sulfate solution (Na 2SO 4 + NaOH), no signs of damage were observed on any of the paste mixtures. These results indicate that the high sulfate content found in the wasteform pore solution will not necessarily lead to severe damage to concrete. Good-quality mixtures could thus prove durable over the long term, and act as an effective barrier to prevent radionuclides from reaching the environment.« less

A modified cementing technique using BoneSource to augment fixation of the acetabulum in a sheep model.

PubMed

Timperley, A John; Nusem, Iulian; Wilson, Kathy; Whitehouse, Sarah L; Buma, Pieter; Crawford, Ross W

2010-08-01

Our aim was to assess in an animal model whether the use of HA paste at the cement-bone interface in the acetabulum improves fixation. We examined, in sheep, the effect of interposing a layer of hydroxyapatite cement around the periphery of a polyethylene socket prior to fixing it using polymethylmethacrylate (PMMA). We performed a randomized study involving 22 sheep that had BoneSource hydroxyapatite material applied to the surface of the acetabulum before cementing a polyethylene cup at arthroplasty. We studied the gross radiographic appearance of the implant-bone interface and the histological appearance at the interface. There were more radiolucencies evident in the control group. Histologically, only sheep randomized into the BoneSource group exhibited a fully osseointegrated interface. Use of the hydroxyapatite material did not give any detrimental effects. In some cases, the material appeared to have been fully resorbed. When the material was evident in histological sections, it was incorporated into an osseointegrated interface. There was no giant cell reaction present. There was no evidence of migration of BoneSource to the articulation. The application of HA material prior to cementation of a socket produced an improved interface. The technique may be useful in humans, to extend the longevity of the cemented implant by protecting the socket interface from the effect of hydrodynamic fluid flow and particulate debris.

On the Utilization of Pozzolanic Wastes as an Alternative Resource of Cement

PubMed Central

Karim, Md. Rezaul; Hossain, Md. Maruf; Khan, Mohammad Nabi Newaz; Zain, Muhammad Fauzi Mohd; Jamil, Maslina; Lai, Fook Chuan

2014-01-01

Recently, as a supplement of cement, the utilization of pozzolanic materials in cement and concrete manufacturing has increased significantly. This study investigates the scope to use pozzolanic wastes (slag, palm oil fuel ash and rice husk ash) as an alkali activated binder (AAB) that can be used as an alternative to cement. To activate these materials, sodium hydroxide solution was used at 1.0, 2.5 and 5.0 molar concentration added into the mortar, separately. The required solution was used to maintain the flow of mortar at 110% ± 5%. The consistency and setting time of the AAB-paste were determined. Mortar was tested for its flow, compressive strength, porosity, water absorption and thermal resistance (heating at 700 °C) and investigated by scanning electron microscopy. The experimental results reveal that AAB-mortar exhibits less flow than that of ordinary Portland cement (OPC). Surprisingly, AAB-mortars (with 2.5 molar solution) achieved a compressive strength of 34.3 MPa at 28 days, while OPC shows that of 43.9 MPa under the same conditions. Although water absorption and porosity of the AAB-mortar are slightly high, it shows excellent thermal resistance compared to OPC. Therefore, based on the test results, it can be concluded that in the presence of a chemical activator, the aforementioned pozzolans can be used as an alternative material for cement. PMID:28788277

On the Utilization of Pozzolanic Wastes as an Alternative Resource of Cement.

PubMed

Karim, Md Rezaul; Hossain, Md Maruf; Khan, Mohammad Nabi Newaz; Zain, Muhammad Fauzi Mohd; Jamil, Maslina; Lai, Fook Chuan

2014-12-05

Recently, as a supplement of cement, the utilization of pozzolanic materials in cement and concrete manufacturing has increased significantly. This study investigates the scope to use pozzolanic wastes (slag, palm oil fuel ash and rice husk ash) as an alkali activated binder (AAB) that can be used as an alternative to cement. To activate these materials, sodium hydroxide solution was used at 1.0, 2.5 and 5.0 molar concentration added into the mortar, separately. The required solution was used to maintain the flow of mortar at 110% ± 5%. The consistency and setting time of the AAB-paste were determined. Mortar was tested for its flow, compressive strength, porosity, water absorption and thermal resistance (heating at 700 °C) and investigated by scanning electron microscopy. The experimental results reveal that AAB-mortar exhibits less flow than that of ordinary Portland cement (OPC). Surprisingly, AAB-mortars (with 2.5 molar solution) achieved a compressive strength of 34.3 MPa at 28 days, while OPC shows that of 43.9 MPa under the same conditions. Although water absorption and porosity of the AAB-mortar are slightly high, it shows excellent thermal resistance compared to OPC. Therefore, based on the test results, it can be concluded that in the presence of a chemical activator, the aforementioned pozzolans can be used as an alternative material for cement.

Examining the association between pain severity and quality-of-life, work-productivity loss, and healthcare resource use among European adults diagnosed with pain.

PubMed

Witt, Edward A; Kenworthy, James; Isherwood, Gina; Dunlop, William C N

2016-09-01

The goal of this research was to quantify the association between pain severity and several health outcomes in a large sample of patients diagnosed with some form of pain. Responses from patients who had been diagnosed with some form of pain (n = 14,459) were drawn from the 2013 EU National Health and Wellness Survey (NHWS; n = 62,000). Respondents reported their subjective pain severity in the past week on a numerical rating scale (0-10) as well as the Medical Outcomes Study Short Form (SF-36), Work Productivity and Activity Impairment Questionnaire (WPAI), and healthcare resource utilization in the past 6 months (healthcare professional (HCP) visits, emergency room (ER) visits, and hospitalizations). Associations between pain severity and health outcomes were examined via a series of regression models controlling for a set of demographic and health-related covariates. After controlling for demographics and comorbidities, pain severity in the past week was shown to be significantly negatively associated with Health Utilities (b = -0.022, p < 0.001) and positively associated with overall WPAI scores (b = 0.18, p < 0.001) and healthcare resource use (Hospitalizations: b = 0.13, p < 0.001; ER Visits: b = 0.14, p < 0.001; HCP Visits: b = 0.08, p < 0.001). The nature of these relationships (linear, curvilinear, etc.) is also explored. This study was a self-report cross-sectional study which may have biased the results and does not allow for causal inferences to be made. Finally, the regression models run were limited to available covariates and, hence, some potentially important covariates may not have been included in these models. The findings suggest that reducing pain severity could result in an increase in patients' quality-of-life and work productivity, and a decrease in healthcare resource use. The equations, linking pain and outcomes, were presented in an accessible format so they could be readily applied in healthcare decision-making.

Effects of calcium leaching on diffusion properties of hardened and altered cement pastes

NASA Astrophysics Data System (ADS)

Kurumisawa, Kiyofumi; Haga, Kazuko; Hayashi, Daisuke; Owada, Hitoshi

2017-06-01

It is very important to predict alterations in the concrete used for fabricating disposal containers for radioactive waste. Therefore, it is necessary to understand the alteration of cementitious materials caused by calcium leaching when they are in contact with ground water in the long term. To evaluate the long-term transport characteristics of cementitious materials, the microstructural behavior of these materials should be considered. However, many predictive models of transport characteristics focus on the pore structure, while only few such models consider both, the spatial distribution of calcium silicate hydrate (C-S-H), portlandite, and the pore spaces. This study focused on the spatial distribution of these cement phases. The auto-correlation function of each phase of cementitious materials was calculated from two-dimensional backscattered electron imaging, and the three-dimensional spatial image of the cementitious material was produced using these auto-correlation functions. An attempt was made to estimate the diffusion coefficient of chloride from the three-dimensional spatial image. The estimated diffusion coefficient of the altered sample from the three-dimensional spatial image was found to be comparable to the measured value. This demonstrated that it is possible to predict the diffusion coefficient of the altered cement paste by using the proposed model.

Performance variances of galvanized steel in mortar and concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hime, W.G.; Machin, M.

Mild steel is used as reinforcement in concrete structures because it is passivated by the highly alkaline cement paste system, preventing typical corrosion. Two processes can corrode the initially passivated steel: air carbonation and chloride (Cl[sup [minus

Assessment of hydration process and mechanical properties of cemented paste backfill by electrical resistivity measurement

NASA Astrophysics Data System (ADS)

Xu, Wenbin; Tian, Xichun; Cao, Peiwang

2018-04-01

Cemented paste backfill (CPB) is an emerging mine backfill technique that allows environmentally hazardous tailings to return to the underground openings or stopes, thereby maximising the safety, efficiency and productivity of operation. Uniaxial compressive strength (UCS) is one of the most commonly used parameters for evaluating the mechanical performance of CPB; the prediction of the UCS of CPB structures from early to advanced ages is of great practical importance. This study aims to investigate the predictability of the UCS of CPB during the hydration process based on electrical resistivity (ER) measurement. For this purpose, the samples prepared at different cement-to-tailing ratios and solid contents were subjected to the ER test during the whole hydration process and UCS tests at 3, 7, 28 days of curing periods. The effect of cement-to-tailing ratio and solid content on the ER and UCS of CPB samples was obtained; the UCS values were correlated with the corresponding ER data. Microstructural analysis was also performed on CPB samples to understand the effect of microstructure on the ER data. The result shows that the ER of CPB decreases first and then increases with the speed which is faster in the previous part than the latter. The ER and UCS of CPB samples increased with increasing cement-to-tailing ratio and solid content and curing periods. A logarithmic relationship is established for each mixture in order to predict the UCS of CPB based on ER. Scanning electron microscope analyses have revealed that the microstructure of the CPB changes with the age from the initial floc to honeycomb, and eventually to the compact clumps. The ER properties of CPB samples were highly associated with their respective microstructural properties. The major output of this study is that ER test is effectively capable for a preliminary prediction of the UCS of CPB.

Geopolymers and Their Uses: Review

NASA Astrophysics Data System (ADS)

Burduhos Nergis, D. D.; Abdullah, M. M. A. B.; Vizureanu, P.; Tahir, M. F. M.

2018-06-01

Outlining the past-present history of the study of alumino-silicate materials, it is well known that geopolymers are inorganic polymers obtained from chemical reaction, also known as geopolymerisation, between an alkaline solution and a solid reach in aluminium and silicone. There is still some controversy surrounding the alkaline activators used to create geopolymer concrete, because homogeneous mixture composed of two (NaOH and Na2SO3) or more chemical in varying proportions are usually highly corrosive and hard to handle. In order to overcome Portland cement many wastes have been used in recent studies to create “friendly” cements by geopolymerisation. In this short review we present basic information’s about how to create and use geopolymers, alkaline activators and raw materials that can be used and conclusions. One question that needs to be asked: Can those materials replace on large scale Portland cement?

Ion release, fluoride charge of and adhesion of an orthodontic cement paste containing microcapsules.

PubMed

Burbank, Brant D; Slater, Michael; Kava, Alyssa; Doyle, James; McHale, William A; Latta, Mark A; Gross, Stephen M

2016-02-01

Dental materials capable of releasing calcium, phosphate and fluoride are of great interest for remineralization. Microencapsulated aqueous solutions of these ions in orthodontic cement demonstrate slow, sustained release by passive diffusion through a permeable membrane without the need for dissolution or etching of fillers. The potential to charge a dental material formulated with microencapsulated water with fluoride by toothbrushing with over the counter toothpaste and the effect of microcapsules on cement adhesion to enamel was determined. Orthodontic cements that contained microcapsules with water and controls without microcapsules were brushed with over-the-counter toothpaste and fluoride release was measured. Adhesion measurements were performed loading orthodontic brackets to failure. Cements that contained microencapsulated solutions of 5.0M Ca(NO3)2, 0.8M NaF, 6.0MK2HPO4 or a mixture of all three were prepared. Ion release profiles were measured as a function of time. A greater fluoride charge and re-release from toothbrushing was demonstrated compared to a control with no microcapsules. Adhesion of an orthodontic cement that contained microencapsulated remineralizing agents was 8.5±2.5MPa compared to the control without microcapsules which was of 8.3±1.7MPa. Sustained release of fluoride, calcium and phosphate ions from cement formulated with microencapsulated remineralizing agents was demonstrated. Orthodontic cements with microcapsules show a release of bioavailable fluoride, calcium, and phosphate ions near the tooth surface while having the ability to charge with fluoride and not effect the adhesion of the material to enamel. Incorporation of microcapsules in dental materials is promising for promoting remineralization. Copyright © 2015 Elsevier Ltd. All rights reserved.

Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition.

PubMed

Glazyrin, K; Pourovskii, L V; Dubrovinsky, L; Narygina, O; McCammon, C; Hewener, B; Schünemann, V; Wolny, J; Muffler, K; Chumakov, A I; Crichton, W; Hanfland, M; Prakapenka, V B; Tasnádi, F; Ekholm, M; Aichhorn, M; Vildosola, V; Ruban, A V; Katsnelson, M I; Abrikosov, I A

2013-03-15

We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation

PubMed Central

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-01-01

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures. PMID:25998415

Search for anisotropy in the Debye-Waller factor of HCP solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2016-02-01

The properties of hexagonal close packed (hcp) solid 4He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid 4He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp 4He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp 4He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm3, and is found to be in good qualitative agreement with experimental data.

75 FR 22835 - Endangered and Threatened Wildlife and Plants; Permits, Santa Cruz County, CA

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-30

... defined under the Act as ``to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect... would then implement the HCP. Construction of a pump house and pipeline for the Ma[ntilde]ana Woods HCP...

Push-out bond strengths of different dental cements used to cement glass fiber posts.

PubMed

Pereira, Jefferson Ricardo; Lins do Valle, Accácio; Ghizoni, Janaina Salomon; Lorenzoni, Fábio César; Ramos, Marcelo Barbosa; Barbosa, Marcelo Ramos; Dos Reis Só, Marcus Vinícius

2013-08-01

Since the introduction of glass fiber posts, irreversible vertical root fractures have become a rare occurrence; however, adhesive failure has become the primary failure mode. The purpose of this study was to evaluate the push-out bond strength of glass fiber posts cemented with different luting agents on 3 segments of the root. Eighty human maxillary canines with similar root lengths were randomly divided into 8 groups (n=10) according to the cement assessed (Rely X luting, Luting and Lining, Ketac Cem, Rely X ARC, Biscem, Duo-link, Rely X U100, and Variolink II). After standardized post space preparation, the root dentin was pretreated for dual-polymerizing resin cements and untreated for the other cements. The mixed luting cement paste was inserted into post spaces with a spiral file and applied to the post surface that was seated into the canal. After 7 days, the teeth were sectioned perpendicular to their long axis into 1-mm-thick sections. The push-out test was performed at a speed of 0.5 mm/min until extrusion of the post occurred. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (α=.05). ANOVA showed that the type of interaction between cement and root location significantly influenced the push-out strength (P<.05). The highest push-out strength results with root location were obtained with Luting and Lining (S3) (19.5 ±4.9 MPa), Ketac Cem (S2) (18.6 ±5.5 MPa), and Luting and Lining (S1) (18.0 ±7.6 MPa). The lowest mean values were recorded with Variolink II (S1) (4.6 ±4.0 MPa), Variolink II (S2) (1.6 ±1.5 MPa), and Rely X ARC (S3) (0.9 ±1.1 MPa). Self-adhesive cements and glass ionomer cements showed significantly higher values compared to dual-polymerizing resin cements. In all root segments, dual-polymerizing resin cements provided significantly lower bond strength. Significant differences among root segments were found only for Duo-link cement. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Bone regeneration capacity of magnesium phosphate cements in a large animal model.

PubMed

Kanter, Britta; Vikman, Anna; Brückner, Theresa; Schamel, Martha; Gbureck, Uwe; Ignatius, Anita

2018-03-15

Magnesium phosphate minerals have captured increasing attention during the past years as suitable alternatives for calcium phosphate bone replacement materials. Here, we investigated the degradation and bone regeneration capacity of experimental struvite (MgNH 4 PO 4 ·6H 2 O) forming magnesium phosphate cements in two different orthotopic ovine implantation models. Cements formed at powder to liquid ratios (PLR) of 2.0 and 3.0 g ml -1 were implanted into trabecular bone using a non-load-bearing femoral drill-hole model and a load-bearing tibial defect model. After 4, 7 and 10 months the implants were retrieved and cement degradation and new bone formation was analyzed by micro-computed tomography (µCT) and histomorphometry. The results showed cement degradation in concert with new bone formation at both defect locations. Both cements were almost completely degraded after 10 months. The struvite cement formed with a PLR of 2.0 g ml -1 exhibited a slightly accelerated degradation kinetics compared to the cement with a PLR of 3.0 g ml -1 . Tartrat-resistant acid phosphatase (TRAP) staining indicated osteoclastic resorption at the cement surface. Energy dispersive X-ray analysis (EDX) revealed that small residual cement particles were mostly accumulated in the bone marrow in between newly formed bone trabeculae. Mechanical loading did not significantly increase bone formation associated with cement degradation. Concluding, struvite-forming cements might be promising bone replacement materials due to their good degradation which is coupled with new bone formation. Recently, the interest in magnesium phosphate cements (MPC) for bone substitution increased, as they exhibit high initial strength, comparably elevated degradation potential and the release of valuable magnesium ions. However, only few in vivo studies, mostly including non-load-bearing defects in small animals, have been performed to analyze the degradation and regeneration capability of MPC derived compounds. The present study examined the in vivo behavior of magnesiumammoniumphosphate hexahydrate (struvite) implants with different porosity in both mechanically loaded and non-loaded defects of merino sheep. For the first time, the effect of mechanical stimuli on the biological outcome of this clinically relevant replacement material is shown and directly compared to the conventional unloaded defect situation in a large animal model. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effects of coarse aggregate on the physical properties of Florida concrete mixes.

DOT National Transportation Integrated Search

2015-10-01

Portland cement concrete is a heterogeneous, composite material composed of coarse and fine granular material : embedded in a matrix of hardened paste. The coarse material is aggregate, which is primarily used as inexpensive filler : and comprises th...

Using side-opening injection cannulas to prevent cement leakage in percutaneous vertebroplasty for osteoporotic vertebral compression fractures, does it really work?

PubMed

Li, Jigang; Li, Tao; Ma, Qiuhong; Li, Jianmin

2017-09-01

Percutaneous vertebroplasty has been widely applied in the treatment of osteoporotic vertebral compression fractures over the past two decades. However as one of the major complications, the rate of cement leakage seems not to be decreased significantly. In this study, the rate of cement leakage was compared between two groups using two different cement injection cannulas. The purpose was to determine the efficacy of side-opening cannula on preventing cement leakage in vertebroplasty for the treatment of osteoporotic vertebral compression fractures. A retrospective study was conducted from January 2013 to December 2015. Totally 225 patients who received bilateral vertebroplasty due to osteoporotic vertebral compression fractures were included in the study. The patients were divided into test group who received vertebroplasty with side-opening cannulas and control group who received vertebroplasty with front-opening cannulas. The patients' medical records were reviewed to determine the bone marrow density, preoperative vertebral compression ratio, preoperative and postoperative VAS, operation time, volume of injected bone cement, rate of cement leakage. Post-operative X-rays and CT scans were utilized to assess the degree of Cement leakage. Comparisons between groups and clinical results on VAS in each group were analyzed with appropriate test. All the patients were performed successfully without symptomatic complications. The back pain was significantly relieved after operation in both groups (P < 0.05). At 6 days and 6 months follow-up, there was no significant difference in the mean VAS score between the two groups (P > 0.05). The rate of cement leakage in the test group was significantly lower than that in the control group (P < 0.05). Percutaneous vertebroplasty with side-opening cannula is a safe and effective minimally invasive method in the treatment of osteoporotic vertebral compression fractures, the rate of cement leakage can be significantly reduced by redirecting the cement flow. Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

A critical analysis of the degree of conversion of resin-based luting cements.

PubMed

Noronha Filho, Jaime Dutra; Brandão, Natasha Lamego; Poskus, Laiza Tatiana; Guimarães, José Guilherme Antunes; Silva, Eduardo Moreira da

2010-01-01

This study analyzed the degree of conversion (DC%) of four resin-based cements (All Ceram, Enforce, Rely X ARC and Variolink II) activated by two modes (chemical and dual), and evaluated the decrease of DC% in the dual mode promoted by the interposition of a 2.0-mm-thick IPS Empress 2 disc. In the chemical activation, the resin-based cements were prepared by mixing equal amounts of base and catalyst pastes. In the dual activation, after mixing, the cements were light-activated at 650 mW/cm² for 40 s. In a third group, the cements were light-activated through a 2.0-mm-thick IPS Empress 2 disc. The DC% was evaluated in a FT-IR spectrometer equipped with an attenuated total reflectance crystal (ATR). The data were analyzed by two-way ANOVA and Tukey's HSD test. For all resin-based cements, the DC% was significantly higher with dual activation, followed by dual activation through IPS Empress 2, and chemical activation (p<0.05). Irrespective of the activation mode, Rely X presented the highest DC% (p<0.05). Chemically activated Variolink and All Ceram showed the worst results (p<0.05). The DC% decreased significantly when activation was performed through a 2.0-mm-thick IPS Empress 2 disc (p<0.05). The results of the present study suggest that resin-based cements could present low DC% when the materials are dually activated through 2.0 mm of reinforced ceramic materials with translucency equal to or less than that of IPS-Empress 2.

A critical analysis of the degree of conversion of resin-based luting cements

PubMed Central

NORONHA FILHO, Jaime Dutra; BRANDÃO, Natasha Lamego; POSKUS, Laiza Tatiana; GUIMARÃES, José Guilherme Antunes; da SILVA, Eduardo Moreira

2010-01-01

Objective This study analyzed the degree of conversion (DC%) of four resin-based cements (All Ceram, Enforce, Rely X ARC and Variolink II) activated by two modes (chemical and dual), and evaluated the decrease of DC% in the dual mode promoted by the interposition of a 2.0-mm-thick IPS Empress 2 disc. Material and Methods In the chemical activation, the resin-based cements were prepared by mixing equal amounts of base and catalyst pastes. In the dual activation, after mixing, the cements were light-activated at 650 mW/cm2 for 40 s. In a third group, the cements were lightactivated through a 2.0-mm-thick IPS Empress 2 disc. The DC% was evaluated in a FT-IR spectrometer equipped with an attenuated total reflectance crystal (ATR). The data were analyzed by two-way ANOVA and Tukey's HSD test. Results For all resin-based cements, the DC% was significantly higher with dual activation, followed by dual activation through IPS Empress 2, and chemical activation (p<0.05). Irrespective of the activation mode, Rely X presented the highest DC% (p<0.05). Chemically activated Variolink and All Ceram showed the worst results (p<0.05). The DC% decreased significantly when activation was performed through a 2.0-mm-thick IPS Empress 2 disc (p<0.05). Conclusions The results of the present study suggest that resin-based cements could present low DC% when the materials are dually activated through 2.0 mm of reinforced ceramic materials with translucency equal to or less than that of IPS-Empress 2. PMID:21085798

Study of leaching mechanisms of caesium ions incorporated in Ordinary Portland Cement.

PubMed

Papadokostaki, Kyriaki G; Savidou, Anastasia

2009-11-15

In this work, a study of the leaching kinetics of Cs(+) ions from cement paste solids, containing inactive Cs(2)SO(4), is presented, involving (i) the parallel performance of leaching experiments at two temperatures (30 degrees C and 70 degrees C); (ii) the performance of leaching tests with intermediate changes in temperature between 30 degrees C and 70 degrees C; (iii) the use of specimens of two different thicknesses and (iv) the determination of the distribution of Cs(+) in the cement specimen at various stages of the leaching test. The results of leaching studies at 30 degrees C with cement solids simulating the composition of real radioactive wastes, containing NaNO(3), small amounts of inactive CsNO(3) and traces of (137)Cs(+) are also reported. Concentration profiles of Cs(+) in inactive specimens showed that part of the Cs(+) (20-30%) tends to be immobilized in the matrix, while elution of the readily leachable portion follows Fick's law reasonably well. No immobilized Cs(+) was detected in the samples containing considerable amounts of NaNO(3). Long-term leaching experiments (up to 8 years) revealed acceleration of the elution process (not detectable in short-term tests), attributable to increase in porosity caused by erosion of the cement matrix. Sorption experiments of Cs(+) ions by cement granules indicated that adsorption on cement pore surfaces is not significant. On the other hand, the leaching tests at two different temperatures or with intermediate changes in temperature between 30 degrees C and 70 degrees C, yielded activation energies that indicated a more complicated kinetic behavior.

Early-age hydration and volume change of calcium sulfoaluminate cement-based binders

NASA Astrophysics Data System (ADS)

Chaunsali, Piyush

Shrinkage cracking is a predominant deterioration mechanism in structures with high surface-to-volume ratio. One way to allay shrinkage-induced stresses is to use calcium sulfoaluminate (CSA) cement whose early-age expansion in restrained condition induces compressive stress that can be utilized to counter the tensile stresses due to shrinkage. In addition to enhancing the resistance against shrinkage cracking, CSA cement also has lower carbon footprint than that of Portland cement. This dissertation aims at improving the understanding of early-age volume change of CSA cement-based binders. For the first time, interaction between mineral admixtures (Class F fly ash, Class C fly ash, and silica fume) and OPC-CSA binder was studied. Various physico-chemical factors such as the hydration of ye'elimite (main component in CSA cement), amount of ettringite (the main phase responsible for expansion in CSA cement), supersaturation with respect to ettringite in cement pore solution, total pore volume, and material stiffness were monitored to examine early-age expansion characteristics. This research validated the crystallization stress theory by showing the presence of higher supersaturation level of ettringite, and therefore, higher crystallization stress in CSA cement-based binders. Supersaturation with respect to ettringite was found to increase with CSA dosage and external supply of gypsum. Mineral admixtures (MA) altered the expansion characteristics in OPC-CSA-MA binders with fixed CSA cement. This study reports that fly ash (FA) behaves differently depending on its phase composition. The Class C FA-based binder (OPC-CSA-CFA) ceased expanding beyond two days unlike other OPC-CSA-MA binders. Three factors were found to govern expansion of CSA cement-based binders: 1) volume fraction of ettringite in given pore volume, 2) saturation level of ettringite, and 3) dynamic modulus. Various models were utilized to estimate the macroscopic tensile stress in CSA cement-based binders without taking into account the viscoelastic effects. For the first time, model based on poromechanics was used to calculate the macroscopic tensile stress that develops in CSA cement-based binders due to crystallization of ettringite. The models enabled a reasonable prediction of tensile stress due to crystallization of ettringite including the failure of an OPC-CSA binder which had high CSA cement content. Elastic strain based on crystallization stress was calculated and compared with the observed strain. A mismatch between observed and calculated elastic strain indicated the presence of early-age creep. Lastly, the application of CSA cement in concretes is discussed to link the paste and concrete behavior.

Acoustic neuroma: potential risk factors and audiometric surveillance in the aluminium industry.

PubMed

Taiwo, Oyebode; Galusha, Deron; Tessier-Sherman, Baylah; Kirsche, Sharon; Cantley, Linda; Slade, Martin D; Cullen, Mark R; Donoghue, A Michael

2014-09-01

To look for an association between acoustic neuroma (AN) and participation in a hearing conservation programme (HCP) and also for an association between AN and possible occupational risk factors in the aluminium industry. We conducted a case-control analysis of a population of US aluminium production workers in 8 smelters and 43 other plants. Using insurance claims data, 97 cases of AN were identified between 1996 and 2009. Each was matched with four controls. Covariates included participation in a HCP, working in an aluminium smelter, working in an electrical job and hearing loss. In the bivariate analyses, covariates associated with AN were participation in the HCP (OR=1.72; 95% CI 1.09 to 2.69) and smelter work (OR=1.88; 95% CI 1.06 to 3.36). Electrical work was not significant (OR=1.60; 95% CI 0.65 to 3.94). Owing to high participation in the HCP in smelters, multivariate subanalyses were required. In the multivariate analyses, participation in the HCP was the only statistically significant risk factor for AN. In the multivariate analysis restricted to employees not working in a smelter, the OR was 1.81 (95% CI 1.04 to 3.17). Hearing loss, an indirect measure of in-ear noise dose, was not predictive of AN. Our results suggest the incidental detection of previously undiagnosed tumours in workers who participated in the company-sponsored HCP. The increased medical surveillance among this population of workers most likely introduced detection bias, leading to the identification of AN cases that would have otherwise remained undetected. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Health-care providers' perspectives on health-insurance access, waiving procedures, and hospital detention practices in Kenya.

PubMed

Mostert, Saskia; Njuguna, Festus; van der Burgt, Renske H M; Musimbi, Joyce; Langat, Sandra; Skiles, Jodi; Seijffert, Anneloes; Sitaresmi, Mei N; Vik, Terry A; van de Ven, Peter M; Kaspers, Gertjan J L

2018-05-09

Patients at Kenyan public hospitals are detained if their families cannot pay their medical bills. Access to health insurance and waiving procedures to prevent detention may be limited. This study explores the perspectives of health-care providers (HCP) on health-insurance access, waiving procedures, and hospital detention practices. A self-administered structured questionnaire was completed by 104 HCP (response rate 78%) involved in childhood cancer care. The perspectives of respondents were as follows: all children with cancer should have health insurance according to 96% of HCP. After parents apply for health insurance, it takes too long before treatment costs are covered (67% agree). Patients with childhood cancer without health insurance have a higher chance of abandoning treatment (82% agree). Hospitals should waive bills of all children with cancer when parents have payment difficulties (69% agree). Waiving procedures take too long (75%). Parents are scared by waiving procedures and may decide never to return to the hospital again (68%). Poor families delay visiting the hospital because they fear hospital detention and first seek alternative treatment (92%). When poor families finally come to the hospital, the disease is in advanced stage already (94%). Parents sometimes have to abandon their detained child at the hospital if they cannot pay hospital bills (68%). Detention of children at the hospital if parents cannot pay their medical bills is not approved by 84% of HCP. HCP acknowledge that access to health insurance needs improvement and that waiving procedures contribute to treatment abandonment. By far, most HCP disapprove of hospital detention practices. These factors warrant urgent attention and adjustment. © 2018 Wiley Periodicals, Inc.

Thermodynamics of dilute 3He-4He solid solutions with hcp structure

NASA Astrophysics Data System (ADS)

Chishko, K. A.

2018-02-01

To interpret the anomalies in heat capacity CV(T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp) 4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution [with CV(T) ˜ T3] from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an "excessive" heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4He) observed experimentally.

Pre-Melting in Iron and Iron Alloys at Earth's Core Conditions: Results from Ab Initio Molecular Dynamics Calculations

NASA Astrophysics Data System (ADS)

Vocadlo, L.; Martorell, B.; Brodholt, J. P.; Wood, I. G.

2014-12-01

Seismically determined S-wave velocities in the Earth's inner core are observed to be much lower (10-30%) than those generally inferred from mineral physics. This is a remarkably large discrepancy - mineralogical models for the mantle and the outer core match the observed velocities to around 1%. In no other large volume of the Earth does such a difference exist. There have been a number of arguments put forward over the years to account for the difference, but none have been universally accepted and our inability to explain the seismic velocities of the inner core remains an uncomfortable truth. Here, we present results from ab initio molecular dynamics calculations performed at 360 GPa and core temperatures on hcp and fcc iron, and on fcc-Fe alloyed with nickel and hcp-Fe alloyed with silicon. The calculated shear modulus, and therefore seismic velocities, of pure hcp-Fe reduces dramatically just prior to melting, providing an elegant explanation for the observed velocities. Calculations on fcc-Fe show no such strong reduction in VS, with a transformation to an hcp-type structure prior to melting; addition of 6.5 atm% and 13 atm% Ni to fcc-Fe raises the temperature of this transition. When silicon is added to hcp-Fe, the pre-melting behaviour is found to be very similar to that of pure hcp-Fe with a strong nonlinear shear weakening just before melting and a corresponding reduction in VS. Because temperatures range from T/Tm = 1 at the inner-outer core boundary to T/Tm ≈ 0.99 at the centre, this strong nonlinear effect on VS should occur in the inner core, providing a compelling explanation for the low VS observed.

In Situ GISAXS investigation of low-temperature aging in oriented surfactant-mesostructured titania thin films

DOE PAGES

Nagpure, Suraj; Das, Saikat; Garlapalli, Ravinder K.; ...

2015-09-11

In this study, the mechanism of forming orthogonally oriented hexagonal close packed (o-HCP) mesostructures during aging of surfactant-templated titania thin films is elucidated using in situ grazing incidence small-angle x-ray scattering (GISAXS) in a controlled-environment chamber. To promote orthogonal orientation, glass slides are modified with crosslinked Pluronic P123, to provide surfaces chemically neutral towards both blocks of mesophase template P123. At 4 °C and 80% RH, the o-HCP mesophase emerges in thin (~60 nm) films by a direct disorder-to-order transition, with no intermediate ordered mesophase. The Pluronic/titania o-HCP GISAXS intensity emerges only after ~10-12 minutes, much slower than previously reportedmore » for smallmolecule surfactants. The Avrami model applied to the data suggests 2D growth with nucleation at the start of the process with a half-life of 39.7 minutes for the aging time just after the induction period of 7 minutes followed by a period consistent with 1D growth kinetics. Surprisingly, films that are thicker (~250 nm) or cast on unmodified slides form o-HCP mesophase domains, but by a different mechanism (2D growth with continuous nucleation) with faster and less complete orthogonal alignment. Thus, the o-HCP mesophase is favored not only 2 by modifying the substrate, but also by aging at 4 °C, which is below the lower consolute temperature (LCST) of the poly(propylene oxide) block of P123. Consistent with this, in situ GISAXS shows that films aged at room temperature (above the LCST of the PPO block) have randomly oriented HCP mesostructure.« less

Influenza vaccination of health care personnel: Experiences with the first year of a national data collection effort.

PubMed

Kalayil, Elizabeth J; Dolan, Samantha B; Lindley, Megan C; Ahmed, Faruque

2015-11-01

The purpose of this project was to evaluate a standardized measure of health care personnel (HCP) influenza vaccination during the first year of implementation. The measure requires acute care hospitals to gather vaccination status data from employees, licensed independent practitioners (LIPs), and adult students/trainees and volunteers. The evaluation included a hospital sampling frame stratified by 4 United States Census Bureau Regions and hospital bed count. The hospitals were selected within strata using simple random sampling and the probability proportional to size method, without replacement. Semi-structured telephone interviews were conducted. Two qualitative data analysts independently coded each interview, and data were synthesized using a thematic analysis. This evaluation took place at hospitals reporting HCP influenza vaccination data as part of the Centers for Medicare & Medicaid Services Hospital Inpatient Quality Reporting (IQR) Program. Participants included the staff at 46 hospitals who were knowledgeable about data collection to fulfill IQR program requirements. Facilitators of data collection included having a small number of HCP, having a data collection system already in place, and providing HCP with advance notice of data collection. Major challenges included the absence of an established tracking process and monitoring HCP not regularly working in the facility, particularly LIPs. More than half of the facilities noted the time- and/or resource-intensive nature of data collection. Most facilities used data collected to meet other reporting requirements beyond the IQR Program. Hospitals implemented a range of data collection methods to comply with reporting requirements. Lessons learned from the first year of measure implementation can be used to enhance data collection practices across HCP groups for future influenza seasons. Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. All rights reserved.

Past occupational dust exposure, depressive symptoms and anxiety in retired Chinese factory workers: the Guangzhou Biobank Cohort Study.

PubMed

Lin, Qiu-Hong; Jiang, Chao-Qiang; Lam, Tai-Hing; Xu, Lin; Jin, Ya-Li; Cheng, Kar-Keung

2014-01-01

Few studies have systematically investigated the impact of past occupational dust exposure on mental health. We examined whether retired factory workers exposed to any of the 4 dusts of silica, cement, coal and asbestos had more depressive symptoms and anxiety in southern China, which has experienced rapid economic development. We used data from the Guangzhou Biobank Cohort Study phase 3. Exposures, lifestyle, symptoms and medical history of the participants were assessed with a structured interview. Self-reported intensity and duration of past occupational dust exposure were used to derive cumulative exposure. Outcome measures were assessed by the 15-item Chinese version of the Geriatric Depression Scale (score ≥5) and the single-item on anxiety. The results revealed that 359 workers were exposed to at least one of the 4 dusts and that 1,253 were unexposed (controls). After adjustment of multiple confounders, greater risks of depressive symptoms were associated with high exposure to silica (odds ratio (OR) of 3.12, 95% CI of 1.17-8.31) and asbestos (OR of 6.90; CI of 1.29-36.75). Risks of anxiety were higher in those with low or high exposures to dust (OR of 2.01 and CI of 1.04-3.87 and OR of 2.29 and CI of 1.30-4.03, respectively) and cement (OR of 3.20 and CI of 1.27-8.07 and OR of 2.30 and CI of 1.09-4.87, respectively), and those with high exposure to silica (OR of 5.29, CI of 1.76-15.92). Past occupational exposures to silica, cement, coal and asbestos dusts were associated with adverse mental health outcomes in retired factory workers. The mechanism underlying the relationship between occupational exposures and psychological symptoms in later life needs to be further studied.

Assessment of the leaching of metallic elements in the technology of solidification in aqueous solution.

PubMed

Rossetti, V Alunno; Di Palma, L; Medici, F

2002-01-01

Results are presented of experiments performed to optimize the solidification/stabilization system for metallic elements in aqueous solution. This system involves mixing cement and a solution of metallic elements in a conventional mixer: the paste thus obtained is transferred drop by drop into a recipient filled with an aqueous solution of NaOH at 20% by weight, in which it solidifies immediately. The separate use of chloride solutions of Li+, Cr3+, Pb2+ and Zn2+ makes it possible to obtain granules displaying various levels of compressive strength. Three different inertization matrices were used in the experiments, the first consisting solely of Portland cement, the second of Portland cement and a superplasticizer additive, and the third of Portland cement partially replaced with silica-fume and superplasticizer. The results of the tests performed showed a very low level of leaching into the alkaline solidification solution for Cr3+, the quantity leached being under 2% as against higher levels for the other metallic elements. For all the considered elements, the best results were obtained by using silica-fume in the inertization matrix.

The Visible Cement Data Set

PubMed Central

Bentz, Dale P.; Mizell, Symoane; Satterfield, Steve; Devaney, Judith; George, William; Ketcham, Peter; Graham, James; Porterfield, James; Quenard, Daniel; Vallee, Franck; Sallee, Hebert; Boller, Elodie; Baruchel, Jose

2002-01-01

With advances in x-ray microtomography, it is now possible to obtain three-dimensional representations of a material’s microstructure with a voxel size of less than one micrometer. The Visible Cement Data Set represents a collection of 3-D data sets obtained using the European Synchrotron Radiation Facility in Grenoble, France in September 2000. Most of the images obtained are for hydrating portland cement pastes, with a few data sets representing hydrating Plaster of Paris and a common building brick. All of these data sets are being made available on the Visible Cement Data Set website at http://visiblecement.nist.gov. The website includes the raw 3-D datafiles, a description of the material imaged for each data set, example two-dimensional images and visualizations for each data set, and a collection of C language computer programs that will be of use in processing and analyzing the 3-D microstructural images. This paper provides the details of the experiments performed at the ESRF, the analysis procedures utilized in obtaining the data set files, and a few representative example images for each of the three materials investigated. PMID:27446723

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fei; Wu, Yuan; Lou, Hongbo

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

Health care providers' perspectives on a weekly text-messaging intervention to engage HIV-positive persons in care (WelTel BC1).

PubMed

Murray, Melanie C M; O'Shaughnessy, Sara; Smillie, Kirsten; Van Borek, Natasha; Graham, Rebecca; Maan, Evelyn J; van der Kop, Mia L; Friesen, Karen; Albert, Arianne; Levine, Sarah; Pick, Neora; Ogilvie, Gina; Money, Deborah; Lester, Richard

2015-10-01

Though evidence shows that Mobile health (mHealth) interventions can improve adherence and viral load in HIV-positive persons, few have studied the health care providers' (HCP) perspective. We conducted a prospective mixed methods pilot study using the WelTel intervention wherein HIV-positive participants (n = 25) received weekly interactive text messages for 6 months. Text message response rate and topic data were collected to illustrate the HCP experience. The aim of this study is to explore intervention acceptability and feasibility from the HCP perspective through a baseline focus group and end of study interviews with HCP impacted by the intervention. Interview data were thematically coded using the Technology Acceptance Model. HCPs identified that the WelTel intervention engaged patients in building relationships, while organizing and streamlining existing mHealth efforts and dealing with privacy issues. HCPs recognized that although workload would augment initially, intervention benefits were many, and went beyond simply improving HIV viral load.

First-principles study of high-pressure structural phase transitions of magnesium

NASA Astrophysics Data System (ADS)

Liu, Qiuxiang; Fan, Changzeng; Zhang, Ruijun

2009-06-01

The structural phase transitions for the hcp, bcc, dhcp, and fcc of magnesium at hydrostatic pressures larger than about 200 GPa at zero temperature are studied by first-principles total energy calculations. The plane-wave basis pseudopotential method has been adopted, in which the generalized gradient approximation implanted in the CASTEP code is employed. By comparing the enthalpy differences of the hcp structure with other three structures under different pressures, it can be seen that when the pressure becomes higher than about 65, 130, and 190 GPa, the bcc, dhcp, and fcc structures become more stable relative to the hcp structure, respectively. Due to the lowest enthalpy value of the bcc structure above 65 GPa, it can be deduced that magnesium may transform to the bcc structure from the ground state hcp structure around 65 GPa, but no further phase transitions occur without additionally applying high temperature. In addition, the equation of state of magnesium is calculated, indicating that bcc structure is the softest phase.

Polymorphism in a high-entropy alloy

DOE PAGES

Zhang, Fei; Wu, Yuan; Lou, Hongbo; ...

2017-06-01

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

Superconductivity under high pressure in the binary compound CaLi2

NASA Astrophysics Data System (ADS)

Debessai, M.; Matsuoka, T.; Hamlin, J. J.; Gangopadhyay, A. K.; Schilling, J. S.; Shimizu, K.; Ohishi, Y.

2008-12-01

Feng predicted for CaLi2 highly anomalous properties with possible superconductivity under very high pressures, including for the hcp polymorph a significant lattice bifurcation at pressures above 47 GPa. More recently, however, Feng suggested that for pressures exceeding 20 GPa CaLi2 may dissociate into elemental Ca and Li. Here we present for hcp CaLi2 measurements of the electrical resistivity and ac susceptibility to low temperatures under pressures as high as 81 GPa. Pressure-induced superconductivity is observed in the pressure range of 11-81 GPa, with Tc reaching values as high as 13 K. X-ray diffraction studies to 54 GPa at 150 K reveal that hcp CaLi2 undergoes a structural phase transition above 23 GPa to orthorhombic but does not dissociate into elemental Ca and Li. In the hcp phase a fit of the equation of state with the Murnaghan equation yields the bulk modulus Bo=15(2)GPa and dBo/dP=3.2(6) .

Traditional Portland cement and MgO-based cement: a promising combination?

NASA Astrophysics Data System (ADS)

Tonelli, Monica; Martini, Francesca; Calucci, Lucia; Geppi, Marco; Borsacchi, Silvia; Ridi, Francesca

2017-06-01

MgO/SiO2 cements are materials potentially very useful for radioactive waste disposal, but knowledge about their physico-chemical properties is still lacking. In this paper we investigated the hydration kinetics of cementitious formulations prepared by mixing MgO/SiO2 and Portland cement in different proportions and the structural properties of the hydrated phases formed in the first month of hydration. In particular, the hydration kinetics was investigated by measuring the free water index on pastes by means of differential scanning calorimetry, while the structural characterization was carried out by combining thermal (DTA), diffractometric (XRD), and spectroscopic (FTIR, 29Si solid state NMR) techniques. It was found that calcium silicate hydrate (C-S-H) and magnesium silicate hydrate (M-S-H) gels mainly form as separate phases, their relative amount and structural characteristics depending on the composition of the hydrated mixture. Moreover, the composition of the mixtures strongly affects the kinetics of hydration and the pH of the aqueous phase in contact with the cementitious materials. The results here reported show that suitable mixtures of Portland cement and MgO/SiO2 could be used to modify the properties of hydrated phases with potential application in the storage of nuclear waste in clayey disposal.

Time Savings with Rituximab Subcutaneous Injection versus Rituximab Intravenous Infusion: A Time and Motion Study in Eight Countries

PubMed Central

De Cock, Erwin; Kritikou, Persefoni; Sandoval, Mariana; Tao, Sunning; Wiesner, Christof; Carella, Angelo Michele; Ngoh, Charles; Waterboer, Tim

2016-01-01

Background Rituximab is a standard treatment for non-Hodgkin lymphoma. The SABRINA trial (NCT01200758) showed that a subcutaneous (SC) rituximab formulation did not compromise efficacy or safety compared with intravenous (IV) infusion. We aimed to quantify active healthcare professional (HCP) time and patient chair time for rituximab SC and IV, including potential time savings. Methods This non-interventional time and motion study was run in eight countries and 30 day oncology units. Rituximab SC data were collected alongside the MabCute trial (NCT01461928); IV data were collected per routine real-world practice. Trained observers recorded active HCP time for pre-specified tasks (stopwatch) and chair time (time of day). A random intercept model was used to analyze active HCP time (by task and for all tasks combined) in the treatment room and drug preparation area, drug administration duration, chair time and patient treatment room time by country and/or across countries. Active HCP and chair time were extrapolated to a patient’s first year of treatment (11 rituximab sessions). Results Mean active HCP time was 35.0 and 23.7 minutes for IV and SC process, respectively (-32%, p <0.0001). By country, relative reduction in time was 27–58%. Absolute reduction in extrapolated active HCP time (first year of treatment) was 1.1–5.2 hours. Mean chair time was 262.1 minutes for IV, including 180.9 minutes infusion duration, vs. 67.3 minutes for SC, including 8.3 minutes SC injection administration (-74%, p <0.0001). By country, relative reduction was 53–91%. Absolute reduction in extrapolated chair time for the first year of treatment was 3.1–5.5 eight-hour days. Conclusions Compared with rituximab IV, rituximab SC was associated with reduced chair time and active HCP time. The latter could be invested in other activities, whereas the former may lead to more available appointments, reducing waiting lists and increasing the efficiency of day oncology units. Trial Registration ClinicalTrials.gov NCT01200758 PMID:27362533

Pore orientation effects on the kinetics of mesostructure loss in surfactant templated titania thin films

DOE PAGES

Das, Saikat; Nagpure, Suraj; Garlapalli, Ravinder K.; ...

2016-12-17

The mesostructure loss kinetics are measured as a function of the orientation of micelles in 2D hexagonal close packed (HCP) columnar mesostructured titania thin films using in situ grazing incidence small angle x-ray scattering (GISAXS). Complementary supporting information is provided by ex situ scanning electron microscopy. Pluronic surfactant P123 acts as the template to synthesize HCP structured titania thin films. When the glass substrates are modified with crosslinked P123, the micelles of the HCP mesophase align orthogonal to the films, whereas a mix of parallel and orthogonal alignment is found on unmodified glass. The rate of mesostructure loss of orthogonallymore » oriented (o-HCP) thin films (~60 nm thickness) prepared on modified substrate is consistently found to be less by a factor of 2.5 ± 0.35 than that measured for mixed orientation HCP films on unmodified substrates. The activation energy for mesostructure loss is only slightly greater for films on modified glass (155 ± 25 kJ/mol -1) than on unmodified (128 kJ/mol -1), which implies that the rate difference stems a greater activation entropy for mesostructure loss in o-HCP titania films. Nearly perfect orthogonal orientation of micelles on modified surfaces contributes to the lower rate of mesostructure loss by supporting the anisotropic stresses that develop within the films during annealing due to continuous curing, sintering and crystallization into the anatase phase during high temperature calcination (>450 °C). Because the film thickness dictates the propagation of orientation throughout the films and the degree of confinement, thicker (~250 nm) films cast onto P123-modified substrates have a much lower activation energy for mesostructure loss (89 ± 27 kJ/mol -1) due to the mix of orientations found in the films. Thus, in conclusion, this kinetic study shows that thin P123- templated o-HCP titania films are not only better able to achieve good orthogonal alignment of 3 the mesophase relative to thicker films or films on unmodified substrates, but that alignment of the mesophase in the films stabilizes the mesophase against thermally-induced mesostructure loss.« less

Pore orientation effects on the kinetics of mesostructure loss in surfactant templated titania thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Saikat; Nagpure, Suraj; Garlapalli, Ravinder K.

The mesostructure loss kinetics are measured as a function of the orientation of micelles in 2D hexagonal close packed (HCP) columnar mesostructured titania thin films using in situ grazing incidence small angle x-ray scattering (GISAXS). Complementary supporting information is provided by ex situ scanning electron microscopy. Pluronic surfactant P123 acts as the template to synthesize HCP structured titania thin films. When the glass substrates are modified with crosslinked P123, the micelles of the HCP mesophase align orthogonal to the films, whereas a mix of parallel and orthogonal alignment is found on unmodified glass. The rate of mesostructure loss of orthogonallymore » oriented (o-HCP) thin films (~60 nm thickness) prepared on modified substrate is consistently found to be less by a factor of 2.5 ± 0.35 than that measured for mixed orientation HCP films on unmodified substrates. The activation energy for mesostructure loss is only slightly greater for films on modified glass (155 ± 25 kJ/mol -1) than on unmodified (128 kJ/mol -1), which implies that the rate difference stems a greater activation entropy for mesostructure loss in o-HCP titania films. Nearly perfect orthogonal orientation of micelles on modified surfaces contributes to the lower rate of mesostructure loss by supporting the anisotropic stresses that develop within the films during annealing due to continuous curing, sintering and crystallization into the anatase phase during high temperature calcination (>450 °C). Because the film thickness dictates the propagation of orientation throughout the films and the degree of confinement, thicker (~250 nm) films cast onto P123-modified substrates have a much lower activation energy for mesostructure loss (89 ± 27 kJ/mol -1) due to the mix of orientations found in the films. Thus, in conclusion, this kinetic study shows that thin P123- templated o-HCP titania films are not only better able to achieve good orthogonal alignment of 3 the mesophase relative to thicker films or films on unmodified substrates, but that alignment of the mesophase in the films stabilizes the mesophase against thermally-induced mesostructure loss.« less

A SAT Based Effective Algorithm for the Directed Hamiltonian Cycle Problem

NASA Astrophysics Data System (ADS)

Jäger, Gerold; Zhang, Weixiong

The Hamiltonian cycle problem (HCP) is an important combinatorial problem with applications in many areas. While thorough theoretical and experimental analyses have been made on the HCP in undirected graphs, little is known for the HCP in directed graphs (DHCP). The contribution of this work is an effective algorithm for the DHCP. Our algorithm explores and exploits the close relationship between the DHCP and the Assignment Problem (AP) and utilizes a technique based on Boolean satisfiability (SAT). By combining effective algorithms for the AP and SAT, our algorithm significantly outperforms previous exact DHCP algorithms including an algorithm based on the award-winning Concorde TSP algorithm.

Evaluation of stress in high pressure radial diffraction: application to hcp Co

NASA Astrophysics Data System (ADS)

Merkel, S.; Tome, C.; Wenk, H.

2007-12-01

Understanding the coupling between elastic and plastic behaviour in hcp Co plastically deformed is important as it can serve as a starting model for improving our understanding of hcp-Fe, the main constituent of the Earth's inner core. For many years, the radial diffraction technique has been used to study mechanical properties under pressure. In those experiments, a polycrystalline sample is plastically deformed between two diamond anvils and lattice spacings are measured using diffraction, with the incoming x-ray beam perpendicular to the compression direction. From the variations of the d-spacings with the diffraction angle, we deduce information on the hydrostatic and deviatoric stress in the sample, while the variations of diffraction intensities provide information on the lattice preferred orientations within the polycrystal. Theories have been developed to relate the observed lattice strains to elastic moduli and stress within the sample (1). However, those models do not account for the effect of plastic deformation and, as a consequence, stress determinations can be inconsistent between lattice planes. In particular, experiments on cobalt have shown that plasticity effects on lattice strains were particularly large in hcp metals (2). This implies that the elastic moduli previously measured for hcp-iron using this technique are not directly related to single-crystal elastic moduli(3). Addressing this problem requires us to consider plastic relaxation, in addition to elastic effects. This can be done using polycrystal elasto-plastic models, which account for slip activity and the threshold stresses associated with their activation. Here, we present new results on modeling radial diffraction experiments using an elasto-plastic self-consistent (EPSC) model and show how the model can be used to interpret radial diffraction data on hcp-Co. More important, we also show how this can be used to derive information about the active slip systems and their critical stress of activation. (1) A.K. Singh, C. Balasingh, Mao, R.J. Hemley & J. Shu, Analysis of lattice strains measured under non- hydrostatic pressure, J. Appl. Phys., 1998, 83, 7567-7575 (2) S. Merkel, N. Miyajima, D. Antonangeli, G. Fiquet & T. Yagi, Lattice preferred orientation and stress in polycrystalline hcp-Co plastically deformed under high pressure, J. Appl. Phys., 2006, 100, 023510 (3) D. Antonangeli, S. Merkel & D. L. Farber, Elastic anisotropy in hcp metals at high pressure and the sound wave anisotropy of the Earth's inner core, Geophys. Res. Lett., 2006, 33, L24303

A new electric method for non-invasive continuous monitoring of stroke volume and ventricular volume-time curves

PubMed Central

2012-01-01

Background In this paper a new non-invasive, operator-free, continuous ventricular stroke volume monitoring device (Hemodynamic Cardiac Profiler, HCP) is presented, that measures the average stroke volume (SV) for each period of 20 seconds, as well as ventricular volume-time curves for each cardiac cycle, using a new electric method (Ventricular Field Recognition) with six independent electrode pairs distributed over the frontal thoracic skin. In contrast to existing non-invasive electric methods, our method does not use the algorithms of impedance or bioreactance cardiography. Instead, our method is based on specific 2D spatial patterns on the thoracic skin, representing the distribution, over the thorax, of changes in the applied current field caused by cardiac volume changes during the cardiac cycle. Since total heart volume variation during the cardiac cycle is a poor indicator for ventricular stroke volume, our HCP separates atrial filling effects from ventricular filling effects, and retrieves the volume changes of only the ventricles. Methods ex-vivo experiments on a post-mortem human heart have been performed to measure the effects of increasing the blood volume inside the ventricles in isolation, leaving the atrial volume invariant (which can not be done in-vivo). These effects have been measured as a specific 2D pattern of voltage changes on the thoracic skin. Furthermore, a working prototype of the HCP has been developed that uses these ex-vivo results in an algorithm to decompose voltage changes, that were measured in-vivo by the HCP on the thoracic skin of a human volunteer, into an atrial component and a ventricular component, in almost real-time (with a delay of maximally 39 seconds). The HCP prototype has been tested in-vivo on 7 human volunteers, using G-suit inflation and deflation to provoke stroke volume changes, and LVot Doppler as a reference technique. Results The ex-vivo measurements showed that ventricular filling caused a pattern over the thorax quite distinct from that of atrial filling. The in-vivo tests of the HCP with LVot Doppler resulted in a Pearson’s correlation of R = 0.892, and Bland-Altman plotting of SV yielded a mean bias of -1.6 ml and 2SD =14.8 ml. Conclusions The results indicate that the HCP was able to track the changes in ventricular stroke volume reliably. Furthermore, the HCP produced ventricular volume-time curves that were consistent with the literature, and may be a diagnostic tool as well. PMID:22900831

Development of low-pH cementitious materials for HLRW repositories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia Calvo, J.L., E-mail: jolgac@ietcc.csic.e; Hidalgo, A.; Alonso, C.

One of the most accepted engineering construction concepts of underground repositories for high radioactive waste considers the use of low-pH cementitious materials. This paper deals with the design of those based on Ordinary Portland Cements with high contents of silica fume and/or fly ashes that modify most of the concrete 'standard' properties, the pore fluid composition and the microstructure of the hydrated products. Their resistance to long-term groundwater aggression is also evaluated. The results show that the use of OPC cement binders with high silica content produces low-pH pore waters and the microstructure of these cement pastes is different frommore » the conventional OPC ones, generating C-S-H gels with lower CaO/SiO{sub 2} ratios that possibly bind alkali ions. Leaching tests show a good resistance of low-pH concretes against groundwater aggression although an altered front can be observed.« less

HCP: A Flexible CNN Framework for Multi-label Image Classification.

PubMed

Wei, Yunchao; Xia, Wei; Lin, Min; Huang, Junshi; Ni, Bingbing; Dong, Jian; Zhao, Yao; Yan, Shuicheng

2015-10-26

Convolutional Neural Network (CNN) has demonstrated promising performance in single-label image classification tasks. However, how CNN best copes with multi-label images still remains an open problem, mainly due to the complex underlying object layouts and insufficient multi-label training images. In this work, we propose a flexible deep CNN infrastructure, called Hypotheses-CNN-Pooling (HCP), where an arbitrary number of object segment hypotheses are taken as the inputs, then a shared CNN is connected with each hypothesis, and finally the CNN output results from different hypotheses are aggregated with max pooling to produce the ultimate multi-label predictions. Some unique characteristics of this flexible deep CNN infrastructure include: 1) no ground-truth bounding box information is required for training; 2) the whole HCP infrastructure is robust to possibly noisy and/or redundant hypotheses; 3) the shared CNN is flexible and can be well pre-trained with a large-scale single-label image dataset, e.g., ImageNet; and 4) it may naturally output multi-label prediction results. Experimental results on Pascal VOC 2007 and VOC 2012 multi-label image datasets well demonstrate the superiority of the proposed HCP infrastructure over other state-of-the-arts. In particular, the mAP reaches 90.5% by HCP only and 93.2% after the fusion with our complementary result in [44] based on hand-crafted features on the VOC 2012 dataset.

Implication of health care personnel in measles transmission

PubMed Central

Torner, Núria; Solano, Ruben; Rius, Cristina; Domínguez, Angela; Surveillance Network of Catalonia, Spain, the Measles Elimination Program

2014-01-01

Healthcare personnel (HCP) play an important role in transmission of highly contagious diseases such as measles. Current immunization guidelines in Catalonia include Measles-Mumps-Rubella (MMR) immunization for HCP born after 1967 without evidence of immunity. Despite high vaccination coverage (90%) a high burden of measles cases related to outbreaks have occurred. The aim of this study was to assess the implication of HCP in measles transmission related to healthcare setting. A review of surveillance case data from 2001 to 2013 gathered through the Measles Elimination Program in Catalonia was performed. Twenty six outbreaks involving 797 cases were reported, 52 (6.5%) were HCP aged 21–41 years, 72,5% (38) patient were care personnel (doctors and nurses) and 22,5% (14) other health care related personnel. Forty six 87%) were unvaccinated, 4(10%) had only one dose and 2 had two doses of MMR. In community outbreaks 30 clusters with HCP involved were observed, yet none were identified as index cases. Non-vaccinated HCPs against measles were all under 45 years of age. Vaccination is the only reliable protection against nosocomial spread of measles from HCPs. Assessing vaccination status of HCPs and implementing a 2 dose vaccination in those lacking evidence of immunity is needed in order to set to zero the risk of acquiring and spreading measles in healthcare (HC) settings. PMID:25483548

MD modeling of screw dislocation influence upon initiation and mechanism of BCC-HCP polymorphous transition in iron

NASA Astrophysics Data System (ADS)

Dremov, V. V.; Ionov, G. V.; Sapozhnikov, F. A.; Smirnov, N. A.; Karavaev, A. V.; Vorobyova, M. A.; Ryzhkov, M. V.

2015-09-01

The present work is devoted to classical molecular dynamics investigation into microscopic mechanisms of the bcc-hcp transition in iron. The interatomic potential of EAM type used in the calculations was tested for the capability to reproduce ab initio data on energy evolution along the bcc-hcp transformation path (Burgers deformation + shuffe) and then used in the large-scale MD simulations. The large-scale simulations included constant volume deformation along the Burgers path to study the origin and nature of the plasticity, hydrostatic volume compression of defect free samples above the bcc to hcp transition threshold to observe the formation of new phase embryos, and the volume compression of samples containing screw dislocations to study the effect of the dislocations on the probability of the new phase critical embryo formation. The volume compression demonstrated high level of metastability. The transition starts at pressure much higher than the equilibrium one. Dislocations strongly affect the probability of the critical embryo formation and significantly reduce the onset pressure of transition. The dislocations affect also the resulting structure of the samples upon the transition. The formation of layered structure is typical for the samples containing the dislocations. The results of the simulations were compared with the in-situ experimental data on the mechanism of the bcc-hcp transition in iron.

Clinical and economic impact of various strategies for varicella immunity screening and vaccination of health care personnel.

PubMed

Baracco, G J; Eisert, S; Saavedra, S; Hirsch, P; Marin, M; Ortega-Sanchez, I R

2015-10-01

Exposure to patients with varicella or herpes zoster causes considerable disruption to a health care facility's operations and has a significant health and economic impact. However, practices related to screening for immunity and immunization of health care personnel (HCP) for varicella vary widely. A decision tree model was built to evaluate the cost-effectiveness of 8 different strategies of screening and vaccinating HCP for varicella. The outcomes are presented as probability of acquiring varicella, economic impact of varicella per employee per year, and cost to prevent additional cases of varicella. Monte Carlo simulations and 1-way sensitivity analyses were performed to address the uncertainties inherent to the model. Alternative epidemiologic and technologic scenarios were also analyzed. Performing a clinical screening followed by serologic testing of HCP with negative history diminished the cost impact of varicella by >99% compared with not having a program. Vaccinating HCP with negative screen cost approximately $50,000 per case of varicella prevented at the current level of U.S. population immunity, but was projected to be cost-saving at 92% or lower immunity prevalence. Improving vaccine acceptance rates and using highly sensitive assays also optimize cost-effectiveness. Strategies relying on screening and vaccinating HCP for varicella on employment were shown to be cost-effective for health care facilities and are consistent with current national guidelines for varicella prevention. Published by Elsevier Inc.

To Share or Not to Share: Malaysian Healthcare Professionals' Views on Localized Prostate Cancer Treatment Decision Making Roles.

PubMed

Lee, Yew Kong; Lee, Ping Yein; Cheong, Ai Theng; Ng, Chirk Jenn; Abdullah, Khatijah Lim; Ong, Teng Aik; Razack, Azad Hassan Abdul

2015-01-01

To explore the views of Malaysian healthcare professionals (HCPs) on stakeholders' decision making roles in localized prostate cancer (PCa) treatment. Qualitative interviews and focus groups were conducted with HCPs treating PCa. Data was analysed using a thematic approach. Four in-depth interviews and three focus group discussions were conducted between December 2012 and March 2013 using a topic guide. Interviews were audio-recorded, transcribed verbatim, and analysed thematically. The participants comprised private urologists (n = 4), government urologists (n = 6), urology trainees (n = 6), government policy maker (n = 1) and oncologists (n = 3). HCP perceptions of the roles of the three parties involved (HCPs, patients, family) included: HCP as the main decision maker, HCP as a guide to patients' decision making, HCP as a facilitator to family involvement, patients as main decision maker and patient prefers HCP to decide. HCPs preferred to share the decision with patients due to equipoise between prostate treatment options. Family culture was important as family members often decided on the patient's treatment due to Malaysia's close-knit family culture. A range of decision making roles were reported by HCPs. It is thus important that stakeholder roles are clarified during PCa treatment decisions. HCPs need to cultivate an awareness of sociocultural norms and family dynamics when supporting non-Western patients in making decisions about PCa.

To Share or Not to Share: Malaysian Healthcare Professionals' Views on Localized Prostate Cancer Treatment Decision Making Roles

PubMed Central

Lee, Yew Kong; Lee, Ping Yein; Cheong, Ai Theng; Ng, Chirk Jenn; Abdullah, Khatijah Lim; Ong, Teng Aik; Razack, Azad Hassan Abdul

2015-01-01

Aim To explore the views of Malaysian healthcare professionals (HCPs) on stakeholders’ decision making roles in localized prostate cancer (PCa) treatment. Methods Qualitative interviews and focus groups were conducted with HCPs treating PCa. Data was analysed using a thematic approach. Four in-depth interviews and three focus group discussions were conducted between December 2012 and March 2013 using a topic guide. Interviews were audio-recorded, transcribed verbatim, and analysed thematically. Findings The participants comprised private urologists (n = 4), government urologists (n = 6), urology trainees (n = 6), government policy maker (n = 1) and oncologists (n = 3). HCP perceptions of the roles of the three parties involved (HCPs, patients, family) included: HCP as the main decision maker, HCP as a guide to patients’ decision making, HCP as a facilitator to family involvement, patients as main decision maker and patient prefers HCP to decide. HCPs preferred to share the decision with patients due to equipoise between prostate treatment options. Family culture was important as family members often decided on the patient’s treatment due to Malaysia’s close-knit family culture. Conclusions A range of decision making roles were reported by HCPs. It is thus important that stakeholder roles are clarified during PCa treatment decisions. HCPs need to cultivate an awareness of sociocultural norms and family dynamics when supporting non-Western patients in making decisions about PCa. PMID:26559947

Effect of desliming of sulphide-rich mill tailings on the long-term strength of cemented paste backfill.

PubMed

Ercikdi, Bayram; Baki, Hakan; İzki, Muhammet

2013-01-30

This paper presents the effect of desliming on the short- and long-term strength, stability and rheological properties of cemented paste backfill (CPB) produced from two different mill tailings. A 28-day unconfined compressive strength (UCS) of ≥1.0 MPa and the maintenance of stability over 224 days of curing were selected as the design criteria for the evaluation of paste backfill performance. Desliming induced some changes in the physical, chemical, mineralogical and rheological properties of the tailings. CPB mixture of the deslimed tailings achieved the required consistency at a lower water to cement ratio. The short-term UCSs of CPB samples of the deslimed tailings were found to be 30-100% higher than those samples of the reference tailings at all the binder dosages and curing times. CPB samples of the deslimed tailings achieved the long-term stability at relatively low binder dosages (e.g. 5 wt% c.f. ≥6.1% for the reference tailings). It was also estimated that desliming could allow a 13.4-23.1% reduction in the binder consumption depending apparently on the inherent characteristics of the tailings. Over the curing period, generation of sulphate and acid by the oxidation of pyrite present in the tailings was also monitored to correlate with the strength losses observed in the long term. Scanning electron microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses provided an insight into the microstructure of CPB and the formation of secondary mineral phases (i.e. gypsum) confirming the beneficial effect of desliming. These findings suggest that desliming can be suitably exploited for CPB of sulphide-rich mill tailings to improve the strength and stability particularly in the long term and to reduce binder consumption. Copyright © 2012 Elsevier Ltd. All rights reserved.

Nano-modified cement composites and its applicability as concrete repair material

NASA Astrophysics Data System (ADS)

Manzur, Tanvir

Nanotechnology or Nano-science, considered the forth industrial revolution, has received considerable attention in the past decade. The physical properties of a nano-scaled material are entirely different than that of bulk materials. With the emerging nanotechnology, one can build material block atom by atom. Therefore, through nanotechnology it is possible to enhance and control the physical properties of materials to a great extent. Composites such as concrete materials have very high strength and Young's modulus but relatively low toughness and ductility due to their covalent bonding between atoms and lacking of slip systems in the crystal structures. However, the strength and life of concrete structures are determined by the microstructure and mass transfer at nano scale. Cementitious composites are amenable to manipulation through nanotechnology due to the physical behavior and size of hydration products. Carbon nanotubes (CNT) are nearly ideal reinforcing agent due to extremely high aspect ratios and ultra high strengths. So there is a great potential to utilize CNT in producing new cement based composite materials. It is evident from the review of past literature that mechanical properties of nanotubes reinforced cementitious composites have been highly variable. Some researches yielded improvement in performance of CNT-cement composites as compared to plain cement samples, while other resulted in inconsequential changes in mechanical properties. Even in some cases considerable less strengths and modulus were obtained. Another major difficulty of producing CNT reinforced cementitious composites is the attainment of homogeneous dispersion of nanotubes into cement but no standard procedures to mix CNT within the cement is available. CNT attract more water to adhere to their surface due to their high aspect ratio which eventually results in less workability of the cement mix. Therefore, it is extremely important to develop a suitable mixing technique and an optimum mix proportion to produce CNT reinforced cement composites. In this study, an extensive parametric study has been conducted using different types of treated and untreated multi walled nanotubes (MWNT) as reinforcement of cementitious composites having different mix proportions. It is found that mixing of nanotubes within cement matrix is the key to develop composites having desirable properties. A mixing technique has been proposed to address the issues related to dispersion of nanotubes within cement matrix. Polycarboxylate based super plasticizer has been proposed to use as surfactant. It is evident that there exists an optimum concentration of MWNT and mix proportion to achieve proper reinforcement behavior and strength properties. The affect of size of MWNT on strengths (both compressive and flexure) of composites has also been investigated. Based on the parametric study and statistical analysis, a tentative optimum mix proportion has been proposed. Composites made by the proposed mixing technique and design mix obtained 26, 27 and 16% higher compressive strength as compared to control samples at the age of 3, 7 and 28 day, respectively. Flexural strengths of those composites at 3, 7 and 28 day were about 24, 24.5 and 20% higher than that of control samples, respectively. It has also been suggested that application of MWNT reinforced cement mortar as concrete repair material has excellent potential since composites exhibited desirable behavior in setting time, bleeding and slant shear.

Study of Transport Properties and Structure of Extended-Chain Polymers.

DTIC Science & Technology

1985-09-01

Thermometric devices disturb temperature. Unfeasible to use guarded electrodes or hotplates ". Surface and volume conductivities mixed. Numerical examples will...gold or aluminum onto appropriate portions of the surface. Alternatively, graphite pastes, silver pastes, conductive cements, or paints can be used. Care... aluminum box which was grounded to provide elec- 158 85 a) TOP VIEW GROUND WIRETELNBS ONNECTORLO samAewi E SHILDE ELIREDE ALUM5 INV O kv~~TO COVERBA7:E

78 FR 15737 - Incidental Take Permit Amendment and Supplemental Environmental Assessment for Wind Energy...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-12

...] Incidental Take Permit Amendment and Supplemental Environmental Assessment for Wind Energy Development... of a revised habitat conservation plan (revised HCP) and accompanying documents for wind energy development by San Francisco Wind Farm LLC (formerly WindMar R.E.) (Permittee). The revised HCP analyzes take...

Impact of hydrated cement paste quality and entrained air-void system on the durability of concrete.

DOT National Transportation Integrated Search

2011-06-30

This study is designed to examine whether traditional limits used to describe the air-void system still : apply to concrete prepared with new admixtures and materials. For this research, the concrete mixtures : prepared were characterized with tradit...

A Systematic Review of Root Canal Filling Materials for Deciduous Teeth: Is There an Alternative for Zinc Oxide-Eugenol?

PubMed Central

Barja-Fidalgo, Fernanda; Moutinho-Ribeiro, Michele; Oliveira, Maria Angelina Amorim; de Oliveira, Branca Heloísa

2011-01-01

The aim of this systematic review was to determine whether there is a root canal filling for deciduous teeth equally or more effective than zinc oxide-eugenol cement (ZOE). Six clinical trials selected for inclusion were independently reviewed by two researchers. Only two showed statistically significant different success rates between the test and the control groups. One found that an iodoform paste with calcium hydroxide (IP + Ca) performed better than ZOE, and the other found that ZOE performed similarly to IP + Ca. The other four studies compared ZOE with an iodoform paste (IP), a calcium hydroxide cement (Ca(OH)2), or IP + Ca. In these trials, the success rates in the ZOE groups were slightly lower than in the other groups. There seems to be no convincing evidence to support the superiority of any material over ZOE, and both ZOE and IP + Ca appear to be suitable as root canal fillings for deciduous teeth. PMID:21991471

On Deterioration Mechanism of Concrete Exposed to Freeze-Thaw Cycles

NASA Astrophysics Data System (ADS)

Trofimov, B. Ya; Kramar, L. Ya; Schuldyakov, K. V.

2017-11-01

At present, concrete and reinforced concrete are gaining ground in all sectors of construction including construction in the extreme north, on shelves, etc. Under harsh service conditions, the durability of reinforced concrete structures is related to concrete frost resistance. Frost resistance tests are accompanied by the accumulation of residual dilation deformations affected by temperature-humidity stresses, ice formation and other factors. Porosity is an integral part of the concrete structure which is formed as a result of cement hydration. The prevailing hypothesis of a deterioration mechanism of concrete exposed to cyclic freezing, i.e. the hypothesis of hydraulic pressure of unfrozen water in microcapillaries, does not take into account a number of phenomena that affect concrete resistance to frost aggression. The main structural element of concrete, i.e. hardened cement paste, contains various hydration products, such as crystalline, semicrystalline and gel-like products, pores and non-hydrated residues of clinker nodules. These structural elements in service can gain thermodynamic stability which leads to the concrete structure coarsening, decrease in the relaxation capacity of concrete when exposed to cycling. Additional destructive factors are leaching of portlandite, the difference in thermal dilation coefficients of hydration products, non-hydrated relicts, aggregates and ice. The main way to increase concrete frost resistance is to reduce the macrocapillary porosity of hardened cement paste and to form stable gel-like hydration products.

Use of cemented paste backfill in arsenic-rich tailings

NASA Astrophysics Data System (ADS)

Hamberg, Roger; Maurice, Christian; Alakangas, Lena

2015-04-01

Gold is extracted by cyanide leaching from inclusions in arsenopyrite from a mine in the north of Sweden. The major ore mineral assemblage consists of pyrrhotite and arsenopyrite-loellingite. Effluents from the gold extraction were treated with Fe2(SO4)3, with the aim to form stable As-bearing Fe-precipitates (FEP). The use of the method called cemented paste backfill (CPB) is sometimes suggested for the management of tailings. In CPB, tailings are commonly mixed with low proportions (3 - 7 %) of cement and backfilled into underground excavated area. To reduce costs, amendments such as granulated blast furnace slag (GBFS), biofuel fly ash (BFA) and cement kiln dust (CKD) are used for partial replacement of cement in CPB due to their pozzolanic and alkaline properties. The objective for this study was to evaluate the leaching behaviour of As in CPB-mixtures with low proportions (1 - 3 %) of BFA and ordinary cement and unmodified tailings. The selection of CPB-recipies was made based on technical and economical criterias to adress the demands deriving from the mining operations. Speciation of the As in ore and tailings samples revealed that mining processes have dissolved the majority of the arsenopyrite in the ore, causing secondary As phases to co-precipitate with newly formed FEP:s. Tank leaching tests (TLT) and weathering cells (WCT) were used to compare leaching behaviour in a monolithic mass contra a crushed material. Quantification of the presumed benefit of CPB was made by calculation of the cumulative leaching of As. Results from the leaching tests (TLT and WCT) showed that the inclusion of As-rich tailings into a cementitious matrix increased leaching of As. This behaviour could partially be explained by an increase of pH. The addition of alkaline binder materials to tailings increased As leaching due to the relocation of desorbed As from FEPs into less acid-tolerant species such as Ca-arsenates and cementitious As-phases. Unmodified tailings generated an acidic environment in which As-bearing FEPs were stable. The addition of binders increased the tailings' acid-neutralizing capacity and introduced more Ca-ions and Fe-precipitates into the tailings matrix, both of which may facilitate As adsorption and reduce the potential for sulphide oxidation on a long-term basis.

[Chromatic study of all-ceramic crown--IPS Empress: difference of color by manufacturing technique and cements].

PubMed

Hata, Utako; Sadamitsu, Kenichiro; Yamamura, Osamu; Kawauchi, Daisuke; Fujii, Teruhisa

2004-12-01

In recent years,aesthetic appearance and function are called for and all-ceramic crowns are spreading. By choosing an all-ceramic crown the problem of metal ceramics is avoided. There are difficulties of color tone reproducibility of cervical margin and darkness of gingival margin. We examined IPS Empress also in various all-ceramic crowns. IPS Empress has high permeability a ceramic ingot of various color tones and excellent color tone reproducibility of natural teeth. Generally a layering technique is used for an anterior tooth and the staining technique is used for a molar. However the details are unknown We examined how differences of manufacturing method and cement affect the color tone of all ceramics clinically. Two kinds of Empress crown were fabricated for a 27 year-old woman's upper left-side central incisors:the staining technique of IPS Empress and the layering technique of IPS Empress II. Various try-in pastes(transparent opaque white white and yellow) of VariolinkII of the IPS Empress System were used for cementing. Color was measured using a spectrophotometer CMS 35FS. The L*a*b* color system was used for showing a color. The right-side central incisors on the opposite side of the same name teeth were used for comparison. We analyzed the color difference (DeltaE* ab)with a natural tooth. Consequently when it had no cement of staining technique and was tranceparent small values were obtained. It is considered that the color tone can be adjusted by color cement. It is effective to use the staining technique for an anterior tooth crown depending on the case. The crown manufactured using the layering technique is not easily influenced by cement. The crown manufactured by the staining technique tends to be influenced by cement.

On the Nature of Disorder in Solid 4He

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2010-02-01

We apply a modified Debye approach to calculate the Gibbs free energy for different structural phases and crystallite sizes in 4He. Atoms are assumed to interact via the Aziz potential. We have found that some intermediate (between hcp and bcc) phase predicted previously is more favorable than hcp at low temperatures and for small sizes. We show that it can exist in a wide pressure range up to 60 bar in 4He for crystallite sizes about 3,000 atoms. For larger sizes (10,000 atoms or more) this phase becomes unfavorable. In multidomain structures the intermediate phase competes with hcp and metastable fcc that can be a reason for disorder in solid 4He.

Measurement of Body-Centered-Cubic Aluminum at 475 GPa [Observation of Body-Centered-Cubic Aluminum at 475 GPa

DOE PAGES

Polsin, D. N.; Fratanduono, D. E.; Rygg, J. R.; ...

2017-10-27

Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216 ± 9 GPa and 321 ± 12 GPa, respectively, with the bcc phase persisting to 475 GPa. Here, this is the first in situ observation of the high-pressure bcc phase of Al. High-pressure texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.

Measurement of Body-Centered-Cubic Aluminum at 475 GPa [Observation of Body-Centered-Cubic Aluminum at 475 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polsin, D. N.; Fratanduono, D. E.; Rygg, J. R.

Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216 ± 9 GPa and 321 ± 12 GPa, respectively, with the bcc phase persisting to 475 GPa. Here, this is the first in situ observation of the high-pressure bcc phase of Al. High-pressure texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.

Spin and charge transport across cobalt/graphene interfaces

NASA Astrophysics Data System (ADS)

Chshiev, Mairbek; Kalitsov, Alan; Mryasov, Oleg

We report ballistic calculations of in-plane and out-of-plane spin and charge transport through graphene attached to the hcp-Co electrodes. Our calculations are based on the Keldysh non-equilibrium Green Function formalism and the tight binding Hamiltonian model tailored to treat both lateral and vertical device configurations. We present results for (i) vertical device that consists of a one-side fluorinated C4F graphene sandwiched between two hcp Co electrodes and (ii) lateral device consisting of pristine graphene/C4F graphene bilayer with two top hcp-Co electrodes Our calculations predict large magnetoresistance with small resistance-area product and significant deviation from sinusoidal behavior of spin transfer torque for the vertical device configuration.

Role of Substrate on Quartz Cementation in Quartz Aggregates

NASA Astrophysics Data System (ADS)

Farver, J. R.; Winslow, D.; Onasch, C.

2010-12-01

Quartz cementation in quartz aggregates has been experimentally investigated. The starting material was disaggregated detrital quartz grains from the well-sorted, mature St. Peter Sandstone. The ‘as-is’ grains have patches of iron oxide coatings and some have euhedral overgrowths that contain iron oxide dust rims. In addition a set of experiments was run using grains that were cleaned by soaking in sodium hydrosulfite and sodium bisulfate solutions to remove exposed iron oxide coatings. Experimental charges consisted of amorphous silica powder (≈30 mg) to provide a source of silica for the quartz cement, AlCl3 powder (≈3 mg) to provide a tracer for Cathodoluminescence (CL) identification of cement formed during the experiment, 25 wt% NaCl brine solution (≈25 mg) to increase the silica solubility and to better mimic oil field brines, and the natural quartz grains (100-130 mg). The charges were weld-sealed in Au capsules and run in cold-seal pressure vessels at 250°C to 450°C at 150 MPa confining pressure for up to 8 weeks. After the experiments, the samples were vacuum impregnated with a low viscosity epoxy containing a blue dye. After curing, the sample charge was sawn in half along its long axis and one half was polished (to 1 micron diamond paste) for analysis. The nature and amount of quartz cement in the samples were determined by a combination of CL, light microscopy, and scanning electron microscopy. Photomosaics of the samples were created and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement formed during the experiment was easily recognized from the quartz grains (and previous overgrowths) by the difference in luminescence. The results indicate the amorphous silica powder provides a ready source for silica for quartz cementation due to its greater solubility than the quartz. The cementation rates are rapid (>14% cement formed in 2 weeks at 450°C and >7% in 8 weeks at 250°C). Compared to experiments using crushed fragments of synthetic quartz (Pepple, 2007), the amount of cement in these natural samples was greater. Cementation followed a common pattern in all samples. Microfractures, which formed during pressurization of the charges, healed very rapidly followed by overgrowths on the quartz grains. Cementation began closest to the amorphous silica, then progressed away. There was no measurable difference in the amount of quartz cement formed in samples of the as-is and cleaned St. Peter Sandstone indicating that iron played no role in the rate of cementation. Although the amount of cement formed increased with increasing temperature and duration of the experiments, the rate of cementation decreased dramatically in longer duration (8 weeks) experiments suggesting a change in the precipitation mechanism/rate. This apparent change in precipitation rate may reflect a decrease in available surfaces for nucleation and/or a decrease in growth rate as euhedral faces develop as proposed by Lander et al (2008).

77 FR 43609 - Endangered and Threatened Wildlife and Plants; Incidental Take Permit Application; Draft...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-25

... Environmental Assessment and Draft San Luis Valley Regional Habitat Conservation Plan, Colorado AGENCY: Fish and... implementation of a regional habitat conservation plan (HCP) in the San Luis Valley, Colorado. Pursuant to the ESA and the National Environmental Policy Act, we announce the availability of the draft HCP and draft...

Stabilizing the hexagonal close packed structure of hard spheres with polymers: Phase diagram, structure, and dynamics

NASA Astrophysics Data System (ADS)

Edison, John R.; Dasgupta, Tonnishtha; Dijkstra, Marjolein

2016-08-01

We study the phase behaviour of a binary mixture of colloidal hard spheres and freely jointed chains of beads using Monte Carlo simulations. Recently Panagiotopoulos and co-workers predicted [Nat. Commun. 5, 4472 (2014)] that the hexagonal close packed (HCP) structure of hard spheres can be stabilized in such a mixture due to the interplay between polymer and the void structure in the crystal phase. Their predictions were based on estimates of the free-energy penalty for adding a single hard polymer chain in the HCP and the competing face centered cubic (FCC) phase. Here we calculate the phase diagram using free-energy calculations of the full binary mixture and find a broad fluid-solid coexistence region and a metastable gas-liquid coexistence region. For the colloid-monomer size ratio considered in this work, we find that the HCP phase is only stable in a small window at relatively high polymer reservoir packing fractions, where the coexisting HCP phase is nearly close packed. Additionally we investigate the structure and dynamic behaviour of these mixtures.

Exploration of momentum evolution and three-dimensional localization in recombined electron wave packets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeibel, J. G.; Jones, R. R.

2003-08-01

Picosecond ''half-cycle'' pulses (HCPs) have been used to produce electronic wave packets by recombining photoelectrons with their parent ions. The time-dependent momentum distributions of the bound wave packets are probed using a second HCP and the impulsive momentum retrieval (IMR) method. For a given delay between the initial photoionization event and the HCP recombination, classical trajectory simulations predict pronounced periodic wave packet motion for a restricted range of recombining HCP amplitudes. This motion is characterized by the repeated formation and collapse of a highly localized spike in the three-dimensional electron probability density at a large distance from the nucleus. Ourmore » experiments confirm that oscillatory wave packet motion occurs only for certain recombination ''kick'' strengths. Moreover, the measured time-dependent momentum distributions are consistent with the predicted formation of a highly localized electron packet. We demonstrate a variation of the IMR in which amplitude modulation of the HCP probe field is employed to suppress noise and allow for a more direct recovery of electron momentum from experimental ionization data.« less

Compression of Fe-Si-H alloys to core pressures

NASA Astrophysics Data System (ADS)

Tagawa, Shoh; Ohta, Kenji; Hirose, Kei; Kato, Chie; Ohishi, Yasuo

2016-04-01

We examined the compression behavior of hexagonal-close-packed (hcp) (Fe0.88Si0.12)1H0.61 and (Fe0.88Si0.12)1H0.79 (in atomic ratio) alloys up to 138 GPa in a diamond anvil cell (DAC). While contradicting experimental results were previously reported on the compression curve of double-hcp (dhcp) FeHx (x ≈ 1), our data show that the compressibility of hcp Fe0.88Si0.12Hx alloys is very similar to those of hcp Fe and Fe0.88Si0.12, indicating that the incorporation of hydrogen into iron does not change its compression behavior remarkably. The present experiments suggest that the inner core may contain up to 0.47 wt % hydrogen (FeH0.26) if temperature is 5000 K. The calculated density profile of Fe0.88Si0.12H0.17 alloy containing 0.32 wt % hydrogen in addition to geochemically required 6.5 wt % silicon matches the seismological observations of the outer core, supporting that hydrogen is an important core light element.

Exploring and Promoting Prosocial Vaccination: A Cross-Cultural Experiment on Vaccination of Health Care Personnel

PubMed Central

Betsch, Cornelia; Korn, Lars; Holtmann, Cindy

2016-01-01

Influenza vaccination for health care personnel (HCP) is recommended particularly because it indirectly protects patients from contracting the disease. Vaccinating can therefore be interpreted as a prosocial act. However, HCP vaccination rates are often far too low to prevent nosocomial infections. Effective interventions are needed to increase HCP's influenza vaccine uptake. Here we devise a novel tool to experimentally test interventions that aim at increasing prosocially motivated vaccine uptake under controlled conditions. We conducted a large-scale and cross-cultural experiment with participants from countries with either a collectivistic (South Korea) or an individualistic (USA) cultural background. Results showed that prosocially motivated vaccination was more likely in South Korea compared to the US, mediated by a greater perception of vaccination as a social act. However, changing the default of vaccination, such that participants had to opt out rather than to opt in, increased vaccine uptake in the US and therefore compensated for the lower level of prosocial vaccination. In sum, the present study provides both a novel method to investigate HCP influenza vaccination behavior and interventions to increase their vaccine uptake. PMID:27725940

Exploring and Promoting Prosocial Vaccination: A Cross-Cultural Experiment on Vaccination of Health Care Personnel.

PubMed

Böhm, Robert; Betsch, Cornelia; Korn, Lars; Holtmann, Cindy

2016-01-01

Influenza vaccination for health care personnel (HCP) is recommended particularly because it indirectly protects patients from contracting the disease. Vaccinating can therefore be interpreted as a prosocial act. However, HCP vaccination rates are often far too low to prevent nosocomial infections. Effective interventions are needed to increase HCP's influenza vaccine uptake. Here we devise a novel tool to experimentally test interventions that aim at increasing prosocially motivated vaccine uptake under controlled conditions. We conducted a large-scale and cross-cultural experiment with participants from countries with either a collectivistic (South Korea) or an individualistic (USA) cultural background. Results showed that prosocially motivated vaccination was more likely in South Korea compared to the US, mediated by a greater perception of vaccination as a social act. However, changing the default of vaccination, such that participants had to opt out rather than to opt in, increased vaccine uptake in the US and therefore compensated for the lower level of prosocial vaccination. In sum, the present study provides both a novel method to investigate HCP influenza vaccination behavior and interventions to increase their vaccine uptake.

Examination of Cement Pastes Hydrated Phases, and Synthetic Products by X-Ray Diffraction

DTIC Science & Technology

1972-04-01

International Union o, Crystallography Commission on Crystallo- graphic Data, Powder Data, Journal of Applied Crystallography, Vol 4, pp 81-86, 1971 . 21...Papes, Research Series 1, Building Research Station, 1962. 25. l,, Dosch, Rbntgen-Ceinstrukturuntersuchu , luftemp’indlicher pulverprlparate, Zement- Kall

FCC-HCP coexistence in dense thermo-responsive microgel crystals

NASA Astrophysics Data System (ADS)

Karthickeyan, D.; Joshi, R. G.; Tata, B. V. R.

2017-06-01

Analogous to hard-sphere suspensions, monodisperse thermo-responsive poly (N-isopropyl acrylamide) (PNIPAM) microgel particles beyond a volume fraction (ϕ) of 0.5 freeze into face centered cubic (FCC)-hexagonal close packed (HCP) coexistence under as prepared conditions and into an FCC structure upon annealing. We report here FCC-HCP coexistence to be stable in dense PNIPAM microgel crystals (ϕ > 0.74) with particles in their deswollen state (referred to as osmotically compressed microgel crystals) and the FCC structure with particles in their swollen state by performing annealing studies with different cooling rates. The structure of PNIPAM microgel crystals is characterized using static light scattering technique and UV-Visible spectroscopy and dynamics by dynamic light scattering (DLS). DLS studies reveal that the particle motion is diffusive at short times in crystals with ϕ < 0.74 and sub-diffusive at short times in PNIPAM crystals with ϕ > 0.74. The observed sub-diffusive behavior at short times is due to the overlap (interpenetration) of the dangling polymer chains between the shells of neighbouring PNIPAM microgel particles. Overlap is found to disappear upon heating the crystals well above their melting temperature, Tm due to reduction in the particle size. Annealing studies confirm that the overlap of dangling polymer chains between the shells of neighbouring PNIPAM spheres is responsible for the stability of FCC-HCP coexistence observed in osmotically compressed PNIPAM microgel crystals. Results are discussed in the light of recent reports of stabilizing the HCP structure in hard sphere crystals by adding interacting polymer chains.

Prevalence of and factors associated with burnout among health care professionals in Arab countries: a systematic review.

PubMed

Elbarazi, I; Loney, T; Yousef, S; Elias, A

2017-07-17

Burnout among healthcare professionals is one of the key challenges affecting health care practice and quality of care. This systematic review aims to (1) estimate the prevalence of burnout among health care professionals (HCP) in Arab countries; and (2) explore individual and work-related factors associated with burnout in this population. Multiple electronic databases were searched for studies published in English or Arabic from January 1980 to November 2014 assessing burnout (using the Maslach Burnout Inventory; MBI) amongst health care professionals (HCP) in Arab countries. Nineteen studies (N = 4108; 49.3% females) conducted on HCP in Bahrain, Egypt, Jordan, Lebanon, Palestine, Saudi Arabia and Yemen were included in this review. There was a wide range of prevalence estimates for the three MBI subscales, high Emotional Exhaustion (20.0-81.0%), high Depersonalization (9.2-80.0%), and low Personal Accomplishment (13.3-85.8%). Gender, nationality, service duration, working hours, and shift patterns were all significantly associated with burnout. Within the constraints of the study and the range of quality papers available, our review revealed moderate-to-high estimates of self-reported burnout among HCP in Arab countries that are similar to prevalence estimates in non-Arabic speaking westernized developed countries. In order to develop culturally appropriate interventions, further research using longitudinal designs is needed to confirm the risk factors for burnout in specific HCP settings and specialties in Arab countries.

Comparison of informal caregiver and named nurse assessment of symptoms in elderly patients dying in hospital using the palliative outcome scale.

PubMed

Dawber, Rebecca; Armour, Kathy; Ferry, Peter; Mukherjee, Bhaskar; Carter, Christopher; Meystre, Chantal

2016-01-12

A prospective study of symptom assessments made by a healthcare professional (HCP; named nurse) and an informal caregiver (ICG) compared with that of the patient with a terminal diagnosis. To look at the validity of HCP and ICG as proxies, which symptoms they can reliably assess, and to determine who is the better proxy between HCP and ICG. A total of 50 triads of patient (>65 years) in the terminal phase, ICG and named nurse on medical wards of an acute general hospital. Assessments were made using the patient and caregiver versions of the palliative outcome scale (POS), all taken within a 24 h period. Agreement between patient-rated, ICG-rated and HCP-rated POS and POS for symptoms (POS-S) was measured using weighted-κ statistics. Demographic and clinical data on each group of participants were collected. ICG assessments have higher agreement with those of the patient than HCP. Better agreement in both groups was found for physical symptoms, and best agreement was for pain. The worst agreements were for psychological symptoms, such as anxiety and depression, and for satisfaction with information given. Psychological symptoms are overestimated by both ICG and HCP. ICGs are more reliable proxies than HCPs. A trend for overestimation of symptoms was found in both groups which may lead to undervaluation of the quality of life by proxy and overtreatment of symptoms. This highlights the need to always use the patient report when possible, and to be aware of the potential flaws in proxy assessment. Reasons for overestimation by proxies deserve further research. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Strain sensitivity of carbon nanotube cement-based composites for structural health monitoring

NASA Astrophysics Data System (ADS)

D'Alessandro, Antonella; Ubertini, Filippo; Laflamme, Simon; Rallini, Marco; Materazzi, Annibale L.; Kenny, Josè M.

2016-04-01

Cement-based smart sensors appear particularly suitable for monitoring applications, due to their self-sensing abilities, their ease of use, and their numerous possible field applications. The addition of conductive carbon nanofillers into a cementitious matrix provides the material with piezoresistive characteristics and enhanced sensitivity to mechanical alterations. The strain-sensing ability is achieved by correlating the variation of external loads or deformations with the variation of specific electrical parameters, such as the electrical resistance. Among conductive nanofillers, carbon nanotubes (CNTs) have shown promise for the fabrication of self-monitoring composites. However, some issues related to the filler dispersion and the mix design of cementitious nanoadded materials need to be further investigated. For instance, a small difference in the added quantity of a specific nanofiller in a cement-matrix composite can substantially change the quality of the dispersion and the strain sensitivity of the resulting material. The present research focuses on the strain sensitivity of concrete, mortar and cement paste sensors fabricated with different amounts of carbon nanotube inclusions. The aim of the work is to investigate the quality of dispersion of the CNTs in the aqueous solutions, the physical properties of the fresh mixtures, the electromechanical properties of the hardened materials, and the sensing properties of the obtained transducers. Results show that cement-based sensors with CNT inclusions, if properly implemented, can be favorably applied to structural health monitoring.

Preparation and characterization of a hybrid alkaline binder based on a fly ash with no commercial value

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mejia, Johanna M.; Rodriguez, Erich; Mejia de Gutierrez, Ruby

2015-05-18

Alkali-activated Portland fly ash cement (FA/OPC) and alkali activated blast furnace slag-fly ash cement (FA/GBFS) were prepared using 70% of a low quality fly ash (FA). The low quality is associated with a high content of unburned material (loss of ignition of 14.6%). The hybrid cements were activated by the alkaline solution in order to obtain an overall SiO 2/Al 2O 3 molar ratio of 5.0 and 6.0 and unique overall Na 2O/SiO 2 molar ratio of 0.21. The microstructural characterization of the blended pastes generated in the systems showed the coexistence of amorphous gels C-A-S-H and N-A-S-H gels inmore » the hybrid systems. The addition of OPC or GBFS increases the compressive strength (at 28 days of curing) up to 127% compared with the geopolymer systems based only on FA used in this study. The content of silicates soluble also plays an important role in the reaction products and higher SiO 2/Al 2O 3 lead to obtain higher mechanical performance and denser structure. The results obtained show that these hybrid cements are an effective way for valorization the waste used in this study for the production of high strength and low-carbon footprint cement-type material.« less

Effect of PCM on the Hydration Process of Cement-Based Mixtures: A Novel Thermo-Mechanical Investigation.

PubMed

Fabiani, Claudia; Pisello, Anna Laura; D'Alessandro, Antonella; Ubertini, Filippo; Cabeza, Luisa F; Cotana, Franco

2018-05-23

The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to their melting temperature and operation boundaries. Further to that, the present paper aims at investigating an innovative use of PCM for absorbing heat released by cement during its curing process, which typically contributes to micro-cracking of massive concrete elements, therefore compromising their mechanical performance during their service life. The experiments carried out in this work showed how PCM, even in small quantities (i.e., up to 1% in weight of cement) plays a non-negligible benefit in reducing differential thermal increases between core and surface and therefore mechanical stresses originating from differential thermal expansion, as demonstrated by thermal monitoring of cement-based cubes. Both PCM types analyzed in the study (with melting temperatures at 18 and 25 ∘ C) were properly dispersed in the mix and were shown to be able to reduce the internal temperature of the cement paste by several degrees, i.e., around 5 ∘ C. Additionally, such small amount of PCM produced a reduction of the final density of the composite and an increase of the characteristic compressive strength with respect to the plain recipe.

Axial compression behaviour of reinforced wallettes fabricated using wood-wool cement panel

NASA Astrophysics Data System (ADS)

Noh, M. S. Md; Kamarudin, A. F.; Mokhatar, S. N.; Jaudin, A. R.; Ahmad, Z.; Ibrahim, A.; Muhamad, A. A.

2018-04-01

Wood-wool cement composite panel (WWCP) is one of wood based composite material that produced in a stable panel form and suitable to be used as building wall system to replace non-ecofriendly material such as brick and other masonry element. Heavy construction material such as brick requires more manpower and consume a lot of time to build the wall panel. WWCP is a lightweight material with a density range from 300 kg/m3 to 500 kg/m3 and also capable to support an imposed load from the building. This study reported on the axial compression behaviour of prefabricated reinforced wallettes constructed with wood-wool cement panel. A total of six specimens were fabricated using two layers of cross laminated WWCP bonded with normal mortar paste (Portland cement) at a mix ratio of 1:3 (cement : sand). As part of lifting mechanism, the wallettes were equipped with three steel reinforcement (T12) that embedded inside the core of wallettes. Three replicates of wallettes specimens with dimension 600 mm width and 600 mm length were fabricated without surface plaster and with 16 mm thickness of surface plaster. The wallettes were tested under axial compression load after 28 days of fabrication until failure. The result indicated that, the application of surface plaster significantly increases the loading capacity about 35 % and different orientation of the panels improve the bonding strength of the wall.

A probabilistic atlas of human brainstem pathways based on connectome imaging data.

PubMed

Tang, Yuchun; Sun, Wei; Toga, Arthur W; Ringman, John M; Shi, Yonggang

2018-04-01

The brainstem is a critical structure that regulates vital autonomic functions, houses the cranial nerves and their nuclei, relays motor and sensory information between the brain and spinal cord, and modulates cognition, mood, and emotions. As a primary relay center, the fiber pathways of the brainstem include efferent and afferent connections among the cerebral cortex, spinal cord, and cerebellum. While diffusion MRI has been successfully applied to map various brain pathways, its application for the in vivo imaging of the brainstem pathways has been limited due to inadequate resolution and large susceptibility-induced distortion artifacts. With the release of high-resolution data from the Human Connectome Project (HCP), there is increasing interest in mapping human brainstem pathways. Previous works relying on HCP data to study brainstem pathways, however, did not consider the prevalence (>80%) of large distortions in the brainstem even after the application of correction procedures from the HCP-Pipeline. They were also limited in the lack of adequate consideration of subject variability in either fiber pathways or region of interests (ROIs) used for bundle reconstruction. To overcome these limitations, we develop in this work a probabilistic atlas of 23 major brainstem bundles using high-quality HCP data passing rigorous quality control. For the large-scale data from the 500-Subject release of HCP, we conducted extensive quality controls to exclude subjects with severe distortions in the brainstem area. After that, we developed a systematic protocol to manually delineate 1300 ROIs on 20 HCP subjects (10 males; 10 females) for the reconstruction of fiber bundles using tractography techniques. Finally, we leveraged our novel connectome modeling techniques including high order fiber orientation distribution (FOD) reconstruction from multi-shell diffusion imaging and topography-preserving tract filtering algorithms to successfully reconstruct the 23 fiber bundles for each subject, which were then used to calculate the probabilistic atlases in the MNI152 space for public release. In our experimental results, we demonstrate that our method yielded anatomically faithful reconstruction of the brainstem pathways and achieved improved performance in comparison with an existing atlas of cerebellar peduncles based on HCP data. These atlases have been publicly released on NITRIC (https://www.nitrc.org/projects/brainstem_atlas/) and can be readily used by brain imaging researchers interested in studying brainstem pathways. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of the pharmacokinetics and tolerability of HCP1004 (a fixed-dose combination of naproxen and esomeprazole strontium) and VIMOVO® (a marketed fixed-dose combination of naproxen and esomeprazole magnesium) in healthy volunteers

PubMed Central

Choi, YoonJung; Han, HyeKyung; Shin, Dongseong; Lim, Kyoung Soo; Yu, Kyung-Sang

2015-01-01

Background HCP1004 is a newly developed fixed-dose combination of naproxen (500 mg) and esomeprazole strontium (20 mg) that is used in the treatment of rheumatic diseases and can reduce the risk of nonsteroidal anti-inflammatory drug-associated ulcers. The aim of this study was to evaluate the pharmacokinetics (PK) and safety of HCP1004 compared to VIMOVO® (a marketed fixed-dose combination of naproxen and esomeprazole magnesium). Subjects and methods An open-label, randomized, two-treatment, two-sequence crossover, single-dose clinical study was conducted in 70 healthy volunteers. In each period, a reference (VIMOVO®) or test (HCP1004) drug was administered orally, and serial blood samples for PK analysis were collected up to 72 hours after dosing. To evaluate the PK profiles, the maximum plasma concentration (Cmax) and the area under the concentration–time curve from 0 to the last measurable time (AUC0−t) were estimated using a noncompartmental method. Safety profiles were evaluated throughout the study. Results Sixty-six of the 70 subjects completed the study. The Cmax (mean ± standard deviation) and AUC0−t (mean ± standard deviation) for naproxen in HCP1004 were 61.67±15.16 µg/mL and 1,206.52±166.46 h·µg/mL, respectively; in VIMOVO®; these values were 61.85±14.54 µg/mL and 1,211.44±170.01 h·µg/mL, respectively. The Cmax and AUC0−t for esomeprazole in HCP1004 were 658.21±510.91 ng/mL and 1,109.11±1,111.59 h·ng/mL, respectively; for VIMOVO®, these values were 595.09±364.23 ng/mL and 1,015.12±952.98 h·ng/mL, respectively. The geometric mean ratios and 90% confidence intervals (CIs) (HCP1004 to VIMOVO®) of the Cmax and AUC0−t of naproxen were 0.99 (0.94–1.06) and 1.00 (0.98–1.01), respectively. For esomeprazole, the geometric mean ratios (90% CI) for the Cmax and AUC0−t were 0.99 (0.82–1.18) and 1.04 (0.91–1.18), respectively. The overall results of the safety assessment showed no clinically significant issues for either treatment. Conclusion The PK of HCP1004 500/20 mg was comparable to that of VIMOVO® 500/20 mg for both naproxen and esomeprazole after a single oral dose. Both drugs were well-tolerated without any safety issues. PMID:26257511

Comparison of the pharmacokinetics and tolerability of HCP1004 (a fixed-dose combination of naproxen and esomeprazole strontium) and VIMOVO® (a marketed fixed-dose combination of naproxen and esomeprazole magnesium) in healthy volunteers.

PubMed

Choi, YoonJung; Han, HyeKyung; Shin, Dongseong; Lim, Kyoung Soo; Yu, Kyung-Sang

2015-01-01

HCP1004 is a newly developed fixed-dose combination of naproxen (500 mg) and esomeprazole strontium (20 mg) that is used in the treatment of rheumatic diseases and can reduce the risk of nonsteroidal anti-inflammatory drug-associated ulcers. The aim of this study was to evaluate the pharmacokinetics (PK) and safety of HCP1004 compared to VIMOVO(®) (a marketed fixed-dose combination of naproxen and esomeprazole magnesium). An open-label, randomized, two-treatment, two-sequence crossover, single-dose clinical study was conducted in 70 healthy volunteers. In each period, a reference (VIMOVO(®)) or test (HCP1004) drug was administered orally, and serial blood samples for PK analysis were collected up to 72 hours after dosing. To evaluate the PK profiles, the maximum plasma concentration (Cmax) and the area under the concentration-time curve from 0 to the last measurable time (AUC0-t) were estimated using a noncompartmental method. Safety profiles were evaluated throughout the study. Sixty-six of the 70 subjects completed the study. The Cmax (mean ± standard deviation) and AUC0-t (mean ± standard deviation) for naproxen in HCP1004 were 61.67 ± 15.16 µg/mL and 1,206.52 ± 166.46 h · µg/mL, respectively; in VIMOVO(®); these values were 61.85 ± 14.54 µg/mL and 1,211.44 ± 170.01 h · µg/mL, respectively. The Cmax and AUC0-t for esomeprazole in HCP1004 were 658.21 ± 510.91 ng/mL and 1,109.11 ± 1,111.59 h · ng/mL, respectively; for VIMOVO(®), these values were 595.09 ± 364.23 ng/mL and 1,015.12 ± 952.98 h · ng/mL, respectively. The geometric mean ratios and 90% confidence intervals (CIs) (HCP1004 to VIMOVO(®)) of the Cmax and AUC0-t of naproxen were 0.99 (0.94-1.06) and 1.00 (0.98-1.01), respectively. For esomeprazole, the geometric mean ratios (90% CI) for the Cmax and AUC0-t were 0.99 (0.82-1.18) and 1.04 (0.91-1.18), respectively. The overall results of the safety assessment showed no clinically significant issues for either treatment. The PK of HCP1004 500/20 mg was comparable to that of VIMOVO(®) 500/20 mg for both naproxen and esomeprazole after a single oral dose. Both drugs were well-tolerated without any safety issues.

Checkerspot Butterflies, Science, and Conservation Policy: A Grassroots View of Nitrogen Overdose

NASA Astrophysics Data System (ADS)

Weiss, S. B.

2009-12-01

Educating policy makers and the general public about the global “Nitrogen Overdose” has proved challenging because of the complexities of the global nitrogen cycle and its effect on terrestrial, freshwater, estuarine, and marine ecosystems. In this presentation, I present my grassroots experience as a scientist who transitioned into a scientist/activist, working with elected officials, regulators, private industry, activist groups, and the general public, to conserve the rare, beautiful, and charismatic Bay checkerspot butterfly in the San Francisco Bay Area. The butterfly is threatened by atmospheric nitrogen deposition (5-20 kg-N/ha/year) that enriches nutrient poor soils derived from serpentinite rock. This eutrophication allows nitrophilous grasses to invade and displace the dazzling wildflower displays that provide essential food and nectar for the butterfly. Over the past 25 years, I have been involved in all phases of the conservation of this ecosystem, drawing on long-term scientific investigations (literally hundreds of papers by dozens of researchers) on the population dynamics and conservation of the butterfly, and the biogeochemistry of the serpentine grassland ecosystem. Publication of a 1999 paper on N-deposition impacts on the butterfly led to consultations with government agencies and a powerplant company, and development of precedent setting N-deposition mitigation through habitat acquisition and grazing management. This process has evolved into a regional-scale Habitat Conservation Plan (HCP) that is nearing completion in 2010. A key to the success of this ongoing endeavor is education about biodiversity and N-deposition. Field-tours during spring wildflower season put diverse groups of people in direct contact with the obvious beauty of the ecosystem, creating an opening to learning about the complexities of N-deposition, the population biology of the butterfly, and the convoluted conservation history of the sites. Informal tours have developed into a docent program that led more than 1500 people to the site over the past 4 years, including targeted tours for elected officials, decision makers, land managers, and scientists. Outreach has also included more than a dozen articles in local, regional, and national press, television spots, public presentations (Kiwanis, garden clubs, local conferences), and behind the scenes work in policy development for the HCP. When political decisions on the HCP are finalized in the next year, there will be a cadre of educated people, motivated by first hand experience with the ecosystem, to support final approval and implementation of a rigorous plan that will secure the butterfly, numerous imperiled plants, and the entire flower-filled ecosystem. The experience provides a case study and model of how effective grassroots action by concerned scientists can make a difference.

Confocal microscopic observation of structural changes in glass-ionomer cements and tooth interfaces.

PubMed

Watson, T F; Pagliari, D; Sidhu, S K; Naasan, M A

1998-03-01

This study aimed to develop techniques to allow dynamic imaging of a cavity before, during and after placement of glass-ionomer restorative materials. Cavities were cut in recently extracted third molars and the teeth longitudinally sectioned. Each hemisected tooth surface was placed in green modelling compound at 90 to the optical axis of the microscope. The cavity surface was imaged using a video rate confocal microscope in conjunction with an internally focusable microscope objective. The sample on the stage was pushed up to the objective lens which 'clamped' the cover glass onto it. Water, glycerine or oil was placed below the coverglass, with oil above. Internal tooth structures were imaged by changing the internal focus of the objective. The restorative material was then placed into the cavity. Video images were stored either onto video tape or digitally, using a frame grabber, computer and mass memory storage. Software controls produced time-lapse recordings of the interface over time. Preliminary experiments have examined the placement and early maturation of conventional glass-ionomer cements and a syringeable resin-modified glass-ionomer cement. Initial contact of the cement matrix and glass particles was visible as the plastic material rolled past the enamel and dentine, before making a bond. Evidence for water movement from the dentine into the cement has also been seen. After curing, the early dimensional changes in the cements due to water flux were apparent using the time-lapse facility. This new technique enables examination of developing tooth/restoration interfaces and the tracking of movement in materials.

Sealing of cracks in cement using microencapsulated sodium silicate

NASA Astrophysics Data System (ADS)

Giannaros, P.; Kanellopoulos, A.; Al-Tabbaa, A.

2016-08-01

Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

Efficient management of cardiovascular risk screening programs

NASA Technical Reports Server (NTRS)

Roth, Carol

1993-01-01

The Environmental Health Unit, located on-site at the the Goddard Space Flight Center (GSFC), is responsible for the implementation of the Center's Employee Environmental and Occupational Health Program. The Health Unit, Health Physics (HP), and Industrial Hygiene (IH) staffs collaborate to provide quality service to the employees at GSFC. The Health Unit staff identifies, evaluates, and ensures the control of occupational hazards on the Center. In the past, components of the Industrial Hygiene Program have included the Industrial Hygiene Health Hazard Identification Program (IHHIP), the Hearing Conservation Program (HCP), the Hazard Communication Program, and the bi-annual fume hood survey. More recently, the Environmental Health Unit has expanded its services by adding the Ergonomics Program. Various aspects of the Ergonomics Program are discussed.

Impact of hydrated cement paste quality and entrained air-void system on the durability of concrete : part B.

DOT National Transportation Integrated Search

2011-06-30

This publication is a statistical review of reported motor vehicle crashes in Maine during the five-year study period 2005 - 2009. The statistics are compiled from crash reports submitted to the Department of Transportation by the Traffic Division, D...

Detecting deleterious fine particles in concrete aggregates and defining their impact : research brief.

DOT National Transportation Integrated Search

2011-02-01

As concrete hardens, it develops mechanical properties such as strength and stiffness that depend in part on the ratios of the water, cement paste and aggregate gravel that compose it. While enough water must be added to concrete so it can be mixed, ...

Ultrahigh pressure deformation of polycrystaline hcp-cobalt

NASA Astrophysics Data System (ADS)

Merkel, S.; Antonangeli, D.; Fiquet, G.; Yagi, T.

2003-12-01

During the past few years, a novel set of methods has been developed allowing direct measurements on elasticity and rheology under static ultrahigh pressures using synchrotron x-ray diffraction and the diamond anvil cell. In particular, the analysis on the development of texture and uniaxial stress in a polycrystalline sample under ultrahigh pressure and non-hydrostatic conditions yielded to very interesting results on the microscopic deformation mechanisms and strength of MgO, silicate perovskite or ɛ -Fe [eg. Merkel et al. 2002, Merkel et al. 2003]. However, our understanding of the properties of the ɛ phase of iron remains poor. There are considerable uncertainties and disagreement on the results of various experiments or first-principles calculations. In particular, the results of the radial diffraction measurement on ɛ -Fe [Mao et al. 1998] have been highly controversial. In order to address this issue, we performed investigations on polycrystalline hcp-cobalt. Its properties such as the bulk modulus and thermal expansion are very close to those of ɛ -Fe and it is readily available under ambient conditions. Thus, it is a well known material and results from the high pressure radial diffraction experiments can be compared with those from well-established techniques. In the present analysis, we performed a new set a measurements between 0 and 20 GPa under ambient temperature conditions at the ESRF synchrotron source using amorphous boron gasket, monochromatic x-ray beam, and imaging plate techniques. From such an experiment, we are able to extract information on non-hydrostatic stress, elasticity, and preferred orientations of the sample in-situ under high pressure and compare them with results obtained previously on ɛ -Fe. Documenting the evolution of stress, elasticity and texture in hcp metals is of great interest for our understanding of the bulk properties and seismic anisotropy of the Earth's inner core. S. Merkel et al., J. Geophys. Res. 107 (2002) doi: 10.129/2001JB000920. S. Merkel et al., Earth Planet. Sci. Lett. 209 (2003) 351. H. Mao et al., Nature 396 (1998), 741

78 FR 15374 - Notice of Availability of Draft Habitat Conservation Plan; Receipt of Application for Incidental...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-11

... is 0.97 acres within the HCP boundary. Surveys have not been conducted for Hine's Emerald Dragonfly... pipeline maintenance to document the extent of actual excavation and site restoration. No surveys are... application, HCP, EAS) may be obtained on the Internet at the following address: http://www.fws.gov/midwest...

Using Scientific Information to Develop Management Strategies for Commercial Redwood Timberlands

Treesearch

Jeffrey C. Barrett

2007-01-01

In 1999, PALCO (Pacific Lumber Company), a private landowner, and the state and federal governments agreed to implement a unique Habitat Conservation Plan (HCP) on 89,000 hectares of commercial redwood and Douglas-fir timberlands in Humboldt County, California. The aquatics portion of the PALCO HCP contains a set of "interim" conservation strategies developed...

Diffusion anisotropy of poor metal solute atoms in hcp-Ti

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scotti, Lucia, E-mail: lxs234@bham.ac.uk; Mottura, Alessandro, E-mail: a.mottura@bham.ac.uk

2015-05-28

Atom migration mechanisms influence a wide range of phenomena: solidification kinetics, phase equilibria, oxidation kinetics, precipitation of phases, and high-temperature deformation. In particular, solute diffusion mechanisms in α-Ti alloys can help explain their excellent high-temperature behaviour. The purpose of this work is to study self- and solute diffusion in hexagonal close-packed (hcp)-Ti, and its anisotropy, from first-principles using the 8-frequency model. The calculated diffusion coefficients show that diffusion energy barriers depend more on bonding characteristics of the solute rather than the size misfit with the host, while the extreme diffusion anisotropy of some solute elements in hcp-Ti is a resultmore » of the bond angle distortion.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adidharma, Hertanto, E-mail: adidharm@uwyo.edu; Tan, Sugata P.

Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T{sup ∗} ≤ 1.20) and high densities (0.96 ≤ ρ{sup ∗} ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe themore » properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.« less

A facile method for isolation of recombinant human apolipoprotein A-I from E. coli

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikon, Nikita; Shearer, Jennifer; Liu, Jianfang

Apolipoprotein (apo) A-I is the major protein component of high-density lipoprotein (HDL) and plays key roles in the Reverse Cholesterol Transport pathway. In the past decade, reconstituted HDL (rHDL) has been employed as a therapeutic agent for treatment of atherosclerosis. The ability of rHDL to promote cholesterol efflux from peripheral cells has been documented to reduce the size of atherosclerotic plaque lesions. However, development of apoA-I rHDL-based therapeutics for human use requires a cost effective process to generate an apoA-I product that meets “Good Manufacturing Practice” standards. Methods available for production and isolation of unmodified recombinant human apoA-I at scalemore » are cumbersome, laborious and complex. To overcome this obstacle, a streamlined two-step procedure has been devised for isolation of recombinant untagged human apoA-I from E. coli that takes advantage of its ability to re-fold to a native conformation following denaturation. Heat treatment of a sonicated E. coli supernatant fraction induced precipitation of a large proportion of host cell proteins (HCP), yielding apoA-I as the major soluble protein. Reversed-phase HPLC of this material permitted recovery of apoA-I largely free of HCP and endotoxin. In conclusion, purified apoA-I possessed α-helix secondary structure, formed rHDL upon incubation with phospholipid and efficiently promoted cholesterol efflux from cholesterol loaded J774 macrophages.« less

A facile method for isolation of recombinant human apolipoprotein A-I from E. coli

DOE PAGES

Ikon, Nikita; Shearer, Jennifer; Liu, Jianfang; ...

2017-03-20

Apolipoprotein (apo) A-I is the major protein component of high-density lipoprotein (HDL) and plays key roles in the Reverse Cholesterol Transport pathway. In the past decade, reconstituted HDL (rHDL) has been employed as a therapeutic agent for treatment of atherosclerosis. The ability of rHDL to promote cholesterol efflux from peripheral cells has been documented to reduce the size of atherosclerotic plaque lesions. However, development of apoA-I rHDL-based therapeutics for human use requires a cost effective process to generate an apoA-I product that meets “Good Manufacturing Practice” standards. Methods available for production and isolation of unmodified recombinant human apoA-I at scalemore » are cumbersome, laborious and complex. To overcome this obstacle, a streamlined two-step procedure has been devised for isolation of recombinant untagged human apoA-I from E. coli that takes advantage of its ability to re-fold to a native conformation following denaturation. Heat treatment of a sonicated E. coli supernatant fraction induced precipitation of a large proportion of host cell proteins (HCP), yielding apoA-I as the major soluble protein. Reversed-phase HPLC of this material permitted recovery of apoA-I largely free of HCP and endotoxin. In conclusion, purified apoA-I possessed α-helix secondary structure, formed rHDL upon incubation with phospholipid and efficiently promoted cholesterol efflux from cholesterol loaded J774 macrophages.« less

A survey of probiotic use practices among patients at a tertiary medical centre.

PubMed

Draper, K; Ley, C; Parsonnet, J

2017-05-30

Probiotic use has skyrocketed in recent years. Little is known, however, about patient knowledge and practices regarding probiotic use, especially in the context of antibiotic use. An invitation to complete a short, anonymous, electronic survey was sent by email to 965 patients at a tertiary medical centre in California who had agreed to be contacted for participation in research studies. Questions were asked about both probiotic and antibiotic use in the prior three months. Of 333 survey respondents, 55% had recently used probiotics, including food products and/or supplements (90 and 60% of probiotic users, respectively). Women were more likely than men to have used probiotics (odds ratio (OR): 1.99; 95% confidence interval (CI): 1.2-3.4). Health care providers (HCP) had prescribed antibiotics to 79 (24%) respondents in the preceding three months. Among antibiotic users, 33% had initiated or changed probiotics at the time of antibiotic use, usually without a recommendation from their prescribing HCP (72%). Only 12% of those who took probiotics with antibiotics had received a specific recommendation from their HCP. Most patients chose to take probiotic mixtures (56%), with few selecting evidence-based strains, such as Lactobacillus rhamnosus GG (11%). Regular probiotic use among patients is common. Typically, these probiotics are not recommended by a HCP, even in conjunction with antibiotic prescriptions. While a growing body of evidence supports specific probiotic strains for the prevention of antibiotic-associated diarrhoea, patients are often not receiving a specific recommendation from their HCP and appear to be taking strains without guidance from supporting evidence.

Falls in multiple sclerosis.

PubMed

Matsuda, Patricia N; Shumway-Cook, Anne; Bamer, Alyssa M; Johnson, Shana L; Amtmann, Dagmar; Kraft, George H

2011-07-01

To examine incidence, associated factors, and health care provider (HCP) response to falls in persons with multiple sclerosis (MS). Cross-sectional retrospective design. Community setting. Four hundred seventy-four persons with MS. Mailed survey questionnaire examined incidence, risk factors, and HCP response to falls in persons with MS who were dwelling in the community. Univariate and multiple ordinal regression analysis identified variables associated with single and multiple falls. Falls, causes and perceived reasons for falls, and HCP response. A total of 265 participants (58.2%) reported one or more falls in the previous 6 months, and 58.5% of falls were medically injurious. Trips/slips while walking accounted for 48% of falls. Factors associated with falls included use of a cane or walker (odds ratio [OR] 2.62; 95% confidence interval [CI] 1.66-4.14), income <$25,000 (OR 1.85; 95% CI 1.13-3.04), balance problems (OR 1.28; 95% CI 1.11-1.49), and leg weakness (OR 1.26; 95% CI 1.09-1.46). Fifty-one percent of those who fell (135/265) reported speaking to an HCP about their falls; recommended strategies included safety strategies (53.2%), use of gait assistive devices (42.1%), exercise/balance training (22.2%), and home modifications (16.6%). Factors associated with falls in persons with MS are similar to those in other populations with neurologic diseases. Despite the high incidence of falls, fewer than 50% of people with MS receive information about prevention of falls from an HCP. Copyright © 2011 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Hereditary chronic pancreatitis

PubMed Central

Rosendahl, Jonas; Bödeker, Hans; Mössner, Joachim; Teich, Niels

2007-01-01

Hereditary chronic pancreatitis (HCP) is a very rare form of early onset chronic pancreatitis. With the exception of the young age at diagnosis and a slower progression, the clinical course, morphological features and laboratory findings of HCP do not differ from those of patients with alcoholic chronic pancreatitis. As well, diagnostic criteria and treatment of HCP resemble that of chronic pancreatitis of other causes. The clinical presentation is highly variable and includes chronic abdominal pain, impairment of endocrine and exocrine pancreatic function, nausea and vomiting, maldigestion, diabetes, pseudocysts, bile duct and duodenal obstruction, and rarely pancreatic cancer. Fortunately, most patients have a mild disease. Mutations in the PRSS1 gene, encoding cationic trypsinogen, play a causative role in chronic pancreatitis. It has been shown that the PRSS1 mutations increase autocatalytic conversion of trypsinogen to active trypsin, and thus probably cause premature, intrapancreatic trypsinogen activation disturbing the intrapancreatic balance of proteases and their inhibitors. Other genes, such as the anionic trypsinogen (PRSS2), the serine protease inhibitor, Kazal type 1 (SPINK1) and the cystic fibrosis transmembrane conductance regulator (CFTR) have been found to be associated with chronic pancreatitis (idiopathic and hereditary) as well. Genetic testing should only be performed in carefully selected patients by direct DNA sequencing and antenatal diagnosis should not be encouraged. Treatment focuses on enzyme and nutritional supplementation, pain management, pancreatic diabetes, and local organ complications, such as pseudocysts, bile duct or duodenal obstruction. The disease course and prognosis of patients with HCP is unpredictable. Pancreatic cancer risk is elevated. Therefore, HCP patients should strongly avoid environmental risk factors for pancreatic cancer. PMID:17204147

Training hospital providers in basic CPR skills in Botswana: Acquisition, retention and impact of novel training techniques☆

PubMed Central

Meaney, Peter A.; Sutton, Robert M.; Tsima, Billy; Steenhoff, Andrew P.; Shilkofski, Nicole; Boulet, John R.; Davis, Amanda; Kestler, Andrew M.; Church, Kasey K.; Niles, Dana E.; Irving, Sharon Y.; Mazhani, Loeto; Nadkarni, Vinay M.

2013-01-01

Objective Globally, one third of deaths each year are from cardiovascular diseases, yet no strong evidence supports any specific method of CPR instruction in a resource-limited setting. We hypothesized that both existing and novel CPR training programs significantly impact skills of hospital-based healthcare providers (HCP) in Botswana. Methods HCP were prospectively randomized to 3 training groups: instructor led, limited instructor with manikin feedback, or self-directed learning. Data was collected prior to training, immediately after and at 3 and 6 months. Excellent CPR was prospectively defined as having at least 4 of 5 characteristics: depth, rate, release, no flow fraction, and no excessive ventilation. GEE was performed to account for within subject correlation. Results Of 214 HCP trained, 40% resuscitate ≥1/month, 28% had previous formal CPR training, and 65% required additional skills remediation to pass using AHA criteria. Excellent CPR skill acquisition was significant (infant: 32% vs. 71%, p < 0.01; adult 28% vs. 48%, p < 0.01). Infant CPR skill retention was significant at 3 (39% vs. 70%, p < 0.01) and 6 months (38% vs. 67%, p < 0.01), and adult CPR skills were retained to 3 months (34% vs. 51%, p = 0.02). On multivariable analysis, low cognitive score and need for skill remediation, but not instruction method, impacted CPR skill performance. Conclusions HCP in resource-limited settings resuscitate frequently, with little CPR training. Using existing training, HCP acquire and retain skills, yet often require remediation. Novel techniques with increased student: instructor ratio and feedback manikins were not different compared to traditional instruction. PMID:22561463

Differences in Child Passenger Safety Counseling Frequency and Attitudes by Health Care Provider Specialty.

PubMed

Huseth-Zosel, Andrea L; Orr, Megan

2016-12-01

Many children are not being properly restrained in motor vehicles, resulting in unnecessary injury and fatalities. Health care provider (HCP) education is effective at increasing proper child restraint within vehicles. However, differences exist by HCP specialty in regards to frequency of child passenger safety (CPS) counseling. This study of a sample of 255 HCPs examined differences in CPS counseling by HCP specialty (pediatric vs. non-pediatric). HCPs from several upper Midwest states were surveyed about how frequently they provide CPS counseling in their practice by patient age and their attitudes toward CPS-related issues. Pediatric HCPs were twice as likely as non-pediatric HCPs to always provide CPS counseling to parents/guardians of children aged 5 or older. Non-pediatric HCPs were more likely than pediatric HCPs to feel that counseling is ineffective at increasing child seat/booster (p = 0.001) or seat belt use (p = 0.006). Non-pediatric HCPs were more likely than pediatric HCPs to feel there is inadequate time to provide CPS counseling in their practice setting (p = 0.001), and were less likely to know where to refer patients if they have questions regarding CPS issues (0.0291). The differences in HCP attitudes toward CPS counseling provision and the resulting differences in counseling frequency by patient age may contribute to disparities for patients who have limited or no access to pediatric HCPs. Additional research is needed to investigate the rationale for counseling differences seen by HCP specialty and patient age, and the potential effect on child motor vehicle injuries and fatalities.

Evolution of the pore structure during the early stages of the alkali-activation reaction: An in situ small-angle neutron scattering investigation

DOE PAGES

White, Claire E.; Olds, Daniel P.; Hartl, Monika; ...

2017-02-01

The long-term durability of cement-based materials is influenced by the pore structure and associated permeability at the sub-micrometre length scale. With the emergence of new types of sustainable cements in recent decades, there is a pressing need to be able to predict the durability of these new materials, and therefore nondestructive experimental techniques capable of characterizing the evolution of the pore structure are increasingly crucial for investigating cement durability. Here, small-angle neutron scattering is used to analyze the evolution of the pore structure in alkali-activated materials over the initial 24 h of reaction in order to assess the characteristic poremore » sizes that emerge during these short time scales. By using a unified fitting approach for data modeling, information on the pore size and surface roughness is obtained for a variety of precursor chemistries and morphologies (metakaolin- and slag-based pastes). Furthermore, the impact of activator chemistry is elucidatedviathe analysis of pastes synthesized using hydroxide- and silicate-based activators. It is found that the main aspect influencing the size of pores that are accessible using small-angle neutron scattering analysis (approximately 10–500 Å in diameter) is the availability of free silica in the activating solution, which leads to a more refined pore structure with smaller average pore size. Furthermore, as the reaction progresses the gel pores visible using this scattering technique are seen to increase in size.« less

Chemical-mineralogical characterization of C&D waste recycled aggregates from São Paulo, Brazil.

PubMed

Angulo, S C; Ulsen, C; John, V M; Kahn, H; Cincotto, M A

2009-02-01

This study presents a methodology for the characterization of construction and demolition (C&D) waste recycled aggregates based on a combination of analytical techniques (X-ray fluorescence (XRF), soluble ions, semi-quantitative X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTG) and hydrochloric acid (HCl) selective dissolution). These combined analytical techniques allow for the estimation of the amount of cement paste, its most important hydrated and carbonated phases, as well as the amount of clay and micas. Details of the methodology are presented here and the results of three representative C&D samples taken from the São Paulo region in Brazil are discussed. Chemical compositions of mixed C&D aggregate samples have mostly been influenced by particle size rather than the visual classification of C&D into red or grey and geographical origin. The amount of measured soluble salts in C&D aggregates (0.15-25.4mm) is lower than the usual limits for mortar and concrete production. The content of porous cement paste in the C&D aggregates is around 19.3% (w/w). However, this content is significantly lower than the 43% detected for the C&D powders (<0.15 mm). The clay content of the powders was also high, potentially resulting from soil intermixed with the C&D waste, as well as poorly burnt red ceramic. Since only about 50% of the measured CaO is combined with CO(2), the powders have potential use as raw materials for the cement industry.

Leaching Behavior of Heavy Metals from Cement Pastes Using a Modified Toxicity Characteristic Leaching Procedure (TCLP).

PubMed

Huang, Minrui; Feng, Huajun; Shen, Dongsheng; Li, Na; Chen, Yingqiang; Shentu, Jiali

2016-03-01

As the standard toxicity characteristic leaching procedure (TCLP) can not exhaust the acid neutralizing capacity of the cement rotary kiln co-processing solid wastes products which is particularly important for the assessment of the leaching concentrations of heavy metals. A modified TCLP was proposed. The extent of leaching of heavy metals is low using the TCLP and the leaching performance of the different metals can not be differentiated. Using the modified TCLP, however, Zn leaching was negligible during the first 180 h and then sharply increased (2.86 ± 0.18 to 3.54 ± 0.26 mg/L) as the acidity increased (pH < 6.0). Thus, Zn leaching is enhanced using the modified TCLP. While Pb leached readily during the first 126 h and then leachate concentrations decreased to below the analytical detection limit. To conclude, this modified TCLP is a more suitable method for these cement rotary kiln co-processing products.

Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr; Bertron, Alexandra; Larreur-Cayol, Steeves

2015-03-15

Interactions of short-chain organic acids with hydrated cement phases affect structure durability in the agro-food and nuclear waste industries but can also be used to modify cement properties. Most previous studies have been experimental, performed at fixed concentrations and pH, without quantitatively discriminating among polyacidity effects, or complexation and salt precipitation processes. This paper addresses such issues by thermodynamic equilibrium calculations for acetic, citric, oxalic, succinic acids and a simplified hydrated CEM-I. The thermodynamic constants collected from the literature allow the speciation to be modeled over a wide range of pH and concentrations. Citric and oxalic had a stronger chelatingmore » effect than acetic acid, while succinic acid was intermediate. Similarly, Ca-citrate and Ca-oxalate salts were more insoluble than Ca-acetate and Ca-succinate salts. Regarding aluminium complexation, hydroxyls, sulfates, and acid competition was highlighted. The exploration of acid mixtures showed the preponderant effect of oxalate and citrate over acetate and succinate.« less