Γs Values Research Articles

Treatment of saliva contamination of resin core foundation before adhesive luting.

This study aimed to evaluate the influence of surface pretreatment on the shear bond strength of resin luting cement to saliva-contaminated resin core foundation. The surface free energy (γS) of the adherent surfaces was examined. The two-way analysis of variance revealed that the surface pretreatment and storage conditions had a significant effect on the strength of the bond to resin core foundation. The γS values of the saliva-contaminated group were significantly lower than those of the other groups, and they tended to improve after surface pretreatment. The tendency of improvement in γS values differed depending on the type of pretreatment agents. Surface treatment with solutions containing functional monomers is effective in removing saliva contaminants from the resin core foundation surfaces and in creating an effective bonding surface for the resin luting cement.

High-ductility Mg-9Li-1Zn-2Gd-1.2Mn alloy prepared via traditional hot extrusion

The dual-phase Mg-9Li-1Zn-2Gd-1.2Mn alloys were prepared by traditional hot extrusion at 200 °C, 250 °C, and 300 °C, respectively. The microstructure of as-extruded Mg-9Li-1Zn-2Gd-1.2Mn alloy is remarkably refined, and the mechanical properties are significantly improved compared with the as-cast alloy. The Mg-9Li-1Zn-2Gd-1.2Mn alloy extruded at 200 °C exhibits the best comprehensive mechanical properties among the alloys with the yield strength (YS), ultimate tensile strength (UTS), and elongation to failure (εef) are 141 MPa, 166 MPa, and 57%, respectively. The dispersed second phases and Zn segregation along the grain boundary inhibit the growth of recrystallized grains and reduce the grain size, contributing to high ductility. Then, the unstable stacking fault energy of {0001}<11 2‾ 0> slip system (γusf(basal)) and surface energy of {0001} plane (γs(basal)) in Mg and Mg-Li-Gd-Zn supercells are characterized by first-principles calculation. The results indicated that the value of γusf(basal) decreased from 259 mJ/m2 to 249 mJ/m2, while the value of γs(basal) increased from 537 mJ/m2 to 597 mJ/m2. The lower γusf(basal) promotes the initiation of basal slip and higher γs(basal) leads to a lower cracking tendency, revealing the ductility improvement by adding Li, Zn, and Gd elements. This work provides an effective strategy to prepare high-ductility Mg-Li alloys.

Amino acid decorated xanthan gum coatings: Molecular arrangement and cell adhesion

In this work, citric acid molecules mediated simultaneously the crosslinking of xanthan gum (XG) chains and the grafting of glutamic acid (Glu), cysteine (Cys), histidine (His) or tryptophan (Trp) to XG chains, as evidenced by Fourier-transform infrared spectroscopy, elemental and thermogravimetric analyses, and high-resolution X-ray photoelectron spectroscopy. XG coatings (∼60 nm thick) presented total surface energy (γS) of 65 mJ/m². The attachment of amino acids to the XG chains decreased γS values to ∼ 48 mJ/m² because the surface energy polar (γpS) component decreased. Circular dichroism (CD) spectra revealed that the helix conformation of XG chains was retained in XG and XG-Glu-coatings, but it was lost in the XG-His, XG-Cys-and XG-Trp-coatings due to intermolecular interactions between the amino acid side groups (thiol, imidazole, and indole). XG-based coatings presented no cytotoxicity. After 3 h of incubation, the adhesion of SH-5YSY neural cells in comparison to the control (100%) was XG-His (18%), XG-Cys (21.4%), XG (29%), XG-Trp (28.6%) and XG-Glu (46.4%). The decrease of% cell adhesion tended to be favored by the decrease of γpS, except for XG-Glu-and XG-Trp, and by the loss of helix molecular conformation of chains in the coatings.

Surface Energy Changes Involved in Apatite Formation in Copper-Containing Bioactive Glasses

The aim of this work was to use the Washburn capillary rise method to evaluate changes in surface energy promoted by the insertion of CuO in a 58S glass and its implication in bioactivity. The presence of CuO decreased the surface wettability by decreasing the Lewis acid-base component γSAB and increasing the Lifshitz-van der Waals component γSLW. The insertion of CuO also diminished the value of the electron donor parameter γS-; i.e., the number of negative groups. This was accompanied by a nonuniform apatite formation on the surface, likely because the presence of CuO-rich regions with lower electron donor values impaired the adsorption of Ca2+, preventing uniform apatite precipitation. Therefore, surface energy was extremely sensitive to small physical and chemical changes in the glass structure and the behavior of the electron donor parameter could be used as an adequate probe to predict glass bioactivity.

Using contact angle measurement technique for determination of the surface free energy of B-SBA-15-x materials

Pure and boron-containing, Santa Barbara Amorphous (SBA-15) mesoporous materials and B-SBA-15-x (x is molar ratio of Si/B = 50, 30, 10), were synthesized via a direct hydrothermal method. Samples were characterized by XRD, BJH pore size distribution and SEM techniques. A contact angle technique was used to determine surface free energy and its dispersive and polar components. For this purpose, ethylene glycol (EG), di-iodomethane (DIM), formamide (FA) and water were used as model liquids to detect the contact angles. The OWRK/Fowkes approach was used to calculate the surface free energy values. Total surface free energy (γS) values of pure SBA-15 and B-SBA-15-50, B-SBA-15-30, B-SBA-15-10 were calculated as 64.365, 63.545, 63.490 and 64.218 mJ/m2 at room temperature, respectively. The main results of the study can be summarized as follows: (i) The contact angle measurement technique is suitable for determining the total surface free energy (γS) and its dispersive and polar components (γSd and γSp, respectively) of SBA-15 mesoporous materials and (ii) Addition of boron did not have a significant impact on the characteristic structure of SBA-15.

Measurement and modelling of the dynamics of NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; surface–atmosphere exchange over the Amazonian rainforest

Abstract. Local and regional modelling of NH3 surface exchange is required to quantify nitrogen deposition to, and emissions from, the biosphere. However, measurements and model parameterisations for many remote ecosystems – such as tropical rainforest – remain sparse. Using 1 month of hourly measurements of NH3 fluxes and meteorological parameters over a remote Amazon rainforest site (Amazon Tall Tower Observatory, ATTO), six model parameterisations based on a bidirectional, single-layer canopy compensation point resistance model were developed to simulate observations of NH3 surface exchange. Canopy resistance was linked to either relative humidity at the canopy level (RHz0′), vapour pressure deficit, or a parameter value based on leaf wetness measurements. The ratio of apoplastic NH4+ to H+ concentration, Γs, during this campaign was inferred to be 38.5 ± 15.8. The parameterisation that reproduced the observed net exchange of NH3 most accurately was the model that used a cuticular resistance (Rw) parameterisation based on leaf wetness measurements and a value of Γs=50 (Pearson correlation r=0.71). Conversely, the model that performed the worst at replicating measured NH3 fluxes used an Rw value modelled using RHz0′ and the inferred value of Γs=38.5 (r=0.45). The results indicate that a single-layer canopy compensation point model is appropriate for simulating NH3 fluxes from tropical rainforest during the Amazonian dry season and confirmed that a direct measurement of (a non-binary) leaf wetness parameter improves the ability to estimate Rw. Current inferential methods for determining Γs were noted as having difficulties in the humid conditions present at a rainforest site.

Flexural Properties and Polished Surface Characteristics of a Structural Colored Resin Composite.

The aim of this study was to determine the flexural properties and surface characteristics of a structural colored resin composite after different finishing and polishing methods, in comparison to those of conventional resin composites. A structural color resin composite, Omnichroma (OM, Tokuyama Corp, Chiyoda City, Tokyo, Japan), and two comparison resin composites, Filtek Supreme Ultra (FS, 3M, St Paul, MN, USA) and Tetric EvoCeram (TE, Ivoclar Vivadent, Schaan, Liechtenstein), were used. The flexural properties of the resin composites were determined in accordance with the ISO 4049 specifications. For surface properties, 70 polymerized specimens of each resin composite were prepared and divided into seven groups of 10. Surface roughness (Sa), gloss (GU), and surface free energy (SFE) were investigated after the following finishing and polishing methods. Three groups of specimens were finished with a superfine-grit diamond bur (SFD), and three with a tungsten carbide bur (TCB). After finishing, one of the two remaining groups was polished with a one-step silicone point (CMP), and the other with an aluminum oxide flexible disk (SSD). A group ground with SiC 320-grit was set as a baseline. The average flexural strength ranged from 116.6 to 142.3 MPa in the following order with significant differences between each value: FS > TE > OM. The average E ranged from 6.8 to 13.2 GPa in the following order with significant differences between each value: FS > TE > OM. The average R ranged from 0.77 to 1.01 MJ/mm3 in the following order: OM > FS > TE. The Sa values of the OM groups polished with CMP and SSD were found to be significantly lower than those of the other resin composites, regardless of the finishing method. The GU values appeared to be dependent on the material and the finishing method used. The OM specimens polished with SSD showed significantly higher GU values than those polished with CMP. Most of the resin composites polished with SSD demonstrated significantly higher γS values compared to the other groups. Extremely strong negative correlations between Sa and GU in the combined data from the three resin composites and each resin composite and between Sa and γS in the OM specimens were observed; GU showed a strong positive correlation with γS in the same material. These findings indicate that both flexural and surface properties are material dependent. Furthermore, the different finishing and polishing methods used in this study were observed to affect the Sa, GU, and SFE of the resin composites.

Cationic Imidazolium Polythiophenes: Effects of Imidazolium-Methylation on Solution Concentration-Driven Aggregation and Surface Free Energy of Films Processed from Solvents with Different Polarity.

Cationic imidazolium-functionalized polythiophenes with single- or double-methylation of the imidazolium ring were used to study the impact of imidazolium-methylation on (i) the solution concentration-driven aggregation in the presence of paramagnetic probes with different ionic and hydrophobic constituents and (ii) their surface free energy (SFE) as spin-coated films deposited on plasma-activated glass. Electron paramagnetic resonance spectroscopy shows that the differences in film structuration between the polymers with different methylations originate from the early stages of aggregation. In the solid state, higher degree of imidazolium-methylation generates smaller values of total SFE, γS, (by around 2 mN/m), which could be relevant in optoelectronic applications. Methylation also causes a decrease in the polar contribution of γS (γSp), suggesting that methylation decreases the polar nature of the imidazolium ring, probably due to the blocking of its H-bonding capabilities. The values of γS obtained in the present work are similar to the values obtained for doped films of neutral conjugated polymers, such as polyaniline, poly(3-hexylthiophene), and polypyrrole. However, imidazolium-polythiophenes generate films with a larger predominance of the dispersive component of γS (γSd), probably due to the motion restriction in the ionic functionalities in a conjugated polyelectrolyte, in comparison to regular dopants. The presence of 1,4-dioxane increases γSp, especially, in the polymer with larger imidazolium-methylation (and therefore unable to interact through H-bonding), probably by a decrease of the imidazolium–glass interactions. Singly-methylated imidazolium polythiophenes have been applied as electrode selective (“buffer”) interlayers in conventional and inverted organic solar cells, improving their performance. However, clear structure–function guidelines are still needed for designing high-performance polythiophene-based interlayer materials. Therefore, the information reported in this work could be useful for such applications.

Effects of Finishing and Polishing Methods on the Surface Roughness and Surface Free Energy of Bulk-fill Resin Composites.

The purpose of this study was to determine the influence of finishing and polishing methods on surface properties of bulk-fill resin composites through surface roughness (Ra) and surface free energy (SFE) measurements, and scanning electron microscopy (SEM) observations. Three bulk-fill resin composites, Tetric EvoCeram Bulk Fill (TB), Filtek Bulk Fill (FB), and Filtek Bulk Fill Flowable Restorative (FF), and two conventional resin composites, Clearfil AP-X (AP) and Estelite ∑ Quick (EQ) were used. Seventy cured specimens of each resin composite were prepared and divided into seven groups of 10 specimens. Ra, SFE measurements, and SEM observations were conducted after finishing and polishing procedures. Three groups of specimens were finished with a fine grit diamond bur (FDB), and three with a tungsten carbide bur (CBB). After finishing, one group from each type of finishing was polished with aluminum oxide flexible disks (SSD) and one group from each type of finishing was polished with diamond particles embedded in a silicone point (CMP). A baseline group of samples that were neither finished nor polished after removing the translucent strips from the surface was examined. Although the baseline group showed significantly lower Ra values than the other groups, most resin composites showed lower Ra values with CBB+SSD than with the other finishing and polishing groups. Among the tested resin composites, EQ showed significantly lower Ra values than the other resin composites, regardless of the finishing and polishing methods. On the other hand, AP showed significantly higher Ra values than the other resin composites in all finishing and polishing groups, apart from FB with FDB. For the finished specimens, most resin composites showed higher SFE values with CBB than with FDB. For the polished specimens, all the tested resin composites with CMP showed lower γS values than those with SSD, regardless of the finishing method. The baseline groups of TB and FB showed significantly lower SFE values than the other finished and polished groups. In the SEM observations, all the examined resin composites showed rougher surfaces after finishing with FDB than with CBB. However, when comparing the different polishing methods (CMP and SSD), surface smoothness appeared to be material dependent.

Influence of Application Time on Dentin Bond Performance in Different Etching Modes of Universal Adhesives.

We attempted to determine the effect of universal adhesive application time on dentin bond performance in different etching modes based on shear bond strength (SBS) tests and surface free energy (SFE) measurements. The five universal adhesives used were Adhese Universal (AU), Clearfil Universal Bond Quick (CQ), G-Premio Bond (GP), Scotchbond Universal (SU), and Tokuyama Universal Bond (TU). Bovine dentin specimens were divided into four groups of 10 for each adhesive. SBS and SFE were determined after applying the following surface treatments: 1) self-etch (SE) mode with immediate air blowing after adhesive application (IA treatment), 2) SE mode with prolonged application time (PA treatment), 3) etch-and-rinse (ER) mode with IA treatment, and 4) ER mode with PA treatment. Bonded specimens were subjected to SBS testing. The SFE of adhesive-treated dentin surfaces was measured after rinsing with acetone and water. Three-way analysis of variance revealed that dentin SBS values (p<0.001) were significantly influenced by the factors of adhesive type and application duration, but the factor of pre-etching was not significant (p=0.985). The manufacturer's instructions require longer application times for AU and SU, which showed significantly lower SBS values in IA than in PA treatment in both etching modes. However, the difference in the other adhesives was not significant between the IA and PA treatments in either etching mode. The total SFE (γS) was dependent on the adhesive and etching mode. The γS value of the initial group (SiC paper ground group) at baseline was 69.5 (mN·m-1) and that of the pre-etching group at baseline was 30.6 (mN·m-1). For all the adhesives, γS in SE mode showed significantly higher values than in ER mode, regardless of the application time. In SE mode, almost all universal adhesives tested showed lower γS values in PA treatment than in IA treatment. For ER mode, all the adhesives showed significantly higher γS values than those of the pre-etching baseline, regardless of the application time. Most adhesives did not show any significant differences in γS values between IA and PA treatments, regardless of etching mode.

Organic–inorganic collagen/iota‐carrageenan/hydroxyapatite hybrid membranes are bioactive materials for bone regeneration

ABSTRACTThis study aimed to produce biomembranes with controlled degradability for application in bone regeneration in order to stimulate biological reactions necessary to improve bone formation. Hydrogels were prepared by dissolving hydrolyzed collagen (HC) and iota‐carrageenan (ι‐Carr) in aqueous mixtures containing CaCl2 and H3PO4. A rise in pH by exposure to NH3(g) caused mineral precipitation into the hydrogel. Subsequently, the membranes were fabricated by solvent casting. Infrared spectroscopy and X‐ray diffraction attested hydroxyapatite formation. The crystallite size was close to 12 nm, which was smaller than the size reported for human bone apatite. The membranes induced bone‐like apatite precipitation in simulated body fluid. The carrageenan content modulated the membrane mechanical behavior. Membranes with controlled degradability were obtained by using higher amount of this polysaccharide. These membranes were able to release HC in physiological conditions. The surface properties were evaluated in terms of wettability and surface energy (γS) by means of contact angle (θc) measurements. Low θc (8.5–16.8) indicated that the hybrid membranes were hydrophilic, while higher γS values, around 70.6 mJ.m−2, could favor biomolecule incorporation into the surface. Our data set evidenced that these materials could potentially be used as a temporary guided tissue regeneration membrane with the possibility of inducing bone regeneration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48004.

Theoretical Study on Second Hyperpolarizabilities of Intramolecular Pancake-Bonded Diradicaloids with Helical Scaffolds

Using the spin-unrestricted density functional theory method, we have investigated a novel class of open-shell singlet fused-ring molecules with helical scaffolds toward the development of highly efficient third-order nonlinear optical (NLO) systems. It turns out that the helical molecules possess pancake bonding with intermediate diradical character and thereby exhibit large enhancement of orientationally-averaged second hyperpolarizability γs values (third-order NLO properties at the molecular scale) as compared to their closed-shell analogues. It is also found that the asymmetric charge distribution between the cofacial radical sites located on both the terminal rings of the helical scaffold leads to further enhancement of the γ value in the intermediate open-shell character region as compared to the open-shell analogues without asymmetric charge distributions. These results indicate that the helical systems with intermediate diradical character are potential candidates for the building block of highly...

Variability of depth-limited waves in coral reef surf zones

Wave breaking and transformation on coral reef flats is an important process protecting tropical coastlines and regulating the energy regimes of coral reefs. However, the high hydraulic roughness, shallow water, and steep bathymetries of coral reefs may confound common surf zone assumptions, such as a depth-limited and saturated surf zone with a constant wave height to water depth ratio (γ). Here, we examine wave transformation across a coral reef flat, during three separate swell events, on both a time-averaged and a wave-by-wave basis. We use the relationship between significant wave height and water depth (γs) to examine the change in surf saturation across the reef flat and compare the measured wave height decay to results of modelled wave energy dissipation in the surf zone. Our results show that γs was not cross-reef constant and varied according to location on the reef flat and local water depth. On average, γs was greatest at the outer reef flat, near the reef crest, and progressively reduced towards the inner reef flat, near the reef lagoon. This was most pronounced in shallow water with large γs values (γs > 0.85) at the outer reef flat and small γs values (γs < 0.1) at the inner reef flat. This indicates that there is an increase in wave energy dissipation in shallow water, most likely due to increased breaker and bed frictional dissipation. The measured wave energy dissipation across the entire reef flat could, on average, be modelled accurately; however, this required location specific calibration of the free parameters, the wave friction factor (fw) and γ, and further suggests that there is no value for either parameter that is universally applicable to coral reef flats. Despite model calibration inaccuracies were still observed, primarily at the outer reef flat. These inaccuracies reflected the observed cross-reef variation of γ on the reef flat and potentially the limitations of random wave breaker dissipation models in complex surf zones. Our results have implications for the use of wave energy dissipation models in predicting breaker dissipation and subsequent benthic community change on coral reef flats, and suggest that careful consideration of the free parameters in such models (such as fw and γ) is required.

Evaluation of salivary surface tension in a cohort of young healthy adults.

To determine salivary pH, flow rate (FR) and surface tension (γs) in a cohort of 30 healthy young adults. To acquire cohort biological independent variables (age, gender, weight, height, medications, smoking, pathologies, and allergies) and to correlate them with pH, FR and γs obtained values. Evaluate the possible variation of the γs values during the time after the withdrawal and the influence of the operational abilities of the experimenting operators. Evaluate the relationship between γs, pH and FR and the dependence between pH and FR. Non-stimulated saliva samples were taken in four different time span, for three days, with a drooling method for 15 minutes. The saliva sample was analyzed, in terms of γs, by two different operators (OP1 and OP2), twice consecutive (γs-1 and γs-2) for a total of 360 measurements. The γs was calculated using the du Noüy method. The FR was evaluated by weighing technique and pH by pH indicator papers. The measurements of γs performed by two different operators (OP1, OP2) showed respectively average values of 46.46 mN/m and 43.45 mN/m, while the mean FR was 0.29 ± 0.13 mL/min and the average pH was 7.1 ± 0.43. There were no significant correlations between γs and the biological variables analyzed. We can consider as reference values, in a sample of young adults, γs 45.56 ± 6.51 mN/m.

Frequency Variation of the AC Order Parameter Susceptibility of the Metamagnetic Ising Model

The extensive investigation of the absorptive and reactive parts of the AC order parameter susceptibility spectra of iron group dihalides, which is obtained on the basis of Onsager theory of irreversible processes, revealed the fact that the diagonal phenomenological rate coefficients γs and γm have an important impact on the nature of the order parameter relaxation process. The number of the relaxation peaks appearing in the double logarithmic plots of χs′′ versus field frequency ω and the number of plateau regions in χs′ spectrum depends on the values of γs and γm. Only for γs≫γm does the relaxation evolve from a simple Debye exponential at high temperatures to a two-step process at lower temperatures in which there exist two long relaxation times characterizing the relaxation of staggered magnetization. In parallel with these characteristics of the order parameter relaxation, Cole-Cole plots (χs′′-χs′) are shown to consist of two arcs in the metamagnetic phase and of a semicircle in the paramagnetic phase.

Wettability of modified silica layers deposited on glass support activated by plasma

Fumed silica modified by hexamethyldisilazane [HDMS] and polydimethylsiloxane [PDMS] was dispersed in a polystyrene/chloroform solution. To increase adhesion between deposited silica layers and a glass surface, the latter was pretreated with air plasma for 30s. The silica/polystyrene dispersion was deposited on the glass support using a spin coater. After deposition, the plates were dried in a desiccator for 24h. Water advancing and receding contact angles were measured using the tilted plate method. The apparent surface free energy (γS) was evaluated using the contact angle hysteresis approach. The surface topography was determined using the optical profilometry method.Contact angles changed from 59.7°±4.4 (at surface coverage with trimethylsilyl groups Θ=0.14) to 155°±3.1 at Θ=1. The value of γS decreased from 51.3±2.8mJ/m2 (for the sample at the lowest value of Θ) to 1.0±0.4mJ/m2 for the most hydrophobic sample. Thus, some systems with a high degree of modification by HDMS showed superhydrophobicity, and the sliding angle amounted to about 16°±2.1.

Interplay of Substrate Surface Energy and Nanoparticle Concentration in Suppressing Polymer Thin Film Dewetting

It is known that dewetting of a polystyrene (PS) thin film on a silicon substrate gets completely suppressed upon addition of small amount of C60 nanoparticles (NP).1 The NPs migrate to the film–substrate interface and forms an enriched surface layer of the particles that eventually stabilizes the film by apparent pinning. In this article we quantitatively highlight the unexplored effect of substrate surface energy (γS) on the migration of the NPs to the film–substrate interface and their contribution on dewetting suppression. Depending on the relative magnitudes of NP concentration (CNP) and γS, we identify three distinct stability regimes. In regime 1 (CNP < 0.2%) there is no suppression of dewetting and the final polygonal arrangement of droplets closely resemble dewetted structures in particle free films. However, the size of the polygons becomes smaller in NP containing films when γS < γC60 (NP surface energy) and larger as γS exceeds γC60. In regime 2 (0.3% < CNP < 0.75%) the films dewet partially, and the extent of dewetting is seen to strongly dependent on the relative magnitudes of γC60 and γS. While dewetting proceeds up to the stage of partial hole growth and coalescence when γS < γC60, some random isolated holes are seen to form when γS > γC60. On the basis of direct AFM imaging, we show that in both regimes 1 and 2 the NPs migrate to the substrate–film interface only when γS > γC60. We show complete suppression of dewetting in regime 3 (CNP > 1.0%), where the particles are seen to migrate to the substrate for all values of γS. The work highlights that entropy driven migration of particles takes place on substrates with any γS only above a critical NP concentration (CNPC) and only on substrates with γS > γC60 when CNP < CNPC. The findings, apart from dewetting suppressing, can guide potential design criteria for applications such as electron extracting layer in organic photovoltaic.

Evaluation of the Haemocompatibility of TiO2 Coatings Obtained by Anodic Oxidation of Ti-6Al-4V

The blood compatibility (haemocompatibility) is a requirement in materials used in prosthetic heart valves. No standardized methods are available to measure haemocompatibility in solid materials. However, a material could be considered haemocompatible if its surface does not modify the normal activation of the coagulation pathway and produces no damage in the blood components. In this work, the haemocompatibility of coatings obtained by anodic oxidation of Ti-6Al-4V (with H2SO4 1M and 40 to 70V) with and without heat treatment (1h for 500°C), is evaluated and compared with the haemocompatibility of the Ti-6Al-4V substrate and pyrolytic carbon. Standard clinical trials for clothing: Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) were adapted to evaluate the haemocompatibility of solid materials. Besides, the interaction between blood platelets and solid material were performed through an analysis of interfacial tension (γi,j), this parameter could indicate the degree of preferential adsorption of each protein of the blood plasma. The ratio between albumin-material and fibrinogen-material interfacial tension, (γs,Alb/ γs,Fib), is an important parameter used to predict the platelets adhesion and the trend at the formation of cloth. The results of the clothing trials indicate that the tested surfaces would be haemocompatibles due to the values of PT and APTT obtained which were in range of the normal ones. In addition, the measured values of γs,Alb/ γs,Fib indicate that all the tested surfaces are more haemocompatible than pyrolitic carbon. The recrystalized films by heat treatment which produce some rutile crystals are the most haemocompatibles.

Nonlinear Optical Properties of a Series of 6,12-Diethynylindeno[1,2-&lt;em&gt;b&lt;/em&gt;]fluorene Derivatives

The polarizabilities (αs) and second hyperpolarizabilities (γs) of a series of 6,12-diethynylindeno (1,2-b)fluorene derivatives were investigated by the density functional theory CAM-B3LYP method. The calculated results indicate that these molecules possess considerably large second hyperpolarizabilities. Replacing the 6,12-hydrogen atoms on indeno(1,2-b)fluorene molecules by ethynyl silyl or oxygen atoms results in a change in the geometry of the molecular structure, which affects the nonlinear optical (NLO) properties. Introducing ethynyl silyl groups into the molecules can increase the αs and γs values, while these values decrease introducing oxygen atoms into the molecules. Also, the γs values depend on the 2, 8-disubstituted R groups (R=H, F, CH3) of the indeno(1,2-b)fluorene molecules. When R is methyl, the molecule has much larger αs and γs values. Moreover, according to time-dependent density functional theory calculations on the indeno(1,2-b)fluorene series, the maximum absorption wavelength of the ethynyl silyl derivatives display a bathochromic shift due to increasing conjugation, while a blue shift of the maximum absorption wavelengths are observed in the oxygen-substituted derivatives because the conjugation decreases as the molecular structure is distorted.

A novel potential: the interlayer potential for the fcc (111) plane family

We propose a novel interlayer potential, which is different from usual interatomic potentials. The interlayer potential represents the interaction between atomic layers in a layered material. Based on the Chen–Möbius inversion method in combination with ab initio calculations, the interlayer interactions are obtained for the face centered cubic (fcc) (111) planes. In order to check the validity of our interlayer potential, we calculate the intrinsic stacking fault energy (γsf) and the surface energy (γs) of five metals: Al, Ni, Cu, Ag and Au. The predicted γsf and γs values are compared with the theoretical results obtained from direct calculations and also with the available experimental data. Using the interlayer potentials, we also investigate the phonon dispersion and phonon density of state in the fcc (111) plane family of the considered metals.