Radiopaque acrylic bone cements with bromine‐containing monomer

One important issue for the acrylic bone cements concerns the radiopacity, which may be achieved by different ways. In this work, a new bromine‐containing acrylic monomer, the 2‐(2‐bromopropionyloxy) propyl methacrylate (BPPM), was synthesized and proposed to be used for providing radiopaque bone cements. Different acrylic bone cements were realized by partially replacing the methyl methacrylate (MMA) monomer phase with 5–20% w/w of BPPM‐comonomer. The effect of this comonomer on the curing parameters of acrylic bone cements, on their thermal and rheological properties, water absorption, density, contact angle, compression tests, and radiopacity was studied. It appears that the presence of BPPM does provide radiopacity, improves the curing parameters by decreasing the maximum curing temperature and increasing the setting time. The new BPPM‐acrylic bone cements exhibit lower glass transition temperature and better thermal stability when compared with the classical radiolucent acrylic cements. Rheological measurements have shown that 10–20% w/w of BPPM in the liquid phase of acrylic bone cement formulations increase its flexibility, and may also induce a slight crosslinking reaction during the curing phase. BPPM‐modified acrylic bone cements present lower polymerization shrinkage and higher compression strength, and similar water uptake, porosity, and water contact angle as the radiolucent PMMA‐cements. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Role of polymer-clay interactions and nano-clay dispersion on the viscoelastic response of supercritical CO2 dispersed polyvinylmethylether (PVME)-Clay nanocomposites

Clay dispersion and polymer-clay interactions play a key role in producing property enhancements in nanocomposites; yet characterizing them in complex polymer-clay systems is often a challenge. Rheology can offer insights into clay dispersion and clay-polymer interactions. We have investigated the viscoelastic response for a series of supercritical CO₂ (scCO₂) processed polyvinylmethylether (PVME)/clay nanocomposites with varying polymer-clay interactions and nano-clay dispersion. PVME is used in this study because it is highly swellable in scCO₂, thereby enabling processing of PVME/clay mixtures without the presence of a co-solvent. Since PVME and natural clay are water-soluble, highly dispersed PVME-clay nanocomposites were prepared using water, followed by lyophilization in the presence of polymer. In this ‘weakly interacting’, but highly dispersed systems, with clay loadings above the percolation threshold, terminal behavior was observed in the linear viscoelastic moduli (i.e. no low frequency plateau is observed). When the nanocomposites were processed in scCO₂, with 15 wt% of 30B and I.30P, the WAXD patterns of the resultant nanocomposites were largely comparable, indicating partial dispersion, with intercalation peaks. However, the rheology of these two nanocomposites were significantly different despite similar inorganic volume loading (4 vol%). Even with less dispersion compared to the water-based system, the low-frequency moduli were significantly more enhanced, accompanied by a plateau, and a cross-over frequency shift. Neglecting the small differences in the actual clay content between these clays (4-5 vol% of inorganic matter), this suggests that rheology may be sensitive to strong interactions between the clay surfactant and the polymer. Therefore, polymer-clay interactions and clay-clay interactions may both be important in the ability to sustain a “so-called” percolated network, rather than just clay dispersion.     

Quantum-SAR Extension of the Spectral-SAR Algorithm. Application to Polyphenolic Anticancer Bioactivity

Aiming to assess the role of individual molecular structures in the molecular mechanism of ligand-receptor interaction correlation analysis, the recent Spectral-SAR approach is employed to introduce the Quantum-SAR (QuaSAR) “wave” and “conversion factor” in terms of difference between inter-endpoint inter-molecular activities for a given set of compounds; this may account for inter-conversion (metabolization) of molecular (concentration) effects while indicating the structural (quantum) based influential/detrimental role on bio-/eco- effect in a causal manner rather than by simple inspection of measured values; the introduced QuaSAR method is then illustrated for a study of the activity of a series of flavonoids on breast cancer resistance protein.     

A new definition of threshold voltage in Tunnel FETs

This work reports on the physical definition and extraction of threshold voltage in Tunnel FETs (field effect transistors) based on numerical simulation data. It is shown that the Tunnel FET has the outstanding property of having two threshold voltages: one in terms of gate voltage, V_TG, and one in terms of drain voltage, V_TD. These threshold voltages can be physically defined based on the transition between a quasi-exponential dependence, and a linear dependence of the drain current on V_GS or V_DS, and by extension, on the saturation of the tunneling energy barrier width narrowing. The extractions of V_TG and V_TD are performed based on the transconductance change method in the double gate Tunnel FET with a high-k dielectric, and a systematic comparison with the constant current method is reported. The effect of gate length scaling on these Tunnel FETs’ threshold voltages, as well as the dependence of V_TG on applied drain voltage and V_TD on applied gate voltage, are investigated.     

A meta-analysis on the effect of dietary application of exogenous fibrolytic enzymes on the performance of dairy cows

The aim of this study was to use meta-analytical methods to estimate effects of adding exogenous fibrolytic enzymes (EFE) to dairy cow diets on their performance and to determine which factors affect the response. Fifteen studies with 17 experiments and 36 observations met the study selection criteria for inclusion in the meta-analysis. The effects were compared by using random-effect models to examine the raw mean difference (RMD) and standardized mean difference between EFE and control treatments after both were weighted with the inverse of the study variances. Heterogeneity sources evaluated by meta-regression included experimental duration, EFE type and application rate, form (liquid or solid), and method (application to the forage, concentrate, or total mixed ration). Only the cellulase-xylanase (C-X) enzymes had a substantial number of observations (n = 13 studies). Application of EFE, overall, did not affect dry matter intake, feed efficiency but tended to increase total-tract dry matter digestibility and neutral detergent fiber digestibility (NDFD) by relatively small amounts (1.36 and 2.30%, respectively, or <0.31 standard deviation units). Application of EFE increased yields of milk (0.83 kg/d), 3.5% fat-corrected milk (0.55 kg/d), milk protein (0.03 kg/d), and milk lactose (0.05 kg/d) by moderate to small amounts (<0.30 standard deviation units). Low heterogeneity (I?² statistic <25%) was present for yields and concentrations of milk fat and protein and lactose yield. Moderate heterogeneity (I?² = 25 to 50%) was detected for dry matter intake, milk yield, 3.5% fat-corrected milk, and feed efficiency (kg of milk/kg of dry matter intake), whereas high heterogeneity (I?² > 50%) was detected for total-tract dry matter digestibility and NDFD. Milk production responses were higher for the C-X enzymes (RMD = 1.04 kg/d; 95% confidence interval: 0.33 to 1.74), but were still only moderate, about 0.35 standardized mean difference. A 24% numerical increase in the RMD resulting from examining only C-X enzymes instead of all enzymes (RMD = 1.04 vs. 0.83 kg/d) suggests that had more studies met the inclusion criteria, the C-X enzymes would have statistically increased the milk response relative to that for all enzymes. Increasing the EFE application rate had no effect on performance measures. Application of EFE to the total mixed ration improved only milk protein concentration, and application to the forage or concentrate had no effect. Applying EFE tended to increase dry matter digestibility and NDFD and increased milk yield by relatively small amounts, reflecting the variable response among EFE types.     

Coordination polymers

Summary By interfacial polycondensation of Cu,Ni,Co and Mn rezorcylaldehyde-ophenylenediamine sodium salt with terephthalic and isophthalic dichloride respectively, coordination polymers, particularly chelate plyesters, as coloured powders, insoluble in organic solvents, were obtained. The identification of coordination polymers has been carried out by the elementary analysis and IR spectroscopy.     

Optothermal window method for on-line monitoring of decay kinetics of<Emphasis Type="Italic"> trans</Emphasis>-β-carotene in thermally treated vegetable oils

The optothermal window detection method at 488 nm was used to monitor on-line the concentration of trans-ß-carotene that was added to several vegetable oils after treating them at 200 °C in the presence of air for varying amounts of time. Results obtained for extra virgin oil show a direct proportionality between the rate constant describing the disappearance of trans-ß-carotene and the duration of thermal treatment. The rate constant for the decay of trans-ß-carotene in oils treated under identical conditions was also dependent on the type of oil. Trends and individual data are discussed in the light of a possible application of the method for the determination of the oxidative stability of vegetable oils.     

Hierarchical structure formation and pattern replication induced by an electric field

Several techniques based on soft lithography have emerged to replicate micrometre-sized patterns. Similar to most other lithographic methods, these techniques structure a single layer of photo resist. For many applications, however, it is desirable to control the spatial arrangement of more than one component. With traditional methods, this requires an iterative, multistep procedure, making the replication process more complex and less reliable. Here, a replication process is described where multiple materials are processed simultaneously. Using a bilayer formed by two different polymers, electrohydrodynamic instabilities at both polymer surfaces produce a hierarchic lateral structure that exhibits two independent characteristic dimensions. A lateral modulation of the electric field enables replication with a resolution down to 100 nanometres. This approach might provide a simple strategy for large-area, sub-100-nanometre lithography.     

Kinetic data on the polycondensation of tetrachlorobisphenol A with bis(2,3-dichloropropyl) phosphorochloridite

Tetrachlorobisphenol A and bis(2,3 dichloropropyl)phosphorochloridite form a polycondensate with the elimination of HCl and 2,3 dichloropropanol. The polyphosphite formed undergoes an Arbuzov transposition leading to a more stable polyphosphonate. I.r. and ¹H-n.m.r. spectroscopy give support for the described mechanism. From the ¹H-n.m.r. spectral integrals which were registered during the reaction, the separate processes and the rate of consumption of tetrachlorobisphenol A, may be quantitatively determined. The reaction temperature has to be kept below 200°C in order to avoid side reactions.     

Corrosion susceptibility of implant materials Ti-5Al-4V and Ti-6Al-4Fe in artificial extra-cellular fluids

The paper is aimed at detecting the corrosion susceptibility (generated by the potential gradients, due to the pH changes) of implant materials Ti-5Al-4V and Ti-6Al-4Fe alloys exposed in extra-cellular fluids for long term (10 000 exposure hours) in comparison with pure titanium. The titanium and its ternary alloys exhibited spontaneous passivity in Ringer’s solutions of pH=6.98, 4.35 and 2.5, simulating the real situations that can arise in surgical applications. Potential gradients determined in presumptive extreme pH conditions indicate that there is no probability for local corrosion. Impedance spectra were fitted with one time constant equivalent circuit, typically for protective, compact oxide film. The fitting parameters indicate long-term stability of the passive layers in surgical implant conditions. Atomic force microscopy (AFM) and spectral infrared (IR) data are important arguments in supporting the conclusion that titanium and its ternary alloys have a very good corrosion resistance in long-term functional conditions.