More on the poly(L‐lactide) prepared using ferrous acetate as catalyst

Polylactides were prepared by ring‐opening polymerization (ROP) in bulk using as catalyst either stannous 2‐ethylhexanoate at a monomer to catalyst ratio of 2000, or ferrous acetate (Fe(OAc)₂) at monomer to catalyst ratios of 500, 1000, 2000 and 3000. The crystallization behaviour was studied for the prepared polymers as well as the degradation behaviour both in laboratory and natural compost environments by using differential scanning calorimetry, size exclusion chromatography, X‐ray diffractiometry and microscopy. No differences were apparent due to the choice or amount of catalyst used, except for those which could be related to the increased racemization when the Fe(OAc)₂ was used. Copyright © 2004 Society of Chemical Industry     

Radiographic mensuration characteristics of the sagittal lumbar spine from a normal population with a method to synthesize prior studies of lordosis

This multinational, multicentre, randomised, parallel-group study compared the safety, tolerability and efficacy of ondansetron 8 mg orally twice a day with ondansetron suppository 16 mg once daily in patients receiving cyclophosphamide-containing chemotherapy. A total of 406 patients were randomised to receive ondansetron 8 mg p.o. (198 patients) or ondansetron suppository (208 patients) medication in a double-blind, double-dummy trial. The primary efficacy analysis revealed that ondansetron provided good anti-emetic control with 81% of patients in the 8 mg p.o. b.d. group and 73% of patients in the 16 mg ondansetron suppository o.d. group experiencing complete or major control of emesis (< or = 2 emetic episodes) on the worst day of days 1-3. The 90% confidence interval for the difference between the two treatments for complete or major control (1.4, 15.0%) showed that the treatments could be regarded as equivalent. A difference in favour of oral ondansetron treatment was noted for the complete control (0 emetic episodes) rates over days 1-3, but no differences were found on day 1. There were no significant differences in the distribution of nausea grades between the treatment groups on the worst day of days 1-3 or on day 1. The incidence of adverse events was similar for the two treatment groups, the most frequently reported events were headache and constipation. There were no significant laboratory findings in either treatment group. In conclusion this study showed that the ondansetron treatments could be regarded as equivalent for the primary efficacy endpoint and that ondansetron suppository was well tolerated and effective in the prevention of cyclophosphamide-induced emesis.     

An Eulerian approach for partitioned fluid–structure simulations on Cartesian grids

This paper describes an Eulerian approach for partitioned fluid–structure simulations based on a fluid solver using regularly and adaptively refined Cartesian grids. The particular focus is on the efficient implementation and embedding of the fluid solver in the context of coupled simulations. Special subjects are the efficient layout of data structures and data access based on space-filling curves and the realisation of geometry and topology changes. In addition, a coupling environment is presented that allows for an easy and flexible coupling of flow and structure codes. Simulation results are provided for large particle movements within the drift ratchet scenario.     

Controlling Polymorphism in Poly(3‐Hexylthiophene) through Addition of Ferrocene for Enhanced Charge Mobilities in Thin‐Film Transistors

Crystalline organic molecules often exhibit the ability to assemble into multiple crystal structures depending on the processing conditions. Exploiting this polymorphism to optimize molecular orbital overlap between adjacent molecules in the unit lattice is an effective method for improving charge transport within the material. In this study, grazing incident X‐ray diffraction was employed to demonstrate the formation of tighter π‐π stacking poly(3‐hexylthiophene‐2,5‐diyl) polymorphs in films spin coated from ferrocene‐containing solutions. As a result, the addition of ferrocene to casting solutions yields thin‐film transistors which exhibit approximately three times higher source‐drain currents and charge mobilities than neat polymer devices. Nevertheless, XPS depth profiling and NMR analyses of the active layer reveal that all ferrocene is removed during the spin coating process, which may be an essential factor to achieve high mobilities. Such insights gleaned from ferrocene/poly(3‐hexylthiophene‐2,5‐diyl) mixtures can serve as a template for selection and optimization of other small molecule/polymer systems with greater baseline charge mobilities.     

A First Step for an INL Spectral-Based BIST: The Memory Optimization

Integral non-linearity (INL) is the main static parameter of analog-to-digital converter. This paper presents a comparison between different INL test techniques based on INL estimation from the spectrum of the converted signal. The most common technique is based on polynomial fitting of the INL curve. This technique is well suited to the estimation of a smooth INL curve without sharp transitions. The new method described in the paper is based on a Fourier series expansion of the INL curve. We demonstrate that this new technique allows a more efficient INL estimation. The comparison between the two techniques has been realized thanks to a metrics that considers the uncertainty of production test measurements. Finally, we propose a first step of the study of implementation feasibility of the INL estimation technique. This study focus only on the optimization of required memory.     

Measurement techniques and results of an intercomparison for RFpower in a 3.5 mm coaxial line up to 26 GHz

The methods and results of an international comparison are presented for measurements of RF power in a 3.5 mm coaxial line at seven frequencies up to 26 GHz. Three national laboratories of metrology having different measurement techniques participated in the comparison. The agreement between the mean values of the calibration factor of the traveling standard reported by the participants is well within their reported uncertainties (k=2), which are between 0.5% and 3.1%     

Density functional theory study on adsorption of thiophene on TiO2 anatase (0 0 1) surfaces

In order to develop a fundamental understanding of the adsorption mechanism of thiophenic compounds on TiO₂-based adsorbents for ultra-deep desulfurization of liquid hydrocarbon fuels, a density functional theory (DFT) study was conducted on the adsorption of thiophene over the TiO₂ anatase (0 0 1) surface. The perfect, O-poor (with oxygen vacancies), and O-rich (with activated O₂ on the surface) anatase (0 0 1) surfaces were built, and the interaction of thiophene molecule with these surfaces was examined. The adsorption configuration and adsorption energy on the different surfaces and sites were estimated. The results showed that thiophene may be adsorbed on both the perfect and O-poor surfaces through an interaction between the Ti cations on the surface and the S atom in thiophene, whereas on the O-rich surface through an interaction of the activated O atoms (the dissociatively or associatively adsorbed O₂) on the surface with the S atom in thiophene to form a sulfone-like surface species. The adsorption of thiophene on the O-rich surface is significantly stronger than adsorption on the perfect and O-poor surfaces on the basis of the calculated adsorption energies. The results indicate that the activated O₂ on the TiO₂ anatase (0 0 1) surface may play an important role in the adsorption desulfurization over the TiO₂-based adsorbents, and increased concentration of the activated O₂ on the surface may result in improvement of the adsorption capacity of the adsorbents.     

Electrolyte and temperature effects on pitting corrosion of type 316LN stainless steels

Abstract

The influence of electrolyte composition and temperature on the pitting corrosion resistance of nitrogen bearing (0·015, 0·198, and 0·56%N) type 316L stainless steels has been investi gated. Anodic polarisation curves were determined in neutral chloride solution at room temperature and at elevated temperatures of 308, 318, and 333 K. Similar polarisation studies were also conducted at room temperature in 1N H₂ SO₄ and in an acidic chloride solution containing 1N H₂ SO₄ and 0·5M NaCl. The results show that the critical pitting potential E_pp in neutral chloride and acidic chloride media increases as the nitrogen content of the alloy increases, indicating that resistance to pitting increases with the addition of nitrogen. However, in 1N H₂ SO₄ solution, the transpassive potential was almost independent of the nitrogen content. As the temperature of the neutral chloride medium was increased, the E_pp values decreased, irrespective of nitrogen content. The decrease in E_pp is attributed not only to the temperature induced modification of the passive oxide film but also to chloride induced activity at the passive film/solution interface. Nevertheless, the alloy con taining 0·56% nitrogen showed better resistance to pitting at 333 K than did the alloy with 0·015% nitrogen at room temperature. SEM examination of the pitted specimens showed clear evidence of pitting for the alloy with 0·015% nitrogen, but insignificant pitting attack for the alloy with 0·56%N. However, the alloy with 0·56%N displayed some pitting attack when the experiments were conducted at 333 K.     

Nonphotically induced phase shifts of circadian rhythms in the golden hamster: activity-response curves at different ambient temperatures

Running in a novel wheel during the subjective day can shift the circadian activity rhythm of a hamster. The amount of running is thought to be an important variable. We generated a dose-response (activity-phase shift) curve for the amount of wheel running during a 3 h period starting 8 h before normal dark onset in a 14:10 LD cycle. At room temperature (23 degrees C) the relationship was sigmoidal: from 0 to 4000 revolutions resulted in minimal phase advances (up to 50 min). From 4000 to 5000 revolutions the magnitude of the advances increased sharply, and above 5000 revolutions phase advances were asymptotic at about 3 h. The same general relationship held when hamsters were stimulated to be more active in the novel wheel by lowering the ambient temperature to either 11 degrees C or 6 degrees C. However, at these lower temperatures, a significant number of animals did not shift more than the minimal amount of 50 min even though they ran more than 5000 revolutions. This indicates that running per se in a novel wheel was not sufficient to induce phase shifts. Possibly, at room temperature, the amount of wheel running reflects a particular motivational state produced by the rewarding nature of wheel running, although at low ambient temperatures at least some individuals run primarily to meet thermoregulatory needs.