One‐Pot Sandmeyer Trifluoromethylation and Trifluoromethylthiolation

Practical one‐pot procedures were developed for both Sandmeyer‐type trifluoromethylations and trifluoromethylthiolations. Starting from broadly available (hetero)aromatic amines, various benzotrifluorides were synthesized in high yields via in situ diazotization and copper‐mediated trifluoromethylation using the inexpensive Ruppert–Prakash trifluoromethylating reagent. In the presence of sodium thiocyanate as a sulfur source, aryl trifluoromethyl thioethers are exclusively formed.

     

Children's performance on pseudoword repetition depends on auditory trace quality: Evidence from event-related potentials.

This study explored the relation between phonological short-term memory and auditory-sensory processing in 7–9-year-old children. Twenty-four participants performed a pseudoword repetition test. The mismatch-negativity (MMN) component of auditory event-related brain potentials was obtained from 9 participants with the highest and 9 participants with the lowest scores on the test. The MMN indexes short-term auditory-sensory memory, including auditory-sensory representations for speech. It was recorded to just perceptible /baga/–/baka/ bisyllabic and easily discriminable 1000/1100-Hz tone contrasts with interstimulus intervals of 350 and 2,000 ms. The high and low repeaters differed significantly in MMN amplitude to speech stimuli at the shorter interstimulus interval. Thus, the accuracy of auditory-sensory processing seems to affect phonological short-term representations in school-age children and therefore may play a role in vocabulary development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Drying of Solid Furl Particlbs in Hot Gases

Drying of solid fuel particles in hot gases ( 50-200c) is studied both theoretically and experimentally. The measurements are carried out by using a thermobalance reactor constructed for drying and pyrolysis studies of particles up to 30 mm by diameter. The model is based on the solution of the conservation equations for mass and energy. The drying is considered to consist of three successive periods: a short initial heating period, period of constant rate of drying and period of falling rate of drying. It is assumed that the particle moisture distribution is uniform during the constant rate of drying. Shrinking core model is assumed for the falling rate period. esides fuel particles, the model is applicable also for other solid particle drying processes. Model calculations are compared to measurements for wood chips. The model can predict the efFect of the main parameters reasonably well. These main parameters affecting the drying rate are: particle size, particle shape, initial particle moisture content, gas temperature and gas moisture content, emperature of the reactor walls and slip velocity. The irregular shape of practical fuel particles can approximately be simulated as one-dimensional case ( plate, cylinder, sphere) by using an equivalent volumc to surface area ratio.     

Reading vertical text from a computer screen

In Western languages, text is traditionally presented in horizontal lines. However, reading of vertically arranged text might be more efficient because of the elimination of horizontal eye movements. We investigated the effect of vertical arrangement upon reading text presented on a computer screen. Even though vertically aligned text was read at a slower rate than horizontally aligned text, the difference was smaller than in previous studies. Analysis of eye-movement data revealed that there were no differences in fixation numbers and numbers of regressions between vertical formats and the standard-text format. But fixation durations were shorter for the standard-text format than for the vertical formats. Taken together, the results indicate that reading vertically presented text from a display device may be nearly as efficient as reading normal horizontal text. Therefore, the fact that text is normally vertically arranged in small-screen devices is not a usability problem.     

The structure and strength of first-year ice ridges in the Baltic Sea

Sea ice ridges are typical features in the Baltic Sea ice pack accounting for on average up to one-third of the total ice mass. They are difficult obstacles to winter navigation and cause large forces on ships and offshore structures. However, the internal structure and strength properties of ice ridges are quite poorly known. This paper presents the results of an experimental project on the structure and strength of first-year ice ridges in the Baltic Sea carried through during 1987–1989. Altogether, six freely floating ridges were investigated. Their total thickness ranges from 4 to 17 m. Valuable field data about the size and shape of ridges, consolidated and unconsolidated parts, block size and porosity have been obtained by drilling and sampling. Divers and underwater video cameras have been used for observing the ridge keel structure. The totally consolidated layer within the ridges was 1–2 times the thickness of the surrounding level ice. The average porosity was 29%. The strength of the keel part has been measured with a full scale loading test. The force required to shear the keel was determined as a function of the normal force, the settlement rate, and the porosity of the keel. The shear strength of the ridge keels was from 1.7 up to more than 4.0 kPa. Also small scale tests were conducted in an ice tank giving results in agreement with the full scale tests.     

Calculation of constrained equilibria by Gibbs energy minimization

The Gibbs energy minimization encompasses active use of the chemical potentials (partial molar Gibbs energies) of the constituents of the system. Usually, these appear at their equilibrium values as a result of the minimization calculation, the mass balance constraints being the necessary subsidiary conditions. Yet, there are several such physico-chemical circumstances where the system is also constrained by other factors, such as surface effects, potential fields or even by chemical reaction kinetics. In this paper a particular method is presented by which constrained chemical potentials can be applied in a multi-phase Gibbs energy minimization. The constrained potentials arise typically from work-related thermodynamic displacements in the system. When Gibbs energy minimization is performed by the Lagrange method, these constraints appear as additional Lagrangian multipliers. Examples of the constrained potential method are presented in terms of the electrochemical Donnan equilibria in aqueous systems containing semi-permeable interfaces, the phase formation in surface-energy controlled systems and in systems with affinities controlled by chemical reaction kinetics. The methods have been applied successfully in calculating distribution coefficients for metal ions together with pH-values in pulp suspensions, in the calculation of surface tension of alloys, and in thermochemical process modeling involving chemical reaction rates.     

Fabrication of optical inverted-rib waveguides using UV-imprinting

In this paper we introduce a fabrication process for polymer rib waveguides that uses UV-imprint lithography. In the structure of an inverted-rib waveguide, the lower cladding of the waveguide is patterned by UV-imprinting and the waveguiding layer is subsequently spin-coated. That makes the thickness of the formed slab layer on the rib waveguide controllable by tuning the spin-coating parameters. The fabrication process utilizes two steps of UV-imprinting. The first one is to form a rigid polymer mold from positive tone photoresist. The second one is to pattern the waveguide lower cladding with the formed polymer mold. Through the two steps of UV-imprinting, rib waveguides can be fabricated without an etching procedure. We demonstrated the proposed fabrication process by fabricating 2-μm-wide waveguides operating in single mode at 1310 nm. With TE-polarized light, the fabricated waveguides show an average transmission of 58.6% in a 30 mm long waveguide, corresponding to a loss of 2.3 dB.     

Thermal Fatigue Endurance of Lead-Free Composite Solder Joints over a Temperature Range of −55°C to 150°C

The thermal fatigue endurance of two lead-free solder/plastic-core solder ball (PCSB) composite joint structures in low-temperature co-fired ceramic (LTCC) modules was investigated using a thermal cycling test over a temperature range of −55°C to 150°C. The investigated solder alloys were Sn-7In-4.1Ag-0.5Cu (SAC-In) and 95.5Sn-4Ag-0.5Cu (SAC). Three failure mechanisms were observed in the test joints. Transgranular (fatigue) cracking mixed with minor intergranular cracking was the dominant failure mechanism at the outer edge of the joints in both test assemblies, whereas separation of the solder/intermetallic compound (IMC) interface and creep cracking occurred in the other parts of the test joints. The propagation rate of the transgranular crack was lower in the SAC-In joints compared with in the SAC joints. Furthermore, the SAC solder seemed to be more prone to separation of the solder/IMC interface, and more severe intergranular (creep) cracking occurred in it compared with in the SAC-In solder. In the thermal cycling test conditions, the better thermal fatigue endurance of the SAC-In solder composite joints resulted in a 75% higher characteristic lifetime compared with the SAC composite joints.     

Association of lumbar artery narrowing, degenerative changes in disc and endplate and apparent diffusion in disc on postcontrast enhancement of lumbar intervertebral disc

Objective  A decreased supply of nutrition to the intervertebral disc can lead to disc degeneration. Nutrient supply can be simulated in vivo by measuring gadolinium enhancement of the disc. We aimed to study the changes associated with disc degeneration that may have effect on the nutrition of the disc, i.e. lumbar artery narrowing, Modic changes, endplate defects, and apparent diffusion coefficient (ADC) in nucleus pulposus. Patients and methods  Twenty male volunteers underwent a lumbar spine examination at 1.5 T for anatomical imaging, diffusion weighted imaging, magnetic resonance angiography, and for T1 relaxation time quantification of contrast enhancement of intervertebral disc. Results  Enhancement of the disc increased with degeneration. Disc space narrowing associated strongly with the enhancement (Pearson’s correlation coefficient 0.46, P < 0.001). The enhancement rate in discs adjacent to Modic type 2 changes was 24%, adjacent to type 1/2 changes 58%, and 13% in the absence of Modic changes. Discs adjacent to endplate defects enhanced 32% compared to 10% of normal endplates. Lumbar artery narrowing or ADC in the disc were not associated with the enhancement. Conclusion  Increased enhancement of a degenerated disc is associated mostly with disc space narrowing and with the presence of degenerative endplate changes and endplate defects.