Rare-earth diiodides and derivatives

The rare-earth diiodides, MI₂, may be synthesized from the corresponding triiodides, MI₃, by reduction with their metals at elevated temperatures or, alternatively, through so-called metallothermic reduction reactions with alkaline or alkaline-earth metals. In these cases, ternary iodides may be obtained that may be derived from the binary diiodides by either formal addition or substitution. Prominent formula types that are thus obtained are A^IMI₃, or the mixed-valent A^I₅M^II₂M^IIII₁₂ and A^IIMI₄ with A^I and A^II representing alkaline or alkaline-earth elements (and their analogues), respectively. Further iodides that are relevant in these systems are, for example, Pr₂I₅, Ba₆Pr₃I₁₉ and interstitially stabilized phases such as {Er₁₄(N₂)(C₂)₂}I₂₄, La₉O₄I₁₆ and Ba{Ce₄N₂}I₈.     

Differential responses to male and female depressive reactions.

Suggests that the commonly reported preponderance of female over male depression in incidence and prevalence studies requires further analysis. One explanation is that the social consequences of expression of depressive symptomatology are different for males and females. A comparison of 157 male and 189 female undergraduates' reactions to male and female case histories of common reactions to stress confirmed the hypothesis. Depression elicited more rejection of males than of females, and the sex difference in rejection of depression was more pronounced than for anxiety or flat affect-detached responses. A discriminant analysis suggested that depressed males are especially likely to be perceived as impaired in role functioning as compared with depressed females. Results suggest that depressed males are not rejected for expression of emotionality as such. Speculations about the causes and consequences of differential rejection of depression are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

X-ray microbeam and recrystallization studies of plastic deformation around fatigue cracks

X-ray microbeam technique and recrystallization method were used to measure plastic zones around 20 kHz fatigue cracks in mild steel. Both methods render approximately the same extension of a plastic zone. In order to obtain the amount of deformation within a plastic zone measurements of integral line breadth and recrystallization temperature were calibrated by specimens deformed with known per cent static tension. But since static and cyclic loading cause different dislocation structures (especially the dislocation density is much more inhomogeneous in fatigued specimens) quantitative comparison is difficult. Furthermore the two methods display different values of the actual amount of deformation. X-ray line broadening indicates an average dislocation density, whereas recrystallization displays a maximum amount of deformation, which corresponds to the local dislocation concentrations.     

SNR enhancement in radial SSFP imaging using partial k-space averaging

The steady-state free precessing (SSFP) sequences, widely used in MRI today, acquire data only during a short fraction of the repetition time (TR). Thus, they exhibit a poor scan efficiency. In this paper, a novel approach to extending the acquisition window for a given TR without considerably modifying the basic sequence is explored for radial SSFP sequences. The additional data are primarily employed to increase the signal-to-noise ratio, rather than to improve the temporal resolution of the imaging. The approach is analyzed regarding its effect on the image SNR (signal to noise ratio) and the reconstruction algorithm. Results are presented for phantom experiments and cardiac functions studies. The gain in SNR is most notable in rapid imaging, since SNR enhancement for a constant repetition time may be used to compensate for the increase in noise resulting from angular undersampling.     

Surface properties of wood and MDF after ultrasonic-assisted cutting

Surfaces created by ultrasonic-assisted cutting (UC) of beech and spruce and of medium density fibreboard (MDF) are compared to surfaces obtained by conventional linear cutting (CC) using a sharp tool. Topography is evaluated performing roughness measurements and scanning electron microscopy. No effect of UC procedure on mean roughness is found. The surface of MDF and large areas of the surfaces of the woods appear similar after UC and CC, whereas other regions show impact marks and microscopic reels produced by the periodic oscillation of the tool in UC. The wettability of surfaces produced with both wood processing techniques is similar. Surface free energy measurements indicate accelerated ageing caused by UC, probably due to heating.     

Fluoroscopy-based 3-D reconstruction of femoral bone cement: a new approach for revision total hip replacement

In revision total hip replacement the removal of the distal femoral bone cement can be a time consuming and risky operation due to the difficulty in determining the three-dimensional (3-D) boundary of the cement. We present a new approach to reconstruct the bone cement volume by using just a small number of calibrated multiplanar X-ray images. The modular system design allows the surgeon to react intraoperatively to problems arising during the individual situation. When encountering problems during conventional cement removal, the system can be used on demand to acquire a few calibrated X-ray images. After a semi-automatic segmentation and 3-D reconstruction of the cement with a deformable model, the system guides the surgeon through a free-hand navigated or robot-assisted cement removal. The experimental evaluation using plastic test implants cemented into anatomic specimen of human femoral bone has shown the potential of this method with a maximal error of 1.2 mm (0.5 mm RMS) for the distal cement based on just 4-5 multiplanar X-ray images. A first test of the complete system, comparing the 3-D-reconstruction with a computed tompgraphy data set, confirmed these results with a mean error about 1 mm.     

Gap acceptance and risk-taking by young and mature drivers, both sober and alcohol-intoxicated, in a simulated driving task

A single-blind randomized study was conducted on young (18–21 years, n = 16) and mature (25–35 years, n = 16) drivers to assess how age, combined with a modest dose of alcohol (0.7 g/kg for males and 0.6 g/kg for females), influenced performance on a driving simulator. The driving tasks included detecting the presence of a vehicle on the horizon as quickly as possible, estimating the point on the road that an approaching vehicle would have passed by the participants’ vehicle (time-to-collision) and overtaking another vehicle against a steady stream of oncoming traffic. The results of the vehicle detection task showed that detection times were significantly slower with maturity, alcohol consumption and lower approaching vehicle speeds (50 kph), particularly on curved sections of road. Approaching vehicle speed was also found to significantly influence time-to-collision (TTC) judgments, such that faster approach speeds led to less underestimated (and therefore riskier) judgments of TTC than slower speeds. In the overtaking task, mature participants demonstrated impaired discrimination skills with varying approaching vehicle speeds, while young participants recorded significantly slower speeds while overtaking a vehicle, thus increasing the time that they spent in the opposing lane. In conclusion, young and mature drivers demonstrated pivotal differences in behavior in this study. Young drivers showed a greater tendency to engage in risky driving, while experienced drivers appeared to be more susceptible to perceptual influences. Overall, alcohol consumption impaired a driver's ability to divide attention, but had little effect on decision-making processes.     

Nonlinear optical chromophores as nanoscale emitters for single-molecule spectroscopy

Fluorescence imaging of single molecules at room temperature is a powerful technique for studying complex condensed phase systems and revealing structure and dynamics hidden by ensemble measurements. Successful single-molecule spectroscopic experiments rely upon strong emitters that can be detected at the level of individual copies above the relevant background signals. This Account discusses a class of nonlinear optical chromophores that not only are well-suited for single-molecule imaging but also offer additional beneficial properties such as a significant ground-state dipole moment, moderate hyperpolarizability, and sensitivity to local environment. An overview of the photophysical properties of several members of this class of molecules as well as a mechanism to help understand the environmental sensitivity is presented. Some preliminary applications of the chromophores as single-molecule reporters in cellular and polymer systems are discussed, along with detection of the emitters by two-photon fluorescence.     

Construction of Recombinant Escherichia coli Catalysts which Simultaneously Express an (S)‐Oxynitrilase and Different Nitrilase Variants for the Synthesis of (S)‐Mandelic Acid and (S)‐Mandelic Amide from Benzaldehyde and Cyanide

Recombinant Escherichia coli strains were constructed which simultaneously expressed the genes encoding the (S)‐oxynitrilase from cassava (Manihot esculenta) together with the wild‐type or a mutant variant of the arylacetonitrilase from Pseudomonas fluorescens EBC191 in a single organism under the control of a rhamnose‐inducible promoter. The whole cell catalysts obtained converted benzaldehyde and potassium cyanide in aqueous media at pH 5.2 mainly to (S)‐mandelic acid and/or (S)‐mandelic amide and synthesized only low amounts of the corresponding (R)‐enantiomers. The conversion of benzaldehyde and potassium cyanide (KCN) by a whole‐cell catalyst simultaneously expressing the (S)‐oxynitrilase and the wild‐type nitrilase resulted in a ratio of (S)‐mandelic acid to (S)‐mandelic amide of about 4:3. This could be explained by the strong nitrile hydratase activity of the wild‐type nitrilase with (S)‐mandelonitrile as substrate. The relative proportion of (S)‐mandelic amide formed in this system was significantly increased by coexpressing the (S)‐oxynitrilase with a carboxy‐terminally truncated variant of the nitrilase. This whole‐cell catalyst converted benzaldehyde and KCN to mandelic amide and mandelic acid in a ratio of about 9:1. The ee of the (S)‐mandelic amide formed was calculated to be >95%.