In-situ high-voltage electron microscopy observations of reactions between molten Zn and Fe

Reactions between molten Zn and Fe have been observed directly by means of an in-situ heating experiment in a high-voltage electron microscope. In order to suppress evaporation of Zn during the in-situ heating experiment the specimen was coated with a plasma-polymerized hydrocarbon film. Mechanisms for the formation of Fe-Zn intermetallic compounds are discussed and it is concluded that all the models proposed so far are of doubtful validity.     

Rarely Pure and Never Simple: Tensions in the Theory of Truth

Section 1 discerns ambiguity in the word “truth”, observing that the term is used most naturally in reference to truth-bearers rather than truth-makers. Focusing on truths-as-truth-bearers, then, it would appear that alethic realism conflicts with metaphysical realism as naturalistically construed. Section 2 discerns ambiguity in the purporting of truth (as in assertion), conjecturing that all expressions, not just those found in traditionally recognized opaque contexts, can be read intensionally (as well, perhaps, as extensionally). For instance, we would not generally want to say that “The Matterhorn is 4,500 m high” expresses the same truth as “The Matterhorn is 14763.7795276 feet high” (or that it is true in the same range of utterance contexts), even though the two are extensionally equivalent. The reason is that they express different intensions.     

Facilitation of corticospinal excitability during motor imagery of wrist movement with visual or quantitative inspection of EMG activity

The present study investigated facilitation of corticospinal excitability during motor imagery of wrist movement with visual or quantitative inspection of background electromyographic (EMG) activity. Ten healthy participants imagined wrist extension from a first-person perspective in response to a start cue. Transcranial magnetic stimulation was delivered to the motor cortex 2 sec. after the start cue. EMG signals were recorded from the extensor carpi radialis muscle. Trials with background EMG activity were discarded based on visual inspection. Both motor-evoked potential (MEP) and background EMG amplitudes increased during motor imagery. The amount of increase in MEP amplitude was positively correlated with the amount of increase in background EMG amplitude during motor imagery. The statistically significant increase in MEP amplitude during motor imagery disappeared when the effect of muscle activity was statistically eliminated or after trials with background EMG activity were discarded based on strict quantitative criteria. Facilitation of corticospinal excitability during motor imagery of wrist movement depends partially on muscle activity. Discarding background EMG activity during motor imagery based on visual inspection is not sufficient to equalize background EMG amplitude between resting and motor imagery. Discarding trials with background EMG activity through strict quantitative criteria is useful to equalize background EMG amplitude between at rest and during motor imagery.     

Relative distance cues contribute to scaling depth from motion parallax

The visual system scales motion parallax signals with information about absolute distance (M. E. Ono, Rivest, & H. Ono, 1986). The present study was designed to determine whether relative distance cues, which intrinsically provide information about relative distance, contribute to this scaling. In two experiments, two test stimuli, containing an equal extent of motion parallax, were presented simultaneously at a fixed viewing distance. The relative distance cues of dynamic occlusion and motion parallax in the areas surrounding the test stimuli (background motion parallax) and/or relative size were manipulated. The observers reported which of the two parallactic test stimuli appeared to have greater depth, and which appeared to be more distant. The results showed that the test stimulus specified, by the relative distance cues, as being more distant was perceived as having more depth and as being more distant. This indicates that relative distance cues contribute to scaling depth from motion parallax by modifying the information about the absolute distance of objects.     

Should I use a computer-assisted career guidance system? It depends on where your career decision-making difficulties lie

The present study examined the pattern of career decision-making difficulties encountered by 417 young adults who used one or more of the computer-assisted career guidance systems (CACGSs) available at one of the Israeli Veteran Administration's counselling centres, and assessed the effectiveness of these CACGSs in reducing their career decision-making difficulties. Career decision-making difficulties were found to be highest for individuals who were prior to the pre-screening stage of the career decision-making process and lowest for those who were at the choice stage. The reduction in difficulties after using the CACGSs was statistically significant in seven of the 10 difficulty categories examined: an especially marked reduction was found for difficulties related to lack of information. No such reduction was observed for difficulties related to external conflicts. Participants' perception of having been assisted through the dialogue with the CACGSs was highest for individuals who used all three systems, and lowest for those who accessed only one of the three CACGSs.     

Transmission electron microscopy of dislocations in SrTiO3

Dislocations have been introduced in SrTiO₃ by Vickers indentation at room temperature and analysed by transmission electron microscopy. The slip systems in SrTiO₃ were identified as ?110?-{110}. ?110? dislocations are dissociated into two partial dislocations. The stacking-fault energy γSF was determined to be 136 ± 15 mJm^-2.     

On the dislocation mechanism of amorphization of Si by indentation

The formation of an amorphous phase underneath a Vickers indentation produced on a Si(001) surface at room temperature has been observed by cross-sectional transmission electron microscopy. Two types of location are observed for the amorphous phase. One is formed just underneath the image of the indentation and the other is parallel to the slip planes of Si. It is concluded that the latter type, at least, is formed as a result of activation of dislocations which is induced by an external shear stress combined with a hydrostatic pressure.     

Motion parallax driven by head movements: conditions for visual stability, perceived depth, and perceived concomitant motion

Yoking the movement of the stimulus on the screen to the movement of the head, we examined visual stability and depth perception as a function of head-movement velocity and parallax. In experiment 1, for different head velocities, observers adjusted the parallax to find (a) the depth threshold and (b) the concomitant-motion threshold. Between these thresholds, depth was seen with no perceived motion. In experiment 2, for different head velocities, observers adjusted the parallax to produce the same perceived depth. A slower head movement required a greater parallax to produce the same perceived depth as faster head movements. In experiment 3, observers reported the perceived depth for different parallax magnitudes. Perceived depth covaried with smaller parallax without motion perception, but began to decrease with larger parallax and concomitant motion was seen. Only motion was seen with the larger parallax.     

High-resolution in situ electron microscopy of a silicon surface modification by molten aluminium at high temperatures

High-resolution in situ heating experiments in a transmission electron microscope have been applied to a study of the surface modification of Si by molten Al in a vacuum of 1 10^-5 Pa. Transformation from an atomically rough to an atomically flat surface was induced by wetting of molten Al atoms. Si {110}, {112}, {115} and {773} surfaces show sawtooth-like structures composed of nanofacets. It is concluded that molten Al atoms remove a native amorphous oxide layer which existed on the original Si surface, making the surface 'clean' even in a non-ultra-high vacuum such as 10^-5Pa.