Formation and breakdown of a protective layer of chromium sesquioxide on L-605 alloy at 1100° C

The formation and breakdown of a protective layer of Cr₂O₃ on L-605 during oxidation at 1100° C was investigated. The effects of surface deformation, pressure, and water vapor on the breakdown time were evaluated. It was found that increasing surface deformation, increased the time to breakdown. Decreasing pressure below 1 atm to 0.13 N/m² increased time of breakdown as did decreasing water content from 25,000 to 2.5 ppm. By metallographic and microprobe examinations of samples during breakdown a model was deduced. Surface deformation promotes Cr₂O₃ formation, while increasing pressure and moisture increases the volatility of Cr₂O₃. Thus, the Cr₂O₃ grows for a time determined by these three factors. At the end of this time the growth stresses cause the oxide to crack, exposing a chromium-depleted metal surface to the oxidizing gas. The resultant rapid oxidation of this surface lifts the remaining Cr₂O₃, exposing more depleted metal. When the depletion zone is consumed and a very thick oxide has formed, the rate of oxidation slows and no further disruption is noted.     

Thermodynamic review and calculations—alkali-metal oxide systems with nuclear fuels, fission products, and structural materials

This paper considers the phase equilibria of alkali metal oxides and their combinations with other oxides relevant to nuclear fuels, fission products, and structural materials. The other oxides include those of the lanthanides, the actinides, iron, nickel, aluminum, silicon, as well as those of periodic table groups IIA, IVB, VB, VIB, and VIA. The alkali metal halides, chalcogenides, and hydroxides are also included. Techniques are developed to permit calculation of phase equilibria and Ellingham diagrams in ternary and higher-order systems. These techniques include estimation of previously unknown 298.15 K values of the enthalpies of formation and the entropies of many compounds.     

Population-based incremental interactive concept learning for image retrieval by stochastic string segmentations

We propose a method for concept-based medical image retrieval that is a superset of existing semantic-based image retrieval methods. We conceive of a concept as an incremental and interactive formalization of the user's conception of an object in an image. The premise is that such a concept is closely related to a user's specific preferences and subjectivity and, thus, allows to deal with the complexity and content-dependency of medical image content. We describe an object in terms of multiple continuous boundary features and represent an object concept by the stochastic characteristics of an object population. A population-based incrementally learning technique, in combination with relevance feedback, is then used for concept customization. The user determines the speed and direction of concept customization using a single parameter that defines the degree of exploration and exploitation of the search space. Images are retrieved from a database in a limited number of steps based upon the customized concept. To demonstrate our method we have performed concept-based image retrieval on a database of 292 digitized X-ray images of cervical vertebrae with a variety of abnormalities. The results show that our method produces precise and accurate results when doing a direct search. In an open-ended search our method efficiently and effectively explores the search space.     

An inquiry of the opinions of the French and Belgian populations as regards risk

IRSN (France) and SCK-CEN (Belgium), two institutes of research and expertise in radiation protection and nuclear safety, simultaneously organised a very similar public opinion survey in their respective countries in November 2002. The study explores subjects such as: major people's concerns, perception of environmental risks, perception of risks in general, the role of experts in decision making, opinions on nuclear matters and aspects of nuclear emergency preparedness. In each country, more than 1000 citizens representing the general public have been consulted in face-to-face interviews. The field work has been performed by professional companies (BVA in France and Research International in Belgium). The paper shows that industrial and technological risks are not perceived as one of the major public concerns, although many other risks, of different nature are considered to be high. The actions of the authorities to provide protection against the consequences of many risks or disasters are not considered to be sufficient, and many respondents claim not to believe the information they receive. There exists a large difference between the opinion of French and Belgian public, and within the different language groups in Belgium, with regard to who should be in charge of the control of the hazardous industries. Many of the "actors" within the nuclear industry are not known by the respondents. The perception of the technical competence or the truth being told shows large variations between the main actors (such as members of the nuclear industry, the government or the media). Majorities within the population believe that a disaster as serious as the Chernobyl one can happen in their country and that in case of a nuclear accident, the authorities would not be capable to protect the population adequately.     

Design and implementation of software for assembly and browsing of 3D brain atlases

Visualization software for three dimensional digital brain atlases present many challenges in design and implementation. These challenges include the design of an effective human interface, management of large data sets, display speed when slicing the data set for viewing/browsing, and the display of delineated volumes of interest (VOI). We present a software design, implementation and storage architecture that addresses these issues, allowing the user to navigate through a reconstructed volume quickly and smoothly, with an easy-to-use human interface. The software (macostat, for use with Macintosh OS) allows the user to rapidly display slices of the digital atlas at any arbitrary slicing angle, complete with delineated VOIs. The VOIs can be assigned colors of the user's choosing. The entire atlas, or selected portions, may be resliced with slices stored as individual image files, complete with delineations. These delineations may be transferred to corresponding sections of experimental materials using our analysis program (brain). The software may be obtained from the laboratory's web site: http://www.neuroterrain.org     

An unslotted multichannel channel‐access protocol for distributed direct‐sequence networks

A multichannel reservation-based channel-access protocol is investigated in this paper. The available system bandwidth is divided into distinct frequency channels. Under the protocol, one channel (the control channel) is used to exchange reservation messages and the remaining channels (the traffic channels) are used for information-bearing traffic. The performance of this scheme is compared to that of a single-channel reservation-based protocol. A simple contention-based slotted-Aloha protocol is also considered. Performance results take into account the effects of multiple-access interference on acquisition and packet errors. Results show that the reservation-based approach is advantageous under conditions of high traffic. In addition, a pacing mechanism that mitigates multiple-access interference and promotes fairness is described, and results are presented that demonstrate its effectiveness. This revised version was published online in June 2006 with corrections to the Cover Date.     

Spectroelectrochemical sensing based on attenuated total internal reflectance stripping voltammetry. 2. Determination of mercury and lead

Detection of lead and mercury by attenuated total internal reflectance spectroscopy coupled to stripping voltammetry is demonstrated. Changes in attenuation of light passing through an indium tin oxide optically transparent electrode (ITO-OTE) accompany the electrodeposition and stripping of lead and mercury on the electrode surface. The change in absorbance during stripping of electrodeposited metal constitutes the analytical response that enables detection over a range of 2.5 x 10(-7)-5 x 10(-5) and 5 x 10(-8)-5 x 10(-5) M for mercury and lead, respectively. The spectroelectrochemical responses of mercury and lead on the ITO surface are characterized and optimized with respect to solution conditions, the potential excitation signals used for deposition and stripping, and wavelength for detection. The deposited metals were examined by environmental scanning electron miscroscopy, and the electrodeposition pattern of lead and mercury was found to influence the optical response.     

Vicarious experience and partial reinforcement.

This study attempts to determine the conditions under which one can benefit from others' experience and to offer an explanation in terms of S-R theory using a mediational response mechanism. The apparatus was a modified slot machine which pays off on particular plays determined in advance by E. Ss were 200 university students divided into 5 pairs of groups, with one group in each pair having a 25% reward acquisition series and the other a 100% acquisition series. 5 different conditions of participation were used. The results showed that vicarious learning did take place as long as S actually participated in the winning during acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological and subjective effects of Zen meditation and demand characteristics.

Undergraduates studied a Zen meditation exercise under 3 demand conditions: deactivation (modeling and suggesting relaxation outcome), neutral (no specific outcome), and activation (arousal outcome). Results show that Zen meditation produces small physiological changes in naive, unpracticed Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)