Molecular dynamics simulations of collision cascades in FeCrHe

Radiation damage due to 1 and 5 keV collision cascades in Fe₉₀Cr₁₀ in the presence of 0.1%, 0.5% and 1.0% He defects, relevant for fusion reactor steels, has been studied using molecular dynamics simulations. We show that with 0.1% interstitial He the effect on the damage production in the FeCr matrix is minor, while with 1.0% He, the number of Frenkel pairs is significantly increased in comparison to pure FeCr. The positions of the He interstitials and clusters depend on the Cr atoms and the amount of He inside the cascade region is increased by about 30% due to the cascade. With substitutional He less damage is formed in the FeCr matrix due to cascades.     

Relating variations in water saturation of a sandstone sample to pore geometry by neutron tomography and image analysis of thin sections

Neutron tomography experiments were undertaken on a quartz arenite sample in order to determine saturation variations in the sample after the initially water-saturated sample was subjected to air flushing. The experiments were carried out in order to study the applicability of the neutron tomography facility at the Paul Scherrer Institute, Switzerland, for imaging fluid distribution in porous rocks. The variation in water saturation was related to the pore geometry of the sample as investigated by petrographic image analysis of thin sections. A variation in fluid saturation was successfully imaged. The spatial saturation distribution noted from the neutron tomography corresponds well with variations in pore geometry, indicating that the water was preferentially flushed from the coarse-grained laminae. Résumé. Des mesures tomographiques neutroniques ont été réalisées sur un échantillon de grès quartzeux dans le but d'y déterminer des variations de degré de saturation après que l'échantillon initialement saturé en eau ait été soumis à un drainage forcé. Les expériences ont été conduites afin d'étudier la capacité d'un dispositif de tomographie neutronique de l'Institut Paul Scheerer (Suisse) à donner une image de la répartition des fluides dans les roches poreuses. Des variations de degré de saturation ont été identifiées avec succès, variations en relation avec la géométrie des pores de l'échantillon comme cela a pu être identifié par des techniques d'analyse d'image de lames minces. La répartition spatiale du degré de saturation observée à partir de la tomographie neutronique correspond bien à des variations dans la géométrie des pores, indiquant que l'eau avait été préférentiellement chassée des lamines constituées de gros grains. Electronic Publication     

Evaluation of Chinese projects and comparison with Norwegian projects

Project work in developing and emerging economies is complicated and unpredictable. It would be of great help to equip project managers with an easily applicable tool to assess whether the project is on the right track or not. A Project Evaluation Scheme (PEVS) has earlier been used on Norwegian projects. Data from 89 Chinese projects has been collected using the scheme. This article analyses the Chinese data and compares them to the Norwegian findings. The Chinese projects are scoring higher in all areas investigated, except on informal contacts. Particularly high were goal setting, overall planning and control execution. The Chinese projects achieve their goals and are regarded as a success by all participants. They should improve in project closeout work. The article discusses the reasons for differences between Chinese and Norwegian projects, ranging from differences in perception regarding the questionnaire, to the possibility that Chinese projects in fact are better. The qualities of activity execution are found to be the most important factor in predicting project success. PEVS is proven to be applicable to Chinese projects, yet further customisation is needed.     

Kairomones and their use for management of entomophagous insects: II. Mechanisms causing increase in rate of parasitization byTrichogramma spp.

When the effect of the kairomone, tricosane, on parasitization byTrichogramma achaeae Nagaraja and Nagarkatti of eggs ofHeliothis zea (Boddie) was studied in petri dish tests, the greatest percentage parasitization ( = 64%) was obtained if the entire filter paper was treated. Treatment of smaller areas (about the eggs) resulted in decreased parasitism. In the greenhouse, highest parasitization ( = 71%) byT. pretiosum (Riley) ofH. zea eggs placed on pea seedlings grown in pie pans was obtained if the whole pan was treated; lowest parasitism ( = 29%) occurred when the pans were untreated. Parasitization was intermediate ( = 52%) in other pans treated only at selected spots. Dissections ofH. zea eggs collected from kairomonetreated and untreated field plots revealed that eggs ofTrichogramma spp. were more efficiently distributed (less superparasitism) among host eggs in treated plots. These kairomones increase parasitization ofTrichogramma spp. by releasing and continuously reinforcing an intensified searching behavior rather than by attracting and guiding the parasite directly to the host.Hymenoptera: Trichogrammatidae.In cooperation with the University of Georgia College of Agriculture Experiment Station, Coastal Plain Station, Tifton, Georgia.Mention of a proprietary product in this paper does not constitute an endorsement of this product by the USDA.     

Kairomones and their use for management of entomophagous insects: X. Laboratory studies on manipulation of host-finding behavior ofTrichogramma pretiosum riley1 with a kairomone extracted fromHeliothis zea (boddie) moth scales

The behavioral response ofTrichogramma pretiosum Riley females to the kairomone found inHeliothis zea (Boddie) moth scales is examined.Hymenoptera: Trichogrammatidae.In cooperation with the University of Georgia College of Agriculture Experiment Stations, Coastal Plain Station, Tifton, Georgia 31793.Mention of a proprietary product in this paper does not constitute an endorsement of this product by the USDA.The authors would like to acknowledge the excellent technical assistance of Mrs. Marcella Latham.     

A molecular dynamics study of the clustering of implanted potassium in multiwalled carbon nanotubes

We have studied the low energy irradiation of carbon nanotubes (CNT) with K ions using classical molecular dynamics simulations with analytical potentials. The studied CNTs had diameters of about 0.5–1.2 nm and single or multiple walls. The average penetration depth and probabilities to introduce an impurity atom into CNT were studied with simulations on irradiating the CNT with single K ion. The number of potassium clusters, their average sizes and the damage produced into the CNT due to the irradiation were studied using multiple K ion irradiations. We found that the K ions are mobile in CNTs right after the implantation event and that they cluster together. For CNTs with 1–3 coaxial tubes, the highest ratio of K atoms in clusters per total number of K ions was obtained by using an irradiation energy of about 100 eV. Also the least damage per K ion was found to be produced into the CNT with this energy when those energies high enough for the ion to penetrate the outermost wall of the CNT were considered.     

Application of non-linear optical second harmonic generation and X-ray absorption and spectroscopies to defect related properties of Hf silicate and Hf Si oxynitride gate dielectrics

Three different Hf oxide based dielectrics have emerged as viable candidates for applications in advanced ULSI devices. This article focuses on two of these: (i) phase separated Hf silicates with (i) 70–85% nano-crystalline HfO₂ with a nano-grain size <2 nm, and 15–30% ～2 nm non-crystalline SiO₂ inclusions, and (ii) Hf Si oxynitride alloys, the most promising of which has a composition, (HfO₂)_0.3(SiO₂)_0.3(Si₃N₄)_0.4 designated as 3/3/4 Hf SiON. X-ray absorption spectroscopy has been applied to identification of defect associated with vacancy structures in phase separated silicates, and network disruption defects in the Hf Si oxynitrides. Optical second harmonic generation is introduced in this article for the first time as a non-invasive approach for detecting macroscopic strain, that is shown to be absent in these low defect density dielectrics, the phase separated Hf silicates, and Hf Si oxynitrides, but present in HfO₂ films, and Hf silicates with lower HfO₂ content, e.g., the 40% HfO₂ film of this article.