3,492 research outputs found
Microstructure and mechanical properties of bulk yttria-partially-stabilized zirconia
A commercially available bulk 4.5 mole percent yttria-(Y2O3) partially stabilized zirconia (PSZ) was studied by light microscopy, X-ray analysis, microhardness measurement, and fracture toughness testing. The growth of the precipitates and the phase transformations were studied as a function of aging in air at 1500 C. Aging curves were constructed for both the as received and the solution annealed and quenched materials; the curves showed hardness peaks at 1397 and 1517 Kg/sq mm respectively. The rectangular plate shaped tetragonal precipitates were found to have a 110 habit plane. A total of twelve different types of tetragonal precipitates were found. Grinding of the Y2O3 PSZ into powder did not cause a significant amount of metastable tetragonal precipitates to transform into the monoclinc phase, thus indicating that transformation toughening is not a significant mechanism for the material
Wireless, in-vessel neutron monitor for initial core-loading of advanced breeder reactors
An experimental wireless, in-vessel neutron monitor was developed to measure the reactivity of an advanced breeder reactor as the core is loaded for the first time to preclude an accidental critically incident. The environment is liquid sodium at a temperature of approx. 220 C, with negligible gamma or neutron radiation. With ultrasonic transmission of neutron data, no fundamental limitation was observed after tests at 230 C for 2000 h. The neutron sensitivity was approx. 1 count/s-nv, and the potential data transmission rate was approx. 10,000 counts/s
Particle Survival and Polydispersity in Aggregation
We study the probability, , of a cluster to remain intact in
one-dimensional cluster-cluster aggregation when the cluster diffusion
coefficient scales with size as . exhibits a
stretched exponential decay for and the power-laws for
, and for . A random walk picture
explains the discontinuous and non-monotonic behavior of the exponent. The
decay of determines the polydispersity exponent, , which
describes the size distribution for small clusters. Surprisingly,
is a constant for .Comment: submitted to Europhysics Letter
Rehabilitation and Reintroduction of wild born orphan chimpanzee (Pan troglodytes) within the pongo and okokong islands of the douala-edea wildlife reserve, Littoral Region Cameroon
This study had as main objective to document on the reintroduction of chimpanzees in the Douala-Edea Wildlife Reserve which appears to be the first case of chimpanzee reintroduction in Cameroon. The study was carried out in the South East zone of the Douala-Edea Wildlife Reserve which holds a small chimpanzee sanctuary under the auspices of “Papaye France” association. Data was collected on the field using semi structured questionnaires, interviews and direct observations alongside a participatory action approach at the sanctuary. Data from discussion guide and questionnaires were descriptively analysed and discussed with respect to our objectives. There were 24 orphan chimpanzees all together present in the zone and being cared for by the association PAPAYE France. This association has released 16 chimpanzees on two Islands of the reserve, the first group made of 9 chimpanzees (6 males and 3 females) were released in 2008 on the Pongo Island and a second group made of 6 chimpanzees (4 males and 2 females) were released on the Okokong Island in 2010; one female was later introduced to this group early 2015. These chimpanzees were released after a rehabilitation process not in line with IUCN guidelines for reintroduction of great apes and not following any developed scientific approach or methodology. Despite this, the released chimps are faring well as new births have been recorded on either Islands, chimps feed, nest, movement and vocalize indicating there have gotten adapted to live on the Islands. It was also noted that the sizes of these islands may not maintain a viable, nutritionally self-sustaining population in the long run hence could better serve as a semi naturalistic sanctuary. It is necessary that the carrying capacities of the islands be determined while larger potential release sites be assessed and prepared for an eventual transfer/reintroduction of these apes in the future
Testing T Invariance in the Interaction of Slow Neutrons with Aligned Nuclei
The study of five-fold (P even, T odd) correlation in the interaction of slow
polarized neutrons with aligned nuclei is a possible way of testing the time
reversal invariance due to the expected enhancement of T violating effects in
compound resonances. Possible nuclear targets are discussed which can be
aligned both dynamically as well as by the "brute force" method at low
temperature. A statistical estimation is performed of the five-fold correlation
for low lying p wave compound resonances of the Sb, Sb and
I nuclei. It is shown that a significant improvement can be achieved
for the bound on the intensity of the fundamental parity conserving time
violating (PCTV) interaction.Comment: 22 pages, 5 figures, published versio
Microrheology with optical tweezers: data analysis
We present a data analysis procedure that provides the solution to a long-standing issue in microrheology studies, i.e. the evaluation of the fluids' linear viscoelastic properties from the analysis of a finite set of experimental data, describing (for instance) the time-dependent mean-square displacement of suspended probe particles experiencing Brownian fluctuations. We report, for the first time in the literature, the linear viscoelastic response of an optically trapped bead suspended in a Newtonian fluid, over the entire range of experimentally accessible frequencies. The general validity of the proposed method makes it transferable to the majority of microrheology and rheology techniques
Face-space: A unifying concept in face recognition research
The concept of a multidimensional psychological space, in which faces can be represented according to their perceived properties, is fundamental to the modern theorist in face processing. Yet the idea was not clearly expressed until 1991. The background that led to the development of face-space is explained, and its continuing influence on theories of face processing is discussed. Research that has explored the properties of the face-space and sought to understand caricature, including facial adaptation paradigms, is reviewed. Face-space as a theoretical framework for understanding the effect of ethnicity and the development of face recognition is evaluated. Finally, two applications of face-space in the forensic setting are discussed. From initially being presented as a model to explain distinctiveness, inversion, and the effect of ethnicity, face-space has become a central pillar in many aspects of face processing. It is currently being developed to help us understand adaptation effects with faces. While being in principle a simple concept, face-space has shaped, and continues to shape, our understanding of face perception
Diverse syntrophic partnerships from deep-sea methane vents revealed by direct cell capture and metagenomics
Microorganisms play a fundamental role in the cycling of nutrients and energy on our planet. A common strategy for many microorganisms mediating biogeochemical cycles in anoxic environments is syntrophy, frequently necessitating close spatial proximity between microbial partners. We are only now beginning to fully appreciate the diversity and pervasiveness of microbial partnerships in nature, the majority of which cannot be replicated in the laboratory. One notable example of such cooperation is the interspecies association between anaerobic methane oxidizing archaea (ANME) and sulfate-reducing bacteria. These consortia are globally distributed in the environment and provide a significant sink for methane by substantially reducing the export of this potent greenhouse gas into the atmosphere. The interdependence of these currently uncultured microbes renders them difficult to study, and our knowledge of their physiological capabilities in nature is limited. Here, we have developed a method to capture select microorganisms directly from the environment, using combined fluorescence in situ hybridization and immunomagnetic cell capture. We used this method to purify syntrophic anaerobic methane oxidizing ANME-2c archaea and physically associated microorganisms directly from deep-sea marine sediment. Metagenomics, PCR, and microscopy of these purified consortia revealed unexpected diversity of associated bacteria, including Betaproteobacteria and a second sulfate-reducing Deltaproteobacterial partner. The detection of nitrogenase genes within the metagenome and subsequent demonstration of 15N2 incorporation in the biomass of these methane-oxidizing consortia suggest a possible role in new nitrogen inputs by these syntrophic assemblages
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