9,302 research outputs found
Three water sites in upper mantle olivine and the role of titanium in the water weakening mechanism
Infrared spectroscopy on synthetic olivines has established that there are at least
four different mechanisms by which hydrogen is incorporated into the crystal structure.
Two mechanisms occur in the system MgO-SiO2-H2O associated with silicon and
magnesium vacancies, respectively. A third mechanism is associated with trivalent cation
substitution, commonly Fe3+ in natural olivine, while the fourth mechanism, which is
the one most prevalent in natural olivines from the spinel-peridotite facies of the Earth’s
upper mantle, is associated with Ti4+ [Berry et al., 2005]. Here first principles calculations
based on density functional theory are used to derive the structure and relative energies
of the two defects in the pure MgO-SiO2-H2O system, and possible hydrogen-bearing
and hydrogen-free point defects in Ti4+-doped forsterite. Calculated structures are used to
compare the predicted orientation of the O-H bonds with the experimentally determined
polarization. The energies are used to discuss how different regimes of chemical
environment, temperature (T), pressure (P), and both water content and water fugacity
( fH2O), impact on which of the different hydroxyl substitution mechanisms are
thermodynamically stable. We find that given the presence of Ti impurities, the most
stable mechanism involves the formation of silicon vacancies containing two protons
charge balanced by a Ti4+ cation occupying an adjacent octahedral site. This mechanism
leads to the water-mediated formation of silicon vacancies. As silicon is known to be the
most slowly diffusing species in olivine, this provides a credible explanation of the
observed water weakening effect in olivine
Towards an expanded model of litigation
Introduction: The call for contributions for this workshop describes the important new challenges for the legal search
community this domain brings. Rather than just understanding the challenges this domain poses in terms of
their technical properties, we would like to suggest that understanding these challenges as socio-technical
challenges will be important. That is, as well as calling for research on a technical level to address these
challenges we are also calling for work to understand the social practices of those involved in e-discovery
(ED) and related legal work. A particularly interesting feature of this field is that it is likely that search
technologies will (at least semi-)automate responsiveness review in the relatively near term and this will
change the way that the work is organised and done in many ways – offering new possibilities for new
ways of organising the work. As well as designing those technologies for automating responsiveness
review we need to be envisioning how the work will be done in the future, how these technologies will
impact the organisation of the case and so on. In this position paper we therefore outline the importance of
understanding the wider social context of ED when designing tools and technologies to support and change
the work. We would like to reinforce and expand on Conrad’s call for IR researchers to understand just
what ED entails [2], include the stages that come both before and after core retrieval activities.
The importance of considering the social aspects of work in the design of the technology has been
established for some time. Ushering in this ‘turn to the social,’ and focusing on interface design, Gentner
and Grudin [4] described how the GUI has already changed from an interface for engineers, representing
the engineering model of the machine to one that supported single ‘everyman’ users (based on ideas from
psychology). From then onwards the interface has evolved to support groups of users, taking into account
the social and organisational contexts of use. This has particular resonance for the design of ED
technologies: during ED in particular and the wider legal process there are often many lawyers involved –
reviewing documents, determining issues, etc. Even if the way that their work is organised currently is not
seen as collaborative in the traditional sense – with individual lawyers working on individual document sets
to review them - their work needs to be coordinated and it seems likely that their work could be enhanced
by, for example, knowledge of what their colleagues had found, how the case was shaping up, new key
terms and facts turned up and so on. Work is often modelled for the purposes of design using process
models, but this misses out on the richness and variety actually found when one examines how the work is
carried out [3]. Technologies which strictly enforce the process models can often hinder the work, or end
up being worked around as was the case with workflow systems since people interpret processes very
flexibly to get the work done ([1], [3]). Other studies in other fields have found similar problems when
systems are designed on for example cognitive models of how the work is done; they often do not take into
account the situated nature of the work and thus they can be very difficult to use [5]. We believe, like [2],
that a clear understanding of the social practices of ED is vital for the creation of high-quality, meaningful
tools and technologies. We furthermore propose that work practice studies, to be used in combination with
other methods, are a central part of getting the detailed understanding of the work practices central to
designing useful and intelligent tools. Work practice studies would involve ethnographies, consisting
primarily of observation, undertaken of practitioners engaging in the work of ED
Organ failure, outcomes and deprivation status among critically ill cirrhosis patients — a one-year cohort study
No abstract available
Tert-butyl benzoquinone: mechanism of biofilm eradication and potential for use as a topical antibiofilm agent
Objectives: Tert-butyl benzoquinone (TBBQ) is the oxidation product of tert-butyl hydroquinone (TBHQ), an antimicrobial food additive with >40 years of safe use. TBBQ displays potent activity against Staphylococcus aureus biofilms in vitro. Here, we report on studies to further explore the action of TBBQ on staphylococcal biofilms, and provide a preliminary preclinical assessment of its potential for use as a topical treatment for staphylococcal infections involving a biofilm component. Methods: The antibacterial properties of TBBQ were assessed against staphylococci growing in planktonic culture and as biofilms in the Calgary Biofilm Device. Established assays were employed to measure the effects of TBBQ on biofilm structure and bacterial membranes, and to assess resistance potential. A living skin equivalent was used to evaluate the effects of TBBQ on human skin. Results: TBBQ eradicated biofilms of S. aureus and other staphylococcal species at concentrations ≤64 mg/L. In contrast to other redox-active agents exhibiting activity against biofilms, TBBQ did not cause substantial destructuring of the biofilm matrix; instead, the antibiofilm activity of the compound was attributed to its ability to kill slow- and non-growing cells via membrane perturbation. TBBQ acted synergistically with gentamicin, did not damage a living skin equivalent following topical application, and exhibited low resistance potential. Conclusions: The ability of TBBQ to eradicate biofilms appears to result from its ability to kill bacteria regardless of growth state. Preliminary evaluation suggests that TBBQ represents a promising candidate for development as a topical antistaphylococcal biofilm agent
Las especies amenazadas son indicadoras de los puntos calientes de la regulación trófica en sentido descendente
Se ha considerado la introducción de mesopredadores y herbÃvoros extranjeros como el principal desencadenante de la extinción de mamÃferos australianos. Estudios recientes sugieren que los efectos devastadores de las especies invasoras quedan mitigados por los superpredadores. Por lo tanto, la supervivencia de muchas especies amenazadas puede depender de la presencia y funcionalidad ecológica de los grandes predadores. El superpredador australiano, el dingo (Canis lupus dingo) ha sido muy perseguido por todo el continente, y es extremadamente raro encontrar poblaciones de dingos que no estén sujetas a un control letal. En este estudio pronosticamos que la presencia de especies amenazadas señala los lugares donde las poblaciones de dingos están relativamente intactas, y que su ausencia puede indicar que los dingos son raros o que sus poblaciones están socialmente fracturadas. La comparación entre un lugar que alberga a un marsupial amenazado, el kowari o rata marsupial de cola de pincel (Dasyuroides byrnei), y un lugar vecino, de donde falta el kowari, es concordante con el patrón que sugerimos.
Palabras clave: Envenenamiento con 1080, Canis lupus dingo, Dasyuroides byrnei, Especie invasora, Control por predador, Superpredador.The introduction of alien mesopredators and herbivores has been implicated as the main driver of mammalian extinction in Australia. Recent studies suggest that the devastating effects of invasive species are mitigated by top–order predators. The survival of many threatened species may therefore depend on the presence and ecological functioning of large predators. Australia’s top predator, the dingo (Canis lupus dingo), has been intensively persecuted across the continent and it is extremely rare to find dingo populations that are not being subjected to lethal control. We predicted that the presence of threatened species point out places where dingo populations are relatively intact, and that their absence may indicate that dingoes are either rare or socially fractured. A comparison of a site which harbors a threatened marsupial, the kowari (Dasyuroides byrnei), and a neighboring site where the kowari is absent, offers support for this suggested pattern.
Key words: 1080 poison–baiting, Canis lupus dingo, Dasyuroides byrnei, Invasive species, Predator control, Top predator.Se ha considerado la introducción de mesopredadores y herbÃvoros extranjeros como el principal desencadenante de la extinción de mamÃferos australianos. Estudios recientes sugieren que los efectos devastadores de las especies invasoras quedan mitigados por los superpredadores. Por lo tanto, la supervivencia de muchas especies amenazadas puede depender de la presencia y funcionalidad ecológica de los grandes predadores. El superpredador australiano, el dingo (Canis lupus dingo) ha sido muy perseguido por todo el continente, y es extremadamente raro encontrar poblaciones de dingos que no estén sujetas a un control letal. En este estudio pronosticamos que la presencia de especies amenazadas señala los lugares donde las poblaciones de dingos están relativamente intactas, y que su ausencia puede indicar que los dingos son raros o que sus poblaciones están socialmente fracturadas. La comparación entre un lugar que alberga a un marsupial amenazado, el kowari o rata marsupial de cola de pincel (Dasyuroides byrnei), y un lugar vecino, de donde falta el kowari, es concordante con el patrón que sugerimos.
Palabras clave: Envenenamiento con 1080, Canis lupus dingo, Dasyuroides byrnei, Especie invasora, Control por predador, Superpredador
Threatened species indicate hot-spots of top-down regulation
The introduction of alien mesopredators and herbivores has been implicated as the main driver of mammalian extinction in Australia. Recent studies suggest that the devastating effects of invasive species are mitigated by top-order predators. The survival of many threatened species may therefore depend on the presence and ecological functioning of large predators. Australia’s top predator, the dingo (Canis lupus dingo), has been intensively persecuted across the continent and it is extremely rare to find dingo populations that are not being subjected to lethal control. We predicted that the presence of threatened species point out places where dingo populations are relatively intact, and that their absence may indicate that dingoes are either rare or socially fractured. A comparison of a site which harbors a threatened marsupial, the kowari (Dasyuroides byrnei), and a neighboring site where the kowari is absent, offers support for this suggested pattern
Necrosis of a Guinea Pig Stomach after Contact with Povidone-Iodine: a Case Report
Rodents are the most frequently used animals in surgical experimentation. It is estimated that guinea pigs
in particular are the third most commonly used species in this context. To disinfect guinea pigs’ skin, either
alcohol or surgical iodine are most often used. In the context of an animal research project, a Nissen operation
was performed in an adult male guinea pig. Because of accidental contamination of the operative field, a 10%
povidone-iodine cutaneous solution was applied to the serosa of the anterior wall of the stomach and to the
gastric fundus. The guinea pig died 12 hours after surgery due to an acute necrotizing hemorrhagic gastritis.
Although there have been a few reports of povidone-iodine toxicity in the guinea pig, as far as the authors
could determine, this is the first time that such a serious abdominal complication is reported. The authors
believe that the possibility of a similar event should be taken into consideration when planning, executing and
interpreting experiments in the guinea pig
Active cloaking of finite defects for flexural waves in elastic plates
We present a new method to create an active cloak for a rigid inclusion in a
thin plate, and analyse flexural waves within such a plate governed by the
Kirchhoff plate equation. We consider scattering of both a plane wave and a
cylindrical wave by a single clamped inclusion of circular shape. In order to
cloak the inclusion, we place control sources at small distances from the
scatterer and choose their intensities to eliminate propagating orders of the
scattered wave, thus reconstructing the respective incident wave. We then vary
the number and position of the control sources to obtain the most effective
configuration for cloaking the circular inclusion. Finally, we successfully
cloak an arbitrarily shaped scatterer in a thin plate by deriving a
semi-analytical, asymptotic algorithm.Comment: 19 pages, 14 figures, 1 tabl
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