Experimental evidence for the origin of two kinds of inclusions in diamonds from the deep mantle.

Abstract The conditions of origin for the type III inclusions in diamonds from Brazil [Hutchison, Thesis, 1997] and the NaPxÊ n inclusion from China [Wang and Sueno, Miner. J. 18 (1996) 9^16] were experimentally determined using a splitsphere anvil apparatus (USSA-2000). The type III inclusions formed at a minimum pressure and temperature of 25 GPa and 2000³C, while the origin of the NaPx^En inclusion was close to 23 GPa and 1900³C. Both determinations suggest that the temperature at the corresponding depths is about 300³C higher than predicted by most geotherms for a convecting mantle without a thermal boundary layer at 660 km. Both kinds of inclusions required rapid, single-stage transport by carbonate melt to the Earth's surface, which is consistent with the depths of origin for this melt greater than 660 km. The unusual composition of the NaPx^En inclusion is the result of metasomatism by carbonate melt enriched in Na, K and Mg, and depleted in Si and Al. Since this melt is not kimberlitic in composition, exchange of material between the melt and the mantle was necessary for the melt to become kimberlitic by the time it reached the surface. The resulting metasomatism taking place over a long period of time could cause major changes in the mineral and chemical composition and the structure of the Earth's mantle, and thus play an important role in its evolution.

Fe-rich ferropericlase and magnesiow\ufcstite inclusions reflecting diamond formation rather than ambient mantle

At the core of many Earth-scale processes is the question of what the deep mantle is made of. The only direct samples from such extreme depths are diamonds and their inclusions. It is commonly assumed that these inclusions reflect ambient mantle or are syngenetic with diamond, but these assumptions are rarely tested. We have studied inclusion\u2013host growth relationships in two potentially superdeep diamonds from Juina (Brazil) containing nine inclusions of Fe-rich (XFe 480.33 to 650.64) ferropericlase-magnesiow\ufcstite (FM) by X-ray diffractometry, X-ray tomography, cathodoluminescence, electron backscatter diffraction, and electron microprobe analysis. The inclusions share a common [112] zone axis with their diamonds and have their major crystallographic axes within 3\ub0\u20138\ub0 of those of their hosts. This suggests a specific crystallographic orientation relationship (COR) resulting from interfacial energy minimization, disturbed by minor post-entrapment rotation around [112] due to plastic deformation. The observed COR and the relationships between inclusions and diamond growth zones imply that FM nucleated during the growth history of the diamond. Therefore, these inclusions may not provide direct information on the ambient mantle prior to diamond formation. Consequently, a \u201cnon-pyrolitic\u201d composition of the lower mantle is not required to explain the occurrence of Fe-rich FM inclusions in diamonds. By identifying examples of mineral inclusions that reflect the local environment of diamond formation and not ambient mantle, we provide both a cautionary tale and a means to test diamond-inclusion time relationships for proper application of inclusion studies to whole-mantle questions

Crystallographic relationships between diamond and its inclusions

The study of the crystallographic orientations of minerals included in diamonds can provide an insight into the mechanisms of their incorporation and the timing of their formation relative to the host diamond. The reported occurrence of non-trivial orientations for some minerals in some diamonds, suggesting an epitactic relationship, has long been considered to reflect contemporaneous growth of the diamond and the inclusion (= syngenesis). Correct interpretation of such orientations requires (i) a statistically significant data set, i.e. crystallographic data for single and multiple inclusions in a large number of diamonds, and (ii) a robust data-processing method, capable of removing ambiguities derived from the high symmetry of the diamond and the inclusion. We have developed software which performs such processing, starting from crystallographic orientation matrixes obtained by X-ray diffractometry. Preliminary studies indicate a wide variety of trends in the orientations of different inclusion phases in diamonds. In contrast to previous claims, olivine inclusions in lithospheric diamonds from Udachnaya do not show any preferred orientations with respect to their diamond hosts, but multiple inclusions in a single diamond often show very similar orientations within a few degrees (Nestola et al. 2014). Chromite (spinel) inclusions exhibit a strong tendency for a single (111) plane of each inclusion to be parallel to a (111) plane of their diamond host, but without any statistically significant orientation of the crystallographic axes a, b, and c. By contrast, 7 inclusions of ferropericlase studied in 2 different super deep diamonds (four inclusions in one diamond and three inclusions in the second diamond) from Brazil all exhibit the same orientation with their axes practically coincident with those of diamonds regardless of the position and the shape of the inclusions. The implications of these observations for the mechanisms of diamond growth will be explored

AORTIC DISSECTION IN THE ELDERLY: COMPARING SEPTUAGENARIANS AND OCTOGENARIANS

none15siopenJabara, Justin; Peterson, Mark; Trimarchi, Santi; Myrmel, Truls; Reece, T. Brett; Bossone, Eduardo; Hutchison, Stuart; Gilon, Dan; Appoo, Jehangir; Di Eusanio, Marco; Montgomery, Daniel; Isselbacher, Eric; Nienaber, Christoph; Eagle, Kim; Patel, HimanshuJabara, Justin; Peterson, Mark; Trimarchi, Santi; Myrmel, Truls; Reece, T. Brett; Bossone, Eduardo; Hutchison, Stuart; Gilon, Dan; Appoo, Jehangir; Di Eusanio, Marco; Montgomery, Daniel; Isselbacher, Eric; Nienaber, Christoph; Eagle, Kim; Patel, Himansh

Serratamolide is a hemolytic factor produced by Serratia marcescens

Serratia marcescens is a common contaminant of contact lens cases and lenses. Hemolytic factors of S. marcescens contribute to the virulence of this opportunistic bacterial pathogen. We took advantage of an observed hyper-hemolytic phenotype of crp mutants to investigate mechanisms of hemolysis. A genetic screen revealed that swrW is necessary for the hyper-hemolysis phenotype of crp mutants. The swrW gene is required for biosynthesis of the biosurfactant serratamolide, previously shown to be a broad-spectrum antibiotic and to contribute to swarming motility. Multicopy expression of swrW or mutation of the hexS transcription factor gene, a known inhibitor of swrW expression, led to an increase in hemolysis. Surfactant zones and expression from an swrW-transcriptional reporter were elevated in a crp mutant compared to the wild type. Purified serratamolide was hemolytic to sheep and murine red blood cells and cytotoxic to human airway and corneal limbal epithelial cells in vitro. The swrW gene was found in the majority of contact lens isolates tested. Genetic and biochemical analysis implicate the biosurfactant serratamolide as a hemolysin. This novel hemolysin may contribute to irritation and infections associated with contact lens use. © 2012 Shanks et al

Identification of gold nanoparticle-resistant mutants of Saccharomyces cerevisiae suggests a role for respiratory metabolism in mediating toxicity

Positively-charged gold nanoparticles (0.8-nm core diameter) reduced yeast survival, but not growth, at a concentration of 10 to 100 μg/ml. Among 17 resistant deletion mutants isolated in a genome-wide screen, highly significant enrichment was observed for respiration-deficient mutants lacking genes encoding proteins associated with the mitochondrion

Using a Stick Does Not Necessarily Alter Judged Distances or Reachability

Background It has been reported that participants judge an object to be closer after a stick has been used to touch it than after touching it with the hand. In this study we try to find out why this is so. Methodology We showed six participants a cylindrical object on a table. On separate trials (randomly intermixed) participants either estimated verbally how far the object is from their body or they touched a remembered location. Touching was done either with the hand or with a stick (in separate blocks). In three different sessions, participants touched either the object location or the location halfway to the object location. Verbal judgments were given either in centimeters or in terms of whether the object would be reachable with the hand. No differences in verbal distance judgments or touching responses were found between the blocks in which the stick or the hand was used. Conclusion Instead of finding out why the judged distance changes when using a tool, we found that using a stick does not necessarily alter judged distances or judgments about the reachability of objects