The weathering of micrometeorites from the Transantarctic Mountains

Micrometeorites are cosmic dust particles recovered from the Earth's surface that dominate the influx of extraterrestrial material accreting to our planet. This paper provides the first in-depth study of the weathering of micrometeorites within the Antarctic environment that will allow primary and secondary features to be distinguished. It is based on the analysis of 366 particles from Larkman Nunatak and 25 from the Transantarctic Mountain collection. Several important morphological categories of weathering effects were identified: (1) irregular and faceted cavities, (2) surface etch pits, (3) infilled cavities, (4) replaced silicate phases, and (5) hydrated and replaced metal. These features indicate that congruent dissolution of silicate phases, in particular olivine, is important in generating new pore space within particles. Comparison of the preservation of glass and olivine also indicates preferential dissolution of olivine by acidic solutions during low temperature aqueous alteration. Precipitation of new hydrous phases within cavities, in particular ferrihydrite and jarosite, results in pseudomorph textures within heavily altered particles. Glass, in contrast, is altered to palagonite gels and shows a sequential replacement indicative of varying water to rock ratios. Metal is variably replaced by Fe-oxyhydroxides and results in decreases in Ni/Fe ratio. In contrast, sulphides within metal are largely preserved. Magnetite, an essential component of micrometeorites formed during atmospheric entry, is least altered by interaction with the terrestrial environment. The extent of weathering in the studied micrometeorites is sensitive to differences in their primary mineralogy and varies significantly with particle type. Despite these differences, we propose a weathering scale for micrometeorites based on both their degree of terrestrial alteration and the level of encrustation by secondary phases. The compositions and textures of weathering products, however, suggest open system behaviour and variable water to rock ratios that imply climatic variation over the lifetime of the micrometeorite deposits

Global terrestrial distribution of penguins (Spheniscidae) and their conservation by protected areas

Establishing protected areas (PAs) ranks among the top priority actions to mitigate the global scale of modern biodiversity declines. However, the distribution of biodiversity is spatially asymmetric among regions and lineages, and the extent to which PAs offer effective protection for species and ecosystems remains uncertain. Penguins, regarded as prime bioindicator birds of the ecological health of their terrestrial and marine habitats, represent priority targets for such quantitative assessments. Of the world’s 18 penguin species, eleven are undergoing population declines, for which ten are classified as ‘Vulnerable’ or ‘Endangered’. Here, we employ a global-scale dataset to quantify the extent to which their terrestrial breeding areas are currently protected by PAs. Using quantitative methods for spatial ecology, we compare the global distribution of penguin colonies, including range and population size analyses, with the distribution of terrestrial PAs classified by the International Union for Conservation of Nature, and generate hotspot and endemism maps worldwide. Our assessment quantitatively reveals < 40% of the terrestrial range of eleven penguin species is currently protected, and that range size is the significant factor in determining PA protection. We also show that there are seven global hotspots of penguin biodiversity where four or five penguin species breed. We suggest that future penguin conservation initiatives should be implemented based on more comprehensive, quantitative assessments of the multi-dimensional interactions between areas and species to further the effectiveness of PA networks

A rapid co-culture stamping device for studying intercellular communication.

Regulation of tissue development and repair depends on communication between neighbouring cells. Recent advances in cell micro-contact printing and microfluidics have facilitated the in-vitro study of homotypic and heterotypic cell-cell interaction. Nonetheless, these techniques are still complicated to perform and as a result, are seldom used by biologists. We report here development of a temporarily sealed microfluidic stamping device which utilizes a novel valve design for patterning two adherent cell lines with well-defined interlacing configurations to study cell-cell interactions. We demonstrate post-stamping cell viability of >95%, the stamping of multiple adherent cell types, and the ability to control the seeded cell density. We also show viability, proliferation and migration of cultured cells, enabling analysis of co-culture boundary conditions on cell fate. We also developed an in-vitro model of endothelial and cardiac stem cell interactions, which are thought to regulate coronary repair after myocardial injury. The stamp is fabricated using microfabrication techniques, is operated with a lab pipettor and uses very low reagent volumes of 20 μl with cell injection efficiency of >70%. This easy-to-use device provides a general strategy for micro-patterning of multiple cell types and will be important for studying cell-cell interactions in a multitude of applications

The Borwein brothers, Pi and the AGM

We consider some of Jonathan and Peter Borweins' contributions to the high-precision computation of $\pi$ and the elementary functions, with particular reference to their book "Pi and the AGM" (Wiley, 1987). Here "AGM" is the arithmetic-geometric mean of Gauss and Legendre. Because the AGM converges quadratically, it can be combined with fast multiplication algorithms to give fast algorithms for the $n$-bit computation of $\pi$, and more generally the elementary functions. These algorithms run in almost linear time $O(M(n)\log n)$, where $M(n)$ is the time for $n$-bit multiplication. We outline some of the results and algorithms given in Pi and the AGM, and present some related (but new) results. In particular, we improve the published error bounds for some quadratically and quartically convergent algorithms for $\pi$, such as the Gauss-Legendre algorithm. We show that an iteration of the Borwein-Borwein quartic algorithm for $\pi$ is equivalent to two iterations of the Gauss-Legendre quadratic algorithm for $\pi$, in the sense that they produce exactly the same sequence of approximations to $\pi$ if performed using exact arithmetic.Comment: 24 pages, 6 tables. Changed style file and reformatted algorithms in v

The chaperone protein clusterin may serve as a cerebrospinal fluid biomarker for chronic spinal cord disorders in the dog

Chronic spinal cord dysfunction occurs in dogs as a consequence of diverse aetiologies, including long-standing spinal cord compression and insidious neurodegenerative conditions. One such neurodegenerative condition is canine degenerative myelopathy (DM), which clinically is a challenge to differentiate from other chronic spinal cord conditions. Although the clinical diagnosis of DM can be strengthened by the identification of the Sod1 mutations that are observed in affected dogs, genetic analysis alone is insufficient to provide a definitive diagnosis. There is a requirement to identify biomarkers that can differentiate conditions with a similar clinical presentation, thus facilitating patient diagnostic and management strategies. A comparison of the cerebrospinal fluid (CSF) protein gel electrophoresis profile between idiopathic epilepsy (IE) and DM identified a protein band that was more prominent in DM. This band was subsequently found to contain a multifunctional protein clusterin (apolipoprotein J) that is protective against endoplasmic reticulum (ER) stress-mediated apoptosis, oxidative stress, and also serves as an extracellular chaperone influencing protein aggregation. Western blot analysis of CSF clusterin confirmed elevated levels in DM compared to IE (p &#60; 0.05). Analysis of spinal cord tissue from DM and control material found that clusterin expression was evident in neurons and that the clusterin mRNA levels from tissue extracts were elevated in DM compared to the control. The plasma clusterin levels was comparable between these groups. However, a comparison of clusterin CSF levels in a number of neurological conditions found that clusterin was elevated in both DM and chronic intervertebral disc disease (cIVDD) but not in meningoencephalitis and IE. These findings indicate that clusterin may potentially serve as a marker for chronic spinal cord disease in the dog; however, additional markers are required to differentiate DM from a concurrent condition such as cIVDD

Role of hemoclips in the management of acute bleeding from a gastric stromal tumor: a case report and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Though gastrointestinal stromal tumors (GISTs) frequently present with gastrointestinal bleeding, the guidelines for the management and control of bleeding are unclear especially in patients who are not appropriate for surgical resection.</p> <p>Case presentation</p> <p>We report a case of gastric GIST in an elderly patient who presented with bleeding. Homeostasis was achieved initially with the endoscopic placement of a hemoclip followed by treatment with the tyrosine kinase inhibitor, imatinib.</p> <p>Conclusion</p> <p>The management of bleeding GISTs in the elderly pose a challenging task to the gastroenterologist and treatment strategies should be tailored to the expertise of the endoscopist, surgeon and other supportive staff.</p

Sperm design and variation in the New World blackbirds (Icteridae)

Post-copulatory sexual selection (PCSS) is thought to be one of the evolutionary forces responsible for the rapid and divergent evolution of sperm design. However, whereas in some taxa particular sperm traits are positively associated with PCSS, in other taxa, these relationships are negative, and the causes of these different patterns across taxa are poorly understood. In a comparative study using New World blackbirds (Icteridae), we tested whether sperm design was influenced by the level of PCSS and found significant positive associations with the level of PCSS for all sperm components but head length. Additionally, whereas the absolute length of sperm components increased, their variation declined with the intensity of PCSS, indicating stabilizing selection around an optimal sperm design. Given the diversity of, and strong selection on, sperm design, it seems likely that sperm phenotype may influence sperm velocity within species. However, in contrast to other recent studies of passerine birds, but consistent with several other studies, we found no significant link between sperm design and velocity, using four different species that vary both in sperm design and PCSS. Potential reasons for this discrepancy between studies are discussed

A preliminary study of the effect of closed incision management with negative pressure wound therapy over high-risk incisions

Background Certain postoperative wounds are recognised to be associated with more complications than others and may be termed high-risk. Wound healing can be particularly challenging following high-energy trauma where wound necrosis and infection rates are high. Surgical incision for joint arthrodesis can also be considered high-risk as it requires extensive and invasive surgery and postoperative distal limb swelling and wound dehiscence are common. Recent human literature has investigated the use of negative pressure wound therapy (NPWT) over high-risk closed surgical incisions and beneficial effects have been noted including decreased drainage, decreased dehiscence and decreased infection rates. In a randomised, controlled study twenty cases undergoing distal limb high-energy fracture stabilisation or arthrodesis were randomised to NPWT or control groups. All cases had a modified Robert-Jones dressing applied for 72 h postoperatively and NPWT was applied for 24 h in the NPWT group. Morphometric assessment of limb circumference was performed at six sites preoperatively, 24 and 72 h postoperatively. Wound discharge was assessed at 24 and 72 h. Postoperative analgesia protocol was standardised and a Glasgow Composite Measure Pain Score (GCPS) carried out at 24, 48 and 72 h. Complications were noted and differences between groups were assessed. Results Percentage change in limb circumference between preoperative and 24 and 72 h postoperative measurements was significantly less at all sites for the NPWT group with exception of the joint proximal to the surgical site and the centre of the operated bone at 72 h. Median discharge score was lower in the NPWT group than the control group at 24 h. No significant differences in GCPS or complication rates were noted. Conclusions Digital swelling and wound discharge were reduced when NPWT was employed for closed incision management. Larger studies are required to evaluate whether this will result in reduced discomfort and complication rates postoperatively

Using Simulations as a Starting Point for Constructing Meaningful Learning Games

For many school administrators and decision makers, the term “video games” holds numerous cultural associations which make their adoption in the education space challenging. Additionally, the term is so broad that it can sometimes be difficult to communicate explicitly a desire to build learning experiences that go beyond the Drill and Kill edutainment titles that currently dominate most people’s perceptions of educational games. By contrast, the term “simulations” is often well respected among educators, particularly in the natural sciences. With “simulation” already being a full genre of video games, it would seem natural that researchers are beginning to explore the overlaps between simulation games and pedagogical goals that go beyond those found in Drill and Kill games. In this chapter, we survey some of the relevant research concerning both simulations and video games and outline practical pathways through which we can leverage the interest and frameworks designed for simulation construction to facilitate the introduction of video game concepts and experiences into the classroom environment. In particular, we report on the use of Starlogo TNG, a graphical programming environment in which kids themselves can create simulation-based video games, for deepening children’s understanding of scientific concepts