Dark Material Research Articles

Infrared spectroscopic characterization of the low-albedo materials on Iapetus

Iapetus, one of the large satellites of Saturn, has been studied over the centuries for its signature brightness contrast, light on one side and dark on the opposite. It has recently been suggested that the dark material is a combination of native and exogenous materials with distinct histories. We present an analysis of parts of the Cassini Regio, the darkest region on the leading hemisphere of Iapetus, focusing on the hydrocarbon signature with a view to detect and investigate differences in the material(s). We find variations in the hydrocarbon bands with geographic location, one type predominantly located on the leading hemisphere. A comparison with the equivalent spectral features on Phoebe and Hyperion reveals a predictable resemblance between the leading hemisphere material and Phoebe and an unexpected likeness between Hyperion’s darkest material and Iapetus’ trailing hemisphere surface. An analysis of the slope in the visible part of the spectrum is strongly affected by a rise in the continuum (∼0.35–0.65μm) attributed to Rayleigh scattering from nano-size particles on the surface. The continuum rise varies in strength with the albedo and H2O ice content, and when it is properly accounted for, the overall slope in all the identified spectral units is the same over the interval 0.35–2.3μm, independent of albedo or ice abundance. The interpretation of current and previous results offers two different scenarios illustrated by the presence of one vs. two dark materials distributed over the Iapetus surface. We describe the scenarios and their implications. The appearance of the aromatic and aliphatic absorption bands together in their measured relative strengths makes this spectral signature unique, and thus enables the comparison among the three satellites.

Critical Perspectives on Philip Pullman’s His Dark Materials: Essays on the Novels, the Film and the Stage Productions (review)

Critical Perspectives on Philip Pullman’s His Dark Materials: Essays on the Novels, the Film and the Stage Productions (review)

On the closure of public libraries of Oxfordshire

Philip Pullman writes books for children. His best known is probably the His Dark Materials trilogy, Northern Lights, The Subtle Knife and The Amber Spyglass. His most contentious probably The Good Man Jesus and the Scoundrel Christ. He writes not so much to explain as to allow the reader’s own imagination to work on his words. The same purpose is at the core of his belief in the value of public libraries. The debate on the role and future of public libraries in the UK was marked by the accusation that authors had their own interests in mind when they objected to library closures. Philip Pullman leapt to the attack. This is an edited version of his mauling of Oxfordshire County Council.

Delivery of dark material to Vesta via carbonaceous chondritic impacts

NASA’s Dawn spacecraft observations of Asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75μm filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater walls and rims); as flow-like deposits or rays commonly associated with topographic highs; and as dark spots (likely secondary impacts) nearby impact craters. This DM could be a relic of ancient volcanic activity or exogenic in origin. We report that the majority of the spectra of DM are similar to carbonaceous chondrite meteorites mixed with materials indigenous to Vesta. Using high-resolution seven color images we compared DM color properties (albedo, band depth) with laboratory measurements of possible analog materials. Band depth and albedo of DM are identical to those of carbonaceous chondrite xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance in DM (1–6vol.%) is consistent with howardite meteorites. We find no evidence for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of DM. Our modeling efforts using impact crater scaling laws and numerical models of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta during the formation of the ∼400km Veneneia basin by a low-velocity (<2km/s) carbonaceous impactor. This discovery is important because it strengthens the long-held idea that primitive bodies are the source of carbon and probably volatiles in the early Solar System.

Transforming carbon nanotube forest from darkest absorber to reflective mirror

Carbon nanotube (CNT) forests are known to be among the darkest materials on earth. They can absorb the entire visible range of electromagnetic wave more efficiently than any other known black material. We have attempted controlled mechanical processing of the CNTs and, surprisingly, observed mirror-like reflection from the processed area with 10%–15% reflectivity, a level higher than typical reflectivity of pure forests by over two orders of magnitude, for a wide range of the spectrum (570–1100 nm). Patterning of micro mirrors in the forest is demonstrated to show its potential application for producing monolithically integrated reflector-absorber arrays in the material.

Leah Price (ed): Unpacking My Library: Writers and Their Books

Think of this as Playboy for bibliophiles. Dozens of full-page, high resolution photographs will have you tilting Unpacking My Library on its side to better admire the stacks and shelves of thirteen authors from a variety of genres. Supporting interviews tell you when the authors bought their first books, how they arrange their books, and what books they keep on their bedside tables. Leah Price, professor of English at Harvard, has put together a captivating little collection that will leave you wanting more. Six of the thirteen authors included in Unpacking My Library—Rebecca Goldstein and Steven Pinker, Lev Grossman and Sophie Gee, and Claire Messud and James Wood—are couples and were chaptered together but interviewed separately. Each couple interviewed maintains shared libraries, so for each, there is a single photo set. The remaining seven authors included are Alison Bechdel, Stephen Carter, Junot Diaz, Jonathan Lethem, Philip Pullman, Gary Shteyngart, and Edmund White. Most exciting to me was the chapter with Pullman, author of His Dark Materials, one of my favorite series growing up. Pullman is the only author featured in Unpacking My Library who wrote an essay response instead of answering each of Price’s questions in turn and it’s nice to read his words uninterrupted. That said, Price asks great questions. Have you ever in your life given up reading? Uniformly not. How do you dispose of unwanted books? Bechdel keeps them, Diaz gives his away, Grossman and Gee put theirs out on the curb, Shteyngart uses the trash. How do you arrange your books? Jonathan Lethem ‘‘oscillate[s] between alphabetical absolutism and imperatives of genre, size, color, [and] publisher’’ (114). Authors were also asked about their shelving arrangements. Pinker stores his books in stackable cubes in order to avoid ‘‘those awful things called bookends’’

Into another world: From creativity to creative learning

This article is an account of a creative learning project conducted in the author’s school in which she worked with a storyteller to engage a class of 14–15-year-old students in exploring other worlds, inspired by the His Dark Materials novels by Philip Pullman. The project was conceived as teacher-led action research in which the author observed the impact of new creative learning approaches on the motivation of a group of students who had become disengaged from the learning process in school. Analysis of a series of critical incidents and associated evidence gave insights into the issues and challenges encountered and the effects on students’ learning as the project progressed. The author found that her own role in the classroom was challenged, which shifted her research towards a more ethnographic approach. Her belief in the power of creative learning was deepened, leading her to reflect on the implications for school improvement beyond her own practice and suggesting further lines of enquiry.

Exploring the effects of overburden on the sublimation and transport of H2O on Iapetus

It has been shown through both measurements and simulations that there exists a measurable ice-free, porous, overburden overlaying water ice on Cassini Regio. Mass transfer through this porous media in a vacuum would occur in the Knudsen regime, which provides sublimation rates orders of magnitude smaller than Hertz–Langmuir sublimation. The availability of water ice for transport from this region is thus currently controlled by mass transfer through the dark material overburden. Thermal segregation suggests that Iapetus’ polar regions have been brightened via ballistic transport of water and its subsequent cold trapping since exogenic deposition models predict dark high latitudes on the leading hemisphere. The limiting effect of the dark material on transport of water ice may thus greatly impact the current mass balance at the poles. The effects of the overburden on the global stability and transport of H2O is addressed in order to gain insight into its influence on the polar albedo distribution and current state of thermal segregation within the dark terrain. Results indicate that thermal segregation is currently an inactive or weak process within Cassini Regio, though it is an ongoing process at the inter-terrain regions. Modeling of polar accumulation suggests that even accounting for the current dark material cover within Cassini Regio there exists sufficient ballistically inbound water to overcome exogenic darkening mechanisms. Topographic effects on local albedo differences are also simulated to provide a more complete water stability study of Iapetus. Results suggest that topographically induced changes in heat flux may be sufficient to create the observed local albedo contrasts and also support ongoing dark exogenic deposition within Cassini Regio to explain the lack of bright slopes deep within the dark terrain.

Shallow dark matter cusps in galaxy clusters

We study the evolution of the stellar and dark matter components in a galaxy cluster of $10^{15} \, \rm{M_{\odot}}$ from $z=3$ to the present epoch using the high-resolution collisionless simulations of Ruszkowski & Springel (2009). At $z=3$ the dominant progenitor halos were populated with spherical model galaxies with and without accounting for adiabatic contraction. We apply a weighting scheme which allows us to change the relative amount of dark and stellar material assigned to each simulation particle in order to produce luminous properties which agree better with abundance matching arguments and observed bulge sizes at $z=3$. This permits the study of the effect of initial compactness on the evolution of the mass-size relation. We find that for more compact initial stellar distributions the size of the final Brightest Cluster Galaxy grows with mass according to $r\propto M^{2}$, whereas for more extended initial distributions, $r\propto M$. Our results show that collisionless mergers in a cosmological context can reduce the strength of inner dark matter cusps with changes in logarithmic slope of 0.3 to 0.5 at fixed radius. Shallow cusps such as those found recently in several strong lensing clusters thus do not necessarily conflict with CDM, but may rather reflect on the initial structure of the progenitor galaxies, which was shaped at high redshift by their formation process.

Masking Ability of IPS e.max ALL-Ceramics System of HO Series

To evaluate the masking ability of IPS e.max all-ceramics system of HO series. IPS e.max Press HO ingots were fabricated into twenty cylindrical specimens (n=5) with the diameter of 13mm and four different thinknesses (0.4mm, 0.6mm, 0.8mm, 1.0mm). All specimens after veneered, gazed and cemented to metal substrate disks (thickness 3mm, diameter 13mm) were measured on both the white background and metal substrate disks background using a spectrophotometer and values of L, a and b were calculated to compare color differences among four groups. Meanwhile ΔE with the preselected required color (A2 color) were calculated. ΔE&lt;1.5 was considered a clinically acceptable color match. In the 0.4mm thickness specimens group, the values of L, a and b significantly increased (-1.36±0.05, -0.15±0.06, -1.46±0.02, respectively) between the white background and abutment background. But there were no significant color differences in the other three groups (P&lt;0.05). In the 0.6mm and 0.8mm thicknesses specimens groups, the color difference values (0.71±0.04, 1.14±0.06, respectively) with A2 color were less than the defined value. Thus the cylindrical specimens with the thickness of 0.6mm, 0.8mm and 1.0mm could mask the metal substrate disks background sufficiently and the thickness of 0.6mm and 0.8mm had an acceptable color match compared with the target color. IPS e.max all-ceramics system of HO series can produce clinically acceptable color match and have the capacity to mask a dark background such as a dark tooth or core buildup material.

Compositional analysis of Hyperion with the Cassini Visual and Infrared Mapping Spectrometer

Compositional mapping of the surface of Hyperion using Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations reveals a heterogeneous surface dominated by water ice accompanied by additional materials. Carbon dioxide, as evidenced by a prominent absorption band centered at 4.26μm, is distributed over most of the surface, including icy regions. This does not represent exposures of pure CO2 ice, but concentrations of CO2 molecules adsorbed on other materials or complexed in H2O, perhaps as a clathrate (Cruikshank, D.P., Meyer, A.W., Brown, R.H., Clark, R.N., Jaumann, R., Stephan, K., Hibbitts, C.A., Sandford, S.A., Mastrapa, R., Filacchione, G., Dalle Ore, C.M., Nicholson, P.D., Buratti, B.J., McCord, T.B., Nelson, R.M., Dalton, J.B., Baines, K.H., Matson, D.L., The VIMS Team [2010]. Icarus 206, 561–572). Localized deposits of low-albedo material in subcircular depressions exhibit spectral absorptions indicative of C–H in aromatic (3.29μm) and aliphatic (3.35–3.50μm) hydrocarbons. An absorption band at 2.42μm that is also seen on other saturnian satellites, tentatively identified as H2 (Clark, R.N. et al. [2011]. In: Proc. AAS-DPS Meeting, 43, 1563; Clark et al., in preparation, 2012) adsorbed on dark material grains, is also prominent. Our best spectral models included H2O and CO2 ice, with small amounts of nanophase Fe and Fe2O3. Weaker and more spatially scattered absorption features are also found at 4.48, 4.60, and 4.89μm, although no clear molecular identifications have yet been made. While strongest in the low-albedo deposits, the CO2, hydrocarbon and putative H2 bands vary in strength throughout the icy regions, as do the 4.48-, 4.60- and 4.89-μm bands, suggesting that this background ice is laced with a complex mixture of non-ice compounds.

Water ice abundance and CO2 band strength on the saturnian satellite Phoebe from Cassini/VIMS observations

We have studied the near-infrared spectrum of the Saturn satellite Phoebe, a distant satellite observed before Cassini’s Saturn orbit insertion, using data from the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini orbiter. We have done a critical calibration of the dataset that involves careful correction of dark artifacts. We model areally mixed water ice and non-ice (assumed segregated because of the low ∼3% albedo of the non-ice material) for several high and medium resolution observations of Phoebe made near closest approach. Using a Hapke roughness factor of 15°, we find ice abundances from ∼0.1% to over 4%. The ice grain radii vary from 1 to 10μm. These are displayed on a projected map of Phoebe with about 50% coverage (about 33% coverage at better than 5km spatial resolution). Detailed looks at the water ice spectral fits shows that the weak 1.05 and 1.25-μm bands are missing in most of the spectra, implying that the ice endmember is not pure ice, but has a dark material mixed with it that lowers the albedo and suppresses these bands. We made a model of ice contaminated with Phoebe-like dark material showing that a few percent of dark material lowers the albedo to ∼50% and suppresses the bands. The dirty ice model produces better fits to the spectra and implies that the amount of dirty ice is about 1.5 times the amount of pure ice. We have also calculated the CO2 band depth for these same observations and projected the results. The CO2 band depth varies inversely with water ice abundance.

Philip Pullman: United Kingdom ★ Author

Philip PullmanUnited Kingdom ★ Author Lydia Kokkola “Stories are the most important thing in the world. Without stories, we wouldn’t be human beings.” Philip Pullman The son of an Air Force pilot, Philip Pullman was born in Norwich in 1946, but spent much of his early childhood in his Grandparents’ rectory where he heard stories combining the landscape, history, Biblical stories and fiction; elements that were to emerge in his own story-telling as an adult. At the age of eleven, his family moved to North Wales where Pullman took up illustrating. These experiences were woven into one of his earliest novels, The Broken Bridge. His formal education at Oxford University was also to produce a fictional setting as it was incorporated into the His Dark Materials trilogy. After a short but successful career as a teacher and teacher-trainer, he took up fulltime writing in 1995 following the success of Northern Lights (The Golden Compass in North America). His works have been translated into over 40 languages and include adventure stories, plays, writing for adults as the well as the fantasy and fairy tales for which he is best known. Internationally, Pullman is best known for the His Dark Materials trilogy set in an alternative universe. The first novel was made into a film—The Golden Compass—and has also been successfully adapted for the stage. Pullman’s complex engagement with Christianity, spirituality and the desire to keep children “innocent,” as well as his allusions to classical works of English literature such as John Milton’s Paradise Lost make for a series of cross-over books which appeal equally, albeit differently, to children, adults, and literary critics. Prior to the publication of these works, however, Pullman had already established himself as an author of substance. The Sally Lockhart Quartet, set in London in the Victorian era, features an enterprising young woman who exposes the darker aspects of the puritanical morality and extreme class division of the period as she searches for a ruby that is rightfully hers. Pullman returned to the Victorian era in his The New Cut Gang series, which features a gang of children who appear to have stepped out of a Sherlock Holmes story. Pullman’s appreciation of Arthur Conan Doyle is also evident in his play, Sherlock Holmes and the Limehouse Horror. Pullman’s prolific and varied output, his willingness to be provocative, his complex use of allusion, and good storytelling have made him as popular with critics as he is with his child and teenage readers. Several monographs and numerous articles have been produced on his works, and he regularly speaks in public addressing issues ranging from religious tolerance to funding for public library services. Selected Publications The Ruby in the Smoke. Oxford: Oxford University Press, 1985. Print. Google Scholar The Broken Bridge. London: Macmillan Children’s Books 1990. Print. Google Scholar Northern Lights. London: Scholastic Point, 1995. Print. Google Scholar Clockwork Or, All Wound Up. New York: Doubleday, 1996. Print. Google Scholar I Was a Rat! or, The Scarlet Slippers. New York: Doubleday, 1999. Print. [End Page 58] Google Scholar Copyright © 2012 Bookbird, Inc

부산 금정산 일대 지하수공내 공막힘 물질의 특징과 형성원인

The physical, chemical, and biological properties of clogging materials formed within groundwater wells in the Mt. Geumjeong area, Busan, Korea, were characterized. The particle size distribution (PSD) of clogging materials was measured by a laser analyzer. XRD, SEM, and TEM analyses were performed to obtain mineralogical information on the clogging materials, with an emphasis on identifying and characterizing the mineral species. In most cases, PSD data exhibited an near log-normal distribution; however, variations in frequency distribution were found in some intervals (bi-or trimodal distributions), raising the possibility that particles originated from several sources or were formed at different times. XRD data revealed that the clogging materials were mainly amorphous ironhydroxides such as goethite, ferrihydrite, and lapidocrocite, with lesser amounts of Fe, Mn, and Zn metals and silicates such as quartz, feldspar, micas, and smectite. Reddish brown material was amorphous hydrous ferriciron (HFO), and dark red and dark black materials were Fe, Mn-hydroxides. Greyish white and pale brown materials consisted of silicates. SEM observations indicated that the clogging materials were mainly HFO associated with iron bacteria such as Gallionella and Leptothrix, with small amounts of rock fragments. In TEM analysis, disseminated iron particles were commonly observed in the cell and sheath of iron bacteria, indicating that iron was precipitated in close association with the metabolism of bacterial activity. Rock-forming minerals such as quartz, feldspar, and micas were primarily derived from soils or granite aquifers, which are widely distributed in the study area. The results indicate the importance of elucidating the formation mechanisms of clogging materials to ensure sustainable well capacity.

Mocking God and Celebrating Satan: Parodies and Profanities in Philip Pullman’s His Dark Materials

Given its stance against organised religion, it is perhaps not surprising that Philip Pullman’s award-winning trilogy His Dark Materials has, alongside the plaudits and praise, invited controversy and debate. Jacobs (The Weekly Standard, 2000), for instance, views the “anti-Christian” theme in Pullman’s work as both misleading and dishonest, whilst Hitchens (The Mail on Sunday, 2002) denounces it as atheistic “propaganda.” Of central concern to these critics, and others, is the impact of Pullman’s heretical understandings on impressionable young readers. I would suggest that such concern implies a somewhat questionable homogenisation of young readers, and fails to recognise the empowering potential residing in Pullman’s text. Indeed, by drawing on Mikhail Bakhtin’s theory of “carnival,” a literary mode which subverts official culture through laughter and role reversals, it can be argued that far from indoctrinating the reader or promoting uncontested atheistic understandings, the heretical disruptions and inversions in Pullman’s religious theme encourage an altogether more positive and plural response.

Rethinking the Humanities

Rethinking the Humanities Len Findlay (bio) In 1990 I secured a commitment from the discretionary fund of the then Dean of Graduate Studies and Associate Vice-President Research at the University of Saskatchewan, Jack Manns. There were three key features of this arrangement for which I gained approval. The Humanities Research Unit I proposed to establish would not be located in a single college but would develop collaborative relations with several. It would report to the Office of the Vice-President Research. And it would be funded from the university's base budget. This arrangement allowed for a strategy of serving the traditional humanities community on campus while creating new collaborative communities on and off campus. Here was a way to advance the disciplinary and transdisciplinary agenda which Canadian universities were beginning to favour and to do so with some intellectual freedom and secure (if modest) resources. This was not the first attempt to "rethink" the humanities, nor has it been easy to keep this project going through various waves of institutional planning, prioritizing, branding, positioning, and forced migration from our long-term space in order to accommodate a Confucius Institute, but the Humanities Research Unit survives and prospers as a source of critique, debate, education, and learning on display and in progress, thanks to the co-direction provided by first Marie [End Page 1] Battiste (Aboriginal Education) and Lynne Bell (Art and Art History) and by a range of supportive colleagues, students, and staff. From the outset, unit programming emphasized three key themes: threats and impediments, academic value, and decolonizing education. As these themes (and their variations here) attest, humanities work is always pursued on challenging terrain but with intellectual resources predominantly but not exclusively text-based and well fitted to engaging with and illuminating questions of pressing importance for scholars, students, institutions, and citizens. Over the years, the unit has approached each of the events it has solely or co-operatively sponsored as one more moment in a continuous process of remaking and reviewing the case for the humanities in contemporary Canada. And at the heart of this endeavour remains my home discipline of English Studies. As a disciplinary formation, English uses its compositional or training component and the global status of English as "the" language of science and business to dominate French, Indigenous, and immigrant-heritage languages on campuses across the country where the profitable option is almost always the easiest sell. English still has numbers—of students and faculty—to its advantage relative to its sister disciplines, making for a positive budgetary presence and a sizeable political presence in areas of collegial governance. However, English as the humanities' champion is also the instrumentalists' greatest prize, the place into which almost all the humanities can be caused to retreat and gradually forego allegiance to their dark materials. A single omnibus department called Composition and Cultural Studies does not seem much of a stretch once omnibus budgeting arrives from Ottawa at a campus near you, if it is not there already. English represents hope and enhanced endangerment that comes with being one of the last dominoes standing in the current remaking of Canadian postsecondary institutions. How, then, does English live up to its role as a champion of the humanities in hard times, rather than serving as a conduit for further cynical compaction and immiseration of intellectual work? One answer to this question must surely be new forms of solidarity beyond the "narcissism of small differences" (Freud 199; see also Kolstø) and resource wars. And it is such a form of non-homogenizing, performative solidarity that this special issue seeks to model. [End Page 2] Caveat auctor! In 1963 in France, in the middle of the theory ferment that has been read both as liberating and as endangering literary studies via the activities of Foucault, Derrida, Cixous, Irigaray, et al., there occurred the Humanist Controversy (La Querelle de Humanisme) whose central figure was Louis Althusser. This controversy, like the current special issue of ESC, derived from someone bringing people together to address a broad issue with particular political and academic aims. When an invitation was extended by editor Erich Fromm to Althusser to contribute to a collection on...

Europa's icy bright plains and dark linea: Exogenic and endogenic contributions to composition and surface properties

We compare linear spectral modeling solutions yielding surface abundance estimates and water ice grain size information from low‐noise Galileo Near‐Infrared Mapping Spectrometer (NIMS) observations for three widely spaced locations on Europa. Bright equatorial plains on the orbital leading side are dominated by fine‐grained (∼50–75 μm) water ice (&gt;80 wt%). This area shows a low abundance of hydrated salts and statistically insignificant amounts of hydrated sulfuric acid. A midlatitude northern hemisphere location on the trailing side exhibits strikingly different surface composition and properties for similar terrain. The modeled abundance of hydrated sulfuric acid exceeds 40% here; large‐grained water ice (∼250 μm diameter) dominates the ice grain size distribution. A third location at high southern latitudes on the leading side exhibits high abundances of water ice (&gt;67%) and no detectable sulfuric acid hydrate. Water ice grain sizes here are intermediate between those of the other locations, at 75–100 μm. We resolve compositional differences between the darkest materials (at visible wavelengths) and the most hydrated materials (as evidenced by the distortion of water ice absorption bands) on Europa's leading side. Distinctive water ice grain size distributions are associated with visibly dark materials in all three locations. Our results help distinguish between exogenic and endogenic influences on Europa's present‐day surface composition. The results are consistent with migration and redeposition of sputtered water ice molecules from trailing to leading side locations.

Gallbladder Hemorrhage Mimicking Acute Cholecystitis in a Patient under Antiplatelet Therapy

Hemorrhage within the gallbladder is rare but potentially fatal. It can be easily overlooked and misdiagnosed because of its low incidence and presentation that is similar to other types of hepatobiliary disease. We present an unusual case of gallbladder hemorrhage in a 36-year-old male patient who was taking antiplatelet medication following cardiac surgery. The patient was misdiagnosed with acute primary cholecystitis and, in consideration of postoperative complications with cardiovascular comorbities, serial treatment with urgent percutaneous transhepatic gallbladder drainage and delayed laparoscopic cholecystectomy was prescribed. Unexpectedly, a gallbladder hemorrhage was intraoperatively confirmed as the gallbladder appeared filled with dark blood clot-like materials. The patient recovered well and was discharged on the 3rd postoperative day without complications. In patients who are on antiplatelet therapy, gallbladder hemorrhage should be considered in the differential diagnosis if they have symptoms typical of biliary colic. In addition, delayed surgery with prompt biliary diversion may represent a safe and effective treatment approach.

The surface composition of Iapetus: Mapping results from Cassini VIMS

Cassini VIMS has obtained spatially resolved imaging spectroscopy data on numerous satellites of Saturn. A very close fly-by of Iapetus on September 10, 2007 provided the best data on the spectral signature and spatial extent of dark material on Iapetus. This Cassini Rev 49 Iapetus fly-by provided spatially resolved imaging spectroscopy data of the dark material and the leading/trailing side transition from the dark material to visually bright ice on the trailing side. Compositional mapping and radiative transfer modeling shows that the dark material is composed of metallic iron, nano-size iron oxide (hematite), CO2, H2O ice, and possible signatures of ammonia, bound water, H2 or OH-bearing minerals, trace organics, and as yet unidentified materials. CO2 indicates a pattern of increasing CO2 strength from the leading side apex to the transition zone to the icy trailing side. A Rayleigh scattering peak in the visible part of the spectrum indicates the dark material has a large component of fine, sub-0.5-μm diameter particles consistent with nanophase hematite and nanophase iron. Spectral signatures of ice also indicate that sub-0.5-μm diameter particles are present in the icy regions. Multiple lines of evidence point to an external origin for the dark material on Iapetus, including the global spatial pattern of dark material, local patterns including crater and cliff walls shielding implantation on slopes facing away from the leading side, exposing clean ice, and slopes facing the leading direction which show higher abundances of dark material. Multiple spectral features and overall spectral shape of the dark material on Iapetus match those seen on Phoebe, Hyperion, Dione, Epimetheus, Saturn’s rings Cassini Division, and the F-ring implying the material has a common composition throughout the Saturn system. The dark material appears to have significant components of nanophase metallic iron and nanophase hematite contributing to the observed UV absorption. The blue scattering peak with a strong UV–visible absorption is observed in spectra of all satellites that contain dark material, again pointing to a common origin of contamination by metallic iron that is partially oxidized.

Iridescent colour production in hairs of blind golden moles ( Chrysochloridae )

Relative to other metazoans, the mammalian integument is thought to be limited in colour. In particular, while iridescence is widespread among birds and arthropods, it has only rarely been reported in mammals. Here, we examine the colour, morphology and optical mechanisms in hairs from four species of golden mole (Mammalia: Chrysochloridae) that are characterized by sheens ranging from purple to green. Microspectrophotometry reveals that this colour is weak and variable. Iridescent hairs are flattened and have highly reduced cuticular scales, providing a broad and smooth surface for light reflection. These scales form multiple layers of light and dark materials of consistent thickness, strikingly similar to those in the elytra of iridescent beetles. Optical modelling suggests that the multi-layers produce colour through thin-film interference, and that the sensitivity of this mechanism to slight changes in layer thickness and number explains colour variability. While coloured integumentary structures are typically thought to evolve as sexual ornaments, the blindness of golden moles suggests that the colour may be an epiphenomenon resulting from evolution via other selective factors, including the ability to move and keep clean in dirt and sand.