Sample records for cone-in-cone calcite veins

  1. Lithofacies palaeogeography and sedimentology Beef and cone-in-cone calcite fibrous cements associated with the end-Permian and end-Triassic mass extinctions:Reassessment of processes of formation

    Institute of Scientific and Technical Information of China (English)

    Stephen Kershaw; Li Guo


    This paper reassesses published interpretation that beef and cone-in-cone (B-CIC) fibrous calcite cements were precipitated contemporaneously just below the sea floor in uncon-solidated sediment, in limestones associated with the end-Permian (P/T) and end-Triassic (T/J) mass extinctions. That interpretation introduced the concept of a sub-seafloor car-bonate factory associated with ocean acidification by raised carbon dioxide driven by volcanic eruption, coinciding with mass extinction. However, our new fieldwork and petrographic analysis, with literature comparison, reveals several problems with this concept. Two key points based on evidence in the T/J transition of the UK are:(1) that B-CIC calcite deposits form thin scattered layers and lenses at several horizons, not a distinct deposit associated with volcanic activity; and (2) B-CIC calcite is more common in Early Jurassic sediments after the extinction and after the end of the Central Atlantic Magmatic Province volcanism proposed to have supplied the carbon dioxide required. Our samples from Late Triassic, Early Jurassic and Early Cretaceous limestones in southern UK show that B-CIC calcite occurs in both marine and non-marine sediments, therefore ocean processes are not mandatory for its formation. There is no proof that fibrous calcite was formed before lithification, but our Early Jurassic samples do prove fibrous calcite formed after compaction, thus interpretation of crystal growth in uncon-solidated sediment is problematic. Furthermore, B-CIC crystals mostly grew both upwards and downwards equally, contradicting the interpretation of the novel carbonate factory that they grew preferentially upwards in soft sediment. Finally, Early Jurassic and Early Cretaceous examples are not associated with mass extinction. Three further key points derived from the literature include: (1) B-CIC calcite is wide-spread geographically and stratigraphically, not clustered around mass extinctions or the Paleocene

  2. Fluid inclusion studies of calcite veins from Yucca Mountain, Nevada, Tuffs: Environment of formation

    Energy Technology Data Exchange (ETDEWEB)

    Roedder, E. [Harvard Univ., Cambridge, MA (United States); Whelan, J.F. [Geological Survey, Denver, CO (United States); Vaniman, D.T. [Los Alamos National Lab., NM (United States)


    Calcite vein and vug fillings at four depths (130-314m), all above the present water table in USW G-1 bore hole at Yucca Mountain, Nevada, contain primary fluid inclusions with variable vapor/liquid raitos: Most of these inclusions are either full of liquid or full of vapor. The liquid-filled inclusions show that most of the host calcite crystallized from fluids at <100{degrees}C. The vapor-filled inclusions provide evidence that a separate vapor phase was present in the fluid during crystallization. Studies of these vapor-filled inclusions on the microscope crushing stage were interpreted in an earlier paper as indicating trapping of an air-water-CO{sub 2} vapor phase at ``<100{degrees}C``. Our new studies reveal the additional presence of major methane in the vapor-filled inclusion, indicating even lower temperatures of trapping, perhaps at near-surface temperatures. They also show that the host calcite crystals grew from a flowing film of water on the walls of fractures open to the atmosphere, the vapor-filled inclusions representing bubbles that exsolved from this film onto the crystal surface.

  3. Fluid inclusion studies of calcite veins from Yucca Mountain, Nevada, Tuffs: Environment of formation

    Energy Technology Data Exchange (ETDEWEB)

    Roedder, E. [Harvard Univ., Cambridge, MA (United States); Whelan, J.F. [Geological Survey, Denver, CO (United States); Vaniman, D.T. [Los Alamos National Lab., NM (United States)


    Calcite vein and vug fillings at fourth depths (130-314m), all above the present water table in USW G-1 bore hole at Yucca Mountain, Nevada, contain primary fluid inclusions with variable vapor/liquid ratios: most of these inclusions are either full of liquid or full of vapor. The liquid-filled inclusions show that most of the host calcite crystallized from fluids at <100{degrees}C. The vapor-filled inclusions provide evidence that a separate vapor phase was present in the fluid during crystallization. Studies of these vapor-filled inclusions on the microscope crushing stage were interpreted in an earlier paper as indicating trapping of an air-water-CO{sub 2} vapor phase at {open_quotes}100{degrees}C{close_quotes}. Our new studies reveal the additional presence of major methane in the vapor-filled inclusion, indicating even lower temperatures of trapping, perhaps at near-surface temperatures. They also show that the host calcite crystals grew from a flowing film of water on the walls of fractures open to the atmosphere, the vapor-filled inclusions representing bubbles that exsolved from this film onto the crystal surface.

  4. Application of Calcite Veins to Study of Newly-activated Faulting

    Institute of Scientific and Technical Information of China (English)

    刘行松; 史兰斌; 唐汉军; 林传勇; 何永年


    The study of period and chronology of fault activity in major worksites in an area with exposed basement rocks is quite difficult. The authors have applied the combinative techniques of field investigation, microscopic observation and isotopic dating to studying the calcite veins filled in the fault zones in several major engineering regions and got successful results. The following conclusions are reached: (i) The last period of strong activity of fault F8 in the Tianshengqiao Hydropower Station, Nanpan River is 200 ka B. P. , and there has been, no obvious activity since 150 ka. (ii) The last period of strong activity for 5 faults in Shixiali Reservoir, Yangyuan County, Hebei Province is 200-300 ka B. P. , and there has been no obvious activity since 200 ka. The research results provide a sound basis of engineering geology for project designers.

  5. Continuous 500,000-year climate record from vein calcite in Devils Hole, Nevada (United States)

    Winograd, I.J.; Coplen, T.B.; Landwehr, J.M.; Riggs, A.C.; Ludwig, K. R.; Szabo, B. J.; Kolesar, Peter T.; Revesz, K.M.


    Oxygen-18 (??18O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine ??18O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

  6. Continuous 500,000-year climate record from vein calcite in devils hole, nevada. (United States)

    Winograd, I J; Coplen, T B; Landwehr, J M; Riggs, A C; Ludwig, K R; Szabo, B J; Kolesar, P T; Revesz, K M


    Oxygen-18 (delta(18)O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine delta(18)O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

  7. A 250,000-year climatic record from great basin vein calcite: implications for milankovitch theory. (United States)

    Winograd, I J; Coplen, T B; Szabo, B J; Riggs, A C


    A continuous record of oxygen-18 (delta(18)O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole-an open fault zone at Ash Meadows, Nevada-between 50 and 310 ka (thousand years ago). The configuration of the delta(18)O versus time curve closely resembles the marine and Antarctic ice core (Vostok) delta(18)O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 +/- 3 ka, at least 17,000 years earlier than indicated by the marine delta(18)O record and 7,000 years earlier than indicated by the less well dated Antarctic delta(18)O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine delta(18)O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

  8. A 250,000-year climatic record from great basin vein calcite: Implications for Milankovitch theory (United States)

    Winograd, I.J.; Szabo, B. J.; Coplen, T.B.; Riggs, A.C.


    A continuous record of oxygen-18 (??18O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole - an open fault zone at Ash Meadows, Nevada - between 50 and 310 ka (thousand years ago). The configuration of the ??18O versus time curve closely resembles the marine and Antarctic ice core (Vostok) ??18O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 ?? 3 ka, at least 17,000 years earlier than indicated by the marine ??18O record and 7,000 years earlier than indicated by the less well dated Antarctic ??18O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine ??18O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

  9. U-Th dating of vein calcite by LA-MC-ICP-MS: preliminary results from geothermal systems (United States)

    McGee, L. E.; Reich, M.; Rodriguez, V.; Leisen, M.; Barra, F.


    The measurement of U-series isotopes in precipitated minerals such as calcite holds various challenges, including low U and Th concentrations (in the ppb-ppt range), and the presence of detrital 232Th which can lead to age overestimations. Additionally, as yet there does not exist a calcite standard reference material for inter-laboratory accuracy and precision comparison, with most laboratories using their own in-house standard material and focussing largely on application to paleoclimate studies (e.g. corals and speleothems). In actively deforming regions, high-pressure hydrothermal fluids play an important role in faulting and vein formation, and commonly fault rupture is followed by rapid sealing through mineral precipitation. Therefore, precise dating of vein growth is of special importance to our understanding of the complex interplay between seismic events and fluid flow in the upper crust, and opens up a new field of study using U-Th techniques. The ability to accurately date fault-filling calcite within such settings has the power to elucidate the connection between structure and fluid flow in the development of geothermal systems, and provide valuable information on the longevity of the heat/water source, in addition to regional magmatic history. We are developing U-Th measurements and ages of vein calcite from geothermal systems using a Neptune Plus MC-ICP-MS (with 5 CDDs and 3 SEMs) coupled to an excimer 193nm Photon Machines laser. We will be comparing our results with an 189ka in-house flowstone calcite standard previously dated by TIMS, as well as developing a geothermal calcite standard.

  10. Effect of outlet diameter of cone-in-cone insert on silo flow pattern%锥形改流体下部孔径对筒仓卸料流态的影响

    Institute of Scientific and Technical Information of China (English)

    谭援强; 肖湘武; 郑军辉; 姜胜强; 高伟


    为了获取锥形改流体(cone-in-cone)下部孔径对筒仓内卸料流态和仓壁压力的影响,实现中心流筒仓内物料流态从中心流到整体流的转变,改善筒仓内物料流动环境,建立模型,用试验验证模型是正确的,该文采用离散元法对三维筒仓中ABS球卸料过程进行了数值模拟。数值模拟结果表明:筒仓卸料口尺寸不变时,减小锥形改流体下部孔径,整体流系数增大,筒仓内物料流态能够从中心流转变为整体流,筒仓壁峰值压力减小且峰值压力位置上移。改流体倾角为120°、135°时,当锥形改流体距筒仓锥形壁面的距离与锥形改流体下部孔径的比值大于等于1时,能实现从中心流到整体流的转变。该研究基于数值模拟结果提出了锥形改流体的设计标准,可为工程上确定改流体结构、位置参数提供参考。%In the food, chemical, pharmaceutical and other industrial engineering field, about 50% of the products and 75% of raw materials are usually stored in the form of particles in the silo. The silo flow pattern can be divided into the mass flow and the funnel flow. In the process of silo design, the mass flow pattern is preferred. With the appropriate presence of cone-in-cone insert, the funnel flow pattern can be changed into mass flow pattern in funnel flow silo. In order to understand the effect of structure and position parameters of cone-in-cone insert on the flow pattern and develop a theory model to design them properly, the discharging processes of acrylonitrile butadiene styrene copolymer (ABS) beads in scale-down funnel flow silo were simulated using the discrete element method (DEM). The validity of the DEM simulations was confirmed by comparing with the experimental results. Mass flow index (MFI) was used to judge silo flow pattern. Firstly, the effects of the height of cone-in-cone insert, the distance between outlet of cone-in-cone insert and discharge

  11. Fluids along the North Anatolian Fault, Niksar basin, north central Turkey: Insight from stable isotopic and geochemical analysis of calcite veins (United States)

    Sturrock, Colin P.; Catlos, Elizabeth J.; Miller, Nathan R.; Akgun, Aykut; Fall, András; Gabitov, Rinat I.; Yilmaz, Ismail Omer; Larson, Toti; Black, Karen N.


    Six limestone assemblages along the North Anatolian Fault (NAF) Niksar pull-apart basin in northern Turkey were analyzed for δ18OPDB and δ13CPDB using bulk isotope ratio mass spectrometry (IRMS). Matrix-vein differences in δ18OPDB (-2.1 to 6.3‰) and δ13CPDB (-0.9 to 4.6‰) suggest a closed fluid system and rock buffering. Veins in one travertine and two limestone assemblages were further subjected to cathodoluminescence, trace element (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) and δ18OPDB (Secondary Ion Mass Spectrometry, SIMS) analyses. Fluid inclusions in one limestone sample yield Th of 83.8 ± 7.3 °C (±1σ, mean average). SIMS δ18OPDB values across veins show fine-scale variations interpreted as evolving thermal conditions during growth and limited rock buffering seen at a higher-resolution than IRMS. Rare earth element data suggest calcite veins precipitated from seawater, whereas the travertine has a hydrothermal source. The δ18OSMOW-fluid for the mineralizing fluid that reproduces Th is +2‰, in range of Cretaceous brines, as opposed to negative δ18OSMOW-fluid from meteoric, groundwater, and geothermal sites in the region and highly positive δ18OSMOW-fluid expected for mantle-derived fluids. Calcite veins at this location do not record evidence for deeply-sourced metamorphic and magmatic fluids, an observation that differs from what is reported for the NAF elsewhere along strike.

  12. Diagenetic environments of calcite veins hosted in marine carbonate rocks in middle Yangtze region of South China%中扬子海相碳酸盐岩中方解石脉成岩环境研究

    Institute of Scientific and Technical Information of China (English)

    王芙蓉; 何生; 杨兴业


    Analyses of thin slices, cathodoluminescence and carbon-oxygen isotope of calcite veins hosted in marine carbonate rocks distributed around Jingshan County in the middle Yangtze region of South China indicated that, two crystal forms including radial calcite and isometric texture calcite could be identified in calcite veins in the Triassic and the cathodoluminescence intensity was different. The Permian and Ordovician fractures were mainly filled with isometric texture calcite veins and the cathodoluminescence intensity was similar with that of the surrounding rocks. The δl3 CPDB value of calcite veins ranged from -6. 76‰ to 4. Ol‰and the δ18 OPDB value ranged from -17. 95‰to -5. 67‰, indicating the marine phreatic environment and the mixing phreatic environment for calcite veins deposition. Calcite veins in the Triassic were sedimentary origin, and part of calcite veins in the Permian and the Ordovician suffered latter diagenetic fluid dissolution. Fluid generated from organic-matter maturation effected the formation of calcite veins in the Permian to some degree.%通过对中扬子京山县城周边露头碳酸盐岩中方解石脉的普通薄片、阴极发光以及碳氧同位索等资料分析,认为该区露头三叠系裂隙中充填放射状和等轴粒状的方解石且阴极发光强度有差异,二叠系和奥陶系裂隙中主要为等轴粒状方解石,阴极发光与围岩相似.方解石脉的δ13CPDB位于-6.76‰~4.01‰之间,δ18OPDB在-17.95‰~-5.67‰之间,基本为海水潜流带一混合水潜流带沉积环境.三叠系方解石脉基本上为沉积碳酸盐岩,二叠系和奥陶系部分方解石脉受后期成岩流体的影响,其中二叠系有饥质成熟产生的流体对该层系方解石脉的形成有一定影响.

  13. Microstructural analysis and calcite piezometry on hydrothermal veins: Insights into the deformation history of the Cocos Plate at Site U1414 (IODP Expedition 344) (United States)

    Brandstätter, Jennifer; Kurz, Walter; Rogowitz, Anna


    In this study we present microstructural data from hydrothermal veins in the sedimentary cover and the igneous basement recovered from Hole U1414A, Integrated Ocean Drilling Program (IODP) Expedition 344 (Costa Rica Seismogenesis Project), to constrain deformation mechanism operating in the subducting Cocos Plate. Cathodoluminescence studies, mechanical e-twin piezometry and electron backscatter diffraction (EBSD) analyses of carbonate veins were used to give insights into the deformation conditions and to help to understand the tectonic deformation history of the Cocos Plate offshore Costa Rica. Analyses of microstructures in the sedimentary rocks and in the basalt of the igneous basement reveal brittle deformation, as well as crystal-plastic deformation of the host rock and the vein material. Cathodoluminescence images showed that in the basalt fluid flow and related precipitation occurred over several episodes. The differential stresses, obtained from two different piezometers using the same parameter (twin density), indicate various mean differential stresses of 49 ± 11 and 69 ± 30 MPa and EBSD mapping of calcite veins reveals low-angle subgrain boundaries. Deformation temperatures are restricted to the range from 170°C to 220°C, due to the characteristics of the existing twins and the lack of high-temperature intracrystalline deformation mechanisms (>220°C). The obtained results suggest that deformation occurred over a period associated with changes of ambient temperatures, occurrence of fluids and hydrofracturing, induced differential stresses due to the bending of the plate at the trench, and related seismic activity.

  14. Commentary on the state of knowledge of the origins of the Yucca Mountain calcite veins. Special report number 17, Contract number 94/96.0003

    Energy Technology Data Exchange (ETDEWEB)

    Archambeau, C.


    This report is a compilation of papers and a letter providing technical information on the origin and geochemistry of calcite veins and calcretes in the vicinity of the Yucca Mountain repository. The information is presented to demonstrate that these deposits may be ``thermogenic`` in origin with some alteration by pedogenic processes. The papers present isotope ratios of uranium, strontium, and carbon to support the claims for a hydrothermal source. The letter provides a critical review of a previous paper presented at the 64th Advisory Committee on Nuclear Waste. The report makes an attempt to emphasize the need to review this possible origin because it has dramatic implications on the geologic history, paleo-ground water levels, and integrity of the repository.

  15. Constraints on Neogene deformation in the southern Terror Rift from calcite twinning analyses of veins within the ANDRILL MIS core, Victoria Land Basin, Antarctica (United States)

    Paulsen, T. S.; Demosthenous, C.; Wilson, T. J.; Millan, C.


    The ANDRILL MIS (McMurdo Ice Shelf) Drilling Project obtained over 1200 meters of Neogene sedimentary and volcanic rocks in 2006/2007. Systematic fracture logging of the AND-1B core identified 1,475 natural fractures, i.e. pre-existing fractures in the rock intersected by coring. The most abundant natural fractures are normal faults and calcite veins; reverse faults, brecciated zones, and sedimentary intrusions are also present. In order to better understand Neogene deformation patterns within the southern Terror Rift, we have been conducting strain analyses on mechanically twinned calcite within healed fractures in the drill core. Twinning strains using all of the data from each sample studied to date range from 2% to 10%. The cleaned data (20% of the largest magnitude deviations removed) typically show ≤30% negative expected values, consistent with a single deformation episode or multiple ~coaxial deformation episodes. The majority of the samples record horizontal extension, similar to strain patterns expected in a normal fault regime and/or vertical sedimentary compaction in a continental rift system. The morphology, width, and intensity of twins in the samples suggest that twinning typically occurred at temperatures <170° C. Twinning intensities suggest differential stress magnitudes that caused the twinning ranged from 216 to 295 MPa.

  16. Controls on the long term earthquake behavior of an intraplate fault revealed by U-Th and stable isotope analyses of syntectonic calcite veins (United States)

    Williams, Randolph; Goodwin, Laurel; Sharp, Warren; Mozley, Peter


    U-Th dates on calcite precipitated in coseismic extension fractures in the Loma Blanca normal fault zone, Rio Grande rift, NM, USA, constrain earthquake recurrence intervals from 150-565 ka. This is the longest direct record of seismicity documented for a fault in any tectonic environment. Combined U-Th and stable isotope analyses of these calcite veins define 13 distinct earthquake events. These data show that for more than 400 ka the Loma Blanca fault produced earthquakes with a mean recurrence interval of 40 ± 7 ka. The coefficient of variation for these events is 0.40, indicating strongly periodic seismicity consistent with a time-dependent model of earthquake recurrence. Stochastic statistical analyses further validate the inference that earthquake behavior on the Loma Blanca was time-dependent. The time-dependent nature of these earthquakes suggests that the seismic cycle was fundamentally controlled by a stress renewal process. However, this periodic cycle was punctuated by an episode of clustered seismicity at 430 ka. Recurrence intervals within the earthquake cluster were as low as 5-11 ka. Breccia veins formed during this episode exhibit carbon isotope signatures consistent with having formed through pronounced degassing of a CO2 charged brine during post-failure, fault-localized fluid migration. The 40 ka periodicity of the long-term earthquake record of the Loma Blanca fault is similar in magnitude to recurrence intervals documented through paleoseismic studies of other normal faults in the Rio Grande rift and Basin and Range Province. We propose that it represents a background rate of failure in intraplate extension. The short-term, clustered seismicity that occurred on the fault records an interruption of the stress renewal process, likely by elevated fluid pressure in deeper structural levels of the fault, consistent with fault-valve behavior. The relationship between recurrence interval and inferred fluid degassing suggests that pore fluid pressure

  17. Intracrystalline deformation of calcite

    NARCIS (Netherlands)

    de Bresser, Hans


    It is well established from observations on natural calcite tectonites that intracrystalline plastic mechanisms are important during the deformation of calcite rocks in nature. In this thesis, new data are presented on fundamental aspects of deformation behaviour of calcite under conditions where 'd

  18. Varicose Veins (United States)

    Varicose veins are swollen, twisted veins that you can see just under the skin. They usually occur in ... of the body. Hemorrhoids are a type of varicose vein. Your veins have one-way valves that help ...

  19. Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping (United States)

    McNamara, David D.; Lister, Aaron; Prior, Dave J.


    Fractures play an important role as fluid flow pathways in geothermal resources hosted in indurated greywacke basement of the Taupo Volcanic Zone, New Zealand, including the Kawerau Geothermal Field. Over time, the permeability of such geothermal reservoirs can be degraded by fracture sealing as minerals deposit out of transported geothermal fluids. Calcite is one such fracture sealing mineral. This study, for the first time, utilises combined data from electron backscatter diffraction and chemical mapping to characterise calcite vein fill morphologies, and gain insight into the mechanisms of calcite fracture sealing in the Kawerau Geothermal Field. Two calcite sealing mechanisms are identified 1) asymmetrical syntaxial growth of calcite, inferred by the presence of single, twinned, calcite crystals spanning the entire fracture width, and 2) 3D, interlocking growth of bladed vein calcite into free space as determined from chemical and crystallographic orientation mapping. This study also identifies other potential uses of combined EBSD and chemical mapping to understand geothermal field evolution including, potentially informing on levels of fluid supersaturation from the study of calcite lattice distortion, and providing information on a reservoir's history of stress, strain, and deformation through investigation of calcite crystal deformation and twinning patterns.

  20. Elastic constants of calcite (United States)

    Peselnick, L.; Robie, R.A.


    The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

  1. Spider Veins (United States)

    ... How to Choose the Best Skin Care Products Spider Veins Treatment Options Learn more about treatment options ... severe venous disease. What you should know about spider veins The exact cause of spider veins is ...

  2. A preliminary study of the calcite beef found in the Cretaceous Jinju Formation, Gyeongsang Basin, South Korea (United States)

    Ha, S.; Chae, Y. U.; Son, M.; Jeong, G. Y.; Paik, I. S.; Lim, H. S.


    The term "beef" refers to fibrous minerals in bedding-parallel veins, where the fibers are approximately perpendicular to the vein margins (Cobbold et al., 2013). It mostly appears within organic-rich black shale layers in sedimentary basin. Although the veins can consist of white gangue minerals, such as calcite, gypsum, or quartz, the commonest mineral in the fibers is calcite. According to the worldwide localities of calcite beef compiled by Cobbold et al (2012), they concentrated in some areas, especially around the Atlantic Ocean. However, they have been rarely reported in the western Pacific margin, except Australia and New Zealand. Recently, calcite beefs have been found in the Cretaceous Jinju Formation, Gyeongsang Basin, Korea. As far as we know, this is the first report of calcite beef in Korea. The lacustrine Jinju Formation is about 1,200 m thick, and made up mainly of lacustrine dark grey to black mudstones. In the study area, calcite beefs were commonly found in the organic-rich black shale layers. The vein thickness is anywhere between a few millimeters to maximum 3 centimeters, and their length ranges from a few centimeters to several tens of meters. The interval between successive veins is from a few centimeters to about 1 meter. Most of them occur parallel to the bedding planes, although some of them are developed along fault planes or within deformed layers. In case of relatively thick beefs, the center of veins often shows a dark grey to black central median line, defined by fine-grained calcite grains, fluid inclusion lines, or wall rock particles. Based on the orientation of fibrous calcite, they can be divided into two types: straight and sigmoidal types. The fibrous calcites are thought to have been symmetrically grown from the median lines to top and bottom of wall rock. The formation mechanism of horizontal fractures, and the formation temperature of beefs in the study area remain as a matter to be studied further.

  3. U and sr isotopes in ground water and calcite, yucca mountain, nevada: evidence against upwelling water. (United States)

    Stuckless, J S; Peterman, Z E; Muhs, D R


    Hydrogenic calcite and opaline silica deposits in fault zones at Yucca Mountain, Nevada, have created considerable public and scientific controversy because of the possible development of a high-level nuclear waste repository at this location. Strontium and uranium isotopic compositions of hydrogenic materials were used to test whether the veins could have formed by upwelling of deep-seated waters. The vein deposits are isotopically distinct from ground water in the two aquifers that underlie Yucca Mountain, indicating that the calcite could not have precipitated from ground water. The data are consistent with a surficial origin for the hydrogenic deposits.

  4. Interactions between cadmium and calcite


    Van der Weijden, R.D.


    The thesis is composed of five chapters, some of which have been published or have been accepted for publication. The contents in some of the chapters may therefore slightly overlap, also because the subjects are closely related. The first two chapters focus mostly on the sorption of Cd on calcite, whereas the next two chapters are devoted to calcite growth and Cd incorporation during growth. In the fifth and final chapter, Cd sorption and incorporation is studied in an environment where calc...

  5. Evolution and the Calcite Eye Lens

    CERN Document Server

    Williams, Vernon L


    Calcite is a uniaxial, birefringent crystal, which in its optically transparent form, has been used for animal eye lenses, the trilobite being one such animal. Because of the calcite birefringence there is a difficulty in using calcite as a lens. When the propagation direction of incoming light is not exactly on the c-axis, the mages blur. In this paper, calcite blurring is evaluated, and the non-blurring by a crystallin eye lens is compared to a calcite one.

  6. Interactions between cadmium and calcite

    NARCIS (Netherlands)

    van der Weijden, R.D.


    The thesis is composed of five chapters, some of which have been published or have been accepted for publication. The contents in some of the chapters may therefore slightly overlap, also because the subjects are closely related. The first two chapters focus mostly on the sorption of Cd on calcite,

  7. Veining Failure and Hydraulic Fracturing in Shales (United States)

    Mighani, S.; Sondergeld, C. H.; Rai, C. S.


    During the hydraulic fracturing, the pressurized fluid creates new fractures and reactivates existing natural fractures forming a highly conductive Stimulated Reservoir Volume (SRV) around the borehole. We extend the previous work on Lyons sandstone and pyrophyllite to anisotropic shale from the Wolfcamp formation. We divide the rock anisotropy into two groups: a) conventional and b) unconventional (shaly) anisotropy. X-ray Computed Tomography (CT), compressional velocity anisotropy, and SEM analysis are used to identify three causes of anisotropy: bedding planes, clay lamination, and calcite veins. Calcite vein is a subsequently filled with calcite bonded weakly to the matrix. Velocity anisotropy and visual observations demonstrate the calcite filled veins to be mostly subparallel to the fabric direction. Brazilian tests are carried out to observe the fracture initiation and propagation under tension. High speed photography (frame rate 300,000 frame/sec) was used to capture the failure. Strain gauges and Acoustic Emission (AE) sensors recorded the deformation leading up to and during failure. SEM imaging and surface profilometry were employed to study the post-failure fracture system and failed surface topology. Fracture permeability was measured as a function of effective stress. Brazilian tests on small disks containing a centered single vein revealed the shear strength of the veins. We interpret the strain data and number, frequency, and amplitude of AE events which are correlated well with the observed fracture process zone, surface roughness, and permeability. The unpropped fracture has enhanced permeability by two orders of magnitude. The observed anisotropic tensile failure seems to have a universal trend with a minimum strength occurring at 15o orientation with respect to the loading axis. The veins at 15o orientation with respect to the loading axis were easily activated at 30% of the original failure load. The measured strength of the vein is as low as 6

  8. Varicose vein - noninvasive treatment (United States)

    Sclerotherapy; Laser therapy - varicose veins; Radiofrequency vein ablation; Endovenous thermal ablation; Ambulatory phlebectomy; Transilluminated power phlebotomy; Endovenous laser ablation; Varicose vein ...

  9. Shock-induced devolatilization of calcite (United States)

    Boslough, M. B.; Ahrens, T. J.; Vizgirda, J.; Becker, R. H.; Epstein, S.


    Experimental measurements of the release adiabats by Vizgirda (1981) indicate that substantial vaporization takes place upon release from shock pressures of 37 GPa for calcite and 14 GPa for aragonite. The present investigation includes the first controlled partial vaporization experiments on calcite. The experiments were conducted to test the predictions of the release adiabat experiments. The quantities of the gaseous species produced from shocked calcite and their carbon and oxygen isotopic compositions were determined, and the shock-induced effect on the Mn(2+) electron spin resonance spectrum in the shock-recovered calcite was observed. On the basis of the obtained results, it is concluded that shock stresses at the 17-18 GPa level give rise to volatilization of 0.03-0.3 (mole) percent of calcite to CO2 and CO. The devolatilization of calcite occurs at low pressure at significantly lower entropy densities than predicted on the basis of thermodynamic continuum models.

  10. Varicose vein stripping (United States)

    ... vein stripping; Venous reflux - vein stripping; Venous ulcer - veins Images Circulatory system References American Family Physician. Management of varicose veins. . ...

  11. Deep Vein Thrombosis (United States)

    Deep vein thrombosis, or DVT, is a blood clot that forms in a vein deep in the body. Most deep vein ... the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a serious problem ...

  12. Microstructural analysis of calcite-filled fractures inherited from basement structures, southern Ontario, Canada: long term instability of the craton? (United States)

    Spalding, Jennifer; Schneider, David


    Intra-cratonic regions are generally characterized by tectonic stability and low seismicity. In southern Ontario, Canada, moderate levels of seismicity have been recorded over the last few decades reaching magnitudes of 5 MN, indicating that the geosphere is not as stable as predicted. The stratigraphy of the region consists of Ordovician limestone with a thickness of ~200 m that unconformably overlays the Mesoproterozoic crystalline Grenville Province. Subsequent tectonism including repeated Paleozoic orogenies and rifting along the east coast of North America has reactivated Proterozoic structures that have propagated into the overlying carbonate platform forming mesoscopic-scale brittle structures. Exposed along the shores of Lake Ontario are decameter-scale fracture zones, with a fracture spacing of 0.5 to 10 meters. The dominant fracture set trends E-W, and often forms conjugate sets with less prominent NNE-oriented fractures. More locally, an older NW-oriented fracture set is cross cut by the E-W and NNE oriented fractures. Regionally, there have been six directions of maximum horizontal stress in southern Ontario since the Precambrian, with the current orientation of maximum stress oriented ENE as a consequence of far field Atlantic ridge-push forces generated at distant plate boundaries. Calcite mineralization along fractured surfaces locally form sub-horizontal slickenside fabrics which are covered by a layer of euhedral calcite crystals, suggesting that fracture dilation (and fluid flow) occurred after fracture slip to allow the growth of calcite crystals. Due to the proximity of the carbonate units to the crystalline basement, we expect the calcitic veins to be enriched in rare earth elements and are presently conducting geochemical analyses. The calcite veins and surfaces vary from 2.5 cm to 1 mm thicknesses, often with larger calcite crystals in the center of the vein and smaller crystals at the vein boundaries, likely representing nucleation on small

  13. The Influence of Exotic Calcite on the Mechanical Behavior of Quartz Bearing Fault Gouge (United States)

    Carpenter, B. M.; Di Stefano, G.; Collettini, C.


    The interseismic recovery of frictional strength is a fundamental part of the seismic cycle. This restrengthening, and related phenomena, plays a key role in determining the stability and mode of tectonic faulting. Recent experimental data has shown that gouge mineralogy has a strong influence on the rate of frictional healing, with calcite-dominated gouges showing the highest rates. Combining these data with widespread observations of calcite as cement or veins in non-carbonate hosted faults, indicates that the presence of calcite within a fault gouge could play an important role in shallow- and mid-crustal earthquakes. We report on laboratory experiments designed to explore the mechanical behavior of quartz/calcite mixtures as a means to better understand the evolution of fault behavior in faults where carbonate materials are present. We sheared mixtures of powdered Carrara marble (>98% CaCO3) and disaggregated Ottawa sand (99.8% SiO2) at constant normal stress of 5 MPa under saturated conditions at room temperature. We performed slide-hold-slide tests, 1-3,000 seconds, and velocity stepping tests, 0.1-1000 μm/s, to measure the amount of frictional healing and velocity dependence of friction respectively. Small subsets of experiments were conducted at different boundary conditions. Preliminary results show that the presence of calcite in quartz-based fault gouge has a hardening effect, both in overall frictional strength, where the strength of our mixtures increases with increasing calcite content, and in single experiments, where mixtures with low percentages of calcite show a consistent strain-hardening trend. We also observe that the rates of frictional healing and creep relaxation increase with increasing calcite content. Finally, our results show that the addition of as little as 2.5% calcite within a fault gouge results in a 30% increase in the rate of frictional healing, with further increases in calcite content resulting in larger increases in the rate

  14. Calcite biomineralization in coccoliths: Evidence from atomic force microscopy (AFM)

    DEFF Research Database (Denmark)

    Henriksen, Karen; Stipp, S.L.S.


    geochemistry, crystal orientation, coccolith function, biomineralization, biological calcite, atomic force microscopy......geochemistry, crystal orientation, coccolith function, biomineralization, biological calcite, atomic force microscopy...

  15. Portal Vein Thrombosis


    Hakan Demirci


    Portal vein thrombosis is an important cause of presinusoidal portal hypertension. Portal vein thrombosis commonly occurs in patient with cirrhosis, malignancy and prothrombotic states. Patients with acute portal vein thrombosis have immediate onset. Patients with chronic portal vein thrombosis have developed portal hypertension and cavernous portal transformation. Portal vein thrombosis is diagnosed with doppler ultrasound, computed tomography and magnetic resonance imaging. Therapy with low...

  16. Focus on Varicose Veins (United States)

    ... veins, which are the visible purple or greenish-blue veins that appear in our legs. Spider veins or teleangiectesias are tiny veins that you ... reduce leg swelling and decrease the risk of blood clots. Prescription ... sclerosing solution into spider, reticular or varicose veins. This is a minimally ...

  17. Spider Vein Removal (United States)

    Spider veins: How are they removed? I have spider veins on my legs. What options are available ... M.D. Several options are available to remove spider veins — thin red lines or weblike networks of ...

  18. Sclerotherapy of Varicose Veins and Spider Veins (United States)

    ... you as to whether the procedure was a technical success when it is completed. Your interventional radiologist ... Varicose Veins) Phlebectomy of Varicose Veins Contrast Materials Anesthesia Safety Sponsored by Please note is ...

  19. Vein Problems Related to Varicose Veins (United States)

    ... telangiectasias. Spider veins involve the capillaries, the smallest blood vessels in the body. Spider veins often appear on the legs and face. They're red or blue and usually look like a spider web or ...

  20. Formation Process and Thermodynamic Poperties of Calcite

    Institute of Scientific and Technical Information of China (English)

    NAN,Zhao-Dong; SHI,Zuo-Yi; QIN,Mei; HOU,Wan-Guo; TAN,Zhi-Cheng


    The fast mixing of aqueous solutions of calcium chloride and sodium carbonate resulted in crystalline forms of vaterite and calcite under vigorous stirring. Then, the vaterite was transformed to pure calcite within about 180 min.The crystalline forms all grew with experimental time increase. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction spectroscopy (XRD) techniques were employed to characterize the as-prepared samples. The heat capacity of the stable as-synthesized calcite was determined by means of an adiabatic calorimeter from 80 to 390 K. The thermodynamic functions of the calcite were derived based on the relationships among the thermodynamic functions and the function of the measured heat capacity with respect to temperature.

  1. Interaction of alcohols with the calcite surface

    DEFF Research Database (Denmark)

    Bovet, Nicolas Emile; Yang, Mingjun; Javadi, Meshkat Sadat


    A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water...

  2. Diffusion of Ca and Mg in Calcite

    Energy Technology Data Exchange (ETDEWEB)

    Cygan, R.T.; Fisler, D.K.


    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  3. Portal Vein Thrombosis

    Directory of Open Access Journals (Sweden)

    Hakan Demirci


    Full Text Available Portal vein thrombosis is an important cause of presinusoidal portal hypertension. Portal vein thrombosis commonly occurs in patient with cirrhosis, malignancy and prothrombotic states. Patients with acute portal vein thrombosis have immediate onset. Patients with chronic portal vein thrombosis have developed portal hypertension and cavernous portal transformation. Portal vein thrombosis is diagnosed with doppler ultrasound, computed tomography and magnetic resonance imaging. Therapy with low molecular weight heparin achieves recanalization in more than half of acute cases.

  4. Do organic ligands affect calcite dissolution rates? (United States)

    Oelkers, Eric H.; Golubev, Sergey V.; Pokrovsky, Oleg S.; Bénézeth, Pascale


    Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO 2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA 4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.

  5. The coordination of Mg in foraminiferal calcite (United States)

    Branson, Oscar; Redfern, Simon A. T.; Tyliszczak, Tolek; Sadekov, Aleksey; Langer, Gerald; Kimoto, Katsunori; Elderfield, Henry


    The Mg/Ca ratio of foraminiferal calcite is a widely accepted and applied empirical proxy for ocean temperature. The analysis of foraminifera preserved in ocean sediments has been instrumental in developing our understanding of global climate, but the mechanisms behind the proxy are largely unknown. Analogies have been drawn to the inorganic precipitation of calcite, where the endothermic substitution of Mg for Ca is favoured at higher temperatures. However, evidence suggests that foraminiferal Mg incorporation may be more complex: foraminiferal magnesium is highly heterogeneous at the sub-micron scale, and high Mg areas coincide with elevated concentrations of organic molecules, Na, S and other trace elements. Fundamentally, the incorporation mode of Mg in foraminifera is unknown. Here we show that Mg is uniformly substituted for Ca within the calcite mineral lattice. The consistency of Mg-specific X-ray spectra gathered from nano-scale regions across the shell (‘test’) reveals that the coordination of Mg is uniform. The similarity of these spectra to that produced by dolomite shows that Mg is present in an octahedral coordination, ideally substituted for Ca in a calcite crystal structure. This demonstrates that Mg is heterogeneous in concentration, but not in structure. The degree of this uniformity implies the action of a continuous Mg incorporation mechanism, and therefore calcification mechanism, across these compositional bands in foraminifera. This constitutes a fundamental step towards a mechanistic understanding of foraminiferal calcification processes and the incorporation of calcite-bound palaeoenvironment proxies, such as Mg.

  6. Source of lead and mineralizing brines for rossie-type Pb-Zn veins in the Frontenac axis area, New York ( USA). (United States)

    Ayuso, Robert; Foley, Nora K.; Brown, C. Erwin


    Veins composed mainly of calcite and some galena, sphalerite, fluorite, and other minerals are widespread in the Frontenac axis area of New York and Ontario. In New York, the veins (Fig. 1) occur mainly west and northwest of Gouverneur (Brown, 1983). The veins, mined in the 1800s for lead, were first described by Emmons (1838). Smyth (1903) called these the "Rossie lead veins," a name now used locally for all veins of this type. Similar veins in southeastern Ontario were described by Uglow (1916) and Sangster (1970).

  7. Calcite Biohybrids as Microenvironment for Stem Cells

    Directory of Open Access Journals (Sweden)

    Razi Vago


    Full Text Available A new type of composite 3D biomaterial that provides extracellular cues that govern the differentiation processes of mesenchymal stem cells (MSCs has been developed. In the present study, we evaluated the chondrogenecity of a biohybrid composed of a calcium carbonate scaffold in its calcite polymorph and hyaluronic acid (HA. The source of the calcite scaffolding is an exoskeleton of a sea barnacle Tetraclita rifotincta (T. rifotincta, Pilsbry (1916. The combination of a calcium carbonate-based bioactive scaffold with a natural polymeric hydrogel is designed to mimic the organic-mineral composite of developing bone by providing a fine-tuned microenvironment. The results indicate that the calcite-HA interface creates a suitable microenvironment for the chondrogenic differentiation of MSCs, and therefore, the biohybrid may provide a tool for tissue-engineered cartilage.

  8. Acidization of shales with calcite cemented fractures (United States)

    Kwiatkowski, Kamil; Szymczak, Piotr; Jarosiński, Marek


    Investigation of cores drilled from shale formations reveals a relatively large number of calcite-cemented fractures. Usually such fractures are reactivated during fracking and can contribute considerably to the permeability of the resulting fracture network. However, calcite coating on their surfaces effectively excludes them from production. Dissolution of the calcite cement by acidic fluids is investigated numerically with focus on the evolution of fracture morphology. Available surface area, breakthrough time, and reactant penetration length are calculated. Natural fractures in cores from Pomeranian shale formation (northern Poland) were analyzed and classified. Representative fractures are relatively thin (0.1 mm), flat and completely sealed with calcite. Next, the morphology evolution of reactivated natural fractures treated with low-pH fluids has been simulated numerically under various operating conditions. Depth-averaged equations for fracture flow and reactant transport has been solved by finite-difference method coupled with sparse-matrix solver. Transport-limited dissolution has been considered, which corresponds to the treatment with strong acids, such as HCl. Calcite coating in reactivated natural fractures dissolves in a highly non-homogeneous manner - a positive feedback between fluid transport and calcite dissolution leads to the spontaneous formation of wormhole-like patterns, in which most of the flow is focused. The wormholes carry reactive fluids deeper inside the system, which dramatically increases the range of the treatment. Non-uniformity of the dissolution patterns provides a way of retaining the fracture permeability even in the absence of the proppant, since the less dissolved regions will act as supports to keep more dissolved regions open. Evolution of fracture morphology is shown to depend strongly on the thickness of calcite layer - the thicker the coating the more pronounced wormholes are observed. However the interaction between

  9. Calcite Twinning in the Ordovician Martinsburg Formation, Delaware Water Gap, New Jersey, USA: Implications for Cleavage Formation and Tectonic Shortening in the Appalachian Piedmont Province

    Directory of Open Access Journals (Sweden)

    John P. Craddock


    Full Text Available A traverse across the Stone Church syncline in the Ordovician Martinsburg turbidites reveals an axial planar cleavage (N40°E, SE dips in regional thrust-related folds (N40°E, shallow plunges and five phases of sparry calcite. Calcite fillings are bedding-parallel, cleavage-parallel, and one vein set cross-cuts both earlier phases; the youngest calcite filling is a bedding-parallel fault gouge that crosscuts the cleavage and preserves top-down-to-the-southeast normal fault kinematics. Calcite veins unique to disharmonically-folded calcareous siltstones (Maxwell, 1962 were also analyzed. Stable isotopic analysis (O, C of all of the calcite phases indicates a uniform fluid source (δ13C −2.0, δ18O −13.3 VPDB and, potentially, a similar precipitation and mechanical twinning age. The twinning strains (n = 1341; average Δσ = −32 MPa; average ε1 = −2.9% in the calcite suite are consistent with SE-NW thrust shortening, and sub-horizontal shortening perpendicular to evolving axial planar cleavage planes in the Stone Church syncline. Calcareous siltstone layers within the Martinsburg Fm. turbidites share concordant bedding planes and are unique, chemically (XRF, but folded and cleaved differently than the surrounding clay-rich Martinsburg turbidites. Neither sediment type yielded detrital zircons. Electron backscatter X-ray diffraction (EBSD and calcite twinning results in a folded calcareous siltstone layer preserving a layer-normal SE-NW shortening strain and Lattice Preferred Orientation (LPO. Shortening axes for the five-phase calcite suite trends ~N40°W, consistent with tectonic transport associated with crystalline nappe emplacement of the Reading Prong within the Piedmont province.

  10. Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas. (United States)

    Wilkinson, Bruce H.


    Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

  11. Portal Vein Thrombosis

    Directory of Open Access Journals (Sweden)

    Ronny Cohen


    Full Text Available Portal vein thrombosis (PVT is the blockage or narrowing of the portal vein by a thrombus. It is relatively rare and has been linked with the presence of an underlying liver disease or prothrombotic disorders. We present a case of a young male who presented with vague abdominal symptoms for approximately one week. Imaging revealed the presence of multiple nonocclusive thrombi involving the right portal vein, the splenic vein, and the left renal vein, as well as complete occlusion of the left portal vein and the superior mesenteric vein. We discuss pathogenesis, clinical presentation, and management of both acute and chronic thrombosis. The presence of PVT should be considered as a clue for prothrombotic disorders, liver disease, and other local and general factors that must be carefully investigated. It is hoped that this case report will help increase awareness of the complexity associated with portal vein thrombosis among the medical community.

  12. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NARCIS (Netherlands)

    Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.


    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rat

  13. High-Magnesian Calcite Mesocrystals : A Coordination Chemistry Approach

    NARCIS (Netherlands)

    Lenders, Jos J. M.; Dey, Archan; Bomans, Paul H. H.; Spielmann, Jan; Hendrix, Marco M. R. M.; de With, Gijsbertus; Meldrum, Fiona C.; Harder, Sjoerd; Sommerdijk, Nico A. J. M.


    While biogenic calcites frequently contain appreciable levels of magnesium, the pathways leading to such high concentrations remain unclear. The production of high-magnesian calcites in vitro is highly challenging, because Mg-free aragonite, rather than calcite, is the favored product in the presenc

  14. in situ Calcite Precipitation for Contaminant Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Yoshiko Fujita; Robert W. Smith


    in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita ( (Idaho National Laboratory, Idaho Falls, Idaho, USA) Robert W. Smith (University of Idaho-Idaho Falls, Idaho Falls, Idaho, USA) Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide strontium-90, is co-precipitation in calcite. Calcite, a common mineral in the arid western U.S., can form solid solutions with trace metals. The rate of trace metal incorporation is susceptible to manipulation using either abiotic or biotic means. We have previously demonstrated that increasing the calcite precipitation rate by stimulating the activity of urea hydrolyzing microorganisms can result in significantly enhanced Sr uptake. Urea hydrolysis causes the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity, and also by liberating the reactive cations from the aquifer matrix via exchange reactions involving the ammonium ion derived from urea: H2NCONH2 + 3H2O ? 2NH4+ + HCO3- + OH- urea hydrolysis >X:2Ca + 2NH4+ ? 2>X:NH4 + Ca2+ ion exchange Ca2+ + HCO3- + OH- ? CaCO3(s) + H2O calcite precipitation where >X: is a cation exchange site on the aquifer matrix. This contaminant immobilization approach has several attractive features. Urea hydrolysis is catalyzed by the urease enzyme, which is produced by many indigenous subsurface microorganisms. Addition of foreign microbes is unnecessary. In turn the involvement of the native microbes and the consequent in situ generation of reactive components in the aqueous phase (e.g., carbonate and Ca or Sr) can allow dissemination of the reaction over a larger volume and/or farther away from an amendment injection point, as compared to direct addition of the reactants at

  15. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation (United States)

    Reddy, Michael M.


    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10-4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10-4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  16. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation (United States)

    Reddy, Michael M.


    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  17. Removal of organic magnesium in coccolithophore calcite (United States)

    Blanco-Ameijeiras, S.; Lebrato, M.; Stoll, H. M.; Iglesias-Rodriguez, M. D.; Méndez-Vicente, A.; Sett, S.; Müller, M. N.; Oschlies, A.; Schulz, K. G.


    Coccolithophore calcite refers to the plates of calcium carbonate (CaCO3) produced by the calcifying phytoplankton, coccolithophores. The empirical study of the elemental composition has a great potential in the development of paleoproxies. However, the difficulties to separate coccolithophore carbonates from organic phases hamper the investigation of coccoliths magnesium to calcium ratios (Mg/Ca) in biogeochemical studies. Magnesium (Mg) is found in organic molecules in the cells at concentrations up to 400 times higher than in inorganically precipitated calcite in present-day seawater. The aim of this study was to optimize a reliable procedure for organic Mg removal from coccolithophore samples to ensure reproducibility in measurements of inorganic Mg in calcite. Two baseline methods comprising organic matter oxidations with (1) bleach and (2) hydrogen peroxide (H2O2) were tested on synthetic pellets, prepared by mixing reagent grade CaCO3 with organic matter from the non-calcifying marine algae Chlorella autotrophica and measured with an ICP-AES (inductively coupled plasma-atomic emission spectrometer). Our results show that treatments with a reductive solution [using hydroxylamine-hydrochloride (NH2OH·HCl + NH4OH)] followed by three consecutive oxidations (using H2O2) yielded the best cleaning efficiencies, removing >99% of organic Mg in 24 h. P/Ca and Fe/Ca were used as indicators for organic contamination in the treated material. The optimized protocol was tested in dried coccolithophore pellets from batch cultures of Emiliania huxleyi, Calcidiscus leptoporus and Gephyrocapsa oceanica. Mg/Ca of treated coccolithophores were 0.151 ± 0.018, 0.220 ± 0.040, and 0.064 ± 0.023 mmol/mol, respectively. Comparison with Mg/Ca literature coccolith values, suggests a tight dependence on modern seawater Mg/Ca, which changes as a consequence of different seawater origins (protocol applicable to field and laboratory studies of trace elemental composition in

  18. Atomistic simulations of calcium uranyl(VI) carbonate adsorption on calcite and stepped-calcite surfaces. (United States)

    Doudou, Slimane; Vaughan, David J; Livens, Francis R; Burton, Neil A


    Adsorption of actinyl ions onto mineral surfaces is one of the main mechanisms that control the migration of these ions in environmental systems. Here, we present computational classical molecular dynamics (MD) simulations to investigate the behavior of U(VI) in contact with different calcite surfaces. The calcium-uranyl-carbonate [Ca(2)UO(2)(CO(3))(3)] species is shown to display both inner- and outer-sphere adsorption to the flat {101̅4} and the stepped {314̅8} and {31̅2̅16} planes of calcite. Free energy calculations, using the umbrella sampling method, are employed to simulate adsorption paths of the same uranyl species on the different calcite surfaces under aqueous condition. Outer-sphere adsorption is found to dominate over inner-sphere adsorption because of the high free energy barrier of removing a uranyl-carbonate interaction and replacing it with a new uranyl-surface interaction. An important binding mode is proposed involving a single vicinal water monolayer between the surface and the sorbed complex. From the free energy profiles of the different calcite surfaces, the uranyl complex was also found to adsorb preferentially on the acute-stepped {314̅8} face of calcite, in agreement with experiment.

  19. [Right ovarian vein syndrome]. (United States)

    Arvis, G


    Right ovarian vein syndrome is revealed in pregnancy by right lumbar pains, and even by nephritic colics. It results from a congenital malposition of the right ovarian vein, which presses the right ureter on the external iliac artery. Diagnosis is by intravenous urography and retrograde ureteral pyelography. If pain persists despite treatment by analgesics, it may be necessary to place a double-J catheter, and to operate after delivery to ligate the ovarian vein.

  20. Postpartum renal vein thrombosis. (United States)

    Rubens, D; Sterns, R H; Segal, A J


    Renal vein thrombosis in adults is usually a complication of the nephrotic syndrome. Rarely, it has been reported in nonnephrotic women postpartum. The thrombosis may be a complication of the hypercoagulable state associated with both the nephrotic syndrome and pregnancy. Two postpartum patients with renal vein thrombosis and no prior history of renal disease are reported here. Neither patient had heavy proteinuria. In both cases, pyelonephritis was suspected clinically and the diagnosis of renal vein thrombosis was first suggested and confirmed by radiologic examination. Renal vein thrombosis should be considered in women presenting postpartum with flank pain.

  1. Stable isotope variations in the Quaternary epithermal calcite-fluorite deposit at Monte delle Fate near Cerveteri (Latium, central Italy) (United States)

    Masi, U.; O'Neil, J.R.


    Carbon, oxygen and hydrogen isotope variations have been measured in samples from the epithermal fluorite vein deposit at Monte delle Fate, Latium. The ranges in ?? 13C and ??18O of calcite are -1.3 to 3.4 and 9.5 to 17.3, respectively. ??D values of water extracted from fluid inclusions are -49 to -39 for calcite and -41 to -34 for fluorite. Fluid inclusion filling temperatures (225??-240??C) and salinites (3.75) are nearly the same for both fluorite and sparry calcite. An elongated form of calcite, of minor abundance, precipitated at lower temperatures. The data indicate that (1) the CO2 involved in the mineralization was provided by the local marine limestones, (2) the waters were meteoric in origin and underwent an 18O shift of ??? 10 permil by exchange with marine country rocks, and (3) all geochemical features can be explained by the action of two hydrothermal fluids. Hot brines recently discovered in the Cesano geothermal area, 30 km to the east, have temperatures and some chemical characteristics similar to the hydrothermal fluids at Monte delle Fate. ?? 1980 Springer-Verlag.

  2. Fracture calcites at Olkiluoto. Evidence from quaternary infills for palaeohydrogeology

    Energy Technology Data Exchange (ETDEWEB)

    Gehoer, S.; Kaerki, A.; Taikina-aho, O. [Kivitieto Oy (Finland); Karhu, J. [Helsinki Univ. (Finland); Loefman, J. [VTT Processes, Espoo (Finland); Pitkaenen, P. [VTT Building and Transport, Espoo (Finland); Ruotsalainen, P. [TUKES, Helsinki (Finland)


    Recently formed secondary minerals, predominantly calcite, occur in varying amounts as fracture infills, and the calcite types, their chemical compositions and isotope ratios reflect the compositions and physicochemical factors of the groundwater system in which they were formed. Fluid inclusions trapped in calcites give direct evidence of trapping temperatures and past salinities and of the chemical compositions of the palaeo fluids. A wide range of mineralogical and geochemical examinations were carried out within the EQUIP project to examine features of this kind. The fracture calcites at the Olkiluoto site are of various origins and represent several textural types. The exact number of calcite-producing events is unknown, but the duration of the period that was appropriate for the precipitation of low temperature calcite is estimated to have exceeded 1000 Ma. Thus the number of genetically related calcite units is assumed to be considerable. This study was focused on the petrogenesis of calcites crystallized in fractures of high water conductivity during the latest stages of geological evolution. The majority of these late stage calcites form physically homogeneous, scaly layers, and in a few cases thin layers composed of idiomorphic crystals. Chemically these are almost stoichiometric calcites (CaCO{sub 3}). The MnO content may exceed 1%, while the amounts of other elements present are minor, although the trace element concentrations, particularly those of large ionic trace elements, can be used as distinguishing features for the recognition of individual precipitates representing different calcite generations. Evidence from fluid inclusions, or more correctly from the absence of these in the late stage calcites, can be interpreted as an indication of slow rates of crystallization under cool conditions. Many chemical variables, e.g. oxygen isotope ratios, demonstrate an equilibrium between the latest calcites and water similar to the present groundwater. Older

  3. The origin of carbon isotope vital effects in coccolith calcite (United States)

    McClelland, H. L. O.; Bruggeman, J.; Hermoso, M.; Rickaby, R. E. M.


    Calcite microfossils are widely used to study climate and oceanography in Earth's geological past. Coccoliths, readily preserved calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have formed a significant fraction of marine sediments since the Late Triassic. However, unlike the shells of foraminifera, their zooplankton counterparts, coccoliths remain underused in palaeo-reconstructions. Precipitated in an intracellular chemical and isotopic microenvironment, coccolith calcite exhibits large and enigmatic departures from the isotopic composition of abiogenic calcite, known as vital effects. Here we show that the calcification to carbon fixation ratio determines whether coccolith calcite is isotopically heavier or lighter than abiogenic calcite, and that the size of the deviation is determined by the degree of carbon utilization. We discuss the theoretical potential for, and current limitations of, coccolith-based CO2 paleobarometry, that may eventually facilitate use of the ubiquitous and geologically extensive sedimentary archive.

  4. The origin of carbon isotope vital effects in coccolith calcite (United States)

    McClelland, H. L. O.; Bruggeman, J.; Hermoso, M.; Rickaby, R. E. M.


    Calcite microfossils are widely used to study climate and oceanography in Earth's geological past. Coccoliths, readily preserved calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have formed a significant fraction of marine sediments since the Late Triassic. However, unlike the shells of foraminifera, their zooplankton counterparts, coccoliths remain underused in palaeo-reconstructions. Precipitated in an intracellular chemical and isotopic microenvironment, coccolith calcite exhibits large and enigmatic departures from the isotopic composition of abiogenic calcite, known as vital effects. Here we show that the calcification to carbon fixation ratio determines whether coccolith calcite is isotopically heavier or lighter than abiogenic calcite, and that the size of the deviation is determined by the degree of carbon utilization. We discuss the theoretical potential for, and current limitations of, coccolith-based CO2 paleobarometry, that may eventually facilitate use of the ubiquitous and geologically extensive sedimentary archive. PMID:28262764

  5. Origin of calcite in the glacigenic Virttaankangas complex

    Directory of Open Access Journals (Sweden)

    Nina M. Kortelainen


    Full Text Available Groundwaters of the glacigenic Virttaankangas complex in southern Finland are characterized by high pH values ranging up to 9.5. These values are significantly higher than those observed in silicate-rich shallow groundwater formations in crystalline bedrock areas. TheVirttaankangas sediments were discovered to contain small amounts of fine grained, dispersed calcite, which has a high tendency to increase the pH of local groundwaters. The primary goal of this study was to determine the mode of occurrence of calcite and to identifyits sources. The mineralogy of the glacigenic Virttaankangas complex was studied using material from 21 sediment drill cores. Fine-grained calcite is present in trace amounts (<< 1.4 % in the glaciofluvial and glaciolacustrine depositional units of the Virttaankangas complex. The topmost littoral sands were practically devoid of calcite. The isotope records of carbon and oxygen, the angular morphology of the grains and the uniform dispersion of calcite in the complex suggest a clastic origin for calcite, with no evidence for in-situ precipitation. In order to constrain the source of calcite, the isotopic composition of carbon and oxygen in five calcite samples was compared to the isotopic data from five carbonate rock erratics and eight crystalline bedrock samples from the region. Based on carbon and oxygen isotope ratios and chemical compositions, the dispersed calcite grains of the Virttaankangas complex appear to have been derived from the Mesoproterozoic Satakunta Formation, some 30 km NW from the Virttaankangas area. In sandstone, calcite is predominantly present as diagenetic cement in grain interspaces, concretions and interlayers. The source of detrital calcite was unexpected, as prior to this study the Satakunta sandstone hasnot been known to contain calcite.

  6. Internal vein texture and vein evolution of the epithermal Shila-Paula district, southern Peru (United States)

    Chauvet, Alain; Bailly, Laurent; André, Anne-Sylvie; Monié, Patrick; Cassard, Daniel; Tajada, Fernando Llosa; Vargas, Juan Rosas; Tuduri, Johann


    The epithermal Shila-Paula Au-Ag district is characterized by numerous veins hosted in Tertiary volcanic rocks of the Western Cordillera (southern Peru). Field studies of the ore bodies reveal a systematic association of a main E-W vein with secondary N55-60°W veins—two directions that are also reflected by the orientation of fluid-inclusion planes in quartz crystals of the host rock. In areas where this pattern is not recognized, such as the Apacheta sector, vein emplacement seems to have been guided by regional N40°E and N40°W fractures. Two main vein-filling stages are identified. stage 1 is a quartz-adularia-pyrite-galena-sphalerite-chalcopyrite-electrum-Mn silicate-carbonate assemblage that fills the main E-W veins. stage 2, which contains most of the precious-metal mineralization, is divided into pre-bonanza and bonanza substages. The pre-bonanza substage consists of a quartz-adularia-carbonate assemblage that is observed within the secondary N45-60°W veins, in veinlets that cut the stage 1 assemblage, and in final open-space fillings. The two latter structures are finally filled by the bonanza substage characterized by a Fe-poor sphalerite-chalcopyrite-pyrite-galena-tennantite-tetrahedrite-polybasite-pearceite-electrum assemblage. The ore in the main veins is systematically brecciated, whereas the ore in the secondary veins and geodes is characteristic of open-space crystallization. Microthermometric measurements on sphalerite from both stages and on quartz and calcite from stage 2 indicate a salinity range of 0 to 15.5 wt% NaCl equivalent and homogenization temperatures bracketed between 200 and 330°C. Secondary CO2-, N2- and H2S-bearing fluid inclusions are also identified. The age of vein emplacement, based on 40Ar/39Ar ages obtained on adularia of different veins, is estimated at around 11 Ma, with some overlap between adularia of stage 1 (11.4±0.4 Ma) and of stage 2 (10.8±0.3 Ma). A three-phase tectonic model has been constructed to explain the

  7. What Causes Varicose Veins? (United States)

    ... blood flow, and thin, stretched walls. The middle image shows where varicose veins might appear in a leg. Figure A shows ... blood flow, and thin, stretched walls. The middle image shows where varicose veins might appear in a leg. Older age or ...

  8. Synthesis and characterization of spider silk calcite composite

    Directory of Open Access Journals (Sweden)

    Svetlana Dmitrović


    Full Text Available Spider silk poses excellent mechanical properties, tenacity and elasticity and it has been used as a template for calcite mineralization to improve load bearing strength of osteoconductive calcite. The samples were obtained by mimicking biomineralization for five days in order to follow formation and growth of calcite on the surface of spider silk. Crystal phase was detected by XRD and FTIR spectroscopy. Microstructure, crystal size and its morphology were studied by means of FESEM. After two days of processing, pure calcite phase was obtained, and a size of the formed crystals increased with prolongation of biomineralization.

  9. Biogenic and synthetic high magnesium calcite - a review. (United States)

    Long, Xia; Ma, Yurong; Qi, Limin


    Systematic studies on the Mg distributions, the crystal orientations, the formation mechanisms and the mechanical properties of biogenic high-Mg calcites in different marine organisms were summarized in detail in this review. The high-Mg calcites in the hard tissues of marine organisms mentioned generally own a few common features as follows. Firstly, the Mg distribution is not uniform in most of the minerals. Secondly, high-Mg calcite biominerals are usually composed of nanoparticles that own almost the same crystallographic orientations and thus they behave like single crystals or mesocrystals. Thirdly, the formation of thermodynamically unstable high-Mg calcites in marine organisms under mild conditions is affected by three key factors, that is, the formation of amorphous calcium (magnesium) carbonate precursor, the control of polymorph via biomolecules and the high Mg/Ca ratios in modern sea. Lastly, the existence of Mg ions in the Mg-containing calcite may improve the mechanical properties of biogenic minerals. Furthermore, the key progress in the synthesis of high-Mg calcites in the laboratory based on the formation mechanisms of the biogenic high-Mg calcites was reviewed. Many researchers have realized the synthesis of high-Mg calcites in the laboratory under ambient conditions with the help of intermediate amorphous phase, mixed solvents, organic/inorganic surfaces and soluble additives. Studies on the structural analysis and formation mechanisms of thermodynamically unstable biogenic high-Mg calcite minerals may shed light on the preparation of functional materials with enhanced mechanical properties.

  10. Spectroscopic characterization of natural calcite minerals. (United States)

    Gunasekaran, S; Anbalagan, G


    The FT-IR, FT-Raman, NMR spectral data of ten different limestone samples have been compared. FT-IR and FT-Raman spectral data show that calcium carbonate in limestone, principally in the form of calcite, as identified by its main absorption bands at 1426, 1092, 876 and 712 cm(-1). The sharp diffractions at the d-spacings, 3.0348, 1.9166 and 1.8796 confirm the presence of calcite structure and the calculated lattice parameters are: a=4.9781 A, c=17.1188 A. The range of 13C chemical shifts for different limestone samples is very small, varying from 198.38 to 198.42 ppm. The observed chemical shifts are consistent with the identical C-O bonding in different limestone samples. 27Al MAS NMR spectra of the samples exhibit a central line at 1 ppm and another line at 60 ppm corresponding to octahedral and tetrahedral Al ions, respectively. The five component resonances were observed in 29Si MAS NMR spectrum of limestone and these resonances were assigned to Si (4 Al), Si (3 Al), Si (2 Al), Si (1 Al) and Si (0 Al) from low field to high field.

  11. CO2 outburst events in relation to seismicity: Constraints from microscale geochronology, geochemistry of late Quaternary vein carbonates, SW Turkey (United States)

    Ünal-İmer, Ezgi; Uysal, I. Tonguç; Zhao, Jian-Xin; Işık, Veysel; Shulmeister, James; İmer, Ali; Feng, Yue-Xing


    Vein and breccia carbonates precipitated in a highly fractured/faulted carbonate bedrock in SW Turkey were investigated through high-resolution U-series geochronology, microstructural and geochemical studies including C-O-Sr isotope and rare-earth element and yttrium (REY) analyses. Petrographical observations and geochronological data are interpreted as evidence that the calcite veins formed through a crack-seal mechanism, mostly accompanied/initiated by intensive hydraulic fracturing of the host limestone in response to high-pressure fluids, which is manifested by multi-stage breccia deposits. Microscale U-series dates (272.6-20.5 kyr) and geochemical compositions of the vein/breccia samples provide information on the timing and mechanism of the vein formation and identify the source of CO2-bearing fluids responsible for the carbonate precipitation. δ18OVPDB and δ13CVPDB values of the calcite veins range between -5.9 and -1.7‰, and -10.6 and -4.6‰, respectively. The isotopic compositions of the veins show highly fluctuating values as calcite grew successively perpendicular to vein walls, which, in combination with microstructural and geochronological constraints, are interpreted to reflect episodic CO2 degassing events associated with seismic and aseismic deformation. Oxygen and Sr isotope compositions (δ18OVPDB: -5.9 to -1.7‰; 87Sr/86Sr: 0.7082 to 0.7085) together with REY concentrations indicate deep infiltration of meteoric waters with various degrees of interactions mostly with the host limestone and siliciclastic parts of the basement rocks. Oxygen and carbon isotope compositions suggest CO2 degassing through intensive limestone dissolution. While majority of the veins display similar Post-Archaean Australian Shale (PAAS)-normalised REY variations, some of the veins show positive EuPAAS anomalies, which could be indicative of contributions from a deeply derived, heated, and reduced fluid component, giving rise to multiple fluid sources for the

  12. The Coordination of Mg in Foraminiferal Calcite (United States)

    Branson, O.; Redfern, S. A.; Tyliszczak, T.; Sadekov, A.; Langer, G.; Elderfield, H.


    The Mg/Ca ratio in calcite shells ('tests') of foraminifera is an empirical ocean temperature proxy widely used to interpret palaeoclimates. We explore the distribution and local environment of Mg in foram tests using STXM and NEXAFS spectroscopy to test the fundamental assumptions behind the proxy, and shed light on the mechanisms underpinning this vital oceanographic tool. Throughout the development of the Mg/Ca proxy, it has been assumed that Mg in foraminifera tests substitutes directly into the calcite lattice (1). This assumption is based on XRD analyses of various high-Mg biogenic carbonates, where Mg concentrations are manifest in the shifted position of diffraction peaks (2, 3). The extrapolation of this trend to foraminiferal calcite links the proxy to inorganic precipitation experiments, and provides a theoretical mechanistic framework to understand the link between Mg/Ca and temperature: the substitution of Mg is endothermic, and favoured at higher temperatures. However, the concentration of Mg in most foraminifera (0-10 mmol/mol Mg/Ca) is below the detection limit of XRD methods, and the analogy to inorganic systems has not been explicitly tested. Electron microprobe (4-6), LA-ICP-MS (7) and high-resolution nanoSIMS mapping (Sadekov, unpub.) of foraminifera tests have revealed the presence of high 'trace element' bands running in plane with the test surface, enriched in Mg, Sr, S, organic molecules and other trace elements. This emphasises a key question highlighted by Dodd (1) when the proxy was still in its infancy: how is Mg incorporated into mineral skeletons? By direct substitution into the calcite lattice, interstitially in a separate distinct mineral phase, or associated with organic compounds? We address this fundamental question using scanning transmission X-ray microscopy (STXM) and X-ray absorption spectroscopy at ALS beamline 11.0.2 to examine the distribution and local atomic environment of Mg in two contrasting species of foraminifera

  13. Kinematics of fibrous vein growth: insights from stable isotopes and trace element data (United States)

    Fischer, M. P.; Lefticariu, L.; Romanek, C.; Perry, E. C.


    Veins are important recorders of thermal, hydrological, structural, and geochemical conditions during deformation. Fibrous or bladed veins are particularly useful, because the mineral fibers are believed to grow continuously or episodically over what may be a significant geologic time period. Thus, individual mineral fibers document the complex, dynamic changes occurring coeval with vein growth and mineral precipitation. Geochemical and structural analyses have been used to constrain the kinematic history of a bed-parallel fibrous calcite vein from the Upper Jurassic La Casita Formation, Sierra Madre Oriental, Mexico. The La Casita Formation, correlative with the Smackover Formation of the northern US Gulf Coast, consists of shale and is part of a sedimentary succession that unconformably overlies evaporites of the Minas Viejas Formation. The fibrous vein examined in this study was taken from the backlimb of the frontal fold of the Monterrey salient near Saltillo. Optical petrographic observation reveals that the calcite fibers have blade or tapering lath shapes with widths from 0.1-1.0 mm. Other minerals present in the vein are pyrite, gypsum, bitumen, and iron oxides. High-resolution, closely spaced stable isotope and elemental analyses were carried out along five traverses across the vein width. The d18O values vary in a narrow range, with an average value of +20.8 permil (VSMOW). The d13C values increase systematically along the fibers, from the walls of the vein toward the suture plane. In all five traverses, the d13C increase is relatively constant, with lower values next to the vein wall (+1.2 to +1.6 permil PDB) and higher values along the suture line (+3.6 to +4.1 permil PDB). The vein minerals, fibrous calcite and accessory pyrite, are interpreted to be the products of high temperature reactions between light hydrocarbons and dissolved sulfate, known as thermochemical sulfate reduction (TSR). Reactants such as light hydrocarbons and products such as CO2

  14. Alteration and vein mineralization, Ladwig uranium mine, Jefferson County, Colorado (United States)

    Wallace, Alan R.


    Uranium ore at the Ladwig mine, Jefferson County, Colo., occurs in steeply dipping, northwest-striking faults and related fractures with a carbonate-adularia assemblage that forms in altered wallrocks and fills veins. The faults occur between large intrusive pegmatites and garnetiferous gneisses of Precambrian age, and were reactivated as the result of the early Paleocene uplift of the Front Range foothills. Mineralization in the deposit includes both wallrock alteration and vein filling. Alteration was intense but local, and chiefly involved the carbonatization of mafic minerals in the wallrocks. Felsic minerals in the wallrocks are relatively unaltered. The veins are filled with an adularia-pitchblende-carbonate assemblage with minor related sulfides and coffinite. Many of the iron-bearing carbonates in both the alteration and vein assemblages have been altered to hematite. The mineralization and alteration are believed to have formed in response to initially high amounts of CO2 and the subsequent release of dissolved CO2 by boiling or effervescence. Uranium, carried in a dicarbonate complex, was precipitated directly as pitchblende when the CO2 was released. The expulsion of H+ during boiling created a net oxidizing environment which oxidized the iron-bearing carbonates. Late stage calcite and sulfides were deposited in existing voids in the veins.

  15. Geochemical and isotope aspects of calcite deposits and calcitic marbles hosts mineralizations, Serra do Carumbe, Vale do Ribeira, Parana state, Brazil; Aspectos geoquimicos e isotopicos das mineralizacoes de calcita e marmores calciticos encaixantes, Serra do Carumbe, Vale do Ribeira, estado do Parana

    Energy Technology Data Exchange (ETDEWEB)

    Venusso, Gerson Caetano; Andrade e Silva, Antonio C. Gondim de, E-mail:, E-mail: [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil)


    The calcite deposits and the calcitic marbles hosts occur in Serra do Carumbe, in the Vale do Ribeira region, Parana State, were studied in their geochemical and isotopic aspects viewing the gathering of information about their genesis and economical use. The calcite deposits are constituted by veins and lenses, being three of them concordant and one discordant in relation to the S{sub 0} from the hosting marbles. In these deposits four main types of calcite were recognized: rombohedrical, fibrous, banded and microcrystalline. The calcite reveal themselves having high purity, with CaO concentration above 55.30% and MgO below 0.42%. The lithogeochemical study of the marbles sequence was conducted in various suites revealing an uniformity in their composition, with high values of CaO (above 46.92%) in relation to the MgO values (below 3,37%), what favors their use for cement manufacture, except in sectors that suffered fault influences, where the marbles are impure (siliceous, magnesian, ferruginous and aluminous). Regarding their trace elements content, the hosting calcitic marbles have higher concentrations than the calcite, in the elements Sr, B, Ba and Mg, what makes evident their different formation environments. The δ{sup 13}C values from calcite range from –9,02 to –12,24 ‰ , referring to PDB, while the values δ{sup 18}O range from 24,48 to 25,23 ‰, referring to SMOW; meanwhile, for the calcitic marbles, the δ{sup 13}C values range from –4,03 to 1,42‰ and of δ{sup 18}O range from 20,71 to 23,00 ‰. The high δ{sup 18}O values would indicate enrichment referring to the interaction of the calcite's generator fluid with the carbonatic host rock. The δ{sup 13}C values indicate origin from hydrothermal solution for the calcite, although they would not allow to conclude if their sources would be superficial or profound. As for the hosting calcitic marbles, the isotopic values indicate genesis from pre-cambrian marine limestone. (author)

  16. Congenital preduodenal portal vein

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Jin; Hwang, Mi Soo; Huh, Young Soo; Park, Bok Hwan [College of Medicine, Youngnam University, Gyeongsan (Korea, Republic of)


    Congenital preduodenal portal vein, first reported by Knight in 1921, is an extremely rare congenital anomaly in which the portal vein passes anteriorly to the duodenum rather than posteriorly in its normal location. It is of surgical significance because it may cause difficulties in operations involving the gall bladder, biliary duct, or duodenum. Recently, we experienced 2 cases of preduodenal portal vein. One was found during surgical exploration for the diagnosis and correction of malrotation of the bowels and the other in a 3 day-old male newborn associated with dextrocardia, situs inversus, and duodenal obstruction by diaphragm. We report these 2 cases with a review of the literature.

  17. Umbilical and portal vein calcification following umbilical vein catheterization

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, K.; Fendel, H.; Hartl, M.


    Calcifications of the umbilical vein and intrahepatic branches of the portal vein developed in a newborn who had inserted an umbilical vein catheter for 11 days postnatally. The calcified intrahepatic portal veins can still be demonstrated sonographically at the age of three years, whereby these calcifications were no longer detectable radiologically. (orig.).

  18. Sorption and desorption of arsenate and arsenite on calcite

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Diederik Jan; Jakobsen, Rasmus


    The adsorption and desorption of arsenate (As(V)) and arsenite (As(111)) oil calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic...

  19. Single-contact pressure solution creep on calcite monocrystals

    CERN Document Server

    Zubtsov, Sergei; Gratier, Jean-Pierre; Dysthe, Dag; Traskine, Vladimir


    Pressure solution creep rates and interface structures have been measured by two methods on calcite single crystals. In the first kind of experiments, calcite monocrystals were indented at 40 degrees C for six weeks using ceramic indenters under stresses in the 50-200 MPa range in a saturated solution of calcite and in a calcite-saturated aqueous solution of NH4Cl. The deformation (depth of the hole below the indenter) is measured ex-situ at the end of the experiment. In the second type of experiment, calcite monocrystals were indented by spherical glass indenters for 200 hours under stresses in the 0-100 MPa range at room temperature in a saturated aqueous solution of calcite. The displacement of the indenter was continuously recorded using a specially constructed differential dilatometer. The experiments conducted in a calcite-saturated aqueous solution of NH4Cl show an enhanced indentation rate owing to the fairly high solubility of calcite in this solution. In contrast, the experiments conducted in a calc...

  20. The role of silicate surfaces on calcite precipitation kinetics

    DEFF Research Database (Denmark)

    Stockmann, Gabrielle J.; Wolff-Boenisch, Domenik; Bovet, Nicolas Emile


    The aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate. Calcite was precipitated at 25°C from supersaturated aqueous solutions in the presence of seeds of either calcite or one of six silicate materials: augite, enstatite......, labradorite, olivine, basaltic glass and peridotite rock. Calcite saturation was achieved by mixing a CaCl2-rich aqueous solution with a NaHCO3-Na2CO3 aqueous buffer in mixed-flow reactors containing 0.5-2g of mineral, rock, or glass seeds. This led to an inlet fluid calcite saturation index of 0.6 and a p......H equal to 9.1. Although the inlet fluid composition, flow rate, and temperature were identical for all experiments, the onset of calcite precipitation depended on the identity of the seeds present in the reactor. Calcite precipitated instantaneously and at a constant rate in the presence of calcite...

  1. Emission polarization study on quartz and calcite. (United States)

    Vincent, R. K.


    Calculation of the spectral emission polarization of quartz and calcite polished plates for observation angles of 20 and 70 deg by the substitution of complex index of refraction values for each mineral into Fresnel's equations. The emission polarization is shown to be quite wavelength-dependent, demonstrating that selected narrow or medium-width spectral bands exhibit a significantly higher percentage of polarization than a broad spectral band for these two minerals. Field measurements with a broadband infrared radiometer yield polarizations on the order of 2% for a coarse-grained granite rock and beach sand (both quartz-rich). This implies that a more sensitive detector with a selected medium-width filter may be capable of measuring emission polarization accurately enough to make this parameter useful as a remote sensing tool for discrimination among rocks on the basis of texture.

  2. Deep vein thrombosis. (United States)

    Bandyopadhyay, Gargi; Roy, Subesha Basu; Haldar, Swaraj; Bhattacharya, Rabindra


    Occlusive clot formation in the veins causes venous thrombosis, the site most common in the deep veins of leg, called deep vein thrombosis. The clot can block blood flow and when it breaks off, called an embolism which in turn can damage the vital organs. Venous thrombosis occurs via three mechanisms ie, Virchow's triad. The mechanisms are decreased flow rate of blood, damage to the blood vessel wall and an increased tendency of the blood to clot. There are several factors which can increase a person's risk for deep vein thrombosis. The symptoms of deep vein thrombosis in the legs are pain, swelling and redness of the part. One variety of venous thrombosis is phlegmasia alba dolens where the leg becomes pale and cool. Investigations include Doppler ultrasound examination of the limb, D-dimer blood test, plethysmography of the legs, x-rays to show vein in the affected area (venography). Hospitalisation is necessary in some cases with some risk factors. The mainstream of treatment is with anticoagulants, mostly low molecular weight heparin for 6 months. Deep venous thrombosis is a rising problem. Early diagnosis and treatment is associated with a good prognosis.

  3. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface

    NARCIS (Netherlands)

    Wolthers, M.; Di Tommaso, D.; Du, Z.; de Leeuw, N.H.


    Calcite–water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Fir

  4. Mesenteric vein thrombosis: CT identification

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, A.; Korobkin, M.; Silverman, P.M.; Dunnick, N.R.; Kelvin, F.M.


    Superior mesenteric vein thrombosis was identified on computed tomographic scans in six patients. In each case, contrast-enhanced scans showed a high-density superior mesenteric vein wall surrounding a central filling defect. Four fo the six patients had isolated superior mesenteric vein thrombosis. A fifth patient had associated portal vein and splenic vein thrombosis, and the sixth patient had associated portal vein and inferior vena cava thrombosis. One of the six patients had acute ischemic bowel disease. The other five patients did not have acute ischemic bowel symptoms associated with their venous occlusion. This study defines the computed tomographic appearance of mesenteric vein thrombosis.

  5. Geometry of calcite cemented zones in shallow marine sandstones

    Energy Technology Data Exchange (ETDEWEB)

    Walderhaug, O.; Prestholm, E.; Oexnevad, I.E.I.


    In offshore oil production, tightly cemented calcite zones often form impermeable barriers to fluid flow an so adversely affect reservoir performance. Based on recent breakthroughs in the theory of the formation of calcite cemented zones, the project discussed in this paper was concerned with (1) Performing outcrop studies in order to increase the existing database on the geometry of calcite cemented zones, (2) Extending and refining methods of predicting the geometry of cored calcite cemented zones, and (3) Applying and illustrating the use of these methods by studying calcite cementation in shallow marine reservoir sandstones on the Norwegian shelf. The paper presents results from field work and applies these results and the criteria for recognizing geometrical forms of calcite cementation in cores to the Ula Formation of the Ula Field and the Rannoch Formation of the Gullfax Field. The results from the core and outcrop studies are integrated in a tentative identification key for cored calcite cemented zones. The work is part of PROFIT (Program for Research On Field oriented Improved recovery Technology), a research project conducted by RF - Rogaland Research in 1991-1994. 32 refs., 10 figs., 2 tabs.

  6. Molecular ordering of ethanol at the calcite surface

    DEFF Research Database (Denmark)

    Pasarín, I. S.; Yang, M.; Bovet, Nicolas Emile


    -743 ] and molecular dynamics (MD) modeling [ Yang, M., Stipp, S. L. S., and Harding, J. H.Cryst. Growth Des. 2008, 8 (11), 4066-4074 ], have suggested that OH functional groups control polysaccharide attachment. The purpose of this work was to characterize, using X-ray reflectivity (XR) combined with molecular...... dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH 3-CH2-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol...

  7. Grain coarsening of calcite: Fundamental mechanisms and biogenic inhibition

    DEFF Research Database (Denmark)

    Schultz, Logan Nicholas

    In a saturated solution, submicrometer calcite (CaCO3) crystals recrystallize and coarsen to minimize surface area. The thermodynamic driving force is described by the Gibbs-Thomson equation, but the rates and mechanism are poorly understood. Calcite grain coarsening has many implications...... in industry and nature, but the specific focus of this research project was to understand how small, biogenic calcite particles in chalk have resisted grain coarsening for over 60 million years in saturated reservoir fluids. A new method was developed to produce pure calcite powder that has submicrometer...... coarsening – small grains coarsen by aggregation at high temperatures, followed by Ostwald ripening. Alginate, a model for the acidic polysaccharides produced by coccolithiphores, inhibited coarsening at a steady rate. A Pseudomonas aeruginosa biofilm preserved particles for at least 60 days before...

  8. Paleoclimatic and paleohydrologic records from secondary calcite: Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, J.F.; Stuckless, J.S.; Moscati, R.J. [Geological Survey, Denver, CO (United States); Vaniman, D.T. [Los Alamos National Lab., NM (United States)


    Stable isotope analyses of calcite and opal, fluid inclusion formation conditions and gas compositions, Sr isotope ratios, and REE compositions all support formation of secondary calcite in the unsaturated zone of Yucca Mountain from infiltration of surface-derived (and soil zone buffered) waters of meteoric origin. Detailed sampling of growth-banding preserved by the secondary calcite should provide a record of past variations in the stable isotope chemistry of these infiltrating waters, and, hence, of precipitation at Yucca Mountain, i.e., a proxy of past climate at Yucca Mountain. The precision of this record depends on how well it can be dated. The distribution and texture of secondary calcite occurrences, if mapped in careful detail from existing bore hole samples and underground workings (as exposures become accessible), could provide a time/space map of fracture and fault unsaturated-zone ground water flow-paths during past wetter climates which might prevail in the future with change in climate.

  9. Calcite crystal growth rate inhibition by polycarboxylic acids (United States)

    Reddy, M.M.; Hoch, A.R.


    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  10. An AFM study of calcite dissolution in concentrated electrolyte solutions (United States)

    Ruiz Agudo, E.; Putnis, C. V.; Putnis, A.; Rodriguez-Navarro, C.


    Calcite-solution interactions are of a paramount importance in a range of processes such as the removal of heavy metals, carbon dioxide sequestration, landscape modeling, weathering of building stone and biomineralization. Water in contact with minerals often carries significant amounts of solutes; additionally, their concentration may vary due to evaporation and condensation. It is well known that calcite dissolution is affected dramatically by the presence of such solutes. Here we present investigations on the dissolution of calcite in the presence of different electrolytes. Both bulk (batch reactors) experiments and nanoscale (in situ AFM) techniques are used to study the dissolution of calcite in a range of solutions containing alkaly cations balanced by halide anions. Previous works have indicated that the ionic strength has little influence in calcite dissolution rates measured from bulk experiments (Pokrovsky et al. 2005; Glendhill and Morse, 2004). Contrary to these results, our quantitative analyses of AFM observations show an enhancement of the calcite dissolution rate with increasing electrolyte concentration. Such an effect is concentration-dependent and it is most evident in concentrated solutions. AFM experiments have been carried out in a fluid cell using calcite cleavage surfaces in contact with solutions of simple salts of the alkaly metals and halides at different undersaturations with respect to calcite to try to specify the effect of the ionic strength on etch pit spreading rate and calcite dissolution rate. These results show that the presence of soluble salts may critically affect the weathering of carbonate rocks in nature as well as the decay of carbonate stone in built cultural heritage. References: Pokrosky, O.S.; Golubev, S.V.; Schott, J. Dissolution kinetics of calcite, dolomite and magnesite at 25°C and 0 to 50 atm pCO2. Chemical Geology, 2005, 217 (3-4) 239-255. Glendhill, D.K.; Morse, J.W. Dissolution kinetics of calcite in Na

  11. Thermoluminescence glow curve of {gamma}-irradiated calcite

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.D.; Ingotombi, S. [Manipur Univ. (India). Dept. of Physics


    The trapping parameters, namely the activation energy E, frequency factor s and b order of kinetics of the thermoluminescence (TL) peaks of calcites (brown and colourless varieties) irradiated with 4.08 kGy of {gamma}-rays, are determined using the least-squares curve-fitting technique. The electron lifetime {tau} of the peaks of calcite are calculated in order to estimate the upper limit of their utility in TL dating. (author).

  12. Selective Flotation of Calcite from Fluorite: A Novel Reagent Schedule

    Directory of Open Access Journals (Sweden)

    Zhiyong Gao


    Full Text Available Fluorite is an important strategic mineral. In general, fluorite ores will contain a certain amount of calcite gangue mineral. Thus, they need to be separated from each other. For an economic separation, a reverse flotation process is used to float calcite gangue from fluorite. However, little information on the separation is available. In this study, a novel reagent schedule using citric acid (CA as the depressant, sodium fluoride (NaF as the regulator and sulfoleic acid (SOA as the collector, was developed to separate calcite from fluorite. The results demonstrated a high selectivity for the flotation of calcite from fluorite using this new reagent schedule. The best selective separation for a single mineral and mixed binary minerals was obtained when 200 mg/L of NaF, 50 mg/L of CA, and 6 mg/L of SOA were used at pH 9. In addition, a batch flotation experiment was carried out using a run-of-mine feed material. Selective separation was achieved with 85.18% calcite removal while only 11.2% of fluorite was lost. An attempt was made to understand the effect of the new reagent schedule on the flotation of calcite. The results from both microflotation and bench scale flotation demonstrated a great potential for industrial application using this novel reagent schedule to upgrade fluorite ore.

  13. Deep Vein Thrombosis

    Centers for Disease Control (CDC) Podcasts


    This podcast discusses the risk for deep vein thrombosis in long-distance travelers and ways to minimize that risk.  Created: 4/5/2012 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 4/5/2012.

  14. Retinal vein occlusion (United States)

    ... decrease the risk of retinal vein occlusion. These measures include: Eating a low-fat diet Getting regular exercise Maintaining an ideal weight Not smoking Aspirin or other blood thinners may help prevent blockages in the other eye. Controlling diabetes may ...

  15. The vein collar

    DEFF Research Database (Denmark)

    Lundgren, F; Schroeder, Torben Veith


    Randomized studies evaluating the effect of a vein collar at the distal anastomosis of PTFE-grafts show conflicting results. The study of the Joint Vascular Research Group (JVRG) of UK found improved primary patency while the Scandinavian Miller Collar Study (SCAMICOS) found neither any effect...

  16. Deep Vein Thrombosis

    African Journals Online (AJOL)


    Il s'agissait de la main et les recherches en ligne. Des termes ..... Cerrato D, Ariano G, and Fiacchino F : Deep vein ... Surg 1988; 75: 1053–7. 19. Salzman ... Alikhan R, Cohen AT, Combe S, Samama .... Kakkar AK, Williamson RCN. Thrombo.

  17. [Ovarian vein syndrome]. (United States)

    Ferrero Doria, R; Guzmán Valls, P; López Alba, J; Tomás Ros, M; Rico Galiano, J L; Fontana Compiano, L O


    The Ovarian Vein Syndrome has been the subject of controversy ever since first described as such by Clark in 1964. This is an uncommon entity within urologic sings and symptoms which appears as a recurrent nephritic colic coinciding with menstruation or during the immediately preceding days. The authors review a clinical case from our Urology Service, including some considerations on the case.

  18. Cucumber vein yellowing virus (United States)

    Cucurbits are an important crop of temperate, subtropical and tropical regions of the world. Cucumber vein yellowing virus (CVYV) is a major viral pathogen of cucurbits. This chapter provides an overview of the biology of CVYV and the disease it causes....

  19. Squash vein yellowing virus (United States)

    Cucurbits are an important crop of temperate, subtropical and tropical regions of the world. Squash vein yellowing virus (SqVYV) is a major viral pathogen of cucurbits. This chapter provides an overview of the biology of SqVYV and the disease it causes....

  20. Calcite Farming at Hollow Ridge Cave: Calibrating Net Rainfall and Cave Microclimate to Dripwater and Calcite Chemical Variability (United States)

    Tremaine, D. M.; Kilgore, B. P.; Froelich, P. N.


    Stable isotope (δ18O and δ13C) and trace element records in cave speleothems are often interpreted as climate changes in rainfall amount or source, cave air temperature, overlying vegetation and atmospheric pCO2. However, these records are difficult to verify without in situ calibration of changes in cave microclimate (e.g., net rainfall, interior ventilation changes) to contemporaneous variations in dripwater and speleothem chemistry. In this study at Hollow Ridge Cave (HRC) in Marianna, Florida (USA), cave dripwater, bedrock, and modern calcite (farmed in situ) were collected in conjunction with continuous cave air pCO2, temperature, barometric pressure, relative humidity, radon-222 activity, airflow velocity and direction, rainfall amount, and drip rate data [1]. We analyzed rain and dripwater δD and δ18O, dripwater Ca2+, pH, δ13C and TCO2, cave air pCO2 and δ13C, and farmed calcite δ18O and δ13C to examine the relationships among rainwater isotopic composition, cave air ventilation, cave air temperature, calcite growth rate and seasonal timing, and calcite isotopic composition. Farmed calcite δ13C decreases linearly with distance from the front entrance to the interior of the cave during all seasons, with a maximum entrance-to-interior gradient of Δδ13C = -7‰ . A whole-cave "Hendy test" at distributed contemporaneous farming sites reveals that ventilation induces a +1.9 ± 0.96‰ δ13C offset between calcite precipitated in a ventilation flow path and out of flow paths. Farmed calcite δ18O exhibits a +0.82 ± 0.24‰ offset from values predicted by both theoretical calcite-water calculations and by laboratory-grown calcite [2]. Unlike calcite δ13C, oxygen isotopes show no ventilation effects and are a function only of temperature. Combining our data with other speleothem studies, we find a new empirical relationship for cave-specific water-calcite oxygen isotope fractionation across a range of temperatures and cave environments: 1000 ln α = 16

  1. Mn content of reservoir calcite cement: A novel inorganic geotracer of secondary petroleum migration in the tectonically complex Junggar Basin (NW China)

    Institute of Scientific and Technical Information of China (English)

    CAO; Jian; HU; WenXuan; YAO; SuPing; ZHANG; YiJie; WANG; XuLong; ZHANG; YueQian; TANG; Yong; SHI; XinPu


    Electronic probe microanalysis (EPMA) results of reservoir calcite cement from fourteen core samples in the Junggar Basin show that Mn-content varies largely between different samples from below the detect limitation to 4.14%, while it displays a generally good correlation with oil-gas shows. This, therefore, likely indicates that concentration of the Mn-content of the calcite cement has a close relation to the intensity of petroleum fluid charging during hydrocarbon secondary migration. In order to assess this hypothesis, oxygen and strontium isotopic measurements on sixteen calcite veins host in source sequences were carried out to investigate the feature of the oil-source petroleum fluid. Analytical results imply that during hydrocarbon generation and migration, deep hot fluid has dissolved volcanic minerals interlined between mudstone source rocks. As Mn is a kind of typical trace element enriched in volcanic rocks, it is reasonable to conclude that the petroleum fluid formed in the source sequences would be Mn-rich. Consequently, calcite cements precipitated from such Mn-rich petroleum fluid would be Mn-rich accordingly. Due to the geologic chromatographic effect during migration along reservoir rocks, the decreasing of the Mn-content of the reservoir calcite cements indicates the migration direction. Then, this novel geotracer was further successfully applied in the study of hydrocarbon migration in the Junggar Basin in combination with organic geochemical analyses during the hydrocarbon migration. The Mn content of the reservoir calcite cement appears promising as a novel inorganic geotracer for the petroleum migration. This paper represents a search for novel indicators of secondary petroleum migration in tectonically complex basins based on fundamentals of the reservoir fluid-rock interactions.

  2. Endovenous treatments for varicose veins

    NARCIS (Netherlands)

    R.R. van den Bos (Renate)


    textabstractEndovenous treatment is currently one of the most frequently used methods for treating varicose veins in the Netherlands. Varicose veins are tortuous and enlarged veins due to weakening in the vein’s wall or valves. They are manifestations of chronic venous disease (CVD), which may lead

  3. Fingerprinting stress: Stylolite and calcite twinning paleopiezometry revealing the complexity of progressive stress patterns during folding—The case of the Monte Nero anticline in the Apennines, Italy (United States)

    Beaudoin, Nicolas; Koehn, Daniel; Lacombe, Olivier; Lecouty, Alexandre; Billi, Andrea; Aharonov, Einat; Parlangeau, Camille


    In this study we show for the first time how quantitative stress estimates can be derived by combining calcite twinning and stylolite roughness stress fingerprinting techniques in a fold-and-thrust belt. First, we present a new method that gives access to stress inversion using tectonic stylolites without access to the stylolite surface and compare results with calcite twin inversion. Second, we use our new approach to present a high-resolution deformation and stress history that affected Meso-Cenozoic limestone strata in the Monte Nero Anticline during its late Miocene-Pliocene growth in the Umbria-Marche Arcuate Ridge (northern Apennines, Italy). In this area an extensive stylolite-joint/vein network developed during layer-parallel shortening (LPS), as well as during and after folding. Stress fingerprinting illustrates how stress in the sedimentary strata did build up prior to folding during LPS. The stress regime oscillated between strike slip and compressional during LPS before ultimately becoming strike slip again during late stage fold tightening. Our case study shows that high-resolution stress fingerprinting is possible and that this novel method can be used to unravel temporal relationships that relate to local variations of regional orogenic stresses. Beyond regional implications, this study validates our approach as a new powerful toolbox to high-resolution stress fingerprinting in basins and orogens combining joint and vein analysis with sedimentary and tectonic stylolite and calcite twin inversion techniques.

  4. Calcites from Ocean Crust Basalts: Reliable Proxy Archives? (United States)

    Böhm, Florian; Eisenhauer, Anton


    Calcite cements in ocean crust basalts of the deep sea form from mixtures of cold seawater and warm hydrothermal fluids (about 0-70°C). These low temperature alteration (LTA) calcites have recently gained new interest as proxy recorders of seawater composition (Refs. 1-5). Recent LTA calcite reconstructions of the Sr/Ca and Mg/Ca evolution in ocean waters point to considerably lower Sr/Ca and Mg/Ca ratios during the Cretaceous and Paleogene than in the modern ocean. However, diagenetic alteration in contact with the basalt host rock may change the composition of the LTA calcites. For testing the reliability of LTA calcite records of seawater composition multi-proxy approaches are applied: oxygen isotopes indicate precipitation temperatures, strontium isotopes (87Sr/86Sr) and trace elements indicate influences from hydrothermal fluids. Additional information about the influence of basement rocks on LTA calcite composition can be derived from analyses of stable calcium and strontium isotopes (44/40Ca, 88/86Sr). We find low 44/40Ca values for DSDP and ODP sites where the 87Sr/86Sr ratios of LTA calcites indicate basement influence. On the other hand, for some sites the 87Sr/86Sr values inidicate precipitation from pristine seawater, while low 44/40Ca values indicate basement influence. All of these sites are either older than 50 Myr or show calcite precipitation temperatures >50°C. Sites that are younger than 25 Myr and had formation temperatures 50°C significantly higher 88/86Sr values were observed. The calcium isotope results indicate basement influence on LTA calcite composition at temperatures >10°C. Radiogenic strontium isotopes, in contrast, can be used as unequivocal basement influence indicators only at temperatures above 30°C. Below about 20°C 87Sr/86Sr ratios are no reliable indicators of basement influence. All LTA calcites of sites older than 50 Myr formed (or recrystallized) at temperatures >15°C. Low 44/40Ca values indicate that

  5. Geochemical signatures of fluid paleo-transfer in fracture filling calcite from low permeability rock masses: examples taken from Bure's and Tournemire's site in France and northern Switzerland; Signatures geochimiques de paleocirculations aqueuses dans la calcite de remplissage de fracture de massifs argileux peu permeables et de leurs encaissants: exemples pris sur les sites de Bure, Tournemire et Suisse du nord

    Energy Technology Data Exchange (ETDEWEB)

    Lecocq, D


    Fractures in rock masses represent preferential path for fluid transfer and, as such, are the most efficient way for migration of radionuclides at a regional scale. The impact of fracturing on hydrogeological system is a major challenge for underground radioactive waste storage projects. In this context, geochemistry of fracture-filling calcite is used to better understand physical and chemical properties of palaeo-fluids. A new methodology has been developed to analyze Mg, Mn, Fe, Sr and Rare Earth Elements REE (La, Ce, Nd, Sm, Eu, Dy and Yb) in calcite by Secondary Ion Mass Spectrometry. Analyses of calcite crystals have been performed in fractures from Jurassic clays and limestones in France (Bure and Tournemire sites) and northern Switzerland (Mt Terri's tunnel and deep borehole). On each case, several geochemical signatures are observed, according to REE partitioning and Mn and Fe concentrations. In the Bure site, a dependence of calcite geochemistry from fracture host rock has been evidenced. On the other hand, speciation of REE in solution equilibrated with clayey or calcareous rocks at circum-neutral pH (7 to 8) is not significantly influenced by the media: speciation is dominated by carbonate species in both cases and phosphate complexes can modify heavy REE availability in relatively to light REE. These results point out that in fractures in clays, calcite crystallizes at equilibrium with a fluid expulsed during diagenesis from clay minerals, recording the effect of clays and accessory phases. In limestone fractures, calcite records a later event related to the past functioning of the present aquifer, and the fluid has reached equilibrium with the rock minerals. In secondary filling calcite from Toarcian Argilites faults close to Tournemire's tunnel, three successive generations of calcite are observed in an extensive fault, and a fourth in a compressive one. In Aalenian Opalinus Clays veins, comparison between existing isotopic data and Mn, Fe

  6. Defluoridation of drinking water by boiling with brushite and calcite. (United States)

    Larsen, M J; Pearce, E I F


    Existing methods for defluoridating drinking water involve expensive high technology or are slow, inefficient and/or unhygienic. A new method is now suggested, encompassing brushite and calcite suspension followed by boiling. Our aim was to examine the efficiency of the method and the chemical reactions involved. Brushite, 0.3-0.5 g, and an equal weight of calcite were suspended in 1 litre water containing 5-20 ppm fluoride. The suspensions were boiled in an electric kettle, left to cool and the calcium salts to sediment. Solution ion concentrations were determined and sediments were examined by X-ray diffraction. In distilled water initially containing 5, 10 and 20 ppm fluoride the concentration was reduced to 0.06, 0.4 and 5.9 ppm, respectively. Using Aarhus tap water which contained 2.6 mmol/l calcium the final concentrations were 1.2, 2.5 and 7.7 ppm, respectively, and runs without calcite gave results similar to those with calcite. Without boiling the fluoride concentration remained unaltered, as did the brushite and calcite salts, despite occasional agitation by hand. All solutions were supersaturated with respect to fluorapatite and hydroxyapatite and close to saturation with respect to brushite. Boiling produced well-crystallised apatite and traces of calcite, while boiling of brushite alone left a poorly crystallised apatite. We conclude that boiling a brushite/calcite suspension rapidly converts the two salts to apatite which incorporates fluoride if present in solution, and that this process may be exploited to defluoridate drinking water.

  7. On the complex conductivity signatures of calcite precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuxin; Hubbard, Susan; Williams, Kenneth Hurst; Ajo-Franklin, Jonathan


    Calcite is a mineral phase that frequently precipitates during subsurface remediation or geotechnical engineering processes. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soil strengthening. Because induced calcite precipitation is typically quite variable in space and time, monitoring its distribution in the subsurface is a challenge. In this research, we conducted a laboratory column experiment to investigate the potential of complex conductivity as a mean to remotely monitor calcite precipitation. Calcite precipitation was induced in a glass bead (3 mm) packed column through abiotic mixing of CaCl{sub 2} and Na{sub 2}CO{sub 3} solutions. The experiment continued for 12 days with a constant precipitation rate of {approx}0.6 milimole/d. Visual observations and scanning electron microscopy imaging revealed two distinct phases of precipitation: an earlier phase dominated by well distributed, discrete precipitates and a later phase characterized by localized precipitate aggregation and associated pore clogging. Complex conductivity measurements exhibited polarization signals that were characteristic of both phases of calcite precipitation, with the precipitation volume and crystal size controlling the overall polarization magnitude and relaxation time constant. We attribute the observed responses to polarization at the electrical double layer surrounding calcite crystals. Our experiment illustrates the potential of electrical methods for characterizing the distribution and aggregation state of nonconductive minerals like calcite. Advancing our ability to quantify geochemical transformations using such noninvasive methods is expected to facilitate our understanding of complex processes associated with natural subsurface systems as well as processes induced through engineered treatments (such as environmental remediation and carbon sequestration).

  8. Role of Fungi in the Biomineralization of Calcite

    Directory of Open Access Journals (Sweden)

    Saskia Bindschedler


    Full Text Available In the field of microbial biomineralization, much of the scientific attention is focused on processes carried out by prokaryotes, in particular bacteria, even though fungi are also known to be involved in biogeochemical cycles in numerous ways. They are traditionally recognized as key players in organic matter recycling, as nutrient suppliers via mineral weathering, as well as large producers of organic acids such as oxalic acid for instance, an activity leading to the genesis of various metal complexes such as metal-oxalate. Their implications in the transformation of various mineral and metallic compounds has been widely acknowledged during the last decade, however, currently, their contribution to the genesis of a common biomineral, calcite, needs to be more thoroughly documented. Calcite is observed in many ecosystems and plays an essential role in the biogeochemical cycles of both carbon (C and calcium (Ca. It may be physicochemical or biogenic in origin and numerous organisms have been recognized to control or induce its biomineralization. While fungi have often been suspected of being involved in this process in terrestrial environments, only scarce information supports this hypothesis in natural settings. As a result, calcite biomineralization by microbes is still largely attributed to bacteria at present. However, in some terrestrial environments there are particular calcitic habits that have been described as being fungal in origin. In addition to this, several studies dealing with axenic cultures of fungi have demonstrated the ability of fungi to produce calcite. Examples of fungal biomineralization range from induced to organomineralization processes. More examples of calcite biomineralization related to direct fungal activity, or at least to their presence, have been described within the last decade. However, the peculiar mechanisms leading to calcite biomineralization by fungi remain incompletely understood and more research is

  9. Modeling the evolution of complex conductivity during calcite precipitation on glass beads (United States)

    Leroy, Philippe; Li, Shuai; Jougnot, Damien; Revil, André; Wu, Yuxin


    SUMMARYWhen pH and alkalinity increase, calcite frequently precipitates and hence modifies the petrophysical properties of porous media. The complex conductivity method can be used to directly monitor calcite precipitation in porous media because it is sensitive to the evolution of the mineralogy, pore structure and its connectivity. We have developed a mechanistic grain polarization model considering the electrochemical polarization of the Stern and diffuse layer surrounding calcite particles. Our complex conductivity model depends on the surface charge density of the Stern layer and on the electrical potential at the onset of the diffuse layer, which are computed using a basic Stern model of the calcite/water interface. The complex conductivity measurements of Wu et al. (2010) on a column packed with glass beads where calcite precipitation occurs are reproduced by our surface complexation and complex conductivity models. The evolution of the size and shape of calcite particles during the calcite precipitation experiment is estimated by our complex conductivity model. At the early stage of the calcite precipitation experiment, modeled particles sizes increase and calcite particles flatten with time because calcite crystals nucleate at the surface of glass beads and grow into larger calcite grains around glass beads. At the later stage of the calcite precipitation experiment, modeled sizes and cementation exponents of calcite particles decrease with time because large calcite grains aggregate over multiple glass beads, a percolation threshold is achieved, and small and discrete calcite crystals polarize.

  10. Varicosity of the pulmonary veins

    Energy Technology Data Exchange (ETDEWEB)

    Leicher-Dueber, A.; Lindner, P.; Schild, H.; Plewe, G.


    Varicosity of the pulmonary veins is a rare anomaly of the pulmonary vascular system. The varices do not usually change in size over years, do not cause symptoms and need no therapy. However, raised left atrial pressure can cause increase in the diameter of pulmonary vein varices. A case of lung vein varicosity in the right middle and upper lobe associated with coarctation of the aorta and an anomalous upper-middle lobe vein was observed over a period of 10 years. Increase in left atrial pressure (aortic and relative mitral regurgitation) led to enlargement of the pulmonary veins.

  11. Hydrochemical controls on aragonite versus calcite precipitation in cave dripwaters (United States)

    Rossi, Carlos; Lozano, Rafael P.


    Despite the paleoclimatic relevance of primary calcite to aragonite transitions in stalagmites, the relative role of fluid Mg/Ca ratio, supersaturation and CO32- concentration in controlling such transitions is still incompletely understood. Accordingly, we have monitored the hydrochemistry of 50 drips and 8 pools that are currently precipitating calcite and/or aragonite in El Soplao and Torca Ancha Caves (N. Spain), investigating the mineralogy and geochemistry of the CaCO3 precipitates on the corresponding natural speleothem surfaces. The data reveal that, apart from possible substrate effects, dripwater Mg/Ca is the only obvious control on CaCO3 polymorphism in the studied stalagmites and pools, where calcite- and aragonite-precipitating dripwaters are separated by an initial (i.e. at stalactite tips) Mg/Ca threshold at ≈1.1 mol/mol. Within the analyzed ranges of pH (8.2-8.6), CO32- concentration (1-6 mg/L), supersaturation (SIaragonite: 0.08-1.08; SIcalcite: 0.23-1.24), drip rate (0.2-81 drops/min) and dissolved Zn (6-90 μg/L), we observe no unequivocal influence of these parameters on CaCO3 mineralogy. Despite the almost complete overlapping supersaturations of calcite- and aragonite-precipitating waters, the latter are on average less supersaturated because the waters having Mg/Ca above ∼1.1 have mostly achieved such high ratios by previously precipitating calcite. Both calcite and aragonite precipitated at or near oxygen isotopic equilibrium, and Mg incorporation into calcite was consistent with literature-based predictions, indicating that in the studied cases CaCO3 precipitation was not significantly influenced by strong kinetic effects. In the studied cases, the calcites that precipitate at ∼11 °C from dripwaters with initial Mg/Ca approaching ∼1.1 incorporate ∼5 mol% MgCO3, close to the published value above which calcite solubility exceeds aragonite solubility, suggesting that aragonite precipitation in high-relative-humidity caves is

  12. A Raman spectroscopic comparison of calcite and dolomite. (United States)

    Sun, Junmin; Wu, Zeguang; Cheng, Hongfei; Zhang, Zhanjun; Frost, Ray L


    Raman spectroscopy was used to characterize and differentiate the two minerals calcite and dolomite and the bands related to the mineral structure. The (CO3)(2-) group is characterized by four prominent Raman vibrational modes: (a) the symmetric stretching, (b) the asymmetric deformation, (c) asymmetric stretching and (d) symmetric deformation. These vibrational modes of the calcite and dolomite were observed at 1440, 1088, 715 and 278 cm(-1). The significant differences between the minerals calcite and dolomite are observed by Raman spectroscopy. Calcite shows the typical bands observed at 1361, 1047, 715 and 157 cm(-1), and the special bands at 1393, 1098, 1069, 1019, 299, 258 and 176 cm(-1) for dolomite are observed. The difference is explained on the basis of the structure variation of the two minerals. Calcite has a trigonal structure with two molecules per unit cell, and dolomite has a hexagonal structure. This is more likely to cause the splitting and distorting of the carbonate groups. Another cause for the difference is the cation substituting for Mg in the dolomite mineral.

  13. Thermal behavior of calcite as an expansive agent

    Directory of Open Access Journals (Sweden)

    Shahraki B.K.


    Full Text Available In this paper, thermal behavior of calcite as raw material of CaO-based expansive agent was investigated. The products were characterized by using differential thermal analysis (DTA, thermogravimetric analysis (TGA, Fourier transform infrared spectroscopy (FT-IR and X-ray powder diffraction (XRD. DTA curves show that calcite has endothermic peak and impurity affects the onset of reactions. The more the impurity increases, the more energy changes increase. At 800-900°C, calcite was decomposed into solid calcium oxide (CaO and gaseous CO2. Lime (CaO used as the base of expandable material is the ultimate product of heated calcite. The calcium oxide phase, in reaction to water forms portlandite, at an onset temperature of about 900°C was also characterized by the appearance of the FT-IR mode at 867,3424 and 3644 cm-1. XRD results show that quartz impurity in calcite samples at 900°C forms larnite phase (Ca2SiO4. The expansions are mainly generated from the hydrations of CaO in the CaO-type expansive agent.

  14. Monoclinic deformation of calcite crystals at ambient conditions (United States)

    Przeniosło, R.; Fabrykiewicz, P.; Sosnowska, I.


    High resolution synchrotron radiation powder diffraction shows that the average crystal structure of calcite at ambient conditions is described with the trigonal space group R 3 bar c but there is a systematic hkl-dependent Bragg peak broadening. A modelling of this anisotropic peak broadening with the microstrain model from Stephens (1999) [15] is presented. The observed lattice parameters' correlations can be described by assuming a monoclinic-type deformation of calcite crystallites. A quantitative model of this monoclinic deformation observed at ambient conditions is described with the space group C 2 / c . The monoclinic unit cell suggested at ambient conditions is related with the monoclinic unit cell reported in calcite at high pressure (Merrill and Bassett (1975) [10]).

  15. Shell microstructure and its inheritance in the calcitic helcionellid Mackinnonia

    Directory of Open Access Journals (Sweden)

    Michael J. Vendrasco


    Full Text Available Mackinnonia davidi from the Cambrian (Series 2 of Australia has a prismatic outer shell layer and, as newly described here, a calcitic semi-nacre inner layer. The pattern is the same as in stenothecids such as Mellopegma, providing more evidence for a strong phylogenetic signal in the shell microstructure of Cambrian molluscs. In addition, calcite now appears to have been common in helcionellids and other molluscs during the early and middle Cambrian, with many species exhibiting foliated calcite. This is surprising given the dominance of aragonite in molluscs, both modern and from post-Cambrian fossil deposits with exceptional shell microstructure preservation, including localities from the Ordovician of the Cincinnati region, USA.

  16. Small scale shear zone in calcite: AMS and microstructure (United States)

    Roxerová, Zuzana; Machek, Matěj; Kusbach, Vladimír; Racek, Martin; Silva, Pedro F.


    Two structural profiles across thin shear zone in calcite from quarry in Estremoz (Portugal) were studied to find a relationship between AMS and strain in natural rocks. The mesoscopic fabric is characterized by the change from the subhorizontal coarse-grained foliation towards the ~2cm-wide shear zone center with subvertical fine-grained foliation. In microstructure, the shear zone records dynamic recrystallization of calcite aggregate which resulted in development of porphyroclastic microstructure with increasing proportion of fine-grained recrystallized matrix towards the shear zone center. Two distinct crystallographic preferred orientations of calcite were recorded. One related with porphyroclasts, characterized by subvertical orientation of calcite axes and another associated with recrystallized matrix showing subhorizontal calcite axes orientation. The magnetic susceptibility ranges from -8e-6SI to 9e-6SI, with the average -4e-6SI. The majority of the rock mass is diamagnetic, corresponding well with the thermomagnetic curves, with local paramagnetic accumulations in form of thin bands. The AMS of the both profiles exhibits stable subvertical foliation bearing vertical lineation which is locally alternated by the medium-angle foliation. We interpret the AMS fabric pattern which is perpendicular to the mineral one as a type of inverse AMS fabric, due to high iron content in major part of calcite grains The magnetic and microstructural description of the shear zone is accompanied by numerical modeling of AMS based on CPO and different proportion of porphyroclasts, matrix and mica for purposes of deciphering the influence of present microstructural features on AMS.

  17. Retroaortic left renal vein joining the left common iliac vein

    Energy Technology Data Exchange (ETDEWEB)

    Brancatelli, G.; Galia, M.; Finazzo, M.; Sparacia, G.; Pardo, S.; Lagalla, R. [Dept. of Radiology ' ' P. Cignolini' ' , Univ. of Palermo (Italy)


    Retroaortic left renal vein joining the left common iliac vein is a rare congenital anomaly in the development of the inferior vena cava. To our knowledge, only one case has been reported in the literature; however, its imaging features have never been described. A 27-year-old male presented with a 1-year history of recurrent right flank pain, dysuria, hematuria, and fever (39 C). Computed tomography and MR venography showed a retroaortic left renal vein joining the left common iliac vein. We present the CT and MR venography findings and discuss their feasibility in showing this congenital anomaly. (orig.)

  18. In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers (United States)

    Peters, Carl A.; Piazolo, Sandra; Webb, Gregory E.; Dutkiewicz, Adriana; George, Simon C.


    The detection of early life signatures using hydrocarbon biomarkers in Precambrian rocks struggles with contamination issues, unspecific biomarkers and the lack of suitable sedimentary rocks due to extensive thermal overprints. Importantly, host rocks must not have been exposed to temperatures above 250 °C as at these temperatures biomarkers are destroyed. Here we show that Archean sedimentary rocks from the Jeerinah Formation (2.63 billion yrs) and Carawine Dolomite (2.55 billion yrs) of the Pilbara Craton (Western Australia) drilled by the Agouron Institute in 2012, which previously were suggested to be suitable for biomarker studies, were metamorphosed to the greenschist facies. This is higher than previously reported. Both the mineral assemblages (carbonate, quartz, Fe-chlorite, muscovite, microcline, rutile, and pyrite with absence of illite) and chlorite geothermometry suggest that the rocks were exposed to temperatures higher than 300 °C and probably ∼400 °C, consistent with greenschist-facies metamorphism. This facies leads to the destruction of any biomarkers and explains why the extraction of hydrocarbon biomarkers from pristine drill cores has not been successful. However, we show that the rocks are cut by younger formation-specific carbonate veins containing primary oil-bearing fluid inclusions and solid bitumens. Type 1 veins in the Carawine Dolomite consist of dolomite, quartz and solid bitumen, whereas type 2 veins in the Jeerinah Formation consist of calcite. Within the veins fluid inclusion homogenisation temperatures and calcite twinning geothermometry indicate maximum temperatures of ∼200 °C for type 1 veins and ∼180 °C for type 2 veins. Type 1 veins have typical isotopic values for reprecipitated Archean sea-water carbonates, with δ13CVPDB ranging from - 3 ‰ to 0‰ and δ18OVPDB ranging from - 13 ‰ to - 7 ‰, while type 2 veins have isotopic values that are similar to hydrothermal carbonates, with δ13CVPDB ranging from - 18

  19. Strontium and Magnesium in Water and in Crassostrea Calcite. (United States)

    Lerman, A


    Distribution of magnesium and strontium was determined between waters and calcites secreted by the oyster species Crassostrea virginica and C. rhizophorae in natural habitats at eight localities, from Maine to Puerto Rico. The concentration of strontium in the calcite shells increases with increasing temperature in the range 13 degrees to 25 degrees C, and also with increasing Sr(++)/Ca(++) molal ratio in the water. The concentration of magnesium in the shells increases irregularly with temperature, and it is apparently independent of the Mg(++)/Ca(++) ratio in the water. The greater variation with temperature in the distribution factor for magnesium may be related to genetic differences between semi-isolated populations.

  20. Isotopic and elemental proxies in mollusc and brachiopod calcite

    DEFF Research Database (Denmark)

    Ullmann, Clemens Vinzenz

    This thesis summarizes the findings of studies conducted at the University of Copenhagen from September 2010 to September 2013, aiming at a better understanding of the geochemical signatures in marine, biogenic calcite. Throughout the history of the Earth, the climatic conditions and the chemical...... for a meaningful interpretation of isotopic and elemental ratios in shell materials. Without this knowledge the correct interpretation of the shell composition in terms of past environments is impossible. Calcite shells of brachiopods, bivalves and belemnites were analyzed here for shell ultra...

  1. Diagenetic alteration in low-Mg calcite from macrofossils

    DEFF Research Database (Denmark)

    Ullmann, Clemens Vinzenz; Korte, Christoph


    microscopy) and chemical (trace element abundances, isotopic ratios) screening techniques used to assess the alteration degree of low-Mg calcite macrofossils and summarize the findings on diagenetic trends observed for elemental and isotopic systems in such materials. For a robust evaluation...... of the preservation state of biogenic calcite, it is advisable to combine a set of complementary techniques. Absolute limiting values of element and isotope ratios for discarding diagenetically altered materials cannot be universally applied, but should rather be evaluated on a case to case basis. The evaluation can...

  2. Lead isotope compositions as guides to early gold mineralization: The North Amethyst vein system, Creede district, Colorado (United States)

    Foley, Nora K.; Ayuso, Robert A.


    The North Amethyst vein system, which is hosted by approximately 27 Ma Carpenter Ridge Tuff and approximately 26 Ma Nelson Mountain Tuff, has two mineral associations separated by brecciation and sedimentation in the veins. The early association consists of quartz, rhodonite, hematite, magnetite, electrum (Au (sub 0.3-0.5) Ag (sub 0.7-0.5)) , and Mn carbonate, Au-Ag sulfide, Ag sulfosalt, and base metal sulfide minerals. The later mineral association cuts the Mn- and Au-bearing assemblages and consists of quartz, calcite, sericite, chlorite, hematite, adularia, fluorite, base metal sulfides, and Ag-bearing tetrahedrite.


    Directory of Open Access Journals (Sweden)



    Full Text Available While the most common presentation of venous thromboembolic disease is deep vein thrombosis (DVT or pulmonary thromboembolism, rarer manifestations are thrombosis of jugular vein, cerebral sinus and inferior vena cava. Here we are presenting a rare case of inferior vena caval thrombosis with multiple thrombus in portal vein, splenic vein and superior mesenteric vein

  4. Cephalic vein aneurysm. (United States)

    Faraj, Walid; Selmo, Francesca; Hindi, Mia; Haddad, Fadi; Khalil, Ismail


    Cephalic vein aneurysms are rare malformations that may develop in any part of the vascular system, and their history, presentation, and management vary depending on their site. The etiology of venous aneurysms remains unclear, although several theories have been elaborated. Venous aneurysms are unusual vascular malformations that occur equally between the sexes and are seen at any age; they can present as either a painful or a painless subcutaneous mass. No serious complications have been reported from upper extremity venous aneurysms. Surgical excision is the definitive management for most of these. The case reported here presented with a painless and mobile, soft, subcutaneous mass that caused only cosmetic concern.

  5. Fracture and vein characterization of a crystalline basement reservoir, central Yemen (United States)

    Veeningen, R.; Grasemann, B.; Decker, K.; Bischoff, R.; Rice, A. H. N.


    The country of Yemen is located in the south-western part of the Arabian plate. The Pan-African basement found in western and central Yemen is highly deformed during the Proterozoic eon and is part of the Arabian-Nubian shield ANS (670-540Ma). This ANS is a result of the amalgamation of high-grade gneiss terranes and low-grade island arcs. The development of an extensive horst-and-graben system related to the breakup of Gondwana in the Mesozoic, has reactivated the Pan-African basement along NW-SE trending normal faults. As a result, younger Meosozoic marls, sandstones, clastics and limestones are unconformably overlying the basement. Some of these formations act as a source and/or reservoir for hydrocarbons. Due to fracturing of the basement, hydrocarbons have migrated horizontally into the basement, causing the crystalline basement to be a potential hydrocarbon reservoir. Unfortunately, little is known about the Pan-African basement in Central Yemen and due its potential as a reservoir, the deformation and oil migration history (with a main focus on the fracturing and veining history) of the basement is investigated in high detail. Representative samples are taken from 2 different wells from the Habban Field reservoir, located approximately 320 ESE of Sana'a. These samples are analysed using e.g. the Optical Microscope, SEM, EDX and CL, but also by doing Rb-Sr age dating, isotope analysis and fluid inclusion analysis. In well 1, the only lithology present is an altered gneiss with relative large (<5 cm diameter) multi-mineralic veins. In well 3, quartzite (top), gneiss (middle) and quartz porphyry's (middle) are intruded by a so called "younger" granitoid body (592.6±4.1Ma). All lithologies record polyphase systems of mineral veins. Pyrite and saddle dolomite in these veins have euhedral shapes, which means that they have grown in open cavities. Calcite is the youngest mineral in these veins, closing the vein and aborting the fluid flow. Fluid inclusions inside

  6. Historical Overview of Varicose Vein Surgery

    NARCIS (Netherlands)

    van den Bremer, Jephta; Moll, Frans L.


    Varicose veins are as old as Hippocrates. Varicose vein treatments come and go. Surgery for varicose vein disease is one of the commonest elective general surgical procedures. The history of varicose vein surgery has been traced. We note the first descriptions of varicose veins, and we particularly

  7. Incorporation of Eu(III) into Calcite under Recrystallization conditions. (United States)

    Hellebrandt, S E; Hofmann, S; Jordan, N; Barkleit, A; Schmidt, M


    The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu(3+) occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na(+). These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.

  8. Adsorption of polar aromatic hydrocarbons on synthetic calcite

    DEFF Research Database (Denmark)

    Madsen, Lene; Grahl-Madsen, Laila; Grøn, Christian


    The wettability of hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. A model system of synthetic call cite, cyclohexane and the three probe molecules: benzoic acid, benzyl alcohol and benzylamine, have been...

  9. Immobilization of nanoparticles by occlusion into microbial calcite

    DEFF Research Database (Denmark)

    Skuce, Rebecca L.; Tobler, Dominique Jeanette; MacLaren, Ian


    systems. In this study, the ureolytic bacteria Sporosarcina pasteurii was used to induce calcium carbonate precipitation in the presence of organo-metallic manufactured nanoparticles. As calcite crystals grew the nanoparticles in the solution became trapped inside these crystals. Capture of NPs within...

  10. Incorporation of Eu(III) into Calcite under Recrystallization conditions (United States)

    Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.


    The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu3+ occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na+. These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.

  11. Aragonite-calcite precipitation in vertical fractures of the "Erzberg" siderite deposit (Austria): Hydrogeochemical and neotectonic implications (United States)

    Boch, Ronny; Wang, Xianfeng; Kluge, Tobias; Kurz, Walter; Leis, Albrecht; Lin, Ke; Pluch, Hannes; Mittermayr, Florian; Dietzel, Martin


    The ore deposit "Erzberg" represents the worldwide largest FeCO3 occurrence and is amongst Austria's most prominent geological places due to its historic, economic and scientific value. The iron-ore (siderite/ankerite) bearing Devonian carbonates of the open pit mine locally host sequential aragonite-calcite precipitates infilling vertical fractures. These typically laminated carbonates are referred to as erzbergite in mineral collections. To study their formation conditions we recovered samples on-site, i.e. from the rare veins being cm to dm in horizontal and tenths of meters in vertical extension. Additionally, samples from our university collection and private collectors were investigated. Some of the fractures filled with aragonite/calcite further exhibit cataclastic sediments, damage zones and slickenside striations. Modern water samples were collected from fractures currently accessible to conduct hydrochemical analyses and modeling. Selected precipitates were analyzed applying microscopic techniques, XRD, electron microprobe elemental mapping, stable and clumped isotopes, and 238U-234U-230Th radiometric dating. Erzbergite veins show either uni- or bidirectional growth, i.e. on one or both fracture/fault planes toward complete infilling depending on vadose water flow. The laminated precipitates are dominated by aragonite relative to pristine as well as partially diagenetic (Mg)-calcite. Intercalated and recurrent brownish Fe-rich layers consisting of goethite, quartz, muscovite are probably of detrital origin. Stable C and O isotopes of the precipitates reveal pronounced spatiotemporal variations in which low δ18O values (-10.4 to -5.1 ‰ VPDB) reflect a meteoric origin and low temperatures of the erzbergite depositing solutions. Carbonate clumped isotope measurements verify formation temperatures ≤25 °C. High δ13C values (-0.7 to +6.8 ‰ VPDB) of the precipitates indicate an origin from dissolution of local ankerite and limestone, without a

  12. New inversion of calcite twin data for paleostress tested and calibrated on numerically-generated and natural data (United States)

    Parlangeau, Camille; Lacombe, Olivier; Schueller, Sylvie; Daniel, Jean-Marc


    grains of homogeneous size in order to minimize the error on the differential stress, which is the least constrained stress parameter. This is mainly due to our poor knowledge on the critical resolved shear stress value for calcite twinning. The technique can detect and separate superimposed stress tensors with close orientations (30° of difference in orientation of principal stress axes) or tensors with stress permutations (e.g., switch of σ₂ and σ₃ axes). The application on natural samples from veins in limestones of Tithonian-Aptian age (Monte Nero anticline, Italy) shows that even if some optical bias and natural heterogeneity exist, the inversion process finds stress regimes consistent with the opening of the successive vein sets. In order to circumvent bias due to optical measurements, the EBSD (electron backscatter diffraction) technique has been adapted for the collection of calcite twin data. We carried out inversion of calcite twin data collected using both U-stage measurements and EBSD; the comparison of the paleostress results demonstrate the reliability of this new EBSD-based twin data collection and the potential of coupling this approach with our new inversion technique to derive the local/regional paleostresses of interest.

  13. phenoVein - A software tool for leaf vein segmentation and analysis


    Bühler, Jonas; Rishmawi, Louai; Pflugfelder, Daniel; Huber, Gregor; Scharr, Hanno; Hülskamp, Martin; Koornneef, Maarten; SCHURR, ULRICH; Jahnke, Siegfried


    phenoVein is a software tool dedicated to automated segmenting and analyzing images of leaf veins. It includes comfortable manual correction features. Advanced image filtering automatically emphasizes veins from background and compensates for local brightness inhomogeneities. Phenotypical leaf vein traits being calculated are total vein density, vein lengths and widths and skeleton graph statistics. For determination of vein widths, a model based vein edge estimation approach has been impleme...

  14. Using vein fabric and fluid inclusion characteristics as an integrated proxy to constrain the relative timing of non cross-cutting, syn- to late-orogenic quartz vein generations (United States)

    Jacques, Dominique; Muchez, Philippe; Sintubin, Manuel


    gradual exhumation of the slate belt from ca. 7.5 to 6 km depth along a retrograde deformation path. A comparison of these results with a former study of syn- to late-orogenic calcite veins at the Variscan front zone (Kenis et al., 2000), indicates that exhumation processes throughout the Rhenohercynian fold-and-thrust belt were diachronous. While exhumation and related quartz veining in the High-Ardenne slate belt occurred during the Sudetic stage of the Variscan orogeny (ca. 325-310 Ma), the exhumation and related calcite veining at the Variscan front zone occurred during the Asturian stage of the Variscan orogeny (ca. 300 Ma). With this study we demonstrate that a relative timing for different vein generations, lacking any cross-cutting relationship, can still be attained through an integration of petrographic and microthermometric arguments. Moreover, this particular approach, enables to further delineate the P-T history of an orogenic system from its pre-, to its syn-, late- and finally postkinematic stages. References Jacques, D., Derez, T., Muchez, P., Sintubin, M., 2014. Syn- to late-orogenic quartz veins marking a retrograde deformation path in a slate belt: Examples from the High-Ardenne slate belt (Belgium). Journal of Structural Geology, 58, 43-58. Kenis, I., Muchez, P., Sintubin, M., Mansy, J.-L., Lacquement, F., 2000. The use of a combined structural, stable isotope and fluid inclusion study to constrain the kinematic history at the northern Variscan front zone (Bettrechies, northern France). Journal of Structural Geology, 22, 589-602.

  15. Calcite dissolution along a transect in the western tropical Indian Ocean: A multiproxy approach

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.

    ].Thoughthese studies could quantify the CO 3 = concentrations to some extent, they could certainly identify the calcite dissolution and preservation events [Broecker et al., 2003]. Recently calcite crystal- linity was also used as a proxy of carbonate ion...) calcite peak on XRD powder diagrams are interpreted as being better crystallized than those showing a broader diffraction peak and dissolution improves shell crystallinity [Bassinot et al., 2004]. Therefore the calcite crystallinity could be used as a...

  16. PVC mixtures’ mechanical properties with the addition of modified calcite as filler


    Vučinić Dušica R.; Jovanović Vladimir D.; Kolonja Božo M.; Sekulić Živko T.; Mihajlović Slavica R.


    In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaki...

  17. Mechanical properties of polyvinyl chloride mixtures with the addition of modified calcite as filler


    Mihajlović, Slavica R.; Sekulić, Živko T.; Vučinić, Dušica R.; Jovanović, Vladimir D.; Kolonja, Božo M.


    In this study, mechanical properties of PVC mixtures (PVC, stabilizer, lubricant and filler) such as tensile strength, tensile elongation, breaking strength and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure had better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking s...

  18. Structural incorporation of Neptunyl(V) into Calcite: Interfacial Reactions and Kinetics


    Heberling, Frank


    In this experimental work the calcite-water interface is characterized by means of zetapotential and surface diffraction measurements. Based on the experimental results a new Basic Stern Surface Complexation model for calcite is developed. Neptunyl(V) adsorption at the calcite surface and incorporation into the calcite structure is studied by batch type adsorption- and mixed flow reactor experiments. Adsorption and incorporation species of Neptunyl are investigated by EXAFS spectroscopy.

  19. Leiomyosarcoma of the renal vein

    Directory of Open Access Journals (Sweden)

    Lemos Gustavo C.


    Full Text Available Leiomyosarcoma of the renal vein is a rare tumor of complex diagnosis. We presented a case of renal vein leiomyosarcoma detected in a routine study. The primary treatment was complete surgical removal of the mass. In cases where surgical removal is not possible the prognosis is poor, with high rates of local recurrence and distant spread.

  20. Agenesis of the iliac veins. (United States)

    Thomas, M L; Posniak, H V


    Three case reports of patients with the rare anomaly of agenesis of the iliac veins are presented. It is emphasised that full phlebographic investigation should be carried out in such patients before surgical treatment is considered. It is pointed out that surgical ablation may exacerbate the symptoms of leg swelling and varicose veins for which the patients seek advice.

  1. Infrared imaging of varicose veins (United States)

    Noordmans, Herke Jan; de Zeeuw, Raymond; Verdaasdonk, Ruud M.; Wittens, Cees H. A.


    It has been established that varicose veins are better visualized with infrared photography. As near-infrared films are nowadays hard to get and to develop in the digital world, we investigated the use of digital photography of varicose veins. Topics that are discussed are illumination setup, photography and digital image enhancement and analysis.

  2. 10-Minute Conultation Varicose veins

    Institute of Scientific and Technical Information of China (English)


    A 55 year old woman presents with a history of tortuous veins on both legs and a related ache towards the end of the day.She finds these veins unsightly and would like to know whether she can have them treated.

  3. Sorption and catalytic oxidation of Fe(II) at the surface of calcite

    NARCIS (Netherlands)

    Mettler, S.; Wolthers, M.; Charlet, L.; Von Gunten, U.


    The effect of sorption and coprecipitation of Fe(II) with calcite on the kinetics of Fe(II) oxidation was investigated. The interaction of Fe(II) with calcite was studied experimentally in the absence and presence of oxygen. The sorption of Fe(II) on calcite occurred in two distinguishable steps: (a

  4. Sagittal vein thrombosis caused by central vein catheter.

    Directory of Open Access Journals (Sweden)

    Feridoun Sabzi


    Full Text Available Cerebral venous thrombosis, including thrombosis of cerebral veins and major dural sinuses, is an uncommon disorder in the general population. However, it has a higher frequency among patients younger than 40 years of age, patients with thrombophilia, pregnant patients or those receiving hormonal contraceptive therapy or has foreign body such as catheter in their veins or arterial system. In this case report, we described clinical and radiological findings in a patient with protein C-S deficiency and malposition of central vein catheter.

  5. Fracture-aperture alteration induced by calcite precipitation (United States)

    Jones, T.; Detwiler, R. L.


    Mineral precipitation significantly alters the transport properties of fractured rock. Chemical solubility gradients that favor precipitation induce mineral growth, which decreases the local aperture and alters preferential flow paths. Understanding the resulting development of spatial heterogeneities is necessary to predict the evolution of transport properties in the subsurface. We present experimental results that quantify the relationship between mineral precipitation and aperture alteration in a transparent analog fracture, 7.62cm x 7.62cm, with a uniform aperture of ~200 μm. Prior to flow experiments, a pump circulated a super-saturated calcite solution over the bottom glass, coating the glass surface with calcite. This method of seeding resulted in clusters of calcite crystals with large reactive surface area and provided micro-scale variability in the aperture field. A continuous flow syringe pump injected a reactive fluid into the fracture at 0.5 ml/min. The fluid was a mixture of sodium bicarbonate (NaHCO3, 0.02M) and calcium chloride (CaCl2 0.0004M) with a saturation index, Ω, of 8.51 with respect to calcite. A strobed LED panel backlit the fracture and a high-resolution CCD camera monitored changes in transmitted light intensity. Light transmission techniques provided a quantitative measurement of fracture aperture over the flow field. Results from these preliminary experiments showed growth near the inlet of the fracture, with decreasing precipitation rates in the flow direction. Over a period of two weeks, the fracture aperture decreased by 17% within the first 4mm of the inlet. Newly precipitated calcite bridged individual crystal clusters and smoothed the reacting surface. This observation is an interesting contradiction to the expectation of surface roughening induced by mineral growth. Additionally, the aperture decreased uniformly across the width of the fracture due to the initial aperture distribution. Future experiments of precipitation

  6. Vein matching using artificial neural network in vein authentication systems (United States)

    Noori Hoshyar, Azadeh; Sulaiman, Riza


    Personal identification technology as security systems is developing rapidly. Traditional authentication modes like key; password; card are not safe enough because they could be stolen or easily forgotten. Biometric as developed technology has been applied to a wide range of systems. According to different researchers, vein biometric is a good candidate among other biometric traits such as fingerprint, hand geometry, voice, DNA and etc for authentication systems. Vein authentication systems can be designed by different methodologies. All the methodologies consist of matching stage which is too important for final verification of the system. Neural Network is an effective methodology for matching and recognizing individuals in authentication systems. Therefore, this paper explains and implements the Neural Network methodology for finger vein authentication system. Neural Network is trained in Matlab to match the vein features of authentication system. The Network simulation shows the quality of matching as 95% which is a good performance for authentication system matching.

  7. Surface tension alteration on calcite, induced by ion substitution

    DEFF Research Database (Denmark)

    Sakuma, Hiroshi; Andersson, Martin Peter; Bechgaard, Klaus


    The interaction of water and organic molecules with mineral surfaces controls many processes in nature and industry. The thermodynamic property, surface tension, is usually determined from the contact angle between phases, but how does one understand the concept of surface tension at the nanoscale...... in the pore water. Incorporation of MgSO4 into calcite, which is energetically favored, decreases surface tension and releases polar oil compounds......., where particles are smaller than the smallest droplet? We investigated the energy required to exchange Mg2+ and SO4 2- from aqueous solution into calcite {10.4} surfaces using density functional theory. Mg2+ substitution for Ca2+ is favored but only when SO4 2- is also present and MgSO4 incorporates...

  8. Tuning hardness in calcite by incorporation of amino acids (United States)

    Kim, Yi-Yeoun; Carloni, Joseph D.; Demarchi, Beatrice; Sparks, David; Reid, David G.; Kunitake, Miki E.; Tang, Chiu C.; Duer, Melinda J.; Freeman, Colin L.; Pokroy, Boaz; Penkman, Kirsty; Harding, John H.; Estroff, Lara A.; Baker, Shefford P.; Meldrum, Fiona C.


    Structural biominerals are inorganic/organic composites that exhibit remarkable mechanical properties. However, the structure-property relationships of even the simplest building unit--mineral single crystals containing embedded macromolecules--remain poorly understood. Here, by means of a model biomineral made from calcite single crystals containing glycine (0-7 mol%) or aspartic acid (0-4 mol%), we elucidate the origin of the superior hardness of biogenic calcite. We analysed lattice distortions in these model crystals by using X-ray diffraction and molecular dynamics simulations, and by means of solid-state nuclear magnetic resonance show that the amino acids are incorporated as individual molecules. We also demonstrate that nanoindentation hardness increased with amino acid content, reaching values equivalent to their biogenic counterparts. A dislocation pinning model reveals that the enhanced hardness is determined by the force required to cut covalent bonds in the molecules.

  9. Constitutive Response of Microbial Induced Calcite Precipitation Cemented Sands (United States)

    Feng, Kai

    In the last decade, microbial induced calcite precipitation (MICP) emerged as a novel technique for implementing soil improvement in an environmentally-friendly and economically beneficial manner. However, the mechanical behavior and constitutive response of these materials are still not fully explored by researchers. In this dissertation, the characteristics of MICP cemented sands are investigated through numerical modelling and experimental tests, including macro and micro tests under both static and dynamic loading. In the first part, the mechanical behavior of MICP cemented sands were probed using monotonic load testing and the existence of calcite precipitation was verified by scanning electron microscopy, with this behavior compared to traditionally cemented soil and naturally cemented soil. Both MICP cementation and traditional cementation were verified to be effective in the increase of stiffness and strength, and unique characteristic of MICP cemented soil was highlighted.

  10. Contrasts in Faulting and Veining Across the Aseismic to Seismic Transition, Kodiak Accretionary Complex, Alaska (United States)

    Rowe, C. D.; Thompson, E.; Moore, J. C.


    Structure and Character of Veined Zones in Kodiak Accretionary Prism Subduction thrust systems produce the world's largest earthquakes. The transition from aseismic to seismogenic faulting occurs at approximately 4 km depth. The chemical and physical controls on this transition are not well understood, but previous research indicates that phase transformations, fluid pressure changes, and formation of authigenic minerals and cements may produce changes in cohesion and coefficient of friction which control fault behavior. We have described and sampled areas of paleo faulting and fluid flow in an ancient subduction thrust system, Kodiak Archipelago, Alaska. We are comparing two formations: the upper Paleocene Ghost Rocks Fm., which previous work has shown to have been exposed to ~ 250° C and 12 km depth (well within the seismogenic zone) and the Eocene Sitkalidak Fm., which has been exposed to 100-125° C at 2.4-3.9 km depth, (accreted before it crossed the aseismic-seismogenic boundary.) Field observations confirmed earlier work and supported project hypotheses. The Ghost Rocks Fm. is characterized by discrete heavily veined zones meters to tens of meters thick. Individual veins in these zones commonly reach thickness of up to several centimeters and are primarily composed of clean calcite and quartz. In contrast, the Sitkalidak Fm. is characterized by a small volume of web-like networks of very fine veins rarely exceeding a few mm in thickness. These veins are composed of laumontite and "dirty" calcite. In the Sitkalidak Fm., stratal disruption is characterized by conjugate shear fracturing, leaving lustrous black residues on shear surfaces, followed by extensional fractures with veining, indicating rising fluid pressures. In the Ghost Rocks Fm., there is little evidence for conjugate shear fracturing. Stratal disruption is accomplished by extensive extensional fracturing and veining as well as ductile deformation and rotation of sediments under non-coaxial strain

  11. Magnesium-Calcite Crystal Formation Mediated by the Thermophilic Bacterium Geobacillus thermoglucosidasius Requires Calcium and Endospores. (United States)

    Murai, Rie; Yoshida, Naoto


    Fresh Geobacillus thermoglucosidasius cells grown on soybean-casein digest nutrient agar were inoculated as a parent colony 1 cm in diameter on the surface of an agar gel containing acetate and calcium ions (calcite-promoting hydrogel) and incubated at 60 °C for 4 days, after which magnesium-calcite single crystals of 50-130 µm in size formed within the parent colony. Addition of EDTA, polyacrylic acid or N,N-dicyclohexylcarbodiimide to the calcite-forming hydrogel inhibited the parent colony from forming magnesium-calcite crystals. Inoculation of G. thermoglucosidasius on calcite-forming hydrogel containing 5 µM cadmium and 20 µM zinc resulted in a decrease in the sporulation rate from 55 to 7-8 %. Magnesium-calcite synthesis decreased relative to the sporulation rate. G. thermoglucosidasius exhibited higher adsorption/absorbance of calcium than other Geobacillus sp. that do not mediate calcite formation and higher levels of magnesium accumulation. Calcium ions contained in the calcite-promoting hydrogel and magnesium ions concentrated in G. thermoglucosidasius cells serve as the elements for magnesium-calcite synthesis. The observed decreases in sporulation rate and magnesium-calcite formation support the hypothesis that endospores act as nuclei for the synthesis of magnesium-calcite single crystals.

  12. Molecular dynamics simulations of peptides on calcite surface


    Yang, Mingjun; Rodger, Mark; Harding, John; Stipp, Susan S.L.


    Abstract A series of Molecular Dynamics (MD) simulations has been carried out to investigate the interaction between peptides and a calcite (1 0 -1 4) surface in water. A 16-amino acid and a 17-amino acid peptide have been built and three different configurations for each peptide are used as starting configurations. The dynamic behaviour of these peptides has been investigated by calculating their radii of gyration and distribution of dihedral angles. For comparison, the simulatio...

  13. Copper incorporation in foraminiferal calcite: results from culturing experiments

    Directory of Open Access Journals (Sweden)

    G. J. van der Zwaan


    Full Text Available A partition coefficient for copper (DCu in foraminiferal calcite has been determined by culturing individuals of two benthic species under controlled laboratory conditions. The partition coefficient of a trace element (TE is an emperically determined relation between the TE/Ca ratio in seawater and the TE/Ca ratio in foraminiferal calcite and has been established for many divalent cations. Despite its potential to act as a tracer of human-induced, heavy metal pollution, data is not yet available for copper. Since partition coefficients are usually a function of multiple factors (seawater temperature, pH, salinity, metabolic activity of the organism, etc., we chose to analyze calcite from specimens cultured under controlled laboratory conditions. They were subjected to different concentrations of Cu2+ (0.1–20 µmol/l and constant temperature (10 and 20°C, seawater salinity and pH. We monitored the growth of new calcite in specimens of the temperate, shallow-water foraminifer Ammonia tepida and in the tropical, symbiont-bearing Heterostegina depressa. Newly formed chambers were analyzed for Cu/Ca ratios by laser ablation-ICP-MS. The estimated partition coefficient (0.1–0.4 was constant to within experimental error over a large range of (Cu/Caseawater ratios and was remarkably similar for both species. Neither did the presence or absence of symbionts affect the DCu, nor did we find a significant effect of temperature or salinity on Cu-uptake.

  14. Production Engineering for Growth of Synthetic Calcite Polarizer Material (United States)


    sources, uniform quality, and geological formation have been more Intensely studied. Numerous techniques for the preparation of...Throughout nature there are many forms of consolidated CaC03 such as limestone, marine life, and stalactites . Most of these are known to be formed...Hydrothermally Grown Calcite (Continued) a slight retr the effects o temperature i formation on density was c crystal. The morphology most

  15. Meteoric calcitization of magnesite in Miocene lacustrine deposits (Calatayud basin, NE Spain) (United States)

    Cañaveras, J. C.; Sánchez-Moral, S.; Sanz-Rubio, E.; Hoyos, M.


    Sedimentary magnesite deposits are commonly present in evaporite successions in the Tertiary Calatayud basin (NE Spain). Outcropping evaporite sequences, mainly composed of secondary gypsum after anhydrite-glauberite, show centimetre-thick layers of magnesite passing laterally into calcite pseudospar. Petrographic and stable isotope data indicate that calcite pseudospar formed via late-stage calcitization of magnesite under near-surface conditions. Calcitization occurred by the interaction between magnesite and Ca-enriched waters derived from the dissolution of gypsum and/or glauberite. The geochemical simulation of this process, petrographic evidence, and the correlation between the magnesite/calcite ratio and the δ18O values of both magnesite and calcite samples across the reaction front are in agreement with the existence of neoformed 18O-depleted magnesite during the waning stages of the calcitization process.

  16. Arsenite sorption and co-precipitation with calcite

    CERN Document Server

    Roman-Ross, Gabriela; Turrillas, Xavier; Fernandez-Martinez, Alejandro; Charlet, Laurent


    Sorption of As(III) by calcite was investigated as a function of As(III) concentration, time and pH. The sorption isotherm, i.e. the log As(III) vs. log [As(OH)3 degrees / Assat] plot is S-shaped and has been modelled on an extended version of the surface precipitation model. At low concentrations, As(OH)3 degrees is adsorbed by complexation to surface Ca surface sites, as previously described by the X-ray standing wave technique. The inflexion point of the isotherm, where As(OH)3 degrees is limited by the amount of surface sites (ST), yields 6 sites nm-2 in good agreement with crystallographic data. Beyond this value, the amount of sorbed arsenic increases linearly with solution concentration, up to the saturation of arsenic with respect to the precipitation of CaHAsO3(s). The solid solutions formed in this concentration range were examined by X-ray and neutron diffraction. The doped calcite lattice parameters increase with arsenic content while c/a ratio remains constant. Our results made on bulk calcite on...

  17. Is bicarbonate stable in and on the calcite surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Rodriguez Blanco, Juan Diego; Stipp, Susan Louise Svane


    We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3− CO32− + H+, when HCO3− is included in, and adsorbed on, a calcite surface. We have used cluster models (80–100 atoms) to represent...... the flat {10.4} surface, acute steps, obtuse steps, two types of kinks on the acute step and two types of kinks on the obtuse steps. Based on the predicted pKa values, which range from −6.0 to 2.4 depending on the surface site, we conclude that bicarbonate deprotonates to carbonate when it is in calcite...... even when pH in solution is very low. This is true for all surface sites, even for solutions where 2.4 calcite, the predicted pKa for deprotonation is 7.5, which is ∼3 pH units lower than in aqueous solution...

  18. Interactions of salicylic acid derivatives with calcite crystals. (United States)

    Ukrainczyk, Marko; Gredičak, Matija; Jerić, Ivanka; Kralj, Damir


    Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated.

  19. Rate of radiocarbon retention onto calcite by isotope exchange

    Energy Technology Data Exchange (ETDEWEB)

    Lempinen, Janne; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry


    Radiocarbon ({sup 14}C) is a top priority class radionuclide associated with the long-term safety of spent nuclear fuel disposal. Dissolved inorganic radiocarbon can be retained in bedrock via isotope exchange with calcite (CaCO{sub 3}) at solubility equilibrium with groundwater. In the present study, the rate of the isotope exchange process was investigated on synthetic calcite using batch experiments. Experiments were performed in solutions with a calcium concentration of 0.0002-0.1 M, including two synthetic reference groundwaters. The radiocarbon activity in the solutions decreased exponentially as a function of time, thus following first-order kinetics. The rate of isotope exchange was quantified from an exponential fit to the activity data over time. The rate of radiocarbon retention increased as a function of the calcium activity. The isotope exchange half-life was only 4.3 days at calcium ion activities over 0.01. This half-life is very much shorter than the half-life of {sup 14}C or the time scale of groundwater movements; consequently calcite can effectively retain radiocarbon from brackish and saline groundwaters.

  20. Neonatal renal vein thrombosis. (United States)

    Brandão, Leonardo R; Simpson, Ewurabena A; Lau, Keith K


    Neonatal renal vein thrombosis (RVT) continues to pose significant challenges for pediatric hematologists and nephrologists. The precise mechanism for the onset and propagation of renal thrombosis within the neonatal population is unclear, but there is suggestion that acquired and/or inherited thrombophilia traits may increase the risk for renal thromboembolic disease during the newborn period. This review summarizes the most recent studies of neonatal RVT, examining its most common features, the prevalence of acquired and inherited prothrombotic risk factors among these patients, and evaluates their short and long term renal and thrombotic outcomes as they may relate to these risk factors. Although there is some consensus regarding the management of neonatal RVT, the most recent antithrombotic therapy guidelines for the management of childhood thrombosis do not provide a risk-based algorithm for the acute management of RVT among newborns with hereditary prothrombotic disorders. Whereas neonatal RVT is not a condition associated with a high mortality rate, it is associated with significant morbidity due to renal impairment. Recent evidence to evaluate the effects of heparin-based anticoagulation and thrombolytic therapy on the long term renal function of these patients has yielded conflicting results. Long term cohort studies and randomized trials may be helpful to clarify the impact of acute versus prolonged antithrombotic therapy for reducing the morbidity that is associated with neonatal RVT.

  1. PVC mixtures’ mechanical properties with the addition of modified calcite as filler

    Directory of Open Access Journals (Sweden)

    Vučinić Dušica R.


    Full Text Available In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture containing calcite modified by dry process. The results showed that the bonding strength between calcite and the adsorbed organic component affected tensile strength, tensile elongation and breaking strength of the PVC mixtures. The best filler was obtained by wet modification using 1.5% stearic acid solution that provided the formation of a stearate monolayer chemisorbed on calcite. The PVC mixtures containing the calcite modified by wet process using 1.5% stearic acid solution exhibited the best mechanical properties. This calcite was completely hydrophobic with dominant chemically adsorbed surfactant, which means that stearate chemisorbed on calcite provided stronger interaction in the calcite-stearic acid-PVC system.

  2. A Vein Map Biometric System

    Directory of Open Access Journals (Sweden)

    Felix Fuentes


    Full Text Available There is increasing demand world-wide, from government agencies and the private sector for cutting-edge biometric security technology that is difficult to breach but userfriendly at the same time. Some of the older tools, such as fingerprint, retina and iris scanning, and facial recognition software have all been found to have flaws and often viewed negatively because of many cultural and hygienic issues associated with them. Comparatively, mapping veins as a human barcode, a new technology, has many advantages over older technologies. Specifically, reproducing a three-dimensional model of a human vein system is impossible to replicate. Vein map technology is distinctive because of its state-of-the-art sensors are only able to recognize vein patterns if hemoglobin is actively flowing through the person

  3. Novel Determination of the Orientation of Calcite on Mineral Substrates (United States)

    Zhao, L.; Ji, X.; Teng, H.


    In the threat of global warming, the transformation from CO2 to stable carbonate minerals is significant to geological CO2 sequestration in the long term.Previous efforts have found that when carbonate minerals nucleate on some mineral substrates ,the time of carbon capture can be shorted .Many efforts have been focused on the dynamics when carbonate minerals nucleate on mineral substrates, but few have studied the orientation of carbonate minerals on mineral substrates. In our experiment, we mainly focused on the orientation of calcite on mineral substrates.We mixed NaHCO3 and CaCl2 to nucleate when mineral substrates were added and a multi-parameter analyzer was used to monitor in real time to determine the induction time for nucleation. On the basis of classical nucleation theory, we got a brand new formula to decide the orientation of calcite on mineral substrates. lntind=(2-cosθ+cos3θ)*16πγ3vm2(12*(kBT)3*(lnS)2)+ln(1/N0v)+ ΔEa/(kBT)where θ is the angle between the substrate and the nuclei, tind is the induction time for nucleation, γ is he average surface free energy, N0 is the total number of particles per unit volume of solution, ΔEa is the activation energy for molecular motion across the embryo-matrix interface, S is the supersaturation index ,kB is the Boltzmann constant. Using the new formula above , when biotite was used as substrate mineral ,we found that the angle between the biotite and the nuclei was 119°. Angle measured on SEM images also supported our conclusion above. Combined with SEM and Debye ring analysed by Rigaku 2D data processing software, we only found one point of (006) in Debye ring, unlike (104)(many points in one ring and it meant that the orientation of (104) is random ). That meant (001) of calcite was first formed on biotite (001). In that case we inferred that 119° was formed by (001) of botite and (012) of calcite for the intersection angle of (001) and (012) was 120°. Future research will focus on the orientation of

  4. Novel identification of matrix proteins involved in calcitic biomineralization. (United States)

    Rose-Martel, Megan; Smiley, Sandy; Hincke, Maxwell T


    Calcitic biomineralization is essential for otoconia formation in vertebrates. This process is characterized by protein-crystal interactions that modulate crystal growth on an extracellular matrix. An excellent model for the study of calcitic biomineralization is the avian eggshell, the fastest known biomineralization process. The objective of this study is to identify and characterize matrix proteins associated with the eggshell mammillary cones, which are hypothesized to regulate the earliest stage of eggshell calcification. Mammillary cones were isolated from 2 models, fertilized and unfertilized, and the released proteins were identified by RP-nanoLC and ES-MS/MS proteomics. Proteomics analysis identified 49 proteins associated with the eggshell membrane fibers and, importantly, 18 mammillary cone-specific proteins with an additional 18 proteins identified as enriched in the mammillary cones. Among the most promising candidates for modulating protein-crystal interactions were extracellular matrix proteins, including ABI family member 3 (NESH) binding protein (ABI3BP), tiarin-like, hyaluronan and proteoglycan link protein 3 (HAPLN3), collagen alpha-1(X), collagen alpha-1(II) and fibronectin, in addition to the calcium binding proteins calumenin, EGF-like repeats and discoidin 1-like domains 3 (EDIL3), nucleobindin-2 and SPARC. In conclusion, we identified several cone-resident proteins that are candidates to regulate initiation of eggshell calcification. Further study of these proteins will determine their roles in modulating calcitic biomineralization and lead to insight into the process of otoconia formation/regeneration. Biomineralization is essential for the development of hard tissues in vertebrates, which includes both calcium phosphate and calcium carbonate structures. Calcitic mineralization by calcium carbonate is an important process in the formation of otoconia, which are gravity receptor organs located in the inner ear and are responsible for balance

  5. [Surgery of essential varicose veins]. (United States)

    Maraval, M


    Idiopathic varicose veins of the lower limbs are a frequent but benign disorder. Surgery is only a moment in the course of the disease. Although not the only treatment of essential varicose veins, surgery by an experienced team performing crossectomy, stripping by intussusception using a stripper, and phlebectomy gives fully satisfactory results, both to patient and to physician, in over 80% of cases. New techniques were recently developed that, at present, have not confirmed early hopes.

  6. Portal Vein Thrombosis in non cirrhotic patients

    NARCIS (Netherlands)

    M.C.W. Spaander (Manon)


    textabstractExtrahepatic portal vein thrombosis (EPVT) is the most common cause of portal hypertension in non- cirrhotic patients. EPVT has been defined as an obstruction of the extrahepatic portal vein with or without involvement of the intrahepatic portal veins. Although the portal vein accounts f

  7. Hydrothermal replacement of calcite by Mg-carbonates (United States)

    Jonas, Laura; Mueller, Thomas; Dohmen, Ralf


    The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product

  8. Principles of calcite dissolution in human and artificial otoconia.

    Directory of Open Access Journals (Sweden)

    Leif Erik Walther

    Full Text Available Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV. The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic otoconia (calcite gelatin nanocomposits and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM. Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV.

  9. Effect of airborne particle on SO 2-calcite reaction (United States)

    Böke, Hasan; Göktürk, E. Hale; Caner-Saltık, Emine N.; Demirci, Şahinde


    In modern urban atmosphere, sulphur dioxide (SO 2) attacks calcite (CaCO 3) in calcareous stone-producing gypsum (CaSO 4·2H 2O) which forms crust at rain sheltered surfaces and accelerates erosion at areas exposed to rain. The airborne particles collected on stone surfaces have always been considered to enhance the gypsum crust formation and thus it is believed that they should be removed from the surface to decrease the effects of SO 2. In this study, our aim was to investigate this event by carrying out a series of experiments in laboratory using pure calcium carbonate powder to represent calcareous stone. Sodium montmorillonite, activated carbon, ferric oxide, vanadium pentoxide and cupric chloride were mixed in the pure calcium carbonate powder as substitutes of the airborne particles in the polluted atmosphere. The samples have been exposed at nearly 10 ppmv SO 2 concentrations at 90% relative humidity conditions in a reaction chamber for several days. The mineralogical composition of the exposed samples were determined by X-ray diffraction (XRD) analysis and infrared spectrometer (IR). Sulphation reaction products, calcium sulphite hemihydrate, gypsum and unreacted calcite, were determined quantitatively using IR. Exposed samples have also been investigated morphologically using a scanning electron microscope (SEM). Experimental results reveal that calcium sulphite hemihydrate is the main reaction product of the SO 2-calcite reaction. It turns out that airborne particles play an important catalytic role in the oxidation of calcium sulphite hemihydrate into gypsum, although their presence does not very significantly affect the extent of sulphation reaction. This behaviour of airborne particles is explained by the presence of liquid film on the calcium carbonate surface where a series of reactions in the gas-liquid-solid interfaces takes place.

  10. The sensitized luminescence of manganese-activated calcite (United States)

    Schulman, J.H.; Evans, L.W.; Ginther, R.J.; Murata, K.J.


    Synthetic manganese-activated calcites are shown to be practically inert to ultraviolet excitation in the range 2000-3500A, while they are luminescent under cathode-ray excitation. The incorporation of small amounts of an auxiliary impurity along with the manganese produces the strong response to ultraviolet radiation hitherto ascribed to CaCO3:Mn itself. Three such impurities have been studied: lead, thallium, and cerium. The first two induce excitation in the neighborhood of the mercury resonance line, while the cerium introduces a response principally to longer wave ultraviolet. The strong response to 2537A excitation shown by some natural calcites is likewise found to be due to the presence of lead along with the manganese, rather than to the manganese alone. The data do not warrant ascribing the longer wave-length ultraviolet-excited luminescence of all natural calcites to the action of an auxiliary impurity. The essential identity of the cathode-ray excited luminescence spectra of CaCO 3:Mn, CaCO3: (Pb+Mn), CaCO3:(Tl+Mn), and CaCO3:(Ce+Mn) with the 2537A-excited spectra of the latter three is evidence that the luminescent center in all cases is the manganese ion or the MnO6 group. It is shown that a "cascade" mechanism for the action of the auxiliary impurities, lead, thallium, and cerium, is incorrect; and that the phenomenon must be considered as a case of sensitized luminescence. Owing to the nature of cathode-ray excitation, the manganese activator can be excited by this agent even in the absence of a second impurity. For optical excitation, however, an absorption band for the ultraviolet must be established by building into the CaCO3:Mn a second impurity or "sensitizer.".

  11. Simulating Succinate-Promoted Dissolution at Calcite {104} Steps (United States)

    Mkhonto, D.; Sahai, N.


    Organic molecules of a wide range of molecular weights from small organic acids, amino-acids, acidic peptides and acidic proteins to humic and fulvic acids play a key role in modulating nucleation, crystal growth and dissolution of calcium carbonate polymorphs. In general, these acidic molecules inhibit calcite growth and, promote dissolution preferentially along specific crystallographic directions, in the process, regulating crystal shape and size, and even whether a metastable polymorph (e.g., vaterite or aragonite) is nucleated first. For example, chiral faces of calcite are selected by chiral amino-acids and the unusual {hk0} faces are expressed in the presence of amino-acids [Orme et al., 2001], and unusual heptagonal dissolution etch-pit are seen in the presence of succinate compared to the normal rhombohedral pits in water alone [Teng et al., 2006]. Thus, the presence of unusual crystal morphologies may indicate organic-mediated growth, thus serving as a biosignature. We have conducted the Molecular Dynamics (MD) simulations using the Consistent Valence Force Field (CVFF) as implemented in the FORCITE© module of the Materials Studio © software package (Accelrys, Inc. TM) to model the adsorption of succinate, a dicarboxylic acid, and charge- balancing Na+ ions on dry and hydrated steps in different directions on the {104} cleavage face of calcite [Mkhonto and Sahai, in prep.]. At the site of succinate adsorption, we find elongation of the interatomic distances (Ca-OCO3,i) between surface Ca2+ cation and the oxygen of the underlying inorganic CO32- anion the first surface layer of calcite, compared to the corresponding distances in the presence of water alone, suggesting greater ease of surface Ca2+ detachment. This result is consistent with the empirically observed increase in overall dissolution rate with succinate [Teng et al., 2006]. Furthermore, succinate adsorption lowers the step energies, which explains the appearance of steps in the unsusual [42

  12. Incorporation of Eu(III) into calcite under recrystallization conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hellebrandt, S.E. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology; Jordan, Norbert [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Barkleit, Astrid [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements; Schmidt, Moritz [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). HGF Young Investigator Group; Hofmann, S.


    The interaction of three calcite powders with Eu(III) under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). Batch contact studies with reaction times from 1 week up to 3 years revealed that the speciation differs from that observed previously in co-precipitation experiments and is dominated by a newly identified species ''γ''. The speed of formation of this species was found to depend greatly on the recrystallization rate of the studied minerals.

  13. Study of Biomass Calcite as Fine Aggregate of Concrete

    Institute of Scientific and Technical Information of China (English)

    WANG Jian; YU Yan


    The possibility of using crushed oyster shell to partly replace the fine aggregate of concrete was evaluated. The compressive strength and slump of concrete mixture with different amount of crushed oyster shell were tested and thus the appropriate dosage was determined. Additionally, the compatibility with super plasticizer and the stability in NazSO4 solution were also discussed to prove the feasibility of oyster shell as fine aggregate of concrete. The microstructure of concrete was observed with XRD and SEM techniques. This research provides the basis for the application of waste biomass calcite.

  14. Grain coarsening of calcite: Fundamental mechanisms and biogenic inhibition

    DEFF Research Database (Denmark)

    Schultz, Logan Nicholas

    grain diameter: The small particle size was similar to coccolith elements in chalk. Calcite was aged in saturated solutions for up to 261 days at temperatures up to 200 °C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and BET surface area data showed fundamental insight into grain...... coarsening – small grains coarsen by aggregation at high temperatures, followed by Ostwald ripening. Alginate, a model for the acidic polysaccharides produced by coccolithiphores, inhibited coarsening at a steady rate. A Pseudomonas aeruginosa biofilm preserved particles for at least 60 days before...

  15. Unusual calcite stromatolites and pisoids from a landfill leachate collection system (United States)

    Maliva, Robert G.; Missimer, Thomas M.; Leo, Kevin C.; Statom, Richard A.; Dupraz, Christophe; Lynn, Matthew; Dickson, J. A. D.


    Low-magnesium calcite stromatolites and pisoids were found to have precipitated within the leachate collection system piping of a Palm Beach County, Florida, landfill. The stromatolites and pisoids formed in an aphotic and anoxic environment that was at times greatly supersaturated with calcite. The stromatolites are composed of branching cylindrical bundles of concentrically laminated radial fibrous crystals. The pisoids consist of concentric layers of radial fibrous and microcrystalline calcite. Bacteria, likely sulfate reducing, appear to have acted as catalysts for calcite crystal nucleation, and thus the formation of the stromatolites and pisoids. The leachate system stromatolites provide a recent example of stromatolites that formed largely by cement precipitation. By acting as catalysts for calcite nucleation, bacteria may cause more rapid cementation than would have occurred under purely abiotic conditions. Rapid calcite precipitation catalyzed by bacteria has interfered with the operation of the Palm Beach County landfill leachate collection by obstructing pipes and may be an unrecognized problem at other landfill sites.

  16. From vein precipitates to deformation and fluid rock interaction within a SSZ: Insights from the Izu-Bonin-Mariana fore arc (United States)

    Micheuz, Peter; Quandt, Dennis; Kurz, Walter


    International Ocean Discovery Program (IODP) expeditions 352 and 351 drilled through oceanic crust of the Philippine Sea plate. The two study areas are located near the outer Izu-Bonin-Mariana (IBM) fore arc and in the Amami Sankaku Basin. The primary objective was to improve our understanding of supra-subduction zones (SSZ) and the process of subduction initiation. The recovered drill cores during IODP expedition 352 represent approximately 50 Ma old fore arc basalts (FAB) and boninites revealing an entire volcanic sequence of a SSZ. Expedition 351 drilled FAB like oceanic crust similar in age to the FABs of expedition 352. In this study we present data on vein microstructures, geochemical data and isotopic signatures of vein precipitates to give new insights into fluid flow and precipitation processes and deformation within the Izu-Bonin fore arc. Veins formed predominantly as a consequence of hydrofracturing resulting in the occurrence of branched vein systems and brecciated samples. Along these hydrofractures the amount of altered host rock fragments varies and locally alters the host rock completely to zeolites and carbonates. Subordinately extensional veins released after the formation of the host rocks. Cross-cutting relationships of different vein types point to multiple fracturing events subsequently filled with minerals originating from a fluid with isotopic seawater signature. Based on vein precipitates, their morphology and their growth patterns four vein types have been defined. Major vein components are (Mg-) calcite and various zeolites determined by Raman spectra and electron microprobe analyses. Zeolites result from alteration of volcanic glass during interaction with a seawaterlike fluid. Type I veins which are characterized by micritic infill represent neptunian dykes. They predominantly occur in the upper levels of drill cores being the result of an initial volume change subsequently to crystallization of the host rocks. Type II veins are

  17. Minimally invasive treatments for perforator vein insufficiency. (United States)

    Kuyumcu, Gokhan; Salazar, Gloria Maria; Prabhakar, Anand M; Ganguli, Suvranu


    Incompetent superficial veins are the most common cause of lower extremity superficial venous reflux and varicose veins; however, incompetent or insufficient perforator veins are the most common cause of recurrent varicose veins after treatment, often unrecognized. Perforator vein insufficiency can result in pain, skin changes, and skin ulcers, and often merit intervention. Minimally invasive treatments have replaced traditional surgical treatments for incompetent perforator veins. Current minimally invasive treatment options include ultrasound guided sclerotherapy (USGS) and endovascular thermal ablation (EVTA) with either laser or radiofrequency energy sources. Advantages and disadvantages of each modality and knowledge on these treatments are required to adequately address perforator venous disease.

  18. Prediction of calcite Cement Distribution in Shallow Marine Sandstone Reservoirs using Seismic Data

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, N.E.


    This doctoral thesis investigates how calcite cemented layers can be detected by reflection seismic data and how seismic data combined with other methods can be used to predict lateral variation in calcite cementation in shallow marine sandstone reservoirs. Focus is on the geophysical aspects. Sequence stratigraphy and stochastic modelling aspects are only covered superficially. Possible sources of calcite in shallow marine sandstone are grouped into internal and external sources depending on their location relative to the presently cemented rock. Well data and seismic data from the Troll Field in the Norwegian North Sea have been analysed. Tuning amplitudes from stacks of thin calcite cemented layers are analysed. Tuning effects are constructive or destructive interference of pulses resulting from two or more closely spaced reflectors. The zero-offset tuning amplitude is shown to depend on calcite content in the stack and vertical stack size. The relationship is found by regression analysis based on extensive seismic modelling. The results are used to predict calcite distribution in a synthetic and a real data example. It is found that describing calcite cemented beds in shallow marine sandstone reservoirs is not a deterministic problem. Hence seismic inversion and sequence stratigraphy interpretation of well data have been combined in a probabilistic approach to produce models of calcite cemented barriers constrained by a maximum amount of information. It is concluded that seismic data can provide valuable information on distribution of calcite cemented beds in reservoirs where the background sandstones are relatively homogeneous. 63 refs., 78 figs., 10 tabs.

  19. Acceleration of calcite kinetics by abalone nacre proteins

    Energy Technology Data Exchange (ETDEWEB)

    Fu, G; Qiu, S R; Orme, C A; Morse, D E; De Yoreo, J J


    The fascinating shapes and hierarchical designs of biomineralized structures have long been an inspiration to materials scientists because of the potential they suggest for biomolecular control over synthesis of crystalline materials. One prevailing view is that mineral-associated macromolecules are responsible for initiating and stabilizing non-equilibrium crystal polymorphs and morphologies through interactions between anionic moieties and cations in solution or at mineral surfaces. Indeed, numerous studies have demonstrated that bio-organic additives can dramatically alter crystal shapes and growth-rates in vitro. However, previous molecular-scale studies revealing mechanisms of growth modification focused on small molecules such as amino acids or peptides and always observed growth inhibition. In contrast, studies using full proteins were non-quantitative and underlying sources of growth modification were ill-defined. Here we investigate interactions between proteins isolated from abalone shell nacre and growing surfaces of calcite. We find that these proteins significantly accelerate the molecular-scale kinetics and, though much larger than atomic steps, alter growth morphology through step-specific interactions that lower their free energies. We propose that these proteins act as surfactants to promote ion attachment at calcite surfaces.

  20. Environmental controls on the Emiliania huxleyi calcite mass (United States)

    Horigome, M. T.; Ziveri, P.; Grelaud, M.; Baumann, K.-H.; Marino, G.; Mortyn, P. G.


    Although ocean acidification is expected to impact (bio)calcification by decreasing the seawater carbonate ion concentration, [CO32-], there exists evidence of non-uniform response of marine calcifying plankton to low seawater [CO32-]. This raises questions on the role of environmental factors other than acidification and on the complex physiological responses behind calcification. Here we investigate the synergistic effect of multiple environmental parameters, including temperature, nutrient (nitrate and phosphate) availability, and seawater carbonate chemistry on the coccolith calcite mass of the cosmopolitan coccolithophore Emiliania huxleyi, the most abundant species in the world ocean. We use a suite of surface (late Holocene) sediment samples from the South Atlantic and southwestern Indian Ocean taken from depths lying well above the modern lysocline. The coccolith calcite mass in our results presents a latitudinal distribution pattern that mimics the main oceanographic features, thereby pointing to the potential importance of phosphorus and temperature in determining coccolith mass by affecting primary calcification and possibly driving the E. huxleyi morphotype distribution. This evidence does not necessarily argue against the potentially important role of the rapidly changing seawater carbonate chemistry in the future, when unabated fossil fuel burning will likely perturb ocean chemistry beyond a critical point. Rather our study highlights the importance of evaluating the combined effect of several environmental stressors on calcifying organisms to project their physiological response(s) in a high CO2 world and improve interpretation of paleorecords.

  1. Molecular simulation of oligomer inhibitors for calcite scale

    Institute of Scientific and Technical Information of China (English)

    Qiuyu Zhang; Hua Ren; Wenwen Wang; Junping Zhang; Hepeng Zhang


    Molecular simulation was performed to study the interaction between CaCO3 crystal and several oligomer inhibitors,by using the equilibrium morphology method to calculate the growth morphology of CaCO3 without inhibitors.The calculated morphology agreed well with SEM photographs.Then,a double-layer model was built to investigate the interaction between calcite crystal and oligomer inhibitors containing maleic anhydride (MA) and acrylic acid (AA).Interaction energy per gram of an oligomer inhibitor was introduced as a scale of inhibition efficiency of different monomers.The results indicated that,for calcite scale inhibition,acrylamide (AM) and vinyl phosphonic acid (VPA) were the most efficient monomers,while allylsulfonic acid (AS) was the poorest.Increasing proportion of AM in dimer inhibitor molecule would improve the inhibition efficiency of MA,though,for a trimer,such as MA-AA-AM,certain sequence of monomers in the inhibitor molecule was necessary besides higher proportion of AM.

  2. Isotopic analysis for degradation diagnosis of calcite matrix in mortar. (United States)

    Dotsika, E; Psomiadis, D; Poutoukis, D; Raco, B; Gamaletsos, P


    Mortar that was used in building as well as in conservation and restoration works of wall paintings have been analysed isotopically (delta(13)C and delta(18)O) in order to evaluate the setting environments and secondary processes, to distinguish the structural components used and to determine the exact causes that incurred the degradation phenomena. The material undergoes weathering and decay on a large proportion of its surface and in depth, due to the infiltration of water through the structural blocks. Mineralogical analysis indicated signs of sulphation and dissolution/recrystallisation processes taking place on the material, whereas stable isotopes provided information relative to the origin of the CO(2) and water during calcite formation and degradation processes. Isotopic change of the initial delta(13)C and delta(18)O in carbonate matrix was caused by alteration of the primary source of CO(2) and H(2)O in mortar over time, particularly by recrystallisation of calcite with porewater, evaporated or re-condensed water, and CO(2) from various sources of atmospheric and biogenic origin. Human influence (surface treatment) and biological growth (e.g. fungus) are major exogenic processes which may alter delta(18)O and delta(13)C in lime mortar.

  3. Extrahepatic Portal Vein Obstruction and Portal Vein Thrombosis in Special Situations: Need for a New Classification (United States)

    Wani, Zeeshan A.; Bhat, Riyaz A.; Bhadoria, Ajeet S.; Maiwall, Rakhi


    Extrahepatic portal vein obstruction is a vascular disorder of liver, which results in obstruction and cavernomatous transformation of portal vein with or without the involvement of intrahepatic portal vein, splenic vein, or superior mesenteric vein. Portal vein obstruction due to chronic liver disease, neoplasm, or postsurgery is a separate entity and is not the same as extrahepatic portal vein obstruction. Patients with extrahepatic portal vein obstruction are generally young and belong mostly to Asian countries. It is therefore very important to define portal vein thrombosis as acute or chronic from management point of view. Portal vein thrombosis in certain situations such as liver transplant and postsurgical/liver transplant period is an evolving area and needs extensive research. There is a need for a new classification, which includes all areas of the entity. In the current review, the most recent literature of extrahepatic portal vein obstruction is reviewed and summarized. PMID:26021771

  4. Extrahepatic portal vein obstruction and portal vein thrombosis in special situations: Need for a new classification

    Directory of Open Access Journals (Sweden)

    Zeeshan A Wani


    Full Text Available Extrahepatic portal vein obstruction is a vascular disorder of liver, which results in obstruction and cavernomatous transformation of portal vein with or without the involvement of intrahepatic portal vein, splenic vein, or superior mesenteric vein. Portal vein obstruction due to chronic liver disease, neoplasm, or postsurgery is a separate entity and is not the same as extrahepatic portal vein obstruction. Patients with extrahepatic portal vein obstruction are generally young and belong mostly to Asian countries. It is therefore very important to define portal vein thrombosis as acute or chronic from management point of view. Portal vein thrombosis in certain situations such as liver transplant and postsurgical/liver transplant period is an evolving area and needs extensive research. There is a need for a new classification, which includes all areas of the entity. In the current review, the most recent literature of extrahepatic portal vein obstruction is reviewed and summarized.

  5. Interactions of arsenic with calcite surfaces revealed by in-situ nanoscale imaging (United States)

    Renard, Francois; Putnis, Christine; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hövelmann, Jörn; Sarret, Géraldine


    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in-situ study of calcite dissolution and growth in the presence of solutions with various amounts of As(III) or As(V). This was performed at room temperature and pH range 6-9 using a flow through cell connected to an atomic force microscope (AFM), to study the evolution of the (10-14) calcite cleavage surface morphology. Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  6. Angiosarcoma of common iliac vein (United States)

    Ibis, Kamuran; Usta, Ufuk; Cosar, Rusen; Ibis, Cem


    Angiosarcoma is a rare malignant tumour of endothelial cells. Primary angiosarcoma of venous origin is extremely rare, and has a very poor prognosis. A 63-year-old woman with retroperitoneal mass underwent en bloc resection on a part of iliac vein followed by adjuvant radiotherapy. No recurrence was detected during 3 years of follow-up. PMID:25596292

  7. Clinical studies on inferior right hepatic veins

    Institute of Scientific and Technical Information of China (English)

    Xue Xing; Hong Li; Wei-Guo Liu


    BACKGROUND:Many small veins are called accessory, short hepatic veins in addition to the right, middle and left hepatic veins. The size of these veins varied from a pinhole to 1 cm; the size of inferior right hepatic veins (IRHVs) is thicker than that of short hepatic veins or more than 1 cm occasionally. Adults have a higher incidence rate of the IRHV. DATA SOURCES:A literature search of the PubMed database was conducted and research articles were reviewed. RESULTS:The size of IRHVs is related to the size of the right hepatic vein, i.e. the larger the diameter of the right hepatic vein, the smaller the diameter of the IRHVs, and vice versa. The IRHVs are divided into superior, medial and inferior groups, separately named the superior, medial and inferior right hepatic veins according to the position of the IRHV entering the inferior vena cava. The superior right hepatic vein mainly drains the superior part of segmentⅦ, and the medial right hepatic vein drains the middle part of segmentⅦ. A thicker IRHV mainly drains segmentⅥ and the inferior part of segmentⅦ and a thinner IRHV drains the inferior part of segmentⅤ. CONCLUSIONS:The clinical signiifcance of these studies on IRHVs is varied: (1) Hepatic caudate lobe resection could be introduced after study on the veins of that lobe. (2) It is very important to identify the draining region of the IRHV for guiding hepatic segmentectomy. The postero-inferior area of the right lobe can be preserved along with the hypertrophic IRHV even if the entire main right hepatic vein is resected during segmentectomy ofⅦ andⅧwith right hepatic vein resection for patients with primary liver cancer. (3) The ligation of the major hepatic vein for the treatment of juxtahepatic vein injury is recommended because of severe hemorrhagic shock and dififculty in

  8. Kinetics and Mechanisms of Calcite Reactions with Saline Waters

    Energy Technology Data Exchange (ETDEWEB)

    Gorman, Brian P [Colorado School of Mines, Golden, CO (United States)


    Project Description: The general objective of the proposed research is to determine the kinetics and mechanisms of calcite reactions with saline waters over a wide range of saline water composition, pCO2, and modest ranges in T and P. This will be accomplished by studying both reaction rates and solubility from changes in solution chemistry, and making nanoscale observations of calcite precipitate surface morphology and composition at the micro-to-nano-scale to provide an understanding of controlling reaction mechanisms and pathways. The specific objectives necessary to reach the general objective are: a) determination of how pCO2, Ca2+, ionic strength and “foreign” ions influence reaction rates; and b) investigate the influence of these parameters on apparent kinetic solubility from dissolution and precipitation reactions. This information will clearly be central to the construction of reliable reaction-transport models to predict reservoir and formation response to increased CO2 in saline waters. This program was initially collaborative with John Morse at Texas A&M, however his passing shortly after the beginning of this program resulted in abbreviated research time and effort. Summary of Results: Early studies using electron microscopy and spectroscopy indicated that carbonate precipitation from natural seawater (NSW) conditions onto aragonite substrates was mediated by a surface amorphous calcium carbonate layer. It was hypothesized that this ACC layer (observed after < 5days reaction time) was responsible for the abnormal reaction kinetics and also served as a metastable seed layer for growth of epitaxial aragonite. Further studies of the ACC formation mechanism indicated a strong dependence on the Mg concentration in solution. Subsequent studies at shorter times (10 hrs) on calcite substrates and in a wide range of supersaturation conditions did not indicate any ACC layer. Instead, an epitaxial layer by layer

  9. Common femoral vein reconstruction using internal jugular vein after blast injury. (United States)

    Holt, Andrew M; West, Charles A; Davis, James A; Gilani, Ramyar; Askenasy, Eric


    Common femoral vein traumatic injuries are rare. Surgical management is controversial and by nature case specific. In this report, we present an unusual case of an isolated common femoral vein injury from a gunshot blast repaired with an interposition internal jugular vein bypass. To our knowledge, this is the first reported case of an isolated common femoral vein reconstructed in this manner.

  10. Who Is at Risk for Varicose Veins? (United States)

    ... may raise your risk for varicose veins. The normal wear and tear of aging may cause the valves in your veins to weaken and not work well. Gender Women tend to get varicose veins more often than men. Hormonal changes that occur during puberty, pregnancy, and menopause (or ...

  11. Cephalic veins in coronary artery bypass surgery

    DEFF Research Database (Denmark)

    Licht, P; Jakobsen, Erik; Lerbjerg, G


    Various alternative conduits for aortocoronary bypass grafting have been suggested when the saphenous vein quality is inadequate. During a 10-year period we have used the cephalic vein in 39 patients. Eighteen entered an angiographic follow-up study. A total of 31 arm vein grafts were used with 4...

  12. Radiological aspects of portal vein embolization

    NARCIS (Netherlands)

    van Lienden, K.P.


    This thesis deals with liver regeneration after portal vein embolization (PVE) or portal vein ligation (PVL). Several aspects of these portal vein occlusion techniques are evaluated in clinical and experimental studies. In addition, the role of dynamic liver function tests and CT-volumetry in risk a

  13. Cephalic veins in coronary artery bypass surgery

    DEFF Research Database (Denmark)

    Licht, P; Jakobsen, Erik; Lerbjerg, G;


    Various alternative conduits for aortocoronary bypass grafting have been suggested when the saphenous vein quality is inadequate. During a 10-year period we have used the cephalic vein in 39 patients. Eighteen entered an angiographic follow-up study. A total of 31 arm vein grafts were used with 4...

  14. Dependence of calcite growth rate and Sr partitioning on solution stoichiometry: Non-Kossel crystal growth

    NARCIS (Netherlands)

    Nehrke, G.; Reichart, G.-J.; Van Cappellen, P.; Meile, C.; Bijma, J.


    Seeded calcite growth experiments were conducted at fixed pH (10.2) and two degrees of supersaturation (Ω = 5, 16), while varying the Ca2+ to CO3 2- solution ratio over several orders of magnitude. The calcite growth rate and the incorporation of Sr in the growing crystals strongly depended on

  15. Biotic control of skeletal growth by scleractinian corals in aragonite-calcite seas.

    Directory of Open Access Journals (Sweden)

    Tomihiko Higuchi

    Full Text Available Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas.

  16. Ethanol adsorption on the {10(1)over-bar4} calcite surface

    DEFF Research Database (Denmark)

    Sand, Karina Krarup; Stipp, Susan Louise Svane; Hassenkam, Tue


    Preliminary atomic force microscopy investigations of the {10 (1) over bar4} calcite Surface cleaved in ethanol indicate a different surface behaviour than that of the {10 (1) over bar4} surface cleaved in air. The results are consistent with recent theoretical studies and suggest strong ordering...... of ethanol over the termination of the bulk calcite structure....

  17. Shock-induced effects in calcite from Cactus Crater (United States)

    Vizgirda, J.; Ahrens, T. J.; Tsay, F.-D.


    The paper discusses shock metamorphism of calcite from coralline limestone samples retrieved from a borehole drilled into rocks beneath Cactus Crater, a nuclear explosion crater at Eniwetok Atoll. The metamorphism was detected and quantified using electron spin resonance (ESR); the ESR spectra of Mn(+) present as a trace constituent in the coral samples, show a consistent decrease in hyperfine peak splitting with decreasing depth of sample. It is suggested that the decrease in hyperfine peak splitting reflects a decrease in crystal field splitting, and therefore, small increases on cation-anion distances produced by mechanical energy input during the shock process. Two alternative crater models suggested by the ESR results are a depiction of a steady decay of the shock wave, and a delineation of a breccia lens with a breccia-bedrock interface at 20 plus or minus 5 m.

  18. Microstructural observations on hydrothermal veins of Site U1414, IODP Expedition 344 (CRISP 2) (United States)

    Brandstätter, Jennifer; Kurz, Walter; Rogowitz, Anna


    The erosive active margin offshore Osa Peninsula (Costa Rica) is characterized by the subducting Cocos Plate with its topographic height, the aseismic Cocos Ridge, which has lifted the seismogenic zone in the reach of scientific drilling. To understand the processes occurring in the subducting Cocos Plate in the vicinity to the Middle America Trench, we investigated microstructures in hydrothermal veins, transecting the lithified sediments and the igneous basement of IODP Hole U-1414A. Mechanical e-twinning occurred mainly in the blocky calcite veins in the lithified sediments, rather than in the fibrous calcite veins within the Cocos Ridge basalt. The differential stress, obtained from two different piezometers, indicate mean differential stresses of approximately 53 and 82 MPa. The majority of the twins show a significant thickness (up to 120 µm), straight twin boundaries and are indicative for deformation temperatures between 150 to 300°C. The presence of additional deformation structures, such as undulose extinction and subgrain boundaries, indicates intracrystalline-plastic deformation by dislocation creep. The comparison of the EBSD data from two samples within the lithified sedimentary unit indicates diverse deformation temperatures. Variation in subgrain size observed for the different samples can be related to local variations in differential stress. The results of different microstructural observations showed, that the deformational history of Site 344-U1414 is characterized by distinct tectonic phases, occurring during the movement of the Cocos Ridge from its location of origin (the Galapagos hotspot) to the convergent margin offshore Costa Rica. The causes for these changes in deformation mechanisms in the studied rocks are ascribed to magmatic advection resulting in an increase of temperature and decrease of critical resolved shear stresses, as well as the bending of the Cocos plate adjacent to the Middle American trench.

  19. A global deglacial negative carbon isotope excursion in speleothem calcite (United States)

    Breecker, D.


    δ13C values of speleothem calcite decreased globally during the last deglaciation defining a carbon isotope excursion (CIE) despite relatively constant δ13C values of carbon in the ocean-atmosphere system. The magnitude of the CIE varied with latitude, increasing poleward from ~2‰ in the tropics to as much as 7‰ at high latitudes. This recent CIE provides an interesting comparison with CIEs observed in deep time. A substantial portion of this CIE can be explained by the increase in atmospheric pCO2 that accompanied deglaciation. The dependence of C3 plant δ13C values on atmospheric pCO2 predicts a 2‰ δ13C decrease driven by the deglacial pCO2 increase. I propose that this signal was transferred to caves and thus explains nearly 100% of the CIE magnitude observed in the tropics and no less than 30% at the highest latitudes in the compilation. An atmospheric pCO2 control on speleothem δ13C values, if real, will need to be corrected for using ice core data before δ13C records can be interpreted in a paleoclimate context. The decrease in the magnitude of the equilibrium calcite-CO2 carbon isotope fractionation factor explains a maximum of 1‰ of the CIE at the highest northern latitude in the compilation, which experienced the largest deglacial warming. Much of the residual extratropical CIE was likely driven by increasing belowground respiration rates, which were presumably pronounced at high latitudes as glacial retreat exposed fresh surfaces and/or vegetation density increased. The largest increases in belowground respiration would have therefore occurred at the highest latitudes, explaining the meridional trend. This work supports the notion that increases in atmospheric pCO2 and belowground respiration rates can result in large CIEs recorded in terrestrial carbonates, which, as previously suggested, may explain the magnitude of the PETM CIE as recorded by paleosol carbonates.

  20. Sorption of phosphate onto calcite; results from batch experiments and surface complexation modeling

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus;


    The adsorption of phosphate onto calcite was studied in a series of batch experiments. To avoid the precipitation of phosphate-containing minerals the experiments were conducted using a short reaction time (3h) and low concentrations of phosphate (⩽50μM). Sorption of phosphate on calcite...... was studied in 11 different calcite-equilibrated solutions that varied in pH, PCO2, ionic strength and activity of Ca2+, CO32- and HCO3-. Our results show strong sorption of phosphate onto calcite. The kinetics of phosphate sorption onto calcite are fast; adsorption is complete within 2–3h while desorption...... of a high degree of super-saturation with respect to hydroxyapatite (SIHAP⩽7.83). The amount of phosphate adsorbed varied with the solution composition, in particular, adsorption increases as the CO32- activity decreases (at constant pH) and as pH increases (at constant CO32- activity). The primary effect...

  1. Unusual micrometric calcite-aragonite interface in the abalone shell Haliotis (Mollusca, Gastropoda). (United States)

    Dauphin, Yannicke; Cuif, Jean-Pierre; Castillo-Michel, Hiram; Chevallard, Corinne; Farre, Bastien; Meibom, Anders


    Species of Haliotis (abalone) show high variety in structure and mineralogy of the shell. One of the European species (Haliotis tuberculata) in particular has an unusual shell structure in which calcite and aragonite coexist at a microscale with small patches of aragonite embedded in larger calcitic zones. A detailed examination of the boundary between calcite and aragonite using analytical microscopies shows that the organic contents of calcite and aragonite differ. Moreover, changes in the chemical composition of the two minerals seem to be gradual and define a micrometric zone of transition between the two main layers. A similar transition zone has been observed between the layers in more classical and regularly structured mollusk shells. The imbrication of microscopic patches of aragonite within a calcitic zone suggests the occurrence of very fast physiological changes in these taxa.

  2. Influence of surface conductivity on the apparent zeta potential of calcite

    CERN Document Server

    Li, Shuai; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe


    Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength < 0.01 M) because of calcite surface conductivity. The basic Stern model successfully predicted ...

  3. A New Multimodal Biometric System Based on Finger Vein and Hand Vein Recognition


    Randa Boukhris Trabelsi; Alima Damak Masmoudi; Dorra Sellami Masmoudi


    As a reliable and robust biological characteristic, the vein pattern increases more and more the progress in biometric researches. Generally, it was shown that single biometric modality recognition is not able to meet high performances. In this paper, we propose a new multimodal biometric system based on fusion of both hand vein and finger vein modalities. For finger vein recognition, we employ the Monogenic Local Binary Pattern (MLBP), and for hand vein recognitionan Improved Gaussian Matche...

  4. Recurrence of superficial vein thrombosis in patients with varicose veins. (United States)

    Karathanos, Christos; Spanos, Konstantinos; Saleptsis, Vassileios; Tsezou, Aspasia; Kyriakou, Despina; Giannoukas, Athanasios D


    To investigate which factors other than history of superficial vein thrombosis (SVT) are associated with recurrent spontaneous SVT episodes in patients with varicose veins (VVs). Patients with a history of spontaneous SVT and VVs were followed up for a mean period of 55 months. Demographics, comorbidities, and thrombophilia screening test were analyzed. Patients were grouped according to the clinical-etiology-anatomy-pathophysiology classification. A multiple logistic regression analysis with the forward likelihood ratio method was undertaken. Thirteen patients out of 97 had a recurrence SVT episode during the follow-up period. All those patients were identified to have a thrombophilia defect. Protein C and S, antithrombin, and plasminogen deficiencies were more frequently present in patients without recurrence. Gene mutations were present in 38% in the nonrecurrence group and 77% in the recurrence group. After logistic regression analysis, patients with dislipidemia and mutation in prothrombin G20210A (FII) had an increased risk for recurrence by 5.4-fold and 4.6-fold, respectively. No deep vein thrombosis or pulmonary embolism occurred. Dislipidemia and gene mutations of F II are associated with SVT recurrence in patients with VVs. A selection of patients may benefit from anticoagulation in the short term and from VVs intervention in the long term. © The Author(s) 2015.

  5. Interactions of arsenic with calcite surfaces revealed by in situ nanoscale imaging (United States)

    Renard, François; Putnis, Christine V.; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hovelmann, Jörn; Sarret, Géraldine


    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in situ study of the evolution of the (10-14) calcite cleavage surface morphology during dissolution and growth in the presence of solutions with various amounts of As(III) or As(V) at room temperature and pH range 6-11 using a flow-through cell connected to an atomic force microscope (AFM). Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  6. Management of varicose veins and venous insufficiency. (United States)

    Hamdan, Allen


    Chronic venous disease, reviewed herein, is manifested by a spectrum of signs and symptoms, including cosmetic spider veins, asymptomatic varicosities, large painful varicose veins, edema, hyperpigmentation and lipodermatosclerosis of skin, and ulceration. However, there is no definitive stepwise progression from spider veins to ulcers and, in fact, severe skin complications of varicose veins, even when extensive, are not guaranteed. Treatment options range from conservative (eg, medications, compression stockings, lifestyle changes) to minimally invasive (eg, sclerotherapy or endoluminal ablation), invasive (surgical techniques), and hybrid (combination of ≥1 therapies). Ms L, a 68-year-old woman with varicose veins, is presented. She has had vein problems over the course of her life. Her varicose veins recurred after initial treatment, and she is now seeking guidance regarding her current treatment options.


    Tezuka, Masahiro; Kanaoka, Yuji; Ohki, Takao


    Varicose veins are a common condition attecting approximately 10 million patients in Japan. The main cause of varicose veins is reflux of the saphenous vein, and conventional treatment for several decades was stripping the affected saphenous vein and phlebectomy. Endovenous laser treatment (EVLT) is a less-invasive treatment method in which the saphenous vein is ablated with a laser under local anesthesia. EVLT has been approved by the Japanese Ministry of Health, Labor and Welfare since 2011, and we have performed EVLT on 5,160 legs with saphenous insufficiency with no severe complications including deep vein thrombosis except for one case of arteriovenous fistula. EVLT appears to be a safe, effective treatment option for varicose veins with saphenous insufficiency.

  8. Deep vein thrombosis in pregnancy. (United States)

    Colman-Brochu, Stephanie


    This article provides a review of the incidence, pathophysiology, and treatment of deep vein thrombosis (DVT) in pregnancy, a rare but serious complication of pregnancy. The incidence of DVT in pregnancy varies widely, but it is a leading cause of maternal morbidity in both the United States and the United Kingdom. Risk factors during pregnancy include prolonged bed rest or immobility, pelvic or leg trauma, and obesity. Additional risk factors are preeclampsia, Cesarean section, instrument-assisted delivery, hemorrhage, multiparity, varicose veins, a previous history of a thromboembolic event, and hereditary or acquired thrombophilias such as Factor V Leiden. Heparin is the anticoagulant of choice to treat active thromboembolic disease or to administer for thromboprophylaxis, but low molecular-weight heparin is being used with increasing frequency in the pregnant woman. Perinatal nurses should be aware of the symptoms, diagnostic tools, and treatment options available to manage active thrombosis during pregnancy and in the intrapartum and postpartum periods.


    Directory of Open Access Journals (Sweden)

    A.Haritha Deepthi


    Full Text Available As the Person‟s/Organization‟s Private information‟s are becoming very easy to access, the demand for a Simple, Convenient, Efficient, and a highly Securable Authentication System has been increased. In considering these requirements for data Protection, Biometrics, which uses human physiological or behavioral system for personal Identification has been found as a solution for these difficulties. However most of the biometric systems have high complexity in both time and space. So we are going to use a Real time Finger-Vein recognition System for authentication purposes. In this paper we had implemented the Finger Vein Recognition concept using MATLAB R2013a. The features used are Lacunarity Distance, Blanket Dimension distance. This has more accuracy when compared to conventional methods.

  10. Mortality after portal vein embolization (United States)

    Lee, Eung Chang; Park, Sang-Jae; Han, Sung-Sik; Park, Hyeong Min; Lee, Seung Duk; Kim, Seong Hoon; Lee, In Joon; Kim, Hyun Beom


    Abstract Portal vein embolization (PVE) is increasingly performed worldwide to reduce the possibility of liver failure after extended hepatectomy, by inducing future liver remnant (FLR) hypertrophy and atrophy of the liver planned for resection. The procedure is known to be very safe and to have few procedure-related complications. In this study, we described 2 elderly patients with Bismuth–Corlette type IV Klatskin tumor who underwent right trisectional PVE involving the embolization of the right portal vein, the left medial sectional portal branch, and caudate portal vein. Within 1 week after PVE, patients went into sepsis combined with bile leak and died within 1 month. Sepsis can cause acute liver failure in patients with chronic liver disease. In this study, the common patient characteristics other than sepsis, that is, trisectional PVE; chronic alcoholism; aged >65 years; heart-related comorbidity; and elevated serum total bilirubin (TB) level (7.0 mg/dL) at the time of the PVE procedure in 1 patient, and concurrent biliary procedure, that is, percutaneous transhepatic biliary drainage in the other patient might have affected the outcomes of PVE. These cases highlight that PVE is not a safe procedure. Care should be taken to minimize the occurrence of infectious events because sepsis following PVE can cause acute liver failure. Additionally, prior to performing PVE, the extent of PVE, chronic alcohol consumption, age, comorbidity, long-lasting jaundice, concurrent biliary procedure, etc. should be considered for patient safety. PMID:28178122

  11. Infrared spectroscopy and density functional theory investigation of calcite, chalk, and coccoliths-do we observe the mineral surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Hem, Caroline Piper; Schultz, Logan Nicholas


    We have measured infrared spectra from several types of calcite: chalk, freshly cultured coccoliths produced by three species of algae, natural calcite (Iceland Spar), and two types of synthetic calcite. The most intense infrared band, the asymmetric carbonate stretch vibration, is clearly asymme...

  12. Meso- and microscale vein structures in fore-arc basalts and boninites related to post-magmatic tectonic deformation in the outer Izu-Bonin-Mariana fore arc system: preliminary results from IODP Expedition 352 (United States)

    Quandt, Dennis; Micheuz, Peter; Kurz, Walter


    The International Ocean Discovery Program (IODP) Expedition 352 aimed to drill through the entire volcanic sequence of the Izu-Bonin-Mariana fore arc. Two drill sites are situated on the outer fore arc composed of fore arc basalts (FAB) whereas two more sites are located on the upper trench slope penetrating the younger boninites. First results from IODP Expedition 352 and preliminary post-cruise data suggest that FAB were generated by decompression melting during near-trench sea-floor spreading, and that fluids from the subducting slab were not involved in their genesis. Subduction zone fluids involved in boninite genesis appear to have been derived from progressively higher temperatures and pressures over time as the subducting slab thermally matured. Structures within the drill cores combined with borehole and site survey seismic data indicate that tectonic deformation in the outer Izu-Bonin-Mariana fore arc is mainly post-magmatic associated with the development of syn-tectonic sedimentary basins. Within the magmatic basement deformation was accommodated by shear along cataclastic fault zones and the formation of tension fractures, shear fractures and hybrid (tension and shear) fractures. Veins form by mineral filling of tension or hybrid fractures and show no or limited observable macroscale displacement along the fracture plane. (Low Mg-) Calcite and/or various types of zeolite are the major vein constituents, where the latter are considered to be alteration products of basaltic glass. Micrite contents vary significantly and are related to neptunian dikes. In boninites calcite develops mainly blocky shapes but veins with fibrous and stretched crystals also occur in places indicating antitaxial as well as ataxial growth, respectively. In FAB calcite forms consistently blocky crystals without any microscopic identifiable growth direction suggesting precipitation from a highly supersaturated fluid under dropping fluid pressure conditions. However, fluid pressure

  13. Aragonite-calcite transformation in fossil snail shells of loess sequences in Loess Plateau, Central China

    Institute of Scientific and Technical Information of China (English)

    SHENG Xuefen; CHEN Jun; CAI Yuanfeng; CHEN Yang; JI Junfeng


    The methods of X-ray diffraction (XRD) and ICP-AES are applied to analyzing the mineral composition of modern and fossil snail shells in Luochuan section and Xifeng section. The results show that the mineral phase of calcium carbonate in modern snail shells is aragonite, but for some fossil snail shells in certain layers of loess sequences, a part of aragonite is transformed into calcite. In Luochuan and Xifeng sections, the stratigraphic borderline of aragonite-calcite transformation appearing obviously is between L5 and L6. Under the earth surface condition, the aragonite-calcite transformation is influenced by the factor of temperature only in a long time scale. It seems that the pressure is not the factor influencing the aragonite-calcite transformation. The results also show that existing age of snail shells is possibly the dominant and principal factor for the aragonite-calcite transformation. To a certain extent, the degree of aragonite-calcite transformation in snail shell is controlled by the content of trace element, such as Mg2+. The trace element can improve the stability of snail shell aragonite and impede the process of aragonite transforming into calcite.

  14. Influence of surface conductivity on the apparent zeta potential of calcite. (United States)

    Li, Shuai; Leroy, Philippe; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe


    Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength ⩽ 0.01 M) because of calcite surface conductivity. The basic Stern model successfully predicted the corrected zeta potential by assuming that the zeta potential is located at the outer Helmholtz plane, i.e. without considering a stagnant diffuse layer at the calcite-water interface. The surface conductivity of calcite crystals was inferred from electrical conductivity measurements and computed using our basic Stern model. Surface conductivity was also successfully predicted by our surface complexation model.

  15. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum. (United States)

    Offeddu, Francesco Giancarlo; Cama, Jordi; Soler, Josep Maria; Putnis, Christine V


    In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours.

  16. Fabrication of porous calcite using chopped nylon fiber and its evaluation using rats. (United States)

    Ishikawa, Kunio; Tram, Nguyen Xuan Thanh; Tsuru, Kanji; Toita, Riki


    Although porous calcite has attracted attention as bone substitutes, limited studies have been made so far. In the present study, porous calcite block was fabricated by introducing chopped nylon fiber as porogen. Ca(OH)2 powder containing 10 wt% chopped nylon fiber was compacted at 150 MPa, and sintered to burn out the fiber and to carbonate the Ca(OH)2 under stream of 1:2 O2-CO2. Sintering of Ca(OH)2 at 750 °C or lower temperature resulted in incomplete burning out of the fiber whereas sintering at 800 °C or higher temperature resulted in the formation of CaO due to the thermal decomposition of Ca(OH)2. However, sintering at 770 °C resulted in complete burning out of the fiber and complete carbonation of Ca(OH)2 to calcite without forming CaO. Macro- and micro-porosities of the porous calcite were approximately 23 and 16%, respectively. Diameter of the macropores was approximately 100 μm which is suitable for bone tissue penetration. Porous calcite block fabricated by this method exhibited good tissue response when implanted in the bone defect in femur of 12-weeks-old rat. Four weeks after implantation, bone bonded on the surface of calcite. Furthermore, bone tissue penetrated interior to the macropore at 8 weeks. These results demonstrated the good potential value of porous calcite as artificial bone substitutes.

  17. Undivided Retromandibular Vein Continuing As External Jugular Vein With Facial Vein Draining Into It : An Anatomical Variation

    Directory of Open Access Journals (Sweden)

    Shahnaz Choudhary, Ashwani K Sharma, Harbans Singh


    Full Text Available Despite the fact that the blueprint of the whole body is unravelled, faultlessly during the growth anddevelopment of an animal; but amazingly variations do occur. During routine dissection of head and neckin a middle aged cadaver in the Post Graduate Department of Anatomy of this medical college, we foundvariation in the formation of external jugular vein on both sides, which was formed by the continuation ofundivided trunk of retromandibular vein. The facial vein and posterior auricular vein were the tributaries ofexternal jugular vein. The sound anatomical knowledge of variations of the veins of head and neck isessential to the success of surgical procedures. The embryological evaluation of the above anomaly wasdone and compared with the available literature which showed that the observed variation was rare

  18. Uranium isotope fractionation during coprecipitation with aragonite and calcite (United States)

    Chen, Xinming; Romaniello, Stephen J.; Herrmann, Achim D.; Wasylenki, Laura E.; Anbar, Ariel D.


    Natural variations in 238U/235U of marine calcium carbonates might provide a useful way of constraining redox conditions of ancient environments. In order to evaluate the reliability of this proxy, we conducted aragonite and calcite coprecipitation experiments at pH ∼7.5 and ∼8.5 to study possible U isotope fractionation during incorporation into these minerals. Small but significant U isotope fractionation was observed in aragonite experiments at pH ∼8.5, with heavier U isotopes preferentially enriched in the solid phase. 238U/235U of dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00007 + 0.00002/-0.00003, 1.00005 ± 0.00001, and 1.00003 ± 0.00001. In contrast, no resolvable U isotope fractionation was observed in an aragonite experiment at pH ∼7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among different aqueous U species is the most likely explanation for these findings. Certain charged U species are preferentially incorporated into calcium carbonate relative to the uncharged U species Ca2UO2(CO3)3(aq), which we hypothesize has a lighter equilibrium U isotope composition than most of the charged species. According to this hypothesis, the magnitude of U isotope fractionation should scale with the fraction of dissolved U that is present as Ca2UO2(CO3)3(aq). This expectation is confirmed by equilibrium speciation modeling of our experiments. Theoretical calculation of the U isotope fractionation factors between different U species could further test this hypothesis and our proposed fractionation mechanism. These findings suggest that U isotope variations in ancient carbonates could be controlled by changes in the aqueous speciation of seawater U, particularly changes in seawater pH, PCO2 , Ca2+, or Mg2+ concentrations. In general, these effects are likely to be small (<0.13‰), but are nevertheless potentially significant because of the small natural range of

  19. The umbilical and paraumbilical veins of man. (United States)

    Martin, B F; Tudor, R G


    During its transit through the umbilicus structural changes occur in the thick wall of the extra-abdominal segment of the umbilical vein whereby the components of the intra-abdominal segment acquire an essentially longitudinal direction and become arranged in fibro-elastic and fibro-muscular zones. The vein lumen becomes largely obliterated by asymmetrical proliferation of loose subendothelial conective tissue. The latter forms a new inner zone within which a small segment of the lumen persists in an eccentric position. This residual lumen transmits blood to the portal system from paraumbilical and systemic sources, and is retained in the upper part of the vein, even in old age. A similar process of lumen closure is observed in the ductus venosus. In early childhood the lower third of the vein undergoes breakdown, with fatty infiltration, resulting in its complete division into vascular fibro-elastic strands, and in old age some breakdown occurs in the outermost part of the wall of the upper two thirds. The paraumbilical veins are thick-walled and of similar structure to the umbilical vein. Together they constitute an accessory portal system which is confined between the layers of the falciform ligament and is in communication with the veins of the ventral abdominal wall. The constituents form an ascending series, namely, Burow's veins, the umbilical vein, and Sappey's inferior and superior veins. The main channel of Sappey's inferior veins may be the remnant of the right umbilical vein since it communicates with the right rectus sheath and often communicates directly with the portal system within the right lobe of the liver. The results are of significance in relation to clinical usage of the umbilical vein.

  20. Calcite Formation in Soft Coral Sclerites Is Determined by a Single Reactive Extracellular Protein* (United States)

    Rahman, M. Azizur; Oomori, Tamotsu; Wörheide, Gert


    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called “calcite and aragonite seas.” Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that –OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature. PMID:21768106

  1. Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein. (United States)

    Rahman, M Azizur; Oomori, Tamotsu; Wörheide, Gert


    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called "calcite and aragonite seas." Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that -OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature.

  2. The potential for phosphorus pollution remediation by calcite precipitation in UK freshwaters

    Directory of Open Access Journals (Sweden)

    C. Neal


    Full Text Available This paper examines the potential for calcium carbonate to reduce phosphate pollution in freshwaters by co-precipitation, a process known as a "self cleansing mechanism". Calcium carbonate saturation levels and phosphate concentrations (SRP - soluble reactive phosphate across the major eastern UK river basins are examined to test for solubility controls. The study shows that calcite saturation varies for each catchment as a function of flow and biological activity rather than by direct regulation by SRP. Indeed, there is no evidence, for any of the rivers studied, that calcite solubility controls hold. However, for groundwater and groundwater-fed springs in the Chalk of the Thames basin, calcite saturation is observed with associated low SRP levels. A self-cleansing mechanism may well be operative within the Chalk due to two factors. Firstly, there is a high potential for nucleation on the calcite micro-crystals in the aquifer. Secondly, there are within aquifer reactions that remove the calcite nucleating inhibitors (SRP and dissolved organic carbon, DOC to levels lower than those occurring within the rivers do. These inhibitors enter the catchment at very high concentrations in association with agricultural pollution (fertilizer application and animal slurry and household contamination (e.g. sewage sources from septic tanks. Under low flow conditions, when the saturation index for calcite is at its highest, so too is the concentration of the nucleation inhibitor SRP. Companion work shows that calcite precipitation can occur at the water-sediment interface of the river and this may involve SRP removal. The data, as a whole, define an apparent bound for calcite solubility control where in the presence of nucleating centres, SRP must be less than 4 mM-P l-1 and DOC must be less than 150 mM-C l-1: a condition that does not seem to pertain within most UK rivers. Keywords: calcite, calcium carbonate, phosphate, soluble reactive phosphate, dissolved

  3. Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization

    DEFF Research Database (Denmark)

    Sand, K K; Yang, M; Makovicky, E;


    adsorption on calcite relative to OH from water and the consequences of the differences in interaction on crystal growth and dissolution. A combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations showed that EtOH attachment on calcite is stronger than HOH binding...... to the surface. The strong influence of calcite in structuring ethanol extends further into the liquid than expected from electrical double-layer theory. This suggests that in fluids where water activity is low, such as in biological systems optimized for biomineralization, organic molecules can control ion...

  4. Recurrent Pure Calcite Urolithiasis Confirmed by Endoscopic Removal and Infrared Spectroscopy in a Malnourished Anorectic Female (United States)

    Andreassen, Kim Hovgaard; Sloth Osther, Palle Jörn


    Abstract Often when calcite is found as a component of urinary calculi, they are considered false calculi or artifacts. We present a case of true calcite urolithiasis. The stone material was removed percutaneously from a severely malnourished anorectic woman and analyzed by infrared spectroscopy (IRS). In addition, calcite urolithiasis was confirmed in several recurrent stone events by IRS. Laxative abuse with magnesium oxide was believed to be the underlying cause of stone formation, and ammonium chloride given as one weekly dose turned out to be effective for stone prevention. PMID:27579419

  5. Comparison of galvanic displacement and electroless methods for deposition of gold nanoparticles on synthetic calcite

    Indian Academy of Sciences (India)

    Chamarthi K Srikanth; P Jeevanandam


    Gold nanoparticles have been deposited on synthetic calcite substrate by galvanic displacement reaction and electroless deposition methods. A comparative study has shown that electroless deposition is superior compared to galvanic displacement reaction for uniform deposition of gold nanoparticles on calcite. Characterization of the samples, prepared by two different deposition methods, was carried out by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy (FE–SEM) and diffuse reflectance spectroscopy (DRS) measurements. FE–SEM studies prove that smaller nanoparticles of gold are deposited uniformly on calcite if electroless deposition method was employed and DRS measurements show the characteristic surface plasmon resonance of gold nanoparticles.

  6. Fluid transfer and vein thickness distribution in high and low temperature hydrothermal systems at shallow crustal level in southern Tuscany (Italy

    Directory of Open Access Journals (Sweden)

    Francesco Mazzarini


    Full Text Available Geometric analysis of vein systems hosted in upper crustal rocks and developed in high and low temperature hydrothermal systems is presented. The high temperature hydrothermal system consists of tourmaline-rich veins hosted within the contact aureole of the upper Miocene Porto Azzurro pluton in the eastern Elba Island. The low temperature hydrothermal system consists of calcite-rich veins hosted within the Oligocene sandstones of the Tuscan Nappe, exposed along the coast in southern Tuscany. Vein thickness distribution is here used as proxy for inferring some hydraulic properties (transmissivity of the fluid circulation at the time of veins’ formation. We derive estimations of average thickness of veins by using the observed distributions. In the case of power law thickness distributions, the lower the scaling exponent of the distribution the higher the overall transmissivity. Indeed, power law distributions characterised by high scaling exponents have transmissivity three order of magnitude lower than negative exponential thickness distribution. Simple observations of vein thickness may thus provides some clues on the transmissivity in hydrothermal systems.

  7. Calcite-forming bacteria for compressive strength improvement in mortar. (United States)

    Park, Sung-Jin; Park, Yu-Mi; Chun, Woo-Young; Kim, Wha-Jung; Ghim, Sa-Youl


    Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of concrete mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of concrete mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and x-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the CaCO3 crystals. We used the isolates to improve the compressive strength of concrete mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

  8. Alkaline flocculation of Phaeodactylum tricornutum induced by brucite and calcite. (United States)

    Vandamme, Dries; Pohl, Philip I; Beuckels, Annelies; Foubert, Imogen; Brady, Patrick V; Hewson, John C; Muylaert, Koenraad


    Alkaline flocculation holds great potential as a low-cost harvesting method for marine microalgae biomass production. Alkaline flocculation is induced by an increase in pH and is related to precipitation of calcium and magnesium salts. In this study, we used the diatom Phaeodactylum tricornutum as model organism to study alkaline flocculation of marine microalgae cultured in seawater medium. Flocculation started when pH was increased to 10 and flocculation efficiency reached 90% when pH was 10.5, which was consistent with precipitation modeling for brucite or Mg(OH)2. Compared to freshwater species, more magnesium is needed to achieve flocculation (>7.5mM). Zeta potential measurements suggest that brucite precipitation caused flocculation by charge neutralization. When calcium concentration was 12.5mM, flocculation was also observed at a pH of 10. Zeta potential remained negative up to pH 11.5, suggesting that precipitated calcite caused flocculation by a sweeping coagulation mechanism.

  9. Ultrasonic Observation of the Calcite-Aragonite Transition (United States)

    Ahrens, T. J.; Katz, S.


    Elastic-wave velocities were measured as a function of pressure by ultrasonic pulse Interferometry in Solenhofen and Manilus limestone specimens to pressures of 27 and 38 kb. Longitudinal velocities decrease sharply from 5.3 km/sec at a mean pressure of 4 kb to a minimum of 4.8 km/sec at 8 kb. Transverse velocities decrease from 3.1 to 2.9 km/sec. At the minimum bulk and rigidity moduli are 25 and 20 per cent below their 4-kb values. A density increase of 1.7 per cent is associated with this minimum. The observed effects are attributed to the calcite-aragonite transition, and they may be due to an inherent property of the material, a component of which undergoes a polymorphic transition, the low- and high-pressure phases coexisting over a considerable pressure range. This may be an additional mechanism to account for low-velocity zones in the earth?s interior.

  10. Face-specific Replacement of Calcite by Amorphous Silica Nanoparticles (United States)

    Liesegang, M.; Milke, R.; Neusser, G.; Mizaikoff, B.


    Amorphous silica, composed of nanoscale spheres, is an important biomineral, alteration product of silicate rocks on the Earth's surface, and precursor material for stable silicate minerals. Despite constant progress in silica sphere synthesis, fundamental knowledge of natural silica particle interaction and ordering processes leading to colloidal crystals is absent so far. To understand the formation pathways of silica spheres in a geologic environment, we investigated silicified Cretaceous mollusk shell pseudomorphs from Coober Pedy (South Australia) using focused ion beam (FIB)-SEM tomography, petrographic microscopy, µ-XRD, and EMPA. The shells consist of replaced calcite crystals (product, the advancement of synchronized dissolution and precipitation fronts along lattice planes is essential. We assume that the volume-preserving replacement process proceeds via a face-specific dissolution-precipitation mechanism with intermediate subparticle aggregation and subsequent layer-by-layer deposition of spheres along a planar surface. Porosity created during the replacement reaction allows permanent fluid access to the propagating reaction interface. Fluid pH and ionic strength remain constant throughout the replacement process, permitting continuous silica nanoparticle formation and diffusion-limited colloid aggregation. Our study provides a natural example of the transformation of an atomic crystal to an amorphous, mesoscale ordered material; thus, links the research fields of natural colloidal crystal formation, carbonate-silica replacement, and crystallization by oriented particle aggregation (CPA).

  11. Microbiologically Induced Calcite Precipitation Mediated by Sporosarcina pasteurii. (United States)

    Bhaduri, Swayamdipta; Debnath, Nandini; Mitra, Sushanta; Liu, Yang; Kumar, Aloke


    The particular bacterium under investigation here (S. pasteurii) is unique in its ability, under the right conditions, to induce the hydrolysis of urea (ureolysis) in naturally occurring environments through secretion of an enzyme urease. This process of ureolysis, through a chain of chemical reactions, leads to the formation of calcium carbonate precipitates. This is known as Microbiologically Induced Calcite Precipitation (MICP). The proper culture protocols for MICP are detailed here. Finally, visualization experiments under different modes of microscopy were performed to understand various aspects of the precipitation process. Techniques like optical microscopy, Scanning Electron Microscopy (SEM) and X-Ray Photo-electron Spectroscopy (XPS) were employed to chemically characterize the end-product. Further, the ability of these precipitates to clog pores inside a natural porous medium was demonstrated through a qualitative experiment where sponge bars were used to mimic a pore-network with a range of length scales. A sponge bar dipped in the culture medium containing the bacterial cells hardens due to the clogging of its pores resulting from the continuous process of chemical precipitation. This hardened sponge bar exhibits superior strength when compared to a control sponge bar which becomes compressed and squeezed under the action of an applied external load, while the hardened bar is able to support the same weight with little deformation.

  12. Palm Vein Verification Using Gabor Filter

    Directory of Open Access Journals (Sweden)

    Ali Mohsin Al-Juboori


    Full Text Available Palm vein authentication is one of the modern biometric techniques, which employs the vein pattern in the human palm to verify the person. The merits of palm vein on classical biometric (e.g. fingerprint, iris, face are a low risk of falsification, difficulty of duplicated and stability. In this research, a new method is proposed for personal verification based on palm vein features. In the propose method, the palm vein images are firstly enhanced and then the features are extracted by using bank of Gabor filters. Then Fisher Discriminated Analysis (FDA is used to reduce the dimension of the features vectors. For vein pattern verification, this work uses Nearest Neighbors method. The EER of the proposed method is 0.2335%.

  13. Preduodenal portal vein: its surgical significance. (United States)

    Makey, D A; Bowen, J C


    Preduodenal portal vein is a rare anatomical variant which may be one of many anomalies in the neonate with duodenal "atresia." Preduodenal portal vein also may be an occasional finding in an adult undergoing biliary, gastric, or pancreatic surgery. Awareness and recognition of the anomaly are essential for the avoidance of injury during such operations. We report here a symptomless patient whose preduodenal portal vein was discovered at cholecystectomy.

  14. Small hepatic veins Budd-Chiari syndrome. (United States)

    Riggio, Oliviero; Marzano, Chiara; Papa, Alessia; Pasquale, Chiara; Gasperini, Maria Ludovica; Gigante, Antonietta; Valla, Dominique Charles; Plessier, Aurélie; Amoroso, Antonio


    Budd-Chiari syndrome is a rare disorder characterized by hepatic venous outflow obstruction at any level from the small hepatic veins to the atrio-caval junction, in the absence of heart failure or constrictive pericarditis. Various imaging modalities are available for investigating the gross hepatic vascular anatomy but there are rare forms of this disease where the obstruction is limited to the small intrahepatic veins, with normal appearance of the large hepatic veins at imaging. In this cases only a liver biopsy can demonstrate the presence of a small vessels outflow block. We report two cases of small hepatic veins Budd-Chiari syndrome.

  15. Leiomyosarcoma of the external iliac vein. (United States)

    Fukuda, Wakako; Taniguchi, Satoshi; Fukuda, Ikuo


    Leiomyosarcoma of the iliac vein is an uncommon tumor. We report a case of a 63-year-old Japanese woman with leiomyosarcoma of the right external iliac vein. The patient complained of right inguinal pain and swelling. Computed tomography demonstrated a mass surrounding the right external iliac artery and vein. Metastases in the lungs and liver were found. Complete resection of the tumor along with the involved vessels was performed. Polytetrafluoroethylene grafts were used to reconstruct the vessels. Pathological examination revealed leiomyosarcoma of the external iliac vein. Although the prognosis of leiomyosarcoma is poor, en bloc tumor resection is the treatment of choice.

  16. Sonographic Findings in Fetal Renal Vein Thrombosis. (United States)

    Gerber, Rebecca E; Bromley, Bryann; Benson, Carol B; Frates, Mary C


    We present the sonographic findings of fetal renal vein thrombosis in a series of 6 patients. The mean gestational age at diagnosis was 31.2 weeks. Four cases were unilateral, and 2 were bilateral. The most common findings were renal enlargement and intrarenal vascular calcifications, followed by increased renal parenchymal echogenicity. Inferior vena cava thrombosis was found in 4 patients and common iliac vein thrombosis in 2. Fetal renal vein thrombosis is an uncommon diagnosis with characteristic sonographic findings. The presence of these findings should prompt Doppler interrogation of the renal vein and inferior vena cava to confirm the diagnosis.

  17. Calcium sulfoaluminate (Ye'elimite) hydration in the presence of gypsum, calcite, and vaterite

    Energy Technology Data Exchange (ETDEWEB)

    Hargis, Craig W. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States); Telesca, Antonio [School of Engineering, University of Basilicata, Potenza (Italy); Monteiro, Paulo J.M., E-mail: [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States)


    Six calcium sulfoaluminate-based cementitious systems composed of calcium sulfoaluminate, calcite, vaterite, and gypsum were cured as pastes and mortars for 1, 7, 28 and 84 days. Pastes were analyzed with X-ray diffraction, thermogravimetric and differential thermal analyses. Mortars were tested for compressive strength, dimensional stability and setting time. Furthermore, pastes with a water/cementitious material mass ratio of 0.80 were tested for heat evolution during the first 48 h by means of isothermal conduction calorimetry. It has been found that: (1) both calcite and vaterite reacted with monosulfoaluminate to give monocarboaluminate and ettringite, with vaterite being more reactive; (2) gypsum lowered the reactivity of both carbonates; (3) expansion was reduced by calcite and vaterite, irrespective of the presence of gypsum; and (4) both carbonates increased compressive strength in the absence of gypsum and decreased compressive strength less in the presence of gypsum, with vaterite's action more effective than that of calcite.

  18. High School Forum: "Invitations to Enquiry": The Calcite/Acid Reaction. (United States)

    Herron, J. Dudley, Ed.; Driscoll, D. R.


    Describes a high school chemistry experiment which involves the reaction between calcite and hydrochloric and sulfuric acids. This reaction can be carried out as a projected demonstration and on an individual basis. (HM)

  19. Morphological changes of calcite single crystals induced by graphene-biomolecule adducts (United States)

    Calvaresi, Matteo; Di Giosia, Matteo; Ianiro, Alessandro; Valle, Francesco; Fermani, Simona; Polishchuk, Iryna; Pokroy, Boaz; Falini, Giuseppe


    Calcite has the capability to interact with a wide variety of molecules. This usually induces changes in shape and morphology of crystals. Here, this process was investigated using sheets of graphene-biomolecule adducts. They were prepared and made dispersible in water through the exfoliation of graphite by tip sonication in the presence tryptophan or N-acetyl-D-glucosamine. The crystallization of calcium carbonate in the presence of these additives was obtained by the vapor diffusion method and only calcite formed. The analysis of the microscopic observations showed that the graphene-biomolecule adducts affected shape and morphology of rhombohedral {10.4} faced calcite crystals, due to their stabilization of additional {hk.0} faces. The only presence of the biomolecule affected minimally shape and morphology of calcite crystals, highlighting the key role of the graphene sheets as 2D support for the adsorption of the biomolecules.

  20. Enhancing mechanical properties of calcite by Mg substitutions: An ab initio study (United States)

    Elstnerova, Pavlina; Friak, Martin; Hickel, Tilmann; Fabritius, Helge Otto; Lymperakis, Liverios; Petrov, Michal; Raabe, Dierk; Neugebauer, Joerg; Nikolov, Svetoslav; Zigler, Andreas; Hild, Sabine


    Arthropoda representing a majority of all known animal species are protected by an exoskeleton formed by their cuticle. The cuticle represents a hierarchically structured multifunctional bio-composite based on chitin and proteins. Some groups like Crustacea reinforce the load-bearing parts of their cuticle with calcite. As the calcite sometimes contains Mg it was speculated that Mg may have a stiffening impact on the mechanical properties of the cuticle. We present a theoretical parameter-free quantum-mechanical study of thermodynamic, structural and elastic properties of Mg-substituted calcite. Our results show that substituting Ca by Mg causes an almost linear decrease in the crystal volume with Mg concentration and of substituted crystals. As a consequence the calcite crystals become stiffer giving rise e.g. to substantially increased bulk moduli.

  1. phenoVein - A tool for leaf vein segmentation and analysis


    Bühler, J.; Rishmawi, L.; Pflugfelder, D.; Huber, G; Scharr, H.; Hülskamp, M; Koornneef, M.; Schurr, U; Jahnke, S.


    Precise measurements of leaf vein traits are an important aspect of plant phenotyping for ecological and genetic research. Here, we present a powerful and user-friendly image analysis tool named phenoVein. It is dedicated to automated segmenting and analyzing of leaf veins in images acquired with different imaging modalities (microscope, macrophotography, etc.), including options for comfortable manual correction. Advanced image filtering emphasizes veins from the background and compensates f...

  2. The mechanical and microstructural behaviour of calcite-dolomite composites: An experimental investigation


    Kushnir, Alexandra R. l.; Kennedy, L. A.; Misra, Santanu; Benson, Philip; White, J C


    The styles and mechanisms of deformation associated with many variably dolomitized limestone shear systems are strongly controlled by strain partitioning between dolomite and calcite. Here, we present experimental results from the deformation of four composite materials designed to address the role of dolomite on the strength of limestone. Composites were synthesized by hot isostatic pressing mixtures of dolomite (Dm) and calcite powders (% Dm: 25%-Dm, 35%-Dm, 51%-Dm, and 75%-Dm). In all comp...

  3. The coordination of sulfur in synthetic and biogenic Mg calcites: The red coral case (United States)

    Perrin, J.; Rivard, C.; Vielzeuf, D.; Laporte, D.; Fonquernie, C.; Ricolleau, A.; Cotte, M.; Floquet, N.


    Sulfur has been recognized in biogenic calcites for a long time. However, its structural position is matter of debate. For some authors, sulfur is a marker of the organic matrix while it is part of the calcite structure itself for others. To better understand the place of sulfur in calcite, sulfated magnesian calcites (S-MgCalcite) have been synthetized at high pressure and temperature and studied by μ-XANES spectroscopy. S-MgCalcite XANES spectra show two different types of sulfur: sulfate (SO42-) as a predominant species and a small contribution of sulfite (SO32-), both substituting for carbonate ions in the calcite structure. To address the question of the position of sulfur in biogenic calcites, the oxidation states of sulfur in the skeleton and organic tissues of Corallium rubrum have been investigated by micro X-ray fluorescence (μ-XRF) and sulfur K-edge micro X-ray absorption near edge structure (μ-XANES) spectroscopy at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) on beamline ID21. In the skeleton, sulfur is mainly present as oxidized sulfur SO42- (+VI), plus a weak sulfite contribution. XANES spectra indicate that sulfur is inorganically incorporated as sulfur structurally substituted to carbonate ions (SSS). Although an organic matrix is present in the red coral skeleton, reduced organic sulfur could not be detected by μ-XANES spectroscopy in the skeleton probably due to low organic/inorganic sulfur ratio. In the organic tissues surrounding the skeleton, several sulfur oxidation states have been detected including disulfide (S-S), thioether (R-S-CH3), sulfoxide (SO2), sulfonate (SO2O-) and sulfate (SO42-). The unexpected occurrence of inorganic sulfate within the organic tissues suggests the presence of pre-organized organic/inorganic complexes in the circulatory system of the red coral, precursors to biomineralization ahead of the growth front.

  4. Origin of sulfate in barite and calcite cements in the Jebel Madar salt dome (Oman) (United States)

    Vandeginste, V.; John, C. M.; Gilhooly, W. P.


    Jebel Madar is a 500-m high mountain rising in the desert at the Oman Foothills. The Jebel consists of Triassic to Cretaceous carbonate host rocks forming the carapace of a salt dome. Halokinesis caused major fracturing and faulting at Jebel Madar, and the resulting structures acted as the main pathways for fluids that generated diagenetic cements composed of both barite and calcite. The spatial distribution of calcite and barite occurrences shows that calcite is formed in large abundance along the three main faults, whereas barite is more concentrated along faults further away from the three main ones. The stable carbon and oxygen isotope composition of calcite and fluid inclusion data from both calcite and barite show a distinct evolution of the fluid with a highly saline component towards more mixing with meteoric water. This is in agreement with clumped isotopes data on calcite cements indicating an evolution towards lower temperatures, consistent with doming of the Jebel and greater input of lower-temperature descending meteoric fluids. Here, we present sulphur and oxygen isotopic data on barite that suggest a link between the barite formation and the Precambrian salt underlying Jebel Madar. The average δ34S measured in barite is 33‰ CDT (1σ = 5‰; n = 33), which falls at the lower end of the δ34S range reported for the Ara Group anhydrite. The average δ18O in the same barite samples is 23‰ VSMOW (1σ = 2‰; n = 33). Data from the barite will be compared with sulphur isotopes from the carbonate-associate sulfate in the calcite cements. The overall goal of our research is to gain a better insight in the formation process of barite and calcite in Jebel Madar and its link with salt tectonics. We would like to acknowledge the financial support of QCCSRC (funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park) and the GSA Laubach fund for this study.

  5. Molecular dynamics simulation of adsorption of an oil-water-surfactant mixture on calcite surface

    Institute of Scientific and Technical Information of China (English)

    Lu Guiwu; Zhang Xuefen; Shao Changjin; Yang Hong


    An interface super molecular structure model for oil-water-surfactant mixture and calcite was established. By using a molecular dynamics method, the effects of rhamnolipid, sodium dodecyl benzene sulfonate and sodium hexadecyl sulfonate on the interface adsorption behavior of oil molecules were investigated. It was found that these three surfactants could reduce oil-calcite interface binding energy, and play a role of oil-displacing agent.

  6. Accurate measurement of the main refractive indices and thermo-optical coefficients of the calcite crystal

    Institute of Scientific and Technical Information of China (English)

    Shuang Zhao; Fuquan Wu; Haifeng Wang; Weigang Zhong; Xiuzhen Li; Hengjing Tang; Meng Shi; Hongyan Deng


    The main refractive indices of calcite crystal are measured by the means of auto-collimation, and the thermo-optical coefficients are calculated. The coefficient expression of Sellmeier equation is obtained by solving Sellmeier equation strictly and the refractive indices of different wavelengths are calculated, which accord with experimental esultsery well. The measured main refractive indices of calcite at 488-nm wavelength are identical with the values obtained by Sellmeier equation.

  7. Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?

    Directory of Open Access Journals (Sweden)

    S. Bindschedler


    Full Text Available Calcitic nanofibres are ubiquitous habits of secondary calcium carbonate (CaCO3 accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enigmatic. Three possible mechanisms fuel the debate: (i purely physicochemical processes, (ii mineralization of rod-shaped bacteria, and (iii crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic or organic in nature. They are very often observed in association with Needle Fibre Calcite (NFC, another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent association is likely to be an important fact to help understanding the origin of nanofibres. In this manuscript the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothesis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morphological resemblance when compared to their natural counterparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hypothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically-influenced mineralization process, generating calcitic nanofibres. This highlights the possible involvement of Fungi in CaCO3 biomineralization processes, a role still poorly documented at

  8. Precipitation of Calcite during the Deposition of Paleogene Sangkarewang Oil Shale, Ombilin Basin, West Sumatra, Indonesia

    Directory of Open Access Journals (Sweden)

    Agus Haris Widayat


    Full Text Available DOI: 10.17014/ijog.2.3.185-197Geochemical and petrographical analyses were carried out to investigate the occurrence of calcite in theformer Ombilin lacustrine lake. The study involves eight samples taken from a 56 m long drill core of Sangkarewangoil shale. Geochemical investigation showed that the samples consist of varied terrigenous input represented by Si, Al, K, and Ti, and autochthonous input represented by S, total organic carbon (TOC, and d13C of bulk organic matter. Along the drill core profile the abundance of autochthonous input decreases upwards, while that of terrigenous input oppositely increases upwards. Petrographical analysis revealed that calcite is a major mineral in the samples. In this study, the abundance of calcite could be represented by the abundance of Ca, as calcite is the only significant Ca containing mineral. Ca is abundant in the samples (8.4% in average and its concentration varies similarly with those of S, TOC, and d13C, suggesting that the element as well as calcite incorporates the autochthonous input. Thevariation of calcite abundance in the drill core profile is considered to be related with primary productivity changes during the development of the former lake. Higher primary productivity represented by more positive of d13C value(-24.8‰ during the deposition of the lower part of the drill core profile promoted the higher amount of deposited organic matter. In such environment, the supersaturation of carbonate ion in lake water was also reached and significant precipitation of authigenic calcite occurred. As the lake developed, the primary productivity decreased as indicated by more negative of d13C value (eventually -26.8‰. This condition led to the decreases of deposited organic matterand calcite in the lake sediments.

  9. Sturgeon and paddlefish (Acipenseridae) sagittal otoliths are composed of the calcium carbonate polymorphs vaterite and calcite. (United States)

    Pracheil, B M; Chakoumakos, B C; Feygenson, M; Whitledge, G W; Koenigs, R P; Bruch, R M


    This study sought to resolve whether sturgeon (Acipenseridae) sagittae (otoliths) contain a non-vaterite fraction and to quantify how large a non-vaterite fraction is using neutron diffraction analysis. This study found that all otoliths examined had a calcite fraction that ranged from 18 ± 6 to 36 ± 3% by mass. This calcite fraction is most probably due to biological variation during otolith formation rather than an artefact of polymorph transformation during preparation.

  10. Subclavian artery to internal jugular vein fistula following percutaneous internal jugular vein catheterization. (United States)

    Merino-Angulo, J; Cortazar, J L; Saez-Garmendia, F; Montejo, M


    The percutaneous internal jugular vein approach is now a commonly performed procedure for central venous catheterization. Iatrogenic arteriovenous fistulae are a very infrequent complication. We report an asymptomatic subclavian artery to internal jugular vein fistula following two percutaneous internal jugular vein catheterization attempts.

  11. NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Bevilaqua, Rochele C. A.; Miranda, Caetano R. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Rigo, Vagner A. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Universidade Tecnológica Federal do Paraná, UTFPR, Cornélio Procópio, PR (Brazil); Veríssimo-Alves, Marcos [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Departamento de Física, ICEx, Universidade Federal Fluminense, UFF, Volta Redonda, RJ (Brazil)


    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca{sup 2+}. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO{sub 3} (101{sup ¯}4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for {sup 43}Ca, {sup 13}C, and {sup 17}O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

  12. Ion beam modifications of defect sub-structure of calcite cleavages

    Indian Academy of Sciences (India)

    E Venkateshwar Rao; M Ramakrishna Murthy


    Experimental investigations on the defect sub-structure and surface modifications, brought about by He+ ion-bombardment of calcite cleavages (100), have been carried out. Optical and scanning electron microscopic investigations revealed drastic modifications on the surface morphology, local symmetry and defect concentration. Additional structural defects on ion-bombardment of calcite surfaces also have been observed. Changes in shape and form of chemical etch pits are found to be a function of ion-beam energy, as studied by optical microscopy. Radiation damage in calcite has been attributed mainly due to desorption of CO$^{-2}_{3}$ ions from the calcite surfaces, on irradiation. Measurements of surface conductivity on irradiated calcite surfaces have been made employing a four-probe technique. Enhancement of surface conductivity has been considered to be due to an increase in concentration of CO$^{-2}_{3}$ ions formed, on ion irradiation and subsequent thermal stimulation. Planar plastic anisotropy has been studied on irradiated calcite cleavages by measurement of microhardness.

  13. Reaction-induced fracturing in a hot pressed calcite-periclase aggregate (United States)

    Kuleci, H.; Ulven, O. I.; Rybacki, E.; Wunder, B.; Abart, R.


    The chemo-mechanical feedbacks associated with hydration of periclase immersed in a calcite matrix were investigated experimentally. Dense calcite-periclase aggregates with calcite to periclase ratio of 90/10 and 95/5 by volume were prepared by hot isostatic pressing. Subsequent hydration experiments were performed in a hydrothermal apparatus at temperatures of 580-610 °C and a pressure of 200 MPa for run durations of 5-60 min. The rate of the periclase to brucite transformation was primarily controlled by the access of fluid. Where fluid was present, the reaction was too fast for the associated positive volume increase of the solids of about 100% to be accommodated by creep of the calcite matrix, and fracturing was induced. The newly formed cracks greatly enhanced the access of fluid leading to a positive feedback between hydration and fracturing. Mostly the newly formed cracks follow pre-existing grain boundaries in the calcite matrix. Comparison of experimental results with numerical 2D discrete element modelling (DEM) of crack formation revealed that the geometry of the crack pattern around a reacting particle depends on the shape of the original periclase particle, on the mechanical strength of the particle-matrix interface and on the mechanical strength and arrangement of grain boundaries in the calcite matrix in the immediate vicinity of the swelling particle.

  14. The calcite → aragonite transformation in low-Mg marble: Equilibrium relations, transformations mechanisms, and rates (United States)

    Hacker, Bradley R.; Rubie, David C.; Kirby, Stephen H.; Bohlen, Steven R.


    Experimental transformation of a rather pure natural calcite marble to aragonite marble did not proceed via the expected straightforward polymorphic replacement. Instead, the small amount of Mg in the starting material (0.36 wt %) was excluded from the growing aragonite and diffused preferentially into the remaining calcite grains, producing Mg-rich calcite rods that persisted as relicts. Nucleation of aragonite occurred exclusively on grain boundaries, with aragonite [001] oriented subparallel to calcite [0001]. The aragonite crystals preferentially consumed the calcite crystal on which they nucleated, and the reaction fronts developed preferentially along the {010} and {110} planes of aragonite. Each aragonite neoblast that grew was nearly free of Mg (typically growth rates are approximately linear and range from ∼3 × 10−11 m s−1 at 600°C to ∼9 × 10−9 m s−1 at 850°C, with an apparent activation enthalpy of 166 ± 91 kJ mol−1. This reaction mechanism and the resultant texture are akin to cellular precipitation reactions in metals. Similar transformation textures have been reported from high-Mg marbles in Japan and China that disproportionated to low-Mg calcite and dolomite.

  15. Low-Temperature Plasticity of Naturally Deformed Calcite Rocks

    Institute of Scientific and Technical Information of China (English)


    Optical, cathodoluminescence and transmission electron microscope (TEM) analyses were conducted onfour groups of calcite fault rocks, a cataclastic limestone, cataclastic coarse-grained marbles from two fault zones, and afractured mylonite. These fault rocks show similar microstructural characteristics and give clues to similar processes ofrock deformation. They are characterized by the structural contrast between macroscopic cataclastic (brittle) andmicroscopic mylonitic (ductile) microstructures. Intragranular deformation microstructures (i.e. deformation twins, kinkbands and microfractures) are well preserved in the deformed grains in clasts or in primary rocks. The matrix materials areof extremely fine grains with diffusive features. Dislocation microstructures for co-existing brittle deformation andcrystalline plasticity were revealed using TEM. Tangled dislocations are often preserved at the cores of highly deformedclasts, while dislocation walls form in the transitions to the fine-grained matrix materials and free dislocations, dislocationloops and dislocation dipoles are observed both in the deformed clasts and in the fine-grained matrix materials. Dynamicrecrystallization grains from subgrain rotation recrystallization and subsequent grain boundary migration constitute themajor parts of the matrix materials. Statistical measurements of densities of free dislocations, grain sizes of subgrains anddynamically recrystallized grains suggest an unsteady state of the rock deformation. Microstructural andcathodoluminescence analyses prove that fluid activity is one of the major parts of faulting processes. Low-temperatureplasticity, and thereby induced co-existence of macroscopic brittle and microscopic ductile microstmctures are attributedto hydrolytic weakening due to the involvement of fluid phases in deformation and subsequent variation of rock rheology.During hydrolytic weakening, fluid phases, e.g. water, enhance the rate of dislocation slip and climb, and

  16. Generating and analyzing synthetic finger vein images

    NARCIS (Netherlands)

    Hillerström, Fieke; Kumar, Ajay; Veldhuis, Raymond


    Abstract: The finger-vein biometric offers higher degree of security, personal privacy and strong anti-spoofing capabilities than most other biometric modalities employed today. Emerging privacy concerns with the database acquisition and lack of availability of large scale finger-vein database have


    Directory of Open Access Journals (Sweden)

    Trajkovska Meri


    Full Text Available Portal venous system, apart from the main portal vein, includes its tributaries: superior and inferior mesenteric vein, as well as splenic vein, so the term portal venous thrombosis encompasses a broad spectrum of pathological conditions. Usually, one or more causative factors can be recognized, either local endothelial/ flow disturbances, or systemic inherited /acquired conditions. Portal vein thrombosis can be associated with benign or malignant disorders. Weather we are speaking about acute or chronic thrombosis, the clinical presentation is different. Acute thrombosis can be presented in a wide range, from mild abdominal discomfort to a state of intestinal ischemia and life-threatening infarction. Chronic thrombosis is usually recognized when variceal bleeding or other symptoms of portal hypertension express. Fast and accurate diagnosis sometimes is a life-saving procedure, especially in acute vascular alterations. Recently, due to the improvement of imaging procedures the number of patients with diagnosed portal vein thrombosis is increasingly growing. With a negative predictive value of 98% color Doppler ultrasound is considered as imaging modality of choice in detecting portal vein thrombosis. Based on large studies it is presumed that overall risk of getting portal vein thrombosis during lifetime is 1% in general population, but much bigger 5%-15% in cirrhotic patients. Existence of specific ultrasound criteria, if fulfilled, has ensured that diagnosis of portal vein thrombosis is fast and non-invasive. Procedure is convenient for the patient and healthcare providers, and above all, allows prompt treatment preventing further deterioration.

  18. Endovenous laser therapy for varicose veins

    NARCIS (Netherlands)

    Disselhoff, B.C.V.M.


    This thesis describes the technique of endovenous laser ablation and the outcome of various series of patients with varicose veins due to reflux in the great saphenous vein, treated by endovenous laser ablation or cryostripping in a single-centre study. This study has shown clear advantages of endov

  19. Vein of foramen caecum: imaging findings. (United States)

    Tutar, Onur; Kandemirli, Sedat Giray; Yildirim, Duzgun; Memis, Emine Sebnem; Bakan, Selim


    Vein of foramen caecum has been classically described as a vein that connects nasal mucosa to the superior sagittal sinus in classic anatomy textbooks. However, its existence is controversial in literature. Herein, we demonstrated computed tomography and contrast enhanced magnetic resonance imaging findings of a tubular vascular structure extending to nasal mucosa and superior sagittal sinus.

  20. Improving the management of varicose veins. (United States)

    Onida, Sarah; Lane, Tristan R A; Davies, Alun H


    Up to 30% of the UK population are affected by varicose veins. They are a manifestation of increased venous pressure in the lower limb caused by impaired venous return. Primary varicosities result from poor drainage from the superficial to the deep venous system. Secondary varicosities arise as a result of underlying pathology impeding venous drainage, such as deep venous thrombosis or increased intra-abdominal pressure caused by a mass, pregnancy or obesity. Patients with bleeding varicose veins should be referred to a vascular service immediately. Referral is also indicated in the following cases: symptomatic primary or recurrent varicose veins; lower limb skin changes thought to be caused by chronic venous insufficiency; superficial vein thrombosis and suspected venous incompetence; a venous leg ulcer or healed venous leg ulcer. Imaging is crucial in the assessment of the superficial and deep venous system to enable assessment of venous competence. The gold standard imaging technique is colour duplex ultrasonography. Duplex ultrasound should be used to confirm the diagnosis of varicose veins and the extent of truncal reflux, and to plan treatment for patients with suspected primary or recurrent varicose veins. Superficial vein ligation, phlebectomy and stripping have been the mainstay of treatment. In recent years, new techniques have been developed that are minimally invasive, enabling treatment of superficial venous incompetence with reduced morbidity. NICE recommends that endothermal ablation, in the form of radiofrequency or laser treatment, should be offered as treatment for patients with confirmed varicose veins and truncal reflux.

  1. Retinal vein occlusion: pathophysiology and treatment options


    Niral Karia


    Niral KariaDepartment of Ophthalmology, Southend Hospital, Prittlewell Chase, Westcliff on Sea, Essex, United KingdomAbstract: This paper reviews the current thinking about retinal vein occlusion. It gives an overview of its pathophysiology and discusses the evidence behind the various established and emerging treatment paradigms.Keywords: central, hemispheric, branch, retinal vein occlusion, visual loss

  2. Assessment and management of patients with varicose veins. (United States)

    Allen, Louise

    Varicose veins are enlarged superficial veins found in the legs. This article explores the anatomy and physiology of the venous system to assist nurses to assess, manage and treat patients with varicose veins.

  3. Ages and Origins of Calcite and Opal in the Exploratory Studies Facility Tunnel, Yucca Mountain, Nevada (United States)

    Paces, James B.; Neymark, Leonid A.; Marshall, Brian D.; Whelan, Joseph F.; Peterman, Zell E.


    Deposits of calcite and opal are present as coatings on open fractures and lithophysal cavities in unsaturated-zone tuffs at Yucca Mountain, Nevada, site of a potential high-level radioactive waste repository. Outermost layers of calcite and opal have radiocarbon ages of 16,000 to 44,000 years before present and thorium-230/uranium ages of 28,000 to more than 500,000 years before present. These ages are young relative to the 13-million-year age of the host rocks. Multiple subsamples from the same outer layer typically show a range of ages with youngest ages from the thinnest subsamples. Initial uranium-234/uranium-238 activity ratios between 1 and 9.5 show a distinct negative correlation with thorium-230/uranium age and are greater than 4 for all but one sample younger than 100,000 years before present. These data, along with micrometer-scale layering and distinctive crystal morphologies, are interpreted to indicate that deposits formed very slowly from water films migrating through open cavities. Exchanges of carbon dioxide and water vapor probably took place between downward-migrating liquids and upward-migrating gases at low rates, resulting in oversaturation of mineral constituents at crystal extremities and more or less continuous deposition of very thin layers. Therefore, subsamples represent mixtures of older and younger layers on a scale finer than sampling techniques can resolve. Slow, long-term rates of deposition (less than about 5 millimeters of mineral per million years) are inferred from subsamples of outermost calcite and opal. These growth rates are similar to those calculated assuming that total coating thicknesses of 10 to 40 millimeters accumulated over 12 million years. Calcite has a wide range of delta carbon-13 values from about -8.2 to 8.5 per mil and delta oxygen-18 values from about 10 to 21 per mil. Systematic microsampling across individual mineral coatings indicates basal (older) calcite tends to have the largest delta carbon-13 values

  4. Thermal and Evolved Gas Behavior of Calcite Under Mars Phoenix TEGA Operating Conditions (United States)

    Ming, D.W.; Niles, P.B.; Morris, R.V.; Boynton, W.V.; Golden, D.C.; Lauer, H.V.; Sutter, B.


    The Mars Phoenix Scout Mission with its diverse instrument suite successfully examined several soils on the Northern plains of Mars. The Thermal and Evolved Gas Analyzer (TEGA) was employed to detect organic and inorganic materials by coupling a differential scanning calorimeter (DSC) with a magnetic-sector mass spectrometer (MS). Martian soil was heated up to 1000 C in the DSC ovens and evolved gases from mineral decomposition products were examined with the MS. TEGA s DSC has the capability to detect endothermic and exothermic reactions during heating that are characteristic of minerals present in the Martian soil. Initial TEGA results indicated the presence of endothermic peaks with onset temperatures that ranged from 675 C to 750 C with corresponding CO2 release. This result suggests the presence of calcite (CaCO3. CaO + CO2). Organic combustion to CO2 is not likely since this mostly occurs at temperatures below 550 C. Fe-carbonate and Mg-carbonate are not likely because their decomposition temperatures are less than 600 C. TEGA enthalpy determinations suggest that calcite, may occur in the Martian soil in concentrations of approx.1 to 5 wt. %. The detection of calcite could be questioned based on previous results that suggest Mars soils are mostly acidic. However, the Phoenix landing site soil pH was measured at pH 8.3 0.5, which is typical of terrestrial soils where pH is controlled by calcite solubility. The range of onset temperatures and calcite concentration as calculated by TEGA is poorly con-strained in part because of limited thermal data of cal-cite at reduced pressures. TEGA operates at calcite literature thermal data was obtained at 1000 mbar or higher pressures.

  5. Effect of Mg on the Grain Growth and Dislocation Creep of Calcite (United States)

    Xu, L.


    We tested the effect of variations in the amount of the solute impurity (Mg) on grain growth and strength of calcite aggregate. Synthetic marbles were produced by hot isostatic pressing mixtures of powders of calcite and dolomite at 850° C and 300 MPa confining pressure for different intervals (2 to 30 hrs). The HIP treatment resulted in homogeneous aggregates of calcite with Mg content from 0.5 to 17 mol%. Stress stepping tests and constant strain rate tests were used to examine the effect of Mg content on the dislocation creep of calcite. The grain growth rate under static conditions was decreased with Mg content from 7 to 17 mol%, indicating perhaps that grain boundary mobility is suppressed by the solute drag effect. In the diffusion creep at stresses below 40 Mpa, the strength of calcite decreases with increasing Mg content owing to the difference in grain size at 800° C and 300 MPa confining pressure. The contribution of dislocation creep increases with increasing stress, and the transition between diffusion and dislocation creep occurs at higher stresses for the samples with higher magnesium content and smaller grain size. The creep data were fit assuming a composite flow law consisting of a linear combination of diffusion and dislocation creep and a single-valued grain size. The best agreement was obtained by using a dislocation creep law with exponential dependence of strain rate on stress (e.g. Peierls law). More evidence from microstructure is needed to identify the dominant deformation mechanism conclusively. Most of the samples were compressed up to strains of 0.25; small recrystallized grains are formed resulting in a bimodal grain size distribution in some of the deformed samples. Preliminary data shows that the recrystallized grain sizes are smaller for Mg-calcite compared with that of pure calcite. This study will help to understand the effect of impurities on grain-growth kinetics and strain weakening in localized shear zones.

  6. The influence of final repository relevant electrolyte on the interaction of trivalent lanthanides and actinides with calcite; Der Einfluss endlagerrelevanter Elektrolyte auf die Wechselwirkung dreiwertiger Lanthanide und Actinide mit Calcit

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Sascha


    Calcite, a naturally occurring and very abundant mineral, is considered a potential retentive geochemical barrier regarding nuclear waste disposal. In this work, the reactivity of calcite towards trivalent Ln and An has been determined by spectroscopic, microscopic and X-ray scattering techniques. This, in connection with the use of luminescent probes Eu(III) and Cm(III), allowed for the understanding of electrolyte influences on the retention potential of calcite.

  7. Radiological features of azygous vein aneurysm. (United States)

    Choudhary, Arabinda Kumar; Moore, Michael


    Mediastinal masses are most commonly associated with malignancy. Azygous vein aneurysm is a very rare differential diagnosis of mediastinal mass. We report here three cases of azygous vein aneurysm including children and adult patients. In the pediatric patient it was further complicated by thrombosis and secondary pulmonary embolism. We describe the radiological features on CXR, MRI, CT, PET-CT, US and angiogram and their differential diagnosis. Imaging findings of continuity with azygous vein, layering of contrast medium on enhanced CT and dynamic MRA showing filling of the mass at the same time as the azygous vein without prior enhancement will be strongly suggestive of azygous vein aneurysm with transtracheal ultrasound being the definitive test in these patients. It is important to keep a vascular origin mass in the differential diagnosis of mediastinal masses. Also, in young healthy patients with pulmonary embolism, a vascular etiology such as azygous vein aneurysm should be carefully evaluated. This article will help the clinicians to learn about the imaging features of azygous vein aneurysm on different imaging modalities.

  8. Portal vein gas in emergency surgery

    Directory of Open Access Journals (Sweden)

    Mahmood Hind


    Full Text Available Abstract Background Portal vein gas is an ominous radiological sign, which indicates a serious gastrointestinal problem in the majority of patients. Many causes have been identified and the most important was bowel ischemia and mesenteric vascular accident. The presentation of patients is varied and the diagnosis of the underlying problem depends mainly on the radiological findings and clinical signs. The aim of this article is to show the clinical importance of portal vein gas and its management in emergency surgery. Methods A computerised search was made of the Medline for publications discussing portal vein gas through March 2008. Sixty articles were identified and selected for this review because of their relevance. These articles cover a period from 1975–2008. Results Two hundreds and seventy-five patients with gas in the portal venous system were reported. The commonest cause for portal vein gas was bowel ischemia and mesenteric vascular pathology (61.44%. This was followed by inflammation of the gastrointestinal tract (16.26%, obstruction and dilatation (9.03%, sepsis (6.6%, iatrogenic injury and trauma (3.01% and cancer (1.8%. Idiopathic portal vein gas was also reported (1.8%. Conclusion Portal vein gas is a diagnostic sign, which indicates a serious intra-abdominal pathology requiring emergency surgery in the majority of patients. Portal vein gas due to simple and benign cause can be treated conservatively. Correlation between clinical and diagnostic findings is important to set the management plan.

  9. Valsalva and gravitational variability of the internal jugular vein and common femoral vein: Ultrasound assessment

    Energy Technology Data Exchange (ETDEWEB)

    Beddy, P. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland)]. E-mail:; Geoghegan, T. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland); Ramesh, N. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland); Buckley, O. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland); O' Brien, J. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland); Colville, J. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland); Torreggiani, W.C. [Department of Radiology, The Adelaide and Meath Hospital, Tallaght, Dublin 24 (Ireland)


    Purpose: Central venous cannulation via the common femoral vein is an important starting point for many interventions. The purpose of this study was to determine the optimum conditions for cannulation of the femoral vein and to compare these with the relative changes in the internal jugular vein. Methods: High-resolution 2D ultrasound was utilised to determine variability of the calibre of the femoral and internal jugular veins in 10 healthy subjects. Venous diameter was assessed during the Valsalva manoeuvre and in different degrees of the Trendelenburg position. Results: The Valsalva manoeuvre significantly increased the size of the femoral and internal jugular veins. There was a relatively greater increase in femoral vein diameter when compared with the internal jugular vein of 40 and 29%, respectively. Changes in body inclination (Trendelenburg position) did not significantly alter the luminal diameter of the femoral vein. However, it significantly increased internal jugular vein diameter. Conclusions: Femoral vein cannulation is augmented by the Valsalva manoeuvre but not significantly altered by the gravitational position of the subject.

  10. The puzzling presence of calcite in skeletons of modern solitary corals from the Mediterranean Sea (United States)

    Goffredo, Stefano; Caroselli, Erik; Mezzo, Francesco; Laiolo, Leonardo; Vergni, Patrizia; Pasquini, Luca; Levy, Oren; Zaccanti, Francesco; Tribollet, Aline; Dubinsky, Zvy; Falini, Giuseppe


    The skeleton of scleractinian corals is commonly believed to be composed entirely of aragonite due to the current Mg/Ca molar ratio of seawater, which thermodynamically favours the deposition of this polymorph of calcium carbonate (CaCO3). However, some studies have shown that other forms of CaCO3 such as calcite can be present in significant amount (1-20%) inside tropical coral skeletons, significantly impacting paleo-reconstructions of SST or other environmental parameters based on geochemical proxies. This study aims at investigating for the first time, (1) the skeletal composition of two Mediterranean solitary corals, the azooxanthellate Leptopsammia pruvoti and the zooxanthellate Balanophyllia europaea, across their life cycle, (2) the distribution of the different CaCO3 forms inside skeletons, and (3) their implications in paleoclimatology. The origin of the different forms of CaCO3 observed inside studied coral skeletons and their relationships with the species' habitat and ecological strategies are also discussed. CaCO3 composition of L. pruvoti and B. europaea was investigated at six sites located along the Italian coasts. Skeleton composition was studied by means of X-ray powder diffraction and Fourier transform infrared spectroscopy. A significant amount of calcite (1-23%) was found in more than 90% of the studied coral skeletons, in addition to aragonite. This calcite was preferentially located in the basal and intermediate areas than at the oral pole of coral skeletons. Calcite was also mainly located in the epitheca that covered the exposed parts of the coral in its aboral region. Interestingly in B. europaea, the calcite content was negatively correlated with skeleton size (age). The presence of calcite in scleractinian corals may result from different mechanisms: (1) corals may biologically precipitate calcite crystals at their early stages in order to insure their settlement on the substrate of fixation, especially in surgy environments; (2

  11. Hand vein recognition based on orientation of LBP (United States)

    Bu, Wei; Wu, Xiangqian; Gao, Enying


    Vein recognition is becoming an effective method for personal recognition. Vein patterns lie under the skin surface of human body, and hence provide higher reliability than other biometric traits and hard to be damaged or faked. This paper proposes a novel vein feature representation method call orientation of local binary pattern (OLBP) which is an extension of local binary pattern (LBP). OLBP can represent the orientation information of the vein pixel which is an important characteristic of vein patterns. Moreover, the OLBP can also indicate on which side of the vein centerline the pixel locates. The OLBP feature maps are encoded by 4-bit binary values and an orientation distance is developed for efficient feature matching. Based on OLBP feature representation, we construct a hand vein recognition system employing multiple hand vein patterns include palm vein, dorsal vein, and three finger veins (index, middle, and ring finger). The experimental results on a large database demonstrate the effectiveness of the proposed approach.

  12. Phosphorus speciation in calcite speleothems determined from solid-state NMR spectroscopy (United States)

    Mason, Harris E.; Frisia, Silvia; Tang, Yuanzhi; Reeder, Richard J.; Phillips, Brian L.


    Variations in speleothem P concentration show cyclic patterns that have important implications for high resolution palaeoclimate and palaeoenvironmental reconstructions. However, little is known about the speciation of P in calcite speleothems. Here we employ solid-state 31P and 1H magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopic techniques as a non-destructive method for analyzing the distribution of P in speleothems. The 31P MAS NMR results show three peaks indicating the presence of three primary types of phosphate species in samples from the Grotta di Ernesto (northeastern Italy): a broad peak at a chemical shift δP-31 = 3.1 to 3.7 ppm from individual phosphate ions incorporated within calcite, a narrow set of peaks near δP-31 = - 0.9 ppm from crystalline monetite and a narrow peak at δP-31 = 2.9 ppm from an unidentified crystalline phosphate phase. Essentially identical results were obtained for a synthetic calcite/phosphate coprecipitate. Spectra collected for a sample from Grotte de Clamouse (southern France) show only a broad peak near 3.5 ppm suggesting a possible limit for phosphate incorporation into the calcite structure. These data suggest that P in this system can interact to form calcium phosphate surface precipitates during infiltration events and are subsequently enclosed during calcite growth.

  13. Model study of initial adsorption of SO{sub 2} on calcite and dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Malaga-Starzec, Katarina; Panas, Itai; Lindqvist, Oliver


    The rate of calcareous stone degradation is to a significant extent controlled by their surface chemistry with SO{sub 2}. Initial surface sulphite is converted to a harmful gypsum upon, e.g. NO{sub 2} catalysed oxidation. However, it has been observed by scanning electron microscopy that the lateral distributions of gypsum crystals differ between calcitic and dolomitic marbles. The first-principles density functional theory is employed to understand the origin of these fundamentally different morphologies. Here, the stability differences of surface sulphite at calcite CaCO{sub 3} (s) and dolomite Ca{sub x}Mg{sub 1-x}CO{sub 3} (s) are determined. A qualitative difference in surface sulphite stability, favouring the former, is reported. This is taken to imply that calcitic micro-crystals embedded in a dolomitic matrix act as sinks in the surface sulphation process, controlled by SO{sub 2} diffusion. The subsequent formation of gypsum under such conditions will not require SO{sub 4}{sup 2-} (aq) ion transport. This explains the homogeneous distribution of gypsum observed on the calcitic micro-crystals in dolomite. In contrast, sulphation on purely calcitic marbles never reaches such high SO{sub 2} coverage. Rather, upon oxidation, SO{sub 4}{sup 2-} (aq) transport to nucleation centres, such as grain boundaries, is required for the growth of gypsum crystals.

  14. Mechanism of Calcite Co-Orientation in the Sea Urchin Tooth

    Energy Technology Data Exchange (ETDEWEB)

    Killian, Christopher; Metzler, Rebecca; Gong, Y. U. T.; Olson, Ian; Aizenberg, Joanna; Politi, Yael; Wilt, Fred; Scholl, Andreas; Young, Anthony; Doran, Andrew; Kunz, Martin; Tamura, Nobumichi; Coppersmith, Susan; Gilbert, P. U. P. A.


    Sea urchin teeth are remarkable and complex calcite structures, continuously growing at the forming end and self-sharpening at the mature grinding tip. The calcite (CaCO{sub 3}) crystals of tooth components, plates, fibers, and a high-Mg polycrystalline matrix, have highly co-oriented crystallographic axes. This ability to co-orient calcite in a mineralized structure is shared by all echinoderms. However, the physico-chemical mechanism by which calcite crystals become co-oriented in echinoderms remains enigmatic. Here, we show differences in calcite c-axis orientations in the tooth of the purple sea urchin (Strongylocentrotus purpuratus), using high-resolution X-ray photoelectron emission spectromicroscopy (X-PEEM) and microbeam X-ray diffraction ({mu}XRD). All plates share one crystal orientation, propagated through pillar bridges, while fibers and polycrystalline matrix share another orientation. Furthermore, in the forming end of the tooth, we observe that CaCO{sub 3} is present as amorphous calcium carbonate (ACC). We demonstrate that co-orientation of the nanoparticles in the polycrystalline matrix occurs via solid-state secondary nucleation, propagating out from the previously formed fibers and plates, into the amorphous precursor nanoparticles. Because amorphous precursors were observed in diverse biominerals, solid-state secondary nucleation is likely to be a general mechanism for the co-orientation of biomineral components in organisms from different phyla.

  15. Dolomite-magnesian calcite relations at elevated temperatures and CO2 pressures (United States)

    Graf, D.L.; Goldsmith, J.R.


    The equilibrium thermal decomposition curve of dolomite has been determined up to a CO2 pressure of 20,000 lb/in.2, at which pressure dolomite decomposes at 857??C. Equilibrium was approached from both directions, by the breakdown and by the solid-state synthesis of dolomite. At elevated temperatures and pressures, calcites in equilibrium with periclase as well as those in equilibrium with dolomite contain Mg in solid solution. In the former, the Mg content increases with increasing CO2 pressure, and decreases with increasing temperature. In the latter, it is a function of temperature only. The exsolution curve of dolomite and magnesian calcite has been determined between 500?? and 800??C; at 500?? dolomite is in equilibrium with a magnesian calcite containing ~6 mol per cent MgCO2; at 800??, ~22 mol per cent. There appears to be a small but real deviation from the ideal 1 : 1 Ca : Mg ratio of dolomite, in the direction of excess Ca, for material in equilibrium with magnesian calcite at high temperature. The experimental findings indicate that very little Mg is stable in the calcites of sedimentary environments, but that an appreciable amount is stable under higher-temperature metamorphic conditions, if sufficient CO2 pressure is maintained. ?? 1955.

  16. Selective Separation of Fluorite, Barite and Calcite with Valonea Extract and Sodium Fluosilicate as Depressants

    Directory of Open Access Journals (Sweden)

    Zijie Ren


    Full Text Available Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with sodium oleate as the collector. The single mineral flotation results showed that valonea extract displayed the strongest depression on calcite, while sodium fluosilicate displayed the strongest depression on barite. These two depressants allowed selective separation of the three minerals through sequential flotation. The flotation of mixed minerals showed that 94% of the calcite was successfully depressed by the valonea extract, and 95% recovery of the fluorite was achieved in the subsequent flotation with sodium fluosilicate depressing barite. The different depressant–mineral interactions were investigated via electro-kinetic studies and molecular dynamics (MD simulations using the Materials Studio 6.0 program. The valonea extract exhibited the strongest adsorption on the calcite surface, and sodium fluosilicate exhibited the strongest adsorption on the barite surface, which prevented oleate species from reacting with Ca2+ or Ba2+ surface sites. This study provides useful guidance for how to process fluorite, barite and calcite resources.

  17. The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite. (United States)

    Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Benning, Liane G


    The kinetics and mechanisms of nanoparticulate amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range of environmentally relevant temperatures (7.5-25 °C) using synchrotron-based in situ time-resolved Energy Dispersive X-ray Diffraction (ED-XRD) in conjunction with high-resolution electron microscopy, ex situ X-ray diffraction and infrared spectroscopy. The crystallization process occurs in two stages; firstly, the particles of ACC rapidly dehydrate and crystallize to form individual particles of vaterite; secondly, the vaterite transforms to calcite via a dissolution and reprecipitation mechanism with the reaction rate controlled by the surface area of calcite. The second stage of the reaction is approximately 10 times slower than the first. Activation energies of calcite nucleation and crystallization are 73±10 and 66±2 kJ mol(-1), respectively. A model to calculate the degree of calcite crystallization from ACC at environmentally relevant temperatures (7.5-40 °C) is also presented.

  18. Trace concentration - Huge impact: Nitrate in the calcite/Eu(III) system (United States)

    Hofmann, Sascha; Voïtchovsky, Kislon; Schmidt, Moritz; Stumpf, Thorsten


    The interactions of trivalent lanthanides and actinides with secondary mineral phases such as calcite is of high importance for the safety assessment of deep geological repositories for high level nuclear waste (HLW). Due to similar ionic radii, calcium-bearing mineral phases are suitable host minerals for Ln(III) and An(III) ions. Especially calcite has been proven to retain these metal ions effectively by both surface complexation and bulk incorporation. Since anionic ligands (e.g., nitrate) are omnipresent in the geological environment and due to their coordinating properties, their influence on retentive processes should not be underestimated. Nitrate is a common contaminant in most HLW forms as a result of using nitric acid in fuel reprocessing. It is also formed by microbial activity under aerobic conditions. In this study, atomic force microscopy investigations revealed a major influence of nitrate upon the surface of calcite crystals. NaNO3 causes serious modifications even in trace amounts (surface layer of low crystallinity on top of the calcite crystal. Time-resolved laser fluorescence spectroscopy of Eu(III) showed that, within this layer, Eu(III) ions are incorporated, while losing most of their hydration shell. The results show that solid solution modelling for actinides in calcite must take into account the presence of nitrate in pore and ground waters.

  19. Authigenic Mg-calcite at a cold methane seep site in the Laptev Sea (United States)

    Kravchishina, M. D.; Lein, A. Yu.; Savvichev, A. S.; Reykhard, L. E.; Dara, O. M.; Flint, M. V.


    Authigenic minerals were studied in Holocene shelf sediments of the Laptev Sea (cold methane seep site, water depth 71 m). The study presents the first finds of large hard carbonate concretions with Mg-calcite cement in recent sediments of the Arctic shelf seas. These concretions differ from previously reported glendonites and concretions from bottom sediments of the White Sea, Kara Sea, Sea of Okhotsk, etc. A study of the morphology, microstructure, and composition of these newly reported concretions revealed the multistage formation of carbonates (structural varieties of Mg-calcite and aragonite). It was shown that organic matter played an important role in the formation of authigenic carbonates, i.e., in the formation of sedimentary-diagenetic Mg-calcite. The role of methane as a possible source for authigenic carbonate formation was estimated. It was found that methane-derived Mg-calcite accounts for 17-35% of concretion materials. Mg-calcite had δ13C-Ccarb values between-24 and-23‰ and δ13C-Corg values between-44.5 and-88.5‰.

  20. Petrography, mineralogy, and chemistry of calcite-silica deposits at Exile Hill, Nevada, compared with local spring deposits

    Energy Technology Data Exchange (ETDEWEB)

    Vaniman, D.T.; Chipera, S.J.; Bish, D.L.


    Chemical, mineralogic, and petrographic analyses of siliceous calcretes from Exile Hill east of Yucca Mountain, Nevada, indicate that pedogenic processes alone account for the formation of the calcretes. These calcretes have been interpreted by some observers as evidence of seismically triggered eruptions of deep water. Such an origin could have important consequences if Yucca Mountain is developed as an unsaturated site for the disposal of high-level nuclear waste. At odds with this hypothesis are the absence of features that should be present at fault-fed springs (e.g., fissure-ridge mounds with microterraces) and the preservation within root casts of delicate pedogenic microfossils, such as calcified filaments and needle-fiber calcites. Mineral-chemical evidence of pedogenic origin is found in heavy-mineral concentrations, reflected in Fe and Sc enrichments. These concentrations, which occur in the most massive of the vein calcretes, require derivation of detritus from a mixture of weathered and eolian materials that occur in the overlying B soil horizons, as opposed to direct incorporation of adjacent unweathered bedrock. Carbonate and silica abundances and accumulation rates are well within the scope of pedogenic processes. Calcium is derived from rainwater or eolian sources, whereas silica is derived in part by dissolution of local volcanic glasses or from dissolution of unstable silica minerals that are abundant in the local tuffs. In contrast with local deposits that are of spring or seep origin, the siliceous calcretes at Yucca Mountain are pedogenic in origin as well as evolution and provide no evidence in support of conjectured spring activity.

  1. Ventriculoatrial shunting via the azygos vein. (United States)

    Balasubramaniam, C; DuBois, J J; Laurent, J P; Pokorny, W J; Harberg, F J; Cheek, W R


    The treatment of hydrocephalus has evolved through many stages but the "cure" is still elusive. It is not unusual for the neurosurgeon to find that the commonly used routes for catheter placement or sites for drainage of cerebrospinal fluid (CSF) cannot be employed. The azygos vein was used to gain access to the right atrium when the CSF could not be drained into the peritoneal cavity, nor could the neck veins be used to place the catheter into the right atrium. The azygos vein is a convenient and safe route to reach the right atrium in selected patients.

  2. Portal Decompression Using the Inferior Mesenteric Vein

    Directory of Open Access Journals (Sweden)

    Paolo Gorini


    Full Text Available We report five patients with variceal hemorrhage, in three cases secondary to diffuse thrombosis of the portal, superior mesenteric and splenic veins. Mesenteric angiography demonstrated patency of the inferior mesenteric vein (IMV in each, and successful portal decompression by anastomosis of the IMV to the left renal vein (n=4 or the inferior vena cava (n=1 was accomplished. Bleeding was permanently controlled: four patients have survived from one to eight years post-operatively. Because shunt procedures utilizing the IMV are technically straightforward, subtotally decompress the portal system and avoid the right upper quadrant, they may be advantageous in certain clinical settings.


    Abbasov, P A


    In 2012 - 2013 years in 265 patients for liver transplantation was performed, including in 224 (84.5%)--from a living donor, in 41 (15.5%)--from the dead body. Using a Foley catheter to stop bleeding, and the imposition of vascular sutures during endovenectomy in portal vein thrombosis (PVT) and its possible damage under all conditions. In particular, PVT IV degree (Grade IV) in order to restore blood flow in the graft using the left gastric and renal vein is an alternative, if they are cryopreserved vein may be suitably used.

  4. Varicose veins--Who should be referred? (United States)

    Onida, Sarah; Davies, Alun H; Franklin, Ian


    Varicose veins are a common, progressive condition in the UK, with significant negative effects on patients' quality of life. Despite their prevalence, access to secondary care for the assessment and treatment of varicose veins can be variable throughout the country.The National Institute of Health and Care Excellence guidelines developed in 2013 provide evidence-based guidance on the referral, assessment, and management of the patient with venous disease.In this article, we review the development of the guidelines for the management of varicose veins over the last 15 years, highlighting the latest changes in referral criteria.

  5. Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus;


    The competitive adsorption of arsenate and phosphate onto calcite was studied in batch experiments using calcite-equilibrated solutions. The solutions had circum-neutral pH (7–8.3) and covered a wide span in the activity of Ca2+ and View the MathML source. The results show that the adsorption...... that adsorption of arsenate onto calcite is of minor importance in most groundwater aquifers, as phosphate is often present at concentration levels sufficient to significantly reduce arsenate adsorption. The CD-MUSIC model for calcite was used successfully to model adsorption of arsenate and phosphate separately...

  6. Smaller calcite lattice deformation caused by occluded organic material in coccoliths than in mollusk shell

    DEFF Research Database (Denmark)

    Frølich, Simon; Sørensen, Henning Osholm; Hakim, Sepideh Sadat


    The growth and nucleation of biominerals are directed and affected by associated biological molecules. In this paper, we investigate the influence of occluded biomolecules on biogenic calcite from the coccolithophorid Pleurochrysis carterae and from chalk, a rock composed predominantly of fossil....... Two heating cycles allow us to differentiate the effects of thermal agitation and organic molecules. Single peak analysis and Rietveld refinement were combined to show significant differences resulting from the occluded biomolecules on the mineral phase in biogenic calcite in the mollusk shell....... This suggests that the interaction between biomolecules and calcite is not as tight in the coccoliths as in the shell. Although the shape of chalk has been preserved over millions of years, no major influence on the crystal lattice was observed in the chalk samples....

  7. Effects of L-Aspartic acid on the step retreat kinetics of calcite (United States)

    Yoshino, Toru; Kagi, Hiroyuki


    Effects of L-Aspartic acid (L-Asp) on step retreat kinetics in the dissolution of calcite were investigated. The step retreat velocities under surface-controlled kinetics were determined from in-situ atomic force microscopic observations using an improved flow-through system. Comparison of the present results with those obtained under a mixed kinetics condition revealed that the addition of L-Asp promotes the transport process in the calcite dissolution through acid-base and/or complex forming reactions in the diffusion boundary layer. Additionally, promotion of the acute and obtuse step retreats by the L-Asp additive was observed under surface-controlled kinetics. This report is the first to clarify that L-Asp promotes surface processes in the dissolution of calcite.

  8. Experimental diagenesis: insights into aragonite to calcite transformation of Arctica islandica shells by hydrothermal treatment (United States)

    Casella, Laura A.; Griesshaber, Erika; Yin, Xiaofei; Ziegler, Andreas; Mavromatis, Vasileios; Müller, Dirk; Ritter, Ann-Christine; Hippler, Dorothee; Harper, Elizabeth M.; Dietzel, Martin; Immenhauser, Adrian; Schöne, Bernd R.; Angiolini, Lucia; Schmahl, Wolfgang W.


    Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. In generating their mineralised hard parts, most marine invertebrates produce metastable aragonite rather than the stable polymorph of CaCO3, calcite. After death of the organism the physiological conditions, which were present during biomineralisation, are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features. In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 and 175 °C, with the main focus on 100 and 175 °C, reaction durations between 1 and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 °C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 °C (and at 0.9 MPa pressure) for 7 and 84 days. During hydrothermal alteration at 100 °C for 28 days most but not the entire biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments up to 174 °C, there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 °C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days

  9. VeinPLUS: A Transillumination and Reflection-based Hand Vein Database


    Gruschina, Alexander


    This paper gives a short summary of work related to the creation of a department-hosted hand vein database. After the introducing section, special properties of the hand vein acquisition are explained, followed by a comparison table, which shows key differences to existing well-known hand vein databases. At the end, the ROI extraction process is described and sample images and ROIs are presented.

  10. Polyphase vein mineralization in the Fennoscandian Shield at Åkerlandet, Järvsand, and Laisvall along the erosional front of the Caledonian orogen, Sweden (United States)

    Saintilan, Nicolas J.; Stephens, Michael B.; Spikings, Richard; Schneider, Jens; Chiaradia, Massimo; Spangenberg, Jorge E.; Ulianov, Alexey; Fontboté, Lluís


    The Åkerlandet, Järvsand, and Laisvall deposits in Sweden are calcite-fluorite-sulfide vein deposits and occurrences located close to the current erosional front of the Caledonian orogen and hosted by crystalline basement rocks in the Fennoscandian Shield. At Laisvall, basement-hosted veinlets occur beneath Ediacaran to Cambrian sandstones that host a strata-bound Pb-Zn deposit. The mineralized fractures at Åkerlandet and Järvsand occur along fault systems oriented N-S to NNW-SSE. Veins or veinlets strike NNW-SSE and NW-SE at Åkerlandet, NNE-SSW at Järvsand, and NNW-SSE and NNE-SSW to NE-SW at Laisvall. At Åkerlandet and Järvsand, fractures acted as conduits for hydrothermal fluids of variable composition and formed during separate tectonic events. At Åkerlandet, the fault zone with NNW-SSE strike shows kinematic indicators consistent with NE-SW bulk horizontal extension. At Järvsand, the calcite-fluorite-galena veins formed along R-Riedel shears related to the host N-S to NNW-SSE fault system. The kinematic indicators are consistent with NW-SE bulk horizontal extension, similar to the extensional deformation during the later part of the Caledonian orogeny (Silurian to Devonian). At Åkerlandet, adularia-quartz deposition was followed by sphalerite ± galena and finally by precipitation of fluorite and calcite. 40Ar-39Ar thermochronology of a single adularia sample did not yield a well-defined plateau age but the gas released at higher temperatures suggests an early Tonian (980 to 950 Ma) crystallization age, i.e., during the later part of the Sveconorwegian orogeny, although the data do not exclude other less likely interpretations. Previous fluid inclusion microthermometry and geochronological studies and new petrographic and geochemical results suggest that sphalerite ± galena mineralization formed from saline, relatively oxidizing, moderate-temperature, and slightly acidic hydrothermal fluids, either during the Ediacaran or the Middle Ordovician

  11. [Retinal vein occlusion in a young patient]. (United States)

    Zemba, Mihail; Ochinciuc, Uliana; Sarbu, Laura; Avram, Corina; Camburu, Raluca; Stamate, Alina


    We present a case report of a 27 years old pacient with central retinal vein occlussion and macular edema. The pacient has a significant reduction of the macular aedema with complete recovery of vision after the treatment.

  12. Vein of Galen Malformation: Outcome after Embolization

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap


    Full Text Available The neurodevelopmental outcome after endovascular treatment of vein of Galen malformation (VOGM in 27 patients seen between 1983 and 2002 was assessed by chart review and parental questionnaires at the University of California, San Francisco.

  13. Coccolithophore responses to environmental variability in the South China Sea: species composition and calcite content (United States)

    Jin, Xiaobo; Liu, Chuanlian; Poulton, Alex J.; Dai, Minhan; Guo, Xianghui


    Coccolithophore contributions to the global marine carbon cycle are regulated by the calcite content of their scales (coccoliths) and the relative cellular levels of photosynthesis and calcification rates. All three of these factors vary between coccolithophore species and with response to the growth environment. Here, water samples were collected in the northern basin of the South China Sea (SCS) during summer 2014 in order to examine how environmental variability influenced species composition and cellular levels of calcite content. Average coccolithophore abundance and their calcite concentration in the water column were 11.82 cells mL-1 and 1508.3 pg C mL-1, respectively, during the cruise. Water samples can be divided into three floral groups according to their distinct coccolithophore communities. The vertical structure of the coccolithophore community in the water column was controlled by the trophic conditions, which were regulated by mesoscale eddies across the SCS basin. The evaluation of coccolithophore-based calcite in the surface ocean also showed that three key species in the SCS (Emiliania huxleyi, Gephyrocapsa oceanica, Florisphaera profunda) and other larger, numerically rare species made almost equal contributions to total coccolith-based calcite in the water column. For Emiliania huxleyi biometry measurements, coccolith size positively correlated with nutrients (nitrate, phosphate), and it is suggested that coccolith length is influenced by light and nutrients through the regulation of growth rates. Larger-sized coccoliths were also linked statistically to low pH and calcite saturation states; however, it is not a simple cause and effect relationship, as carbonate chemistry was strongly co-correlated with the other key environmental factors (nutrients, light).

  14. Heterogeneous growth of cadmium and cobalt carbonate phases at the (101¯4) calcite surface

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Man; Ilton, Eugene S.; Engelhard, Mark H.; Qafoku, Odeta; Felmy, Andrew R.; Rosso, Kevin M.; Kerisit, Sebastien N.


    The ability of surface precipitates to form heteroepitaxially is an important factor that controls the extent of heterogeneous growth. In this work, the growth of cadmium and cobalt carbonate phases on (10-14) calcite surfaces is compared for a range of initial saturation states with respect to otavite (CdCO3) and sphaerocobaltite (CoCO3), two isostructural metal carbonates that exhibit different lattice misfits with respect to calcite. Calcite single crystals were reacted in static conditions for 16 hours with CdCl2 and CoCl2 aqueous solutions with initial concentrations 0.3 ≤ [Cd2+]0 ≤ 100 μM and 25 ≤ [Co2+]0 ≤ 200 μM. The reacted crystals were imaged in situ with atomic force microscopy (AFM) and analyzed ex situ with X-ray photoelectron spectroscopy (XPS). AFM images of Cd-reacted crystals showed the formation of large islands elongated along the direction, clear evidence of heteroepitaxial growth, whereas surface precipitates on Co-reacted crystals were small round islands. Deformation of calcite etch pits in both cases indicated the incorporation of Cd and Co at step edges. XPS analysis pointed to the formation of a Cd-rich (Ca,Cd)CO3 solid solution coating atop the calcite substrate. In contrast, XPS measurements of the Co-reacted crystals provided evidence for the formation of a mixed hydroxy-carbonate cobalt phase. The combined AFM and XPS results suggest that the lattice misfit between CoCO3 and CaCO3 ( 15% based on surface areas) is too large to allow for heteroepitaxial growth of a pure cobalt carbonate phase on calcite surfaces in aqueous solutions and at ambient conditions. The use of the satellite structure of the Co 2p3/2 photoelectron line as a tool for determining the nature of cobalt surface precipitates is also discussed.

  15. Efficacy of varicose vein surgery with preservation of the great safenous vein

    Directory of Open Access Journals (Sweden)

    Bernardo Cunha Senra Barros


    Full Text Available OBJECTIVE: To evaluate the efficacy of surgical treatment of varicose veins with preservation of the great saphenous vein. METHODS: We conducted a prospective study of 15 female patients between 25 and 55 years of age with clinical, etiologic, anatomic and pathophysiologic (CEAP classification 2, 3 and 4. The patients underwent surgical treatment of primary varicose veins with great saphenous vein (GSV preservation. Doppler ultrasonography exams were carried out in the first and third months postoperatively. The form of clinical severity of venous disease, Venous Clinical Severity Score (VCSS was completed before and after surgery. We excluded patients with history of deep vein thrombosis, smoking or postoperatively use of elastic stockings or phlebotonics. RESULTS: All patients had improved VCSS (p <0.001 and reduction in the diameter of the great saphenous vein (p <0.001. There was a relationship between VCSS and the GSV caliber, as well as with preoperative CEAP. There was improvement in CEAP class in nine patients when compared with the preoperative period (p <0.001. CONCLUSION: The varicose vein surgery with preservation of the great saphenous vein had beneficial effects to the GSV itself, with decreasing caliber, and to the symptoms when the vein had maximum caliber of 7.5 mm, correlating directly with the CEAP. The decrease in GSV caliber, even without complete abolition of reflux, leads to clinical improvement by decreasing the reflux volume.

  16. Isolated inferior mesenteric portal hypertension with giant inferior mesenteric vein and anomalous inferior mesenteric vein insertion

    Directory of Open Access Journals (Sweden)

    G Raghavendra Prasad


    Full Text Available Extrahepatic portal hypertension is not an uncommon disease in childhood, but isolated inferior mesenteric portal varices and lower gastrointestinal (GI bleed have not been reported till date. A 4-year-old girl presented with lower GI bleed. Surgical exploration revealed extrahepatic portal vein obstruction with giant inferior mesenteric vein and colonic varices. Inferior mesenteric vein was joining the superior mesenteric vein. The child was treated successfully with inferior mesenteric - inferior vena caval anastomosis. The child was relieved of GI bleed during the follow-up.

  17. CT in thrombosed dilated posterior epidural vein

    Energy Technology Data Exchange (ETDEWEB)

    Bammatter, S.; Schnyder, P.; Preux, J. de


    The authors report a case of thrombosis of the distal end of an enlarged right posterior epidural vein. The patient had a markedly narrow lumbar canal due to L5 spondylolisthesis. The dilated vein and the thrombosis were displayed by computed tomography but remained unrecognized until surgery. Pathogenesis of this condition is discussed. A review of the English, French and German literature revealed no prior radiological reports of a similar condition.

  18. Primary leiomyosarcoma of the innominate vein. (United States)

    Illuminati, Giulio; Miraldi, Fabio; Mazzesi, Giuseppe; D'urso, Antonio; Ceccanei, Gianluca; Bezzi, Marcello


    Primary venous leiomyosarcoma is rare. We report the case of a primary leiomyosarcoma of the left innominate vein, with neoplastic thrombus extending into the left jugular and subclavian veins. The tumor was curatively resected en bloc with anterior mediastinal and laterocervical lymphatics, through a median sternotomy prolonged into left cervicotomy. Primary venous sarcomas may be associated with prolonged survival in individual cases, with curative resection recommended as the standard treatment, in the absence of distant spread.

  19. The umbilical and paraumbilical veins of man.


    Martin, B F; Tudor, R G


    During its transit through the umbilicus structural changes occur in the thick wall of the extra-abdominal segment of the umbilical vein whereby the components of the intra-abdominal segment acquire an essentially longitudinal direction and become arranged in fibro-elastic and fibro-muscular zones. The vein lumen becomes largely obliterated by asymmetrical proliferation of loose subendothelial conective tissue. The latter forms a new inner zone within which a small segment of the lumen persis...

  20. Branch Retinal Vein Occlusion and Its Management

    Institute of Scientific and Technical Information of China (English)

    Desmond; Archer


    The natural course of Branch Retinal Vein Occlusion is determined by the site and completeness of the occlusion, the integrity of arterial perfusion to the affected sector and the efficiency of the developing collateral circulation. Most patients with tributary vein occlusion have some capillary fall out and microvascular incompetence in the distribution of the affected retina and vision is significantly compromised in over 50% of patients who have either chronic macular oedema or ischemia involving the...

  1. Templated and self-limiting calcite formation directed by coccolith organic macromolecules. (United States)

    Gal, Assaf; Wirth, Richard; Barkay, Zahava; Eliaz, Noam; Scheffel, André; Faivre, Damien


    The formation of intricately shaped crystalline minerals by organisms is orchestrated by specialized biomacromolecules. The macromolecules associated with coccoliths, nanometer-sized calcite crystal arrays produced by marine microalgae, can form a distinct calcium-rich phase via macromolecular recognition. Here, we show that this calcium-rich phase can be mineralized into a thin film of single-crystalline calcite by the balanced addition of carbonate ions. Such a crystallization process provides a strategy to direct crystalline products via local interactions between soluble macromolecules and compatible templates.

  2. Thickness and structure of the water film deposited from vapour on calcite surfaces

    DEFF Research Database (Denmark)

    Bohr, Jakob; Wogelius, Roy A.; Morris, Peter M.


    Synchrotron X-ray reflectivity (SXR) was used to measure the thickness of the water film that adsorbs on a {10¯14} cleavage surface of calcite (CaCO3) in a sample chamber where relative humidity could be controlled within the range from......Synchrotron X-ray reflectivity (SXR) was used to measure the thickness of the water film that adsorbs on a {10¯14} cleavage surface of calcite (CaCO3) in a sample chamber where relative humidity could be controlled within the range from...

  3. A generalised chemical precipitation modelling approach in wastewater treatment applied to calcite

    DEFF Research Database (Denmark)

    Mbamba, Christian Kazadi; Batstone, Damien J.; Flores Alsina, Xavier


    , the present study aims to identify a broadly applicable precipitation modelling approach. The study uses two experimental platforms applied to calcite precipitating from synthetic aqueous solutions to identify and validate the model approach. Firstly, dynamic pH titration tests are performed to define...... of the mineral particulate state (Xcryst) and, for calcite, have a 2nd order dependency (exponent n ¼ 2.05 ± 0.29) on thermodynamic supersaturation (s). Parameter analysis indicated that the model was more tolerant to a fast kinetic coefficient (kcryst) and so, in general, it is recommended that a large kcryst...

  4. Characteristics of a calcite "limestone"-marble from Macedonia, used as flux material

    Directory of Open Access Journals (Sweden)

    Hristova E.


    Full Text Available The phase characteristics of calcite "limestone"-marble from Banjany area village (near Skopje, Macedonia were examined by means of XRD, SEM microscope in polarizing and reflected lights, chemical, DT/TG-analyses. It was concluded as follows: - calcite (CaCO3 is a major mineral component (cca 80-90 % prevailing in the marble over the other minerals - dolomite is generally of minor importance (cca 10-20 % in the rock - quartz, micas graphite, pyrite represent typical accessories. As result of the mentioned phase characteristics, this raw materials was for a long time (more than 30 years used as flux in the iron and steel metallurgy in Macedonia.

  5. Birefringence measurements in single crystal sapphire and calcite shocked along the a axis (United States)

    Tear, Gareth R.; Chapman, David J.; Eakins, Daniel E.; Proud, William G.


    Calcite and sapphire were shock compressed along the direction (a axis) in a plate impact configuration. Polarimetery and Photonic Doppler Velocimetery (PDV) were used to measure the change in birefringence with particle velocity in the shock direction. Results for sapphire agree well with linear photoelastic theory and current literature showing a linear relationship between birefringence and particle velocity up to 310 m s-1. A maximum change in birefringence of 5% was observed. Calcite however showed anomolous behaviour with no detectable change in birefringence (less than 0.1%) over the range of particle velocities studied (up to 75 m s-1).

  6. Study on vibrational modes by group theory and infrared spectra by D FT for calcite crystal

    Institute of Scientific and Technical Information of China (English)

    Danhua Lou; Fengjiu Sun; Lijuan Li


    The factor group symmetry analysis (FSA) method and position symmetry analysis (PSA) method are used to analyze the vibrational modes of calcite (CaCO3) crystal, respectively. With the activated results of infrared and Raman spectra presented, strong points of each method are concluded. The infrared spectra are studied by using dynamics calculations based on density-functional theory (DFT) with the supercell model of calcite crystal. The frequencies of 27 normal modes are achieved, which are consistent with that by the group symmetry analysis very well, and fit with the experimental results better than the lattice dynamical methods.

  7. Galacturonomannan and Golgi-derived membrane linked to growth and shaping of biogenic calcite (United States)

    Marsh, M. E.; Ridall, A. L.; Azadi, P.; Duke, P. J.


    The coccolithophores are valuable models for the design and synthesis of composite materials, because the cellular machinery controlling the nucleation, growth, and patterning of their calcitic scales (coccoliths) can be examined genetically. The coccoliths are formed within the Golgi complex and are the major CaCO(3) component in limestone sediments-particularly those of the Cretaceous period. In this study, we describe mutants lacking a sulfated galacturonomannan and show that this polysaccharide in conjunction with the Golgi-derived membrane is directly linked to the growth and shaping of coccolith calcite but not to the initial orientated nucleation of the mineral phase.

  8. Cryogenic and non-cryogenic pool calcites reflect alternating permafrost and interglacial periods (Breitscheid-Erdbach Cave, Germany

    Directory of Open Access Journals (Sweden)

    D. K. Richter


    Full Text Available Weichselian cryogenic calcites collected in what is referred to as the "Rätselhalle" of the Breitscheid-Erdbach Cave were structurally classified as rhombohedral crystal and spherulitic crystal sinters. The carbon and oxygen isotopic composition of these precipitates corresponds to those of known cryogenic calcites of slow genesis of Central European caves (δ13C=+0.6 and −7.3‰; δ18O=−6.9 to −18.0‰. The variant carbon and oxygen isotope pattern differing between different caves is attributed to cave specific ventilation. Particularly, Breitscheid cryogenic calcites reflect mean levels of cave ventilation. By petrographic and geochemical comparisons of Weichselian cryogenic calcite with recent to sub-recent precipitates as well as Weichselian non-cryogenic calcites of the same locality, a model for the precipitation of these calcites is proposed. While the recent and sub-recent pool-calcites isotopically match the geochemistry of interglacial speleothems (stalagmites, etc., isotope ratios of Weichselian non-cryogenic pool-calcites reflect cooler conditions. Weichselian cryogenic calcites show a trend towards 18O-depleted values with higher carbon isotope ratios reflecting slow freezing of the precipitating solution. In essence, the isotope geochemistry of the Weichselian calcites reflects the climate history changing from overall initial permafrost (glacial conditions to an interglacial and subsequently to renewed permafrost conditions. The last stage then grades into the present-day warm period. Judging from the data compiled here, the last permafrost stage is followed by only one interglacial. During this interglacial, the cave ice melted and non-cryogenic Weichselian calcite precipitates were deposited on the cave ground or on fallen blocks, respectively.

  9. Endovascular treatment of iliac vein compression syndrome

    Institute of Scientific and Technical Information of China (English)

    MENG Qing-you; LI Xiao-qiang; QIAN Ai-min; SANG Hong-fei; RONG Jian-jie; ZHU Li-wei


    Background Iliac vein compression syndrome (IVCS),the symptomatic compression of the left common iliac vein between the right common iliac artery and the vertebrae,is not an uncommon condition.The aim of this research was to retrospectively evaluate long-term outcome and the significance of endovascular treatment in patients with left IVCS.Methods Between January 1997 and September 2008,296 patients received interventional therapy in the left common iliac vein.In the second stage,170 cases underwent saphenous vein high ligation and stripping.Two hundred and thirty-one cases were followed up over a period of 6 to 120 months (average 46 months) and evaluated for symptom improvement with color ultrasound and ascending venography.Results The stenotic or occlusive segments of the left iliac vein were successfully dilated in 285 cases,of whom 272 received stent implantation therapy.Most of the patients achieved satisfactory results on discharge.During the follow-up period,varicose veins were alleviated in 98.7% of the patients,and leg swelling disappeared or was obviously relieved in 84% of cases.About 85% of leg ulcers completely healed.The total patency rate was 91.7% as evaluated with color ultrasound and 91.5% with ascending venography.Conclusions Endovascular treatment of IVCS provides effective symptomatic improvement and good long-term patency in most patients.

  10. Portal vein thrombosis in children and adolescents. (United States)

    Schettino, Graziela C M; Fagundes, Eleonora D T; Roquete, Mariza L V; Ferreira, Alexandre R; Penna, Francisco J


    To review the literature on portal vein thrombosis in children and adolescents, focusing on its diagnosis, complications and treatment. The medical literature of the past 10 years was reviewed using the PubMed and MEDLINE search engines, with major focus on portal vein thrombosis and its clinical outcomes. The following keywords or expressions were used for the web search: portal vein thrombosis, extra-hepatic portal vein obstruction, prognosis, children, portal hypertension, esophagogastric varices. Additionally, we also reviewed the articles cited in the references of the initially selected papers, as well as relevant textbooks. Portal vein thrombosis is one of the most common causes of portal hypertension among children. The initial clinical manifestation is characterized either by episodes of upper gastrointestinal bleeding or by splenomegaly on routine clinical examination. The major complications include upper gastrointestinal bleeding, hypersplenism secondary to splenomegaly, growth retardation, and portal biliopathy. The diagnosis is made by abdominal Doppler ultrasonography. Treatment is targeted at the complications and includes primary and secondary prophylaxis against upper gastrointestinal bleeding (which results from the rupture of esophageal varices), and portosystemic shunting in selected cases. Portal vein thrombosis is one of the major triggers of upper gastrointestinal bleeding in children. Bleeding episodes have a remarkable effect on the quality of life of affected patients. Thus, appropriate diagnosis and treatment are needed in order to reduce morbidity and mortality.

  11. Veins improve fracture toughness of insect wings.

    Directory of Open Access Journals (Sweden)

    Jan-Henning Dirks

    Full Text Available During the lifetime of a flying insect, its wings are subjected to mechanical forces and deformations for millions of cycles. Defects in the micrometre thin membranes or veins may reduce the insect's flight performance. How do insects prevent crack related material failure in their wings and what role does the characteristic vein pattern play? Fracture toughness is a parameter, which characterises a material's resistance to crack propagation. Our results show that, compared to other body parts, the hind wing membrane of the migratory locust S. gregaria itself is not exceptionally tough (1.04±0.25 MPa√m. However, the cross veins increase the wing's toughness by 50% by acting as barriers to crack propagation. Using fracture mechanics, we show that the morphological spacing of most wing veins matches the critical crack length of the material (1132 µm. This finding directly demonstrates how the biomechanical properties and the morphology of locust wings are functionally correlated in locusts, providing a mechanically 'optimal' solution with high toughness and low weight. The vein pattern found in insect wings thus might inspire the design of more durable and lightweight artificial 'venous' wings for micro-air-vehicles. Using the vein spacing as indicator, our approach might also provide a basis to estimate the wing properties of endangered or extinct insect species.

  12. Not all calcite ballast is created equal: differing effects of foraminiferan and coccolith calcite on the formation and sinking of aggregates

    Directory of Open Access Journals (Sweden)

    K. Schmidt


    Full Text Available Correlation between particulate organic carbon (POC and calcium carbonate sinking through the deep ocean has led to the idea that ballast provided by calcium carbonate is important for the export of POC from the surface ocean. While this idea is certainly to some extent true, it is worth considering in more nuance, for example, examining the different effects on the aggregation and sinking of POC of small, non-sinking calcite particles like coccoliths and large, rapidly sinking calcite like planktonic foraminiferan tests. We have done that here in a simple experiment carried out in roller tanks that allow particles to sink continuously without being impeded by container walls. Coccoliths were efficiently incorporated into aggregates that formed during the experiment, increasing their sinking speed compared to similarly sized aggregates lacking added calcite ballast. The foraminiferan tests, which sank as fast as 700 m d−1, became associated with only very minor amounts of POC. In addition, when they collided with other, larger, foraminferan-less aggregates, they fragmented them into two smaller, more slowly sinking aggregates. While these effects were certainly exaggerated within the confines of the roller tanks, they clearly demonstrate that calcium carbonate ballast is not just calcium carbonate ballast- different forms of calcium carbonate ballast have notably different effects on POC aggregation, sinking, and export.

  13. Evaluation of leg varicose veins by MR venography

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Yoshifumi; Shiraishi, Tomokuni; Taira, Mitsuru [Kansai Medical Univ., Neyagawa, Osaka (Japan). Kohri Hospital; Imamura, Atsushi; Yamada, Hitoshi; Okuno, Masafumi; Kamiyama, Yasuo


    Preoperative evaluation was conducted on 30 patients with leg varicose veins by MR venography (MRV), and compared with conventional venography, MR images were performed by the 3D-SMASH Method. Compared with venography, MRV could more clearly demonstrate leg varicose veins with perforating veins than venography. It could detected fine varicose veins more than 2 mm in diameter, and deep veins. Furthermore, 3D observation enables accurate detection of the location of perforating vein. In conclusion, MRV is useful for the diagnosis of leg varicose vein. (author)

  14. Scattering removal for finger-vein image restoration. (United States)

    Yang, Jinfeng; Zhang, Ben; Shi, Yihua


    Finger-vein recognition has received increased attention recently. However, the finger-vein images are always captured in poor quality. This certainly makes finger-vein feature representation unreliable, and further impairs the accuracy of finger-vein recognition. In this paper, we first give an analysis of the intrinsic factors causing finger-vein image degradation, and then propose a simple but effective image restoration method based on scattering removal. To give a proper description of finger-vein image degradation, a biological optical model (BOM) specific to finger-vein imaging is proposed according to the principle of light propagation in biological tissues. Based on BOM, the light scattering component is sensibly estimated and properly removed for finger-vein image restoration. Finally, experimental results demonstrate that the proposed method is powerful in enhancing the finger-vein image contrast and in improving the finger-vein image matching accuracy.

  15. Looking at Dauphiné twins in vein quartz as a potential paleostress indicator (United States)

    Sintubin, Manuel; Wenk, Hans-Rudolf


    Paleostress studies commonly call upon (1) a fault slip data inversion technique, (2) a calcite twin stress inversion technique, (3) recrystallized grain size piezometry for quartz, or (4) direct measurements of residual lattice strain. Recent advances in orientation imaging microscopy (OIM) using electron backscatter diffraction (EBSD) on a scanning electron microscope (SEM) have revealed that Dauphiné twinning is very common in quartz in naturally deformed quartz-bearing rocks in a wide range of tectonometamorphic conditions. It has long been known that mechanical Dauphiné twinning in quartz can be stress-induced. Based on the results of an extensive EBSD-OIM analysis on vein quartz, taken from well-studied early to late-orogenic veins in the High-Ardenne slate belt (Germany, Belgium), we explore the potential use of mechanical Dauphiné twins as a paleostress indicator, possibly completing our toolbox for reconstructing paleostresses in the Earth's crust. The vein quartz studied precipitated in low-grade tectonometamorphic conditions (~200-400°C), typical for the brittle-plastic transition zone at the base of the seismogenic crust (~7-15km). Quartz has only been weakly affected by low to moderate temperature (200 to 400°C) crystal-plastic deformation. The samples show grains with a high concentration of Dauphiné twin boundaries and others free of twin boundaries, thus being untwinned or completely twinned. This pattern depends on the crystallographic orientation. Twin boundaries are arrested by grain or subgrain boundaries, suggesting that Dauphiné twinning occurred on a pre-existing fabric that resulted from crystal-plastic deformation. An analysis of the orientation distribution of the rhombs in the twinned variant domains of individual quartz (sub-)grains reveals a particular preferred orientation of the poles to rhombs. We will discuss the possible significance of these observations with respect to paleostresses that may have caused the mechanical

  16. Scattering Removal for Finger-Vein Image Restoration


    Jinfeng Yang; Ben Zhang; Yihua Shi


    Finger-vein recognition has received increased attention recently. However, the finger-vein images are always captured in poor quality. This certainly makes finger-vein feature representation unreliable, and further impairs the accuracy of finger-vein recognition. In this paper, we first give an analysis of the intrinsic factors causing finger-vein image degradation, and then propose a simple but effective image restoration method based on scattering removal. To give a proper description of f...

  17. An effective preprocessing method for finger vein recognition (United States)

    Peng, JiaLiang; Li, Qiong; Wang, Ning; Abd El-Latif, Ahmed A.; Niu, Xiamu


    The image preprocessing plays an important role in finger vein recognition system. However, previous preprocessing schemes remind weakness to be resolved for the high finger vein recongtion performance. In this paper, we propose a new finger vein preprocessing that includes finger region localization, alignment, finger vein ROI segmentation and enhancement. The experimental results show that the proposed scheme is capable of enhancing the quality of finger vein image effectively and reliably.

  18. Gonadal vein tumor thrombosis due to renal cell carcinoma

    Directory of Open Access Journals (Sweden)

    Hamidreza Haghighatkhah


    Full Text Available Renal cell carcinoma (RCC had a tendency to extend into the renal vein and inferior vena cava, while extension into the gonadal vein has been rarely reported. Gonadal vein tumor thrombosis appears as an enhancing filling defect within the dilated gonadal vein anterior to the psoas muscle and shows an enhancement pattern identical to that of the original tumor. The possibility of gonadal vein thrombosis should be kept in mind when looking at an imaging study of patients with RCC

  19. Augmented reality based real-time subcutaneous vein imaging system


    Ai, Danni; Yang, Jian; Fan, Jingfan; Zhao, Yitian; Song, Xianzheng; Shen, Jianbing; Shao, Ling; Wang, Yongtian


    A novel 3D reconstruction and fast imaging system for subcutaneous veins by augmented reality is presented. The study was performed to reduce the failure rate and time required in intravenous injection by providing augmented vein structures that back-project superimposed veins on the skin surface of the hand. Images of the subcutaneous vein are captured by two industrial cameras with extra reflective near-infrared lights. The veins are then segmented by a multiple-feature clustering method. V...

  20. Leaf vein segmentation using Odd Gabor filters and morphological operations


    Katyal, Vini; Aviral


    Leaf vein forms the basis of leaf characterization and classification. Different species have different leaf vein patterns. It is seen that leaf vein segmentation will help in maintaining a record of all the leaves according to their specific pattern of veins thus provide an effective way to retrieve and store information regarding various plant species in database as well as provide an effective means to characterize plants on the basis of leaf vein structure which is unique for every specie...

  1. Nutcracker Syndrome Complicated by Left Renal Vein Thrombosis

    Directory of Open Access Journals (Sweden)

    Faouzi Mallat


    Full Text Available Isolated renal vein thrombosis is a rare entity. We present a patient whose complaint of flank pain led to the diagnosis of a renal vein thrombosis. In this case, abdominal computed tomography angiography was helpful in diagnosing the nutcracker syndrome complicated by the renal vein thrombosis. Anticoagulation was started and three weeks later, CTA showed complete disappearance of the renal vein thrombosis. To treat the Nutcracker syndrome, we proposed left renal vein transposition that the patient consented to.

  2. Nutcracker syndrome complicated by left renal vein thrombosis. (United States)

    Mallat, Faouzi; Hmida, Wissem; Jaidane, Mehdi; Mama, Nadia; Mosbah, Faouzi


    Isolated renal vein thrombosis is a rare entity. We present a patient whose complaint of flank pain led to the diagnosis of a renal vein thrombosis. In this case, abdominal computed tomography angiography was helpful in diagnosing the nutcracker syndrome complicated by the renal vein thrombosis. Anticoagulation was started and three weeks later, CTA showed complete disappearance of the renal vein thrombosis. To treat the Nutcracker syndrome, we proposed left renal vein transposition that the patient consented to.

  3. Gonadal vein tumor thrombosis due to renal cell carcinoma. (United States)

    Haghighatkhah, Hamidreza; Karimi, Mohammad Ali; Taheri, Morteza Sanei


    Renal cell carcinoma (RCC) had a tendency to extend into the renal vein and inferior vena cava, while extension into the gonadal vein has been rarely reported. Gonadal vein tumor thrombosis appears as an enhancing filling defect within the dilated gonadal vein anterior to the psoas muscle and shows an enhancement pattern identical to that of the original tumor. The possibility of gonadal vein thrombosis should be kept in mind when looking at an imaging study of patients with RCC.

  4. The Effect of the Ca2+:CO32- Activity Ratio on Spiral Growth at the Calcite {1014} Surface

    DEFF Research Database (Denmark)

    Larsen, Kirsten Kolbjørn; Bechgaard, Klaus; Stipp, Susan Louise Svane


    Variation in the Ca2+ to CO 2¿ activity ratio of natural waters is rarely considered in models intended to describe calcite 3 growth. Atomic force microscopy (AFM) and differential interference contrast (DIC) microscopy were used to examine spiral growth on calcite f10¿14g surfaces from solutions...

  5. Corrosion cast study of the canine hepatic veins. (United States)

    Uršič, M; Vrecl, M; Fazarinc, G


    This study presents a detailed description of the distribution, diameters and drainage patterns of hepatic veins on the basis of the corrosion cast analysis in 18 dogs. We classified the hepatic veins in three main groups: the right hepatic veins of the caudate process and right lateral liver lobe, the middle hepatic veins of the right medial and quadrate lobes and the left hepatic veins of both left liver lobes and the papillary process. The corrosion cast study showed that the number of the veins in the Nomina Anatomica Veterinaria and most anatomical textbooks is underestimated. The number of various-sized hepatic veins of the right liver division ranged from 3 to 5 and included 1 to 4 veins from the caudate process and 2 to 4 veins from the right lateral liver lobe. Generally, in all corrosion casts, one middle-sized vein from the right part of the right medial lobe, which emptied separately in the caudal vena cava, was established. The other vein was a large-sized vein from the remainder of the central division, which frequently joined the common left hepatic vein from the left liver lobes. The common left hepatic vein was the largest of all the aforementioned hepatic veins.

  6. Differential early diagenetic low-Mg calcite cementation and rhythmic hardground development in Campanian-Maastrichtian chalk

    DEFF Research Database (Denmark)

    Molenaar, Nicolaas; J.J.P., Zijlstra


    The Campanian-Maastrichtian limestones in the south of the Netherlands are well-sorted fine-grained mudstones and silt- to fine sand-sized bioclastic grainstones. These limestones show a distinct lithological cyclicity manifested by fining-upward grain-size cycles with calcite-cemented layers...... and differences in the degree of early diagenesis. Cemented layers and hardgrounds are the result of differential early marine calcite cementation. In these limestones early calcite cementation cannot be explained by the supply of cementing materials from saturated seawater, An alternative model for early marine...... calcite cementation is proposed, in which early calcite cementation occurred within the sediment at some distance below the seafloor as a result of organic matter degradation and internal redistribution of bioclastic carbonate. Bacterial organic matter degradation caused dissolution of relatively unstable...

  7. [Calcified deep vein thrombosis in a patient with recurrent deep vein thrombosis and sarcoidosis]. (United States)

    Krmek, Dubravka Zupanić; Brajković, Ivana; Bekić, Dinko; Krnić, Antun; Jurković, Petar; Pavlović, Tomislav


    In this article, we present a rare case of calcified deep vein thrombosis in a 42-year-old female patient with frequent relapses of pulmonary sarcoidosis since 1995, for which she was on maintenance therapy with corticosteroids and with consequential secondary diabetes. Recent femoral vein thrombosis was diagnosed with color Doppler in 2012. At the same time, calcified occlusive thrombus in vena cava inferior from the level of renal vein to the confluence of hepatic veins was diagnosed on abdominal multi-slice computed tomography (MSCT). Digital subtraction venography (DSV) revealed a well-developed collateral circulation through the paravertebral veins, azygos and hemiazygos vein. There were no risk factors for thrombosis other than sarcoidosis and diabetes. Deep vein thrombosis is rarely described with sarcoidosis, but according to literature reports, it usually appears as a recurrence and simultaneously at multiple locations. According to the current knowledge, we cannot say for sure whether it is a disease with an increased risk of deep vein thrombosis or there is a combination of multiple risk factors present simultaneously.

  8. Microstratigraphic logging of calcite fabrics in speleothems as tool for palaeoclimate studies

    Directory of Open Access Journals (Sweden)

    Silvia Frisia


    Full Text Available The systematic documentation of calcite fabrics in stalagmites and flowstones provides robustness to palaeoclimate interpretation based on geochemical proxies, but it has been neglected because it is difficult to transform crystal morphologies into numerical values, and construct fabric time series. Here, general criteria that allow for coding fabrics of calcite composing stalagmites and flowstones is provided. Being based on known models of fabric development, the coding ascribes sequential numbers to each fabric, which reflect climate-related parameters, such as changes in drip rate variability, bio-mediation or diagenetic modifications. Acronyms are proposed for Columnar types, Dendritic, Micrite, Microsparite and Mosaic fabrics, whose use could then render possible comparison of calcite fabrics in stalagmites and flowstones from diverse latitudinal and altitudinal settings. The climatic and environmental significance of similarities in the geochemical signals and trends analysed in coeval stalagmites and flowstones (or differences in the signals and trends will be more robust when compared with fabric time series. This is particularly true where, such as in the Holocene, changes in geochemical values may be subtle, yet fabrics may show changes related to variations in supersaturation, drip rate or input of detrital particles or organic compounds. The proposed microstratigraphic logging allows recognition of changes in stable isotope ratio or trace element values that can be ascribed to hydrology and diagenesis, with considerable improvement of reconstructions based on the chemical proxies of stalagmites and flowstones composed of calcite.

  9. Origin of zoning within dedolomite and calcitized gypsum of the Mississippian Arroyo Penasco Group

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, D.S.


    The Mississippian Arroyo Penasco Group carbonates are the oldest Paleozoic rocks present in north-central New Mexico. These supratidal to shallow,subtidal sediments exhibit complex diagenetic fabrics produced by periods of pre-Pennsylvanian subaerial exposure. Both extensive recrystallization of the Espiritu Santo carbonates and brecciation of the overlying Macho Member of the Tererro Formation resulted from an extended period of Mississippian subaerial exposure of broad, low-relief tidal flats. Cathodoluminescent petrography indicates that the recrystallized limestones consist of calcite pseudomorphs of dolomite and gypsum. Dedolomite and calcitized gypsum crystals, with /sup 13/C//sup 12/C ratios of -2 to +1.5% PDB, range from highly zoned to uniformly luminescent. Electron microprobe analyses reveals variable Mn and Fe contents across the pseudomorphs which are responsible for differences in observed luminosity. These features are interpreted to reflect a period of subaerial exposure after deposition of Macho Member sediments, which caused dissolution of gypsum and dolomite by sulfate and Mg depleted meteoric fluids and produced the collapse breccia. Preservation of zoning within some pseudomorphs required simultaneous dissolution of gypsum and dolomite and precipitation of calcite. C-isotope data indicates a meteoric to mixed phreatic origin for pore fluids which precipitated calcite; repetitive zoning within dolomite and gypsum pseudomorphs is indicative of interactions between marine and meteoric phreatic fluids in the intertidal environment.

  10. Morphological and mechanical characterization of composite calcite/SWCNT-COOH single crystals. (United States)

    Calvaresi, Matteo; Falini, Giuseppe; Pasquini, Luca; Reggi, Michela; Fermani, Simona; Gazzadi, Gian Carlo; Frabboni, Stefano; Zerbetto, Francesco


    A growing number of classes of organic (macro)molecular materials have been trapped into inorganic crystalline hosts, such as calcite single crystals, without significantly disrupting their crystalline lattices. Inclusion of an organic phase plays a key role in enhancing the mechanical properties of the crystals, which are believed to share structural features with biogenic minerals. Here we report the synthesis and mechanical characterization of composite calcite/SWCNT-COOH single crystals. Once entrapped into the crystals SWCNT-COOH appeared both as aggregates of entangled bundles and nanoropes. Their observation was possible only after crystal etching, fracture or FIB (focused ion beam) cross-sectioning. SWCNT-COOHs occupied a small volume fraction and were randomly distributed into the host crystal. They did not strongly affect the crystal morphology. However, although the Young's modulus of composite calcite/SWCNT-COOH single crystals was similar to that of pure calcite their hardness increased by about 20%. Thus, SWCNT-COOHs provide an obstacle against the dislocation-mediated propagation of plastic deformation in the crystalline slip systems, in analogy with the well-known hardness increase in fiber-reinforced composites.

  11. Noncrystallographic calcite dendrites from hot-spring deposits at Lake Bogoria, Kenya

    Energy Technology Data Exchange (ETDEWEB)

    Jones, B. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Geology; Renaut, R.W. [Univ. of Saskatchewan, Saskatoon (Canada). Dept. of Geological Sciences


    Complex calcite crystals are an integral component of precipitates that form around the orifices of the Loburu and Mawe Moto hot springs on the shores of Lake bogoria, Kenya. Two types of large (up to 4 cm long) noncrystallographic dendrites are important components of these deposits. Feather dendrites are characterized by multiple levels of branching with individual branches developed through crystal splitting and spherulitic growth. Scandulitic (from Latin meaning shingle) dendrites are formed of stacked calcite crystals and are generally more compact than feather dendrites. These developed through the incremental stacking of rectangular-shaped calcite crystals that initially grew as skeletal crystals. Feather and scandulitic dendrites precipitated from the same waters in the same springs. The difference in morphology is therefore related to microenvironments in which they grew. Feather dendrites grew in any direction in pools of free-standing water provided that they were in constant contact with the solute. Conversely, scandulitic dendrites grew on rims of dams where water flowed over the surface in concert with the pulses of spring water. Thus, each calcite crystal in these dendrites represents one episode of crystal growth. The orientation of the component crystals in scandulitic dendrites is controlled by the topography of the dam or surface, not crystallographic criteria. The noncrystallographic dendrites formed from spring waters with initial temperatures of 90--99 C. Surficial water cooling, loss of CO{sub 2}, and presence of other elements that can interfere with crystal growth contributed to the formation of these unusual crystals.


    Directory of Open Access Journals (Sweden)

    Jan Ondruska


    Full Text Available The temperature dependences of the electrical DC conductivity of calcite waste, kaolinite and illite based ceramics were measured in the temperature range of 20 - 1050oC. The ceramic mass that was used was a mixture of 60 wt. % kaolinitic-illitic clay, 20 - 40 wt. % of this clay was fired at 1000oC for 90 min and 0, 10 and 20 wt. % of calcite waste. During heating, several processes take place - the release of the physically bound water, the burning of organic impurities, the dehydroxylation of kaolinite and illite, the decomposition of calcite, and the creation of anorthite and mullite. All of these processes were checked by means of differential thermal analysis (DTA, derivative thermogravimetry (DTG and thermodilatometry (TDA. At low temperatures (20 - 200oC, due to the release and decomposition of physically bound water, H+ and OH- are dominant charge carriers. After completion of release of physically bound water, up to the start of dehydroxylation at the temperature of ~ 450oC, the DC conductivity is dominated by a transport of Na+, K+, and Ca2+ ions. During dehydroxylation, H+ and OH- ions, which are released from kaolinite and illite lattices, contribute to the DC conductivity. Decomposition of calcite runs between ~ 700oC and 900oC. The glassy phase has a dominant influence on the DC conductivity in the fired ceramics. Its high conductivity is determined by the high mobility of Na+, K+, and Ca2+ ions.

  13. Elasticity and yielding of a calcite paste: scaling laws in a dense colloidal suspension. (United States)

    Liberto, Teresa; Le Merrer, Marie; Barentin, Catherine; Bellotto, Maurizio; Colombani, Jean


    We address the mechanical characterization of a calcite paste as a model system to investigate the relation between the microstructure and macroscopic behavior of colloidal suspensions. The ultimate goal is to achieve control of the elastic and yielding properties of calcite which will prove valuable in several domains, from paper coating to paint manufacture and eventually in the comprehension and control of the mechanical properties of carbonate rocks. Rheological measurements have been performed on calcite suspensions over a wide range of particle concentrations. The calcite paste exhibits a typical colloidal gel behavior, with an elastic regime and a clear yield strain above which it enters a plastic regime. The yield strain shows a minimum when increasing the solid concentration, connected to a change in the power law scaling of the storage modulus. In the framework of the classical fractal elasticity model for colloidal suspensions proposed by Shih et al. [Phys. Rev. A, 1990, 42, 4772], we interpret this behavior as a switch with the concentration from the strong-link regime to the weak-link regime, which had never been observed so far in one well-defined system without external or chemical forcing.

  14. Experimental study of the effect of mica on pressure solution of single crystal calcite (United States)

    Karcz, Z.; Laronne, L.; Polizzotti, R. S.; Ertas, D.; Aharonov, E.


    Field and experimental studies suggest that clays and micas accelerate the rate of pressure solution in various geomaterials. It is not clear however whether the "clay effect" is purely mechanical (i.e., maintaining a thick conduit for fluids at the contact) or whether its surface chemistry plays a critical role. A case in point is the insoluble clay filling of stylolites, which are thought by some to be merely an inert byproduct of dissolution, or by others to be a necessary feature for the propagation of the seam. To study the effect of mica on carbonate pressure solution, the corner of a cleaved calcite single crystal rhomb was polished into a triangular face (edge length ~ 200micron) and pressed against either muscovite or quartz discs to yield a nominal stress of 10-20MPa. Immersing the contact in pre-saturated (with respect to microcrystalline calcite) solutions of distilled water or 0.25M NH4Cl caused axial shortening of the crystal. This axial strain was measured with a capacitance sensor (perimeter roughens. The second stage is distinguished by high axial strain rates (~40nm/h) and changes in the size and spatial position of isolated contacts (diameterfaces adjacent to it. At this point we see no significant difference between the calcite quartz and calcite muscovite experiments under similar load conditions.

  15. Sorption of trace metals on calcite: Applicability of the surface precipitation model

    NARCIS (Netherlands)

    Comans, R.N.J.; Middelburg, J.J.


    Published Sorption isotherm data of Cd2+, Mn2+, Zn2+, and Co2+ on calcite are adequately described by the surface precipitation model which was originally developed by FArley et al. (1985) for the sorption of cations on metal oxides. In addition to monolayer adsorption, the model accounts for the fo

  16. Adsorption and migration of single metal atoms on the calcite (10.4) surface (United States)

    Pinto, H.; Haapasilta, V.; Lokhandwala, M.; Öberg, S.; Foster, Adam S.


    Transition metal atoms are one of the key ingredients in the formation of functional 2D metal organic coordination networks. Additionally, the co-deposition of metal atoms can play an important role in anchoring the molecular structures to the surface at room temperature. To gain control of such processes requires the understanding of adsorption and diffusion properties of the different transition metals on the target surface. Here, we used density functional theory to investigate the adsorption of 3d (Ti, Cr, Fe, Ni, Cu), 4d (Zr, Nb, Mo, Pd, Ag) and 5d (Hf, W, Ir, Pt, Au) transition metal adatoms on the insulating calcite (10.4) surface. We identified the most stable adsorption sites and calculated binding energies and corresponding ground state structures. We find that the preferential adsorption sites are the Ca–Ca bridge sites. Apart from the Cr, Mo, Cu, Ag and Au all the studied metals bind strongly to the calcite surface. The calculated migration barriers for the representative Ag and Fe atoms indicates that the metal adatoms are mobile on the calcite surface at room temperature. Bader analysis suggests that there is no significant charge transfer between the metal adatoms and the calcite surface.

  17. Strontium, nickel, cadmium, and lead substitution into calcite, studied by density functional theory

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Sakuma, Hiroshi; Stipp, Susan Louise Svane


    We have used density functional theory to predict the ion exchange energies for divalent cations Ni(2+), Sr(2+), Cd(2+), and Pb(2+) into a calcite {10.4} surface in equilibrium with water. Exchange energies were calculated for substitution into the topmost surface layer, at the mineral...

  18. Crystalline order of a water/glycine film coadsorbed on the (104) calcite surface. (United States)

    Magdans, Uta; Torrelles, Xavier; Angermund, Klaus; Gies, Hermann; Rius, Jordi


    For biomineralization processes, the interaction of the surface of calcite crystals with organic molecules is of particular importance. Especially, biologically controlled biomineralization as in exoskeletons of mollusks and echinoderms, e.g., sea urchin with single-crystal-like spines and shells,1-3 requires molecular control of seed formation and growth process. So far, experiments showing the obvious influence of organic molecules on the morphology and habit of calcite crystals have demonstrated the molecular dimension of the interaction.4-7 Details of the kinetics of growth and dissolution of mineral surfaces influenced by additives are available,8,9 but other experimental data about the structure of the organic/inorganic interface on the atomic scale are rare. On the other hand, complicated organic macromolecules which are involved in biomineralization are numerous, with only a small fraction solved in structure and function so far.10-13 Therefore, model systems have to be designed to provide a basic understanding for the interaction process.14 Using grazing incidence X-ray diffraction combined with molecular modeling techniques, we show that glycine molecules order periodically on the calcite (104) face in competition with the solvent water when exposed to an aqueous solution of the most simple amino acid. In contrast to the general concept of the charge-matching fit of organic molecules on mineral surfaces,4,14 glycine is not attached to the calcite surface directly but substitutes for water molecules in the second hydration layer.

  19. Higher Order Elastic Constants, Gruneisen Parameters and Lattice Thermal Expansion of Trigonal Calcite

    Directory of Open Access Journals (Sweden)

    Thresiamma Phlip


    Full Text Available The second- and third-order elastic constants of trigonal calcite have been obtained using the deformation theory. The strain energy density derived using the deformation theory is compared with the strain dependent lattice energy obtained from the elastic continuum model approximation to get the expressions for the second- and third-order elastic constants. Higher order elastic constants are a measure of the anharmonicity of a crystal lattice. The seven second-order elastic constants and the fourteen non-vanishing third-order elastic constants of trigonal calcite are obtained. The second-order elastic constants C11, which corresponds to the elastic stiffness along the basal plane of the crystal is greater than C33, which corresponds to the elastic stiffness tensor component along the c-axis of the crystal. First order pressure derivatives of the second-order elastic constants of calcite are evaluated. The higher order elastic constants are used to find the generalized Gruneisen parameters of the elastic waves propagating in different directions in calcite. The Brugger gammas are evaluated and the low temperature limit of the Gruneisen gamma is obtained. The results are compared with available reported values.

  20. Assembly Synthesis of Sheet-like Calcite Array and Stable-Vaterite by Supported Liquid Membrane

    Institute of Scientific and Technical Information of China (English)

    SUN,Dong-Mei(孙冬梅); WU,Qing-Sheng(吴庆生)


    Sheet-like calcite array and stable vaterite were synthesized by bio-mimetic supported liquid membrane system under different reaction conditions. Both of the FTIR spectra of products showed narrower peak at 1418 cm-1 than that of bulk CaCO3, and that of vaterite has a split in this peak.

  1. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica (United States)

    Elster, J.; Nedbalová, L.; Vodrážka, R.; Láska, K.; Haloda, J.; Komárek, J.


    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom for 8-9 months a year and their water chemistry is characterised by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial mat is composed of filamentous cyanobacteria and microalgae that are considered to be Antarctic endemic species. The mucilaginous black biofilm is covered by green spots formed by a green microalga and the macroscopic structures are packed together with fine material. Thin sections consist of rock substrate, soft biofilm, calcite spicules and mineral grains originating from different sources. The morphology of the spicules is typical of calcium carbonate monocrystals having a layered structure and specific surface texture, which reflect growth and degradation processes. The spicules' chemical composition and structure correspond to pure calcite. The lakes' age, altitude, morphometry, geomorphological and hydrological stability, including low sedimentation rates, together with thermal regime predispose the existence of this community. We hypothesise that the precipitation of calcite is connected with the photosynthetic activity of the green microalgae that were not recorded in any other lake in the region. This study has shown that the unique community producing biogenic calcite spicules is quite different to any yet described.


    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.;


    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters ha...

  3. Epr of Mn2+ Impurities in Calcite: A Detailed Study Pertinent to Marble Provenance Determination

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.;


    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters ha...

  4. Modelling how incorporation of divalent cations affects calcite wettability–implications for biomineralisation and oil recovery (United States)

    Andersson, M. P.; Dideriksen, K.; Sakuma, H.; Stipp, S. L. S.


    Using density functional theory and geochemical speciation modelling, we predicted how solid-fluid interfacial energy is changed, when divalent cations substitute into a calcite surface. The effect on wettability can be dramatic. Trace metal uptake can impact organic compound adsorption, with effects for example, on the ability of organisms to control crystal growth and our ability to predict the wettability of pore surfaces. Wettability influences how easily an organic phase can be removed from a surface, either organic compounds from contaminated soil or crude oil from a reservoir. In our simulations, transition metals substituted exothermically into calcite and more favourably into sites at the surface than in the bulk, meaning that surface properties are more strongly affected than results from bulk experiments imply. As a result of divalent cation substitution, calcite-fluid interfacial energy is significantly altered, enough to change macroscopic contact angle by tens of degrees. Substitution of Sr, Ba and Pb makes surfaces more hydrophobic. With substitution of Mg and the transition metals, calcite becomes more hydrophilic, weakening organic compound adsorption. For biomineralisation, this provides a switch for turning on and off the activity of organic crystal growth inhibitors, thereby controlling the shape of the associated mineral phase.

  5. Kinetics and Mechanisms of Cadmium Carbonate Heteroepitaxial Growth at the Calcite (101¯4) Surface

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Man; Kovarik, Libor; Arey, Bruce W.; Felmy, Andrew R.; Rosso, Kevin M.; Kerisit, Sebastien N.


    Elucidating the kinetics and mechanisms of heteroepitaxial nucleation and growth at mineral-water interfaces is essential to understanding surface reactivity in geochemical systems. In the present work, the formation of heteroepitaxial cadmium carbonate coatings at calcite-water interfaces was investigated by exposing calcite (10-14) surfaces to Cd-bearing aqueous solutions. In situ atomic force microscopy (AFM) was employed as the primary technique. The AFM results indicate that the heteroepitaxial growth of cadmium carbonate proceeds via three different mechanisms depending on the initial supersaturation of the aqueous solution: advancement of existing steps, nucleation and growth of three-dimensional (3D) islands, and nucleation and spread of two-dimensional (2D) nuclei. The 3D islands and 2D nuclei exhibit different morphologies and growth kinetics. The effects of supersaturation on heteroepitaxial growth mechanisms can be interpreted in terms of the free energy barrier for nucleation. At low initial supersaturation, where 3D nucleation dominates, it is hypothesized, from the growth rate and morphology of the 3D islands observed with AFM, that the crystallization of the overgrowth follows a non-classical pathway involving the formation of a surface precursor that is not fully crystalline, whereas high supersaturation favors the formation of crystalline 2D nuclei whose morphology is based on the atomic structure of the calcite substrate. Cross-sectional transmission electron microscopy (TEM) images reveal that the atomic structure of the interface between the cadmium carbonate coating and calcite shows perfect, dislocation-free epitaxy.

  6. Kinetics and mechanisms of cadmium carbonate heteroepitaxial growth at the calcite (10 1bar 4) surface (United States)

    Xu, Man; Kovarik, Libor; Arey, Bruce W.; Felmy, Andrew R.; Rosso, Kevin M.; Kerisit, Sebastien


    Elucidating the kinetics and mechanisms of heteroepitaxial nucleation and growth at mineral-water interfaces is essential to understanding surface reactivity in geochemical systems. In the present work, the formation of heteroepitaxial cadmium carbonate coatings at calcite-water interfaces was investigated by exposing calcite (10 1bar 4) surfaces to Cd-bearing aqueous solutions. In situ atomic force microscopy (AFM) was employed as the primary technique. The AFM results indicate that the heteroepitaxial growth of cadmium carbonate proceeds via three different mechanisms depending on the initial supersaturation of the aqueous solution: advancement of existing steps, nucleation and growth of three-dimensional (3D) islands, and nucleation and spread of two-dimensional (2D) nuclei. The 3D islands and 2D nuclei exhibit different morphologies and growth kinetics. The effects of supersaturation on heteroepitaxial growth mechanisms can be interpreted in terms of the free energy barrier for nucleation. At low initial supersaturation, where 3D nucleation dominates, it is hypothesized, from the growth rate and morphology of the 3D islands observed with AFM, that the crystallization of the overgrowth follows a non-classical pathway involving the formation of a surface precursor that is not fully crystalline, whereas high supersaturation favors the formation of crystalline 2D nuclei whose morphology is based on the atomic structure of the calcite substrate. Cross-sectional transmission electron microscopy (TEM) images reveal that the atomic structure of the interface between the cadmium carbonate coating and calcite shows perfect, dislocation-free epitaxy.

  7. Tracing formation and durability of calcite in a Punic-Roman cistern mortar (Pantelleria Island, Italy). (United States)

    Dietzel, Martin; Schön, Frerich; Heinrichs, Jens; Deditius, Artur P; Leis, Albrecht


    Ancient hydraulic lime mortar preserves chemical and isotopic signatures that provide important information about historical processing and its durability. The distribution and isotopic composition of calcite in a mortar of a well-preserved Punic-Roman cistern at Pantelleria Island (Italy) was used to trace the formation conditions, durability, and individual processing periods of the cistern mortar. The analyses of stable carbon and oxygen isotopes of calcite revealed four individual horizons, D, E, B-1 and B-2, of mortar from the top to the bottom of the cistern floor. Volcanic and ceramic aggregates were used for the production of the mortar of horizons E/D and B-1/B-2, respectively. All horizons comprise hydraulic lime mortar characterized by a mean cementation index of 1.5 ± 1, and a constant binder to aggregate ratio of 0.31 ± 0.01. This suggests standardized and highly effective processing of the cistern. The high durability of calcite formed during carbonation of slaked lime within the matrix of the ancient mortar, and thus the excellent resistance of the hydraulic lime mortar against water, was documented by (i) a distinct positive correlation of δ(18)Ocalcite and δ(13)Ccalcite; typical for carbonation through a mortar horizon, (ii) a characteristic evolution of δ(18)Ocalcite and δ(13)Ccalcite through each of the four mortar horizons; lighter follow heavier isotopic values from upper to lower part of the cistern floor, and (iii) δ(18)Ocalcite varying from -10 to -5 ‰ Vienna Pee Dee belemnite (VPDB). The range of δ(18)Ocalcite values rule out recrystallization and/or neoformation of calcite through chemical attack of water stored in cistern. The combined studies of the chemical composition of the binder and the isotopic composition of the calcite in an ancient mortar provide powerful tools for elucidating the ancient techniques and processing periods. This approach helps to evaluate the durability of primary calcite and demonstrates the

  8. Impact of amorphous precursor phases on magnesium isotope signatures of Mg-calcite (United States)

    Mavromatis, Vasileios; Purgstaller, Bettina; Dietzel, Martin; Buhl, Dieter; Immenhauser, Adrian; Schott, Jacques


    Various marine calcifiers form exoskeletons via an amorphous calcium carbonate (ACC) precursor phase and magnesium plays an important role in the temporary stabilization of this metastable phase. Thus, the use of Mg isotope ratios of marine biogenic carbonates as a proxy to reconstruct past seawater chemistry calls for a detailed understanding of the mechanisms controlling Mg isotope signatures during the formation and transformation of ACC to the final crystalline carbonate mineral. For this purpose we have investigated the Mg isotope fractionation between (Ca,Mg)CO3 solids and aqueous fluids at 25 °C and pH = 8.3 during (i) the direct precipitation of crystalline Mg-calcite and (ii) the formation of Mg-rich ACC (Mg-ACC) and its transformation to Mg-calcite. The outcome documents that the small Mg isotope fractionation between Mg-ACC and reactive fluid (ΔMg26ACC-fluid = - 1.0 ± 0.1 ‰) is not preserved during the transformation of the ACCs into Mg-calcite. Following a pronounced isotopic shift accompanying the transformation of Mg-ACC into Mg-calcite, Δ26Mgcalcite-fluid progressively decreases with reaction progress from ∼ - 3.0 ‰ to - 3.6 ‰, reflecting both the approach of isotopic equilibrium and the increase of calcite Mg content (to near 20 mol % Mg). In contrast the crystalline Mg-calcite precipitated directly from the reacting fluid, i.e. lacking a discernable formation of an amorphous precursor, exhibits only small temporal variations in Δ26Mgcalcite-fluid which overall is affected by the precipitation kinetics. The values found in this study at the onset of Mg-ACC precipitation for Mg isotope fractionation between Mg-ACC and the fluid (ΔMg26ACC-fluid = - 1.0 ‰) and between Mg-ACC and Mg2+(aq) (Δ(aq) 26 Mg ACC-Mg2+ = + 2.0 ‰) are consistent with the formation of a hydrated Ca nanoporous solid accommodating Mg bicarbonate/carbonate species in combination with hydrated magnesium. This material crossed by percolating channels filled with the

  9. A new approach for sclera vein recognition (United States)

    Thomas, N. L.; Du, Yingzi; Zhou, Zhi


    The vein structure in the sclera is stable over time, unique to each person, and well suited for human identification. A few researchers have performed sclera vein pattern recognition and reported promising initial results. Sclera recognition poses several challenges: the vein structure moves and deforms with the movement of the eye; images of sclera patterns are often defocused and/or saturated; and, most importantly, the vein structure in the sclera is multi-layered and has complex non-linear deformation. In this paper, we proposed a new method for sclera recognition: First, we developed a color-based sclera region estimation scheme for sclera segmentation. Second, we designed a Gabor wavelet-based sclera pattern enhancement method, and an adaptive thresholding method to emphasize and binarize the sclera vein patterns. Third, we proposed a line descriptor-based feature extraction, registration, and matching method that is illumination-, scale-, orientation-, and deformation-invariant, and can mitigate the multi-layered deformation effects exhibited in the sclera and tolerate segmentation error. It is empirically verified using the UBIRIS database that the proposed method can perform accurate sclera recognition.

  10. Optimization of subcutaneous vein contrast enhancement (United States)

    Zeman, Herbert D.; Lovhoiden, Gunnar; Deshmukh, Harshal


    A technique for enhancing the contrast of subcutaneous veins has been demonstrated. This techniques uses a near IR light source and one or more IR sensitive CCD TV cameras to produce a contrast enhanced image of the subcutaneous veins. This video image of the veins is projected back onto the patient's skin using a n LCD video projector. The use of an IR transmitting filter in front of the video cameras prevents any positive feedback from the visible light from the video projector from causing instabilities in the projected image. The demonstration contrast enhancing illuminator has been tested on adults and children, both Caucasian and African-American, and it enhances veins quite well in all cases. The most difficult cases are those where significant deposits of subcutaneous fat are present which make the veins invisible under normal room illumination. Recent attempts to see through fat using different IR wavelength bands and both linearly and circularly polarized light were unsuccessful. The key to seeing through fat turns out to be a very diffuse source of RI light. Results on adult and pediatric subjects are shown with this new IR light source.

  11. Ligation of superior mesenteric vein and portal to splenic vein anastomosis after superior mesenteric-portal vein confluence resection during pancreaticoduodenectomy – Case report (United States)

    Tang, Jianlin; Abbas, Jihad; Hoetzl, Katherine; Allison, David; Osman, Mahamed; Williams, Mallory; Zelenock, Gerald B.


    62 year old Caucasian female with pancreatic head mass abutting the superior mesenteric vein (SMV) presented with fine needle aspiration biopsy confirmed diagnosis of ductal adenocarcinoma. CT scan showed near complete obstruction of portal vein and large SMV collateral development. After 3 months of neoadjuvant therapy, her portal vein flow improved significantly, SMV collateral circulation was diminished. Pancreaticoduodenectomy (PD) and superior mesenteric portal vein (SMPV) confluence resection were performed; A saphenous vein interposition graft thrombosed immediately. The splenic vein remnant was distended and adjacent to the stump of the portal vein. Harvesting an internal jugular vein graft required extra time and using a synthetic graft posed a risk of graft thrombosis or infection. As a result, we chose to perform a direct anastomosis of the portal and splenic vein in a desperate situation. The anastomosis decompressed the mesenteric venous system, so we then ligated the SMV. The patient had an uneventful postoperative course, except transient ascites. She redeveloped ascites more than one year later. At that time a PET scan showed bilateral lung and right femur metastatic disease. She expired 15 months after PD. Conclusion The lessons we learned are (1) Before SMPV confluence resection, internal jugular vein graft should be ready for reconstruction. (2) Synthetic graft is an alternative for internal jugular vein graft. (3) Direct portal vein to SMV anastomosis can be achieved by mobilizing liver. (4) It is possible that venous collaterals secondary to SMV tumor obstruction may have allowed this patient's post-operative survival. PMID:25568802

  12. Calcite saturation state effects on cultured benthic foraminiferal trace-element distribution coefficients (United States)

    Hintz, C. J.; Shaw, T. J.; Chandler, G. T.; McCorkle, D. C.; Bernhard, J. M.; Blanks, J. K.


    Field studies have suggested that calcite saturation states (Ømega) near and below saturation alter trace element distribution coefficients in benthic foraminifera. Recent benthic foraminiferal culture experiments at the University of South Carolina investigated the response of trace element signatures to three different calcite saturation seawater environments by manipulating total alkalinity (TA). Starting with near-surface Gulf Stream water (Ømega = 3, TA=2380 μeq kg-1), two seawater reservoirs were titrated with HCl to lower their calcite saturation states (Ømega = 2, TA = 1910 μeq kg-1; Ømega = 1.1, TA = 1320 μeq kg-1). Mixed-species foraminiferal assemblages, with the calcite-specific fluorescent label calcein, were inoculated into 13 total culture chambers evenly distributed among the control and 2 treatment seawater reservoirs. These cultures were maintained at 7.2 ± 0.1 °C temperature and 36.6 ± 0.4 ‰ salinity for 8 months. Total alkalinity and dissolved inorganic carbon, measured biweekly, characterized the carbonate system and verified that the calcite saturation state remained stable over the culture duration. Trace element concentrations were also measured biweekly. Foraminiferal reproduction ( Bulimina marginata) was observed in each seawater chemistry. These individuals were utilized for trace element and stable isotope (data not presented here) analysis. Additionally, terminal chambers precipitated in alkalinity-adjusted cultures were identified by the absence of the pre-culture calcein label used on all inoculated foraminifera. These cultured chambers were separated by laser microdissection and analyzed for trace element content by isotope dilution inductively-coupled plasma mass spectrometry. We present the initial results of these trace element distribution coefficients measured in cultured benthic foraminifera from three different Ømega. This research was funded by National Science Foundation grants OCE-0351029 and OCE-0437366.

  13. The role of background electrolytes on the kinetics and mechanism of calcite dissolution (United States)

    Ruiz-Agudo, E.; Kowacz, M.; Putnis, C. V.; Putnis, A.


    The influence of background electrolytes on the mechanism and kinetics of calcite dissolution was investigated using in situ Atomic Force Microscopy (AFM). Experiments were carried out far from equilibrium by passing alkali halide salt (NaCl, NaF, NaI, KCl and LiCl) solutions over calcite cleavage surfaces. This AFM study shows that all the electrolytes tested enhance the calcite dissolution rate. The effect and its magnitude is determined by the nature and concentration of the electrolyte solution. Changes in morphology of dissolution etch pits and dissolution rates are interpreted in terms of modification in water structure dynamics (i.e. in the activation energy barrier of breaking water-water interactions), as well as solute and surface hydration induced by the presence of different ions in solution. At low ionic strength, stabilization of water hydration shells of calcium ions by non-paired electrolytes leads to a reduction in the calcite dissolution rate compared to pure water. At high ionic strength, salts with a common anion yield similar dissolution rates, increasing in the order Cl - salts with a common cation due to an increasing mobility of water around the calcium ion. Changes in etch pit morphology observed in the presence of F - and Li + are explained by stabilization of etch pit edges bonded by like-charged ions and ion incorporation, respectively. As previously reported and confirmed here for the case of F -, highly hydrated ions increased the etch pit nucleation density on calcite surfaces compared to pure water. This may be related to a reduction in the energy barrier for etch pit nucleation due to disruption of the surface hydration layer.

  14. Diagenetic Mg-calcite overgrowths on foraminiferal tests in the vicinity of methane seeps (United States)

    Panieri, Giuliana; Lepland, Aivo; Whitehouse, Martin J.; Wirth, Richard; Raanes, Morten P.; James, Rachael H.; Graves, Carolyn A.; Crémière, Antoine; Schneider, Andrea


    Methane is a potent greenhouse gas and some episodes of past global warming appear to coincide with its massive release from seafloor sediments as suggested by carbon isotope records of foraminifera. Here, we present structural, geochemical, and stable carbon isotope data from single foraminiferal calcite tests and authigenic Mg-calcite overgrowths in a sediment core recovered from an area of active methane seepage in western Svalbard at ca. 340 m water depth. The foraminifera are from intervals in the core where conventional bulk foraminiferal δ13 C values are as low as -11.3 ‰. Mg/Ca analyses of the foraminiferal tests reveal that even tests for which there is no morphological evidence for secondary authigenic carbonate can contain Mg-rich interlayers with Mg/Ca up to 220 mmol/mol. Transmission electron microscopy (TEM) of the contact point between the biogenic calcite and authigenic Mg-calcite layers shows that the two phases are structurally indistinguishable and they have the same crystallographic orientation. Secondary ion mass spectrometry (SIMS) analyses reveal that the Mg-rich layers are strongly depleted in 13C (δ13 C as low as -34.1 ‰). These very low δ13 C values indicate that the authigenic Mg-calcite precipitated from pore waters containing methane-derived dissolved inorganic carbon at the depth of the sulfate-methane transition zone (SMTZ). As the depth of the SMTZ can be located several meters below the sediment-seawater interface, interpretation of low foraminiferal δ13 C values in ancient sediments in terms of the history of methane seepage at the seafloor must be undertaken with care.

  15. Stable isotopes in pedogenic calcite: Can the positive linear covariant trends be used to quantify paleo-evaporation rates? (United States)

    Gröcke, D.; Ufnar, D.; Beddows, P. A.


    Paleoclimatological models suggest enhanced evaporation rates in subtropical regions during greenhouse- world conditions. Laboratory evaporation experiments show that calcites precipitated from variably saturated solutions yield a positive linear covariant trend (PLCT) in δ18O vs δ13C values. This investigation experimentally quantifies calcite PLCT so that δ13C of subtropical paleosol calcretes may be used as a regional proxy of paleo-evaporation rates. A series of powdered CaCO3 samples with δ18O and δ13C values of -19.6‰ and -37.2‰ VPDB respectively were dissolved in deionized water in a pressure sealed container; it also contained separate vials of calcite reacted with HCl to generate a range of pCO2 environments, thus simulating a soil atmosphere. The variable pCO2 conditions simulate expected soil atmosphere pCO2 conditions in a calcrete horizon during alternative phases of calcite dissolution and precipitation. After 24 hrs, the solutions were placed in an open beaker in an incubator at 36°C and allowed to evaporate. Aliquots of 100 μL were removed at 24 hr intervals and the time of calcite crystal nucleation was also noted. Water analyses yielded δ18O enrichments ranging from an initial value of -4.8‰ VSMOW to a range of +10.0‰ to +14.8‰ VSMOW after an evaporation period of 75 hrs. The most enriched water values were attained from the solutions formed under lower pCO2 conditions (more enriched calcite δ18O, δ13C). The array of calcite δ18O vs δ13C values fall upon a PLCT that projects from a theoretical meteoric calcite line (MCL) calculated from the incubation temperature and deionized water δ18O and δ13C values. The precipitated calcite δ18O values range from the MCL value of -8.8‰ VPDB to +0.5‰ VPDB. The higher pCO2 waters precipitated calcite very early during evaporation, and thus the δ18O and δ13C calcite values are slightly enriched relative to the theoretical MCL. The lower pCO2 conditions precipitated calcite late in

  16. MRI manifestations of enlarged superior ophthalmic vein

    Institute of Scientific and Technical Information of China (English)

    WEI Rui-li; MA Xiao-ye; CAI Ji-ping; ZHU Huang


    Objective:To assess MRI in the evaluation of enlarged superior ophthalmic vein (SOV). Methods: MRI manifestations and etiology of forty-six patients with enlarged SOV were analyzed. Results: SOV enlargement was noted to occur in carotid-cavernous fistula, ophthalmic Graves'disease, Tolosa-Hunt syndrome, inflammation at the apex of the orbit, orbital pseudotumor and thrombosis of cavernous sinus. The dilated vein appeared as signal void tubular shadows on both T1 and T2 weighted images. The diameter of the enlarged vein was 3.5-6.0 mm. Extraocular muscle enlargement, orbital pathologies, enlarged carotid cavernous sinus etc were also revealed by MRI. Conclusion: The dilated SOV may be well demonstrated by MRI. The etiological diagnosis of enlarged SOV can be made in combination with the associated findings.

  17. Pathogenesis of varicose veins - lessons from biomechanics. (United States)

    Pfisterer, Larissa; König, Gerd; Hecker, Markus; Korff, Thomas


    The development of varicose veins or chronic venous insufficiency is preceded by and associated with the pathophysiological remodelling of the venous wall. Recent work suggests that an increase in venous filling pressure is sufficient to promote varicose remodelling of veins by augmenting wall stress and activating venous endothelial and smooth muscle cells. In line with this, known risk factors such as prolonged standing or an obesity-induced increase in venous filling pressure may contribute to varicosis. This review focuses on biomechanically mediated mechanisms such as an increase in wall stress caused by venous hypertension or alterations in blood flow, which may be involved in the onset of varicose vein development. Finally, possible therapeutic options to counteract or delay the progress of this venous disease are discussed.

  18. Vein versus tragal perichondrium in stapedotomy. (United States)

    Schmerber, Sébastien; Cuisnier, Olivier; Charachon, Robert; Lavieille, Jean-Pierre


    To assess, in otosclerosis surgery, whether the vein or the tragal perichondrium in stapedotomy with interposition yields the better long-term hearing outcome. A retrospective chart review of prospectively collected audiometric data of 452 ears. Academic tertiary otology-neurotology referral center. Four hundred fifty-two stapedotomies with interposition were performed in 412 patients (bilateral in 40 patients) by the senior author (R.C.) between 1987 and 1998. A tragal perichondrium graft was used in 314 cases and a vein graft was used in 138 cases as sealing material of the oval window. Audiometric data were recorded at 4 months, at 1 year, and at 3 years after surgery after American Academy of Otolaryngology-Head and Neck Surgery guidelines, except for thresholds at 3 kHz, which were not available and which were replaced with those at 4 kHz. There were no significant intergroup differences in initial or late postoperative hearing outcome with regard to change in the pure-tone average bone conduction and air-bone gaps, or sensorineural hearing loss. Ears treated with a vein graft showed statistically better postoperative 2-kHz air-bone gap closure (p =0.0157), but the pure-tone average air-bone gap difference was not significant. Postoperative air-bone gap closure to within 10 dB was achieved in 91% of cases in the vein group and in 76% of cases in the perichondrium group. Specific study of the bone conduction level at 4 kHz showed a sensorineural hearing loss greater than 10 dB in 8% of cases in the vein group and in 11% of cases in the perichondrium group. One case of complete sensorineural hearing loss was observed with a tragal perichondrium graft (0.22%). These results suggest that the vein should be preferred to the tragal perichondrium in stapedotomy with interposition.

  19. Duplicated Ižnternal Juguler Vein

    Directory of Open Access Journals (Sweden)

    Ahmet Kirbas


    Full Text Available    Duplicated internal juguler vein (DIJV is a rare anomaly and reported incidence is 0.4 % in the literature. A 45-year-old female patient was referred to our hospital because of non pulsatile neck swelling. The magnetic resonance image (MRI showed left IJVs divided at the angles of the mandible running anterior to the common carotid artery until anterior mediastinal level. Clinicians should be aware of the rare possibility of duplicated IJVs in patients presenting with neck swelling. The development of imaging technics have revealed more cases of duplicated internal juguler vein.

  20. Deep vein thrombosis: a clinical review

    Directory of Open Access Journals (Sweden)

    Kesieme EB


    Full Text Available Emeka Kesieme1, Chinenye Kesieme2, Nze Jebbin3, Eshiobo Irekpita1, Andrew Dongo11Department of Surgery, Irrua Specialist Teaching Hospital, Irrua, Nigeria; 2Department of Paediatrics, Irrua Specialist Teaching Hospital, Irrua, Nigeria; 3Department of Surgery, University of Port Harcourt Teaching Hospital, Port-Harcourt, NigeriaBackground: Deep vein thrombosis (DVT is the formation of blood clots (thrombi in the deep veins. It commonly affects the deep leg veins (such as the calf veins, femoral vein, or popliteal vein or the deep veins of the pelvis. It is a potentially dangerous condition that can lead to preventable morbidity and mortality.Aim: To present an update on the causes and management of DVT.Methods: A review of publications obtained from Medline search, medical libraries, and Google.Results: DVT affects 0.1% of persons per year. It is predominantly a disease of the elderly and has a slight male preponderance. The approach to making a diagnosis currently involves an algorithm combining pretest probability, D-dimer testing, and compression ultrasonography. This will guide further investigations if necessary. Prophylaxis is both mechanical and pharmacological. The goals of treatment are to prevent extension of thrombi, pulmonary embolism, recurrence of thrombi, and the development of complications such as pulmonary hypertension and post-thrombotic syndrome.Conclusion: DVT is a potentially dangerous condition with a myriad of risk factors. Prophylaxis is very important and can be mechanical and pharmacological. The mainstay of treatment is anticoagulant therapy. Low-molecular-weight heparin, unfractionated heparin, and vitamin K antagonists have been the treatment of choice. Currently anticoagulants specifically targeting components of the common pathway have been recommended for prophylaxis. These include fondaparinux, a selective indirect factor Xa inhibitor and the new oral selective direct thrombin inhibitors (dabigatran and selective

  1. Renal actinomycosis with concomitant renal vein thrombosis. (United States)

    Chang, Dong-Suk; Jang, Won Ik; Jung, Ji Yoon; Chung, Sarah; Choi, Dae Eun; Na, Ki-Ryang; Lee, Kang Wook; Shin, Yong-Tai


    Renal actinomycosis is a rare infection caused by fungi of the genus Actinomyces. A 74-year-old male was admitted to our hospital because of gross hematuria with urinary symptoms and intermittent chills. Computed tomography of the abdomen showed thrombosis in the left renal vein and diffuse, heterogeneous enlargement of the left kidney. After nephrectomy, sulfur granules with chronic suppurative inflammation were seen microscopically, and the histopathological diagnosis was renal actinomycosis. Our case is the first report of renal actinomycosis with renal vein thrombosis.

  2. Portal vein thrombosis in patients with cirrhosis

    DEFF Research Database (Denmark)

    von Köckritz, Leona; De Gottardi, Andrea; Trebicka, Jonel


    Portal vein thrombosis (PVT) is frequent in patients with liver cirrhosis and possible severe complications such as mesenteric ischemia are rare, but can be life-threatening. However, different aspects of clinical relevance, diagnosis and management of PVT are still areas of uncertainty and inves......Portal vein thrombosis (PVT) is frequent in patients with liver cirrhosis and possible severe complications such as mesenteric ischemia are rare, but can be life-threatening. However, different aspects of clinical relevance, diagnosis and management of PVT are still areas of uncertainty...

  3. Postpartum Ovarian Vein Thrombophlebitis with Staphylococcal Bacteremia (United States)

    Parino, Eduardo; Mulinaris, Eric; Saccomano, Edgardo; Gallo, Juan Cruz; Kohan, Gabriel


    A 34-year-old female patient presented with fever and right flank pain ten days after uncomplicated vaginal delivery. CT examination revealed right ovarian vein thrombosis and methicillin-resistant Staphylococcus aureus (MRSA) was isolated from blood cultures. No other source of bacteremia was found. Antibiotic therapy and anticoagulation with enoxaparin were instituted. Fourteen days after admission, she was discharged in good condition. Although a very uncommon complication after spontaneous vaginal delivery, septic ovarian vein thrombophlebitis should be suspected in cases of persistent puerperal fever when other diagnostic possibilities have been excluded. PMID:26221549

  4. Kinematics of the Neogene Terror Rift: Constraints from calcite twinning strain in AND-1B core, McMurdo Ice Shelf (United States)

    Paulsen, T.; Wilson, T. J.; Demosthenous, C.; Millan, C.; Jarrard, R. D.; Laufer, A.


    Strain analyses of mechanically twinned calcite in veins and faults hosted by Neogene (13.6 Ma to 4.3 Ma) sedimentary and volcanic rocks recovered within the ANDRILL AND-1B drill core from the Terror Rift in the southern Ross Sea, Antarctica, yield prolate and oblate ellipsoids with principal shortening and extension strains ranging from 0.1% to 8.5%. The majority of samples show homogeneous coaxial strain predominantly characterized by subvertical shortening, which we attribute to lithostatic loading in an Andersonian normal faulting stress regime during sedimentary and ice sheet burial of the stratigraphic sequence. The overall paucity of a non-coaxial layer-parallel shortening signal in the AND-1B twin populations suggests that horizontal compressive stresses predicted by Neogene transtensional kinematic models for the rift system have been absent or of insufficient magnitude to cause a widespread noncoaxial strain overprint. Limited numbers of oriented samples yield a possible average ESE extension direction for the rift that is subparallel to other indicators of Neogene extension. The lack of horizontal shortening in the twin data suggests the Neogene Terror Rift system either lacks a strong longitudinal strike-slip component, or that spatial partitioning of strain controls the maximum shortening axes seen in rocks of this age.

  5. Image Quality Enhancement Using the Direction and Thickness of Vein Lines for Finger-Vein Recognition

    Directory of Open Access Journals (Sweden)

    Young Ho Park


    Full Text Available On the basis of the increased emphasis placed on the protection of privacy, biometric recognition systems using physical or behavioural characteristics such as fingerprints, facial characteristics, iris and finger-vein patterns or the voice have been introduced in applications including door access control, personal certification, Internet banking and ATM machines. Among these, finger-vein recognition is advantageous in that it involves the use of inexpensive and small devices that are difficult to counterfeit. In general, finger-vein recognition systems capture images by using near infrared (NIR illumination in conjunction with a camera. However, such systems can face operational difficulties, since the scattering of light from the skin can make capturing a clear image difficult. To solve this problem, we proposed new image quality enhancement method that measures the direction and thickness of vein lines. This effort represents novel research in four respects. First, since vein lines are detected in input images based on eight directional profiles of a grey image instead of binarized images, the detection error owing to the non-uniform illumination of the finger area can be reduced. Second, our method adaptively determines a Gabor filter for the optimal direction and width on the basis of the estimated direction and thickness of a detected vein line. Third, by applying this optimized Gabor filter, a clear vein image can be obtained. Finally, the further processing of the morphological operation is applied in the Gabor filtered image and the resulting image is combined with the original one, through which finger-vein image of a higher quality is obtained. Experimental results from application of our proposed image enhancement method show that the equal error rate (EER of finger-vein recognition decreases to approximately 0.4% in the case of a local binary pattern-based recognition and to approximately 0.3% in the case of a wavelet transform

  6. The Use Of The VEINES-QOL/Sym Questionnaire In Patients Operated For Varicose Veins

    Directory of Open Access Journals (Sweden)

    Migdalski Łukasz


    Full Text Available Venous insufficiency is a common, chronic disease that affects nearly half of the population in highly developed countries. The vast majority of affected patients suffer from varicose veins (VV. Recently, the priority in medicine has been patient satisfaction with treatment and high quality of life. Therefore, disease-specific questionnaires that measure quality of life have been developed. One of these is VEINES-QOL/Sym with two subscales that assess quality of life and disease symptoms. To date, it has been used to examine patients with venous ulcers and thrombosis. No data are available concerning the use of VEINES to assess patients after VV surgery.

  7. An unusual case: right proximal ureteral compression by the ovarian vein and distal ureteral compression by the external iliac vein

    Directory of Open Access Journals (Sweden)

    Halil Ibrahim Serin


    Full Text Available A 32-years old woman presented to the emergency room of Bozok University Research Hospital with right renal colic. Multidetector computed tomography (MDCT showed compression of the proximal ureter by the right ovarian vein and compression of the right distal ureter by the right external iliac vein. To the best of our knowledge, right proximal ureteral compression by the ovarian vein together with distal ureteral compression by the external iliac vein have not been reported in the literature. Ovarian vein and external iliac vein compression should be considered in patients presenting to the emergency room with renal colic or low back pain and a dilated collecting system.

  8. 3D Mapping of calcite and a demonstration of its relevance to permeability evolution in reactive fractures (United States)

    Ellis, Brian R.; Peters, Catherine A.


    There is a need to better understand reaction-induced changes in fluid transport in fractured shales, caprocks and reservoirs, especially in the context of emerging energy technologies, including geologic carbon sequestration, unconventional natural gas, and enhanced geothermal systems. We developed a method for 3D calcite mapping in rock specimens. Such information is critical in reactive transport modeling, which relies on information about the locations and accessible surface area of reactive minerals. We focused on calcite because it is a mineral whose dissolution could lead to substantial pathway alteration because of its high solubility, fast reactivity, and abundance in sedimentary rocks. Our approach combines X-ray computed tomography (XCT) and scanning electron microscopy. The method was developed and demonstrated for a fractured limestone core containing about 50% calcite, which was 2.5 cm in diameter and 3.5 cm in length and had been scanned using XCT. The core was subsequently sectioned and energy dispersive X-ray spectroscopy was used to determine elemental signatures for mineral identification and mapping. Back-scattered electron microscopy was used to identify features for co-location. Finally, image analysis resulted in characteristic grayscale intensities of X-ray attenuation that identify calcite. This attenuation mapping ultimately produced a binary segmented 3D image of the spatial distribution of calcite in the entire core. To demonstrate the value of this information, permeability changes were investigated for hypothetical fractures created by eroding calcite from 2D rock surfaces. Fluid flow was simulated using a 2D steady state model. The resulting increases in permeability were profoundly influenced by the degree to which calcite is contiguous along the flow path. If there are bands of less reactive minerals perpendicular to the direction of flow, fracture permeability may be an order of magnitude smaller than when calcite is contiguous

  9. Environmental controls for the precipitation of different fibrous calcite cement fabrics (United States)

    Ritter, Ann-Christine; Wiethoff, Felix; Neuser, Rolf D.; Richter, Detlev K.; Immenhauser, Adrian


    Abiogenic calcite cements are widely used as climate archives. They can yield information on environmental change and climate dynamics at the time when the sediment was lithified in a (marine) diagenetic environment. Radiaxial-fibrous (RFC) and fascicular-optic fibrous (FOFC) calcite cements are two very common and similar pore-filling cement fabrics in Palaeozoic and Mesozoic carbonate rocks (Richter et al., 2011) and in Holocene Mg-calcitic speleothems (Richter et al., 2015). Both fabrics are characterised by distinct crystallographic properties. Current research has shown that these fabrics are often underexplored and that a careful combination of conservative and innovative proxies allows for a better applicability of these carbonate archives to paleoenvironmental reconstructions (Ritter et al., 2015). A main uncertainty in this context is that it is still poorly understood which parameters lead to the formation of either RFC or FOFC and if differential crystallographic parameters affect proxy data from these fabrics. This study aims at a better understanding of the environmental factors that may control either RFC or FOFC precipitation. Therefore, suitable samples (a stalagmite and a Triassic marine cement succession), each with clearly differentiable layers of RFC and FOFC, were identified and analysed in high detail using a multi-proxy approach. Detailed thin section and cathodoluminescence analysis of the samples allowed for a precise identification of layers consisting solely of either RFC or FOFC. Isotopic (δ13C, δ18O) as well as trace elemental compositions have been determined and the comparison of data obtained from these different carbonate archives sheds light on changes in environmental parameters during RFC or FOFC precipitation. References: Richter, D.K., et al., 2011. Radiaxial-fibrous calcites: A new look at an old problem. Sedimentary Geology, 239, 26-36 Richter, D.K., et al., 2015. Radiaxial-fibrous and fascicular-optic Mg-calcitic cave

  10. U-Th dating of calcite corals from the Gulf of Aqaba (United States)

    Yehudai, Maayan; Lazar, Boaz; Bar, Neta; Kiro, Yael; Agnon, Amotz; Shaked, Yonathan; Stein, Mordechai


    Most of the fossil corals in the elevated reef terraces along the Gulf of Aqaba (GOA) were extensively altered to calcite. This observation indicates extensive interaction with freshwater, possibly when the terraces passed through a coastal aquifer that existed along the shores of the GOA, implying a wetter climate during the time of recrystallization from aragonite to calcite. Thus, dating of the recrystallization events should yield the timing of past wetter conditions in the current hyper-arid area of the GOA. In the present study, 18 aragonite and calcite corals were collected from several elevated coral reef terraces off the coast, south of the city of Aqaba. While aragonite corals were dated with the conventional closed system age equation (assuming zero initial Th), the dating of the calcite corals required the development of adequate equations to allow the calculation of both the initial formation age of the aragonite corals and the time of recrystallization to calcite. The two age calculations were based on the assumptions that each reef terrace went through a single and rapid recrystallization event and that the pristine aragonite corals were characterized by a rather uniform initial U concentration, typical for pristine modern corals. Two recrystallization events were identified at 104 ± 6 ka and 124 ± 8 ka. The ages coincide with the timing of sapropel events S4 and S5, respectively, when the African monsoon induced enhanced wetness in the desert area. Considering the age uncertainties, the times of formation of the two major reef terraces are estimated to be ∼124 ka (reef terrace R2) and ∼130 ka (reef terrace R3), matching the peaks in the global sea level during the last interglacial MIS 5e stage. Apparently, sea level of the GOA did not fluctuate a lot during the period between ∼130 ka and ∼104 ka and remained close to the Marine Isotopic stage (MIS) 5e highstand. The availability of freshwater (during the sapropel periods) and limited sea

  11. Experimental Research on Microscopic Indicators of Temperature's Returning-to-Zero in Deformation of Calcite and Discussions of Correlation Problem

    Institute of Scientific and Technical Information of China (English)

    Yao Daquan; Zhai Hongtao


    In order to determine the degree of returning-to-zero of temperatures of deformed calcite, a series of rock-breaking experiments were designed to test calcite-rich limestone samples under fixed confining pressures and different temperatures. The consolidated deformed samples in their initial state were observed under a microscope and the microscopic indicators in different zero-returning states were put forward, thus providing a microscopic foundation for evaluation of reliability of dating values of deformation in calcite. At last, the correction of dating values of deformation for samples whose temperature has not yet returned to zero is discussed.

  12. Comparison of Dissolution and Surface Reactions Between Calcite and Aragonite in L-Glutamic and L-Aspartic Acid Solutions

    Directory of Open Access Journals (Sweden)

    Kwangsuk You


    Full Text Available We have investigated dissolution and surface reaction of calcite and aragonite in amino acid solutions of L-glutamic (L-glu and L-aspartic acid (L-asp at weak acidity of above pH 3. The surface reactions of calcite and aragonite were related with the dissolution. Calcite was dissolved in both solutions but the dissolution was limited by an adsorption of Ca-carboxylate salt. Aragonite was neither dissolved nor reacted in amino acid solutions because the crystal surface consisted of a hard to dissolve structure.

  13. Interactions of the Calcite {10.4} Surface with Organic Compounds: Structure and Behaviour at Mineral – Organic Interfaces

    DEFF Research Database (Denmark)

    Hakim, S. S.; Olsson, M. H. M.; Sørensen, H. O.


    The structure and the strength of organic compound adsorption on mineral surfaces are of interest for a number of industrial and environmental applications, oil recovery, CO2 storage and contamination remediation. Biomineralised calcite plays an essential role in the function of many organisms...... that control crystal growth with organic macromolecules. Carbonate rocks, composed almost exclusively of calcite, host drinking water aquifers and oil reservoirs. In this study, we examined the ordering behaviour of several organic compounds and the thickness of the adsorbed layers formed on calcite {10...

  14. Endovascular Radiofrequency Ablation for Varicose Veins (United States)


    Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular radiofrequency ablation (RFA) for the treatment of primary symptomatic varicose veins. Background The Ontario Health Technology Advisory Committee (OHTAC) met on August 26th, 2010 to review the safety, effectiveness, durability, and cost-effectiveness of RFA for the treatment of primary symptomatic varicose veins based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition Varicose veins (VV) are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad

  15. Varicose Veins: Role of Mechanotransduction of Venous Hypertension (United States)

    Atta, Hussein M.


    Varicose veins affect approximately one-third of the adult population and result in significant psychological, physical, and financial burden. Nevertheless, the molecular pathogenesis of varicose vein formation remains unidentified. Venous hypertension exerted on veins of the lower extremity is considered the principal factor in varicose vein formation. The role of mechanotransduction of the high venous pressure in the pathogenesis of varicose vein formation has not been adequately investigated despite a good progress in understanding the mechanomolecular mechanisms involved in transduction of high blood pressure in the arterial wall. Understanding the nature of the mechanical forces, the mechanosensors and mechanotransducers in the vein wall, and the downstream signaling pathways will provide new molecular targets for the prevention and treatment of varicose veins. This paper summarized the current understanding of mechano-molecular pathways involved in transduction of hemodynamic forces induced by blood pressure and tries to relate this information to setting of venous hypertension in varicose veins. PMID:22489273

  16. Varicose Veins: Role of Mechanotransduction of Venous Hypertension

    Directory of Open Access Journals (Sweden)

    Hussein M. Atta


    Full Text Available Varicose veins affect approximately one-third of the adult population and result in significant psychological, physical, and financial burden. Nevertheless, the molecular pathogenesis of varicose vein formation remains unidentified. Venous hypertension exerted on veins of the lower extremity is considered the principal factor in varicose vein formation. The role of mechanotransduction of the high venous pressure in the pathogenesis of varicose vein formation has not been adequately investigated despite a good progress in understanding the mechanomolecular mechanisms involved in transduction of high blood pressure in the arterial wall. Understanding the nature of the mechanical forces, the mechanosensors and mechanotransducers in the vein wall, and the downstream signaling pathways will provide new molecular targets for the prevention and treatment of varicose veins. This paper summarized the current understanding of mechano-molecular pathways involved in transduction of hemodynamic forces induced by blood pressure and tries to relate this information to setting of venous hypertension in varicose veins.

  17. Thermodynamics of magnesian calcite solid-solutions at 25°C and 1 atm total pressure (United States)

    Busenberg, Eurybiades; Plummer, L. Niel


    The stability of magnesian calcites was reexamined, and new results are presented for 28 natural inorganic, 12 biogenic, and 32 synthetic magnesian calcites. The magnesian calcite solid-solutions were separated into two groups on the basis of differences in stoichiometric solubility and other physical and chemical properties. Group I consists of solids of mainly metamorphic and hydrothermal origin, synthetic calcites prepared at high temperatures and pressures, and synthetic solids prepared at low temperature and very low calcite supersaturations () from artificial sea water or NaClMgCl2CaCl2solutions. Group I solids are essentially binary s of CaCO2 and MgCO2, and are thought to be relatively free of structural defects. Group II solid-solutions are of either biogenic origin or are synthetic magnesian calcites and protodolomites (0–20 and ∼ 45 mole percent MgCO3) prepared at high calcite supersaturations () from NaClNa2SO4MgCl2CaCl2 or NaClMgCl2CaCl2 solutions. Group II solid-solutions are treated as massively defective solids. The defects include substitution foreign ions (Na+ and SO42−) in the magnesian calcite lattice (point defects) and dislocations (~2 · 109 cm−2). Within each group, the excess free energy of mixing, GE, is described by the mixing model , where x is the mole fraction of the end-member Ca0.5Mg0.5CO3 in the solid-solution. The values of A0and A1 for Group I and II solids were evaluated at 25°C. The equilibrium constants of all the solids are closely described by the equation ln , where KC and KD are the equilibrium constants of calcite and Ca0.5Mg0.5CO3. Group I magnesian calcites were modeled as sub-regular solid-solutions between calcite and dolomite, and between calcite and “disordered dolomite”. Both models yield almost identical equilibrium constants for these magnesian calcites. The Group II magnesian calcites were modeled as sub-regular solid-solutions between defective calcite and

  18. Brain vein disorders in newborn infants

    NARCIS (Netherlands)

    Raets, Marlou; Dudink, Jeroen; Raybaud, Charles; Ramenghi, Luca; Lequin, Maarten; Govaert, Paul


    The brain veins of infants are in a complex phase of remodelling in the perinatal period. Magnetic resonance venography and susceptibility-weighted imaging, together with high-resolution Doppler ultrasound, have provided new tools to aid study of venous developmental anatomy and disease. This review

  19. Endovascular vein harvest: systemic carbon dioxide absorption. (United States)

    Maslow, Andrew M; Schwartz, Carl S; Bert, Arthur; Hurlburt, Peter; Gough, Jeffrey; Stearns, Gary; Singh, Arun K


    Endovascular vein harvest (EDVH) requires CO(2) insufflation to expand the subcutaneous space, allowing visualization and dissection of the saphenous vein. The purpose of this study was to assess the extent of CO(2) absorption during EDVH. Prospective observational study. Single tertiary care hospital. Sixty patients (30 EDVH and 30 open-vein harvest) undergoing isolated coronary artery bypass graft surgery. Hemodynamic, procedural, and laboratory data were collected prior to (baseline), during, and at it the conclusion (final) of vein harvesting. Data were also collected during cardiopulmonary bypass (CPB). Data were compared by using t tests, analysis of variance, and correlation statistics when needed. There were significant increases in arterial CO(2) (PaCO(2), 35%) and decreases in pH (1.35%) during EDVH. These were associated with increases in heart rate, mean blood pressure, and cardiac output. Within the EDVH group, greater elevations (>10 mmHg) in PaCO2 were more likely during difficult harvest procedures, and these patients exhibited greater increase in heart rate. Elevated CO(2) persisted during CPB, requiring higher systemic gas flows and greater use of phenylephrine to maintain desired hemodynamics. EDVH was associated with systemic absorption of CO(2). Greater absorption was more likely in difficult procedures and was associated with greater hemodynamic changes requiring medical therapy.

  20. Puzzles in practice: splenic vein thrombosis. (United States)

    McIntyre, Brittany; Marsh, Melanie; Walden, Jeffrey


    This report details a 58-year-old gentleman who presented to his outpatient primary care physician's clinic several times over four weeks for ongoing epigastric pain radiating into his left flank, dry heaving, and constipation. He was presumed to have gastritis at each visit and prescribed escalating doses of proton pump inhibitors. Due to the unrelenting pain, he eventually was admitted to the hospital and diagnosed with splenic vein thrombosis after computed tomography imaging of the abdomen. Our literature search revealed that pancreatic pathology is overwhelmingly the contributing factor to splenic vein thrombosis. Our patient had prominent collateral vasculature, suggesting that his splenic vein thrombosis was chronic in nature and likely the cause of his ongoing abdominal pain. Splenic vein thrombosis is an uncommon cause of abdominal pain, but one that should be included in the treating physician's differential diagnoses when abdominal pain is ongoing despite medical therapy. Although he had no evidence of initial findings on radiography, our patient was eventually diagnosed with biopsy-proven pancreatic cancer. Our case report demonstrates how patients presenting with persistent or worsening abdominal pain despite the use of proton pump inhibitors or other acid reducing agents and potential 'red flag' findings such as decreased appetite and weight loss should be worked up for other potential sources of abdominal pathology.


    Directory of Open Access Journals (Sweden)

    Nakhate Manisha


    Full Text Available The venous system is more complex and variable than arterial system due to its frequent anatomical variations. This paper discusses the anatomy of the great saphenous vein and its variation observed in a male cadaver of around 60 years old.


    Directory of Open Access Journals (Sweden)



    Full Text Available Retinal vein occlusion is the most common retinal occlusive disorder encountered by opthalmologists and is usually associated with a variable amount of visual loss.The study was conducted over a period of 22 months, we performed a combined analysis of risk factors, clinical presentation, management and complication of these 51 patients

  3. Risk factors of thrombosis in abdominal veins

    Institute of Scientific and Technical Information of China (English)

    Amit Kumar Durra; Ashok Chacko; Biju George; Joseph Anjilivelil Joseph; Sukesh Chandran Nair; Vikram Mathews


    AIM: To estimate the prevalence of inherited and acquired thrombophilic risk factors in patients with abdominal venous thrombosis and to compare the risk factor profiles between Budd-Chiari syndromes (BCS) and splanchnic vein thrombosis (SVT).METHODS: In this retrospective study, 36 patients with abdominal venous thrombosis were studied.The patients were divided into Budd-Chiari group (hepatic vein, IVC thrombosis) and splanchnic venous thrombosis group (portal, splenic, superior mesenteric veins) based on the veins involved. Hereditary and acquired thrombophilic risk factors were evaluated in all patients.RESULTS: Twenty patients had SVT, 14 had BCS,and 2 had mixed venous thrombosis. Ten patients (28%) had hereditary and 10 patients (28%) acquired thrombophilic risk factors. The acquired risk factors were significantly more common in the SVT group (SVT vs BCS:45% vs 7%,x2=5.7,P=0.02) while hereditary risk factors did not show significant differences between the two groups (SVT vs BCS: 25%vs 36%, x2=0.46,P=0.7). Multiple risk factors were present in one (7%) patient with BCS and in 3 patients (15%) with SVT. No risk factors were identified in 57% of patients with BCS and in 45% of patients with SVT.CONCLUSION: Hereditary and acquired risk factors play an important role in the etiopathogenesis of abdominal venous thrombosis. Acquired risk factors are significantly more common in SVT patients while hereditary factors are similar in both groups.

  4. Gene Variants Associated With Deep Vein Thrombosis

    NARCIS (Netherlands)

    Bezemer, Irene D.; Bare, Lance A.; Doggen, Carine J.M.; Arellano, Andre R.; Tong, Carmen; Rowland, Charles M.; Catanese, Joseph; Young, Bradford A.; Reitsma, Pieter H.; Devlin, James J.; Rosendaal, Frits R.


    Context The genetic causes of deep vein thrombosis (DVT) are not fully understood. Objective To identify single-nucleotide polymorphisms (SNPs) associated with DVT. Design, Setting, and Patients We used 3 case-control studies of first DVT. A total of 19 682 gene-centric SNPs were genotyped in 44

  5. Small saphenous vein: where does reflux go?

    Directory of Open Access Journals (Sweden)

    Guillermo Gustavo Rossi


    Full Text Available BACKGROUND: The anatomy of small saphenous vein (SSV is very variable because of its complex embryological origin. SSV incompetence often causes reflux that goes to the perforating veins, sometimes not respecting the anatomical course. OBJECTIVE: To analyze differences in reflux direction and reentry in the SSV. METHODS: In this prospective, observational study, 60 lower limbs with SSV incompetence of 43 patients were assessed using a color Doppler ultrasound protocol. RESULTS: Reentry variations were grouped into four types and subtypes. Percentage results were: Type A, perforating veins on the medial side = 25/60 cases (41.66%; subtypes: Cockett, Sherman, paratibial and vertex; Type B, lateral malleolus and perforating veins on the lateral side (fibular 17-26 cm = 15/60 cases (25%; subtypes: fibular and malleolus; Type C, two branches = 19/60 cases (31.66%; subtypes: gastrocnemius and Cockett, gastrocnemius and malleolus, and/or fibular, Cockett and malleolus, Cockett-vertex and fibular; Type D, reflux in the superficial system = 1/60 cases (1.66%. CONCLUSION: On most of the lower limbs assessed, reflux did not follow the classical anatomic course. Our findings demonstrated a high degree of variation in reflux/reentry, but no SSV anatomical variations. Reflux seems to, either look for the most accessible anatomical connection for reentry or be originated in the distal area and then reach the SSV.

  6. Evaluation of left renal vein entrapment using multidetector computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Poyraz, Ahmet K.; Onur, Mehmet R. [Dept. of Radiology, Firat Univ. School of Medicine, Elazig (Turkey)], e-mail:; Firdolas, Fatih [Dept. of Urology, Firat Univ. School of Medicine, Elazig (Turkey); Kocakoc, Ercan [Dept. of Radiology, Bezmialem Vakif Univ., School of Medicine, Istanbul (Turkey)


    Background: Nutcracker syndrome, also called left renal vein entrapment syndrome, is a cause of non-glomerular hematuria with difficulties in diagnosis. Multidetector computed tomography (MDCT) is a powerful tool to prevent unnecessary diagnostic procedures. Purpose: To retrospectively determine the prevalence of nutcracker phenomenon and nutcracker syndrome seen in MDCT in consecutive patients. Material and Methods: The institutional review board approved the study and waived the requirement for informed consent. Abdominal contrast-enhanced MDCT scans were reviewed from 1000 consecutive patients. MDCT scan assessment included renal vein diameter measurements and evaluation for the presence of anterior or posterior left renal vein entrapment. Electronic medical records and urine analysis reports of patients with left renal vein entrapment were reviewed. Student's t test was used to assess differences in renal vein diameter in patients with left renal vein entrapment. Results: Left renal vein entrapment was observed in 10.9% (109), retroaortic left renal vein in 6.5% (65), entrapment of left renal vein between superior mesenteric artery and aorta in 4.1% (41), and circumaortic left renal vein in 0.3% (3) of patients. Mean diameters of right (8.8 {+-} 1.9 mm) and unentrapped left (8.9 {+-} 1.8 mm) renal veins were not significantly different (P = 0.1). The mean diameter of anterior entrapped left renal veins (10.3 {+-} 2 mm) was significantly greater (P = 0.04) than contralateral renal veins (8.6 {+-} 2.1 mm) in their widest portion. In 8.8% of patients with the left renal vein entrapment, urine analysis showed isomorphic hematuria or proteinuria with no other known cause. Varicocele and pelvic congestion were seen in 5.5% of patients with the left renal vein entrapment. Conclusion: Left renal vein entrapment is not a rare entity and renal nutcracker phenomenon might be underdiagnosed.

  7. Arsenic uptake by gypsum and calcite: Modeling and probing by neutron and x-ray scattering

    CERN Document Server

    Fernandez-Martinez, Alejandro; Roman-Ross, Gabriela; Johnson, Mark R; Bardelli, Fabrizio; Turrillas, Xavier; Charlet, Laurent


    Here we report on two structural studies performed on As-doped gypsum (CaSO4 2H2O) and calcite (CaCO3), using neutron (D20-ILL) and x-ray (ID11-ESRF) diffraction data and EXAFS (BM8-ESRF). The aim of this study is to determine whether As gets into the bulk of gypsum and calcite structures or is simply adsorbed on the surface. Different mechanisms of substitution are used as hypotheses. The combined Rietveld analysis of neutron and x-ray diffraction data shows an expansion of the unit cell volume proportional to the As concentration within the samples. DFT-based simulations confirm the increase of the unit cell volume proportional to the amount of carbonate or sulphate groups substituted. Interpolation of the experimental Rietveld data allows us to distinguish As substituted within the structure from that adsorbed on the surface of both minerals.

  8. A calcite permeable reactive barrier for the remediation of Fluoride from spent potliner (SPL) contaminated groundwater

    DEFF Research Database (Denmark)

    Turner, B.D.; Binning, Philip John; Sloan, S.W.


    The use of calcite (CaCO3) as a substrate for a permeable reactive barrier (PRB) for removing fluoride from contaminated groundwater is proposed and is illustrated by application to groundwater contaminated by spent potliner leachate (SPL), a waste derived from the aluminium smelting process....... The paper focuses on two issues in the implementation of calcite permeable reactive barriers for remediating fluoride contaminated water: the impact of the groundwater chemical matrix and CO2 addition on fluoride removal. Column tests comparing pure NaF solutions, synthetic SPL solutions, and actual SPL...... leachate indicate that the complex chemical matrix of the SPL leachate can impact fluoride removal significantly. For SPL contaminant mixtures, fluoride removal is initially less than expected from idealized, pure, solutions. However, with time, the effect of other contaminants on fluoride removal...

  9. Uranium immobilization by sulfate-reducing biofilms grown on hematite, dolomite, and calcite. (United States)

    Marsili, Enrico; Beyenal, Haluk; Di Palma, Luca; Merli, Carlo; Dohnalkova, Alice; Amonette, James E; Lewandowski, Zbigniew


    Biofilms of sulfate-reducing bacteria Desulfovibrio desulfuricans G20 were used to reduce dissolved U(VI) and subsequently immobilize U(IV) in the presence of uranium-complexing carbonates. The biofilms were grown in three identically operated fixed bed reactors, filled with three types of minerals: one noncarbonate-bearing mineral (hematite) and two carbonate-bearing minerals (calcite and dolomite). The source of carbonates in the reactors filled with calcite and dolomite were the minerals, while in the reactor filled with hematite it was a 10 mM carbonate buffer, pH 7.2, which we added to the growth medium. Our five-month study demonstrated that the sulfate-reducing biofilms grown in all reactors were able to immobilize/reduce uranium efficiently, despite the presence of uranium-complexing carbonates.

  10. Deformation twinning and the role of amino acids and magnesium in calcite hardness from molecular simulation. (United States)

    Côté, A S; Darkins, R; Duffy, D M


    We employ classical molecular dynamics to calculate elastic properties and to model the nucleation and propagation of deformation twins in calcite, both as a pure crystal and with magnesium and aspartate inclusions. The twinning is induced by applying uniaxial strain to the crystal and relaxing all stress components except the uniaxial component. A detailed analysis of the atomistic processes reveal that the twinning mechanism involves small displacements of the Ca ions and cooperative rotations of the CO3 ions. The volume of the twinned region expands under increased uniaxial strain via the propagation of steps along the twin boundaries. The energy cost of the twin boundaries is compensated by the reduced hydrostatic stress and strain energy. The presence of biogenic impurities is shown to decrease the strain required to induce twin formation in calcite and, thus, the yield stress. This increased propensity for twinning provides a possible explanation for the increased hardness and penetration resistance observed experimentally in biominerals.

  11. 3D visualization of additive occlusion and tunable full-spectrum fluorescence in calcite (United States)

    Green, David C.; Ihli, Johannes; Thornton, Paul D.; Holden, Mark A.; Marzec, Bartosz; Kim, Yi-Yeoun; Kulak, Alex N.; Levenstein, Mark A.; Tang, Chiu; Lynch, Christophe; Webb, Stephen E. D.; Tynan, Christopher J.; Meldrum, Fiona C.


    From biomineralization to synthesis, organic additives provide an effective means of controlling crystallization processes. There is growing evidence that these additives are often occluded within the crystal lattice. This promises an elegant means of creating nanocomposites and tuning physical properties. Here we use the incorporation of sulfonated fluorescent dyes to gain new understanding of additive occlusion in calcite (CaCO3), and to link morphological changes to occlusion mechanisms. We demonstrate that these additives are incorporated within specific zones, as defined by the growth conditions, and show how occlusion can govern changes in crystal shape. Fluorescence spectroscopy and lifetime imaging microscopy also show that the dyes experience unique local environments within different zones. Our strategy is then extended to simultaneously incorporate mixtures of dyes, whose fluorescence cascade creates calcite nanoparticles that fluoresce white. This offers a simple strategy for generating biocompatible and stable fluorescent nanoparticles whose output can be tuned as required.

  12. Strain-relief by single dislocation loops in calcite crystals grown on self-assembled monolayers (United States)

    Ihli, Johannes; Clark, Jesse N.; Côté, Alexander S.; Kim, Yi-Yeoun; Schenk, Anna S.; Kulak, Alexander N.; Comyn, Timothy P.; Chammas, Oliver; Harder, Ross J.; Duffy, Dorothy M.; Robinson, Ian K.; Meldrum, Fiona C.


    Most of our knowledge of dislocation-mediated stress relaxation during epitaxial crystal growth comes from the study of inorganic heterostructures. Here we use Bragg coherent diffraction imaging to investigate a contrasting system, the epitaxial growth of calcite (CaCO3) crystals on organic self-assembled monolayers, where these are widely used as a model for biomineralization processes. The calcite crystals are imaged to simultaneously visualize the crystal morphology and internal strain fields. Our data reveal that each crystal possesses a single dislocation loop that occupies a common position in every crystal. The loops exhibit entirely different geometries to misfit dislocations generated in conventional epitaxial thin films and are suggested to form in response to the stress field, arising from interfacial defects and the nanoscale roughness of the substrate. This work provides unique insight into how self-assembled monolayers control the growth of inorganic crystals and demonstrates important differences as compared with inorganic substrates.

  13. Geochemistry of speleothems affected by aragonite to calcite recrystallization - Potential inheritance from the precursor mineral (United States)

    Domínguez-Villar, David; Krklec, Kristina; Pelicon, Primož; Fairchild, Ian J.; Cheng, Hai; Edwards, Lawrence R.


    Formerly aragonite speleothems recrystallized to calcite result from solutions subsaturated in aragonite and supersaturated in calcite that infiltrate into the speleothem through the interconnected porosity. In most cases, the crystal replacement takes place through a thin solution film. This diagenetic process can occur under open or semi-closed geochemical conditions. Thus, secondary calcite crystals record the composition of the fluid at the time of diagenesis affected by calcite partition coefficients and fractionation factors (open system) or partly inherit the composition of the primary aragonite (semi-closed system). So, whether or not recrystallized aragonite speleothems can record reliable geochemical signals from the time of speleothem primary deposition still is an open debate. We studied a stalagmite from Eagle Cave (Spain) predominantly composed of secondary calcite that replaced aragonite, although a core of primary aragonite extending 45 mm along the growth direction was preserved at the base of the sample. We obtained Mg and Sr compositional maps, paired U-Th dating and δ18O and δ13C profiles across the diagenetic front. Additionally, two parallel isotope records were obtained along the speleothem growth direction in the aragonite and calcite sectors. Our results support that recrystallization of this speleothem took place in open system conditions for δ18O, δ13C, Mg and Sr, but in semi-closed system conditions for U and Th. The recrystallization of this sample took place during one or several events, likely after the Younger Dryas as a result of climate change influencing drip water composition. Based on compositional zoned patterns, we suggest that the advance of diagenetic fronts in this speleothem had an average rate of 50 ± 45 μm/yr. Such recrystallization rate can transform any aragonite speleothem into calcite within a few centuries. We suggest that the volume of water interacting with the speleothem at the time of recrystallization is

  14. Selective adsorption of L- and D-amino acids on calcite: Implications for biochemical homochirality (United States)

    Hazen, R. M.; Filley, T. R.; Goodfriend, G. A.


    The emergence of biochemical homochirality was a key step in the origin of life, yet prebiotic mechanisms for chiral separation are not well constrained. Here we demonstrate a geochemically plausible scenario for chiral separation of amino acids by adsorption on mineral surfaces. Crystals of the common rock-forming mineral calcite (CaCO(3)), when immersed in a racemic aspartic acid solution, display significant adsorption and chiral selectivity of d- and l-enantiomers on pairs of mirror-related crystal-growth surfaces. This selective adsorption is greater on crystals with terraced surface textures, which indicates that d- and l-aspartic acid concentrate along step-like linear growth features. Thus, selective adsorption of linear arrays of d- and l-amino acids on calcite, with subsequent condensation polymerization, represents a plausible geochemical mechanism for the production of homochiral polypeptides on the prebiotic Earth.

  15. Calcite and dolomite in intrusive carbonatites. II. Trace-element variations (United States)

    Chakhmouradian, Anton R.; Reguir, Ekaterina P.; Couëslan, Christopher; Yang, Panseok


    The composition of calcite and dolomite from several carbonatite complexes (including a large set of petrographically diverse samples from the Aley complex in Canada) was studied by electron-microprobe analysis and laser-ablation inductively-coupled-plasma mass-spectrometry to identify the extent of substitution of rare-earth and other trace elements in these minerals and the effects of different igneous and postmagmatic processes on their composition. Analysis of the newly acquired and published data shows that the contents of rare-earth elements (REE) and certain REE ratios in magmatic calcite and dolomite are controlled by crystal fractionation of fluorapatite, monazite and, possibly, other minerals. Enrichment in REE observed in some samples (up to ~2000 ppm in calcite) cannot be accounted for by coupled substitutions involving Na, P or As. At Aley, the REE abundances and chondrite-normalized (La/Yb)cn ratios in carbonates decrease with progressive fractionation. Sequestration of heavy REE from carbonatitic magma by calcic garnet may be responsible for a steeply sloping "exponential" pattern and lowered Ce/Ce* ratios of calcite from Magnet Cove (USA) and other localities. Alternatively, the low levels of Ce and Mn in these samples could result from preferential removal of these elements by Ce4+- and Mn3+-bearing minerals (such as cerianite and spinels) at increasing f(O2) in the magma. The distribution of large-ion lithophile elements (LILE = Sr, Ba and Pb) in rock-forming carbonates also shows trends indicative of crystal fractionation effects (e.g., concomitant depletion in Ba + Pb at Aley, or Sr + Ba at Kerimasi), although the phases responsible for these variations cannot be identified unambiguously at present. Overall, element ratios sensitive to the redox state of the magma and its complexing characteristics (Eu/Eu*, Ce/Ce* and Y/Ho) are least variable and in both primary calcite and dolomite, approach the average chondritic values. In consanguineous

  16. Interaction of ethanol and water with the {1014} surface of calcite

    DEFF Research Database (Denmark)

    Cooke, David; Gray, R J; Sand, K K;


    Molecular dynamics simulations have been used to model the interaction between ethanol, water, and the {1014} surface of calcite. Our results demonstrate that a single ethanol molecule is able to form two interactions with the mineral surface (both Ca-O and O-H), resulting in a highly ordered......, stable adsorption layer. In contrast, a single water molecule can only form one or other of these interactions and is thus less well bound, resulting in a more unstable adsorption layer. Consequently, when competitive adsorption is considered, ethanol dominates the adsorption layer that forms even when...... the starting configuration consists of a complete monolayer of water at the surface. The computational results are in good agreement with the results from atomic force microscopy experiments where it is observed that a layer of ethanol remains attached to the calcite surface, decreasing its ability to interact...

  17. Functionalizing single crystals: incorporation of nanoparticles inside gel-grown calcite crystals. (United States)

    Liu, Yujing; Yuan, Wentao; Shi, Ye; Chen, Xiaoqiang; Wang, Yong; Chen, Hongzheng; Li, Hanying


    Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe3O4 nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution-grown crystals do not. As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials.

  18. Image Quality Enhancement Using the Direction and Thickness of Vein Lines for Finger-Vein Recognition


    Young Ho Park; Kang Ryoung Park


    On the basis of the increased emphasis placed on the protection of privacy, biometric recognition systems using physical or behavioural characteristics such as fingerprints, facial characteristics, iris and finger‐vein patterns or the voice have been introduced in applications including door access control, personal certification, Internet banking and ATM machines. Among these, finger‐vein recognition is advantageous in that it involves the use of inexpensive and small devices that are diffic...

  19. Adventitial cystic disease of the common femoral vein presenting as deep vein thrombosis

    Directory of Open Access Journals (Sweden)

    Young-Kyun Kim


    Full Text Available Adventitial cystic disease of the common femoral vein is a rare condition. We herein report the case of a 50-year-old woman who presented with painless swelling in her left lower leg that resembled deep vein thrombosis. She underwent femoral exploration and excision of the cystic wall. The presentation, investigation, treatment, and pathology of this condition are discussed with a literature review.

  20. Quantitative laboratory measurements of biogeochemical processes controlling biogenic calcite carbon sequestration.

    Energy Technology Data Exchange (ETDEWEB)

    Zendejas, Frank; Lane, Todd W.; Lane, Pamela D.


    The purpose of this LDRD was to generate data that could be used to populate and thereby reduce the uncertainty in global carbon cycle models. These efforts were focused on developing a system for determining the dissolution rate of biogenic calcite under oceanic pressure and temperature conditions and on carrying out a digital transcriptomic analysis of gene expression in response to changes in pCO2, and the consequent acidification of the growth medium.

  1. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    KAUST Repository

    Li, Yan Vivian


    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl2, and MgCl2) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl2 and MgCl2 solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl2 and MgCl2 solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.

  2. Identification of spectrally similar materials using the USGS Tetracorder algorithm: The calcite-epidote-chlorite problem (United States)

    Dalton, J.B.; Bove, D.J.; Mladinich, C.S.; Rockwell, B.W.


    A scheme to discriminate and identify materials having overlapping spectral absorption features has been developed and tested based on the U.S. Geological Survey (USGS) Tetracorder system. The scheme has been applied to remotely sensed imaging spectroscopy data acquired by the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) instrument. This approach was used to identify the minerals calcite, epidote, and chlorite in the upper Animas River watershed, Colorado. The study was motivated by the need to characterize the distribution of calcite in the watershed and assess its acid-neutralizing potential with regard to acidic mine drainage. Identification of these three minerals is difficult because their diagnostic spectral features are all centered at 2.3 ??m, and have similar shapes and widths. Previous studies overestimated calcite abundance as a result of these spectral overlaps. The use of a reference library containing synthetic mixtures of the three minerals in varying proportions was found to simplify the task of identifying these minerals when used in conjunction with a rule-based expert system. Some inaccuracies in the mineral distribution maps remain, however, due to the influence of a fourth spectral component, sericite, which exhibits spectral absorption features at 2.2 and 2.4 ??m that overlap the 2.3-??m absorption features of the other three minerals. Whereas the endmember minerals calcite, epidote, chlorite, and sericite can be identified by the method presented here, discrepancies occur in areas where all four occur together as intimate mixtures. It is expected that future work will be able to reduce these discrepancies by including reference mixtures containing sericite. ?? 2004 Elsevier Inc. All rights reserved.

  3. An explanation for the 18O excess in Noelaerhabdaceae coccolith calcite



    Coccoliths have dominated the sedimentary archive in the pelagic environment since the Jurassic. The biominerals produced by the coccolithophores are ideally placed to infer sea surface temperatures from their oxygen isotopic composition, as calcification in this photosynthetic algal group only occurs in the sunlit surface waters. In the present study, we dissect the isotopic mechanisms contributing to the "vital effect”, which overprints the oceanic temperatures recorded in coccolith calcite...

  4. Rapid changes in water hardness and alkalinity: Calcite formation is lethal to Daphnia magna. (United States)

    Bogart, Sarah J; Woodman, Samuel; Steinkey, Dylan; Meays, Cindy; Pyle, Greg G


    There is growing concern that freshwater ecosystems may be negatively affected by ever-increasing anthropogenic inputs of extremely hard, highly alkaline effluent containing large quantities of Ca(2+), Mg(2+), CO3(2-), and HCO3(-) ions. In this study, the toxicity of rapid and extreme shifts in water hardness (38-600mg/L as CaCO3) and alkalinity (30-420mg/L as CaCO3) to Daphnia magna was tested, both independently and in combination. Within these ranges, where no precipitation event occurred, shifts in water hardness and/or alkalinity were not toxic to D. magna. In contrast, 98-100% of D. magna died within 96h after exposure to 600mg/L as CaCO3 water hardness and 420mg/L as CaCO3 alkalinity (LT50 of 60h with a 95% CI of 54.2-66.0h). In this treatment, a CaCO3 (calcite) precipitate formed in the water column which was ingested by and thoroughly coated the D. magna. Calcite collected from a mining impacted stream contained embedded organisms, suggesting field streams may also experience similar conditions and possibly increased mortality as observed in the lab tests. Although further investigation is required to determine the exact fate of aquatic organisms exposed to rapid calcite precipitation in the field, we caution that negative effects may occur more quickly or at lower concentrations of water hardness and alkalinity in which we observed effects in D. magna, because some species, such as aquatic insects, are more sensitive than cladocerans to changes in ionic strength. Our results provide evidence that both calcite precipitation and the major ion balance of waters should be managed in industrially affected ecosystems and we support the development of a hardness+alkalinity guideline for the protection of aquatic life.

  5. Higher Order Elastic Constants, Gruneisen Parameters and Lattice Thermal Expansion of Trigonal Calcite


    Thresiamma Phlip; Menon, C S; Indulekha, K.


    The second- and third-order elastic constants of trigonal calcite have been obtained using the deformation theory. The strain energy density derived using the deformation theory is compared with the strain dependent lattice energy obtained from the elastic continuum model approximation to get the expressions for the second- and third-order elastic constants. Higher order elastic constants are a measure of the anharmonicity of a crystal lattice. The seven second-order elastic constants and the...

  6. Heteroepitaxial growth of cadmium carbonate at dolomite and calcite surfaces: Mechanisms and rates (United States)

    Callagon, Erika Blanca R.; Lee, Sang Soo; Eng, Peter J.; Laanait, Nouamane; Sturchio, Neil C.; Nagy, Kathryn L.; Fenter, Paul


    The systematic variation of rates and the mechanism of cadmium uptake on the (1 0 4) surface of dolomite (CaMg(CO3)2) were investigated using in situ and ex situ atomic force microscopy (AFM), ex situ specular X-ray reflectivity (XR), and ex situ X-ray fluorescence (XRF). Selected experiments were performed on the calcite (CaCO3) (1 0 4) surface for comparison. Aqueous solutions of CdCl2, CaCl2, and NaHCO3, undersaturated with respect to calcite and supersaturated with respect to otavite (CdCO3) and the (CdxCa1-x)CO3 solid solution, were reacted with dolomite surfaces for minutes to days. Calcite substrates were reacted with solutions containing 1-50 μM CdCl2, and with no added Ca or CO3. Thin carbonate films following the Stranski-Krastanov growth mode were observed on both substrates. Specular XR and XRF revealed the formation of nm-thick Cd-rich carbonate films that were structurally ordered with respect to the dolomite (1 0 4) plane. Epitaxial films adopted the calcite crystal structure with a d104-spacing (3.00 Å) larger than those of pure dolomite (2.88 Å) and otavite (2.95 Å) indicating either a solid solution with x ≈ 0.5, or a strained Cd-rich carbonate with a composition near that of otavite. The growth rate r of this phase increases with the initial supersaturation of the solution with respect to the solid solution, βmax , and follows the empirical relationship, as determined from XRF measurements, given by:

  7. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate. (United States)

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C


    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product.

  8. Microcracking in calcite and dolomite marble: microstructural influences and effects on properties


    Shushakova, Victoria; Fuller, Edwin; Siegesmund, Siegfried


    Microstructure‐based finite-element analysis with a microcracking algorithm was used to simulate an actual degradation phenomenon of marble structures, i.e., microcracking. Both microcrack initiation and crack propagation were characterized, as were their dependence on lattice preferred orientation (LPO), grain shape preferred orientation (SPO), grain size, marble composition (calcite and dolomite) and grain‐boundary fracture toughness. Two LPOs were analyzed: a random orientation distributio...

  9. Shock Waves Trigger Fault Weakening in Calcite-bearing Rocks During Earthquakes (United States)

    Spagnuolo, E.; Plumper, O.; Violay, M.; Cavallo, A.; Di Toro, G.


    The weakening mechanism of calcite-bearing rocks is still poorly understood though many major earthquakes stroke within carbonate sequences. Insights derive from the laboratory: in experiments performed on calcite-bearing gouges, up to 90% drop in friction is associated to grain size reduction to the nanoscale and the formation of crystal-plastic microstructures suggesting the activation of debated weakening mechanisms (e.g., grain boundary sliding and diffusion creep; nanopowder lubrication). Whatever the case, it is unclear how nanoparticles form and what their role is at the initiation of sliding. To investigate initial fault instability we sheared with a rotary shear apparatus SHIVA pre-cut ring-shaped solid cylinders (50/30 mm ext/int diameter) of Carrara marble (99.9% CaCO3). Rock cylinders were slid for few millimetres(0, 1.5 mm and 5mm) at accelerations (6.5 ms-2) and normal stresses (10 MPa) approaching seismic deformation conditions. Initial slip (nano-fracturing have occurred preserving the grain shape (pulverization) and (3) reaction products attributable to high pressure and high temperature conditions (i.e. calcite decomposition into amorphous carbon rimming the nanograins). All the above features are typical of shock-induced changes in minerals. We interpret the above observations as follows: pre-existing grain boundaries or newly formed defects are the nuclei for the generation of dislocations and for their pile-up; the fast release of those piles-up in avalanches under rapid stress loading (fast moving dislocations) may explain the origin of such a shock-like behaviour responsible for large initial frictional weakening. The passage of the shock wave induces pervasive nanofracturing with grain size reduction to the nano-scale and an abrupt temperature rise responsible for calcite decarbonation and formation of carbon amorphous material.

  10. Successful correction of unroofed coronary sinus with pulmonary vein stenosis. (United States)

    Li, Yang; An, Qi; Zhang, Eryong


    We present a case of an infant with an unroofed coronary sinus associated with a persistent left superior vena cava draining into the left atrium, right superior pulmonary vein stenosis, an atretic left superior pulmonary vein and a double-outlet right ventricle. For pulmonary vein stenosis and atresia, we used a sutureless technique with an autologous pericardial patch to create a neoatrium.

  11. Nanobacteria-like calcite single crystals at the surface of the Tataouine meteorite. (United States)

    Benzerara, Karim; Menguy, Nicolas; Guyot, Francois; Dominici, Christian; Gillet, Philippe


    Nanobacteria-like objects evidenced at the surface of the orthopyroxenes of the Tataouine meteorite in South Tunisia have been studied by scanning and transmission electron microscopies. A method of micromanipulation has been developed to ensure that exactly the same objects were studied by both methods. We have shown that the nanobacteria-like objects are spatially correlated with filaments of microorganisms that colonized the surface of the meteoritic pyroxene during its 70 years of residence in the aridic Tataouine soil. Depressions of a few micrometers in depth are observed in the pyroxene below the carbonates, indicating preferential dissolution of the pyroxene and calcite precipitation at these locations. The nanobacteria-like small rods that constitute calcium carbonate rosettes are well crystallized calcite single crystals surrounded by a thin amorphous layer of carbonate composition that smoothes the crystal edges and induces rounded shapes. Those morphologies are unusual for calcite single crystals observed in natural samples. A survey of recent literature suggests that the intervention of organic compounds derived from biological activity is likely in their formation.

  12. Metal:Calcite Distribution Coefficients of Laboratory-Grown Bathyl Benthic Foraminifera (United States)

    Hintz, C. J.; Shaw, T. J.; Bernhard, J. M.; Chandler, G. T.; McCorkle, D. C.; Blanks, J. K.


    Benthic foraminifera, collected from sediments off the Carolina coast, were maintained in mono- and multi-species cultures for four and a half months in a sediment-free culture system. The foraminifera were cultured in a closed system using a 1600-liter modified artificial seawater reservoir. The temperature, alkalinity, stable isotope ratios, and trace metal concentrations were held static in seawater medium during the experiment. The artificial seawater was circulated from the reservoir through nine 3 mL acrylic microcosms that contained 80-100 foraminifera living in ~1 mm thick silica substrate. Foraminifera were labeled with fluorescent calcein, prior to addition to the microcosms, to provide a clear demarcation between parent calcite and cultured calcite. At the end of the experiment juvenile Bulimina aculeata were harvested from the microcosms (~150-3000 specimens per microcosm). The cultured foraminifera were divided into two groups for separate trace metal analyses and stable isotope analyses. The foraminifera from the trace metal splits were cleaned and analyzed for Ca, Ba, and Cd by isotope dilution ICP-MS. Barium distribution coefficients were close to previously reported values of cultured foraminiferal calcite but remained lower than reported field data. Preliminary Ba:Ca distribution coefficients for B. aculeata do not appear to indicate strong life stage differences, even though there are indications of ontogenetic variations in δ13C for this species (see McCorkle et al. abstract).

  13. Existence and release of fluid inclusions in bornite and its associated quartz and calcite (United States)

    Deng, Jiu-shuai; Wen, Shu-ming; Wu, Dan-dan; Liu, Jian; Zhang, Xiao-lin; Shen, Hai-ying


    The existence and release of fluid inclusions in bornite and its associated minerals, namely, quartz and calcite were investigated and confirmed. The structures, forms, and phases of these large quantities of fluid inclusions were also studied. A mass of fluid inclusions with various sizes, distributions, shapes, and phases exist in bornite and its associated minerals. Their sizes vary from a few micrometers to tens of micrometers, and the forms appear as negative crystals, or elongated, elliptical, and irregular. At room temperature, fluid inclusions were mainly characterized as gas-liquid twophase. However, small amounts of fluid inclusions with pure gas phase and pure liquid single-phase were also observed in quartz and calcite. These fluid inclusions initially broke during the ore crushing and grinding process and then released into the flotation pulp in the flotation process. The quantitative analysis of fluid inclusions in the solution and the comparisons of mineral dissolution show that the amount of copper and iron released by fluid inclusions in the bornite sample is higher than the amount dissolved by the mineral; fluid inclusions in the associated gangue minerals, quartz, and calcite also make contribution.

  14. Biomineralization processes of calcite induced by bacteria isolated from marine sediments

    Directory of Open Access Journals (Sweden)

    Shiping Wei


    Full Text Available Biomineralization is a known natural phenomenon associated with a wide range of bacterial species. Bacterial-induced calcium carbonate precipitation by marine isolates was investigated in this study. Three genera of ureolytic bacteria, Sporosarcina sp., Bacillus sp. and Brevundimonas sp. were observed to precipitate calcium carbonate minerals. Of these species, Sporosarcina sp. dominated the cultured isolates. B. lentus CP28 generated higher urease activity and facilitated more efficient precipitation of calcium carbonate at 3.24 ± 0.25 × 10−4 mg/cell. X-ray diffraction indicated that the dominant calcium carbonate phase was calcite. Scanning electron microscopy showed that morphologies of the minerals were dominated by cubic, rhombic and polygonal plate-like crystals. The dynamic process of microbial calcium carbonate precipitation revealed that B. lentus CP28 precipitated calcite crystals through the enzymatic hydrolysis of urea, and that when ammonium ion concentrations reached 746 mM and the pH reached 9.6, that favored calcite precipitation at a higher level of 96 mg/L. The results of this research provide evidence that a variety of marine bacteria can induce calcium carbonate precipitation, and may influence the marine carbonate cycle in natural environments.

  15. Intermediate-scale tests of sodium interactions with calcite and dolomite aggregate concretes. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Randich, E.; Acton, R.U.


    Two intermediate-scale tests were performed to compare the behavior of calcite and dolomite aggregate concretes when attacked by molten sodium. The tests were performed as part of an interlaboratory comparison between Sandia National Laboratories and Hanford Engineering Development Laboratories. Results of the tests at Sandia National Laboratories are reported here. The results show that both concretes exhibit similar exothermic reactions with molten sodium. The large difference in reaction vigor suggested by thermodynamic considerations of CO/sub 2/ release from calcite and dolomite was not realized. Penetration rates of 1.4 to 1.7 mm/min were observed for short periods of time with reaction zone temperatures in excess of 800/sup 0/C during the energetic attack. The penetration was not uniform over the entire sodium-concrete contact area. Rapid attack may be localized due to inhomogeneities in the concrete. The chemical reaction zone is less then one cm thick for the calcite concrete but is about seven cm thick for the dolomite concrete.

  16. Numerical Simulations of Urea Hydrolysis and Calcite Precipitation in Porous Media Using STOMP

    Energy Technology Data Exchange (ETDEWEB)

    Luanjing Guo; Hai Huang; Bill X. Hu


    Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising in situ immobilization approach of these contaminants is engineered mineral (co)precipitation of calcite driven by urea hydrolysis that is catalyzed by enzyme urease. The tight nonlinear coupling among flow, transport, reaction and reaction-induced property changes of media of this approach was studied by reactive transport simulations with systematically increasing level of complexities of reaction network and physical/chemical heterogeneities using a numerical simulator named STOMP. Sensitivity studies on the reaction rates of both urea hydrolysis and calcite precipitation are performed via controlling urease enzyme concentration and precipitation rate constant according to the rate models employed. We have found that the rate of ureolysis is a dominating factor in the amount of precipitated mineral; however, the spatial distribution of the precipitates depends on both rates of ureolysis and calcite precipitation. A maximum 5% reduction in the porosity was observed within the simulation time period of 6 pore volumes in our 1-dimensional (1D) column simulations. When a low permeability inclusion is considered in the 2D simulations, the altered flow fields redistribute mineral forming constituents, leading to a distorted precipitation reaction front. The simulations also indicate that mineral precipitation occurs along the boundary of the low permeability zone, which implies that contaminants in the low permeability zone could be encapsulated and isolated from the flow paths.

  17. Morphogenetic control of calcite crystal growth in sulfonic acid based hydrogels. (United States)

    Grassmann, Olaf; Löbmann, Peer


    In this paper the mineralization of CaCO(3) in various hydrogel matrices is presented. Sulfonic acid based hydrogels were prepared by introduction of sulfonate-containing monomers into a polyacrylamide network. The sulfonate content of polyacrylamide-co-vinylsulfonate and polyacrylamide-co-allylsulfonate decreases during elution of the copolymers in demineralized water, indicating insufficient linking of the sulfonate-bearing monomers within the hydrogel. In contrast to this, acrylamidomethylpropanesulfonate (AMPS) effectively copolymerizes with acrylamide (AAm) monomers. To study the influence of spatial arrangement of ionic functional groups within hydrogel networks on the mineralization of CaCO(3), AMPS copolymers with different degrees of AMPS cross-linking were synthesized. For the mineralization experiments the copolymers were placed into a double-diffusion arrangement. Calcite as the thermodynamically stable modification of CaCO(3) was obtained with a particular morphology. The pseudocubic habitus resembles aggregates obtained by mineralization in pure polyacrylamide. However, closer examination of the aggregates by scanning electron microscopy (SEM) shows that the crystal growth in the AMPS copolymers is different from that observed in polyacrylamide. Whereas the morphology of the calcite aggregates could be fine-tuned by using copolymers with different sulfonate content, the spatial distribution of the ionic functional groups alters the course of crystallization. Calcium ions are locally accumulated due to the heterogeneous distribution of functional sulfonate groups within the copolymer network. Thereby the nucleation of calcite is triggered, resulting in enhanced mineralization.

  18. Sulfur in foraminiferal calcite as a potential proxy for seawater carbonate ion concentration (United States)

    van Dijk, I.; de Nooijer, L. J.; Boer, W.; Reichart, G.-J.


    Sulfur (S) incorporation in foraminiferal shells is hypothesized to change with carbonate ion concentration [CO32-], due to substitution of sulfate for carbonate ions in the calcite crystal lattice. Hence S/Ca values of foraminiferal carbonate shells are expected to reflect sea water carbonate chemistry. To generate a proxy calibration linking the incorporation of S into foraminiferal calcite to carbonate chemistry, we cultured juvenile clones of the larger benthic species Amphistegina gibbosa and Sorites marginalis over a 350-1200 ppm range of pCO2 values, corresponding to a range in [CO32-] of 93 to 211 μmol/kg. We also investigated the potential effect of salinity on S incorporation by culturing juvenile Amphistegina lessonii over a large salinity gradient (25-45). Results show S/CaCALCITE is not impacted by salinity, but increases with increasing pCO2 (and thus decreasing [CO32-] and pH), indicating S incorporation may be used as a proxy for [CO32-]. Higher S incorporation in high-Mg species S. marginalis suggests a superimposed biomineralization effect on the incorporation of S. Microprobe imaging reveals co-occurring banding of Mg and S in Amphistegina lessonii, which is in line with a strong biological control and might explain higher S incorporation in high Mg species. Provided a species-specific calibration is available, foraminiferal S/Ca values might add a valuable new tool for reconstructing past ocean carbonate chemistry.

  19. Microstructural Characterization of Calcite-Based Powder Materials Prepared by Planetary Ball Milling

    Directory of Open Access Journals (Sweden)

    Wen-Tien Tsai


    Full Text Available In this work, a planetary ball milling was used to modify the surface properties of calcite-based material from waste oyster shell under the rotational speed of 200–600 rpm, grinding time of 5–180 min and sample mass of 1–10 g. The milling significantly changed the microstructural properties of the calcite-based minerals (i.e., surface area, pore volume, true density, and porosity. The surface characterization of the resulting powder should be macroporous and/or nonporous based on the nitrogen adsorption/desorption isotherms. Under the optimal conditions at the rotational speed of 400 rpm, grinding time of 30 min and sample mass of 5 g, the resulting calcite-based powder had larger specific surface area (i.e., 10.64 m2·g−1 than the starting material (i.e., 4.05 m2·g−1. This finding was also consistent with the measurement of laser-diffraction (i.e., 9.7 vs. 15.0 μm of mean diameter. In addition, the results from the scanning electron microscope (SEM observation indicated that surface roughness can be enhanced as particle size decreases as a result of particle-particle attrition. Thus, grinding the aquacultural bioresource by a high-energy ball milling can create the fine materials, which may be applied in the fields of inorganic minerals like aggregate and construction material.

  20. Biomineralization processes of calcite induced by bacteria isolated from marine sediments. (United States)

    Wei, Shiping; Cui, Hongpeng; Jiang, Zhenglong; Liu, Hao; He, Hao; Fang, Nianqiao


    Biomineralization is a known natural phenomenon associated with a wide range of bacterial species. Bacterial-induced calcium carbonate precipitation by marine isolates was investigated in this study. Three genera of ureolytic bacteria, Sporosarcina sp., Bacillus sp. and Brevundimonas sp. were observed to precipitate calcium carbonate minerals. Of these species, Sporosarcina sp. dominated the cultured isolates. B. lentus CP28 generated higher urease activity and facilitated more efficient precipitation of calcium carbonate at 3.24 ± 0.25 × 10(-4) mg/cell. X-ray diffraction indicated that the dominant calcium carbonate phase was calcite. Scanning electron microscopy showed that morphologies of the minerals were dominated by cubic, rhombic and polygonal plate-like crystals. The dynamic process of microbial calcium carbonate precipitation revealed that B. lentus CP28 precipitated calcite crystals through the enzymatic hydrolysis of urea, and that when ammonium ion concentrations reached 746 mM and the pH reached 9.6, that favored calcite precipitation at a higher level of 96 mg/L. The results of this research provide evidence that a variety of marine bacteria can induce calcium carbonate precipitation, and may influence the marine carbonate cycle in natural environments.

  1. Effects of limestone petrography and calcite microstructure on OPC clinker raw meals burnability (United States)

    Galimberti, Matteo; Marinoni, Nicoletta; Della Porta, Giovanna; Marchi, Maurizio; Dapiaggi, Monica


    Limestone represents the main raw material for ordinary Portland cement clinker production. In this study eight natural limestones from different geological environments were chosen to prepare raw meals for clinker manufacturing, aiming to define a parameter controlling the burnability. First, limestones were characterized by X-Ray Fluorescence, X-Ray Powder Diffraction and Optical Microscopy to assess their suitability for clinker production and their petrographic features. The average domains size and the microstrain of calcite were also determined by X-Ray Powder Diffraction line profile analysis. Then, each limestone was admixed with clay minerals to achieve the adequate chemical composition for clinker production. Raw meals were thermally threated at seven different temperatures, from 1000 to 1450 °C, to evaluate their behaviour on heating by ex situ X-Ray Powder Diffraction and to observe the final clinker morphology by Scanning Electron Microscopy. Results indicate the calcite microstrain is a reliable parameter to predict the burnability of the raw meals, in terms of calcium silicates growth and lime consumption. In particular, mixtures prepared starting from high-strained calcite exhibit a better burnability. Later, when the melt appears this correlation vanishes; however differences in the early burnability still reflect on the final clinker composition and texture.

  2. Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template. (United States)

    Xue, Zhonghui; Hu, Binbin; Dai, Shuxi; Du, Zuliang


    Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10 mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6 h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12 h and 24 h, via "copying" the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants.

  3. Effect of Solute Impurity of Mg on the Microstructure of Calcite (United States)

    Xu, L.; Evans, B. J.; Renner, J.


    We produced synthetic marbles by hot isostatic pressing (HIPing) mixtures of calcite and dolomite powders for different intervals (2 to 30 hrs) at 850°C and 300 MPa confining pressure. The HIP treatment resulted in macroscopically homogeneous calcite aggregates with Mg content ranging from 0.5 to 17 mol%. We performed creep tests on samples after HIP at differential stresses from ~ 20 to 170 MPa using constant strain rate and stress-stepping method. Microstructure of both HIPed and deformed samples were studied using both scanning electron microscope (SEM) and transmitted electron microscope (TEM). Both back- scattered electron images and chemical analysis using ion probe suggested that the dolomite phase is completely dissolved, and that the Mg distribution is homogeneous throughout the samples at a scale of a few microns. Grain sizes increase with HIP time and decrease with increasing Mg content (> 3.0 mol%). The growth exponent varies from 2.7 to 3.5 for samples containing 0.3 to 17.0 mol% Mg. Some HIPed samples have intragranular spherical pores, but the shape of the grain boundaries indicates pore drag. At stresses above 80 MPa, the stress sensitivity of strain, n, is greater than 3, indicating an increasing contribution of dislocation creep. The strength of calcite increases with the Mg content in the dislocation creep regime, but not when the rocks deform by diffusion creep. In some deformed samples (ɛ ~ 0.25), a bimodal distribution of large protoblasts and small recrystallized neoblasts coexisted..

  4. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface (United States)

    Ylikantola, A.; Linnanto, J.; Knuutinen, J.; Oravilahti, A.; Toivakka, M.


    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree-Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree-Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree-Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  5. Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades (United States)

    Hoch, A.R.; Reddy, M.M.; Aiken, G.R.


    The crystallization of calcium carbonate minerals plays an integral role in the water chemistry of terrestrial ecosystems. Humic substances, which are ubiquitous in natural waters, have been shown to reduce or inhibit calcite crystal growth in experiments. The purpose of this study is to quantify and understand the kinetic effects of hydrophobic organic acids isolated from the Florida Everglades and a fulvic acid from Lake Fryxell, Antarctica, on the crystal growth of calcite (CaCO3). Highly reproducible calcite growth experiments were performed in a sealed reactor at constant pH, temperature, supersaturation (?? = 4.5), P(CO2) (10-3.5atm), and ionic strength (0.1 M) with various concentrations of organic acids. Higher plant-derived aquatic hydrophobic acids from the Everglades were more effective growth inhibitors than microbially derived fulvic acid from Lake Fryxell. Organic acid aromaticity correlated strongly with growth inhibition. Molecular weight and heteroatom content correlated well with growth inhibition, whereas carboxyl content and aliphatic nature did not. Copyright (C) 1999 Elsevier Science Ltd.

  6. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface

    Energy Technology Data Exchange (ETDEWEB)

    Ylikantola, A. [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); Linnanto, J., E-mail: [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); University of Tartu, Institute of Physics, Riia 142, EE-51014 Tartu (Estonia); Knuutinen, J.; Oravilahti, A. [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); Toivakka, M. [Åbo Akademi University, Laboratory of Paper Coating and Converting and Center for Functional Materials, FI-20500 Turku/Åbo (Finland)


    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree–Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree–Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree–Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  7. Adsorption of arsenic and phosphate onto the surface of calcite as revealed by batch experiments and surface complexation modelling

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt

    The adsorption of phosphate, arsenate (As(V)) and arsenite (As(III)) onto synthetic calcite was studied in a series of batch experiments. The adsorption of the three ions was studied separately followed by studies of the competition between arsenate and phosphate. The experimental data was utilized...... is complete after 1 and 2-3 hours, respectively). Also desorption is fast and complete for both ions within 0.5 h. The reversibility of the sorption process indicates that neither arsenate nor phosphate is readily incorporated into the calcite crystal lattice under our experimental conditions. The phosphate....... This clearly shows the importance of competition studies in validating multicomponent models. Extrapolation of the experimental results to calcite bearing aquifers suggests a large variability in the mobility of arsenic. Under reduced conditions, arsenite, which does not adsorb onto calcite, will dominate and...

  8. Primary varicose veins: Frequency, clinical significance and surgical treatment

    Directory of Open Access Journals (Sweden)

    Vasić Dragan M.


    Full Text Available INTRODUCTION According to the definition of the World Health Organization, varicose veins represent abnormally enlarged superficial veins having baggy or cylindrical shape. The most frequent cause of primary varicose veins is the insufficiency of long saphenous vein (LSV, but especially the basin of its connection with femoral vein and perforating veins. OBJECTIVE The objectives of these investigations were: the determination of insufficiency incidence of SSV in cases of LSV insufficiency; the establishment of association of insufficiency of perforating veins of the basin of LSV and SSV; the study of the results of surgical treatment of insufficiency and varicosity of both short and long saphenous veins. METHODS In this study, 100 patients (66 women and 34 men, average age 52.1 years, with clinical symptoms showing the insufficiency and varicosity of long saphenous vein with no change of deep vein system were examined. Ultrasonographic examinations were made using Color Doppler probes - 7.5 and 3.75 MHz (Toshiba Corevison SSA 350 A; the development of incompetence of long saphenous vein (LSV and short saphenous vein (SSV at the level of the junction as well as other incompetent valves were examined. The reflux was defined as a retrograde flow of the duration longer than 0.5 seconds. RESULTS The insufficiency of short saphenous vein was determined by ultrasonographic examination in 34%, while the insufficiency of perforating veins in 80% of patients. 40% of patients were operated (33.3% of females, and 52.9% of males. The most frequent indications for surgical treatment of superficial veins insufficiency were: strong varicosities, clear symptoms and signs, superficial thrombophlebitis and conditions after superficial thrombophlebitis. Surgical treatment was applied in 16% of patients due to recurrence in the basin of long saphenous vein, and in 6% of cases because of the recurrence in the basin of short saphenous vein. Data analysis failed to

  9. [Pelvic vein thrombosis with elevated D-dimer level and normal ultrasound scan of the femoral vein]. (United States)

    Stenberg, Morten Roos; Tveskov, Claus


    A 17-year-old female presented with an isolated pelvic vein thrombosis (PVT) which was not visualised at the first compression ultrasound scan of the femoral vein. Isolated PVT should be suspected when the patient demonstrates the possible symptoms of a deep vein thrombosis with unilateral leg swelling extending to the groin and a negative compression ultrasound scan of the femoral vein. Supplemental ultrasound scan with Doppler flow, computed tomography or magnetic resonance venography are alternative diagnostic modalities if PVT is suspected.

  10. Treatment of recurrent varicose veins of the great saphenous vein by conventional surgery and endovenous laser ablation.

    NARCIS (Netherlands)

    Groenendael, L. van; Vliet, J.A. van der; Flinkenflogel, L.; Roovers, E.A.; Sterkenburg, S.M. van; Reijnen, M.M.P.J.


    OBJECTIVE: Varicose vein recurrence of the great saphenous vein (GSV) is a common, costly, and complex problem. The aim of the study was to assess feasibility of endovenous laser ablation (EVLA) in recurrent varicose veins of the GSV and to compare this technique with conventional surgical reinterve

  11. A simplified methodology to approach the complexity of foraminiferal calcite oxygen-isotope data - model comparison (United States)

    Roche, Didier; Waelbroeck, Claire


    Since the pioneering work of Epstein (Epstein et al., 1953), numerous calcite isotopic records from the ocean have been used to attempt reconstructing paleoclimatic information. Additional to the well known complexity brought by the fact that foraminiferal calcite records both temperature and isotopic composition of the surrounding oceanic waters, an additional effect for surface - dwelling foraminifers is the fact that two different species do not have the same habitat and may thus record different signals. This is obvious when comparing paleoclimatic records where different species have been measured for the isotopic composition of the calcite. The difference in habitat produces a three dimensional spatial complexity (a foraminifera living in preferred climatic conditions at a specific location, but also at a specific depth, sometimes far from the surface) but also a temporal uncertainty (foraminifers generally live for only a few weeks and their growth season may be evolving through time with climate change). While the different species habitats potentially contain a wealth of information that could be used to better understand the sequences of climate change, this has seldom been used in modeling studies, most models deriving calcite isotopic signal from surface and annual mean conditions (e.g. Roche et al., 2014). In the present work, we propose a reduced complexity approach to compute the calcite for several planktonic foraminifers from climate model simulations under pre-industrial conditions. We base our approach on simple functions describing the temperature dependence of the different species growth rates (Lombard et al., 2009) and on probability of presence based on the physical variables computed in the climate model. We present a comparison to available sediment traps and core tops data as a validation of the methodology, focusing on the possibility for future applicability towards inversion of the signal measured in oceanic sediment cores. References

  12. Calcite precipitation on glass substrates and active stalagmites in Katerloch Cave (Austria): Constraints from environmental monitoring (United States)

    Sakoparnig, Marlene; Boch, Ronny; Wang, Xianfeng; Lin, Ke; Spötl, Christoph; Leis, Albrecht; Gollowitsch, Anna; Dietzel, Martin


    Located near Graz at the SE-rim of the Alps Katerloch is well-known for its impressive dripstone decoration, e.g. several metres tall and relatively fast growing (0.2-0.7 mm/yr on average) candle-stick-type stalagmites. In the course of an ongoing multi-annual and partially high-resolution cave monitoring program we study modern (active) sites of carbonate deposition focusing on the site-specific growth dynamics and connection of modern regional and cave environmental conditions with petrographic, chemical and stable isotopic information captured in the speleothems. Fresh calcite precipitates on artificial (glass) substrates underneath active drip sites were collected continuously from 2006 to 2014 (eight years!). The samples (up to 7 mm thick) represent cave sections of different temperature and drip sites of partially different characteristics (e.g. drip rate). We also recovered short drill cores (up to 3 cm length, 1 cm diameter) from the top of active stalagmites probably representing the last decades to centuries of calcite crystallization. Moreover, an actively growing stalagmite (K10) comprising both modern and past calcite deposition was collected. 238U-234U-230Th dating using MC-ICP-MS of K10 (71 cm long) revealed several distinct growth intervals (separated by growth interruptions) starting at 129.1 ±1.2 kyr BP (Last Interglacial) up to now, mostly reflecting warm and humid climate intervals. High-resolution (100 μm) isotope profiles micromilled from the multi-annual modern calcite precipitates on artificial substrates revealed low δ13C values of -12.8 to -8.3 ‰ (VPDB) and relatively high δ18O of -6.9 to -4.9 ‰Ṫhe δ18O curves from all collection sites (different growth rate) record a pronounced decrease during their most recent growth period most likely corresponding to a significant decrease towards lower oxygen isotope values observed in drip waters collected in the year 2014 compared with samples from 2005 to 2007. Drip water δ2H /δ18O

  13. Clumped isotope thermometry of calcite and dolomite in a contact metamorphic environment (United States)

    Lloyd, Max K.; Eiler, John M.; Nabelek, Peter I.


    Clumped isotope compositions of slowly-cooled calcite and dolomite marbles record apparent equilibrium temperatures of roughly 150-200 °C and 300-350 °C, respectively. Because clumped isotope compositions are sensitive to the details of T-t path within these intervals, measurements of the Δ47 values of coexisting calcite and dolomite can place new constraints on thermal history of low-grade metamorphic rocks over a large portion of the upper crust (from ∼5 to ∼15 km depth). We studied the clumped isotope geochemistry of coexisting calcite and dolomite in marbles from the Notch Peak contact metamorphic aureole, Utah. Here, flat-lying limestones were intruded by a pluton, producing a regular, zoned metamorphic aureole. Calcite Δ47 temperatures are uniform, 156 ± 12 °C (2σ s.e.), across rocks varying from high-grade marbles that exceeded 500 °C to nominally unmetamorphosed limestones >5 km from the intrusion. This result appears to require that the temperature far from the pluton was close to this value; an ambient temperature just 20 °C lower would not have permitted substantial re-equilibration, and should have preserved depositional or early diagenetic Δ47 values several km from the pluton. Combining this result with depth constraints from overlying strata suggests the country rock here had an average regional geotherm of 22.3-27.4 °C/km from the late Jurassic Period until at least the middle Paleogene Period. Dolomite Δ47 in all samples above the talc + tremolite-in isograd record apparent equilibrium temperatures of 328-12+13 °C (1σ s.e.), consistent with the apparent equilibrium blocking temperature we expect for cooling from peak metamorphic conditions. At greater distances, dolomite Δ47 records temperatures of peak (anchi)metamorphism or pre-metamorphic diagenetic conditions. The interface between these domains is the location of the 330 °C isotherm associated with intrusion. Multiple-phase clumped isotope measurements are complemented by

  14. An assessment of calcite crystal growth mechanisms based on crystal size distributions (United States)

    Kile, D.E.; Eberl, D.D.; Hoch, A.R.; Reddy, M.M.


    Calcite crystal growth experiments were undertaken to test a recently proposed model that relates crystal growth mechanisms to the shapes of crystal size distributions (CSDs). According to this approach, CSDs for minerals have three basic shapes: (1) asymptotic, which is related to a crystal growth mechanism having constant-rate nucleation accompanied by surface-controlled growth; (2) lognormal, which results from decaying-rate nucleation accompanied by surface-controlled growth; and (3) a theoretical, universal, steady-state curve attributed to Ostwald ripening. In addition, there is a fourth crystal growth mechanism that does not have a specific CSD shape, but which preserves the relative shapes of previously formed CSDs. This mechanism is attributed to supply-controlled growth. All three shapes were produced experimentally in the calcite growth experiments by modifying nucleation conditions and solution concentrations. The asymptotic CSD formed when additional reactants were added stepwise to the surface of solutions that were supersaturated with respect to calcite (initial Ω = 20, where Ω = 1 represents saturation), thereby leading to the continuous nucleation and growth of calcite crystals. Lognormal CSDs resulted when reactants were added continuously below the solution surface, via a submerged tube, to similarly supersaturated solutions (initial Ω = 22 to 41), thereby leading to a single nucleation event followed by surface-controlled growth. The Ostwald CSD resulted when concentrated reactants were rapidly mixed, leading initially to high levels of supersaturation (Ω >100), and to the formation and subsequent dissolution of very small nuclei, thereby yielding CSDs having small crystal size variances. The three CSD shapes likely were produced early in the crystallization process, in the nanometer crystal size range, and preserved during subsequent growth. Preservation of the relative shapes of the CSDs indicates that a supply-controlled growth mechanism

  15. Primary leiomyosarcoma of saphenous vein presenting as deep venous thrombosis. (United States)

    Fremed, Daniel I; Faries, Peter L; Schanzer, Harry R; Marin, Michael L; Ting, Windsor


    Only a small number of venous leiomyosarcomas have been previously reported. Of these tumors, those of saphenous origin comprise a minority of cases. A 59-year-old man presented with symptoms of deep vein thrombosis and was eventually diagnosed with primary leiomyosarcoma of great saphenous vein origin. The tumor was treated with primary resection and femoral vein reconstruction with autologous patch. Although extremely rare, saphenous leiomyosarcoma can present as deep vein thrombosis. Vascular tumors should be included in the differential diagnosis of atypical extremity swelling refractory to conventional deep vein thrombosis management.

  16. Calcite as a bone substitute. Comparison with hydroxyapatite and tricalcium phosphate with regard to the osteoblastic activity

    Energy Technology Data Exchange (ETDEWEB)

    Monchau, F., E-mail: [Laboratoire Genie Civil et geo-Environnement (EA 4515, Universite Lille Nord de France), Equipe Biomateriaux Artois (Universite d' Artois), IUT/GMP, 1230, rue de l' Universite, BP 819, 62408 Bethune cedex (France); Hivart, Ph.; Genestie, B. [Laboratoire Genie Civil et geo-Environnement (EA 4515, Universite Lille Nord de France), Equipe Biomateriaux Artois (Universite d' Artois), IUT/GMP, 1230, rue de l' Universite, BP 819, 62408 Bethune cedex (France); Chai, F. [Laboratoire Medicaments et Biomateriaux a Liberation Controlee (INSERM U 1008, Universite Lille Nord de France), Groupe de Recherche sur les Biomateriaux (Universite Lille-2), Faculte de Medecine, 1, place de Verdun, 59045 Lille cedex (France); and others


    Close to the bone mineral phase, the calcic bioceramics, such as hydroxyapatite (HA) and {beta}-tricalcium phosphate ({beta}-TCP), are commonly used as substitutes or filling materials in bone surgery. Besides, calcium carbonate (CaCO{sub 3}) is also used for their excellent biocompatibility and bioactivity. However, the problem with the animal-origin aragonite demands the new technique to synthesize pure calcite capable of forming 3D bone implant. This study aims to manufacture and evaluate a highly-pure synthetic crystalline calcite with good cytocompatibility regarding to the osteoblasts, comparing to that of HA and {beta}-TCP. After the manufacture of macroporous bioceramic scaffolds with the identical internal architecture, their cytocompatibility is studied through MC3T3-E1 osteoblasts with the tests of cell viability, proliferation, vitality, etc. The results confirmed that the studied process is able to form a macroporous material with a controlled internal architecture, and this synthesized calcite is non-cytotoxic and facilitate the cell proliferation. Indeed requiring further improvement, the studied calcite is definitely an interesting alternative not only to coralline aragonite but also to calcium phosphate ceramics, particularly in bone sites with the large bone remodelling. Highlights: Black-Right-Pointing-Pointer Macroporous calcite manufacturing with controlled architecture as bone substitute Black-Right-Pointing-Pointer Cytotoxicity: adaptation of the colony-forming method with the target cells: MC3T3-E1 osteoblasts Black-Right-Pointing-Pointer Study of osteoblast proliferation and activity on calcite, HA and TCP.

  17. Mineral Chemistry of Melanite from Calcitic Ijolite, the Oka Carbonatite Complex, Canada:Implications for Multi-Pulse Magma Mixing

    Institute of Scientific and Technical Information of China (English)

    Wei Chen; Weiqi Zhang; Antonio Simonetti; Shaoyong Jiang


    Ti-rich garnet is found within calcitic ijolite from the Oka carbonatite complex in Can-ada, which is characterized by 58%–73% andradite component (2.12 wt.%–4.18 wt.% TiO2) and classi-fied as melanite. The garnet displays complex zoning and contains abundant high field strength ele-ments (HFSEs) and rare earth elements (REEs). Three groups (I, II, III) have been identified based on their petrographic nature. Compared to groups II and III, Group I garnet cores contain higher TiO2, MgO, HFSE, and REE and lower SiO2 abundances. The distinct chemical and petrographic signatures of the investigated garnets cannot be attributed to simple closed system crystallization, but they are consistent with the multi-pulse magma mixing. Combined with previously reported U-Pb ages for apa-tite from the calcitic ijolite, at least three stages of magma evolution and subsequent mixing have been involved in the generation of calcitic ijolite at Oka. The early-formed melt that generated Group I gar-net core was later mixed with at least two small-volume, more evolved melts. The intermediate stage melt formed the remaining garnet along with some pyroxene, calcite, nepheline, and apatite at 127±3.6 Ma. The youngest, most evolved melt generated the majority of pyroxene, calcite, nepheline, and apatite within the calcitic ijolite at 115±3.1 Ma.

  18. Fabrication of calcite blocks from gypsum blocks by compositional transformation based on dissolution-precipitation reactions in sodium carbonate solution. (United States)

    Ishikawa, Kunio; Kawachi, Giichiro; Tsuru, Kanji; Yoshimoto, Ayami


    Calcium carbonate (CaCO3) has been used as a bone substitute, and is a precursor for carbonate apatite, which is also a promising bone substitute. However, limited studies have been reported on the fabrication of artificial calcite blocks. In the present study, cylindrical calcite blocks (ϕ6×3mm) were fabricated by compositional transformation based on dissolution-precipitation reactions using different calcium sulfate blocks as a precursor. In the dissolution-precipitation reactions, both CaSO4·2H2O and CaSO4 transformed into calcite, a polymorph of CaCO3, while maintaining their macroscopic structure when immersed in 1mol/L Na2CO3 solution at 80°C for 1week. The diametral tensile strengths of the calcite blocks formed using CaSO4·2H2O and CaSO4 were 1.0±0.3 and 2.3±0.7MPa, respectively. The fabrication of calcite blocks using CaSO4·2H2O and CaSO4 proposed in this investigation may be a useful method to produce calcite blocks because of the self-setting ability and high temperature stability of gypsum precursors.

  19. Interaction of europium and nickel with calcite studied by Rutherford Backscattering Spectrometry and Time-Resolved Laser Fluorescence Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sabau, A. [Agence Nationale pour la gestion des Déchets RAdioactifs, 1-7 rue J. Monnet, Parc de la Croix Blanche, 92298 Châtenay-Malabry Cedex (France); Université de Nice Sophia Antipolis, Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), 28 avenue Valrose, 06108 Nice Cedex 2 (France); Pipon, Y., E-mail: [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); Institut Universitaire de Technologie (IUT) Lyon-1, Université Claude Bernard Lyon 1, 69 622 Villeurbanne Cedex (France); Toulhoat, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); CEA/DEN, Saclay, 91191 Gif sur Yvette (France); Lomenech, C. [Université de Nice Sophia Antipolis, Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), 28 avenue Valrose, 06108 Nice Cedex 2 (France); Jordan, N. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology (IRE) (Germany); Moncoffre, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); Barkleit, A. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology (IRE) (Germany); and others


    This study aims at elucidating the mechanisms regulating the interaction of Eu and Ni with calcite (CaCO{sub 3}). Calcite powders or single crystals (some mm sized) were put into contact with Eu or Ni solutions at concentrations ranging from 10{sup −3} to 10{sup −5} mol L{sup −1} for Eu and 10{sup −3} mol L{sup −1} for Ni. The sorption durations ranged from 1 week to 1 month. Rutherford Backscattering Spectrometry (RBS) well adapted to discriminate incorporation processes such as: (i) adsorption or co precipitation at the mineral surfaces or, (ii) incorporation into the mineral structure (through diffusion for instance), has been carried out. Moreover, using the fluorescence properties of europium, the results have been compared to those obtained by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) on calcite powders. For the single crystals, complementary SEM observations of the mineral surfaces at low voltage were also performed. Results showed that Ni accumulates at the calcite surface whereas Eu is also incorporated at a greater depth. Eu seems therefore to be incorporated into two different states in calcite: (i) heterogeneous surface accumulation and (ii) incorporation at depth greater than 160 nm after 1 month of sorption. Ni was found to accumulate at the surface of calcite without incorporation.

  20. Petrology of HP metamorphic veins in coesite-bearing eclogite from western Tianshan, China: Fluid processes and elemental mobility during exhumation in a cold subduction zone (United States)

    Lü, Zeng; Zhang, Lifei; Du, Jinxue; Yang, Xin; Tian, Zuolin; Xia, Bin


    A petrological study was carried out for high pressure (HP) veins which cut through the host coesite-bearing eclogites at Habutengsu-Kebuerte in western Tianshan, China. The results place constraints on the origin and property of metamorphic fluids during subduction-zone metamorphism. Omphacite-, clinozoisite- and quartz-dominated veins occur on centimeter to meter scales within lens-shaped and layered eclogites, or cutting into the country rocks of garnet phengite schists. Coesite-bearing eclogites mainly consist of fibrous fine-grained omphacite and porphyroblastic garnet, with minor amounts of amphibole (mainly barroisite), clinozoisite, white mica (mainly paragonite) and rutile. The veins are pronouncedly coarse-grained compared to the host eclogites and commonly consist of quartz, clinozosite, rutile, white mica (phengite and paragonite) and garnet, with or without omphacite, titanite, apatite, carbonate (mainly dolomite) and glaucophane. Fluid inclusions are abundant in vein omphacite, titanite and apatite, but are rare in the equivalent minerals of host eclogites. Rounded vein garnets usually occur close to the sharp interface of vein and host eclogite. Omphacite in the veins is characterized by its euhedral form surrounded by quartz, or coarse bladed aggregates in contrast to the fibrous or patchy one, suggesting dynamic recrystallization in the host rocks. Omphacite in both veins and host eclogites has similar jadeite contents (Jd40-50), indicating formation at eclogite-facies metamorphic conditions. Vein phengite uniformly contains certain amounts of Ba with maximum BaO content of 3.16-4.25 wt.%, suggesting that Ba was mobilized during the exhumation of UHP rocks. Specific textures of vein minerals, such as the enclosure of magnesite (or calcite) in dolomite, rutile in titanite, and the occurrence of zoned Ba-rich phengite, indicate the chemical variability of channelized fluids over time. Based on Zr content in rutile and the presence of paragonite

  1. Safety and efficacy of cryopreserved homologous veins for venous reconstruction in pancreatoduodenectomy. (United States)

    Yamamoto, Masaki; Akamatsu, Nobuhisa; Aoki, Taku; Sakamoto, Yoshihiro; Tamura, Sumihito; Hasegawa, Kiyoshi; Kokudo, Norihiro


    There are several techniques for reconstructing the portal vein-superior mesenteric vein during pancreatoduodenectomy. The aim of the present study was to present our results with portal vein-superior mesenteric vein reconstruction using cryopreserved homologous veins during pancreatoduodenectomy for patients with pancreatic head cancer. Patients who underwent pancreatoduodenectomy for pancreatic head cancer were reviewed retrospectively. In patients with portal vein-superior mesenteric vein resection, the detailed method of reconstruction and clinical outcomes were reviewed. Clinical characteristics, patient survival, and portal vein-superior mesenteric vein patency were compared between those with and without homologous vein grafts. Factors affecting the patency of reconstructed veins were assessed by univariate analysis. Among 144 patients undergoing pancreatoduodenectomy, portal vein-superior mesenteric vein resection was performed in 36 patients (25%); 18 (50%) underwent reconstruction with homologous veins, and the other 18 (50%) underwent reconstruction without homologous veins. The extent of portal vein-superior mesenteric vein involvement, operative time, duration of clamping of portal vein-superior mesenteric vein, intraoperative blood loss, and length of the venous resection were greater (P ≤ .013 each) in those with homologous vein grafts. There was no significant difference in postoperative morbidity/mortality, patient survival, or portal vein-superior mesenteric vein patency. The 1- and 2-year overall patency of portal vein-superior mesenteric vein was 76% and 71%, respectively, while the 2-year patencies were 67% and 67% in those with homologous veins and 87% and 73% in those without homologous veins without difference between the groups. Circumferential resection and pathologic portal vein-superior mesenteric vein involvement were associated with the patency of the reconstructed vein (P = .002 and P = .028, resp). Use of homologous venous

  2. Surface kinetic model for isotopic and trace element fractionation during precipitation of calcite from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    DePaolo, D.


    A surface reaction kinetic model is developed for predicting Ca isotope fractionation and metal/Ca ratios of calcite as a function of rate of precipitation from aqueous solution. The model is based on the requirements for dynamic equilibrium; i.e. proximity to equilibrium conditions is determined by the ratio of the net precipitation rate (R{sub p}) to the gross forward precipitation rate (R{sub f}), for conditions where ionic transport to the growing crystal surface is not rate-limiting. The value of R{sub p} has been experimentally measured under varying conditions, but the magnitude of R{sub f} is not generally known, and may depend on several factors. It is posited that, for systems with no trace constituents that alter the surface chemistry, R{sub f} can be estimated from the bulk far-from-equilibrium dissolution rate of calcite (R{sub b} or k{sub b}), since at equilibrium R{sub f} = R{sub b}, and R{sub p} = 0. Hence it can be inferred that R{sub f} {approx} R{sub p} + R{sub b}. The dissolution rate of pure calcite is measureable and is known to be a function of temperature and pH. At given temperature and pH, equilibrium precipitation is approached when R{sub p} (= R{sub f} - R{sub b}) << R{sub b}. For precipitation rates high enough that R{sub p} >> R{sub b}, both isotopic and trace element partitioning are controlled by the kinetics of ion attachment to the mineral surface, which tend to favor more rapid incorporation of the light isotopes of Ca and discriminate weakly between trace metals and Ca. With varying precipitation rate, a transition region between equilibrium and kinetic control occurs near R{sub p} {approx} R{sub b} for Ca isotopic fractionation. According to this model, Ca isotopic data can be used to estimate R{sub f} for calcite precipitation. Mechanistic models for calcite precipitation indicate that the molecular exchange rate is not constant at constant T and pH, but rather is dependent also on solution saturation state and hence R{sub p

  3. Ligation of superior mesenteric vein and portal to splenic vein anastomosis after superior mesenteric-portal vein confluence resection during pancreaticoduodenectomy – Case report

    Directory of Open Access Journals (Sweden)

    Jianlin Tang


    Conclusion: The lessons we learned are (1 Before SMPV confluence resection, internal jugular vein graft should be ready for reconstruction. (2 Synthetic graft is an alternative for internal jugular vein graft. (3 Direct portal vein to SMV anastomosis can be achieved by mobilizing liver. (4 It is possible that venous collaterals secondary to SMV tumor obstruction may have allowed this patient's post-operative survival.

  4. Augmented reality based real-time subcutaneous vein imaging system. (United States)

    Ai, Danni; Yang, Jian; Fan, Jingfan; Zhao, Yitian; Song, Xianzheng; Shen, Jianbing; Shao, Ling; Wang, Yongtian


    A novel 3D reconstruction and fast imaging system for subcutaneous veins by augmented reality is presented. The study was performed to reduce the failure rate and time required in intravenous injection by providing augmented vein structures that back-project superimposed veins on the skin surface of the hand. Images of the subcutaneous vein are captured by two industrial cameras with extra reflective near-infrared lights. The veins are then segmented by a multiple-feature clustering method. Vein structures captured by the two cameras are matched and reconstructed based on the epipolar constraint and homographic property. The skin surface is reconstructed by active structured light with spatial encoding values and fusion displayed with the reconstructed vein. The vein and skin surface are both reconstructed in the 3D space. Results show that the structures can be precisely back-projected to the back of the hand for further augmented display and visualization. The overall system performance is evaluated in terms of vein segmentation, accuracy of vein matching, feature points distance error, duration times, accuracy of skin reconstruction, and augmented display. All experiments are validated with sets of real vein data. The imaging and augmented system produces good imaging and augmented reality results with high speed.

  5. Clinical Features of Primary Vein Grafts in Free Tissue Transfers

    Directory of Open Access Journals (Sweden)

    Mitsuru Nemoto


    Full Text Available The outcomes of free tissue transfers combined with vein grafts have been inconsistent, and discussions continue regarding their appropriate use. Of the 142 free tissue transfers that we performed from January 2004 to December 2011, we retrospectively analyzed 15 consecutive patients who underwent free tissue transfers in combination with vein grafts. Etiologies included trauma (8 patients, infection (4, and tumor (3. Types of free tissue transfers were fibula (4, anterolateral thigh (3, groin (3, jejunum (3, latissimus dorsi (1, and dorsal pedis (1. Vein grafts were used for the artery (6, vein (2, or both (7. The donor veins were the saphenous vein (12 and the external jugular vein (3. The mean length of the grafted veins was 10.8 cm (range: 4–18 cm. Even though complications of congestion occurred in 2 patients, these flaps survived by reexploration. The flap success rate was 15 of 15 (100% of vein grafted free flaps versus 124 of 127 (97.6% of free flaps not requiring vein grafts. To improve the success rate of free tissue transfers combined with vein grafts, securing healthy recipient vessels, meticulous surgical handling, a reliable vascular anastomosis technique, and strict postoperative monitoring are crucial.

  6. A pilot/introducer needle for central vein cannulation. (United States)

    Suzuki, T; Kanazawa, M; Kinefuchi, Y; Fukuyama, H; Takiguchi, M; Yamamoto, M; Abe, K; Okuda, Y


    A kit for safe and easy insertion of a central vein cannula was devised. A small gauge (22 gauge) metal pilot needle was equipped with a Y-shaped hub which had a side-port to accept a small gauge (0.46 mm) Seldinger guide wire. Once the needle reached the vein, guidewire was threaded in through the side-port. There was no need to remove the pilot needle and no need to repeat vein puncture with a larger-bore needle. Three puncture methods were used with the kit: (1) the central approach via the internal jugular vein, (2) the supraclavicular approach via the junction of the internal jugular vein and subclavian vein, and (3) the infraclavicular approach via the subclavian vein. Each method was used on 20 patients, for total of 60 patients, with a high success rate. Less than 3 minutes were required from puncture to catheter insertion. No serious complications were encountered.

  7. Absent right superior caval vein in situs solitus

    DEFF Research Database (Denmark)

    Lytzen, Rebekka; Sundberg, Karin; Vejlstrup, Niels


    no postnatal complications. All children were found to have healthy hearts at follow-up. CONCLUSIONS: In all cases, the findings proved to be a benign condition with no clinical manifestations or complications. Although isolated absent right superior caval vein does not seem to affect the outcome, associated......Introduction In up to 0.07% of the general population, the right anterior cardinal vein obliterates and the left remains open, creating an absent right superior caval vein and a persistent left superior caval vein. Absent right superior caval vein is associated with additional congenital heart...... disease in about half the patients. We wished to study the consequences of absent right superior caval vein as an incidental finding on prenatal ultrasonic malformation screening. Material and methods This is a retrospective case series study of all foetuses diagnosed with absent right superior caval vein...

  8. [Treatment of renal vein thrombosis associated with nephrotic syndrome]. (United States)

    Funami, M; Takaba, T; Tanaka, H; Murakami, A; Kadokura, M; Hori, G; Ishii, J


    Renal vein thrombosis is a rare entity in which true incidence is unknown. The disease occurs most frequently in patients with nephrotic syndrome, but it also can occur in the presence of other hypercoagulable state. Two cases of renal vein thrombosis with nephrotic syndrome which were treated by thrombectomy are reported here. One patient was successfully treated by renal vein and inferior vena cava thrombectomy before developing severe pulmonary embolism. The other was treated by renal vein thrombectomy by which fatal shock was able to be prevented. In those cases, immediate operation was indicated, primarily to prevent additional, possibly fatal, pulmonary embolism and also to improve perfusion of the kidney. In the hope of salvaging the kidney, thrombectomy may be the treatment of choice for acute renal vein thrombosis, complication of pulmonary embolism and inferior vena cava thrombosis, right renal vein thrombosis without collateral flow and acute renal vein thrombosis with shock.

  9. The great brain versus vein debate. (United States)

    Menon, Ravi S


    From the earliest fMRI experiments, it was quickly appreciated by those working with BOLD at high field that the signal change originated from visible veins whose spatial localization was relatively coarse ("the macrovasculature"), and smaller vessels ("the microvasculature") that were not individually visible in BOLD images. It was expected that a functional brain imaging technique that was predominantly sensitive to the macrovasculature would not have the same effective resolution as one sensitive to the microvasculature. Elimination of the venous signal and enhancement of the microvascular one offered the tantalizing ability to image columnar and lamellar structures in the brain and distinguished fMRI from its predecessor techniques. This article reviews a brief history of how these signal sources were first identified and separated and some of the controversy associated with the "brain versus vein" debate.

  10. Ovarian vein thrombosis in a polytrauma patient. (United States)

    Toman, Emma; Beaven, Alastair; Balogun, Moji; Porter, Keith


    A young mother presented to a major trauma centre following a road traffic collision. Her admission CT traumagram demonstrated liver and renal lacerations, spinal and pelvic fractures with no abnormalities of the ovarian veins. Her inpatient course was uncomplicated other than a sustained, isolated raised C reactive protein. CT of the abdomen 1 week after injury demonstrated stable solid organ injuries and the additional, unexpected finding of a right ovarian vein thrombosis (OVT). A pragmatic approach was taken towards the management of the OVT given the haemorrhagic risk from her traumatic injuries. A multidisciplinary, consultant-led plan was made to slowly increase enoxaparin to a therapeutic dose under close surveillance and to then switch to warfarin following an outpatient consultation with a consultant haematologist. A MR venogram was performed after 3 months of anticoagulation, and this demonstrated complete resolution of the OVT and normal appearances of the ovary.

  11. Pulmonary vein stenosis: Etiology, diagnosis and management

    Institute of Scientific and Technical Information of China (English)

    Pablo Pazos-López; Cristina García-Rodríguez; Alba Guitián-González; Emilio Paredes-Galán; María ángel; De La Guarda álvarez-Moure; Marta Rodríguez-álvarez; José Antonio Baz-Alonso; Elvis Teijeira-Fernández; Francisco Eugenio Calvo-Iglesias; Andrés í?iguez-Romo


    Pulmonary vein stenosis(PVS) is rare condition characterized by a challenging diagnosis and unfavorable prognosis at advance stages. At present, injury from radiofrequency ablation for atrial fibrillation has become the main cause of the disease. PVS is characterized by a progressive lumen size reduction of one or more pulmonary veins that, when hemodynamically significant, may raise lobar capillary pressure leading to signs and symptoms such as shortness of breath, cough, and hemoptysis. Image techniques(transesophageal echocardiography, computed tomography, magnetic resonance and perfusion imaging) are essential to reach a final diagnosis and decide an appropriate therapy. In this regard, series from referral centers have shown that surgical and transcatheter interventions may improve prognosis. The purpose of this article is to review the etiology, assessment and management of PVS.

  12. Doppler spectral characteristics of infrainguinal vein bypasses

    DEFF Research Database (Denmark)

    Nielsen, Tina G; von Jessen, F; Sillesen, H


    With the aim of assessing the velocity profile of femoropopliteal and femorocrural vein bypasses, 128 patients undergoing infrainguinal vein bypass surgery entered a postoperative Duplex surveillance protocol, which included clinical assessment and Duplex scanning, using Doppler spectral analysis...... of arteriovenous fistulas the initially antegrade diastolic velocity was replaced by a retrograde flow within 3 months, whereas a forward flow in diastole was sustained in grafts with patent fistulas. Abnormal Duplex findings in 31 patients led to angiography and revision in 13 cases. Four revised grafts failed......, while nine remained patent at follow-up 1-12 months later. Ten (56%) of 18 non-revised bypasses with abnormal Duplex findings failed within 9 months compared to 1 (1%) of 76 bypasses with a normal velocity profile (p analysis provides...

  13. Massive hydrothorax following subclavian vein catheterization


    Omar, Hesham R.; fathy, Ahmad; Elghonemy, Mohamed; Rashad, Rania; Helal, Engy; Mangar, Devanand; Camporesi, Enrico


    Since the introduction of central venous catheterization for monitoring of the venous pressure, fluid infusion and hyperalimentation, the literature has been full of serious life-threatening complications. Of these complications is the false positioning of the central venous catheter and subsequent development of pleural effusion. In this report we are describing a case of iatrogenic massive pleural effusion following subclavian vein catheterization necessitating intercostal tube drainage and...

  14. Central Vein Preservation in Critical Venous Access. (United States)

    Davidson, J; Paul, A; Patel, S; Davenport, M; Ade-Ajayi, N


    Introduction The lack of suitable veins in children with critical central venous access requirements is a major obstacle to optimal care and is potentially life-threatening. We present outcomes following the use of vein-preserving (VP) surgical techniques, notably the sheath exchange for tunneled lines (SETL). Materials and Methods A retrospective, single observer analysis of a prospectively maintained departmental logbook as well as the medical records of patients. Two broad groups of central line replacements were identified; those inserted following removal of a previous line and a traditional "plastic-free" (PF) period and those exchanged without such an interval. Results Overall, 19 lines were directly exchanged during the study period and compared with 34 inserted after a PF period. Similar catheter life spans and infection rates were demonstrated in each group; 125 (range, 78-173) days in VP exchanges versus 122 (range, 70-175) days in PF replacements (p = 0.41). Line Sepsis resulting in removal or change of line occurred at 103 (range, 60-147) days in VP group versus 104 (range, 45-164) days in PF (p = 0.73). Conclusion For children with critical venous access requirements, direct line exchange procedures are a robust and reproducible means of vein preservation. The outcomes compare favorably with those following the more traditional removal, a PF period and reinsertion.

  15. Portal vein thrombosis related to Cassia angustifolia. (United States)

    Soyuncu, Secgin; Cete, Yildiray; Nokay, Ali E


    Cassia angustifolia (Senna), used as a laxative, is a plant from the Fabaceae family. It includes hydroxyanthracene glycosides, also known as Senna Sennoside. These glycosides stimulate the peristalsis of the colon and alter colonic absorption and secretion resulting in fluid accumulation and expulsion. In the literature, there are reports illustrating the hepatotoxic effects of Cassia angustifolia but there is no report of portal vein thrombosis caused by Cassia Angustifolia. A 42-year-old woman was admitted to the emergency department with a five-day history of worsening epigastric pain, anorexia, episodic vomiting, and intermittent fever. She reported that she had boiled dried senna leaves she had bought from herbalists and drank approximately 200 mL daily for two years. Color Doppler screening found an echogen thrombus obliterating portal vein bifurcation and the right branch. The lumen was obstructed at this level and there was no blood flow through it. Treatment with thrombolytics was unsuccessful. Severe hepatotoxicity senna use is unusual. The cause of senna-related hepatotoxicity is unclear but could be explained by the exposure of the liver to unusual amounts of toxic metabolites of anthraquinone glycosides. Chronic use of Cassia angustifolia may rarely be associated with portal vein thrombosis.

  16. Laser photocoagulation for retinal vein occlusion

    Directory of Open Access Journals (Sweden)

    K. A. Mirzabekova


    Full Text Available Retinal vein occlusion (RVO is one of the leading causes of permanent vision loss. In adults, central retinal vein occlusion (CRVO occurs in 1.8% while branch retinal vein occlusion (BRVO occurs in 0.2%. Treatment strategy and disease prognosis are determined by RVO type (ischemic/non-ischemic. Despite numerous studies and many current CRVO and BRVO treatment approaches, the management of these patients is still being debated. Intravitreal injections of steroids (triamcinolone acetate, dexamethasone and vascular endothelial growth factor (VEGF inhibitors (bevacizumab, ranibizumab were shown to be fairly effective. However, it is unclear whether anti-VEGF agents are reasonable in ischemic RVOs. Laser photocoagulation remains the only effective treatment of optic nerve head and/or retinal neovascularization. Laser photocoagulation is also indicated for the treatment of macular edema. Both threshold and sub-threshold photocoagulation may be performed. Photocoagulation performed with argon (514 nm, krypton (647 nm, or diode (810 nm laser for macular edema provides similar results (no significant differences. The treatment may be complex and include medication therapy and/or surgery. Medication therapy includes anti-aggregant agents and antioxidants, i.e., emoxypine which may be used in acute RVO as well as in post-thrombotic retinopathy. 

  17. Comparison between mechanical properties of human saphenous vein and umbilical vein

    Directory of Open Access Journals (Sweden)

    Hamedani Borhan


    Full Text Available Abstract Background As a main cause of mortality in developed countries, Coronary Artery Disease (CAD is known as silent killer with a considerable cost to be dedicated for its treatment. Coronary Artery Bypass Graft (CABG is a common remedy for CAD for which different blood vessels are used as a detour. There is a lack of knowledge about mechanical properties of human blood vessels used for CABG, and while these properties have a great impact on long-term patency of a CABG. Thus, studying these properties, especially those of human umbilical veins which have not been considered yet, looks utterly necessary. Methods Umbilical vein, as well as human Saphenous vein, are respectively obtained after cesarean and CABG. First, histological tests were performed to investigate different fiber contents of the samples. Having prepared samples carefully, force-displacement results of samples were rendered to real stress–strain measurements and then a fourth-order polynomial was used to prove the non-linear behavior of these two vessels. Results Results were analyzed in two directions, i.e. circumferentially and longitudinally, which then were compared with each other. The comparison between stiffness and elasticity of these veins showed that Saphenous vein’s stiffness is much higher than that of umbilical vein and also, it is less stretchable. Furthermore, for both vessels, longitudinal stiffness was higher than that of circumferential and in stark contrast, stretch ratio in circumferential direction came much higher than longitudinal orientation. Conclusion Blood pressure is very high in the region of aorta, so there should be a stiff blood vessel in this area and previous investigations showed that stiffer vessels would have a better influence on the flow of bypass. To this end, the current study has made an attempt to compare these two blood vessels’ stiffness, finding that Saphenous vein is stiffer than umbilical vein which is somehow as stiff as

  18. Calcite growth-rate inhibition by fulvic acids isolated from Big Soda Lake, Nevada, USA, The Suwannee River, Georgia, USA and by polycarboxylic acids (United States)

    Reddy, Michael M.; Leenheer, Jerry


    Calcite crystallization rates are characterized using a constant solution composition at 25°C, pH=8.5, and calcite supersaturation (Ω) of 4.5 in the absence and presence of fulvic acids isolated from Big Soda Lake, Nevada (BSLFA), and a fulvic acid from the Suwannee River, Georgia (SRFA). Rates are also measured in the presence and absence of low-molar mass, aliphatic-alicyclic polycarboxylic acids (PCA). BSLFA inhibits calcite crystal-growth rates with increasing BSLFA concentration, suggesting that BSLFA adsorbs at growth sites on the calcite crystal surface. Calcite growth morphology in the presence of BSLFA differed from growth in its absence, supporting an adsorption mechanism of calcite-growth inhibition by BSLFA. Calcite growth-rate inhibition by BSLFA is consistent with a model indicating that polycarboxylic acid molecules present in BSLFA adsorb at growth sites on the calcite crystal surface. In contrast to published results for an unfractionated SRFA, there is dramatic calcite growth inhibition (at a concentration of 1 mg/L) by a SRFA fraction eluted by pH 5 solution from XAD-8 resin, indicating that calcite growth-rate inhibition is related to specific SRFA component fractions. A cyclic PCA, 1, 2, 3, 4, 5, 6-cyclohexane hexacarboxylic acid (CHXHCA) is a strong calcite growth-rate inhibitor at concentrations less than 0.1 mg/L. Two other cyclic PCAs, 1, 1 cyclopentanedicarboxylic acid (CPDCA) and 1, 1 cyclobutanedicarboxylic acid (CBDCA) with the carboxylic acid groups attached to the same ring carbon atom, have no effect on calcite growth rates up to concentrations of 10 mg/L. Organic matter ad-sorbed from the air onto the seed crystals has no effect on the measured calcite crystal-growth rates.

  19. Effect of organic ligands on Mg partitioning and Mg isotope fractionation during low-temperature precipitation of calcite (United States)

    Mavromatis, Vasileios; Immenhauser, Adrian; Buhl, Dieter; Purgstaller, Bettina; Baldermann, Andre; Dietzel, Martin


    Calcite growth experiments have been performed at 25 oC and 1 bar pCO2 in the presence of aqueous Mg and six organic ligands in the concentration range from 10-5 to 10-3 M. These experiments were performed in order to quantify the effect of distinct organic ligands on the Mg partitioning and Mg stable isotope fractionation during its incorporation in calcite at similar growth rates normalized to total surface area. The organic ligands used in this study comprise of (i) acetate acid, (ii) citrate, (iii) glutamate, (iv) salicylate, (v) glycine and (vi) ethylenediaminetetraacetic acid (EDTA), containing carboxyl- and amino-groups. These fuctional groups are required for bacterial activity and growth as well as related to biotic and abiotic mineralization processes occurring in sedimentary and earliest diagenetic aquatic environments (e.g. soil, cave, lacustrine, marine). The results obtained in this study indicate that the presence of organic ligands promotes an increase in the partition coefficient of Mg in calcite (DMg = (Mg/Ca)calcite (Mg/Ca)fluid). This behaviour can be explained by the temporal formation of aqueous Mg-ligand complexes that are subsequently adsorbed on the calcite surfaces and thereby reducing the active growth sites of calcite. The increase of DMg values as a function of the supersaturation degree of calcite in the fluid phase can be described by the linear equation LogDMg =0.3694 (±0.0329)×SIcalcite - 1.9066 (±0.0147); R2=0.92 In contrast, the presence of organic ligands, with exception of citrate, does not significantly affect the Mg isotope fractionation factor between calcite and reactive fluid (Δ26Mgcalcite-fluid = -2.5 ±0.1). Citrate likely exhibits larger fractionation between the Mg-ligand complexes and free aqueous Mg2+, compared to the other organic ligands studied in this work, as evidenced by the smaller Δ26Mgcalcite-fluid values. These results indicate that in Earth's surface calcite precipitating environments that are

  20. Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy (United States)

    Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang


    Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

  1. Non-cuffed dual lumen catheters in the external jugular veins versus other central veins for hemodialysis patients. (United States)

    Moini, Majid; Rasouli, Mohammad R; Kenari, Mohammad Mahmoodzadeh; Mahmoodi, Hamid Reza


    To compare prospective between insertion of non-cuffed dual lumen catheter in the external jugular vein and other central veins for hemodialysis (HD), we studied 68 chronic dialysis patients randomly allocated into two groups: one with external jugular vein catheterization as access for HD and another with other central venous catheterization, internal jugular or subclavian vein. Our results showed there were no significant differences regarding successful cannulation, com-plications, total numbers of dialysis, development of pain and infection at the site of cannulation, patency rate of the catheters, and efficacy of hemodialysis between both groups. In addition, the patency of the catheter in the external jugular vein was not affected by previous cannulation of other central veins. In contrast, there was a significant correlation between numbers of attempts for cannulation in both groups and development of hematoma and infection, (pvein may be an alternative for other central veins for insertion of temporary non-cuffed hemodialysis catheter.

  2. Search For Past Life On Mars: Physical And Chemical Characterization Of Calcite Minerals Of Biotic And Abiotic Origin (United States)

    Stalport, Fabien; Coll, P.; Cabane, M.; Person, A.; Navarro-Gonzales, R.; Raulin, F.; Valay, M.; Ausset, P.; Szopa, C.; McKay, C. P.


    Several lines of evidence suggest that early Mars once had liquid water on its surface, a denser atmosphere and a mild climate. Similar environmental conditions led to the origin of life on the Earth more than 3.5 billion years ago; consequently, life might also have originated on Mars. We contend that inorganic compounds could give us interesting clues as to the existence of possible biological activity in future astrobiological missions to Mars. Consequently, we have investigated the physical and chemical properties of calcite, which could be expected on Mars because liquid water was certainly present on the surface of early Mars and carbon dioxide was abundant in its atmosphere. Calcite is interesting because on Earth this mineral is produced by abiotic processes as well as by biological activity. One may suppose that crystalline defects and trace element in the crystal lattice and the growth speed of biotic calcites must indicate a difference between them and pure abiotic calcites. We investigated twelve different terrestrial calcite samples from various origins: biotic, diagenetic and abiotic. The minerals were studied by X-ray diffraction and electron scanning microscopy to determine their mineralogical and chemical composition, and differential thermal analysis coupled to thermogravimetric analysis (DTA-TG) to determine their thermal behavior. Our results show that the thermal degradation of abiotic calcite starts at a temperature at least 40°C higher than the degradation temperature of any biotic calcite investigated. Consequently, in the case of a Martian in-situ study or in a sample return mission, the analysis of Martian minerals by DTA-TG represents a promising approach to detect evidence of past biological activity on Mars.

  3. Search for past life on Mars: Physical and chemical characterization of minerals of biotic and abiotic origin: part 1 - Calcite (United States)

    Stalport, Fabien; Coll, Patrice; Cabane, Michel; Person, Alain; González, Rafael Navarro; Raulin, Francois; Vaulay, Marie Jo; Ausset, Patrick; McKay, Chris P.; Szopa, Cyril; Zarnecki, John


    Several lines of evidence suggest that early Mars once had liquid water on its surface, a denser atmosphere and a mild climate. Similar environmental conditions led to the origin of life on the Earth more than 3.5 billion years ago; consequently, life might also have originated on Mars. The Viking landers searched for evidence of organic molecules on the surface of Mars, and found that the Martian soil is depleted in organics at ppb levels at the landing sites. We contend that inorganic compounds could give us interesting clues as to the existence of possible biological activity in future astrobiological missions to Mars. Consequently, we have investigated the physical and chemical properties of calcite, which could be expected on Mars because liquid water was certainly present on the surface of early Mars and carbon dioxide was abundant in its atmosphere. Calcite is interesting because on Earth this mineral is produced by abiotic processes as well as by biological activity. One may suppose that crystalline defects and trace element in the crystal lattice and the growth speed of biotic calcites must indicate a difference between them and pure abiotic calcites. We investigated twelve different terrestrial calcite samples from various origins: biotic, diagenetic and abiotic. The minerals were studied by X-ray diffraction and electron scanning microscopy to determine their mineralogical and chemical composition, and differential thermal analysis coupled to thermogravimetric analysis (DTA-TG) to determine their thermal behavior. Our results show that the thermal degradation of abiotic calcite starts at a temperature at least 40°C higher than the degradation temperature of any biotic calcite investigated. Consequently, in the case of a Martian in-situ study or in a sample return mission, the analysis of Martian minerals by DTA-TG represents a promising approach to detect evidence of past biological activity on Mars.

  4. Texture evolution in calcite gouge formed at sub-seismic slip (United States)

    Delle Piane, Claudio; Luzin, Vladimir; Timms, Nick E.; Ben Clennell, M.; Giwelli, Ausama


    Carbonate rocks are abundant in the upper crust and are notoriously seismogenic with Mw>6 earthquakes nucleating in fault zones in carbonate dominated units around the world. Field observations describe fault zones as characterised by a narrow principal slip zone at their core, containing fine, granular wear material referred to as fault gouge, produced during cumulative slip. The current literature on the link between texture and frictional properties of calcite gouges is very limited and somewhat contradictory: based on the study of a natural calcite gouge a link has been proposed between the presence of a crystallographic preferred orientation (CPO) and past seismic activity on the gouge hosting fault zone. However, similar features in terms of CPO were also identified on gouges experimentally generated at slip velocities well below the seismic ones, therefore questioning their interpretation as diagnostic of past seismic events. We studied the evolution of friction coefficient and texture on calcite gouges experimentally produced by means of high pressure direct shear experiments on large, water saturated, intact blocks of travertine (calcite 99 % wt.). Several blocks were deformed at room temperature up to different amounts of maximum displacements (20 mm, 70 mm and 120 mm) under an imposed sub-seismic slip rate of approximately 0.1 microns/s. Microstructural characterization of the deformed blocks was subsequently carried out on samples representing the highest strained portion s of each blocks (i.e. gouge zones). Local and bulk texture of the original and deformed materials was studied by means of electron backscattered diffraction (EBSD) and neutron diffraction, respectively. Direct shear experiments consistently indicate an evolution of the friction coefficient stabilizing at around values of 0.6 after 15 mm of slip. Macroscopic observations on the deformed blocks indicate that deformation is localised in a narrow band of extreme grain size reduction

  5. Reconstructing Cambro-Ordovician Seawater Composition using Clumped Isotope Paleothermometry on Calcitic and Phosphatic Brachiopods (United States)

    Bergmann, K.; Robles, M.; Finnegan, S.; Hughes, N. C.; Eiler, J. M.; Fischer, W. W.


    A secular increase in δ18O values of marine fossils through early Phanerozoic time raises questions about the evolution of climate and the water cycle. This pattern suggests two end-member hypotheses 1) surface temperatures during early Paleozoic time were very warm, in excess of 40°C (tropical MAT), or 2) the isotopic composition of seawater increased by up to 7-8‰. It has been difficult to evaluate these hypotheses because the δ18O composition of fossils depends on both temperature and the δ18O of water. Furthermore, primary isotopic signatures can be overprinted by diagenetic processes that modify geological materials. This too could explain the decrease in δ18O values of marine fossils with age. Carbonate clumped isotope thermometry can constrain this problem by providing an independent measure of crystallization temperature and, when paired with classical δ18O paleothermometry, can determine the isotopic composition of the fluid the mineral last equilibrated with. Combined with traditional tools, this method has the potential to untangle primary isotopic signatures from diagenetic signals. We measured the isotopic ordering of CO3 groups (Δ47) substituted into the phosphate lattice of phosphatic brachiopods in Cambrian strata. Phosphatic fossils are generally less soluble than carbonates in surface and diagenetic environments, and so are hypothesized to provide a more robust record of primary growth conditions. They also provide an archive prior to the rise of thick shelled calcitic fossils during the Ordovician Radiation. Additionally, measurements of the δ18O of the CO3 groups can be compared with the δ18O of PO4 groups to test whether their mutual fractionation is consistent with primary growth and the apparent temperature recorded by carbonate clumped isotope measurements. We are constructing a phosphatic brachiopod calibration for carbonate clumped isotope thermometry, and Δ47 values of CO2 extracted from modern phosphatic brachiopods suggest

  6. Quantification of deep medullary veins at 7 T brain MRI

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    Kuijf, Hugo J.; Viergever, Max A.; Vincken, Koen L. [University Medical Center Utrecht, Image Sciences Institute, Utrecht (Netherlands); Bouvy, Willem H.; Razoux Schultz, Tom B.; Biessels, Geert Jan [University Medical Center Utrecht, Department of Neurology, Brain Center Rudolf Magnus, Utrecht (Netherlands); Zwanenburg, Jaco J.M. [University Medical Center Utrecht, Image Sciences Institute, Utrecht (Netherlands); University Medical Center Utrecht, Department of Radiology, Utrecht (Netherlands)


    Deep medullary veins support the venous drainage of the brain and may display abnormalities in the context of different cerebrovascular diseases. We present and evaluate a method to automatically detect and quantify deep medullary veins at 7 T. Five participants were scanned twice, to assess the robustness and reproducibility of manual and automated vein detection. Additionally, the method was evaluated on 24 participants to demonstrate its application. Deep medullary veins were assessed within an automatically created region-of-interest around the lateral ventricles, defined such that all veins must intersect it. A combination of vesselness, tubular tracking, and hysteresis thresholding located individual veins, which were quantified by counting and computing (3-D) density maps. Visual assessment was time-consuming (2 h/scan), with an intra-/inter-observer agreement on absolute vein count of ICC = 0.76 and 0.60, respectively. The automated vein detection showed excellent inter-scan reproducibility before (ICC = 0.79) and after (ICC = 0.88) visually censoring false positives. It had a positive predictive value of 71.6 %. Imaging at 7 T allows visualization and quantification of deep medullary veins. The presented method offers fast and reliable automated assessment of deep medullary veins. (orig.)

  7. Abdominal thromboses of splanchnic, renal and ovarian veins. (United States)

    De Stefano, Valerio; Martinelli, Ida


    Thromboses of abdominal veins outside the iliac-caval axis are rare but clinically relevant. Early deaths after splanchnic vein thrombosis occur in 5-30% of cases. Sequelae can be liver failure or bowel infarction after splanchnic vein thrombosis, renal insufficiency after renal vein thrombosis, ovarian infarction after ovarian vein thrombosis. Local cancer or infections are rare in Budd-Chiari syndrome, and common for other sites. Inherited thrombophilia is detected in 30-50% of patients. Myeloproliferative neoplasms are the main cause of splanchnic vein thrombosis: 20-50% of patients have an overt myeloproliferative neoplasm and/or carry the molecular marker JAK2 V617F. Renal vein thrombosis is closely related to nephrotic syndrome; finally, ovarian vein thrombosis can complicate puerperium. Heparin is used for acute treatment, sometimes in conjunction with systemic or local thrombolysis. Vitamin K-antagonists are recommended for 3-6 months, and long-term in patients with Budd-Chiari syndrome, unprovoked splanchnic vein thrombosis, or renal vein thrombosis with a permanent prothrombotic state such as nephrotic syndrome.

  8. Automated detection of periventricular veins on 7 T brain MRI (United States)

    Kuijf, Hugo J.; Bouvy, Willem H.; Zwanenburg, Jaco J. M.; Viergever, Max A.; Biessels, Geert Jan; Vincken, Koen L.


    Cerebral small vessel disease is common in elderly persons and a leading cause of cognitive decline, dementia, and acute stroke. With the introduction of ultra-high field strength 7.0T MRI, it is possible to visualize small vessels in the brain. In this work, a proof-of-principle study is conducted to assess the feasibility of automatically detecting periventricular veins. Periventricular veins are organized in a fan-pattern and drain venous blood from the brain towards the caudate vein of Schlesinger, which is situated along the lateral ventricles. Just outside this vein, a region-of- interest (ROI) through which all periventricular veins must cross is defined. Within this ROI, a combination of the vesselness filter, tubular tracking, and hysteresis thresholding is applied to locate periventricular veins. All detected locations were evaluated by an expert human observer. The results showed a positive predictive value of 88% and a sensitivity of 95% for detecting periventricular veins. The proposed method shows good results in detecting periventricular veins in the brain on 7.0T MR images. Compared to previous works, that only use a 1D or 2D ROI and limited image processing, our work presents a more comprehensive definition of the ROI, advanced image processing techniques to detect periventricular veins, and a quantitative analysis of the performance. The results of this proof-of-principle study are promising and will be used to assess periventricular veins on 7.0T brain MRI.

  9. Development of HIFU Therapy System for Lower Extremity Varicose Veins (United States)

    Ota, Ryuhei; Suzuki, Jun; Yoshinaka, Kiyoshi; Deguchi, Juno; Takagi, Shu; Miyata, Tetsuro; Matsumoto, Yoichiro


    High-intensity focused ultrasound (HIFU) treatment utilizing microbubbles was investigated in the present study. It is known that microbubbles have the potential to enhance the heating effects of an ultrasound field. In this study, the heat accompanying microbubble oscillation was used to occlude varicose veins. Alteration of veins was observed after ultrasound irradiation. Veins were resected by stripping. In this study, two vein conditions were adopted during HIFU irradiation; non-compressed and compressed. Compressing the vein was expected to improve occlusion by rubbing the altered intima under compressed conditions. The frequency of the ultrasound was 1.7 MHz, the intensity at the focus was 2800 W/cm2, and the irradiation time was 20 s. In this study, the contrast agent Levovist® was chosen as a microbubble source, and the void fraction (ratio of total gas volume to liquid) in the vein was fixed at 10-5. Under non-compressed conditions, changes were observed only at the adventitia of the vein anterior wall. In contrast, under compressed conditions, changes were observed from the intima to the adventitia of both the anterior and posterior walls, and they were partly stuck together. In addition, more experiments with hematoxylin-eosin staining suggested that the changes in the vein were more substantial under the latter conditions. From these results, it was confirmed that the vein was occluded more easily with vein compression.

  10. Computed tomographic evaluation of the portal vein in the hepatomas

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kee Hyung; Lee, Seung Chul; Bae, Man Gil; Seo, Heung Suk; Kim, Soon Yong; Lee, Min Ho; Kee, Choon Suhk; Park, Kyung Nam [Hanyang University College of Medicine, Seoul (Korea, Republic of)


    Computed tomography and pornographic findings of 63 patients with hepatoma, undergone hepatic angiography and superior mesenteric pornography for evaluation of tumor and thrombosis of portal vein and determination of indication of transcatheter arterial embolization for palliative treatment of hepatoma from April, 85 to June, 86 in Hanyang university hospital, were reviewed. The results were as follows: 1. In 36 cases, portal vein thrombosis was detected during photography. Nineteen of 37 cases which revealed localized hepatoma in the right lobe of the liver showed portal vein thrombosis; 9 of 11 cases of the left lobe; 8 of 14 cases which were involved in entire liver revealed thrombosis. One case localized in the caudate lobe showed no evidence of invasion to portal vein. 2. Twenty-four of 34 cases with diffuse infiltrative hepatoma revealed portal vein thrombosis and the incidence of portal vein thrombosis in this type were higher than in the cases of the nodular type. 3. The portal vein thrombosis appeared as filling defects of low density in the lumen of the portal veins in CT and they did not reveal contrast enhancement. 4. CT revealed well the evidence of obstructions in the cases of portal vein thrombosis and the findings were well-corresponded to the findings of the superior mesenteric photography. 5. Five of the cases of the portal vein thrombosis were missed in the CT and the causes were considered as due to partial volume effect of enhanced portal vein with partial occlusion or arterioportal shunts. 6. Six of 13 cases with occlusion of main portal vein showed cavernous transformation and they were noted as multiple small enhanced vascularities around the porta hepatis in the CT. According to the results, we conclude that CT is a useful modality to detect the changes of the portal veins in the patients of the hepatoma.

  11. Calcite/opal deposits at Yucca Mountain, Nevada: Pedogenic or hypogene?

    Energy Technology Data Exchange (ETDEWEB)

    Hill, C.A.; Schluter, C.M.; Harmon, R.S. [and others


    This study is part of the research program of the Yucca Mountain Project intended to provide the State of Nevada with a detailed assessment of the geology and geochemistry of Yucca Mountain and adjacent regions. The purpose of this paper is to consider all of the geological and geochemical data available for the calcite/opal deposits at Yucca Mountain and to ascertain whether this data favors a pedogenic or hyogene origin for these deposits. Far from being of esoteric concern, this subject is of paramount importance to the debate which rages around the suitability of Yucca Mountain as a high-level radioactive waste repository site. It is also the purpose of this paper to serve as a foundation for a lengthy feature article to be submitted for publication in 1994. In addition, a stand has been taken by the National Research Council of the National Academy of Sciences against the upwelling-water model (a vote of 17 to 0 against), and this same panel report has concluded that {open_quotes}there is no compelling evidence for the repetitive flooding of the environment by expulsion of groundwater{close_quotes} and that {open_quotes}instead, the evidence strongly supports the idea that the near-surface mineral deposits resulted from percolating rainwater, which carried soil minerals down into rock fractures{close_quotes}. Based on such information the Department of Energy has stated that it {open_quotes}finds no basis to continue to study the origin of these specific deposits{close_quotes}. This study, based upon many different independent lines of evidence, reaches the opposite conclusion and instead favors a hypogene spring-travertine origin for the controversial calcite/opal deposits at Yucca Mountain. This study recognizes a pedogenic carbonate component at Yucca Mountain, but argues that this component is distinct from, and sometimes intermixed with, the calcite/opal deposits.

  12. Geochemical evidence for repetitive intracrystal recrystallization during the mineralogical stabilization of some biogenic Mg calcites

    Energy Technology Data Exchange (ETDEWEB)

    Budd, D.A. (Univ. of Colorado, Boulder, CO (United States). Dept. of Geological Sciences)


    Mineralogical stabilization of porcellaneous foraminifera is unique relative to other types of bioclasts in that these foraminifera is unique relative to other types of bioclasts in that these foraminifera can undergo stabilization to low-Mg calcite without any textural change. Holocene porcellaneous foraminifer from the freshwater diagenetic zone of the Schooner Cays, Bahamas, are in the midst of this alteration and thus provide a rare insight into the stabilization process. These bioclasts exhibit Mg loss and oxygen isotopic changes with no textural alteration at any scale. The mineralogical stabilization, or recrystallization, is a repetitive intracrystal process. Each recrystallization produces a calcite with a slightly lower Mg content than its predecessor. The stabilization rate is dependent on time and hydrologic flux; older phreatic-zone material is the most altered and younger vadose-zone material is the least altered. Numerical modeling of the chemical diagenesis suggests that the molar water:rock ratio of a single recrystallization is about 1:100 and that the resultant precipitate is not in equilibrium with the ambient pore waters. Repetitive recrystallizations, however, eventually yield a mineralogically stable low-Mg calcite that can be in equilibrium with the bulk pore waters. Complete mineralogical stabilization to LMC should occur at cumulative molar water:rock ratios of about 16 and requires hundreds to thousands of recrystallizations, each reducing Mg content by less than 0.01 mole %. The large number of recrystallizations with incrementally small chemical changes per recrystallization makes alteration of these foraminifera significantly different from single-step recrystallization of other types of bioclasts.

  13. Influence of temperature and CO2 on the strontium and magnesium composition of coccolithophore calcite

    Directory of Open Access Journals (Sweden)

    M. N. Müller


    Full Text Available Marine calcareous sediments provide a fundamental basis for paleoceanographic studies aiming to reconstruct past oceanic conditions and understand key biogeochemical element cycles. Calcifying unicellular phytoplankton (coccolithophores are a major contributor to both carbon and calcium cycling by photosynthesis and the production of calcite (coccoliths in the euphotic zone and the subsequent long-term deposition and burial into marine sediments. Here we present data from controlled laboratory experiments on four coccolithophore species and elucidate the relation between the divalent cation (Sr, Mg and Ca partitioning in coccoliths and cellular physiology (growth, calcification and photosynthesis. Coccolithophores were cultured under different seawater temperature and carbonate chemistry conditions. The partition coefficient of strontium (DSr was positively correlated with both carbon dioxide (pCO2 and temperature but displayed no coherent relation to particulate organic and inorganic carbon production rates. Furthermore, DSr correlated positively with cellular growth rates when driven by temperature but no correlation was present when changes in growth rates were pCO2-induced. The results demonstrate the complex interaction between environmental forcing and physiological control on the strontium partitioning in coccolithophore calcite. The partition coefficient of magnesium (DMg displayed species-specific differences and elevated values under nutrient limitation. No conclusive correlation between coccolith DMg and temperature was observed but pCO2 induced a rising trend in coccolith DMg. Interestingly, the best correlation was found between coccolith DMg and chlorophyll a production suggesting that chlorophyll a and calcite associated Mg originate from the same intracellular pool. These results give an extended insight into the driving factors that lead to variations in the coccolith Mg / Ca ratio and can be used for Sr / Ca and Mg / Ca

  14. Subglacial Calcites from Northern Victoria Land: archive of Antarctic volcanism in the Last Glacial Maximum (United States)

    Frisia, Silvia; Weirich, Laura; Hellstrom, John; Borsato, Andrea; Golledge, Nicholas R.; Anesio, Alexandre M.; Bajo, Petra; Drysdale, Russell N.; Augustinus, Paul C.; Barbante, Carlo; Cooper, Alan


    Subglacial carbonates bear similarities to stalagmites in their fabrics and the potential to obtain precise chronologies using U-series methods. Their chemical properties also reflect those of their parent waters, which, in contrast to stalagmites, are those of subglacial meltwaters. In analogy to speleothems, stable Carbon isotope ratios and trace elements such as Uranium, Iron and Manganese provide the opportunity to investigate ancient extreme environments without the need to drill through thousands of metres of ice. Sedimentological, geochemical and microbial evidence preserved in LGM subglacial calcites from Northern Victoria Land, close to the East Antarctic Ice Sheet margin, allow us to infer that subglacial volcanism was active in the Trans Antarctic Mountain region and induced basal ice melting. We hypothesize that a meltwater reservoir was drained and injected into interconnected basal pore systems where microbial processes enhanced bedrock weathering and, thus, released micronutrients. Volcanic influence is supported by the presence of fluorine (F) and sulphur in sediment-laden calcite layers containing termophilic species. Notably, calcite δ13C points to dissolved inorganic carbon evolved from subglacial metabolic processes. Once transported to the sea, soluble iron likely contributed to fertilizing the Southern Ocean and CO2 drawdown. This is the first well-dated evidence for LGM volcanism in Antarctica, which complements the record of volcanic eruptions retrieved from Talos Dome ice core, and supports the hypothesis of large-scale volcanism as an important driver of climate change. We conclude that subglacial carbonates are equivalent to speleothems in their palaeoclimate potential and may become a most useful source of information of ecosystems and processes at peak glacials in high altitude/high latitude settings.

  15. Graphitic carbon formation through calcite reduction in blueschist metasediments from Alpine Corsica (France) (United States)

    Galvez, M.; Beyssac, O.; Martinez, I.; Benzerara, K.; Malvoisin, B.


    The geochemistry of reduced carbon in subduction zones is strongly affected by mineral equilibria. We study here the geochemistry of carbon in siliceous-marbles at the direct contact with serpentinites in the Alpine eclogitic meta-ophiolithic units of northern Corsica (France). We have combined petrology, Raman spectroscopy and carbon isotopy to provide a description of both the organic and carbonate components of the rocks across a reaction front where the reaction CaCO3+SiO2+2H2=CaSiO3+C+2H2O is evidenced. The continuous reaction zone is composed by a centimeter thick pale nephrite layer at the contact with the serpentinites, followed by a thin wollastonite layer and a 5 to 20 cm thick dark zone composed of wollastonite, carbonaceous material (CM), quartz but no carbonates. There is a sharp transition to the overlying original metasediment composed of calcite+quartz which is significantly less rich in CM. Raman spectroscopy shows that CM is much more graphitic in the reaction zone than in the original sediment. Significant isotopic differences are observed apart the reaction front with δ13C (CM) and δ13C (calcite) around -15‰ and 1.3‰ respectively in the original rock far from the reaction zone, whereas δ13C (CM) is around -1‰ in the reaction zone. We interpret the graphitic CM in the reaction zone as formed from the destabilization and reduction of calcite due to the diffusion of reducing fluids from the underlying serpentinite unit. Mass balance calculations support this hypothesis and show that a complete reduction of carbonates might have occurred. The timing of this abiotic macromolecular and graphitic C formation is discussed. We show that the combined study of isotopic geochemistry and structure of inorganic and organic carbon in metamorphic rocks might be suited to reveal with great fidelity redox gradients in subduction zones.

  16. An explanation for the 18O excess in Noelaerhabdaceae coccolith calcite (United States)

    Hermoso, M.; Minoletti, F.; Aloisi, G.; Bonifacie, M.; McClelland, H. L. O.; Labourdette, N.; Renforth, P.; Chaduteau, C.; Rickaby, R. E. M.


    Coccoliths have dominated the sedimentary archive in the pelagic environment since the Jurassic. The biominerals produced by the coccolithophores are ideally placed to infer sea surface temperatures from their oxygen isotopic composition, as calcification in this photosynthetic algal group only occurs in the sunlit surface waters. In the present study, we dissect the isotopic mechanisms contributing to the "vital effect", which overprints the oceanic temperatures recorded in coccolith calcite. Applying the passive diffusion model of carbon acquisition by the marine phytoplankton widely used in biogeochemical and palaeoceanographic studies, our results suggest that the oxygen isotope offsets from inorganic calcite in fast dividing species Emiliania huxleyi and Gephyrocapsa oceanica originates from the legacy of assimilated 18O-rich CO2 that induces transient isotopic disequilibrium to the internal dissolved inorganic carbon (DIC) pool. The extent to which this intracellular isotopic disequilibrium is recorded in coccolith calcite (1.5 to +3‰ over a 10 to 25 °C temperature range) is set by the degree of isotopic re-equilibration between CO2 and water molecules before intracellular mineralisation. We show that the extent of re-equilibration is, in turn, set by temperature through both physiological (dynamics of the utilisation of the DIC pool) and thermodynamic (completeness of the re-equilibration of the relative 18O-rich CO2 influx) processes. At the highest temperature, less ambient aqueous CO2 is present for algal growth, and the consequence of carbon limitation is exacerbation of the oxygen isotope vital effect, obliterating the temperature signal. This culture dataset further demonstrates that the vital effect is variable for a given species/morphotype, and depends on the intricate relationship between the environment and the physiology of biomineralising algae.

  17. Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi (United States)

    Stoll, Heather M.; Rosenthal, Yair; Falkowski, Paul


    Continuous culture of the coccolithophorid Emiliania huxleyi reveals that coccolith Sr/Ca ratios depend on temperature and growth rate. At a constant temperature of 18°C, coccolith Sr/Ca ratios increased nearly 15% as growth rate increased from 0.1 to 1.5 divisions per day and calcification rate increased from 1.5 to 50 pg calcite per cell per day. When temperature increased from 7 to 26°C, Sr/Ca ratios increased by more than 25% (i.e., 1%/1°C), although the range in growth and calcification rates was the same as for experiments at constant temperature. The temperature dependence of Sr/Ca ratios in coccoliths is consistent with that observed in planktonic foraminifera and abiogenic calcites, suggesting that it is controlled by thermodynamic processes. However, the positive correlation of coccolith Sr/Ca with temperature contrasts with field studies in the equatorial Pacific, where Sr/Ca ratios are highest at the locus of maximum upwelling and productivity despite depressed temperatures. This paradox may reflect different calcification rate effects between E. huxleyi and the other species dominating assemblages in the equatorial Pacific sediments, which may be resolved by new techniques for separation of monospecific coccolith samples from sediments. Models of crystal growth indicate that kinetic effects on Sr partitioning in calcite due to surface enrichment could explain the Sr/Ca variations observed in constant temperature experiments but not the larger amplitude calcification rate effects observed in equatorial Pacific sediments. Despite the dual influence of temperature and growth rate on coccolith Sr/Ca, coccolith Sr/Ca correlates with "b," the slope of the dependence of carbon isotope fractionation in biomarkers (ɛ p) on CO 2(aq) at a range of growth rates and temperatures. Consequently, using coccolith Sr/Ca in combination with alkenone ɛ p may improve paleo-CO 2 determinations.

  18. The evolution of Carbon isotopes in calcite in the presence of cyanobacteria (United States)

    Grimm, Christian; Mavromatis, Vasileios; Pokrovsky, Oleg S.; Oelkers, Eric H.


    Stable isotopic compositions in carbonates are widely used as indicators of environmental conditions prevailing during mineral formation. This reconstruction is substantially based on the assumption that there is no change in the mineral composition over geological time. However, recent experimental studies have shown that carbon and magnesium isotopes in hydrous Mg-carbonates undergo continuous re-equilibration with the ambient solution even after mineral precipitation stopped ([1] and [2], respectively). To verify whether this holds true for anhydrous Ca-bearing carbonates which readily form at earth's surface environments, a series of batch system calcite precipitation experiments were performed in the presence of actively growing cyanobacteria Synechococcus sp. The bacteria were grown at ambient temperature in a BG11 culture medium (SIGMA C3061) and continuous stirring, air-bubbling and illumination. Calcite precipitation was initiated by the addition of 8.5mM CaCl2 and 0-50 mM NaHCO3 or NaHCO3-Na2CO3 mixtures. The presence of cyanobacteria is on one hand promoting CaCO3 formation due to increasing pH resulting from photosynthesis. On the other hand, actively growing cyanobacteria drastically change carbon isotope signature of the aqueous fluid phase by preferably incorporating the lighter 12C isotope into biomass [1]. This study explores the effect of continuously changing carbon isotope compositions in dissolved inorganic carbon (DIC) on precipitated calcite which is in chemical equilibrium with the ambient fluid phase. [1] Mavromatis et al. (2015). The continuous re-equilibration of carbon isotope compositions of hydrous Mg-carbonates in the presence of cyanobacteria. Chem. Geol. 404, 41-51 [2] Mavromatis et al. (2012). Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria. Geochim. Cosmochim. Acta 76, 161-174

  19. Microstructure and thermal change of texture of calcite crystals in ostrich eggshell Struthio camelus

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, A. [Instituto de Ciencias Nucleares, UNAM. Circuito Exterior, Ciudad Universitaria, Coyoacan C.P. 04510 Mexico D.F. (Mexico) and Instituto de Fisica, UNAM. Apartado Postal 20-364, 01000 Mexico D.F. (Mexico)]. E-mail:; Rodriguez-Hernandez, A.G. [Instituto de Fisica, UNAM. Apartado Postal 20-364, 01000 Mexico D.F. (Mexico); Lozano, L.F. [Instituto de Fisica, UNAM. Apartado Postal 20-364, 01000 Mexico D.F. (Mexico); Pena-Rico, M.A. [Instituto de Fisica, UNAM. Apartado Postal 20-364, 01000 Mexico D.F. (Mexico); Velazquez, R. [Instituto de Fisica, UNAM. Apartado Postal 20-364, 01000 Mexico D.F. (Mexico); Basiuk, V.A. [Instituto de Ciencias Nucleares, UNAM. Circuito Exterior, Ciudad Universitaria, Coyoacan C.P. 04510 Mexico D.F. (Mexico); Bucio, L. [Instituto de Fisica, UNAM. Apartado Postal 20-364, 01000 Mexico D.F. (Mexico)


    Eggshell from ostrich Struthio camelus, pristine and thermally treated in the range from room temperature to 550 deg. C, was investigated with low vacuum scanning electron microscopy (LVSEM), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and X-ray powder diffractometry (XRD). Different zones of the eggshell were analysed, including the protein-related, non-crystalline, inner organic membrane. After the high-temperature treatment (>500 deg. C), only crystallised calcite phase was found showing two main textures depending on the shell zone and the treatment temperature. In the crystal layer of the untreated samples, nanosized calcite crystals are organized with their c crystallographic axes highly aligned normal to eggshell surface (a very sharp gaussian angular distribution, {sigma}=0.14, was obtained by using the Rietveld method to model the preferred orientation function in the X-ray powder diffraction pattern). Elemental analysis revealed more Mg{sup 2+} in the crystal layer than in cone layer of the eggshell. A high nitrogen content in the organic membrane is associated to a proteinaceous phase. The cone and palisade layers are composed of needle-shaped calcite crystals, which are more crystallized than in the crystal layer and in average with their c crystallographic axes oriented in all directions except for the one perpendicular to the eggshell surface. Due to the complex structure and the amorphous/crystal phase interactions, the heating at about 500 deg. C texturizes the crystals orienting them mainly along the c-axes normal to the inner eggshell surface.

  20. Portal vein and mesenteric vein gas: CT features; Aeroportie ety aeromesenterie: donnees TDM

    Energy Technology Data Exchange (ETDEWEB)

    Schmutz, G.; Fournier, L.; Le Pennec, V.; Provost, N.; Hue, S.; Phi, I.N. [Centre Hospitalier Universitaire, 14 - Caen (France)


    Portal vein and mesenteric vein gas are unusual conditions with a complex and nuclear pathogenesis. Mesenteric ischemia frequently causes such pathological conditions but a variety of other causes are known: inflammatory bowel disease, bowel distension, traumatic and iatrogenic injury, intra-abdominal sepsis, and idiopathic conditions. This pathologic entity is favored by intestinal wall alterations, bowel distension and sepsis. The prognosis is frequently fatal, especially when associated with extended bowel necrosis although in the majority of the cases, outcome is favorable without surgery. (author)

  1. The influence of solution composition and grain boundaries on the replacement of calcite by dolomite (United States)

    Moraila Martinez, Teresita de Jesus; Putnis, Christine V.; Putnis, Andrew


    Dolomite formation is a mineral replacement reaction that affects extensive rock volumes and comprises a large fraction of oil and gas reservoirs [1,2]. The most accepted hypothesis is the 'dolomitization' of limestone by Mg-rich fluids [3]. The objective of this research is to study the replacement mechanism of calcite by dolomite, the role of grain boundaries, highlighted by Etschmann et al. (2014), and the possible influence of solutions in dolomite formation under the presence of ions that are normally in crustal aqueous fluids. To accomplish this purpose, we performed hydrothermal experiments using Carrara marble cubes of ~1.5 mm size and 7-9 mg weight as starting material, reacted with 1M (Mg,Ca)Cl2 aqueous solutions, with Mg/Ca ratios of 3 and 5 at 200°C, for different reaction times. Additional experiments were performed adding 1mM of Na2SO4, NaCl or NaF to the previous solutions. After the reaction, the product phases were identified using Raman spectroscopy, X-Ray powder diffraction (XRD), electron microprobe analysis (EMPA), and the textural evolution was studied by scanning electron microscopy (SEM). Samples reacted with aqueous solutions resulted in the replacements of the calcite rock into magnesite and dolomite. The amount and type of reaction strongly depends on the Mg/Ca ratio. Samples reacted with a Mg/Ca ratio of 5 resulted in an almost complete replacement reaction and more favorable for magnesite formation than for dolomite. When the Mg/Ca ratio was 3 dolomite formed but the replacement was located in the core of the sample. We show that grain boundaries are very important for the infiltration of solution and the progress of a replacement reaction, acting as fluid pathways. Solution composition controls the nature of the replacement product. Acknowledgment: This work is funded within a Marie Curie EU Initial Training Network- CO2-React. 1. Etschmann B., Brugger J., Pearce M.A., Ta C., Brautigan D., Jung M., Pring A. (2014). Grain boundaries as

  2. Rapid high temperature field test method for evaluation of geothermal calcite scale inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Asperger, R.G.


    A test method is described which allows the rapid field testing of calcite scale inhibitors in high- temperature geothermal brines. Five commercial formulations, chosen on the basis of laboratory screening tests, were tested in brines with low total dissolved solids at ca 500 F. Four were found to be effective; of these, 2 were found to be capable of removing recently deposited scale. One chemical was tested in the full-flow brine line for 6 wks. It was shown to stop a severe surface scaling problem at the well's control valve, thus proving the viability of the rapid test method. (12 refs.)

  3. Possible factors that control calcite dissolution in the western tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.

    CURRENT SCIENCE, VOL. 95, NO. 1, 10 JULY 2008 22 Possible factors that control calcite dissolution in the western tropical Indian Ocean The oceans act as a major controlling de- vice of atmospheric CO 2 through the chemistry of the oceans... and preservation of calcium carbonate in deep-sea sedi- ments 1 . Carbon dioxide dissolved in sea water is present as CO 2 gas, H 2 CO 3 , HCO – 3 and CO = 3 . All these species together con- stitute the Dissolved Inorganic Carbon (DIC) 2 which controls...

  4. Inversion of calcite twin data for stress (2) : EBSD as a tool for data measurements (United States)

    Parlangeau, Camille; Lacombe, Olivier; Brisset, Francois; Kohler, Eric; Daniel, Jean-Marc; Schueller, Sylvie


    Inversion of calcite twin data are known to be a powerful tool to reconstruct the past state(s) of stress in carbonate rocks of the crust, especially in fold-and-thrust belts and sedimentary basins. Twin data measurements have been for long carried out optically using a Universal-Stage. This data collection is time-consuming and suffers from limitations and bias related to measurements of twin planes oblique at low angle or parallel to the thin section, or the unambiguous evaluation of the twinned/untwinned character of collected twin data. EBSD (electron backscatter diffraction) is a well-known technique applied to characterize textures and microstructures of metals or deformed fine-grained rocks. The challenge is to define a strategy for measuring calcite-twin orientations that should be fast, without any loss of information, and which must reconcile (1) the need for a large amount of calcite twin data (3 mutually perpendicular thin sections and at least 30 crystals per thin section), (2) the spacing between EBSD spots, that should take into account (3) the small width of twin lamellae within grains deformed at low pressure and temperature and (4) the large size (usually several hundreds of microns) of twinned calcite grains used for stress analysis. To date, these multiple requirements preclude any (classical) automatic twin data acquisition but instead imply a preliminary definition of the areas of the thin section to be scanned by the EBSD spots, including grain boundaries, because the stress inversion technique requires to know for each grain the orientations of the C axis and of the 3 potential e twin planes. In order to reconcile a perfectly polished surface as required by EBSD and the recognition of grain boundaries, we adopted the double etching technique (Herwegh, 2000) to first reveal grain and twin boundaries. Then, with a SEM and a very fine coating sample, the section is scanned using secondary electrons bin; each spot of interest is visually defined

  5. Sm-Nd isotope dating of hydrothermal calcites from the Xikuangshan antimony deposit, Central Hunan

    Institute of Scientific and Technical Information of China (English)


    The research on Samarium-Neodymium isotope systematics of hydrothermal calcites from the Xikuangshan antimony deposit, Central Hunan, places precise timing constraints on the Sb mineralization in this area. It is revealed that the Xikuangshan deposit formed during the late Jurassic-early Cretaceous Period, the early- and late- stage mineralization took place at (155.5 ± 1.1) Ma and (124.1 ± 3.7) Ma, respectively. The accurate age determination of mineralization is very crucial for revealing the super-enrichment mechanism of the element Sb at the Xikuangshan mine, and lays some foundations for the further understandings of its ore genesis and mineralization mechanism.

  6. Adsorption of pesticides onto quartz, calcite, kaolinite, and α-alumina

    DEFF Research Database (Denmark)

    Clausen, Liselotte; Fabricius, Ida Lykke; Madsen, L.


    adsorption characteristics of selected pesticides. Investigated mineral phases included quartz, calcite, kaolinite, and alpha -alumina. Selected pesticides comprised atrazine (6-chloro-N-2-ethyl-N-4-isopropyl-1,3,5-triazine-2,4-diamine isoproturon [3-(4-isopropyl-phenyl)-1,1-dimethylurea)], mecoprop [(RS)-2...... due to formation of Ca-pesticide-surface complexes. Adsorption of the uncharged pesticides (atrazine and isoproturon) was detected only on kaolinite. The lack of adsorption on alpha -alumina indicates that the uncharged pesticides have a greater affinity for the silanol surface sites (= SiOH) than...

  7. Structure and dynamics of microbe-exuded polymers and their interactions with calcite surfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Cygan, Randall Timothy; Mitchell, Ralph (Harvard University, Cambridge, MA); Perry, Thomas D. (Harvard University, Cambridge, MA)


    Cation binding by polysaccharides is observed in many environments and is important for predictive environmental modeling, and numerous industrial and food technology applications. The complexities of these organo-cation interactions are well suited to predictive molecular modeling studies for investigating the roles of conformation and configuration of polysaccharides on cation binding. In this study, alginic acid was chosen as a model polymer and representative disaccharide and polysaccharide subunits were modeled. The ability of disaccharide subunits to bind calcium and to associate with the surface of calcite was investigated. The findings were extended to modeling polymer interactions with calcium ions.

  8. Endovascular Laser Therapy for Varicose Veins (United States)


    Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular laser therapy (ELT) for the treatment of primary symptomatic varicose veins (VV). Background The Ontario Health Technology Advisory Committee (OHTAC) met on November 27, 2009 to review the safety, effectiveness, durability and cost-effectiveness of ELT for the treatment of primary VV based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition VV are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad or worse as other chronic diseases such as

  9. Reproducibility of dorsal hand vein responses to phenylephrine and prostaglandin F2 alpha using the dorsal hand vein compliance method. (United States)

    Schindler, C; Grossmann, M; Dobrev, D; Francke, K; Ravens, U; Kirch, W


    Assessment of drug-induced venodilation by the dorsal hand vein compliance method requires stable constriction of the vein. This study was designed to investigate intra- and intersubject reproducibility of the venous preconstriction technique in response to phenylephrine and prostaglandin F2 alpha and to determine the influence of basal vein size. Twelve healthy male nonsmokers participated in a prospective cross-over study. Inter- and intrasubject variability was tested in response to phenylephrine and PGF2 alpha on different study days in the same hand vein. The dose of the respective constrictor causing approximately 80% constriction of the vein (ED80) was determined and infused for another 100 minutes. Actual vein size was measured every 5 minutes. Coefficient of variation and regression analyses were performed to analyze influence of vessel size on ED80 of the respective constrictor. Adjusted constriction levels were stable and well reproducible in all subjects. The intersubject coefficient of variation of ED80 ranged from 0.9% to 6.7% for phenylephrine and from 0.9% to 6.9% for PGF2 alpha. Whereas responses to phenylephrine were independent of basal vein diameter, there was a positive correlation between ED80 of PGF2 alpha and basal vein size. Thus, the hand vein compliance method is a suitable method to study dilatory responses in phenylephrine- or PGF2 alpha-constricted veins with considerable interindividual but small intraindividual variability. However, in such studies, phenylephrine appears to be a more reliable tool than PGF2 alpha.

  10. Surface Kinetic Model for the Fractionation of Trace Elements and Isotopes in Calcite Precipitated from Aqueous Solution (United States)

    Depaolo, D. J.; Ryerson, F. J.; Watkins, J. M.; Bourg, I. C.; Yang, W.; Nielsen, L. C.; Druhan, J. L.


    The isotopic and trace element concentrations in calcite and other carbonate minerals form the basis for several paleoceanographic and paleoenvironmental indicators. The chemical and isotopic composition of natural calcites is determined by a combination of equilibrium partitioning and kinetic fractionations. Currently there is no general model that describes when equilibrium applies and how kinetic effects depend on the circumstances and rates of mineral growth. A useful approach is to separate the growth of calcite from aqueous solutions into forward (f) and backward (b) reactions, and to consider the mechanisms and fractionations that may be associated with each. We are evaluating a model where the net precipitation rate of calcite (Rp) is expressed as the difference between a forward rate (Rf) and a backward (dissolution) rate (Rb). Dissolution is approached only as Rp/Rb->0. Much natural calcite, including biogenic, forms under conditions where Rp ≫ Rb, hence the isotopic and trace element partitioning is strongly influenced by the kinetics of the forward reaction. Assuming that there are kinetic fractionations associated with the forward and backward reactions, a simple model can be developed for the dependence of calcite composition on precipitation rate. This model can explain most available experimental data on Ca and O isotopes, as well as Sr/Ca and Mn/Ca in calcite, and can be used to infer the behavior of other trace and minor elements. The critical parameter in applying the model is the value of Rb which to first order can be estimated from mineral dissolution rates, but apparently is not a constant, but instead varies with solution chemistry, especially at saturation conditions close to equilibrium. The surface kinetic model requires three parameters that are measureable experimentally and potentially also predictable from molecular dynamics simulation approaches. In this way it differs from the surface entrapment model of Watson (2004) which

  11. Physical and stable-isotope evidence for formation of secondary calcite and silica in the unsaturated zone, Yucca Mountain, Nevada (United States)

    Whelan, J.F.; Paces, J.B.; Peterman, Z.E.


    Calcite and silica form coatings on fracture footwalls and cavity floors in the welded tuffs at Yucca Mountain, the potential site of a high-level radioactive waste repository. These secondary mineral deposits are heterogeneously distributed in the unsaturated zone (UZ) with fewer than 10% of possible depositional sites mineralized. The paragenetic sequence, compiled from deposits throughout the UZ, consists of an early-stage assemblage of calcite??fluorite??zeolites that is frequently capped by chalcedony??quartz. Intermediate- and late-stage deposits consist largely of calcite, commonly with opal on buried growth layers or outermost crystal faces of the calcite. Coatings on steep-dipping fractures usually are thin (??? 3 mm) with low-relief outer surfaces whereas shallow-dipping fractures and lithophysal cavities typically contain thicker, more coarsely crystalline deposits characterized by unusual thin, tabular calcite blades up to several cms in length. These blades may be capped with knobby or corniced overgrowths of late-stage calcite intergrown with opal. The observed textures in the fracture and cavity deposits are consistent with deposition from films of water fingering down fracture footwalls or drawn up faces of growing crystals by surface tension and evaporated at the crystal tips. Fluid inclusion studies have shown that most early-stage and some intermediate-stage calcite formed at temperatures of 35 to 85??C. Calcite deposition during the past several million years appears to have been at temperatures < 30??C. The elevated temperatures indicated by the fluid inclusions are consistent with temperatures estimated from calcite ??18O values. Although others have interpreted the elevated temperatures as evidence of hydrothermal activity and flooding of the tuffs of the potential repository, the authors conclude that the temperatures and fluid-inclusion assemblages are consistent with deposition in a UZ environment that experienced prolonged heat input from

  12. Internal Jugular Vein Entrapment in a Multiple Sclerosis Patient

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    Marian Simka


    Full Text Available We describe a multiple sclerosis patient presenting with compression of the internal jugular vein caused by aberrant omohyoid muscle. Previously this patient underwent balloon angioplasty of the same internal jugular vein. Ten months after this endovascular procedure, Doppler sonography revealed totally collapsed middle part of the treated vein with no outflow detected. Still, the vein widened and the flow was restored when the patient’s mouth opened. Thus, the abnormality was likely to be caused by muscular compression. Surgical exploration confirmed that an atypical omohyoid muscle was squeezing the vein. Consequently, pathological muscle was transected. Sonographic control three weeks after surgical procedure revealed a decompressed vein with fully restored venous outflow. Although such a muscular compression can be successfully managed surgically, future research has to establish its clinical relevance.

  13. Dissolution and Sorption Processes on the Surface of Calcite in the Presence of High Co2+ Concentration

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    Jorge González-López


    Full Text Available The interaction of the calcite surface with Co2+-rich aqueous solutions ([Co2+aq]initial = 1000 ppm, i.e., ca. 17 mM was investigated by means of macroscopic experiments and surface spectroscopic techniques. In the case of the macroscopic experiments, calcite powder and monocrystals were immersed into solutions for different time periods (from 1 min to one month. The Ca concentrations in the filtrates was measured by means of atomic absorption spectrometry (AAS while the interacted solids were studied using a combination of X-ray photoelectron spectroscopy (XPS and 12C-rutherford backscattering spectrometry (12C-RBS. The macroscopic data showed a characteristic surface dissolution process, in parallel to the surface sorption processes. Adsorption and co-precipitation were seen for almost the entire immersion period for both calcite powder and monocrystals. The surface study by XPS (analyzed at a depth of approximately 12 nm suggested that adsorption takes place in the first hour of the interaction, followed by incorporation of Co2+ into calcite surface layers, leading to the formation of a Co2+-bearing surface (coprecipitate, which occurs over a period of hours and days. The 12C-RBS measurements on calcite { 10 1 ¯ 4 } indicated that the thickness of this surface co-precipitate was 270 nm after one day and then stabilized at 320 nm after more than a week.

  14. Iodate in calcite and vaterite: Insights from synchrotron X-ray absorption spectroscopy and first-principles calculations (United States)

    Podder, J.; Lin, J.; Sun, W.; Botis, S. M.; Tse, J.; Chen, N.; Hu, Y.; Li, D.; Seaman, J.; Pan, Y.


    Calcium carbonates such as calcite are the dominant hosts of inorganic iodine in nature and are potentially important for the retention and removal of radioactive iodine isotopes (129I and 131I) in contaminated water. However, little is known about the structural environment of iodine in carbonates. In this study, iodate (IO3-) doped calcite and vaterite have been synthesized using the gel-diffusion method at three NaIO3 concentrations (0.002; 0.004; 0.008 M) and a pH value of 9.0, under ambient temperature and pressure. Inductively coupled plasma mass spectrometry (ICP-MS) analyses show that iodine is preferentially incorporated into calcite over vaterite. Synchrotron iodine K-edge X-ray absorption near-edge structure (XANES) spectra confirm that IO3- is the dominant iodine species in synthetic calcite and vaterite. Analyses of iodine K-edge extended X-ray absorption fine structure (EXAFS) data, complemented by periodic first-principles calculations at the density functional theory (DFT) levels, demonstrate that the I5+ ion of the IO3- group in calcite and vaterite is bonded by three and two additional O atoms (i.e., coordination numbers = 6 and 5), respectively, and is incorporated via the charged coupled substitution I5+ + Na+ ↔ C4+ + Ca2+, with the Na+ cation at a nearest Ca2+ site being the most energetically favorable configuration.

  15. Calcite Supersaturation and Precipitation Kinetics in the Lower Colorado River, Ail-American Canal and East Highline Canal (United States)

    Suarez, D. L.


    In situ pH determinations and analysis of major ions in solution indicated that the lower Colorado River is supersaturated with respect to calcite throughout the entire daily cycle, in both winter and summer. Although the ion activity product was 4 to 6 times greater than the calcite solubility product, there was no detectable precipitation. Chemical analyses of water samples taken along 350 km of the river and canals from Parker Dam to the Salton Sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows. Laboratory kinetic studies indicated that calcite crystal growth rates with Colorado River water are about 30% of the rate for pure Ca-HCO3 waters and about 70% of that for synthetic Colorado River water. Calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite. Critical supersaturation levels necessary for heterogeneous nucleation do not occur; a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime H2CO3 levels.

  16. Two-dimensional X-ray diffraction as a tool for the rapid, nondestructive detection of low calcite quantities in aragonitic corals (United States)

    Smodej, Jörg; Reuning, Lars; Wollenberg, Uwe; Zinke, Jens; Pfeiffer, Miriam; Kukla, Peter A.


    Paleoclimate reconstructions based on reef corals require precise detection of diagenetic alteration. Secondary calcite can significantly affect paleotemperature reconstructions at very low amounts of ˜1%. X-ray powder diffraction is routinely used to detect diagenetic calcite in aragonitic corals. This procedure has its limitations as single powder samples might not represent the entire coral heterogeneity. A conventional and a 2-D X-ray diffractometer were calibrated with gravimetric powder standards of high and low magnesium calcite (0.3% to 25% calcite). Calcite contents convenient 1-D-XRD methods is the nondestructive and rapid detection of calcite with relatively high spatial resolution directly on coral slabs. The calcite detection performance of the 2-D-XRD setup was tested on thin sections from fossil Porites sp. samples that, based on powder XRD measurements, showed sampling. In this way, areas affected by diagenetic calcite can be avoided and alternative sampling tracks can be defined. Alternatively, individual sampling positions that show dubious proxy results can later be checked for the presence of calcite. The presented calibration and quantification method can be transferred to any 2-D X-ray diffractometer.

  17. Splenic vein leiomyosarcoma: case report and review of the literature. (United States)

    Patrono, Damiano; Molinaro, Luca; Mazza, Elena; Romagnoli, Renato; Salizzoni, Mauro


    Primary venous leiomyosarcoma (LMS) is a rare disease, most commonly affecting the retroperitoneal veins and in particular the inferior vena cava. Five-year survival rate ranges between 33% and 68%. Complete surgical resection represents the only potentially curative treatment, occasionally achieving long-term survival. LMS of the splenic vein is extremely rare, with only three cases reported in the literature. We report a case of primary venous LMS arising from the splenic vein and we briefly review the relevant literature.

  18. Pediatric aneurysms and vein of Galen malformations (United States)

    Rao, V. R. K.; Mathuriya, S. N.


    Pediatric aneurysms are different from adult aneurysms – they are more rare, are giant and in the posterior circulation more frequently than in adults and may be associated with congenital disorders. Infectious and traumatic aneursyms are also seen more frequently. Vein of Galen malformations are even rarer entities. They may be of choroidal or mural type. Based on the degree of AV shunting they may present with failure to thrive, with hydrocephalus or in severe cases with heart failure. The only possible treatment is by endovascular techniques – both transarterial and transvenous routes are employed. Rarely transtorcular approach is needed. These cases should be managed by an experienced neurointerventionist. PMID:22069420

  19. Electro-oculogram of Retinal Vein Occlusion

    Institute of Scientific and Technical Information of China (English)


    Twenty five cases, including 26 eyes with retinal vein occlusion (RVO) were examined by means of the electro-oculogram. The results showed that 23 of the 26 eyes suffering from RVO exhibited abnormalities of the electro-oculogram (EOG). The potential difference and Arden ratio in the RVO eyes were lower than those in the normal eyes (P<0.01). The more the visual acuity of ill eyes was decreased, the higher the abnormal rate of EOG in ill eyes was. 14 eyes had the visual acuity less than 0.1, whose EOGs ...

  20. Central Retinal Vein Occlusion Revealing Coelic Disease

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    Full Text Available Introduction: Thrombosis has been widely reported in coeliac disease (CD but central retinal vein occlusion (CRVO is rarely described. Case presentation: A 27-year-old woman presented with acute visual loss and was diagnosed with CRVO. Her protein S and protein C levels were low and CD was diagnosed on the basis of endoscopic, immunological and histological results. A gluten-free diet resulted in favourable evolution. Conclusion: CD should be considered in young patients with thrombosis, especially if in an unusual location. Treatment is based on a gluten-free diet.